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