Field Manual No. 5-134 *FM 5-134Headquarters, Department of the Army

Washington, DC, 18 April 1985

PILE

C O N S T R U C T I O N

*This field manual supersedes TM 5-258, 18 June 1963.i

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Preface

P-1. Purpose and scope. This manual is organized to be used as a fieldreference. Chapter 1 through 4 discuss piles, equipment, and installation.Information concerning design (less that of sheet piling structures) isprovided in chapters 5 through 7 for use when tactical and logisticalsituations dictate original design. These chapters are of primary interest toengineer staff officers planning pile construction when the standardinstallations, facilities, equipment and supplies of the Army FacilitiesComponent System (AFCS) are not used. The appendix presents infor-mation on piling materials not currently available through military supply.The glossary contains terms frequently used in pile design and construction,acronyms, and abbreviations used in this manual.

P-2. User information. The proponent agency of this publication is theUS Army Engineer School. Submit changes for improving this publicationon DA Form 2028 (Recommended Changes to Publications and BlankForms) and forward to US Army Engineer School, ATTN: ATZA-TD-P, FortBelvoir, Virginia 22080-5291.

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C H A P T E R 1

B A S I C C O N S I D E R A T I O N S

Section I. DEFINITIONS ANDCLASSIFICATIONS

1-1. Definitions.

a. Piles. A pile is a long, columnar elementmade of timber, steel, concrete, or acombination of these materials (discussed inchapter 2). Piles transmit foundation loads todeeper strata that sustain the loads safelyand prevent settling of the supportedstructure. Piles derive their support from acombination of skin friction along theembedded lengths and end bearing at the tipsor bottoms (figure l-l).

b. Piers. A pier is a pile used to support ahorizontal supporting span such as a bridgeor archway.

c. Sheet piles. Sheet piles are generallyprefabricated or precast members drivenvertically into the ground to form a con-tinuous vertical wall. Sheet piles protectbearing piles against scour and the danger ofundermining a pier foundation (figure 1-2).They form retaining walls (bulkheads) forwaterfront structures (figure 1-3).

d. Friction/end-bearing piles. A pileembedded in soil with no pronounced bearingstratum at the tip is a friction pile (figure 1-4).A pile driven through relatively weak orcompressible soils into rock or an underlyingstronger material is an end-bearing pile(figure 1-5).

e. Batter piles. Piles driven at an angle arebatter piles. They are used to resist heavylateral or inclined loads or where thefoundation material immediately beneath thestructure offers little or no resistance to thelateral movement of vertical piles. Battersare driven into a compressible soil to spreadvertical loads over a larger area, therebyreducing settlement. They may be used alone(battered in opposite directions) or incombination with vertical piles (figure 1-6).Batter piles can be driven at slopes of 4degrees to 12 degrees with ordinary drivingequipment.

f. Compaction piles. Compaction piles aredriven to increase the density of loose,cohesionless soils (figure 1-7) and to reducesettlement, since shallow foundations on veryloose deposits of sand or gravel may settleexcessively. Piles with a heavy taper are

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most effective and economical. These pilesderive their support primarily from friction.

g. Anchor piles. Anchor piles are driven toresist tension loads. In hydraulic structures,there may be a hydrostatic uplift load that isgreater than the downward load on thestructure. Anchor piles may be used to anchorbulkheads, retaining walls, and guy wires(figure 1-3).

h. Fender piles. Fender piles are drivento protect piers, docks, and bridges fromthe wear and shock of approaching shipsand floating objects such as ice and debris(figure 1-3).

i. Dolphins. A dolphin is a group of pilesdriven in clusters to aid in maneuveringships in docking operations. These dolphinsserve the same protective functions as fenderpiles (figure 1-3).

1-2. Pile functions.

Several uses of piles are illustrated in figures1-1 through 1-7. A pile or series of piles areused to constructor reinforce construction to

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To eliminate objectionable settlement.

To resist lateral loads.

To serve as fenders to absorb wear andshock.

To improve load-bearing capacity of soiland reduce potential settlement.

To transfer loads from overwaterstructures below the depth of scour.

To anchor structures subjected tohydrostatic uplift, soil expansion, oroverturning.

Section II. PILE SELECTION1-3. Factors.

Many factors influence the choice of piletypes used on a given project. Considerationmust be given to the following factors (andothers, if applicable).

establish a stable foundation. Piles are usedas follows.

To transfer the structural load throughmaterial or strata of poor bearing capacityto one of adequate bearing capacity.

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Type of construction.

Availability of pile types and sizes.

Soil and groundwater conditions at thesite.

Anticipated pile loads.

Driving chacteristics of available piles.

Capabilities of crew and equipment avail-able for handling and driving piles.

Time available for construction.

Design life of structure.

Exposure conditions.

Accessibility of site and transportationfacilities.

Comparative costs.

14. Construction consideration.

a. Material selection. Piles are made fromtimber, steel, or concrete. Composite piles,formed of one material in the lower sectionand another in the upper, are not commonlyused in military construction because of thedifficulty in forming a suitable joint and thegreater complexity of installation.

b. Deliberate construction. Criticalstructures such as wharves, piers, and bridgeson main routes of communication must bewell constructed. Deliberate structureswarrant high safety factors. These structuresrequire thorough soil investigation and siteexamination to obtain the information forproper planning and design. This informationis essential for safety, economy, andpracticality.

c. Hasty construction. In militaryconstruction, many pile structures are builthastily after limited reconnaissance. Hasty

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pile structures are designed with the lowestfactors of safety consistent with theirimportance. In hasty construction readilyavailable materials will be used to constructpile foundations capable of supporting thestructure at maximum load for immediateneeds. They can be strengthened or rebuiltlater.

1-5. Types and sizes.

Piles are classified by use, installation,material, and type of displacement. Clas-sification of piles based on installationtechnique is given in table 1-1.

a. Large displacement. Large displacementpiles include all solid piles such as timber andprecast concrete piles. These piles may beformed at the site or preformed. Steel pilesand hollow concrete piles, driven closed-ended, also fall within this group.

b. Small displacement. Small displacementpiles include steel H-piles, steel pipe piles (ifthe ground enters freely during driving),screw or anchor piles, and preformed pilesdriven in prebored holes.

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c. Nondisplacement. Nondisplacementpiles are formed by boring or other methodsof excavation. The borehole may be linedwith a casing that is either left in place orextracted as the hole is filled with concrete.

1-6. Soil and groundwater.

Soil and groundwater conditions determiuethe design and construction of pile foun-dations. Foundations are successful only ifthe soil strata, to which the structural loadsare transmitted, can support the loads withoutfailure or excessive settlement. Except forend-bearing piles founded on rock, pilesdepend upon the surrounding soil or thatbeneath the pile tips for support. Groundwaterconditions often dictate the type of piles thatmust be used and influence the load-carryingcapacity of piles. Adequate soil exploration,testing, and analysis are prerequisites to thesuccessful design and construction of allexcept crude, hasty pile structures. Therelation of soil conditions to pile driving andthe design of pile foundations are discussedin chapters 5 and 6.

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1-7. Comparative costs. piling materials on the basis of cost per linearfoot is misleading since the costs of shipping

Comparative costs of piling materials are and handling, the job conditions affectingcomputed on the dollar cost per ton of bearing driving techniques, and the relative load-capacity for the entire foundation. Comparing bearing capacities all affect the overall cost.

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C H A P T E R 2

MATERIALS

Section I. SELECTION OF MATERIALS

2-1. Considerations.

The varied factors to be considered inselecting piles is covered in chapter 1, sectionII Chapter 2 discusses selection of pilesbased on the type of construction and theavailability and physical properties of thematerials.

a. Hasty construction. In hasty con-struction, full use is made of any readilyavailable materials for pile foundationscapable of supporting the superstructure andmaximum load during a short term. Thetactical situation, available time, andeconomy of construction effort dictateconstruction.

b. Deliberate construction. In a theater ofoperations, timber piles are normally avail-able in lengths of 30 to 70 feet. They are alsorelatively easy to transport and manipulate.Steel piling is next in importance, especiallywhere deliberate construction is planned toaccommodate heavy loads or where thefoundation is expected to be used for a longtime. Small displacement steel H-piles are

particularly suited to penetrating deep layersof course gravel, boulders, or soft rock such ascoral. Such piles also reduce heave of adjacentstructures.

2-2. Army Facilities ComponentsSystem (AFCS) materials.

Complete bills of materials for facilities andinstallations of the AFCS are in TM 5-303.These detailed listings, identified by facilitynumber and description, provide stocknumber, nomenclature, unit, and quantityrequired. For additional information con-cerning AFCS installations involving pilefoundations, consult TM 5-301 and TM 5-302.

Section II. TIMBER PILES

2-3. Classification.

The American Society for Testing andMaterials (ASTM) classifies timber pilesaccording to their intended use (table 2-l).Class A and class B piles are identical inquality, but differ in size. Class C piles (notlisted) normally are not treated with pre-servatives. Timber piles are further classifiedin terms of marine and nonmarine use.

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a. Marine use. (2) Type II. Type II piles, pressure treatedwith creosote, are suitable for use in marinewaters of severe borer hazard.

(1) Type I. Type I piles, pressure treatedwith waterborne preservatives and creo- (3) Type III. Type III piles, pressure treatedsote (dual treatment), are suitable for use with creosote, are suitable for use in marinein marine waters of extreme borer hazard. waters of moderate borer hazard.

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b. Nonmarine use.

(1) Type I. Type I piles are untreated.

(2) Type II. Type II piles are treated.

2-4. Characteristics.

A good timber pile has the followingcharacteristics.

Free of sharp bends, large or loose knots,shakes, splits, and decay.

A straight core between the butt and tipwithin the body of the pile.

Uniform taper from butt to tip.

2-5. Source.

Usually, timber piles are straight tree trunkscut off above ground swell, with branchesclosely trimmed and bark removed (figure2-l). Occasionally, sawed timber may be usedas bearing piles.

2-6. Strength.

The allowable load on timber piles is basedon pile size, allowable working stress, soilconditions, and available driving equipment.These factors are discussed in chapters 5through 7. The customary allowable load ontimber piles is between 10 and 30 tons. Higherloads generally require verification bypile load tests. For piles designed as columns,working stresses (compression parallel to thegrain) for various types of timber are listed intable 2-2.2-7. Durability.

A principal disadvantage of timber piles islack of durability under certain conditions.Piles are subject to fungi (decay), insects, andmarine borers. Design life depends on thespecies and condition of the wood, the amount

and type of preservative treatment, the degreeof exposure, and other factors. Chapter 8discusses maintenance and rehabilitation.

2-8. Availability.

Timber suitable for piling is abundant inmany parts of the world (see appendix).Timber piling may be obtained from localstocks or cut from standing timber. Thenative stock may be used untreated, or apreservative may be applied as discussed inchapter 8.

2-9. Maintenance.

Because of deterioration, considerabletreatment and maintenance is required on

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timber piles. Maintenance is discussed inchapter 8.

2-10. Other properties.

a. Length. Length maybe adjusted by simplecarpentry (sawing). Timber piles may be cutoff if they do not penetrate as far as esti-mated. Piles driven into water substrata canbe adjusted by sawing off the pile tops abovewater level. They can also be sawed under-water using a saw supported by a frameworkabove the water level. Short piles may beeasily spliced.

b. Flexibility. Timber piles are more flexibilethan steel or concrete piles which makesthem useful in fenders, dolphins, small piers,and similar structures. They will deflectconsiderably, offer lateral resistance, andspring back into position absorbing the shockof a docking ship or other impact.

c. Fire susceptibility. Timber piles ex-tending above the water line, as in trestles orwaterfront structures, are susceptible todamage or destruction by fire.

2-11. Shipping and handling.

Timber piles are easy to handle and shipbecause they are relatively light and strong.Because they float, they can be transportedby rafting particularly for waterfront struc-tures. They can be pulled, cleaned, and reusedfor supplementary construction such as false-work, trestles, and work platforms.

Section III. STEEL PILES

2-12. Classification.

Steel piles are usually rolled H-sections orpipe piles; although wide-flange (WF) beamsare sometimes used. In the H-pile, the flangesand web are of equal thickness. The standardWF shapes have a thinner web than flange.

The 14-inch H-pile section weighing 73 poundsper linear foot and the 12-inch H-pile sectionweighing 53 pounds per linear foot are usedmost frequently in military construction.

a. H-piles. Steel H-piles are widely usedwhen conditions call for hard driving, greatlengths, or high working loads per pile. Theypenetrate into the ground more readily thanother types, partly because they displacerelatively little material. They are par-ticularly suitable, therefore, when the bearingstratum is at great depth. Steel piles areadjustable in length by cutting, splicing, orwelding.

b. Pipe piles. Pipe piles are either welded orseamless steel pipes which may be drivenopen-ended or closed-ended.

c. Railroad-rail piles. Railroad rails can beformed into piles as shown in figure 2-2. Thisis useful when other sources of piles are notavailable.

d. Other. Structured steel such as I-beams,channels, and steel pipe are often availablefrom captured, salvaged, or local sources.With resourceful design and installation, theycan be used as piles when other, moreconventional piles are not available.

2-13.Characteristics

a. Resilience. A steel pile is not as resilientas a timber pile; nevertheless, it is strong andelastic. Large lateral loads may causeoverstressing and permanent deformation ofthe steel, although the pile probably will notbreak. A steel pile may be bent and evenkinked to some degree and still support alarge load.

b. Penetration.

(1) H-piles. A steel H-pile will drive easilyin clay soils. The static load generally will

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be greater than the driving resistance pile and be carried down with it. The coreindicates because the skin friction in- of soil trapped on each side of the web willcreases after rest. In stiffer clays, the pile cause the pile to act as a large displacementmay have the soil compacted between the pile.flanges in driving. The clay may grip the

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(2) Pipe piles. Pipe piles driven open-endpermit greater driving depths, as less soildisplacement occurs. Pipe piles can bereadily inspected after driving. If smallboulders are encountered during driving,they may be broken by a chopping bit orblasting. Pipe piles are often filled withconcrete after driving.

2-14. Source.

a. AFCS. Steel piles can be obtained fromAFCS as described in paragraph 2-2.

b. Local supply. In combat, piles or materialto construct them can be obtained fromcaptured enemy stock or from the localeconomy within a theater of operations. Fulluse should be made of such captured,salvaged, or local materials by substitutingthem for the standard steel bearing pilingindicated by AFCS. Old or new rail sectionsmay be available from military supplychannels, captured stocks, or unused rails incaptured territory. Figure 2-2 shows methodsof welding steel rails to form expedient piles.Such expedient piles are usually fabricated inlengths of 30 feet.

2-15. Strength.

The strength ofpermitting long

steel piles is high, thuslengths to be handled.

Lengths up to 100 feet are not uncommon,although piles greater than 60 feet requirecareful handling to avoid excessive bendingstresses. Pipe piles are somewhat stiffer thanrolled steel sections. The allowable load onsteel piles is based on the cross-sectionalarea, the allowable working stress, soilconditions, and available driving equipment.The maximum allowable stress is generallytaken as 0.35 to 0.50 times the yield strengthwith a value of 12,000 pounds per square inch(psi) used frequently. Allowable loads onsteel piles vary between 50 and 200 tons.

2-16. Durability.

Although deterioration is not a matter ofgreat concern in military structures, steelbearing piles are subject to corrosion anddeterioration. The effects of corrosion,preventive measures taken to protect steelpiles, and remedial measures to correctprevious damage are discussed in chapter 8.

2-17. Shipping and handling.

a. Transporting. Although quite heavy,steel piles are easy to handle and ship. Theycan be transported by rail, water, or truck.Precautions should be taken during shippingand handling to prevent kinking of flanges orpermanent deformation. Steel pipes must beproperly stored to prevent mechanicaldamages.

b. Lifting and stacking. H-piles can belifted from the transport with a special slipon clamp and a bridle sling from a crane.Clamps are attached at points from one fifthto one fourth of the length from each end toequalize the stress. To make lifting easier, asmall hole may be burned in a flange betweenthe upper third and quarter points. Then ashackle may be attached to lift the piles intothe leads. Piles should be stacked on timbersso that they are kept reasonably straight.

Section IV. PRECAST CONCRETEPILES

2-18. Classification.

Precast concrete piles are steel-reinforcedmembers (sometimes prestressed) of uniformcircular, square, or octagonal section, with orwithout a taper at the tip (figure 2-3). Precastpiles range up to 40 or 50 feet in lengthalthough longer lengths may be obtained ifthe piles are prestressed. Classification isbasically by shape and is covered inparagraph 2-20.

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2-19. Characteristics. difficulty requiring both the chiseling of theconcrete and the cutting of the reinforcing

Precast piles are strong, durable and may be rods.cast to the designed shape for the particularapplication. The process of precasting is not 2-20. Source.available in the theater of operations. Theyare difficult to handle unless prestressed, and Precast concrete piles are manufactured in athey displace considerable ground during casting yard, at the job site, or at a centraldriving. Length adjustment is a major location. The casting yard is arranged so the

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piles can be lifted from their forms andtransported to the pile driver with a minimumof handling (figure 2-4). The casting yardincludes storage space for aggregates andcement, mixing unit, forms, floor area for thecasting operations, and sufficient storagespace for the completed piles. The castingyard should have a well-drained surface thatis firm enough to prevent warping during the

period between placement and hardening.Cement and aggregates may be handled bywheelbarrows or buggies. Additional storagespace may be needed for the completed piles.

a. Forms. Forms for piles may be of wood(figure 2-5) or metal. They must be tight toprevent leakage, firmly braced, and designedfor assembly and disassembly so that they

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can be reused. Forms must be thoroughlycleaned and oiled with a nonstaining oilbefore use.

b. Reinforcement. For precast concrete pilessubjected to axial loadings, steel rein-forcement provides resistance to the stressescaused by handling and driving. Threemethods of handling concrete piles areillustrated in figure 2-6. Depending on themethod used, the size and number oflongitudinal reinforcement bars aredetermined from design charts in figure 2-7.These charts are based upon an allowablestress of 1,400 psi in the concrete and 20,000psi in the steel, without allowance for impact.Minimum reinforcement cages are assembledas shown in figure 2-4. Adequate spiralreinforcing at the pile head and tip isnecessary to reduce the tendency of the pile tosplit or span during driving.

c. Placement. When concrete is placed inthe forms by hand, it should be of plasticconsistency with a 3-inch to 4-inch slump.Use a concrete mix having a l-inch to 2-inchslump with concrete vibrators. Reinforcementshould be properly positioned and securedwhile the concrete is placed and vibrated.Details concerning the design of concretemixes are contained in TM 5-742.

d. Curing. Forms should not be removed forat least 24 hours after concrete is placed.Following the removal of the forms, the pilesmust be kept wet for at least seven days whenregular portland cement is used, and threedays when high-early strength cement isused. Curing methods are discussed in TM5-742. Pending and saturated straw, sand, orburlap give good results. The piles should notbe moved or driven until they have acquiredsufficient strength to prevent damage. Eachpile should be marked with a referencenumber and the date of casting.

2-21. Strength.

Precast concrete piles can be driven to highresistance without damage. They are as-signed greater allowable loads than timberpiles. As with other pile types, allowableloads are based on the pile size, soilconditions, and other factors. Customaryallowable loads range from 20 to 60 tons for a10-inch diameter precast concrete pile and 70to 200 tons for an 18-inch square precastconcrete pile.

2-22. Durability.

Under ordinary conditions, concrete piles arenot subject to deterioration. They can be usedabove the water table. Refer to chapter 8 foradditional information on durability.

2-23. Availability.

Precast piles are available only when thecasting facility is nearby. See paragraph 2-20.

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2-24. Shipping and handling.

a. Handling. Piles should be handled inaccordance with the procedure selected fordesign (figure 2-6). For placement, piles maybe lifted by cables and hooks looped aroundthe pile at the desired point. To prevent wearto the cable, use short lengths of wood orother cushioning material, Piles designed fortwo-point support (figure 2-6, 3) and lifted bycables require the following arrangement.

A sheave is required at point A so that thecable will be continuous from point B overthe sheave at A to point C. This cable is anequalizer cable since the tension in ABmust be the same as that of AC. Unless anequalizer is used, care must be taken inlifting the pile so that tension in the cablesis equal; otherwise, the entire load mayrest on one end.

When the pile is raised to a verticalposition, another line, CD, is attached.When drawn up, the sheave at A shiftstoward C.

An additional line is needed with thiscable arrangement to prevent the pile fromgetting out of control when it is raised to avertical position.

b. Shipping and storage. If piles are to bestacked for storage or shipment, the blocking

between the tiers must be in vertical lines sothat a pile in a lower tier will not be subject tobending by the weight of the piles above. Anexample of improper stacking is shown infigure 2-8. A forklift or specially equippedfront-end loader can be used to move pilesfrom the storage area to the work area.Whenever possible, locate the casting site asclose as possible to the job site. Trans-portation by barge is the best method, iffeasible.

Section V. CAST-IN-PLACE PILES

2-25. Classification.

Cast-in-place piles are either cased oruncased. Both are made at the site by forminga hole in the ground at the required locationand filling it with a properly designed con-crete mix.

a. Cased. The concrete of a cased pile is castinside a metal casing or pipe left in theground. The casing is driven to the requireddepth and cleaned before placement ofconcrete. If the casing is relatively thin, amandrel is used to drive the casing. Manydifferent kinds of shells and mandrels areavailable commercially, but not throughmilitary supply channels. Those of foreignmanufacture may be available in a theater ofoperation.

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b. Uncased. Uncased concrete piles referredto as drilled piers are frequently used. Variousaugers are used for drilling holes up to 72inches in diameter with depths up to 60 feet ormore. Auger holes are excavated by the dryprocess. The bottom of the pier maybe under-reamed at the base, if desired, to providegreater end-bearing area or resistance againstuplift forces. Drilling mud advancing throughsubmerged granular materials keeps the holeopen. The dry shaft is filled with concrete. Atremie pipe is used through the drilling mud.Steel reinforcement may be used in theconcrete.

2-26.Characteristics.

The characteristics of cast-in-place pilesdepend greatly on the quality of workmanshipand characteristics of the soils and supportenvironment. Materials for concrete con-struction are readily available in manymilitary situations, thus drilled piers havesome military application. They require largediameter augers. Installation requires betterthan average workmanship. Groundwater isinfluential in determining the difficulty ofinstallation. Even small inflow quantities ofwater may induce caving, thus requiring theuse of casing or drilling mud. Drilled pierscan provide a rapid and economical methodof pile installation under many conditions.

2-27. Strength and durability.

Cast-in-place piles are strong. Large loadscan be carried by cast-in-place piles dependingon the cross-sectional area of the pile. Likeprecast piles, cast-in-place piles are durable.If the pile is cased, even though the casingshould deteriorate, the concrete portion willremain intact.

2-28. Construction.

Construction of cast-in-place piles isdescribed in chapter 4.

Section VI. SHEET PILES

2-29.Classification.

Sheet piles vary in use and materials. Theymay be classified by their uses. They differfrom previously described piles in that theyare not bearing piles, but are retaining piles.Sheet piles are special shapes of interlockingpiles made of steel, wood, or concrete whichform a continuous wall to resist horizontalpressures resulting from earth or water loads.The term sheet piling is used interchangeablywith sheet piles.

2-30. Uses.

Sheet piles are used to resist earth and waterpressure as a part of a temporary orpermanent structure.

a. Bulkheads. Bulkheads are an integralpart of watefront structures such as wharvesand docks. In retaining structures, the sheetpiles depend on embedment support, as incantilever sheet piling, or embedment andanchorage at or near the top, as in anchoredsheet piling.

b. Cofferdams. Cofferdams exclude waterand earth from an excavation to facilitateconstruction.

c. Trench sheeting. Trench sheeting whenbraced at several points is termed bracedsheeting.

d. Small dams and cutoff walls. Sheetpiles may be used to form small dams andmore frequently cutoff walls beneath water-retaining structures to control seepagethrough the foundations.

e. Bridge piles. Sheet piles are used in theconstruction of bridges and left in place. Forexample, a pier may be formed by drivingsteel sheet piling to create a circular enclosure,

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excavating the material inside to the desired available sizes and shapes are given indepth, and filling the enclosed space withconcrete.

f. Groins and sea walls. Sea walls areparallel to the coastline to prevent directwave and erosion damage. Groins or jettiesare perpendicular, or nearly so, to the coast-line to prevent damage from longshorecurrents or tidal erosion of the shore when themotion of the water is parallel, or at an angle,to the shoreline.

2-31. Materials.

a. Steel sheet piling. Steel sheet pilingpossesses several advantage over othermaterials. It is resistant to high drivingstresses, is relatively lightweight, can beshortened or lengthened readily, and maybereused. It has a long service life, either aboveor below water, with modest protection. Sheetpiling available through military supplychannels is listed in table 2-3. Commercially

TM 5-312. The deep-arch web and Z-piles areused to resist large bending movements(figure 2-9). Sheet pile sections of foreignmanufacture, either steel or concrete, shouldbe used when available. The sizes andproperties may differ appreciably from typescommonly available in the United States.

b. Fabricated timber sheet piling. Timbersheet piling may be fabricated for temporarystructures when lateral loads are relativelylight. Timber used in permanent structuresabove water level requires preservativetreatment as described for timber piles(chapter 8). Various types of timber sheetpiling are shown in figure 2-10. The heads arenormally chamfered and the foot is cut at a 60degree slope to force piles together duringdriving.

(1) Wakefield sheet piling. Wake field pilingis used in water and where hard driving is

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anticipated. Three rows of equal width a tongue-and-groove can be provided byplanking are nailed and bolted together so nailing a strip of wood on one edge formingthat the two outer planks form the grooveand the middle plank forms the tongue.Three 2-inch x 12-inch or three 3-inch x12-inch planks are usually used to formeach pile. Two bolts on 6-foot centers andtwo rows of spikes on 18-inch centersbetween the bolts hold the planks together.When bolts are not used, the spikes shouldbe driven in offset rows spaced 12 inchesapart.

(2) Tongue-and-groove piling. Milledtongue-and-groove piling is lightweightand used where watertightness is notrequired. If heavier timbers are available,

the tongue and two strips on the oppositeside forming the groove. Timber (6-inch x12-inch) may be interlocked by cutting2-inch grooves on each side and spiking aspline of hardwood, such as maple or oak,into one groove of the next timber.

(3) Offset timber sheet piling. An in-termediate type of sheet piling can befabricated consisting of two rows of 2-inchx 12-inch or 3-inch x 12-inch plankingwhich are bolted or spiked together so thatthe joints between the two rows of planksare offset.

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c. Rail and plank sheet piling. Railroad d. Concrete sheet piling. Typical concreterails and planking can be used in expedient sheet piling (figure 2-12) may be advan-sheet piling (figure 2-11). The planks should tageous in military construction whenbe leveled along both edges to fit snugly materials for their construction are available.against the adjacent rail. This piling is Due to their strength and durability, theyinstalled by alternately driving a rail, then a adapt well to bulkhead construction.plank.

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C H A P T E R 3

P I L E - D R I V I N G E Q U I P M E N T

Section I. STANDARD PILE-DRIVINGEQUIPMENT

3-1. Basic driving and installingmethods.

Piles are installed or driven into the groundby a rig which supports the leads, raises thepile, and operates the hammer. Rigs areusually manufactured, but in the field theymay be expedient, that is, constructed withavailable materials. Modern commercial rigsuse vibratory drivers while most older andexpedient rigs use impact hammers. Theintent is the same, that is to drive the pile intothe ground (strata).

3-2. Rig mounting and attachments.

Pile-driving rigs are mounted in differentways, depending on their use. This includesrailway, barge, skid, crawler, and truck-mounted drivers. Specialized machines areavailable for driving piles. Most pile drivingin the theater of operations is performedusing a steel-frame, skid-mounted pile driveror power cranes, crawlers, or truck-mountedunits, with standard pile-driving attachment(figure 3-1). The attachments availablethrough military supply channels include

adapters (figure 3-2) used to connect the leadsto the top of the crane boom leads and acatwalk or lead braces used to connect thefoot of the leads to the base of the boom. Theleads and catwalk assembly support drophammers weighing up to 3,000 pounds anddiesel hammers weighing up to 13,000 pounds.

3-3. Steel-frame, skid-mounted piledrivers.

A steel-frame, skid-mounted pile driver witha gasoline-driven engine is a class IV item(figure 3-3). This pile driver may be used onthe ground or on any permanent structure orsturdy transport. It can drive vertical orbatter piles. The reach from the base of theboom to the front of the leads depends uponthe weight of the hammer and power units.Reach may be increased by ballasting theback of the skid frame, or by securing it to thedeck on which it rests to counterbalance theweight of the equipment. The skid-mountedpile driver consists of the followingcomponents.

a. Skid frame. The skid frame is two steelI-beams 40 feet long, crose-braced 8 feet apartat the front of the frame and 12 feet apart at

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the rear of the frame. A platform at the rear of c. Leads. Leads standard to the unit are onethe frame supports the winch.

b. Boom. A 45-foot boom is anchoredskid frame 16 feet from the front end.

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8-foot top section, one 17-foot reversiblesection, one 10-foot extension, one 15-foot

to the intermediate section, and one 15-foot bottomsection, totaling 65 feet. The length of the

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lead may be reduced to 55 or 47 feet by leaving handles the hammer and pile lines. The leadsout sections. The length of the lead is to the skid-mounted pile driver can be tilteddetermined by the length of the pile to be transversely, longitudinally, or in a com-driven. The boom is attached to the midpoint bination of these as well as fore and aft of theof the top 20-foot section. A double-sheave vertical by adjusting the guides.bracket, attached at the top of the leads.

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d. Guides. Two types of guides permit the frame to the leads. It fixes the positionversatile aligning of the leads. of the base of the leads and holds them

(1) Fore-batter guide. The fore-batter guidevertically or at a fore-batter in the plane of

(figure 3-3), referred to as a spotter, is athe longitudinal axis of the equipment

beam extending from the forward end of(figure 3-4, 2).

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(2) Moon beam. The moon beam (figure 3-3)is a curved beam placed transversely at theforward end of the skid frame to regulateside batter.

e. Drive unit. The drive unit (not providedas part of the pile-driver rig) is a 2-drumwinch driven by a gasoline, diesel, or steamengine. The drive unit is mounted on theplatform at the rear of the skid frame.

f. Hammer. A 5,000-pound, double-actingsteam or pneumatic hammer; a 1,800-pound

or 3,000-pound drop hammer; or an 8,000-foot-pound or 18,000-foot-pound dieselhammer may be used.

3-4. Driving devices (hammer andvibratory driver).

There are three impact hammers used forpile-driving: the drop hammer, the pneumaticor steam hammer, and the diesel hammer.Drop hammers and diesel hammers arestandard engineering equipment. Table 3-1provides data on selected types of

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commercially available hammers. Vibratorydrivers/extractors are not classified ashammers and do not require pile caps forprotection against impact stresses. They areclamped to the pile to vibrate as a unit.

a. Drop hammers. The drop hammer (figure3-5) is a simple pile-driving hammerconsisting of a block of metal raised in theleads by the drive unit, then permitted todrop, striking the pile cap. Drop hammers arecumbersome, and their driving action is slowcompared to other hammers. Velocities atimpact are high and damage the top of a pile.Two standard drop hammers are available in

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military supply channels: size one weighs1,800 pounds; size two weighs 3,000 pounds.The maximum height of fall should be limitedto six feet. For most efficient driving, theweight of a hammer twice that of the pile willgive the best results. As an expedient, a loghammer (figure 3-6) may be fabricated andused. Drop hammers should be used only inremote sites or for a small number of pilings.

b. Air or steam hammers. The air or steamhammers (figure 3-7) consist of stationarycylinders and moving rams which include apiston and a striking head. The piston israised by compressed air or steam pressure. If

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the fall is gravity, the hammer is simpleacting. In double-acting hammers, the air orsteam pressure works on the upstroke anddownstroke. Because they provide a high rateof blows (90 to 150 blows per minute), theykeep the pile moving and prevent the buildingof friction thus enabling faster driving. Thedifferential-acting hammer uses higherpressures and lower volumes of air or steam.After being raised, the ram is valved to beused for the downstroke.

c. Diesel hammers. Diesel hammers areself-contained and need no air or steam lines.Fuel tanks are a part of the rig. Dieselhammers are well suited for military

operations. Table 3-2 contains a list of dieselhammers available through militarychannels and the types and sizes of pileswhich can be driven by each hammer. Sizes Aand D are suitable for use with 10-ton and20-ton drivers. Heavier hammers are moresuitable for use with 30-ton to 40-ton cranes.Diesel hammers may be either open-ended orclosed-ended as shown in figure 3-8.

Diesel hammers function as follows.

The ram is lifted by combustion of fueland compressed gas in a chamber betweenthe bottom of the ram and an anvil block inthe base of the housing.

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The crane-load line raises the ram for theinitial stroke, and an automatic tripmechanism allows the ram to drop.

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During this fall, fuel is injected into thecombustion chamber by a cam-actuatedfuel pump.

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Continuing its fall, the ram blocks the magnitude and duration of the drivingexhaust ports located in the cylinder and force.compresses the airlfuel mixture trappedbelow it to ignition temperature. As the ram rises, the exhaust and intake

ports are uncovered, combustion gasesWhen the ram hits the anvil, it delivers escape, and air enters. In the closed-ended

its energy through the anvil to the pile. At type, the housing extends over the cylinderthe same time, combustion occurs which to form a bounce chamber in which air isdrives the ram upward. The pressure of the compressed by the rising ram. Air trappedburning gases acts on the anvil for a and compressed above the piston helpssignificant time, thus increasing the

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stop the ram piston on its upward stroke 3-5. Caps and cushions.and accelerates it on its downward stroke.

The cycle is repeated.

d. Vibratory drivers/extractors.Vibratory drivers are a recent developmentin pile-driving equipment. They are used incommercial pile construction, especially indriving sheet piling. They are not part of themilitary inventory. Vibratory drivers usuallyrequire either an auxiliary hydraulic orelectric power supply. They consist of thevibrating unit which includes the rotatingeccentric weights, the suspension system thatisolates the vibratory forces from the liftingdevice, and the clamping system whichconnects the vibratory driver to the pile.Vibratory drivers have short strokes, lessthan two inches, and high impulse rates, upto 2,000 pulses per minute. Their drivingability derives from the vibrations and theweight of driver and pile.

Caps and cushions protect the top of the pileand reduce the damage caused by the impactof the hammer. Although they serve the samepurpose, they vary for different types ofhammers.

a. Drop hammers. A standard driving capfor timber piles used with a drop hammer is acast block. Its lower face is recessed to fit overthe top of the pile, and its upper face isrecessed to receive an expandable block ofhardwood in end-grained position to act as awasher (figure 3-5). The cap is fitted with awire rope sling so that the cap, as well as thehammer, may be raised to the top of the leadswhen positioning a pile in the leads.

b. Air and steam hammers. The ram of aVulcan hammer strikes a cap block positionedin the base of the hammer. In other hammers,such as the MKT type, the rams strike directly

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on the base or anvil. The top of the pile isprotected by a driving cap suspended fromthe base of the hammer and fitted to thedimensions of the pile. Driving caps for steelH-piles are shown in figure 3-9. The tops ofconcrete piles are usually protected fromlocal overstress by a pile cushion insertedbetween the drive head and the pile. The capblock and cushion serve several purposes;however, their primary function is to limitimpact stresses in both the pile and hammer.

Common types of cushion materials aresheets of Micarta with sheets of aluminum orlarge oak blocks in end-grained position.

c. Diesel hammers. Military dieselhammers are supplied with cushion blocksinserted between the anvil and the drive cap.The cushion blocks consist of laminatedplastic and aluminum or cast nylon. Ad-ditional cushioning is required betweenconcrete piles and the pile cushion.

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3-6. Pile-driving leads.

Pile-driving leads (figure 3-10) are tracks forsliding the hammer and guides to positionand steady the pile during the first part of thedriving. Standard steel leads are supplied inl-foot and 15-foot lengths. The 15-foot lengthis the top section. Leads must be ap-proximately 20 feet longer than the pile toprovide space for the hammer and ac-cessories. There are three types of leads.

a. Swinging leads. Swinging leads arehung from the crane boom by a crane line.The bottoms of the leads are held in placewhile the boom is positioned so that the pile isplumb or at the desired batter. Swingingleads are the lightest, simplest, and leastexpensive. They permit driving piles in a holeor over the edge of an excavation. Swingingleads require a three-line crane (leads,hammer, and pile). Precise positioning of theleads is slow and difficult.

b. Fixed, underhung leads. A spotter easilyand rapidly helps connect fixed, underhungleads to the boom point and to the front of thecrane. The leads are positioned by adjustingthe boom angle and spotter. A two-line craneis adequate to accurately locate the leads invarious positions. The length of the leads islimited by the boom length. Military standardleads are underhung from the crane boomand fixed to the crane by a catwalk. They arecomprised of a 15-foot top section and therequired number of 10-foot lower sections tomake up the required length (see figure 3-l).

c. Fixed, extended leads. Fixed, extendedleads extend above the boom point. They areattached with a swivel connection whichallows movement in all directions. A spotterconnects the bottom of the leads to the frontof the crane. A two-line crane is required. Aheadblock directs the crane lines over the topof the leads. Once the leads are set up, theycan be positioned quickly and accurately;however, initial setup time is extensive. Side

to-side as well as fore-and-aft adjustment ispossible. The military standard skid-mountedpile-driving rig has fixed, extended leadswith capabilities of side-to-side and fore-and-aft batter.

3-7. Spotters and lead braces.

The spotter connects the bottom of fixedleads (underhung or extended) to the front ofthe crane. With military standard leads usedwith a crane, the catwalk connects betweenthe bottom of the leads and the front of thecrane’s revolving upper machinery deck. Ittelescopes for fore-and-aft batter. The front of

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the spotter is moved for and aft for batterpiles, and side to side to plumb piles eitherhydraulically or manually. Special bottombraces are available which permit thisoperation (figure 3-11).

3-8. Followers.

Followers are fabricated pile extensionsplaced between the top of a pile and the

hammer. They are used when driving pilingbelow the water surface, especially with adrop hammer (which operates with reducedefficiency underwater) and with the dieselhammer (which cannot operate underwater).Followers are used under fixed or swingingleads and in tight spaces where there is noroom for the leads and the hammer, as in aclose pile grouping. When followers are used,the computation of the bearing value of the

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pile using a dynamic formula is uncertain.Followers must be rugged and constructed totransmit the full impact of the hammer andto hold the hammer and the pile in positivealignment. Followers can be fabricated fortimber, steel, and sheet piling.

a. Timber pile follower. The follower ismade from around timber of hardwood 10-to20-feet long. The bottom of the timber isinserted into, and bolted to, a follower capwhich is recessed at the bottom the same as apile cap. The top is trimmed to fit into the pilecap or hammer. If there is insufficient drivingspace for a follower cap, a flared wrought-steel band is bolted to the bottom of thetimber follower.

b. Steel pile follower. For a steel pilefollower, a section of the driven pile isreinforced by welding steel plates at the headto lessen damage from repeated use. Ex-tension plates that fit snugly against the pileto be driven are welded to the base.

c. Sheet pile follower. Projecting platesare riveted on each side of the sheet pile beingdriven. These riveted plates are shaped to fitthe form of the pile.

Section II. EXPEDIENT ANDFLOATING PILE-DRIVINGEQUIPMENT

3-9. Expedient pile drivers.

When standard pile drivers are not available,expedient pile drivers may be constructed.

a. Wood-frame, skid-mounted piledriver. A skid frame is made of two 12-inch x17-inch timbers 44 feet long. The frame iscross braced with 8-inch x 8-inch and 12-inchx 12-inch timbers and stiffened on both sideswith a king post and king-post cables. Theleads are standard or expedient. Figure 3-12shows expedient leads, 66 feet high made of

timber with the bearing surfaces faced withsteel plates to reduce wear and friction. Thefixed leads are supported by guys run to therear of the frame and by an A-frame from themidpoint of the leads to the midpoint of theframe. The rig can be skidded into placeusing a 2-drum winch. The rig is anchored,using natural anchors in the vicinity of thesite. Any pile-driver hammers discussed inparagraph 3-4 can be used.

b. Timber pile driver. Figure 3-13 shows arig with a 12-inch x 12-inch timber base andan A-frame using a section of standard leads.Cross braces are 3-inch x 12-inch members.The leads must be securely fastened to the tipof the A-frame and guyed at the base. Anotherdesign, using smaller dimensioned lumber, isshown in figure 3-14.

c. Tripod pile driver. Figure 3-15 shows ahand-operated rig constructed of local

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materials. The hammer, guide rod, blocks,and line (rope) are the only equipment thatmust be transported. This rig is particularlywell adapted for jungle operations where thetransportation of heavy equipment is dif-ficult. The rig will handle short lengths ofpiling up to 8 inches in diameter. Figure 3-16shows the design features of the pile driver.The spars are 8 to 10 inches in diameter and

are lashed with ½-inch line. The base framemust be ballasted while driving piles. A loghammer (figure 3-6) can be used to drive thepiles. The rig is built of hardwood and has asteel baseplate to protect the driving end. Theguide-rod hole and the guide rod must be wellgreased to prevent binding when the hammerfalls. The base of the guide rod is positionedby drilling a ¾-inch hole 6 to 8 inches deep in

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the head of the pile. Guying the pile helps four-wheel-drive truck or the front wheels ofposition the guide rod. any front-wheel-drive truck.

d. Welded-angle construction pile driver. 3-10. Power for expedient pile drivers.A piledriving rig can be built using fourheavy steel angles as leads and a laminated To raise the pile into position and operate thesteel plate cap of welded and bolted hammer in driving the pile, power is required.construction. The leads should be heavily When available, the power unit for a standardbraced and guyed (figure 3-17). The hammer skid-mounted pile driver should be used. Incan be operated by the rear wheels of any

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other cases a truck, truck motor, or manpowercan be used.

a. Truck. The hammer line can be snubbedto a truck bumper and the truck backed awayuntil the hammer is raised. The line is thenfreed allowing the hammer to fall (figure3-13). The wheels of a truck can be jacked andused as hoist drums (figure 3-17). The truckwinch should not be used except in emer-gencies since heavy use will cause excessivewear to the winch motor.

b. Truck motor. A truck motor can bemounted on the base frame of the rig. A drumis mounted on the drive shaft and controlledby the clutch. The hammer line is attached tothe drum.

c. Manpower. Hammers weighing up to1,200 pounds can be operated by 15-personcrews if there is sufficient pulling distance atthe site. Normally, a soldier hauling a linecan pull 50 to 80 pounds. When steel hammers

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are fabricated in laminated sections, they areeasier to hand-carry over difficult terrain.

3-11. Floating pile drivers.

a. Floating cranes. Barge-mounted cranescan be adapted for pile-driving operating byusing boom-point adapters and pile-drivingattachments. If standard leads are notavailable, they should be improvised fromdimensioned lumber faced with steel plateand adequately braced. For pile driving, afloating crane may be maneuvered with itsown lead lines, and spuds put down beforedriving begins.

b. Barges or rafts. Crane-shovel units orskid-mounted pile drivers may be mounted onbarges or rafts for work afloat. Driving maybe off the end or side of the raft, depending onproblems of current and maneuverability.Sandbags can counterbalance a raft to enablethe pile driver to be positioned close to the endof the raft to extend its reach. A standard4-foot x 7-foot barge assembly is adequate tosupport a pile driver adapted from a 12 ½-toncrane (figure 3-18). A pile driver adapted froma skid-mounted pile driver can be mounted ona 5-foot x 12-foot barge assembly (figure 3-19).

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c. Pneumatic floats. Cranes or skid-mounted pile drivers may be mounted onrafts assembled from pneumatic floats whichserve as platforms. Driving off the end or sideof the float using counterbalances (such assandbags) applies to this type of rig.

d. Anchoring of rafts. The raft must beheld securely to position the pile accuratelyand to hold the leads and hammer in linewith the pile during driving. For the first pileof an isolated off-shore structure, such as adolphin, two transverse lines on capstans atbow and stern and one longitudinal line on adeck capstan will hold the craft if the floating

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rig is not furnished with spuds. The first piledriven may be used as one of the anchors. It ispossible to run the steadying lines fromanchorages onshore. More control of the raftcan be obtained if the lines are run like springlines from a berthed ship, so that they crosseach other diagonally.

Section III. OTHER PILE-DRIVINGEQUIPMENT

3-12. Accessory equipment.

a. Support equipment. Equipment must beavailable for handling stockpiled piling and

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for straightening, cutting, splicing, capping, couplings. The pipes and fittings are madeand bracing piles. into a jetting assembly, and the water hoses

and couplings are used to connect the jettingb. Jetting equipment. Jetting is a method assembly to a water pump (figure 3-20).of forcing water around and under a pile toloosen and displace the surrounding soils. (1) Jetting pipes. Jetting pipes are usuallyJetting operations are discussed in chapter 4, from 2½ to 3½ inches in diameter. Thesection II. The equipment consists of steel pipes are reduced to about half theirpipes, pipe fittings, water hoses, and

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diameter to form nozzles at the point ofdischarge.

(2) Jetting pump. The jetting pump must becapable of delivering 500 gallons perminute (gpm) at a pressure of 150 to 200pounds per square inch (psi). Gasoline ordiesel-powered centrifugal pumps havingfrom two to four stages and developingfrom 100 to 300 psi are normally used. Foruse in gravelly soils, water pressure shouldrange from 100 to 150 psi. For sands, waterpressure from 50 to 60 psi is generallyadequate.

(3) Jetting sizes. Jet sizes are normally 2 ½inches for 250 gpm, 3 inches for 250 to 500gpm, and 3 ½ inches for 500 to 750 gpm.

(4) Jetting with air. Air may be used forjetting either alone or with water. Aircompressors are required.

c. Sleeve. A sleeve is a 4-foot section of steelpipe bolted to the jaws of the hammer to holdthe pile in place for driving when leadscannot be used. A three-point suspensionkeeps the hammer fixed at the desired anglewhen driving batter piles (figure 3-21, 1).

d. Pants. Pants consist of parallel platesbolted to the hammer body. These fit over thetop of sheet piling that is being driven withoutthe use of leads and serve to guide the hammer(figure 3-21, 2).

3-13. Equipment selection.

In military pile construction, little op-portunity exists for selecting the equipmentused in a given operation. Reduction instandard military equipment items availablefrom the table of organization and equipment(TOE) and class IV equipment has simplifiedthis problem. When selection is possible,consider the following factors.

a. Ground conditions. Stable soil con.ditions permit the use of truck-mountedcranes, while boggy areas require crawler-mounted units.

b. Piles. The number, size, and length ofpiles affect the choice of equipment. Diesel,air, or steam hammers are used to drivebatter piles. Long piles require a large rigwith long leads. It is better to drive a long pileas a continuous section than to drive shortsections since alignment is controlled.

c. Hammers. Selection of the type and size ofhammer will depend on availability, the typeof pile, and the anticipated loadings.

For air and steam hammers (singleacting or double-acting) the ratio of ramweight to pile weight should fall between1:1 and 1:2. For diesel hammers, the ratioshould fall between 1:1 and 1:4.

All types of air, steam, and dieselhammers can be used to drive timber pilesprovided they have energy ratings between15,000 and 20,000 foot-pounds. Hammerswith a rated energy up to 26,000 foot-pounds can be used for timber piles withbutt diameters of 15 inches or more. Specificguidance for selecting the size of dieselhammers is provided in table 3-1.

Except for diesel hammers, the size of thehammer selected should be one in whichthe desired energy is developed by heavyrams striking at low velocity. A highvelocity impact wastes a large amount ofthe striking energy. It also deforms the pilehead leaving less energy available for theuseful purpose of driving a pile.

The energy of a diesel hammer isdeveloped by a combination of the fallingof the ram, compression of the air in thecombustion chamber, and the firing of thediesel fuel. This combination eliminates

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the need for a heavy ram at a low velocityand depends only on sufficient energy toproperly move the pile.

With air or steam hammers, a double-acting or differential-acting hammer ispreferred when piles must be driven toconsiderable depth where penetration perblow is small. The greater frequency ofblows give faster penetration.

The simple-acting hammer can be usedwhere the soil above the bearing stratumcan be penetrated rapidly under easydriving conditions.

For driving precast concrete piles, aheavy ram with low impact velocity isrecommended. When driving is easy,hammer blows should be minimized untilresistance develops. This may avoid stresswaves that might cause cracking.

3-14. Equipment assembly.

Skill and caution are required in the erectionof pile-driving equipment. Assembly in-formation is not within the scope of thismanual. For comprehensive assembly in-structions, consult the operator’s manual forthe pile-driving equipment to be used.

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C H A P T E R 4

PILE INSTALLATION

Section I. PREPARATION OF PILES FOR DRIVING

4-1. Preparation of timber piles.

Timber piles selected for a structure should belong enough so that the butts are 2 or 3 feethigher than the finished elevation after thepiles are driven to the desired penetration.(Methods of predetermining pile lengths aredescribed in chapter 5.) Timber piles requirelittle preparation or special handling;however, they are susceptible to damageduring driving, particularly under harddriving conditions. To protect the pile againstdamage, the following precautions should betaken.

a. Fresh heading. When hard driving isexpected, the pile should be fresh headed byremoving 2 to 6 inches of the butt. Removinga short end section allows the hammer totransmit energy more readily to the lowersections of the piles. Butts of piles that havebeen fresh headed should be field treatedwith creosote and coal tar pitch (chapter 8),after the pile has been driven to the desiredpenetration.

OPERATIONS

b. Fitting. Proper fit between the butt of thepile and the driving cap of the hammer is themost important factor in protecting the pilefrom damage during hard driving. The buttof the pile must be square cut, shaped to fitthe contour of the driving cap, and a littlelarger than the dimensions of the cap so thewood will be compressed into the driving cap.Under most driving conditions the tip of atimber pile should be left square withoutpointing. The following points should be keptin mind when fitting timber piles.

Pointing timber piles does little to in-crease the rate of penetration.

Piles with square tips are more easilykept in line during driving and providebetter end bearing.

For very hard driving, steel shoes protectthe tips of piles (figure 4-1, 1). Steel platesnailed to blunt tips (figure 4-1, 2) offerexcellent protection.

c. Wrapping. If a driving cap is not used, orif crushing or splitting of the pile occurs, thetop end of the pile should be wrapped tightlywith 12-gage steel wire to forma 4-inch band.The steel wire should be stapled firmly in

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place. This is a simple method of protectingpile butte during hard driving. Steel strappingabout 1¼ inches wide will also provideadequate protection. Strapping should en-circle the pile twice, be tensioned as tightly aspossible, and be located approximately twofeet from the butt.

d. Splicing. Piles can be spliced if singlesections of the required length are notavailable or if long sections cannot behandled by available pile drivers. Generally,

decreasing pile spacing or increasing thenumber of piles is preferable to splicing.Except in very soft soils or in water, thediameter of the complete splice should not begreater than the diameter of the pile (figure4-2). The ends of the piles must be squared,and the diameter trimmed to fit snugly in the8-inch or 10-inch steel pipe. Steel splice platesare also used (figure 4-2).

e. Lagging. Lagging a friction pile with steelor timber plates, planks, or rope wrapping

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can be used to increase the pile’s load-carryingcapabilities.

4-2. Preparation of steel piles.

a. Reinforcing. Point reinforcement isseldom needed for H-piles; however, if drivingis hard and the overburden contains ob-structions, boulders, or coarse gravels, theflanges are likely to be damaged and the piles

may twist or bend. In such cases H-piles(figure 4-3) and pipe piles (figure 4-4) shouldbe reinforced.

b. Cleaning. Pipe piles driven open-ended,must be cleaned out before they are filledwith concrete. Ordinarily they are closedat the lower end, usually with a flat plate(figure 4-4). In a few soils, such as stiff plasticclays, the overhang of the plate should be

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eliminated. Such pipe piles can be inspectedafter driving. Damaged piles should be iden-tified and rejected if not repairable.

c. Splicing. H-piles can be spliced anddesigned to develop the full strength of thepile both in bearing and bending. This isdone most economically with butt-weldedsplices (figure 4-5). This method requires thatthe pile be turned over several times during

the welding operation. Various types of plateand sleeve splices can be used (figure 4-6).Splicing is often performed before the pilesare placed in the leads so pile-drivingoperations are not delayed.

d. Lagging. Lagging is of questionable valueand if attached near the bottom of the pile,will actually reduce the capacity of the pile.

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4-3. Preparation of concrete piles.

Precast concrete piles should be straight andnot cambered by uneven prestress or poorconcrete placement during casting.

a. Reinforcing. Reinforcing of precastconcrete piles is done in the manufacturing.The top of the pile must be square orperpendicular to the longitudinal axis of thepile. The ends of prestressing or reinforcingsteel should be cut flush with the end of thepile head to prevent direct loading by the ramstroke. Poured concrete piles may be re-inforced with steel reinforcing rods.

b. Splicing or cutting. Precast concretepiles are seldom, if ever, spliced. If the drivinglength has been underestimated, the pile canbe extended only with considerable difficulty.The piles are expensive to cut if the lengthhas been over estimated. Poured concretepiles should not require splicing as length ispredetermined in the planning stages.

Section II. CONSTRUCTIONPROCEDURES

4-4. Positioning piles.

When piles are driven on land, for example abuilding foundation, the position of each pilemust be carefully established, using availablesurveying equipment. A simple template canbe constructed to insure proper positioning ofthe piles. Piles generally should not be drivenmore than three inches from their designlocation. Greater tolerances are allowed forpiles driven in water and for batter piles.

4-6. General driving procedures.

Piles are set and driven in four basic steps(figure 4-7).

a. Positioning. The pile driver is broughtinto position with the hammer and cap at thetop of the leads (figure 4-7, 1).

4-8

b. Lashing. Generally, the pile line is lashedabout one third of the distance from the top ofthe pile, the pile is swung into the helmet, andthe tip is positioned into the leads (figure 4-7,2). A member of the handling crew can climbthe leads and, using a tugline, help align thepile in the leads.

c. Centering. The pile is centered under thepile cap, and the pile cap and hammer arelowered to the top of the pile. If a drophammer is used, the cap is unhooked from thehammer (figure 4-7, 3).

d. Driving. The hammer is raised anddropped to drive the pile (figure4-7, 4). Drivingshould be started slowly, raising the hammeronly a few inches until the pile is firmly set.The height of fall is increased gradually to amaximum of 6 feet. Blows should be appliedas rapidly as possible to keep the pile moving.Repeated long drops should be avoided sincethey tend to damage the top of the pile.

4-6. Driving requirements.

Careful watch must be kept during driving toavoid damage to the pile, pile hammer, orboth. Precautions and danger signs includethe following

a. Support. The pile driver must be securelysupported, guyed, or otherwise fastened toprevent movement during driving.

b. Refusal. Refusal is reached when theenergy of the hammer blow no longer causespenetration. At this point, the pile has reachedrock or its required embedment in the bearingstratum. It is not always necessary to drivepiles to refusal. Friction piles frequently mustbe driven only far enough to develop thedesired load bearing capacity. In certaintypes of soils, such as a very soft organic soilor deep marsh deposit, a considerable lengthof pile may be necessary to develop adequateload capacity. Driving in such soils isfrequently easy as piles may penetrate several

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feet under a single hammer blow. It isimportant that driving be a continuousprocedure. An interruption of even severalminutes can cause a condition of temporaryrefusal in some types of soils, thus requiringmany blows to get the pile moving again.

c. Timber piles. Timber piles are frequentlyoverdriven when they are driven to endbearing on rock (figure 4-3). If the pile hits afirm stratum, depth may be checked bydriving other piles nearby. If the piles stop atthe same elevation, indications are that afirm stratum has been reached. Followingare items to be watched for when drivingtimber piles.

(1) Breaking or splitting below ground. Ifthe driving suddenly becomes easier, or ifthe pile suddenly changes direction, thepile has probably broken or split. Furtherdriving is useless as bearing capacity isunreliable. Anew pile must be driven closeto the broken one, or the broken one pulledand a new one driven in its place.

(2) Pile spring or hammer bounce. The pilemay spring or the hammer may bouncewhen the hammer is too light. This usuallyoccurs when the butt of the pile has beencrushed or broomed, when the pile has metan obstruction, or when it has penetratedto a solid footing.

(3) Double-acting hammer bounce. When adouble-acting hammer is being used, toomuch steam or air pressure may causebouncing. When using a closed-ended dieselhammer, lifting of the hammer on theupstroke of the ram piston can causebouncing. This is caused by too high athrottle setting or too small a hammer.Throttle controls should be backed off justenough to avoid this lifting action.

(4) Crushed or broomed butt. If the butt of atimber pile has been crushed or broomed

4-10

for approximately 1 inch, it should be cutback to sound wood before driving iscontinued. There should be no more thanthree or four final blows per inch for timberpiles driven with a diesel, steam, or airhammer. Further driving may fracture thepile or cause brooming.

d. Steel piles. In driving steel piles, par-ticular care must be taken to see that thehammer strikes the top of the pile squarely,with the center of the hammer directly overthe center of the pile. Watch for the following.

(1) Slack lines. A hammer suspended froma slack line may buckle the top section andrequire the pile be trimmed with a torchbefore driving can proceed. Driving caps(previously described) will prevent thistype of damage to H-piles.

(2) Alignment. When a steel pile is drivenwith a flying hammer (free-swing hammer),the pile should be aligned with guys (figure4-9). Hooks, shackles, or cable slings canbe used to attach guy lines. A pile should beconsidered driven to refusal when fiveblows of an adequate hammer are requiredto produce a total penetration of ¼ inch orless.

e. Concrete piles. Required driving re-sistances for prestressed concrete piles areessentially the same as for steel piles. Drivingstresses should be reduced to prevent piledamage. The ram velocity or stroke should bereduced during initial driving when soilresistance is low. Particular attention shouldbe paid to the following.

(1) Cap or helmet. The pile-driving cap orhelmet should fit loosely around the piletop so the pile may rotate slightly withoutbinding within the driving head.

(2) Cushioning. An adequate cushioningmaterial must be provided between thehelmet or driving cap and the pile head.

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Three or four inches of wood cushioningmaterial (green oak, gum, pine, or firplywood) are adequate for piles less than50 feet in length in a reasonably goodbearing stratum. Cushions 6 inches thickor more may be required when drivinglonger piles in very soft soil. The cushionshould be placed with the grain parallel tothe end of the pile. When the cushionbecomes highly compressed, charred, orburned, it should be replaced. If driving ishard, the cushion may have to be replacedseveral times during the driving of a singlepile.

f. Special problems. Special problems mayarise when driving various types of piles. Alist of potential problems, with possiblemethods of treatment, is shown in table 4-1.

4-7. Aligning piles.

Piles should be straightened as soon as anymisalignment is noticed during the driving.When vertical piles are driven using fixedleads, plumbing is not a matter of concernsince the leads will hold the pile and correctthe alignment. Vertical piles normally shouldnot vary more than 2 percent from the plumbposition.

a. Checking misalignment. Along mason’slevel is useful in plumbing the leads. Forbatter piles (figure 4-10) a plywood templatecan be used with the level. Exact positioningis easier if the driver is provided with aspotter or moon beam.

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b. Checking misalignment by cap re- alignment. The alignment can be checked bymoval. If the pile is more than a few inches lifting the cap from the pile butt. The pile willout of plumb during driving, an effort should rebound laterally if not properly aligned withbe made to restore the pile to its proper the leads and hammer.

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c. Aligning with block and tackle. Duringdriving, a pile may be brought into proper

H-piles, this procedure may induce un-desirable twisting and should be avoided if

alignment by using block and tackle (figure4-11). The impact of the hammer will tend to

possible. Jetting either alone or with thepreceding method, may be used.

jar the pile back into line. In the case of steel

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4-8. Obstructions.

Obstructions below the ground surface areoften encountered during pile-drivingoperations. Obstructions may result fromfilling operations in the area or from oldstumps or tree trunks buried by later deposits.Obstructions are frequently encounteredwhen piles are driven in industrial andcommercial areas of older cities or alongwaterfronts. They are a matter of concernsince they can prevent a pile from penetratingenough to provide adequate load-carryingcapacity. Piles are frequently forced out ofline by obstructions and may be badlydamaged by continued driving in an effort tobreak through the obstruction.

a. Driving. When an obstruction such as arotten log or timber is encountered, 10 or 15extra blows of the hammer may cause the pileto breakthrough (figure 4-12, 1). With steel orprecast concrete bearing piles, extra blows ofthe hammer may break or dislodge a boulder(figure 4-12, 2); however, care must be takenthat blows do not damage the pile. Pilealignment should be watched carefully duringthis operation to insure that the lower portionof the pile is not being deflected out of line.

b. Using explosives. If the obstructioncannot be breached by driving, the pile shouldbe withdrawn and an explosive chargelowered to the bottom of the hole to blast theobstruction out of the way (figure 4-12, 3). Ifusing explosives is not practical, the pile canbe left in place, and the foundation plan canbe changed to use other piles.

c. Jetting. Jetting is particularly valuable insoils which will settle firmly around the pile.Sands, silty sands, and some gravels provideconditions suitable for jetting as drivingthrough these materials in a dense stateresults in pile damage. Displacement piles incohesionless soils are frequently placed byjetting.

(1) Hose and pipe jetting. Jetting isperformed by inserting the jet pipe to thedesired depth, forcing water through thepile to loosen the soil, then dropping thepile into the jetted hole and driving the pileto its resistance. If the pile freezes beforefinal embedment, jetting can be resumed.Jetting should not be deeper than 4 or 5 feetabove final grade.

(2) Attached jetting pipes and hoses.Jetting for timber, steel, or standardprecast concrete piles is usually done by anarrangement of jetting pipes and hoses.The jet pipe is connected with a flexiblehose and hung from the boom or the piledriver leads. When possible, two jet pipesare lashed to opposite sides of the pile.Usually the pile is placed into positionwith the hammer resting on it to giveincreased weight, and the jet is operated sothat the soil is loosened and displacedevenly from under the tip of the pile (figure4-13). A single jet, however, is not workedup and down along the side of the pile, asthe pile will drift in that direction. Properuse of jet pipes is shown in figure 4-14.

(3) Special precast concrete jetting. Tofacilitate jetting, jet pipes can be embeddedinto precast concrete piles, Jetting ar-rangements for precast concrete piles areshown in figure 4-15.

(4) Precautions. Where piles must be drivento great depths, the double water jets maybe insufficient. Additional compressed aircan be effective. For combined water andair jetting, the simplest method is to tack-weld a small air pipe to the outside of thewater-jet pipe. In any jetting operation, thealignment of the pile is critical. Jetting is auseful method to correct the alignment oftimber piles in a pile bent (figure 4-16).Jetting around a pile while it is beingdriven is undesirable as the pile will driftoff line and location. Pile tips must be well

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seated with reasonable soil resistance 4-9. Predrilling.before full driving energy is used. Theultimate bearing capacity of the pile is It may be necessary to predrill pilot holes ifgenerally not significantly affected by the soils above the bearing stratum arejetting. However, jetting will greatly re- unusually stiff or hard. Predrilling keeps theduce the uplift capacity of a pile. preservative shell of treated timber piles

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intact. Predrilling also reduces underwaterheave and lateral displacement of previouslydriven adjacent piles. Holes are drilledslightly smaller than the diameter of the pileand to within a few feet of the bearingstratum. The pile is inserted, and the weightof the hammer forces the pile down near thebottom of the drill hole displacing any slurry.The pile is then driven to the requiredpenetration or resistance.

a. Rotary equipment. Predrilling should bedone with wet rotary equipment which leavesthe hole filled with a slurry of mud. Themethod employs a fishtail bit that contains awater jet within the drill stem. The water anddrill cuttings form a slurry which lines thewalls and stops sloughing of unstable soillayers. Additives (such as bentonite) can alsobe used to stabilize the walls of the drill hole.

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b. Augers. Augers which remove all materialfrom the hole can cause a quicksand action.Sand or soil may flow into the drilled holebelow the water table. Augers should be usedonly above groundwater tables and in soilswhere a drill hole will stand open withoutcollapsing.

4-10. Special placement techniques.

a. Spudding. Spuds can penetrate debris orhard strata so the pile can reach the bearingstratum. Spuds consist of heavy pile sections,usually with special end reinforcement. Whenheavy piles (such as steel or precast concretepiles) are driven, the pile may be raised anddropped to break through a layer of hardmaterial or an obstruction. In a similaroperation, a pilot pile is withdrawn, and thefinal pile is driven in the hole.

b. Jacking. A pile may be jacked intoposition. This method is usually used when itis necessary to underpin the foundation of astructure and headroom is limited or whenvibration from conventional driving coulddamage an existing structure. The pile isjacked in sections using a mechanical orhydraulic screw jack reacting against theweight of the structure. The pile is selected forthe specific situation, and it is built up inshort, convenient lengths.

c. Vibrating. High-amplitude vibrators areused for driving piles in saturated sand andgravels, Vibratory hammers are particularlyadvantageous for driving sheet piling.

4-11. Driving piles in water.

a. Positioning piles. When piles are drivenin water, different methods may mark thedesired pile positions. When a number ofbents are to be constructed, a stake is placedat each abutment approximately 6 inchesfrom the pile centerline (figure 4-17). A wirerope is stretched between the two stakes, and

a piece of tape or cable clip is fastened to therope at each pile bent position. Piles are thendriven at each tape or cable clip.

b. Using floating pile drivers. When afloating pile driver is used, a frame forpositioning piles may be fastened to the hull.A floating template is sometimes used toposition piles in each bent (figure 4-18).Battens are spaced along the centerlinedesired for each pile. The battens are placedfar enough apart so that, as the pile is driven,the larger-diameter butt end will not bind onthe template and carry it underwater. If thepiles are driven under tidal water, a chain orcollar permits the template to rise and fallwith the tide. If the ends of the battens arehinged and brought up vertically, thetemplate may be withdrawn from betweenthe bents and floated into position for thenext bent provided the pile spacing is uniform.

c. Using floating rigs. If a floating rig isavailable, it can be used to drive the piles foran entire structure before the rest of the work.In general, more piles can be driven per man-hour with floating equipment because thedriver is easily moved. As soon as the piles inone bent have been driven, the rig may bepositioned to drive the next bent, while thebent just driven is braced and capped.Floating pile. driver rigs are difficult toposition where currents are strong andadequate winches are unavailable. Otherwise,they can be positioned easily either end-on orside-on to the pile bent which is being driven.Batter piles can be driven in any desireddirection by adjusting the spotter or catwalk,without using a moon beam.

d. Driving from bridge or wharf. Whenpile driving uses mobile equipment operatingfrom a deck of a bridge wall structure, twoprocedures may be used in moving the piledriver forward.

(1) Walking stringer method. As each bentis driven, the piles are aligned, braced, cut,

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and capped. The movable stringers aremade by placing spacer blocks betweentwo or three ordinary stringers so thedriving rig can advance into position todrive the next bent. The movable stringersare laid onto the bent which has just beencompleted. When the advance row or rowsof piles have been braced, cut, or capped,the pile driver picks up the temporarystringers behind and slings them into placeahead. The installation of permanentstringers and decking follows behind thepile driver. Variations of this method arepossible when a skid-mounted piledriver isused. This method gives the pile driver lessidle time than the method described in (2)following. Since the decking operationsare completely separate, individual crewscan be developed to drive, cut, cap, anddeck. These crews become more proficientand are more rapid than crews that work

at all three operations. This is hazardousbecause the machinery is supported byloose stringers and decking. Skill andorganization are required because severaloperations may be in progress at the sametime. Piles must move through the deckingcrews to reach the driving point, soplanning is important.

(2) Finish-as-you-go method. Instead ofusing movable stringers, each bent orbench, including the permanent stringersor decking, may be completed before therig is moved forward. This method is saferand requires less organization, since oneoperation follows another. The pile drivermay be idle or set stringers. To completeeach panel, personnel rotate jobs.

e. Driving from temporary earthcauseways. An excellent method for driving

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piles for a bridge or wall structure in shallowwater is to extend a temporary earth causeway from the shore. Piles may then be drivenusing a mobile rig operating on the causeway.In the usual case, piles are driven through thefill. This is the fastest method of buildingbridges and other structures, where heightlimitations permit and required penetrationsare not unusual.

f. Driving from the 50-ton standardtrestle. Used in depths up to eight feet, thistrestle can drive two or three times as manypiles as a bridgemounted trestle. This methodinvolves constructing the bays (supportstructures) and using them as a platform.After completing a pile bent, a pile driverwalks the standard trestle by striking the baynearest the completed work, swinging it, andre-erecting it ahead.

g. Aligning. When all piles in a bent havebeen driven, they can be pulled into properposition with block and tackle and analigning frame (figures 4-19, 4-20). Bracingand subsequent construction of pile bents aredescribed in TM 5-312.

4-12. Driving underwater.

It is sometimes necessary to drive pilesunderwater rather than use a pile follower.Special pile hammers are designed for drivingunderwater. Recommendations by themanufacturer should be followed in preparingand rigging the hammer for underwaterdriving. Diesel hammers cannot operateunderwater.

4-13. Pulling piles.

Piles split or broken during driving or drivenin the wrong place ordinarily should be pulled.In some cases, it may be necessary to pullpiles to clear an area. Sheet piles and,occasionally, bearing piles that have beendriven for a temporary structure may be

salvaged by pulling. Piles should be removedas soon as possible, since the resistance topulling may increase with time. Commonmethods for pulling piles are described below.

a. Direct lift. If a pile is located so that acrane of substantial capacity can be moveddirectly over it, pulling by direct lift ispossible. A sling should be wrapped aroundthe pile and the pull steadily increased untilthe pile begins to move or is extracted. Jettingcan be used to help loosen a pile. The boomshould be snubbed to a stationary object tokeep it from whipping back if the pilesuddenly comes loose or the lifting tacklebreaks.

b. Hammer and extractor lift. Piles maybe pulled with air or steam-powered extractorsor with inverted acting hammers rigged forthis use. Vibratory hammers are effective.Usually, a 25-ton lift on the extractor will beadequate, but multiplereeved blocks in aderrick may be needed. If piles are difficult topull, additional driving may break them loose.Use a safety line at the tip of the boom in casethe connecting line or cable breaks.

c. Tidal lift. Piles in tidewater maybe pulledby attaching the slings to barges or pontoonsat low tide and allowing the rise of the tide toexert the lifting force. To keep barges fromtipping, a barge should be placed on eitherside of the pile; and the lifting force should betransmitted by girders extending across thefull width of both barges.

4-14. Pile driving in cold weather.

It is possible to conduct pile-drivingoperations in severe cold even though theground is frozen. Frost up to two feet thickcan be broken successfully by driving a heavypilot pile or a heavy casing. Ground can bethawed to a shallow depth by spreading alayer of several inches of unflaked lime overthe area, covering the layer with snow, then

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with a tarpaulin, which in turn is coveredwith snow. This method will melt a layer offrost 3 feet thick in 12 hours. Earth augers areeffective in drilling holes in frozen groundand may aid pile driving. Holes cut in soundriver ice act as guides for piles for bridgefoundations. Auxiliary equipment such as asteam or air hammer and other machineryrequire special handling in cold weather.

Instructions furnished by the manufacturermust be carefully followed.4-15. Pile installation in permafrost.Construction operations under arcticconditions and in permafrost areas arediscussed in TM 5-349. Pile installationmethods in permafrost include steam or waterthawing, dry augenng, boring, and driving.

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a. Steam or water thawing. Piles can beinstalled in permafrost by prethawing theground with steam points or water. Steam at30 psi delivered through a l-inch steel pipe issatisfactory for depths up to 15 or 20 feet. Forgreater depths, higher steam pressure (60 to90 psi) and larger pipes (2-inch) are used.Water jetting is used if the soil is sandy. Thepile is hammered lightly into the ground, andthe steam aids the penetration while

scaffolding or an A-frame facilitates handlinglong sections of steam-jetting and water-jetting pipes. The steam demand is ap-proximately 15 to 20 cubic feet per foot ofpenetration. When the final depth is reached,the steam point is kept in the hole to make thehole big enough to accept the pile. If the soil issandy, the steam point is kept in place for ½hour; if the soil is clay, it may remain for upto 3 hours. Figure 4-21 shows the approximate

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shape of the hole thawed in sand-silt soilafter 1½ hours of stem jetting.

(1) Setting the pile. After the hole has beenthawed properly, the pile is placed by theusual methods. After three to four days ofthawing, a series of piles may be set (figure4-22). Wooden piles have a tendency tofloat when placed in the thawed hole andtherefore must be weighted or held downuntil the permafrost begins to refreeze.

(2) Disadvantages. Steam or water thawinghas the disadvantage of introducing somuch heat into the ground that freeze back

may be indefinitely delayed. Piles may notdevelop adequate bearing capacity, or-hostheave may work them out of the groundand damage supported structures. Steamor water thawing should not be used inareas where the mean annual permafrosttemperature is greater than 200F. Thismethod may be used in colder permafrostonly with exceptional precautions tocontrol heat input into the ground if othermethods of installation are not possible.

b. Dry augering. Pile holes maybe drilledin the permafrost using earth augers withspecially designed bits for frozen ground.

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Holes 2 feet in diameter can be advanced atrates of up to about 1 foot per minute in frozensilt or clay, depending on the type of bit,ground temperature, and size of equipment.Holes up to 4 feet or more in diameter can bedrilled readily in such soil. Drilling with anauger is the easiest method when the frozenground surface permits ready mobility andsteam and water do not have to be handled.This method is not feasible in coarse, frozensoils containing boulders.

(1) Hole drilling. The holes maybe drilledundersized, and wood or pipe piles maybedriven into the holes. However, the holesusually are drilled oversized; and a soil-water slurry is placed in the annulus’ spacearound the pile and allowed to freeze back,effectively transferring the imposed pileloads to the surrounding frozen soil.

(2) Slurry. Silt from a borrow pit or fromthe pile hole excavation can be used forslurry as can gravelly sand, silty sand, orplain sand. Clays are difficult to mix andblend, and when frozen they are not strong.Gravel, unsaturated soil, water, or concreteshould not be used for backfill in permfrostareas. Organic matter must not be used inslurry. Details on dry augering are con-tained in TM 5-852-4.

c. Boring. Holes for piles may be made byrotary or churned drilling or by drive coring(under some conditions) using various bitsand drive barrels. Frozen materials areremoved with air, water, or mechanicalsystems. Procedures are the same as for dry-augered holes.

d. Driving. Conventional or modified piledriving procedures, including diesel andvibratory hammers, may be used to driveopen-ended steel pipe and H-piles to depthsup to 50 feet or more in frozen groundcomposed of silty sand or finer-grained soilsat ground temperature above 25°F. Under

favorable conditions heavy pipe and H-pilescan be driven into the ground at lowertemperatures. Freeze back is complete within15 to 30 minutes after driving. The H-piledriven in frozen soil should not be smallerthan the HP 10 x 42, and the rated hammerenergy should not be less than 25,000foot-pounds.

4-16. Cutting and capping of piles.

a. Timber piles. The capping of timber-pilebents should bear evenly on every pile in thebent. The piles should be cutoff accurately byfollowing sawing guides nailed across allpiles in the bent (figure 4-23). After the pilesare cut and treated with preservatives, thecap is placed and fastened to the piles by driftpins driven through holes bored from the topof the cap into each pile. If a concrete cap isused, the tops of timber piles should be cutsquare, treated with preservative, andembedded in the concrete at least 3 inches.

b. Steel piles. Steel-pile bents are cut to theproper elevation using a welding torch. Aworking platform and cutting guide fastenedwith C-clamps can be used for this purpose(figure 4-20). Capping of steel piles with steelmembers follows the same procedure asoutlined for timber piles, but the members arejoined by welding or riveting, and steel platesare used rather than timber splices or scabs.If the cap is reinforced concrete, the top of thepile should be embedded at least 3 inches inthe concrete. A well-designed reinforcedconcrete pile cap does not require steel platesto transmit a compressive load to H-piles. Ifthe piles are subject to uplift, cap plates oradditional embedment is required.

c. Concrete piles. Cutting concrete pilesrequires concrete saws, pneumatic hammers,and an acetylene cutting torch. A V-shapedchannel is cut around the pile at the level ofthe desired cutoff. Reinforcing bars areexposed and cut with the torch at the desired

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point above the cutoff. If possible, thereinforcing bars should project into a concretecap for bonding. The head of the pile can bebroken off by wedging or pulling with a linefrom a crane. The cap is placed on top of thepiles by casting in place or drilling groutholes at the proper position in a precast cap.Another suitable method is to drill holes andto grout in bolts or reinforcing steel,depending on the type of cap used.

d. Anchorage. The uplift force on a structureis transmitted to the pile by a bond betweenthe pile surface and the concrete of the pilecap, or by a mechanical anchorage. Theultimate bond between concrete and freshly-embedded timber piles may be 60 psi or more;however, long submergence may cause somedeterioration of the outer layer of wood whichreduces the bond value. When the embeddedportion of timber piles is submerged, aworking stress for a bond of not more than 15psi should be used without considering theend surface of the pile. When the load intension is greater than the strength whichcan be developed by the bond, a mechanicalanchorage can be used. The resistance of awood pile to extraction from concrete maybeincreased by notching the embedded portionof the pile and considering the longitudinalshearing strength of the timber.

Section III. PREPARATION AND USEOF PILES

4-17. Sheet piles.

a. Alignment. When sheet piles are drivenas permanent structures, such as bulkheads,the first pile must be driven accurately,maintaining alignment throughout. Atimber-aligning frame composed of doublerows of studs, to which one or two rows ofwales and diagonal bracing are spiked, maybe required to maintain alignment, in softsoils. Normal practice is to drive the ball endof interlocking steel sheet piles to prevent soil

from being trapped and forcing theinterlock open during driving.

b. Steel sheet piles. Interlocking steel sheetpiles can be driven by one of two basicmethods.

(1) Single pile or pair of piles. In thismethod the driving leads must be keptvertical and stable, with the hammercentered over the neutral axis of the pile.This requires a firm, level foundation forthe driving equipment.

(2) Preassembled sheet piles. The pilingand wall are formed and driven along theline. The piling is set with both axesvertical. Vibration in the hammer or thepile will drive the piles out of alignment.Z-piles are driven in pairs. Single or pairsof short piles are driven to full depth in softground to prevent creep. Long piles aredriven into the ground as follows.

Set waling along the line of sheeting.

Drive a pair of sheet piles to part depth.

Set a panel of a dozen single piles or pairsin the walings.

Drive the last pile or pair in the panel partway.

Drive the piles between the first and lastpile or pairs of piles to full depth.

Drive the first pile to full depth.

Drive the last pile two-thirds its fullpenetration to act as a guide for the firstpile of the next panel.

c. Concrete sheet piles. Concrete sheetpiles are frequently placed by jetting. If awatertight wall is required, the joints aregrouted after driving is completed. The soil at

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the bottom of the pile is slushed out by a has been drawn down, an additional lengthwater jet pipe of sufficient length to reach the is usually welded on rather than attemptingbottom of the pile. A tremie is used to placegrout underwater. Flexible fillers such asbituminous material may be placed in jointsat intervals of 25 to 50 feet. If a cap is placedon the sheet pile wall, the flexible jointscontinue through the cap. In reinforcingpreviously driven sheet piles, frictional dragmay occur. To counteract this, the piles maybe bolted or welded to a stiff waling. If a pile

to jack up the pile.

4-18. Drilled piles.

Power-driven earth augers are used to drillholes to the size and depth required (figure4-24). Commercial drilling rigs are availablein a wide variety of mountings and drivingarrangements. If the holes remain open and

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dry until concreting is completed, thefoundation can be constructed rapidly andeconomically. If the walls of the hole areunstable and tend to cave in, the hole maybeadvanced using a slurry, similar to drillingmud alone or in combination with casing.

a. Slurry. Slurry is a mixture of soil,bentonite, and water which forms a heavy,viscous fluid mixed by lifting and loweringthe rotating auger in the hole. When theslurry obtains the proper consistency, thehole is advanced through the cohesionlesszone using the auger. The slurry stabilizesthe wall of the hole, preventing inflow ofgroundwater. Slurry is added at the bottom ofthe hole as depth is advanced.

b. Dry hole. If the hole is dry, the concrete isallowed to fall freely from the ground surface.The cement and aggregate may separate ifthe concrete falls against the sides of theshaft. If the diameterie small, a short, verticalguide tube is located at the center of the top ofthe shaft where the concrete is introduced.Reinforcement may be provided through acircular cage inside which the concrete canfail freely. A slump of about 6 inches issuitable under most conditions. Higherslumps are used in heavily reinforced piers.The presence of even a small amount of waterin the bottom of the shaft may reduce thestrength of the concrete. Bags of cement aresometimes laid on the bottom to absorb theexcess water before the concrete is placed.Tremied concrete can be placed in an uncasedslurry fill hole; however, refined techniquesand experienced specialist contractors aremandatory.

4-19. Shell-type piles.

In shell-type, cast-in-place concrete piles, thelight steel casing remains in the ground andis filled with concrete after it has beeninspected and has been found free of damage(figure 4-25).

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Section IV. SUPERVISION

4-20. Manpower.

The size of the pile-driving crew dependsupon a number of variables: equipmentavailable; type, length, and weight of pilesbeing driven; and driving conditions. Theminimum crew is 5 in most situations. Indriving light timber piles with a drop hammeror a crane fitted with pile-driving at-tachments, 1 person would be needed as asupervisor, 1 as a crane operator, and 3 ashelpers in handling the piles and hammer.One person should serve as an inspector,recording blow counts and penetrations. Acarpenter may be needed to cut off the piles. Alarger crew is required to drive long, steelbearing piles under hard driving conditions.If a steam hammer is used, a boiler engineerand fire fighter will be required. If anadditional crane or winch is needed to placethe piles into position, additional personnelare required. A welder may be needed to cutoff the piles at the correct elevation or to weldon additional sections. The crew may consistof 10 to 12, including supervisors and 4 or 5laborers.

4-21. Productivity.

The rate at which piles can be installeddepends upon many factors, such asequipment, length and weight of the piles,and driving conditions. A normal-sized crewcan install from 1 ½ to 5 timber bearing pilesper day (day operations) and from 3 to 6 steelsheet piles per hour. Figures for pile-drivingoperations can be established from experiencewith a particular crew, equipment, piles, anddriving conditions.

4-22. Safety.

a. Safety precautions. Standard safetyand accident prevention procedures developedfor general construction operations also apply

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to pile-driving operations. Pile driving is ahazardous operation, and adequate care mustbe taken to protect personnel from injury.

Proper individual protective equipment(shoes, gloves, helmets, and ear plugs)should be worn at all times. All equipmentguards should be maintained and in place.

Cooperation between equipmentoperators and personnel is essential toavoid accidents. Hand signals must beused during pile installation operations(figure 4-26).

Personnel must be kept clear when pilingis being hoisted into the leads and duringthe first few feet of driving. Mill scale, forexample, may be driven off a steel pileduring driving.

Operators must never stand under ornear a pile hammer. If an y adjustment is tobe made at or below a hammer, the hammershould be stopped and rested on a pile orsecured by placing the hammer-retainingpin through the pile leads. Ladders shouldbe provided on frames and leads to giveaccess to the hammer.

All equipment, particularly pile leads,must be examined frequently for any cracksor loose bolts.

Diesel pile hammers must be cleanedregularly to avoid an accumulation ofdiesel oil which may become a fire hazard.They should be fitted with a trip wire orrope so that the hammer can be stoppedfrom ground level and workers do not haveto climb ladders to operate the fuel cutoff.

The exhaust of steam hammers must becontrolled so that workers are not en-

dangered by discharges of steam orscalding water. All hoses and hoseconnections must be in good condition andproperly secured to the hammer inlet. Theend of the hose must be tied to the hammerto prevent a flying end if the connectionshould break loose.

Helmets, driving caps, anvil blocks, andother parts receiving impact must beinspected regularly for damage or fracture.Worn parts should be replaced before wearbecomes excessive, and particular caretaken to avoid wear that will develop astress concentration on a moving part.

The hammer must be kept at the bottomof the leads whenever possible.

b. Handling procedures. Creosoted timberscan cause skin bums. When creosoted pilesare driven, a fine spray is created when thehammer strikes the pile. This material on theskin should be washed off immediately withsoap and water. Cream or lotion maybe usedto protect the skin from creosote. Gogglesprotect the eyes. Hand and power tools usedto prepare piles for driving and to cut off,straighten, and align piles after they aredriven must be used safely. When it isnecessary to cut off the tops of driven piles,piledriving operations should be suspendedexcept when the cutting operations are locatedat least twice the length of the longest pilefrom the driver.

c. Water procedures. If piling is carried outover water, workers should wear life jackets.Life belts with a suitable length of cordageshould be available on the attendant floatingcraft.

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C H A P T E R 5

A L L O W A B L E L O A D S O N A S I N G L E P I L E

Section I. BASICS

5-1. Considerations.

For safe, economical pile foundations inmilitary construction, it is necessary todetermine the allowable load capacity of asingle pile under various load conditions.

5-2. Principles.

A structure is designed on pile supports if thesoil is inadequate for other types offoundations. The basic principles for pilefoundations are that they must be safeagainst breaking (bearing capacity and shearfailure) and buckling and that they must notsettle excessively or exceed the soil’s bearingcapacity. There can be other factors, such asthe need to protect a bridge pile from scour.

5-3. Requirements.

The requirements for the preliminary designof a pile foundation follow.

a. Studying soil. Obtain a soil profileresulting from subsurface explorations. Thisanalysis will determine whether the piles willbe friction (sand or clay), end bearing

(stratum of firm earth), or a combination ofboth. Local experience can be a useful guide,and sufficient laboratory test data to estimatestrength and compressibility of major strataare required.

b. Determining pile length. The mostaccurate method for determining the lengthof friction piles is to drive and load test piles.Since the time factor in a theater of operationsrarely permits driving and load testing offiction piles, lengths may be calculated fromanalysis of the soil profile. Uniformity of soilconditions will determine the number of testpiles driven at selected locations to verify thecomputed lengths. On small projects and forhasty construction, dynamic formulas maybe used to assess the allowable pile load. Ifsoil conditions are nonuniform and esti-mating pile lengths accurately is difficult, apile with an easily adjustable length (timberor steel) should be used. The driving resistancein blows per inch should be used to establishallowable loads by comparing results ofnearby piles in similar soil conditions. Fordeliberate construction, where little ex-perience is available, load tests on selectedpiles should be performed and interpreted. Aminimum of three driving tests (and more ifsubsurface conditions are erratic) should be

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performed. Record driving resistance of testpiles and all piles installed. Compare theresistances of the test piles to insure againstlocalized weak subsurface conditions.

Section II. STRUCTURAL DESIGNS

5-4. Structural capacity.

a. Allowable pile stresses. Overstress intimber piles under design loads should notexceed the values given in table 2-2. Theallowable stress in steel piles should notexceed 12,000 psi. Estimate possible re-ductions in steel cross section for corrosivelocation or provide protection from corrosion.The allowable stress in precast or cast-in-place piles should not exceed 33 percent of theconcrete cylinder strength at 28 days.

b. Driving stresses. Do not damage thepiles by overdriving. Final driving resis-tances for various pile types should be limitedto the values indicated in chapter 4.

c. Buckling failures. There is no danger ofbuckling a fully-embedded, axially-loaded,point-bearing pile of conventional dimensionsbecause of inadequate lateral support,provided it is surrounded by even the softestsoils. The ultimate load for buckling of slendersteel piles in soft clay is discussed later in thischapter. Buckling may be a problem whenpiles project appreciably above groundsurfaces. In such cases, the unsupportedlengths of the pile should be used in column-stress formulas to determine the safe loadcapacity. The unsupported length, 1“, iscomputed assuming the pile is laterallysupported at 10 feet below ground surface insoft soils and 5 feet in sands and firm soils.This laterally supported point is commonlyreferred to as a fixed point (see figure 5-l).

d. Lateral loads. Lateral forces on embeddedpiles may produce high bending stresses anddeflections. The behavior of short, rigid piles

under lateral loads is discussed later in thischapter. The behavior of relatively flexiblepiles extending appreciably above groundsurfaces and subjected to lateral loads isbeyond the scope of this manual.

5-5. Column-stress formulas.

a. Slenderness ratio.

(1) Timber piles. The slenderness ratio(lu/d) is the ratio of the effective un-

supported length (1u) to the average pilediameter (d). The average pile diameter ismeasured at a point one-third the distancefrom the butt of the pile. For the effectiveunsupported length of a single row of pilesunbraced in the longitudinal direction, lu is0.7 of the distance from the fixed point tothe top of the piles, as shown in figure 5-1.For a single row of piles adequately bracedin the longitudinal direction, lu is one-halfthe distance from the fixed point to thelowest bracing. For piles arranged in twoor more rows and adequately bracedbetween rows, the unbraced length is one.half the fixed point to the lowest bracing asshown in figure 5-1. If the ratio (lu/d) is lessthan 11, then a buckling capacity need notbe determined. If the ratio exceeds a valueof 11, the buckling capacity must bedetermined. To avoid use of extremelyslender piles, the value of lu/d should notexceed 40. When the slenderness ratio isless than 11, the allowable load is based ontable 2-2. When the slenderness ratioexceeds a value of 11, the allowableconcentric axial load is computed as thelesser of the following.

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(2) Steel piles. The slenderness ratio ofsteel piles is the ratio of the unsupportedlength (1.) as described to the least radiusof gyration(r). Tables and formulas for theradius of gyration are given in TM 5-312.The buckling capacity of steel piles mustalways be determined regardless of thenumerical value of lu/r. For the most econom-ical design, the value of lu/r should notexceed 120. For steel piles the allowablebuckling load is calculated as follows.

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Section III. DYNAMIC FORMULAS

5-6. Concept.

Dynamic pile formulas are based on thetheory that the allowable load on a pile isclosely related to the resistance encounteredduring driving. The concept assumes that thesoil resistance remains constant during andafter driving operations. This may be true forcoarse-grained soils, but may be in error forfine-grained soils because of the reduction instrength due to remolding caused by piledriving. The formula of principal use to themilitary engineer is the Engineering Newsformula.

5-7. Engineering News formula

The allowable load on a pile may be estimatedby one of the following versions of theEngineering News formula.

piles driven with a double-acting air orsteam hammer or closed-ended dieselhammer.

5-8. Pile set.

To determine the pile set, attach a piece ofheavy paper to the pile at a convenient height(figure 5-2). Place a straightedge close to thepaper supported by stakes spaced two feet oneach side of the pile. Draw a pencil steadily

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across the straightedge while striking the 5-9. Application.pile with a series of blows. This trace will.show the set of net penetration of the pile for agiven blow of the hammer. For example,assume that a timber pile is driven by an1,800-pound drop hammer with a height offall equal to 6 feet. During the last 6 inches ofdriving, the average pile set is measured andfound to be 0.25 inch. Using the EngineeringNews formula applicable to drop hammers,the allowable load is computed as follows.

Qall= 2 x 1,800x6 = 17,280 pounds or 8.6 tons0.25 + 1

The Engineering News formula providesconservative values in some cases and unsafevalues in other cases. Reasonably reliableresults are obtained for piles in coarse-grainedsoils. Generally, when time is available andthe cost is justified, pile load tests should beused in conjunction with the dynamicformulas for estimating allowable pile loads.Using only the dynamic formula should berestricted to hasty construction and to projectswhere the cost of load testing would be toohigh in relation to the total cost of piles.

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Dynamic formulas are useful in correlatingpenetration resistance obtained from localexperience and in relating the results of loadtests to the behavior of piles actually driven.

a. Saturated fine sands. In saturated finesands, the formula usually indicates theallowable load as being less than that whichmay develop after driving. If time is available,a friction pile that has not developed itsrequired load should be rested for at least 24hours. The capacity may then be checkedwith at least 10 blows from a drop hammer or30 blows with a steam, pneumatic, or dieselhammer. If the average penetration is lessthan that required by the formula to give theneeded bearing capacity, piles do not requiresplicing or deeper driving. If the requiredcapacity is not developed after the rest period,the piles must be spliced or additional pilesdriven, if the design of the foundation permits.

b. Jetting. The formulas do not apply topiles driven by the aid of jetting unless thepile is permitted to rest after jetting and thendriven to final position without jetting. Datafrom the final driving may be used in thedynamic formula after resting the pile. Theformulas do not apply to end-bearing pilesdriven to rock or other firm strata.

Section IV. STATIC FORMULAS

5-10. Driven piles.

Static pile formulas are based on the shearstrength of the foundation soils. Theseformulas compute the ultimate bearingcapacity and allowable load. Static pileformulas apply to piles in clay (figure 5-3) andto piles completely or partially embedded incohesionless soil (figure 5-4). The shearstrength must be determined from laboratorytests on undisturbed samples or estimatedfrom correlations with the standard pene

tration test. The latter method is generallymore reliable for cohesionless soils. Typicalvalues of the undrained shear strength ofcohesive soils are shown in table 5-1. Theultimate capacity of piles in cohesionlesssoils is influenced by the position of thegroundwater table. Depending on the cer-tainty with which subsoil conditions areknown, the ultimate bearing capacity shouldbe divided by a factor of safety from 1.5 to 2.0to obtain the allowable load. For a givenallowable load, the static formulas (figures5-3, 5-4) also determine the required length ofpiles, the pullout capacities of piles, and theultimate load buckle of slender steel piles insoft clay.

5-11. Drilled piles.

The allowable load on drilled piles is based onsoils shear strength data and from formulassimilar to those for driven piles. In clays, theaverage undisturbed shear strength over thedepth of the pile should be multiplied by anempirical earth pressure coefficient, Kc,varying from 0.35 to 0.75 to account forsoftening. If the hole is allowed to remainopen for more than a day or two or if a slurryis used during construction, the lower valuesshould be used. In sands, the coefficient ofearth pressure, Kc, should be taken as 1.0.The allowable end-bearing capacity, Qd,, canalso be computed using the standardpenetration test results in terms of N blowsper foot.

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Section V. PILE LOAD TESTS

5-12. Equipment.

Load tests determine the allowable load, thesettlement under working load, or thesoundness of a pile. Load tests may beconducted in compression or tension. Lateralload tests are seldom justified. The followingconsiderations must be made.

The test piles should be of the same typeand driven by the same equipment as forconstruction.

Test loading should not be initiated lessthan 24 hours after driving piles incohesionless soils and not less than 7 daysin cohesive soils.

The load is usually applied by a hydraulicjack reacting against dead weights oragainst a yoke fastened to a pair of anchorpiles (figure 5-5). Anchor piles should beatleast 5 test pile diameters from the test pile.

The test load should be twice the proposeddesign load as estimated from the dynamicformula, static formula, or other means.

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Readings of settlement and reboundsshould be referred to a deep benchmarkand recorded to 0.001 feet.

5-13. Procedures.

The loading procedure may be carried outeither by the continuous load method or theconstant rate of penetration (CRP) method.

a. Continuous load. The load is applied inseven increments, equal to ½, ¾, 1, 1¼, 1 ½,1¾, and 2 times the allowable load assumedfor design. The load is maintained constantat each increment until there is no settlement

in a 2 hour period. The total test load shouldremain in place until settlement does notexceed 0.002 feet in 48 hours. The total loadshould be removed in decrements not ex-ceeding one fourth of the total test load withintervals of not less than one hour. Therebound should be recorded after eachdecrement is removed. A curve may then beprepared showing the relationship betweenthe load and deflection (figure 5-6). Thisprocedure is most reliable where it is nec-essary to estimate the settlement of pilesunder the design load. The allowable load istaken as one half that which caused a netsettlement of not more than ½ inch or gross

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settlement of 1 inch, whichever is less. Thecontinuous load method is rarely justified inmilitary construction because of the excessivetime requirements.

b. Constant rate of penetration. The pileis jacked into the ground at a constant rate,and a continuous record of the load anddeformation is taken. The test proceedsrapidly and requires the services of severalobservers. Results of the test are not toosensitive to the rate of penetration. The loadis increased until the pile fails by plunging orthe capacity of the equipment is reached.Results of the test are plotted (figure 5-7). Theallowable load is considered to be 50 percentof the ultimate bearing capacity defined bythe intersection of lines drawn tangent to thetwo basic portions of the load settlementcurve. The constant penetration rate method,a very rapid test, is particularly suited formilitary construction.

6-14. Bearing stratum resistance.

Where piles are driven through compressiblesoil strata into a bearing stratum of sand orother firm material, the allowable pile load isbased on the carrying capacity of the bearingstratum without depending on the short-termfrictional resistance of the compressible soils(figure 5-4). With pile load tests, it is generallynot possible to distinguish between the short-term carrying capacity of the compressiblesoil and the long-term carrying capacity ofthe bearing stratum. The capacity of thebearing stratum can be obtained by testingthe pile inside the hollow casing or by makinga load test on two piles driven about 5 feetapart. One pile is driven to refusal in thebearing stratum while the other is driven towithin 3 feet of the bearing stratum. Thedifference in the ultimate loads for the twopiles is equal to the carrying capacity of thebearing stratum.

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5-15. Limitations of pile load tests. deep enough to sustain vertical loads will

Pile load tests do not take into account theeffects of group action on bearing capacityunless a group of piles is loaded. Thesettlement of a pile group is not generallyrelated to the settlement recorded during aload test on a single pile. Settlement must beestimated as discussed in chapter 6 fromconsideration of soil compressibility withinthe zone of the influence (figure 5-6).

5-16. Lateral loads resistance.

a. Lateral loads. Vertical piles supportingstructures are subjected to lateral forces. Forexample, a pile bent supporting a highwaybridge may be subjected to the forces of wind,current, ice, and the impact of floating objects.Similar forces may act on waterfrontstructures, such as wharves and piers.Properly designed bracing, supplemented bybatter piles and fenders, will usually providethe structure with sufficient stability to resistlateral loads. The piles must be driven deepenough to prevent the structure fromoverturning. Normally, vertical piles driven

develop enough lateral resistance to preventthe structure founded on a number of pilesfrom overturning. An exception to this couldbe a bridge foundation in an area subject toscour during periods of high water. Whenpiles are subjected to lateral loads in excess of1,000 pounds per pile, it is usually moreeconomical and desirable to provide batterpiles. Lateral loads apply to both rigid andflexible piles (figure 5-9).

b. Flexible and rigid piles. It is difficult toestimate the resistance provided by a singlevertical pile (or group of piles) to lateralforces. The best method is to conduct fieldloading tests. If time and facilities for this arelacking, the embedment or lateral capacitymay be estimated by the use of charts (figures5-10, 5-11) that apply to fixed-end and free-head short, rigid piles. The effect of groupaction is ignored in these charts. For thefixed-head pile, failure occurs when the pilemoves as a unit through the soil. For the free-head pile, failure occurs when the pile rotatesas a unit through the soil around a pointlocated below the ground surface. Theoretical

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analysis has been developed and is availablefor laterally loaded piles in which theflexibility of the pile is considered.

(1) Rigid piles in clay. Figure 5-10 showsthe relationship between the ultimatelateral resistance and length of embedmentfor fixed-end and free-head piles in claysoils in terms of the undrained shearstrength (table 5-l). As the shear strengthof the soil near ground surface depends onseasonal variations in water content, it isgood practice to reduce laboratory valuesby one-third to one-fourth. A safety factorfrom 1.5 to 2.0 should be applied to the

design lateral load to compute the ultimatelateral resistance. Continuous lateral loadsshould be resisted by batter piles.

(2) Rigid piles in sand. Figure 5-11 showsthe relationship between the ultimatelateral resistance and length of embedmentfor fixed-end and free-head piles in sandsin terms of coefficient of passive earthpressure, Kp, assumed equal to 3.0regardless of the density of the sand. Safetyfactors from 1.5 to 2.0 should be applied tothe design lateral load to compute theultimate lateral resistance.

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C H A P T E R 6

P I L E F O U N D A T I O N S

Section I. GROUP BEHAVIOR

6-1. Group action. Piles are most effectivewhen combined in groups or clusters.Combining piles in a group complicatesanalysis since the characteristics of a singlepile are no longer valid due to the interactionsof the other group piles. The allowable load ofa single pile will not be the same when thatpile is combined in a cluster or in a group.There is no simple relationship between thecharacteristics of a single isolated pile andthose of a group. Relationships depend on thesize and other features of the group and onthe nature and sequence of the soil strata.The ultimate bearing capacity of a group ofpiles is not necessarily equal to the ultimatebearing capacity of a single isolated pilemultiplied by the number of piles in thegroup.

Only in certain cases (for example wherethe group compacts the soil) will theultimate bearing capacity of the group begreater than the number of piles times theultimate bearing capacity.

For end-bearing piles on rock or incompact sand or gravel with equally strongmaterial beneath, the ultimate bearing

capacity of the group will be essentiallyequal to the number of piles times theultimate bearing capacity.

For piles which rely on skin friction in adeep bed of cohesive material, the ultimatebearing capacity of a large group maybesubstantially less than the number of pilestimes the ultimate bearing capacity.

6-2. Driving.

a. Effects on the soil. When piles areinstalled in groups, consideration should begiven to their effects on the soil. Heave andlateral displacement of the soil should belimited by the choice of a suitable type of pileand by appropriate spacing. Some soil,particularly loose sands, will be compactedby displacement piles. Piles should beinstalled in a sequence which avoids creatinga compacted block of ground into whichadditional piles cannot be driven. Similardriving difficulties may be experienced wherea stiff clay or compacted sand and gravelhave to be penetrated to reach the bearingstratum. This may be overcome by firstdriving the center piles of a group andworking outwards, but it is frequently moreconvenient to begin at a selected edge and

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work across the group. In extreme cases, itmay be necessary to predrill through a hardupper stratum. If the group is confined bysheet piling which has already been driven, itmay be preferable to drive from the perimeterinward to avoid displacemer of the sheetpiling.

b. Effects on adjacent structures. Whenpiles are to be driven for a new foundationalongside an existing structure, care must betaken to insure that the existing structure isnot damaged by the operation. Settlement orheave caused by pile driving may seriouslydamage the foundations of nearby structures.For example, piles driven behind a retainingwall can increase the pressure on the wall.This increase in pressure maybe caused bydensfication of a granular soil by vibration,or a plastic soil may actually be forced againstthe wall. To avoid or minimize the effects ofvibration, the pile may be driven in apredrilled hole or jetted or jacked into place.The jetting itself could have a detrimentaleffect upon the soil beneath an existingstructure.

6-3. Spacing.

Piles should be spaced in relationship to thenature of the ground, their behavior in groups.and the overall cost of the foundation. Thespacing should be chosen with regard to theresulting heave or compaction. Spacingshould be wide enough for all piles installedto the correct penetration without damagingadjacent construction or the piles themselves.For piles founded on rock, the minimumcenter-to-center spacing is 2 times the averagepile diameter, or 1.75 times the diagonaldimension of the pile cross section, but notless than 24 inches. An optimum spacing of3 times the diameter of the pile is often used.This allows both adequate room for drivingand economical design of the pile cap.

Section II. GROUND CONDITIONS

6-4. Rock.

Site investigation should establish whetherthe underlying rock surface is level, inclined,or irregular. It should also determine thethickness of decomposed rock which the pileshould penetrate. If the surface is inclined,driven piles may have to be pointed. Theupper load limit of a pointed pile embedded insound rock may be the allowable compressivestress of the material in the pile. If theoverlying material is saturated plastic clay,displacement piles and consequent volumechanges may heave piles already driven.

6-5. Cohesionless soils.

a. Piles driven into dense sand. Piles aredriven through the soft materials and into adense, deep stratum of sand to developadequate carrying capacity. If the sand ismoderately loose, the required penetrationmay be deep. If the sand is dense, penetrationmay be only a few feet. Skin friction ofcompressible soil is not considered since itwill disappear in a period of time. The entireload will then be carried by the firm stratum(figure 5-3).

(1) Point resistance. Point resistance canbe found using calculations and laboratorytests (chapter 5, section IV). It can also bedetermined approximately by making aload test on two piles driven about 5 feetapart. One pile is driven to refusal in thefirm bearing stratum while the other isdriven until its point is 3 feet above thesurface of the bearing stratum. If bothpiles are loaded at equal rates, the effect oftime on skin friction can be eliminated.The point resistance is equal to thedifference between the ultimate bearingcapacities of the two piles.

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(2) Depth estimate. The depth to whichpiles must extend into the sand can beestimated on the basis of driving testscombined with load tests or, in the case ofsmall projects, calculations using dynamicor static formulas.

b. Compaction piles. Compaction pilesdensify the sand. The design load forcompaction piles is conservative. The pilesare driven to equal penetration with eachhammer stroke. The hammer strokes wil1 beprogressively shorter as work continuesbecause the sand becomes more compactedby driving the preceding pile. Drivingresistance increases as each pile is drivenbecause of the compaction of the soil.

(1) Driving loads. On small jobs, loads of20 tons are usually assigned to compactionpiles of timber and 30 tons to precastconcrete. The piles should be driven to thecapacities indicated by the EngineeringNews formula (chapter 5, section III). Onlarge jobs, a test group of several pilesshould be driven. The center pile should bedriven first to a capacity indicated by theEngineering News formula. When theentire group of piles has been driven, thecenter pile should be redriven, and itscapacity determined by the formula. Thedifference between the 2 computedcapacities reflects the effects of densi-fication. A load test on the center pile afterredriving may be used to check the ac-curacy of the computed capacity.

(2) Length. The length of compaction pilesdecreases markedly with increasing taper.Piles from 20-ton to 30-ton capacity havinga taper of 1 inch to 2 ½ feet can seldom bedriven more than 25 feet in loose sands.

c. Piles for preventing scour. Scour, whichresults from currents, floods, or ship-propelleraction, will significantly reduce the func-tional resistance of a pile. The bases of bridge

piers located near river channels must beestablished below the level to which the riverbottom is removed by scour during floods. Inmany cases, the depth of the river increasesfaster during floods than the crest rises. Asbridges are located where the channel isnarrow, the depth of scour is likely to begreater than average. Furthermore, theconstruction of the bridge usually causesadditional constriction of the channel anditself increases the depth of scour. Depths ofscour can be as much as 4 feet for each 1 footof rise. For military construction, a reason-able design estimate is a depth of scour equalto 1 foot for each foot of rise of the water.Scour can be minimized by surrounding thepile foundation with sheet piles or providingriprap protection around the base of the pier(refer to TM 5-312).

d. Group behavior. The ultimate bearingcapacity of pile groups in cohesionless soil isequal to the number of piles times the ultimatebearing capacity of an individual pile,provided the pile spacing is not less thanthree pile diameters. A pile group incohesionless soil settles more than anindividual pile under the same load (figure6-l). Ordinarily, driving to a resistance of20 tons for timber piles or 30 tons for concretepiles as determined by the Engineering Newsformula will insure that settlements arewithin tolerable limits. Piles driven into athick bearing stratum of dense, cohesionlessmaterials should not settle provided correctsafety and engineering analysis have beenfollowed.

e. Uplift resistance. The total upliftresistance of a pile group is the smaller of thefollowing.

The uplift resistance of a single pile timesthe number of piles in the group.

The uplift capacity of the entire pilegroup as a block (figure 6-2), which is the

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sum of the weight of the pile cap, theweight of the block of soil (using buoyantweights below the water table), and thefrictional resistance along the perimeter ofthe block.

f. Driving. The driving resistance of sandsdoes not indicate the true resistance of thepile. If the sands are loose, pore pressuresallow the piles to penetrate with littleresistance. However, with time these porepressures will dissipate; and redriving orsubsequent load tests will indicate a greatersoil resistance. If the materials are dense,initial driving may cause negative porepressure, making driving hard. As thesepressures dissipate, both resistance and loadvalues lower. Redrive tests should beperformed when excessively high or lowdriving resistances are encountered.

6-6. clay.

a. Group action. Piles driven in clay derivetheir capacity from friction. They arecommonly driven in groups or clustersbeneath individual footings or as single largegroups beneath mats or rafts. The bearingcapacity of a pile cluster maybe equal to thenumber of piles times the bearing capacityper pile, or it may be much smaller because ofblock failure (figure 6-3). The load on a groupof piles may be sufficient to cause blockfailure. Block failure generally can beeliminated if the pile spacing is equal to orgreater than three pile diameters.

b. Settlement. The need to limit settlementwill govern design of piles in clay. Proceduresfor computing foundation settlement arepresented in TM 5-545. Stress distribution

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requirements may be found by analyzing the piles is generally small, and thereforesettlement of pile groups (figure 6-4). The alternate types of shallow foundations shouldreduction in settlement provided by friction be considered in lieu of friction piles.

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Settlement of a group of friction piles willtend to increase as the number of piles in thegroup increases. Efficiency factors can beused to calculate how to reduce the allowableload to compensate for settlement. For pilesspaced wider than three pile diameters, thereduced group capacity can be found bymultiplying the sum of the individualcapacities times the ultimate bearing capacitytimes an efficiency factor which varies from0.7 for a spacing of three pile diameters to 1for eight pile diameters. Alternatively, thepile groups are proportioned on the basis ofcomputed settlements.

c. Uplift resistance. The resistance to upliftof pile groups in clay is governed by the sameconsiderations that apply to uplift resistanceof pile groups in sand.

d. Driving. Clay soils are relatively in-compressible under the action of pile driving.

Hence, a volume of soil eaual to that of thepile usually will be displaced (figure 6-5). Thiswill cause ground heave between and aroundthe piles.

Driving a pile alongside those previouslydriven frequently will cause those alreadyin place to heave upward.

In the case of piles driven through a claystratum to firm bearing beneath, the heavemay be sufficient to destroy the contactbetween the tip of the pile and the firmstratum. This may be detected by takinglevel readings on the tops of piles previously placed. Raised piles should beredriven to firm bearing.

The displacement of soil by the pile maycause sufficient lateral force to movepreviously driven piles out of line ordamage the shells of cast-in-place concrete

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piles of the shell-less type. This problemmay be solved by predrilling.

6-7. Negative friction (down drag).

a. Cohesive soils. After a pile is installedthrough a stratum of cohesive soil, thedownward movement of the consolidatingand overlying soils will cause a drag on thepile. The consolidation may be caused by theweight of the deposit, by the imposition of asurcharge such as a fill, or by remoldingduring pile installation. The downward dragmay cause excessive settlement. Coating thepile with a bitumen compound will reducedrag. The magnitude of the drag per unit ofarea cannot exceed the undrained shearingstrength of the compressible soil (table 5-l).The drag acts on the vertical surface area ofthe entire pile foundation. Methods ofanalysis for drag on piles in clay areillustrated in figure 6-6.

b. Sensitive clays. When piles are driventhrough sensitive clay, the resultingremolding may restart the consolidationprocess. The downward force due to negativefriction may then be estimated by multiplyingthe cohesion of the remolded clay by thesurface area of the pile shaft. Particular careshould be given to the design of friction pilefoundations if the soil is sensitive. In suchcircumstances it maybe preferable not to usepiles.

c. Design allowance. If drag will develop,the point resistance of the piles should beevaluated separately by means of analysis orload tests. The drag load should be added tothe load earned by the bearing stratum.When drag causes an overload, the allowableload may be reduced by 15 percent if a safetyfactor from 2.5 to 3 is provided for the workingload.

6-8. Permafrost.

a. Suitability. Piles are extremelysatisfactory as foundations in arctic regions.Their use is discussed in detail in TM 5-349.Since the bearing value of frozen ground ishigh, piles in permafrost will support atremendous load. However, because freezingof the active zone creates uplift, piles maybeinstalled at least twice as deep as the thick-ness of the active zone. To reduce uplift, pilesare installed butt down. Loads are not placedon piling until the permafrost has had achance to refreeze, unless the normal skinfiction and bearing will support the load.

b. Allowable load. The allowable load canbe determined as follows.

Immediately after construction (figure6-7, 1).

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c. Spacing. A minimum spacing of 6 feet is d. Installation seasons. The best season toused if the piles are placed in holes thawed by install piles in the arctic is autumn, as soona steam or water jet. Normal design should as the ground surface has frozen sufficientlyspace piles 10 to 14 feet apart. For very heavy to support equipment. If working conditionsconstruction, excellent results have been permit, winter is an equally good season.obtained by using 8-inch diameter, standard-weight steel pipes, placed in holes drilledwithout steam or water jetting, and spaced6 feet center-to-center.

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Section III. DESIGN EXAMPLES

6-9. Point-bearing piles in sand.

a. Task. Design a pile structure for soft soilsover a thick stratum of sand. Determine thenumber of 15-inch timber piles required tosupport an isolated column footing whichcarries a vertical load of 180 tons, includingthe weight of the pile cap.

b. Conditions. The soil consists of 10 feet ofsoft organic clay underlain by sands. Thegroundwater table is at ground surface. Thesubmerged unit weights of the clay and sandsare 40 and 62 pounds per cubic foot re-spectively. A split spoon boring indicatesthat the penetration resistance of the sand is30 blows per foot. A test pile has been driventhrough the organic clay, penetrating 5 feetinto the sand. Time is not available toperform a pile load test.

c. Dynamic formula. A 3,000-pound hammerwith a drop of 6 feet is used to drive the testpile. The average penetration of the pileduring the last 6 blows of the hammer is 0.25inch. Using the Engineering News formulaapplicable for drop hammers, the estimatedallowable load for the pile is as follows.

d. Static formula. The allowable load on asingle pile also maybe estimated by means ofthe static formula (figure 5-4, 2). Based on thepenetration resistance of 30 blows per foot,the sand stratum can be assumed to be in amedium dense condition with an angle ofinternal friction of 36 degrees. FS=factor of safety

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e. Allowable load and spacing. Both thedynamic and static formulas indicate that anallowable load of 15 tons per pile is reason-able. The number of piles required to supportthe load is 180/15 = 12 piles. As the piles arefounded in sand, no reduction for groupaction is necessary. The piles should bespaced 3 feet (three times the pile diameter)center-to-center and could be arranged in 3rows of 4 piles each. Piles should be 17 feetlong, providing an additional 2 feet requiredfor embedment and for differences in drivingresistances. If a concrete cap is used,allowance must be made for embedment ofpiles into the cap.

6-10. Point-bearing piles in sands withdeep clay stratum.

a. Task. Design a pile structure for soft soilsover a thick stratum of sand. Determine thenumber of 15-inch timber piles required tosupport a load of 180 tons including theweight of the pile cap.

b. Conditions. Foundation conditions aresimilar to those in paragraph 6-9 except thatthe sand stratum is of limited thickness andunderlain by clay. The soil profile andavailable soils data are shown in figure 6-8.

c. Allowable load. The allowable load perpile, based on either the dynamic or staticformula, is determined to be 15 tons, as notedin paragraph 6-9.

d. Settlement. The clay layer underlyingthe sand stratum could result in undesirablesettlement of the pile foundation. Settlementcaused by consolidation is a matter of concernif the structure is not temporary. Con-solidation settlement can be estimated usingthe stress distribution based on figure 6-4 andthe approximate method of settlementanalysis explained in TM 5-545.

(1) Basic equation. The basic equation forsettlement due to consolidation of a

6-12

normally loaded clay of low sensitivity isas follows.

(2) Pressure calculations. .All pressurecalculations will be referred to the center ofthe clay layer (elevation 268).

where:

PO = existing overburden pressure

For simplicity, it is assumed that the pilesare arranged in a square pattern of 4 x 4.The increase in pressure,by assuming that the load is spread atangle of 2 vertical to 1 horizontal, startingat the lower third point of the pile embed-ment in sands.

is obtained

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(3) Settlemet formula. Estimated set-tlement as follows.

(4) Settlement estimate. The settlementmay now be estimated as follows.

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(5) Other considerations. This foundationmay be expected to settle approximately4 inches. Settlement may be reducedslightly by increasing the spacing betweenthe piles. An increase in pile spacing abovefour times the pile diameter frequentlyresults in uneconomical design of the pilecap. If this amount of settlement is exces-sive, longer timber piles may be driventhrough the sand and clay to bedrock.Jetting may be necessary to get the pilesthrough the sand layer. If this is done, theload on each pile maybe increased to 20tons or more, and the number of piles maybe reduced from 16 to 9. Piles 42 feet longwill be required.

6-11. Friction piles in clay.

a. Task. Design a pile foundation in alocation where borings indicate a uniformclay deposit to a depth of 80 feet (figure 6-9).Determine the number of 12-inch timber piles(readily available in 45 foot lengths) requiredto support a load of 120 tons.

b. Conditions. The clay is medium stiff,with an average unconfined shear strengthof 600 pounds per square foot (0.3 tons persquare foot). The allowable load on a singlepile may be estimated by using the soil testresults and other information (figure 5-3).Time is not available to perform a pile loadtest.

c. Required embedment. The ultimate loadon a single pile using the analysis shown infigure 5-3 is as follows.

Based on a safety factor of 2.0, the requiredembedment to provide an allowable load perpile of 20 tons is as follows.

d. Pile spacing and group action. If thepiles are arranged in 3 rows of 3 piles eachwith a spacing of 3 feet 6 inches, center-to-center, the pile group can carry a gross load of9 (20) = 180 tons. To accommodate the largersettlement expected from a group of pilescompared to a single pile, the capacity shouldbe multiplied by an efficiency factor, E, which(as previously noted) is equal to 0.7 for a pilespacing of 3 pile diameters. Thus, the groupcapacity corrected for settlement to 0.7 x 180tons (126 tons) is a value greater than theactual load of 120 tons.

e. Block failure. To check for block failure(figure 6-3) the bearing capacity of the pilegroup is computed as follows.

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With a safety factor of 3, the allowable loadon the pile group is 595/3 = 198 tons. Sincethis is greater than the load which the groupwill carry (120 tons), the design is satisfactoryfrom the standpoint of block failure.

f. Settlement. The settlement of the pilegroup may be estimated using the approxi-mate method described in paragraph 6-10,assuming that the pile loads are applied on aplane located one-third of the length of thepiles above their tips. Using the data shownin figure 6-9, the following calculations aremade with pressures calculated at elevation125.

Assuming that a long-term settlement of3 inches is acceptable, the design is consideredsatisfactory. If the computed settlement isexcessive, the amount could be reduced byusing greater pile spacings or longer piles. Itshould be noted that long-term settlementsexceeding 1 inch can cause serious problemsfor rigid structures. This is particularly truewhen differential settlements occur.

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C H A P T E R 7

D I S T R I B U T I O N O F L O A D S O N P I L E G R O U P S

Section I. DESIGN LOADS

7-1. Basic design.

The load carried by an individual pile orgroup of piles in a foundation depends uponthe structure concerned and the loads carried.Under normal circumstances, pile foun-dations are designed to support the entiredead load of the structure plus an appropriateportion of the live load.

7-2. Horizontal loads.

Determining horizontal loads acting on pilesused for bridge supports is of particularimportance in military construction. Pileswhich support bridges crossing rivers areoften subjected to a variety of horizontalloads.

Pressure of flowing water.

Forces of ice.

Impact of floating objects.

Effects of wind on the substructure andsuperstructure.

Methods of computing these loads aredescribed in TM 5-312.

Section II. VERTICAL PILE GROUPS

7-3 Distribution of vertical loads.

a. Resultant at center of gravity. Pilesunder a structure act as a group intransmitting the loads to the soil. Thedistribution of loads to the individual pilesdepends upon the amount of vertical andhorizontal movement at the base of thestructure and the amount of rotationalmovement about some center. If the base ofstructure is rigid and the piles are all vertical,a vertical load (or several vertical loads)applied at the center of gravity of the pilegroup will be distributed equally to all thepiles. Thus, assuming that the resultant (R)of all vertical loads passes through the centerof gravity of the pile group (figure 7-l), theload (Pv) on each pile is given by the followingformula.

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n = number of piles in pile groupb. Resultant not at center of gravity. If

where the resultant of all the vertical loads actingon a pile group does not pass through the

R = resultant of all vertical loads center of gravity of the pile group, thedistribution of the loads to the individual

= load acting on each pile piles is indeterminate. Discussion of the

= summation of all vertical loadsapproximate method for determining thedistribution of loads follows. This method

acting on pile group should be suitable for military applications.

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7-4. Calculating distribution of loads. where:

Before approximate methods are used for Pv = vertical load on any pilevertical pile foundations, it is important toknow the limitations involved. The ap- = resultant of all vertical loads onproximate methods disregard the charac-teristics of the soil and piles and the restraint

pile group

of the embedded pile head. For vertical pilefoundations where the soil and piles offer

n= number of piles

great resistance to movement, approximatemethods give results equivalent to those

ex = distance from point of

obtained by more refined methods.

a. Resultant eccentric about one axis.(See figures 7-1, 7-2.) If the resultant (R =is eccentric only about one axis, the Y-Yaxis,the load on any pile (Pv) is given by thefollowing formula.

intersection of resultant withplane of base of structure to

cx =

Y- Yaxis

distance from Y - Y axis to pilefor which Pv is being calculated

moment of inertia of pile groupabout Y - Y axis with each pileconsidered to have an areaof unity

Iy =

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b. Resultant eccentric about two axes. Ifthe resultant is eccentric about both the Xand Y axes, the load on any pile (Pv) is givenby the following formula.

where

= distance from point ofintersection of resultant withplane of base of structure toX-xaxis

= distance from X - X axis to pilefor which P, is being calculated

= moment of inertia of pile groupabout X - X axis

c. Moment of inertia of pile group. Themoment of inertia of a pile group about eitherthe X-X or Y-Y axis (figure 7-2) can becalculated by the following formula.

(n2 - 1) (number of rows)

where

Ap= the area of one pile, assumed tobe equal to 1

S = pile spacing in feet

n = number of piles in each row

Since Ap equals 1, if there are four piles perrow and two rows (figure 7-2), the moment ofinertia about the Y-Y axis is given by thefollowing formula.

7-4

12

Iy= S2 (4) (42 -1)(2 rows)12

Iy =10 S2

If there are two piles per row and four rows,the moment of inertia (Ix) is given by thefollowing formula.

Ix = S2 (2) (22 -1)(4 rows)

Ix = S2

d. Example.

(1) Task. Calculate the load acting on eachpile if the resultant of gravity of the pile group, X = 0 feet.Calculate the load acting on each pile if the

acts at a distance X=-4 feet.

(2) Conditions. Assume that the bent (figure7-3) is subjected to a loadincluding both dead and live loads. Assumethat the resultant of the vertical loadsacts at a position -X feet to the right of thecenter of gravity of the bent. Distances tothe left are plus and distances to the rightare minus.

(3) Solution. If the resultant acts at thecenter of gravity of the pile group, the loadacting on each pile is the same and is givenas follows.

If the resultant acts 4 feet to the right of thecenter of the gravity of the bent, the loadacting on each pile can be computed fromthe following formula.

acts at the center

resultant

of 135 tons

FM 5-134

ex= -4 feet (center of gravity of the

pile group to the point ofapplication of the resultant)

where:The moment of inertia J can be computed asfollows.

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(4) Tabulations. The remaining computationcan be tabulated as shown in table 7-1. Theloads on these piles vary from 3 tons for pileone to 27 tons for pile nine. To check this pilefoundation, the allowable load of each pileshould be calculated by the procedures estab-lished in chapter 5.

Section III. VERTICAL AND BATTERPILE GROUPS

7-5. Load distribution from structure topiles.

where

Substituting these values of n, ex, and Iyinto the above equation gives thefollowing.

where:

cx = the distance in feet from thecenter of gravity of the pilegroup to the pile for which P, isbeing calculated. (The value ofCX can be either plus or minusaccording to the establishedsign convention.)

7-6

Batter piles are used in a pile group to absorball or part of the horizontal loads when thegroup is unstable with only vertical piles. Pilegroups that consist of a combination ofvertical and batter piles are indeterminateexcept where the piles are symmetrical aboutthe transverse and longitudinal axis of thefoundation. In this case, a vertical loadapplied at the center of the pile group will bedistributed equally to all piles.

7-6. Determining distribution of loadsto groups containing batter piles.

a. Limitations. A method similar to that forvertical pile groups is also used for de-termining the load distribution on verticaland batter piles. This method has limitedaccuracy and should be used only in hastyconstruction in a theater of operations.Computed values are used in permanentstructures or structures which must carryheavy loads.

b. Application. In applying the approximatemethod, the load imposed on each verticaland batter pile is assumed to act in thedirection of the pile (figure 7-4).

Calculate the vertical component of load, Pv,on each pile as follows.

FM 5-134

where:

= resultant of vertical loads on apile group

n = number piles

= summation of all momentsabout the center of gravity ofpile group at the level of pilefixity due to XV and(figure 7-4)

c x = distance from center of gravityof pile group to pile for whichPv is being calculated

Iy = moment of inertia of pile group

The relationship between the vertical andhorizontal load components and resultantaxial pile load is shown in figure 7-5. Calculatethe horizontal and axial components asfollows.

where

Ph = horizontal component ofpile load

Pa = axial component of pile load

x = coefficient of horizontal batter

y = coefficient of vertical batter

= angle (in degrees) of the batter

The horizontal component of axial loads onthe batter pile is assumed to add to or resistthe horizontal thrust depending upon thedirection of batter. The horizontal load onany pile is the algebraic difference betweenthe resultant horizontal load and thesummation of the horizontal components ofaxial loads on the batter piles divided by thenumber of piles.

The vertical, horizontal, and axial com-ponents (figure 7-4) may be represented by aforce polygon (figure 7-6). The batter pileshave reduced the’ magnitude of the totalhorizontal load from as follows.

These operations can be interpretedgraphically or computed mathematically.After constructing the force diagram orcomputing the lateral loads and bendingstresses on each pile, the loads are checked todetermine if they are less than the allowablelateral resistance and bending stresses.

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7=8

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7-9

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C H A P T E R 8

M A I N T E N A N C E A N D

Section I. TIMBER PILES

8-1. Damage and deterioration.

Both untreated and treated piles are subjectto deterioration and damage by decay,termites, marine borers, mechanical forces,and fire. Steps should be taken to insure thatpiles will remain durable in semipermanentor temporary structures. Untreated timberpiles entirely embedded in earth and cut offbelow the lowest groundwater level, sub-merged in freshwater, or frozen into saturatedpermafrost soils are considered permanent.The lowest groundwater table should not behigher than the invert level of any sewer orsubsurface drain existing or planned, norhigher than the water level at the siteresulting from the lowest drawdown of wellsor sumps. Percolating groundwater heavilycharged with acids or alkalies can destroypiles. The following subparagraphs describethe most destructive forces on piles.

a. Decay. Decay is caused by fungi whichpenetrate the wood in all directions. Fungifeed on the wood, which breaks down androts (figure 8-l). The probability and rate ofdecay depend on several factors.

R E H A B I L I T A T I O N

(1) Species. Timber piles which arenaturally durable have a useful life formany decades.

(2) Preservatives. Untreated timber pilesthat are alternately wet and dry may lastfrom five to ten years, whereas treatedpiles will last from 10 to 20 years.

(3) Temperature. Timbers which lastseveral years in temperate climates maylast less than a year in tropical conditions.

(4) Dampness (permanent or intermittent).All timber piles will remain free fromdecay if the water content is kept below 22percent. The decay is rapid if the pile isalternately wet and dry. Such a situationmay exist in a waterfront structure wherethe tide causes large changes in the waterlevel. On semipermanent structures onland, damage is caused by lowering thewater table during the life of the structure.

(5) Oxygen. Wood-rotting fungi cannotdevelop without a supply of free oxygen.

b. Termites. Timber piles in warm cli-mates are subject to attack by subterranean

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termites. Termites are active through thetropics and subtropics in both wet and andregions. Some species occur in the warmerparts of temperate countries—for example, insouthern France—but they are not foundin the colder parts of these regions. Termiteactivity is very destructive. In the tropics,timber piles in contact with the ground maybe destroyed in a few weeks unless they arefrom a species resistant to termites.

c. Marine borers. Marine borers rapidlydestroy untreated wooden structures in saltwater (figure 8-2). In the tropics they can dosevere damage in a few months unless thetimber is one of the few resistant species suchas greenheart or turpentine wood (seeappendix). In temperate climates, attack isgenerally slower and sporadic. Except forcertain resistant species, timber piles arelikely to be destroyed in a few years.

d. Mechanical forces. Timber piles inwaterfront structures or bridges are damagedby abrasive action between the mud line andthe water or, in some cases, even above thehigh waterline. Wear can be caused byfloating craft, drifting objects, ice, and waveor current action which scour the pile surfacewith pebbles or coarse sand.

e. Fire. Timber piles, especially if creosoted,are extremely susceptible to destruction byfire.

8-2. Preventive measures.

a. Basics. Protection against wood-destroying organisms can be obtained byselecting naturally resistant timber species(see appendix) or by applying preservativetreatments. Natural resistance applies onlyto the heartwood. Sapwood, even of very

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FM 5-134

durable species, is rapidly attacked by wood-destroying organisms. It is better, par-ticularly in the tropics, to use preservativetreatment rather than to rely on naturalresistance.

b. Protection from decay and insects.The most effective prevention against decayis by applying creosote or other treatment topoison the food supply of insects. Charringthe surface of the timber when practicablemay provide protection against termites.

c. Protection from marine borers.Leaving the bark intact on untreated pilesaffords some protection. Bark adheres best totimber which is cut in the fall or winter.Creosoting will afford protection for five toten years against some species of marineborers. With other species, it is necessary toencase the pile in concrete or sheath it in

copper throughout With the activity zone(mud line to the high waterline).

d. Protection from mechanical forces.Pile fenders and dolphins are widely used toprotect pile foundations against floatingobjects. Pile sheathing may be used to protectagainst damaging erosion.

e. Protection from fire. The danger of firemay be reduced when designing largewaterfront structures by dividing the facilityinto unite with fire walls or bulkheads whichextend from the underside of the deck to alevel below the low waterline. On permanentstructures, foam extinguishers should beinstalled.

8-3. Preservative treatment.

The life of timber piles is greatly lengthenedby treatment with preservatives. Creosote oil

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FM 5-134

is the most satisfactory material for treatingtimber piles and is most likely to be availablein military situations. Various otherchemicals, such as copper sulfate and zincchloride, are poisonous to animal life. Sincemost of these chemicals are soluble in water,they leach out, rapidly losing their protectiveeffect.

a. Application. Wherever possible, all piling,as well as other timber members, should betreated at a preservative plant, normallylocated alongside a sawmill, before beingdispatched to the site on which they are to beused. Piles intended for preservativetreatment should have all of the outer barkand at least 80 percent of the inner barkremoved. Remaining strips of inner barkshould not be more than ¾-inch wide normore than 8 inches long.

b. Handling. Care must be taken in handlingtreated timber to minimize the disturbance ofthe treated surface. The effectiveness of thetreatment depends on keeping the creosotedsurface unbroken. Timber hooks, pile poles,and the like are not used on treated timbers. Ifthe surface must be punctured or cut, as innotching to apply a brace, protection is partlyrestored by mopping on two or more coats ofcreosote oil at a temperature between 175° Fand 200°F. Methods of applying preser-vatives are the brush and pressure methods.

(1) Brush method. The least satisfactorymethod of treatment is the brush method(figure 8-3), in which the preservative isliberally applied like paint. The preser-vative penetration obtained by this methodis slight. Some improvement over the brush

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FM 5-134

method is obtained by dipping the pile intohot creosote.

The chief use of hand applications is intreating cuts or borings made on treatedmembers during fabrication of a structure.Such cutting should be avoided as much aspossible, since it is important that anunbroken shell of preservative bemaintained for adequate protection. Anycuts that cannot be avoided should receivecareful attention.

Particular attention should be given tothe protection of butt ends of treated timberpiles when they are cut off. If the butt is tobe exposed at the cutoff, as in fender piles,the end of the pile may be protected. Thecutoff end should be brushed liberally withtwo coats of hot creosote oil, followed by aheavy coat of coal-tar pitch (figure 8-3).Protection is increased by applying two orthree layers of pitch-soaked canvas coatedwith sealing compound. It is desirable torenew the protective coating every year bytwo heavy applications of hot creosote.

Treated piles that are to be capped stircutting should be protected by applicationof hot creosote oil and tar pitch. It isdesirable to place a sheet of heavy roofingpaper or a metallic cap over the butt of thepile before placing a timber cap.

Where treated piles in a foundation arecut off before receiving a footing, the cutoffshould be given two heavy coats of hotcreosote oil, allowing sufficient timebetween applications for absorption.

(2) Pressure method. The most satisfactoryand enduring treatments are those carriedout in plants with equipment for pressureprocesses. Specifications normally requirea 12-pound retention of creosote per cubicfoot of wood. Considerable equipment isrequired. The method is not described

because it is impractical for militaryoperations. Pressure-treated piles shouldbe used for all marine construction andwherever possible in deliberate con-struction.

8-4. Concrete encasement.

Effective protection can be provided byencasing timber piles in concrete, usually bygrouting the annular space between the pileand a section of pipe. Precast concrete jacketshave been designed and used for permanentinstallations. Concrete jackets have also beenformed by shooting concrete (guniting) ontimber piles, either before or after driving.The protective coating is generally from 1½to 2-inches thick and reinforced with wiremesh. Protection provided to the pile isexcellent.

8-5. Sheathing.

Metallic sheathing is effective only if it is freefrom holes. The protection provided is notpermanent. Metal casings are sometimes usedaround piles. The pile is prepared and driven,and the metal casing is slipped down aroundthe pile after the driver has been removed.The space between the pile and the casing isthen filled with concrete. For timber sheetpiles, a layer of tar paper sealed with mop-coated bituminous material and protected bya wood sheathing placed over the face of thepiling. A thick coating of bituminous materialis effective as long as the coating remainsintact. This protection may last for hastyconstruction in water infested by marineborers. A longer-lasting method is to wrapthe pile with burlap or tar paper over thecoating and add another coating.

8-6. Periodic inspection.

Periodic inspection of pile foundations afterinstallation is important. Damage detectedearly can be more easily and economically

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FM 5-134

repaired than later. For temporary waterfrontstructures, inspection of the piling down tothe low water level may be sufficient. Forimportant, permanent structures, inspectiondown to the mud line should be made bydivers or by pulling a pile. The effects ofmarine borers should be watched carefullysince deterioration may proceed very rapidlyonce they have entered the pile. Deteriorationdue to other causes may be accelerated byborer damage. With some types of borers,damage can be detected only by cutting thewood. In such cases, it is valuable to drive apile like that used in the structure a shortdistance below the mud line. It may be pulledand inspected periodically.

Section II. STEEL PILES

8-7. Damage and deterioration.

The life of steel piles is generally not a matterof concern in temporary military structures.When a structure of longer life is involved orexposure conditions are severe, the load-carrying capacity and useful life of a steelpile may be reduced by corrosion or abrasion.

a. Corrosion. Corrosion is caused by thetendency of metals to revert from their freestate to the combined form in which theynormally occur as ores. It is caused by adifference in potential between two points ona conducting material in the presence of anelectrolyte. In the case of a steel pile, theanode is the corroding surface; and theinterior portion of the metal is the cathode.Corrosion may also be caused by sulphate-reducing bacteria which are widely dis-tributed in soils and natural waters. The rateof corrosion vanes sharply with the soil,depth of embedment, water content, or thenature of the water in which the pile may beimmersed.

Steel piles in contact with undisturbedsoil below the groundwater level will not besubject to significant corrosion.

Steel piles are subject to corrosion onlywhen extending through fresh waterpolluted by industrial wastes whichcontain large amounts of corrosive acids.

Deterioration of steel piles in seawatercan be rapid when waves spray saltdeposits on the piles. The zone of mostactive corrosion lies between the low-tideand high-tide levels.

Steel piles are subjected to rusting whenexposed to the air at the ground line andfor several feet beneath the ground surface.

b. Abrasion. Corrosion is accelerated byabrasion caused by waterborne sand or gravelwhich is agitated by tidal action. Abrasionalone is not a serious problem, except thatwhen it damages the protective covering ofthe pile, corrosion proceeds more rapidly.Timber cladding offers temporary protection.

8-8. Preventive measures.

a. Bitumastic surfacing. It is oftendesirable to provide a protective coating overa portion of a steel pile. Paints used onstructural steel generally do not providesufficient protection under severe corrosiveconditions. Some special paints, whenavailable, are used with greater success.Coal-tar pitch or a bitumastic paint (hot orcold) is applied to the active zone before thepile is driven. The portions exposed to the airare maintained like other steel structures.The success of surface coating depends uponkeeping the protective surface intact. If anycracks or pinholes are left in the coating,heavy corrosive attack may occur at suchpoints. The surface must be prepared, and thematerial applied evenly and completely.

b. Concrete encasement. Positive pro-tection against severe corrosion, particularlywhere abrasion is a contributing factor, canbe provided by encasing a steel pile in concrete

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FM 5-134

over the length under the greatest attack.Poured concrete encasements are used mostoften (figure 8-4). A metal form is placedaround the pile over the desired length ofprotection, and the form is filled with denseconcrete. Protection is from 2 feet below meanlow water to 3 feet or more above mean highwater. The metal form may be left in place,thus providing additional protection. Many

other schemes have been used to form aconcrete jacket around steel piles onpermanent and important structures. Detailsof these methods are beyond the scope of thismanual.

c. Other measures. For temporarystructures where severe corrosion is expected,an obvious solution is to increase the size of

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FM 5-134

steel piles. If piles are designed as columns,working stresses used in the design may bereduced in anticipation of future reductionsin sections caused by corrosion, thusachieving a similar result. Cathodic pro-tection, if used correctly, will solve manycorrosion problems; however, it is seldompractical in military structures.

8-9. Inspection.

Steel piles which form a part of a permanentstructure should be inspected periodically,particularly in waterfront structures. Carefulattention must be given to the zone where themost severe corrosion is likely to occur todetect damage as early as possible and toapply remedial measures. If a protectivecoating or concrete encasement is used, itscondition should be checked periodically tomake sure that it continues to fulfill itsintended function. Inspection to low watermay be adequate in many cases; in othercases, inspection by divers should be earnedout to the mud line. As with timber piles, itmay be desirable to pull a pile for inspection.

Section III. CONCRETE PILES

8-10. Damage and deterioration.

Groundwater may contain destructive acids,alkalies, or salts which damage concrete.High concentrations of magnesium or sodiumsulphate salts are particularly destructive. Inhumid regions, moisture penetrates theportion of the pile exposed to the air andcauses the steel reinforcement to rust and theconcrete to span on the surface. Alternatethawing and freezing accelerates deteri-oration as water in the voids or cracks in theconcrete freezes, creating an expansive forcewhich furthers cracking and spalling.Occasionally, concrete piles in salt water aredamaged by rock-boring mollusks (pholads),similar to marine borers that attack timberpiles. The greatest damage to concrete piles is

caused by the rusting of the reinforcementsteel and consequent cracking and spallingof the concrete. Prestressed piles tend to bemore durable, as tension cracking isminimized.

8-11. Preventive measures.

Deterioration and damage are most pro-nounced in piles of poor quality concrete.Generally, difficulties do not arise if a dense,impervious concrete mix is used and if thesteel reinforcement is provided with anadequate (2 to 3 inches) cover of concrete.Careful handling and placing of precast pileswill avert excessive stresses and subsequentcracking. When concrete piles are subjectedto abrasion, metal shielding or timbercladding is used in the area of greatestexposure.

8-12. Periodic inspection.

As with other types of pile foundations, acareful watch should be kept for signs ofdeterioration, particularly for spalling of theconcrete and deterioration of the reinforcingsteel.

Section IV. REHABILITATION

8-13. Considerations.

Pile foundations may be destroyed ordamaged by deterioration or explosive actionin a tactical situation. In either case, it isnecessary to evaluate the situation anddetermine what to do. Most discussion in thissection applies to all types of piles. Evaluatingfactors are as follows.

Is the pile foundation capable ofsupporting the loads anticipated withoutrehabilitation?

If the pile foundation has a limitedcapacity, what load limits can it carrywithout damage to the foundation?

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FM 5-134

Has the load-carrying capacity of the pilefoundation been reduced so seriously thatits satisfactory use is impractical? In sucha case, it may be possible to repair theexisting piles or drive new piles.

8-14. Evaluations.

The objective of an evaluation is to obtain allinformation possible to evaluate the load-carrying capacity of the foundation and todetermine the most efficient rehabilitationprocedures. Attention should be given to thenumber and type of piles; size and alignmentexternal damage, such as the twisting orbreaking from explosive charges; deter-ioration which may have taken place in theareas of critical exposure; and underlyingsoil conditions. Examine the remainingportions of the superstructure, classify it, andcalculate the loads for which the super-structure was originally designed. If theoriginal design followed good engineeringpractice for the materials, construction, anddesign load, the piles are assumed to be ableto carry loads for which they were designed,less the effects of damage or deterioration.Details for this process are contained in FM5-36 and TM 5-312 for bridges and in TM-360for port and harbor structures. This estimateis appropriate for buildings unless they areunusually heavy structures.

8-16. Replacement and repair.

Five procedures are used in replacing andrepairing foundation piles.

a. Replacing damaged piles. If a wharf,pier, or span can support the weight of a piledriver, several floor planks are removed; andthe new piles are placed and driven throughthe hole. When an entire bent is replaced, it iscapped and wedged tightly against theexisting stringers.

b. Adding bents above the waterline.Timber piles damaged or deteriorated abovethe high waterline can be cut off level andcapped with a trestle bent to attain theelevation of the old stringers.

c. Using concrete extension piles.Another method of rehabilitating timber pilesdamaged above the waterline is to cut off thedamaged pile, shape the butt end (tenon), andadd an upper concrete section.

d. Using cutoff and splice. Upper portionsof damaged or deteriorated piles may berepaired by cutting them off level and splicingthem. When long, unsupported timber pilesare spliced with timber, the bending strengthat the splice usually is much less than that ofthe unspliced pile. A stronger splice can beobtained with a reinforced concrete en-casement. To make this type of splice, four6-inch straps are bolted across the splice jointto hold together the two sections of timberpile. The ends of ten to twelve 6-foot re-inforcing steel bars (¾ inch) are bent, and thebars are placed longitudinally across thesplice joint. The ends are driven severalinches into the pile. A cage of No. 10 wiremesh (4 inches x 6 inches), the same length asthe unbent portion of reinforcing bar, isfastened to the bars. Five or six turns of wireare fastened to the top and bottom of the cageand stapled to the pile. A sheetmetal form isthen placed around the reinforcement for 5inches of concrete encasement around thesplice. Bituminous material is used to seal thejoint between the concrete encasement andthe pile after the form is removed (figure 8-5).

e. Reconstructing damaged concretepiles. Damaged portions of concrete pilesmay be cut off with the original reinforcingbars extending above the concrete cutofflevel. Forms are placed, reinforcement isadded, and the piles are extended to thenecessary level as described in chapter 2,section IV.

8-9

FM 5-134

8-10

FM 5-134

A P P E N D I X

W O O D S U S E D A S P I L E S

A-1. Local timber.

Throughout the world many varieties of wood are used for piles. Some woods are commonlyused, and their properties have been thoroughly evaluated and reported. Others are used locally.Little information about them is available in engineering literature. When it is possible to uselocal woods, consult local sources of information to determine their suitability. This appendixpresents information concerning the woods most commonly used. The woods mentioned hereare identified by their common names. Local terms frequently designate different varieties ofthe woods, and locally available woods are not discussed here.

A-2. North American timber.

a. Douglas fir covers many varieties found principally in the western part of the United States.This wood is very strong and is excellent for piles. The heartwood is resistant to decay.Treatment ranges from difficult to moderate, generally requiring pressure for effectivepenetration. Creosoting is necessary, as with most North American woods, to provide someprotection against borers. Fir is available in long lengths.

b. Southern pine has many varieties, including longleaf and shortleaf, and is good for piles. Theheartwood is moderately decay resistant. This wood takes preservatives well. Treatment isnecessary to provide resistance to borers.

c. Cypress (southern) comes from the swamps of the Gulf and Atlantic coasts and theMississippi Valley. Tidewater red cypress is more durable than either the yellow or whitevariety. The heartwood of cypress is very resistant to decay. The sapwood is thin; hence the pilesshould be durable. Treatment with preservatives is difficult but can be done when the sapwoodis thick. Cypress has medium strength.

A-1

FM 5-134

d. Oak has been used for various types of short piles. Oak is expensive in many areas. There aremany types of oak, varying in characteristics. Meet varieties are strong, durable, and quiteresistant to decay. They must be creosoted to prevent borer attack, and the difficulty oftreatment varies. Oak corrodes steel and iron.

e. Lurch, a softwood which has moderate to high strength, is tough and durable, even whenalternately wet and dry. It is difficult to treat with preservatives. Western larch, found in theUnited States, compares favorably with European larch.

f. Redwood is a softwood of medium strength, not widely used for piles. It has little resistance toborers and can be treated with only moderate difficulty.

g. Mangrove, palm, and palmetto have been used in the southern United States, principallybecause they have shown some resistance to attack by borers. They are very soft and aregenerally jetted into place, They are unable to withstand normal driving. Piles of this type havelow strength and are used to support very light loads. They are susceptible to decay above thewaterline.

h. Other woods which have been used for piles are cedar, cottonwood, elm, various gums, andmaple.

A-3. Central and South American timber.

a. Angelique is wood of Surinam which has considerable resistance to borers in tropical waters.It contains silica, which aids in borer resistance.

b. Black kakarali is a hard, dense wood used in Guyana for waterfront structures. It has goodresistance to borer attack.

c. Foengo is from Surinam and has good resistance to borers in structures located in the CanalZone.

d. Greenheart from Guyana and Surinam is an excellent wood for piles for marine structures. Itis resistant to borers, particularly in temperate zones. This is probably due to the alkaloid itcontains. Greenheart is resistant to treatment since it is dense and close grained.

e. Mahogany is an excellent wood for piles since it has high strength and durability. It is foundin various parts of Central and South America.

f. Manbarklak comes from Surinam. It is hard and heavy. It has a high silica content and offersgood resistance to borer attack. It has good service records in both tropic and temperate waters.

g. Mangrove, palm, and palmetto are used in various areas of Central and South America.

h. Purpleheart is found in Trinidad, Guyana, French Guiana, and Surinam. It is resistant todecay, but more susceptible to borers than greenheart.

A-2

FM 5-134

A-4. European timber.

a. Larch is one of the toughest and most durable of the European woods. It is a softwood,although one of the denser and harder types. It can be treated with preservatives by pressuremethods.

b. Northern pine is given many local names and exists in several varieties. It is generallystrong, elastic, and quite durable.

c. Norway pine is similar to Northern pine and has medium strength.

d. English oak is strong, tough, and durable. It is seldom available in long lengths and isexpensive for ordinary use. It will corrode iron or steel fastenings.

e. Alder is quite durable when completely submerged but susceptible to decay when alternatelywet and dry. It is easy to treat and has moderate strength and resistance to borer attack.

f. Elm is usually strong and tough. Some species are quite resilient, which has led to some use ofpiles of this type as fenders on waterfront structures. Elm is fairly durable and can be treatedwith preservatives, offering fair resistance to borers.

g. Kail has low strength and is not widely used for piles when other woods are available.

h. White deal has been used for piles, but has low strength.

i. Many different firs, spruces, and pines are used locally in Europe, and some are exported.They are softwoods, but give reasonably good service when creosoted.

A-5. African timber.

Many different woods are used locally in Africa. Little information is available as to theirproperties. Local inquiry should be made to determine the suitability of a particular wood for usein pile structures.

A-6. Asian timber.

a. Teak is a hardwood found in many parts of Asia. It has high strength and durability andmakes excellent piles where available.

b. Eng is found in various countries and has been used as a substitute for teak. It has mediumstrength and durability when treated.

c. Mahogany, found in various parts of Asia, is an excellent strong and durable wood for piles. Itis extremely resistant to penetration of preservatives. Philippine mahogany is an example ofthis type of wood in Asia.

A-3

FM 5-134

d. Sal is found in India and is used in waterfront structures. It has high strength and durability.

e. Acle is found in India and has high strength and good resistance to borers. It is widely used inmarine structures.

f. Pyinkado is a Burmese hardwood having good strength and durability. It is extremelyresistant to the penetration of preservative materials.

g. Kolaka is found in the Celebes and is used for piles in Indonesia. It is high in silica content,thus is generally resistant to borers.

h. Chir is Indian wood used for piles. It has medium strength.

i. Deodar is used in India and has medium strength and durability.

j. Peon is an Indian wood with medium strength and durability.

k. Jarul is used to some extend in India and has high strength.

l. White siris is an Indian wood of high strength and durability.

A-7. Australian timber.

a. Ironbark has medium strength and good durability.

b. Jarrah is dense, impermeable wood. It has medium strength and high durability.

c. Karri, for use in pile structures, has properties similar to those of jarrah.

d. Tallow wood is a very dense, impermeable species having good durability.

e. Turpentine wood is dense, impermeable, and durable. Resistance to borers lies in theproperties of the bark, which must not be removed or damaged.

f. White or red gum has medium strength and high durability.

g. Totara is a New Zealand wood with good resistance to borer attack.

h. Other woods are available in this area of the world. For example, Australia has manyvarieties of eucalyptus that are more resistant to borers than oak or pine.

A-4

FM 5-134

G L O S S A R Y

Section I. DEFINITIONS

Adapters. Devices used to attach leads to the point of a crane boom.

Allowable load. The load which maybe safely applied to a pile based on bearing capacity andsettlement.

Anchor pile. A pile used to resist tension or uplift loads.

Anvil. The part of a power-operated hammer which receives the blow of the ram and transmits itto the pile.

Batter pile. A pile driven at an angle to the vertical.

Bearing pile. A pile driven or formed in the ground for transmitting the weight of a structure tothe soil by the resistance developed at the pile point or base and by friction along its sides.

Bent. A structural member or framework used for strengthening a bridge or trestle transversely.

Bracing. A system of inclined or horizontal structure members fastened to the piles of a bent or arow to increase stability.

Brooming. Separation of fibers (usually at butt or tip of a timber pile) caused by improperdriving.

Cast-in-place pile. A pile formed by excavating or drilling a hole and filling it with concrete.

Compaction pile. A pile driven to increase the density of very loose, cohesionless soil.

Composite pile. A pile formed of one material in the lower section and another in the upper.

Glossary-1

FM 5-134

Concrete piles. Piles made of concrete aggregate either cast-in-place or precast.

Concrete sheet piles. Reinforced precast piles of rectangular cross section with tongue-and-groove interlocks.

Cushion. A block inserted between the hammer and the top of the pile to minimize damage.Cushions can be wood, belting, old rope, or other shock-absorbent materials.

Dap. Incision or notch cut in timber, into which the head of a pile or other timber is fitted.

Diesel hammer. A stationary cylinder and a cylinder which is driven upward by a diesel fuelexplosion. Open-end and closed-end types are used.

Dolphin. Piles driven close together in water and tied together. The group is capable ofwithstanding lateral forces from vessels and other floating objects.

Drop hammer. A weight with grooves in the sides, that falls on the end of the pile when driving.

Dynamic pile formulas. Equations which provide empirical determination of the approximateload-carrying capacity of a bearing pile, based upon the behavior of the pile during driving. Theformula of principal value to the military engineer is the Engineering News formula.

End-bearing pile. A pile that derives its support from an underlying firm stratum.

Fender pile. A pile driven in front of a structure to protect it from damage from floating objects orto absorb shock from impact.

Floating pile drivers. Pile drivers mounted on barges, rafts, or pneumatic floats. A floatingcrane may be used as a pile driver when fitted with pile-driving attachments.

Follower. A member between the hammer and the pile to transmit blows to the pile when the topof the pile is below the reach of the hammer.

Fore-batter guide. A beam extending from the forward end of the frame of a steel-frame,skid-mounted pile driver to the leads.

Friction pile. A pile which derives its support from skin friction between the surface of the pileand the surrounding soil.

Guide pile. A pile which guides driving of other piles or supports wales for sheet piling.

H-piles. Steel H-sections used as bearing piles.

Heaving. Uplifting of earth, between or near piles, caused by pile driving. Also, uplifting ofdriven piles in such a mass of earth.

Glossary-2

FM 5-134

Helmet. A temporary steel cap placed on top of a concrete pile to minimize damage to the headduring driving.

Jetting. A method of forcing water around and under a pile to loosen and displace thesurrounding soil.

Lagging. Plates, strips, or blocks fastened to a pile to increase its load-carrying capacity.

Lead braces. Structural members used to fasten the leads to the base of the crane boom.

Leads. A frame (upright or inclined) which supports sheaves at the top for hoisting the pile andhammer. The leads are equipped with parallel members for guiding the pile and hammer. Theymay be fixed, swinging, or hanging, depending on how they are attached to the pile driver.

Log hammer. An expedient pile-driving hammer made up of hardwood and a steel base plate.

Moon beam. A slightly curved beam placed transversely at the forward end of the pile driver toregulate side batter.

Pile. Load-bearing member of timber, steel, concrete, or a combination forced into the ground tosupport a structure.

Pile bent. Two or more piles driven in a row transverse to the long dimension of the structure andfastened together by capping and bracing.

Pile cap. A masonry, timber, or concrete footing formed to transmit the load from the structureto the pile group.

Pile driver. A machine with a drop, steam, diesel, or pneumatic hammer with hoistingapparatus, leads, and frame for driving piles. The machine may be placed on skids, a float, arailroad car, or other mountings.

Pile-driving cap. A device placed on top of a pile to protect the pile and facilitate driving. It is alsoreferred to as a pile-driving helmet.

Pile-driving hammer. See drop hammer and pneumatic or steam hammer.

Pile extractor. A device used to pull piles, usually an inverted steam or air hammer with yokeequipped to transmit upward pulls to the piles.

Pile foundation. A group of piles ueed to support a column or pier, a row of piles under a wall, or anumber of piles distributed over a large area to support a mat foundation.

Pile group. Bearing piles driven close together to forma pile foundation.

Pile line. A line (rope or cable) to lift a pile and hold it in place during the early stages of driving.

Glossary-3

FM 5-134

Pile load test. A field load test conducted on a pile to determine its load-carrying capacity.

Pile shoe. A metal protection for the foot of a pile used to prevent damage or to obtain greaterpenetration when driving into or through hard stratum.

Pipe piles. Steel pipe sections used as bearing piles.

Pneumatic or steam hammer. A stationary cylinder and a moving part, (the ram) whichincludes the piston and striking head. Both single-acting and double-acting hammers are used.

Precast concrete piles. A reinforced or precast concrete pile cast and thoroughly cured beforedriving.

Rail piles. Steel railroad rails used as bearing or sheet piles in expedient situations.

Ram. The rising and falling part of the hammer which delivers the blow.

Refusal. The condition when a pile driven by a hammer has zero penetration (as when a point ofthe pile reaches an impenetrable stratum such as rock) or when the effective energy of thehammer blow is no longer sufficient to cause penetration (as when the hammer is too light or itsvelocity at impact is not adequate). The pile may cease to penetrate before it has reached thedesired supporting power. “Refusal” may indicate the specified minimum penetration per blow.

Scour. The undermining of a pile foundation by the action of flowing water.

Set. The net distance by which the pile penetrates into the ground at each blow of the hammer.

Set-load curve. A curve showing the relationship between set and load for a given set ofconditions and a given dynamic pile formula.

Settlement. The amount of downward movement of the foundation of a structure or a part of astructure under conditions of applied loading.

Soil profile. A graphic representation of a vertical cross section of the soil layers below groundsurface,

Spliced pile. A pile composed of two or more separate lengths secured together, end to end, toform one pile.

Spotter. A horizontal member connecting the base of fixed leads to the base of the crane boom.The spotter can be extended or retracted to permit driving piles on a batter and also to plumb theleads over the location of a vertical pile.

Springing. Excessive lateral vibration of a pile.

Glossary-4

FM 5-134

Spud. A short, strong member driven and then removed to make a hole (for inserting a pile thatis too long to place directly in the pile driver leads) or to break through a crust of hard material.Also a movable vertical pipe or H-section placed through a strong frame on a floating pile driveror dredge to hold the vessel in position.

Spudding. The operation of raising and dropping a heavy pile to break through a thin layer ofhard material or an obstruction.

Steam hammer. See pneumatic or steam hammer.

Steel bearing piles. Rolled or fabricated sections used as piles.

Steel-frame, skid-mounted pile driver. A pile driver mounted on skids and made up of steelmembers.

Steel sheet piles. Steel shapes, rolled or fabricated, which become interlocked as they aresuccessively driven, thereby forming a continuous wall or cell which is capable of sustaininglateral loads and resisting forces tending to separate them.

Stringer. A member at right angles to, and resting on, pile caps or clamps and forming a supportfor the superstructure.

Tension pile. See anchor pile.

Test pile. A pile driven to determine driving conditions and required lengths. Also a loading testmay be made to determine the load-settlement characteristics of the pile and surrounding soil.

Timber pile. A bearing pile of timber, usually straight tree trunks cut off above groundswell withbranches closely trimmed and bark removed.

Timber pile driver. An expedient pile driver made up of dimensioned lumber.

Treated timber pile. A timber pile impregnated with a preservative that retards or preventsdeterioration due to organisms.

Tripod pile driver. An expedient pile driver made up of local timber and usually hand operated.

Ultimate bearing capacity. The maximum load which a single pile will support. The load atwhich the soil cannot be penetrated.

Wakefield sheet piling. Timber sheet piles of three planks bolted or spiked together. The middleplank is offset, forming a tongue on one side and a groove on the other.

Wale. A member extending along a row of piles and fastened to them which serves as a spacer forthe piles or support for other members. In a fender it absorbs shock and protects a structure orfloating craft from floating objects. It is also called waler or ranger.

Glossary-5

FM 5-134

Welded-angle pile driver. An expedient pile driver made up of steel angles welded or boltedtogether.

Wood-frame, skid-mounted pile driver. A pile driver mounted on skids and made up of timbers.

Section II. ACRONYMS, ABBREVIATIONS, AND SYMBOLS

Acronyms and Abbreviations.

A

AFCS

Approx

ASTM

CRP

D

DA

DB

DE

DF

dia

el

F

FS

ft

fp

ga

gpm

GWT

Glossary-6

area

Army Facilities Components System

approximately

American Society for Testing and Materials

constant rate of penetration

diameter

deep arch

doubh+acting steam hammer

diesel

differential-acting steam hammer

diameter

elevation

allowable compression stress

factor of safety

foot

fixed point

gage

gallons per minute

ground water table

FM 5-134

MA

h

in

incl

lb

L

max

MHW

min

MLW

n

OC

od

P

pcf

psf

psi

R

s

SA

SPT

sq

TOE

w/

height

inch

including

pound

length

medium arch

maximum

mean high water

minimum

mean low water

number

on center

outside diameter

perimeter

pounds per cubic foot

pounds per square foot

pounds per square inch

radius

straight web

shallow arch

Standard Penetration Test

square

table of organization and equipment

with

Glossary-7

FM 5-134

WF wide flange

Z Zee section

Symbols.

A

Ap

As

a

b

c c

c

c x

cy

D

d

E

e

eO

ex

eY

FC

cross-sectional area of a pile in square inches

cross-sectional area of a pile in square feet

shaft area

adfreezing strength

diameter of pier in feet

compression index

tons per square foot

distance from Y-Y axis to pile for which P, is being calculated

distance from X-X axis to pile for which P, is being calculated

diameter (used in formula)

average diameter in inches measured at one-third of the pile length fromthe butt

elasticity of wood species in psi

driving energy in foot pounds

initial void ratio

distance from point of intersection of resultant with plane of base of structure toY-Y axis

distance from point of intersection of resultant with plane of base of structure toX-X axis

allowable compression stress parallel to grain

Glossary-8

FM 5-134

H

H

I

I x

I y

KC

Kp

lu

ΣΜΣΜ

N

n

Nq

P

Pa

Ph

P1

P °

P v

Qall

Qu

R

r

S

thickness of the clay layer in feet

ultimate decrease in thickness of a confined clay layer due to consolidation in feet(also, settlement of the structure)

least moment of inertia in inches

moment of inertia of pile group about X-X axis

moment of inertia of pile group about Y-Y axis

earth pressure coefficient

passive earth pressure coefficient

unsupported length in inches

summation of all moments about the center of gravity of pile group at the level ofpile fixity due to Σ

number of blows per foot

number of piles

bearing capacity factor

perimeter of group

axial component of pile load

horizontal component of pile load

final pressure in tons per square foot

V and ∆H

initial pressure in tons per square foot

vertical load on any pile

safe load in pounds

ultimate bearing capacity of group

resultant

least radius of gyration in inches

pile spacing in feet

Glossary-9

FM 5-134

s

v

w

WL

x

y

θ

δ

average net penetration or pile set, in inches, per blow for the last 6 inchesof driving

resultant of all vertical loads on pile group

summation of all vertical loads

weight of striking parts in pounds

liquid limit

coefficient of horizontal batter

coefficient of vertical batter

angle of the batter

angle of shaft resistance

Glossary-10

FM 5-134

R E F E R E N C E S

I. REQUIRED PUBLICATIONS. Required publications are sources that users must read inorder to understand or to comply with this publication.

Technical Manuals (TM).

TM 5-303 Army Facilities Components System Logistic Data and Billsof Materials

TM 5-312 Military Fixed Bridges

TM 5-545 Geology

TM 5-852-4 Arctic and Subarctic Construction Foundations for Structures

II. RELATED PUBLICATIONS. Related publications are sources of additional information.They are not required in order to understand this publication.

Army Regulations (AR).

AR 310-25 Dictionary of United States Army Terms

AR 310-50 Catalog of Abbreviations and Brevity Codes

Field Manuals (FM).

FM 5-35 Engineer’s Reference and Logistical Data

FM 5-36 Route Reconnaissance and Classification

References-1

FM 5-134

Technical Manuals (TM).

TM 5-301-1 Army Facilities Components System-Planning (Temperate)

TM 5-301-2 Army Facilities Components System-Planning (Tropical)

TM 5-301-3 Army Facilities Components System-Planning (Frigid)

TM 5-301-4 Army Facilities Components System-Planning (Desert)

TM 5-302-1 Army Facilities Components System-Design, Vol 1

TM 5-302-2 Army Facilities Components System-Design, Vol 2

TM 5-349 Arctic Construction

TM 5-360 Port Construction and Rehabilitation

TM 5-742 Concrete and Masonry

Engineer Manuals (EM).

EM 1110-2-2906 Design of Pile Structures and Foundations, US Army Corps ofEngineers

Available from: OCE Publication Depot890 South Pickett StreetAlexandria, VA 22304

Navy Publications.

NAVFAC DM-7.1 Soil Mechanics

NAVFAC DM-7.2 Foundations and Earth Structures

NAVFAC DM-7.3 Stabilization and Special Geotechnical Construction

Available from: Department of the NavyNaval Facilities Engineering Command200 Stovall StreetAlexandria, VA 22332

References-2

FM 5-134

I N D E X

Page

Accessory equipmentAdaptation of floating cranesAnchoring of pile driver raftsAnchor pilesAvailability

Cast-in-place pilesPrecast concrete pilesSheet pilesSteel sheet pilingTimber piles

Batter piles:DefinedDetermining distribution of loadsLoads imposed

Bearing piles, foundation design:Rigid piles in clayRigid piles in sand

Bridge pile foundations, rehabilitationBrush method, preservative treatment of timberBuilding pile maintenance and rehabilitationCaps, drivingClassification of timber piles (table 2-1)Cold weather pile drivingCompaction pilesConcrete piles, cast-in-place:

Drilled piers (uncased)DurabilityShell-type (cased)Strength

Concrete piles, cause of damageConcrete piles, maintenance

3-223-213-221-3

2-122-72-132-142-3

1-17-67-6

5-135-138-88-48-13-112-24-251-1

2-132-132-122-138-88-8

Index-1

FM 5-134

Concrete piles, precast:AvailabilityCuringDurabilityFormsHandlingManufacturePlacementShipmentStorageStrengthTypes

Construction, pile:DeliberateHasty

Corrosion of steel pilesCutting and capping of piles:

Anchoring pilesConcrete pilesSteel pilesTimber piles

Decay, timber pilesDefinitionsDeterioration of piles:

ConcreteSteelTimber

Determination of resistance in bearing stratumDiesel hammers, pile-dirivingDistribution of loads to piles in a group, foundation designDolphins, definedDrilled pilesDriving (see also pile-driving operations):

Cold weatherDriving problemsPermafrostPile driving in groupsSheet pilesUnderwater

Driving requirements

Page2-102-102-102-92-122-82-102-122-122-102-7

1-5, 2-11-5, 2-18-6

4-324-304-304-308-11-1

8-88-68-15-113-76-11-34-33

4-256-54-266-14-324-254-8

Index-2

FM 5-134

Driving with mobile equipment:Bridge or wharfStandard trestle, 50-tonTemporary earth causeways

Drop hammers, pile-drivingEncasement (concrete) of timber pilesEnd-bearing piles, definedEquipment for pile driving (see pile-driving equipment)Expedient pile driversFender pilesFloating pile driversFloating rigsFollowers, pileFriction piles, definedFriction piles, in clay (design example)H-pilesHammers, pile-drivingJackingJetting, equipmentLagging, timber pilesLagging, steel pilesLeads, pile-drivingLengths of piles, determining for foundationsLimitations of pile test loadsLoad-carrying capacity of bearing piles (see bearing piles,

foundation design)Loading procedures:

Constant rate of penetration methodContinuous load method

Maintenance of timber pilesMarine borers, timber pilesMaterials, piling:

Army Facilities Component Systems (AFCS)Consideration in selecting typeCostsMaterial selection

Page4-224-254-233-68-3,6-51-13-13-151-33-214-223-141-16-142-53-11,3-124-223-234-24-53-25-15-12

5-1

5-115-108-18-2

2-11-4, 2-11-71-5

Index-3

F M 5 - 1 3 4

Miscellaneous sheet pilesObstructionsPermafrost, pile installation inPiers (definition)Pile drivers on barges, pneumatic floats, or rafts

Pile-driving equipmentAir hammersAssemblyBoomCapsDevices, hammer and vibrating driverDiesel hammersDrop hammersExpedient driversFloating driversFollowersGuidesHammersInstallationJettingLeadsLead bracesPower for expedient pile driversRigsSelecting equipmentSkid frameSpottersSteel-frame, skid-mounted driversVibrating drivers/extractorsWood-frame, skid-mounted drivers

Page4-324-164-261-13-21

3-63-263-23-113-53-73-63-153-213-143-43-113-13-233-23-133-183-13-243-13-133-13-113-15

Pile-driving operations:Alignment 4-127-6Batter piles in groupsCold weatherDriving requirementsGeneral proceduresJackingJettingManpowerMobile equipment, bridge or wharfMobile equipment, temporary earth causewaysObstructionsOverwaterPermafrostPlacing piles by explosives

4-254-84-84-224-164-344-224-234-164-364-264-16

Index-4

FM 5-134

Pile-driving operations:Placing piles by jettingProduction ratePulling pilesSafetyShell-typeSheet piles, generalSpudsTidal liftUnderwaterWater

Pile followersPile foundations:

Capacity in permafrostClayCohesionless soilsDriving in groupsFriction piles in clayGroup actionNegative friction or down dragPile spacingPiles founded on rockPoint bearing piles in sands

Pile load testPiles:

FunctionSelectionSizesTypes

Piling materials (see materials, piling)Pipe pilesPositioning piles for drivingPrecast concrete piles (see concrete piles, precast)Predrilling operationsPreparation of piles or drivingPreservative treatment, timberProperties of selected impact pile hammers (table 3-2)

Page4-164-344-254-344-344-324-224-254-254-223-14

6-86-56-26-16-86-36-86-106-26-115-9

1-31-41-61-62-12-54-222-74-194-18-33-104-25Pulling piles

Rail pile 2-16

Index-5

FM 5-134

Rehabilitation:Basic considerationsEvaluation of existing pile foundationsReplacement and repair

Selection of diesel hammers for various sizes of piling(table 3-1)

Sheathing, timber pilesSheet piles:

AvailabilityDefinitionDescriptionDrivingExpedientFollowersUses

Skid-mounted pile driverSlenderness ratioSplicing:

Steel pilesTimber piles

SpudsStandard H-pilesStandard sheet pilesSteel-frame, skid-mounted pile driversSteel piles:

AbrasionBitumastic surfacingCapsCleaningDurabilityEncasement (concrete)FollowerH-pilesHandlingLaggingOther physical propertiesPeriodic inspectionsPreventive measuresReinforcingSections, otherShipmentStrength

Index-6

Page

8-88-98-9

3-68-5

2-131-11-14-82-163-142-133-1,3-155-2

4-54-24-222-51-13-1

8-68-63-124-32-78-63-152-52-74-52-58-88-64-32-52-72-7

FM 5-134

Strength or consistency of undisturbed clays (table 5-1)Structural design of piles:

Allowable pile stressesBuckling failureDriving stressesLateral loads

Timber piles:AlignmentAvailabilityConcrete encasementsDamage and deterioration causesDecayDescriptionDeterioration, causesDurabilityFire susceptibilityFlexibilityFollowerHandlingLaggingMaintenanceMarine borersPeriodic inspectionPreparationPreservative treatmentPreventive measuresSheathingTabular form for determining load acting on each pile

(table 7-1)TermitesShipmentSourcesSplicingStrength

Treatment of field problems encountered during pile driving(table 4-1)

Tripod pile driverVertical loads, distribution on vertical pilesVibratory driver, pile-drivingWelded-angle pile driverWood-frame, skid-mounted pile driversWorking stresses for timber (table 2-3)Wrapping timber piles

Page

5-16

5-25-25-25-2

4-122-38-58-18-12-18-12-32-52-53-142-54-22-32-28-54-18-38-28-5

7-68-12-52-34-22-3

4-133-157-13-113-183-152-44-1

Index-7

FM 5-134

v

FM 5-134

v i

FM 5-134

vii

FM 5-134

vii

FM 5-134

18 APRIL 1985

By Order of the Secretary of the Army:

JOHN A. WICKHAM, JR.General, United States Army

Chief of Staff

Official:

DONALD J. DELANDROBrigadier General United States Army

The Adjutant General

DISTRIBUTION:

Active Army, ARNG, and USAR: To be distributed in accordance with DA Form 12-11 A, Require-ments for Engineer Construction and Construction Support Units (Qty rqr block no. 33) and DAForm 12-34B, Combat Support (Qty rqr block no. 90).

Additional copies may be requisitioned from the US Army Adjutant General Publications Center,2800 Eastern Boulevard, Baltimore, MD 21220-2896.

★ U. S. GOVERNMENT PRINTING OFFICE : 1991 0 - 281-486 (43308)