dynamic testing methods for grl - ohio department of ... · • cross-hole sonic logging (csl) •...
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GRLGRLDynamic Testing Methods for Evaluation of Integrity and Capacity for Drilled Shafts
Dynamic Testing Methods for Evaluation of Integrity and Capacity for Drilled Shafts
CSLCSL
PDAPDAPDA PITPITPIT
GRLGRLDeep Foundation Solutions:
• Driven Piles
• Steel, Concrete, Timber
• Drilled Shafts
• Wet or Dry, Cased or Uncased
• Augercast Piles
Each pile type has different inspection needs
Deep Foundation Solutions: Deep Foundation Solutions:
•• Driven PilesDriven Piles
•• Steel, Concrete, TimberSteel, Concrete, Timber
•• Drilled ShaftsDrilled Shafts
•• Wet or Dry, Cased or Wet or Dry, Cased or UncasedUncased
•• AugercastAugercast PilesPiles
Each pile type has different Each pile type has different inspection needsinspection needs
GRLGRLPlanned inspection • Included in project specifications
• Planned costs - normal pay item
Unplanned inspection• in response to something gone wrong
• Unplanned costs - who pays?
• Delays project, extra claims
Planned inspection Planned inspection •• Included in project specificationsIncluded in project specifications
•• Planned costs Planned costs -- normal pay itemnormal pay item
Unplanned inspectionUnplanned inspection•• in response to something gone wrongin response to something gone wrong
•• Unplanned costs Unplanned costs -- who pays?who pays?
•• Delays project, extra claimsDelays project, extra claims
( Preferred )( Preferred )( Preferred )
GRLGRL
Low Strain Integrity MethodsLow Strain Integrity MethodsLow Strain Integrity Methods
• PILE INTEGRITY TESTING (PIT) • Measure Pile Top Motion, Reflections from Defects• For concrete piles, concrete filled pipes, drilled
shafts, augercast piles, and sometimes timber piles.
• CROSS-HOLE SONIC LOGGING (CSL)• Determines Concrete Quality Between Tubes in Shaft• For drilled shafts and larger augercast piles
•• PILE INTEGRITY TESTING (PIT) PILE INTEGRITY TESTING (PIT) •• Measure Pile Top Motion, Reflections from DefectsMeasure Pile Top Motion, Reflections from Defects•• For concrete piles, concrete filled pipes, drilled For concrete piles, concrete filled pipes, drilled
shafts, shafts, augercast augercast piles, and sometimes timber piles. piles, and sometimes timber piles.
•• CROSSCROSS--HOLE SONIC LOGGING (CSL)HOLE SONIC LOGGING (CSL)•• Determines Concrete Quality Between Tubes in ShaftDetermines Concrete Quality Between Tubes in Shaft•• For drilled shafts and larger For drilled shafts and larger augercast augercast pilespiles
GRLGRLPile Integrity Testing…... looks for major defects
Pile Integrity Testing…... looks for major defects
Small hammer impact device Accelerometer
measures response
(defect)
ASTM D5882ASTM D5882
GRLGRL
Local Defect: small medium large
Local Bulge: small medium large
PIT - Basic InterpretationsPIT PIT -- Basic InterpretationsBasic Interpretations
GRLGRLNormal test (pile top “free”)
800 mm drilled shafts800 mm drilled shafts
L = 25 m (L/D = 31)L = 25 m (L/D = 31)
Good PileGood Pile
Bad PileBad Pile
GRLGRL
14 inch 14 inch augercastaugercast pile with 15 foot rebars.pile with 15 foot rebars.
Failed static load testFailed static load test often prompts testing.often prompts testing.Defect in this test pile shaft caused failed test Defect in this test pile shaft caused failed test
(rather than soil failure) (rather than soil failure)
GRL#994034
Test Pile
DefectDefect
GRLGRLPIT detected bored pile defect at 4.1 m depth; PIT detected bored pile defect at 4.1 m depth; confirmed by coreconfirmed by core
GRLGRL
Good pile with local bulge at about 25 ft and clear toe
Bulge- / + cycle
Bad pile with major defect at about 3.5 ft and no clear toe
Neck+ / - cycle
Bad pile excavated to reveal neck
GRLGRLClassifications(4 categories proposed by GRL)
Classifications(4 categories proposed by GRL)
•• A A -- Good PileGood PileClear toe response, no obvious defect; sound shaftClear toe response, no obvious defect; sound shaft
•• B B -- Bad PileBad PileClear identification of serious defect; Clear identification of serious defect; no toe signal no toe signal
–– needs contingency tests or corrective measuresneeds contingency tests or corrective measures
•• C C -- Possible DefectPossible Defect–– rere--test, other tests, reduce capacity or replacetest, other tests, reduce capacity or replace
•• D D -- Inconclusive dataInconclusive data(poor pile top quality, (poor pile top quality,
or no reflections due to strong soil)or no reflections due to strong soil)–– fix pile top & refix pile top & re--test; might give test; might give info info for upper pile shaft for upper pile shaft
which is reason to accept pile.which is reason to accept pile.
GRLGRL
•• Compare with other observations Compare with other observations
•• ReRe--test with PIT (trim pile top to solid concrete)test with PIT (trim pile top to solid concrete)•• Excavate if near topExcavate if near top•• Request pile coreRequest pile core•• Request a PDA test or a static testRequest a PDA test or a static test•• Replace pile (or repair)Replace pile (or repair)•• Other?Other?
•• Have a planHave a plan what to do if find a defectwhat to do if find a defect
What to do if find a “problem” ?What to do if find a “problem” ?
GRLGRL
•• Some studies suggest a 30 L/D Some studies suggest a 30 L/D limit.limit.Actually this is only a “rule of thumb” andActually this is only a “rule of thumb” anduseable length depends on:useable length depends on:
–– soil strength,soil strength,–– pile uniformity,pile uniformity,–– actual diameter and length,actual diameter and length,–– and equipment noise and resolution.and equipment noise and resolution.
•• We often see much fartherWe often see much farther
PIT LimitationsPIT Limitations
•• Highly nonHighly non--uniform piles difficult to interpretuniform piles difficult to interpret•• Cracks or mechanical joints block wavesCracks or mechanical joints block waves•• Small defects (or of short length) hard to findSmall defects (or of short length) hard to find•• Gradual changes hard to findGradual changes hard to find
GRLGRLPIT ConclusionsPIT ConclusionsPIT Conclusions
• PIT finds major defects, low cost so can test every pile
• Inclusion of inspection requirements in job specifications is suggested
• PIT can sometimes test piles in structure
• Guideline of use till 30 L/D is not a limit.
• Cracks or gaps limit transmission of wave
• No information about capacity
•• PIT finds PIT finds major defectsmajor defects, , low cost so can test every pilelow cost so can test every pile
•• Inclusion of inspection requirements in Inclusion of inspection requirements in job specifications is suggestedjob specifications is suggested
•• PIT can sometimes test piles in structurePIT can sometimes test piles in structure
•• Guideline of use till 30 L/D is not a limit. Guideline of use till 30 L/D is not a limit.
•• Cracks or gaps limit transmission of waveCracks or gaps limit transmission of wave
•• No information about capacity No information about capacity
GRLGRL
Stress Waves, emitted Stress Waves, emitted in one tube are receivedin one tube are received
in another one if concretein another one if concretequality is satisfactoryquality is satisfactory
ReceiveReceiveTransmitTransmit
Cross Hole Sonic Logging
ASTM D6760
Cross Hole Sonic LoggingCross Hole Sonic Logging
ASTM D6760ASTM D6760
GRLGRLCross Hole Sonic Logging
GRLGRL
SignalSignal
(wave speed) = ( tube distance ) / (arrival time )(wave speed) = ( tube distance ) / (arrival time )
Arrival
Energy
Cross Hole Sonic Logging
Arrival
Arrival
GRLGRL
DefectDefect
DefectDefect
DefectDefect
How do we spot defects?How do we spot defects?Low energyLow energyLate arrivalsLate arrivals
Cross Hole Sonic Logging
GRLGRL48” shaft with soft toe condition48” shaft with soft toe condition
GRLGRLShaft with tremie defect
GRLGRL
•• insensitive to surrounding soil or pile lengthinsensitive to surrounding soil or pile length
•• finds multiple defects, depth and quadrantfinds multiple defects, depth and quadrant
•• finds “soft bottoms” if tubes go to bottomfinds “soft bottoms” if tubes go to bottom
•• inspires careful construction by contractorinspires careful construction by contractor
CSL Testing AdvantagesCSL Testing Advantages
GRLGRL
•• must plan and install access tubesmust plan and install access tubes
•• tubes preferably less than 2 meters aparttubes preferably less than 2 meters apart
•• evaluates concrete only between tube pairsevaluates concrete only between tube pairs
•• defects undetected when outside cagedefects undetected when outside cage
CSL Testing LimitationsCSL Testing Limitations
GRLGRLCSL ConclusionsCSL ConclusionsCSL Conclusions• Can find multiple defects and their quadrant;
not sensitive to pile length or soil
• CSL finds defects between (steel) access tubes; consider defect remedy in advance
• CSL access tubes in every shaft inspires high quality installation for every shaft
(even if do not test every shaft)
• Allows low cost testing access if problems occur during installation
• Waterfall, FAT and energy compliment interpretation of results
•• Can find multiple defects and their quadrant; Can find multiple defects and their quadrant; not sensitive to pile length or soilnot sensitive to pile length or soil
•• CSL finds defects between (steel) access tubes; CSL finds defects between (steel) access tubes; consider defect remedy in advanceconsider defect remedy in advance
•• CSL access tubes CSL access tubes in every shaftin every shaft inspires inspires high quality installation for every shaft high quality installation for every shaft
(even if do not test every shaft)(even if do not test every shaft)
•• Allows low cost testing access if problems occur Allows low cost testing access if problems occur during installationduring installation
•• Waterfall, FAT and energy compliment Waterfall, FAT and energy compliment interpretation of resultsinterpretation of results
GRLGRL
The EndThe End