dubai

TEHNOLOGY-B

BYBY

ByGamini Rajakaruna

Senior LecturerInternational College of Business and Technology

Sri Lanka

AIM OF THE MODULE

• The aim of this Module is to develop a sound understanding of the functional requirement ,design constraints, and construction methods related to Civil Engineering works.

• It will help to further develop the knowledge of the student on measurments,and pricing of Civil Engineering Works.

• This presentation includes TWO Sessions

SESSION -01Civil Engineering Works & Structures

• This Session includes discussions on :

• Earth Work Operations• Road Construction• Bridges• Earth Retaining Structures• Tunnels• Dams• Cofferdams and Caissons• Beach Stabilization Structures

SESSION-02Environmental & Social Aspects of Construction Process.

• This Session includes;

• Sustainability • Waste Management

EARTH WORK OPERATIONS

• Earth Work operations are carried out in construction work sites, mainly for two purposes. They are

• Earth Filling• Excavations

• Both excavations and filling of earth are involved in almost every construction project, big or small.

EARTH FILLING

• Earth Filling operations are done in large scale on following types of construction projects.

• Earth Dams• Embankments of Reservoirs and Canals• Road Construction• Filling low lying areas.

• Some of the earth work operations are combinations of both excavation and earth work.

MACHINERY USED

• Several types of machinery used for Earth work operations.

• Some machines does several functions and over and over again in cycles.

• Different types of machinery are used for different purposes.

DOZER

LODER

SCRAPERS

COMBINE OPERATIONS

• DAM FILLING: Combination of Scraper +Dozer

• EMBANKMEN FILLING: Combination of Scraper +Dozer and Secondary combination of Loader Dump Truck + Dozer.

• FILLING OF ROADS: Combination Scarper +Dozer and Secondary combination of Loader+ Excavator+ Dump Truck +Dozer.

• FILLING OF LOW LYING LAND: Loader/Excavator+ Dump Truck, Dozer

CYCLE TIME

• Every Machine engaged in earth work operations has to repeat the same work several times over and over again.

• This Cycle consists of many operations.

• The Cycle time of a machine for a particular operation is the sum of all time durations of each operations plus the waiting time.

• This shows that the Productivity of an earth work operations depends in the cycle time

• The Cycle Time is divided in to 2 elements. They are:

• Fixed Time: It includes the time for Loading, Dumping, Turning,Accelarating,Decelerating all are constant under uniform operations.

• Variable Time: It includes Haul time & Return time. Both these depend on the distance traveled and average speed of the vehecle.Usually hauling and returning are at different speed range.

• Therefore it is necessary to determine the time for each separately.

• Cycle Time=Fixed Time+ Variable Time

• Variable Time=Haul Time +Return Time

• Haul Time-Distance between pit &fill x time per unit distance when hauling.

• Time per unit Distance= 1/speed

• Returning Time =Distance between pit and fill x time per unit distance when returning.

EXCAVATIONS

• Several types of excavation can be identified in the construction induestry.They are:

• Excavating to reduce level.• Trench Excavation• Excavation for Fillings• Excavation for under water construction.

EXCAVATING TO REDUCED LEVELS

• Most of the sites have to be leveled before erection of the building to reduce the cost and for proper erection.

• Three methods of reducing levels are:

• Cut & Fill• Cut• Fill.

TRENCH EXCAVATION

• Two types of Trench Excavation involved in the construction industry. They are :

• Manual Excavations.(up to 1.5M deep.)• Mechanical Excavations(1.5M to over 3.0M

deep)

The method of excavation and shoring to be used any particular case will depend upon a number of factors.

• Nature of subsoil can determine the type of plant or hand tools required and the type of shoring required.

• Purpose of the excavation .It helps to determine minimum wideths,depths,and placing of support members to give a reasonable working space with in the excavation.

• Presence of ground water may necessitate the need for interlocking ,shoring ,sum pits and pumps. Large quantities of ground water may prompt the use of dewatering techniques.

• Presence of a large number of services may restrict the use of machinery to such an extent that becomes uneconomic.

• The disposal of the excavated spoil may restrict the choice of plant due to the load and unload cycle not keeping pace with the machine out put.

.Shoring for Shallow Trenches

Shoring for Deep Trenches

• .• •

Shoring for Basement Excavations.

Factors to be considered.

• Following factors to be considered for earth moving operations.

• Loadability: How easy to dig and load

• Moisture Content: It has a affect on soils unit properties.

• Percentage of Swell: The volume expand

• Soil Weight: Affects the performance of the equipment.

Zones of Operations

• There are 3 Zones of operations to consider on a construction project.

• Power Zone:Maximuem power required to overcome adverse site .eg: Rough Terrain etc.

• Slow –Speed power zone: Site conditions are slightly better than Power Zone.

• High Speed Hauling Zone: Ground conditions are good or where long, well maintained haul roads are established.

2.0.ROAD CONSTRUCTION

• A Road can be defined as means that connects two destinations.(Cities/Towns/Places) and facilitate the ground support of both goods and passengers.

• A Highway is an improved Road by given special consideration for speed,saftey and time for transportation of vehicles.

• Following terminologies are used in Road construction

• Carriage Way: This is the portion of the road way designed and constructed for vehicular traffic.

• Shoulder: This is the portion of the road way immediately beyond the edges of the carriage way on which pedestrians use to walk.

• Platform: Refers to the surface of the road including both the shoulder and the carriage way. Platforms are cambered.

2.1.Typical Cross-section of a road

2.2.Classification of Roads

• Class-A: Roads connecting capital of the country with district capitals.• Width of carriage way-24ft• Width of Platform-36 ft.• Generally paved with bitumen surface.

• Class-B: Roads connecting two district capitals and other main towns.• Width of carriage way-12 ft.• Width of Platform-24 ft.• Generally paced with bitumen surface.•

• Class-C: Other minor road sand local roads connecting towns and other important in institutions.

• Width of carriage way-12ft.• Width of Platform-18ft.• Generally paved and bitumen surface.

• Class-D:Wideth of carriage way-10-18ft.• Gravel Roads.

• A highway is a public road, especially a major road connecting two or more destinations.

• Any interconnected set of highways can be variously referred to as a "highway system", a "highway network", or a "highway transportation system".

• Each country has its own national highway system. Major highways are often named and numbered by the governments that typically develop and maintain them.

• It can have several several lanes.

2.2.1.Highway System

2.3.Structure

• The structure of a Road consists of following components

• Formation or Sub grade• Sub Base.• Base.• The wearing surface.

2.3.1 .Formation /Sub grade

• This is the soil foundation which receives the traffic load.

• It forms the natural ground in its final shape on which the road structure rests.

• Ordinary soil is the best material for the road formation.

2.3.2.Sub grade

2.3.3. Sub base

• Sub base is constructed on the formation./sub grade.

• The main function of the sub base is to distribute the load of the traffic over the formation or sub grade in such a way that there will be no sinking of the road surface in to sub grade.

• Soiling and bottoming are two other terms used for sub grade in the construction industry.

•

2.3.4.Meterial Used.

• Broken rocks-4 inch size of rock spalls are suitable but larger sizes are required for subcases on soft or unreliable subgrades.

• Stones: Stones passing through 150 mm diameter ring for any directions and hard ,clean, and durable.

• Construction includes:• 1.Placing of the sub base• 2.Compaction of the sub base.

2.3.5.Sub base after formation

2.3.6.Base

• Base course is the layers immediately under the wearing surface.

• The base is subjected to heavy loading when ever traffic movement occurs.

• There for base should be should be constructed to withstand the effects of heavy loading.

• Construction includes.• 1.Laying the base• 2.Placing the base.• 3.Compaction of the base.

2.3.7.Meterial Used

• 2inch nominal size aggregates of approved quality.

• Crushed metal is widely used.

• The metal should be hard clean and durable.

• This can be selected after laboratory testing.

2.3.8.Formation of Road Base.

2.3.9.The Wearing Surface

• The Wearing Surface is the top surface of a road structure.

• The wheels of the passing vehicles come in to contact with the wearing surface.

• The purpose of the wearing surface will be.• 1.To provide a dust free surface over the base.• 2.Prevent entry of water in to the road structure.• 3.Prevent removal of materials of the base and sub base. • 4.Provide smooth riding surface.• 5.To resist abrasions and wearing

2.3.10.Meterial Used

• 1.Macadam bases:Macadem is small broken stones rolled in with some binding meterial.Several types are used for Road construction.

• 2.Tar: A viscous liquid , black in color with adhesive properties obtain by distillation of coal, wood or shale.

• 3.Bitumen;A viscous liquid, black or dark brown in color having adhesive properties. It is a by product obtained in petroleum crude oil refining.

• 4.Asphelt: Black substance use for roofing and road surfacing.

2.3.11.Wearing Surface

3.0.BRIDGES

• A Bridge is a structure built span physical obstacles such as body of water , valley or road for the purpose of providing passage over obstacle.

• Bridges are of various types and can be categorised mainly in to 5 types depending on structural principals.

• These 5 types of bridges are;

• 1.Arch Bridge• 2.Beam Bridge• 3.Cantiliver Bridge• 4.Cabale-stayed Bridge• 5.Suspension bridge

3.1.Arch Bridge

• An arch bridge is a bridge with abutments at each end shaped as a curved arch.

• Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side.\

• A viaduct (a long bridge) may be made from a series of arches, although other more economical structures are typically used today.

3.1.2.Structural Stability

3.1.3.Meterials for Construction.

• Arch bridges have been made of stones,bricks,cast iron, and steel.

• The largest are in steel and while some what smaller are in concrete.

• The oldest Arch Bridges are made out of masonry bricks and stones.

• Arch spans of Arch Bridges can varying from 200M to 550 m.

3.2.1.Beam Bridge

• Beam Bridges are the most simple structural forms being supported by on an abutment at each end of the deck.They are simply supported.

• Simplest beam bridge can be a plank placed a crossed a stream.

• Bridges design for modern infrastructure will usually be constructed of steel or concrete or of both.

3.2.2.Structural Stability

• Beam Bridge often simply rest on a support at each end ,allowing the ends to rotate slightly as the beam sags.

• But beam can be fixed at one end in the manner of a cantilever , or even at both ends.

• Where continues beam rests more than two supports the connections can be used to reduce the variation of bending moments through out the beam.

3.2.3.METERIAL USED

• Beam Bridges are often built with

• Reinforced Concrete• Pre Stressed Concrete• I-Beams• Plate Girders• Box Girders.

3.2.4.Cantilever Bridges

• A Cantilever bridge is a build by using cantilever structures that projects horizontally to the space.

• A cantilever is rather a bracket , projecting out into space.

• Most cantilever bridges have two cantilevers, with a beam suspended between their fee ends.

• Many Motorway bridges are built in this manner.• Spans can varies from minimum 250M to maximum of 550M

3.2.5.Structural Stability

3.2.6.Suspension Bridges

• A Suspension Bridge is a type of a Bridge in which Deck is hanging below suspension cables on vertical suspenders.

• This type of Bridge has cable suspended from Towers plus vertical suspendered cables that carry the weight of the Deck, which carry traffic.

• With the Deck high above the floppy cables, this looks unstable ,and it is.Therefore this construction can be used only for spans that are short enough for a stiff deck to transmit lateral forces to the anchorage.

3.2.7.Function of various parts

• The Towers hold the cable up.

• The Anchorage pull the cable outward and downward

• The hangers connect the Deck to the main cable.

• Deck is there to carry the traffic.

3.2.8.Structural Stability

3.2.9.CABLE-STAYED BRIDGE

• Cabal Stayed Bridge is a Bridge that consists of one or more cables supporting the Deck.

• It is related to the Cantilever Bridge .

• The spans can be constructed as cantilevers until they are joined at the center.

• The difference between Cantilever Bridge and Cable Stayed Bridge is the former usually have a suspended span and latter do not.

3.2.10.STRUCTURAL STABILITY

4.0.EARTH RETAINING STRUCTURES

• The basic function of a Earth Retaining structure is to retain soil at a slope which is greater than it would naturally assume, usually at a vertical or near vertical position.

• The natural slope taken up by any soil is called angle of repose and is measured in relationship to the horizontal.

• Angles of Repose changes from soil to soil.

• It ranges from 45-near 0 degrees in most soils and average angle usually considered as 30 degrees.

• It is It is the wedge of soil resting on this upper plane of angle of repose which has to be support.

• The supporting structures are known as Retaining walls.

4.1.Structral Stability

• Retaining Walls must be designed to ensure :

• Overturning does not occur.• Sliding does not occur.• The soil on which the wall rests is not

overloaded.• The material used in construction are not

overstressed.

4.2.Types of Retaining Walls.

• Mass Retaining walls• Cantilever walls• Pre Cast Concrete Retaining Walls.• Pre cast Concrete Crib Retaking walls

• When deciding the type of wall following factors will be considered.

• Nature of the Soil.• Height of water table • Subsoil water movement.• Material used in construction wall.

3.2.1. Gravity Retaining Walls

• Mass Retaining walls sometimes called Gravity Walls are relying upon their own mass together with the friction on underside of the base to overcome the tendency to slide or overturn.

• They are generally economic up to height of 1.8M.

• It will consists of mass concrete , generally without reinforcement.

Concrete Gravity Wall

Masonry Gravity Wall(Rubble)

Masonry Gravity Wall(Blocks)

4.2.2.Cantilever Walls

• Cantilever Walls are economical for height range of 1.2M to 6.0M.

• Two basic forms can be considered.

• 1.A base with a large heel so that mass of earth above can be added to the mass of the wall for design purposes.

• 2.Cantilever Wall with a large toe(If above type is not possible)

Wall with a large heel

Wall with toe

4.2.3.Pre Cast Concrete Retaining Walls

• Pre Cast Concrete module system consists of interlocking soil filled reinforced concrete modules which form a gravity wall.

• Manufactured from high grade pre cast concrete on the cantilever principal usually to 600 mm wide modules.

• They can be erected on a foundation as a permanent retaining wall or be free standing to act as a dividing wall between heaped materials such as aggregate foe concreate.

5.0.TUNNELS

• A Tunnel is an underground passageway ,completley enclosed except for opening at the each end.

• Purpose for Tunneling will be for:

• 1.Road Transport• 2.Railway Transport• 3.Conveyence of water• 4.Conveyance of Sewarage• 5.Access to Power Houses.

5.1.Types of Tunnels

• Hard Rock-Tunnels constructed through hard rock.

• Soft Rock-Tunnels constructed through clay.• Tunnels constructed through under water

• Shapes of Tunnels includes:• 1.Circuler-• 2.Horse Shoe• 3.Inverted-D

Circular Shape(to carry out liquids)

Horse Shoe(for transport)

5.2.Selection Criteria

• Location• Topography and access to portals.• Tunnel slope• Geology• Tunnel Selection• Economic Size.• Construction Cost.• Maintenance• Environment considerations

5.3.Construction Methodology

• Tunnels has to be constructed in Hard Ground as well as Soft Ground.

• The approach to construction is as follows.• 1.On Hard Grounds:• a).Drilling(using Boring machines)• B).Blasting(drilling holes and packing explosives to the

holes)• C)Mucking(removing the debris)

Drilling(or boring)

Blasting

Mucking(Hulage)

• On Soft Grounds:

• Excavation(workers dig soft ground through clay, silt, sand and gravel)

• Mucking(removing the debris)• Shield Advancement(to prevent caving of earth shield

to be pushed to the excavated area).• Erection of Tunnel Lining(installing permanent limning

by the workers)• Grouting.

SOFT GROUND BORING MACHINE

Tunnel Linning

6.0.DAMS

• Rivers can be fickle and dangerous.

• At one time , they may flow gently, at another time they may rise in flood destroying everything before them and leaving havoc in their wake.

• Dams controls such situations bring the rivers back to their old course , letting the water rise and pile up against the great walls.

• By creating additional storage of water, Dams can serve to generate electricity, supply water for agricultural lands

• .

6.1.Types of Dams

• Embankment Dams• Gravity/Concrete Dams• Arch/Concrete Dams

• One of the best place for building a is narrow part of the deep river valley.

• Dams required Spillways so that flow of water can be safely released down stream before water overflow the top of the Dam.

• Sluice Gates also have to built on to them to control the flood water.

6.1.2.Embankment Dams

• This type of Dams are constructed with compacted earth , rock, or both.

• More than 80% of large Dams are this type.

• These Dams are on its sheer weight to resist the pressure of the water behind it, and therefore very massive.\

• They need a special impervious core to make them water tight.

6.1.3.Gravity /Concrete Dams

• This types of Dams are used more often than Embankment type to provide hydro electrical power.

• The cross section of this types of Dams looks rectangular and the base is around ¾ of the height of the Dam.

• Building of Sluice gates are easier than in embankment type

6.1.4.Arch Concrete Dams

• Arch Dams are type of Dams that are curved and commonly built with concrete.

• It designed in such a manner that curve up stream so that the force of water against it press against the Arch , compressing and strengthening the structure as its pushes into foundation.

• This type of Dams are most suited for narrow gorges with steep walls with stable rock to support the structure.

• They are thinner than any other Dam type require much less concrete,

• An Arch Dam acts not only by its weight but also by transmitting the water pressure into a thrust against the abutments at either end.

• A Arch Dam stands a grave danger if the water in the reservoir seeps through the ground under it.

• All fissures are therefore sealed by cement injected through holes bored deep into the ground under Dam.

7.0.COFFERDAMS & CAISSONS

7.1.Cofferdams

• A coffer-dam is a watertight wall used to enclose the site of a work for the purpose of laying dry the foundation, as in the construction of sea-walls or the abutments and piers of bridges.

• A timber coffer-dam may consist of two or more rows of close piling, the space between the rows being filled in with well-punned clay, called "puddle."

• The thickness of the dam, or distance between the outer and inner rows of piles, will depend on the depth of the water to be resisted, and to some extent on the stiffness of the soil through which the piles of the dam are to be driven.

7.1.Timber Piled Coffer Dams

• The height at which the dam should stand above high water will depend on the situation; the more exposed it is, the higher will the dam be required; in ordinary cases 3 feet will be sufficient.

• Before commencing a coffer-dam it is usual to dredge out all the loose soil on the site, which if allowed to remain would admit water under the puddle.

• The ground being thus prepared, piles of whole timber, called " guide piles," are driven at intervals of about 10 feet apart, to mark out the form of the dam;

• Longitudinal timbers, formed of half baulks, called "walings," are then bolted on each side of the guide piles, one pair near the top, and another pair at about the level of low water. These serve the purpose of keeping in their places the intermediate piles, which may now be driven.

.• The rows of piles were tied together with iron bolts, which passed through the piles and wailings,

and were secured with large nuts and washer plates.

• .

7.2.Steel Sheeting Cofferdams

• Since the widespread adoption of sheet piling techniques after World War I, cofferdam construction has been guided by the '4 Ds':

• They are: Drive, Drain, Dig and Dismantle.

• First, sheet piling contractors are employed to drive sheet pile walls around the work site.

• Drainage systems are then employed to de-water the site before foundations are dug and laid.

• Once foundation construction and other works are complete, the site is filled and the cofferdam dismantled

7.3.CAISSONS

• A caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam.

• These are constructed such that the water can be pumped out, keeping the working environment dry.

• There are Three types of Caissons:

• Box Caissons• Open Caissons• Compressed air Caissons.

7.3.2.Box Caissons

• Box caissons are prefabricated concrete boxes with sides and bottom and are set down on prepared bases.

• Once in place they will be filled with concrete to become part of the permanent works, for example the foundation for a bridge pier.

• One problem with box caissons is that hollow concrete structures float and so they must be ballasted or anchored to prevent this until they can be filled with concrete.

• Adjustable anchoring systems combined with a GPS survey allow engineers to position a box caisson with pinpoint accuracy.

7.3.3.OPEN CAISSONS• Open caissons are similar to box caissons except that they do not have a bottom

face.

• They are suitable for use in soft clays (e.g. in some river-beds) but not for where there may be large obstructions in the ground.

• The open caissons may fill with water during sinking. The material is excavated by clamshell excavator bucket on crane. The caissons are sunk by self-weight, concrete or water ballast placed on top, or by hydraulic jacks.

• The leading edge of the caisson or "cutting shoe" is sloped out at a sharp angle (usually made of steel) to aid sinking in a vertical manner. The shoe is generally wider than the caisson to reduce friction and the leading edge may be supplied with pressurized betonies slurry (it swells in water to stabilize settlement or fill depressions/voids).

• The leading edge of the caisson or "cutting shoe" is sloped out at a sharp angle (usually made of steel) to aid sinking in a vertical manner. The shoe is generally wider than the caisson to reduce friction and the leading edge may be supplied with pressurized bentonite slurry (it swells in water to stabilize settlement or fill depressions/voids).

• A reinforced concrete plug is poured under the water known as a "tremie pour". This will act as a pile cap and resist the upward forces of subsoil once dewatered. The piles will act as bearing (transmitting load to deeper soils or friction along their surface length) and anchorage (resist floatation in the same manner).

7.3.4.Compressed Air Caissons

8.0.BEACH ATABILIZATION STRUCTURES

• Costal zone is a dynamic area of natural change and of increase of human use.

• Its occupies less than 15% of the earth land surface yet accommodate 50% of world population.

• Costal zone contains rich resources to produce goods and services and are home to most commercial and industrial activities.

• Costal erosion is the removal of beach or sand by wake of action and tidal currents.

• Waves generated by stromes,winds or fast moving motor crafts causes costal erosion.

• This justifyes the importance of Beach Stabilization Structures.• There are several methods used for this purpose and some

main methods are:• 1.Constructing of Groins and• 2.Nearshore Break Waters

8.1.Groins

• Groins controls the rate of long shore sand transport through a projected area and reduce the rate of sand lost alongshore .

• If properly design they are effective in stabilizing beaches where sand is lost by alongshore movement.

• They are relatively easy to construct using land based construction equipment and are relatively to inspect and maintain.

8.2.Nearshore Breakwaters

• Near shore breakwaters are effective shoreline stabilization structures that control along shore and off shore movement of sediment.

• They are segmental shore parallel structures built along the upper beach at approximately high water movement.

• They are normally built by rocks but can be found of concrete units as well.

• It reduces the energy of the waves reaching the shore lines .The structure act as direct barrier to waves, but at very high water level they allow some over falls.

• When oncoming waves hit these breakwaters ,their erosive power is concentrated on these structures some distance away from the coast.

• It can have a strong influence on long shore drifts.

• END OF FIRST SESSION