Right Way of PIT

7/26/2019 Right Way of PIT

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03/06/201

Right Way of PITRight Way of PIT

PIT is frequentlyPIT is frequently

specified to detectspecified to detect

defect on bored piles.defect on bored piles.


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03/06/201

Pile Integrity Testing looks for defectsPile Integrity Testing looks for defects

Small hammer

impact deviceAccelerometer

measures response

(defect)

PIT motivation and advantagesPIT motivation and advantages

prime function is to locateprime function is to locatemajormajor defectsdefects(to evaluate questionable shafts)(to evaluate questionable shafts)

inexpensive, can test many pilesinexpensive, can test many piles(good for quality assurance)(good for quality assurance)

no advance selection requiredno advance selection required(good for forensic purposes)(good for forensic purposes)


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03/06/201

Concerns:Concerns:

PIT is a useful tool when used properlyPIT is a useful tool when used properly

find major defects if they exist.find major defects if they exist.

If PIT used improperly, it can either:If PIT used improperly, it can either:

find defects that do not existfind defects that do not exist

not find defects that do existnot find defects that do exist

Bad diagnosis can lead to discredit of methodBad diagnosis can lead to discredit of method

Goal is to use PIT properlyGoal is to use PIT properly

This presentation presents proper useThis presentation presents proper use

(and also examples of what not to do).(and also examples of what not to do).


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03/06/201

SummarySummary

Time Domain analysisTime Domain analysis

Locate major defectsLocate major defects

Estimate profileEstimate profile

Frequency Domain analysisFrequency Domain analysis

Stiffness (must measure force)Stiffness (must measure force)

Question:Question:

How do we acquire data and process it soHow do we acquire data and process it so

that we can properly interpret it?that we can properly interpret it?

Question:Question:


that we can properly interpret it?that we can properly interpret it?


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03/06/201

Question:Question:


that then we can properly interpret it tothat then we can properly interpret it to

obtainobtain reliable conclusionsreliable conclusions??

Real data is not perfectReal data is not perfect

Imperfect pilesImperfect piles

pile top contact surface not smoothpile top contact surface not smooth

inhomogeneous materialinhomogeneous material

(modulus versus length)(modulus versus length)

inhomogeneous material (particle sizes)inhomogeneous material (particle sizes)

pile material dampingpile material damping

soil resistancesoil resistance


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Imperfect impactsImperfect impacts

spherical point contact versus plane wavespherical point contact versus plane wave

(pile not one dimensional)(pile not one dimensional)

protruding reinforcement ringsprotruding reinforcement rings

Rayleigh wavesRayleigh waves

long inputs versus short defectslong inputs versus short defects

Pile top clean and free of waterPile top clean and free of water


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Imperfect pilesImperfect piles

Imperfect impactsImperfect impacts

Imperfect sensorsImperfect sensors

coupling to pilecoupling to pile

Imperfect signal conditioningImperfect signal conditioning

external noiseexternal noise

internal noiseinternal noise

Imperfect processingImperfect processing

finite resolution in time and amplitudefinite resolution in time and amplitude


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03/06/201

Collect Several Blows of Data

No clear toe signal, need more data processing

Pile

Real data is not perfectnot perfect, so...

data enhancements play an

important part in evaluating low

strain integrity tests

Real data is not perfectnot perfect, so...

data enhancements play an

important part in evaluating low

strain integrity tests

Collect multiple blows:

averaging reduces random effects Use best possible equipment

low noise, high resolutionbest signal processing

Collect multiple blows:

averaging reduces random effects Use best possible equipment

low noise, high resolutionbest signal processing


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03/06/201

Pile Test Consultants ( PVT) LtdPile Test Consultants ( PVT) LtdPile Test Consultants ( PVT) LtdPile Test Consultants (PVT) Ltd 5/23 /201 65/23/20165/23/20165/23/2016

DPJ TATA 8,9DPJ TATA 8,9DPJ TATA 8,9DPJ TATA 8,9

K:\...\DPJ -TATA BULING\DPJ TATA 8,9. PITK:\...\DPJ -TATA BULING\DPJ TATA 8,9. PITK:\...\DPJ -TATA BULING\DPJ TATA 8,9. PITK:\... \DPJ -TATA BULING\DPJ TATA 8,9.PIT PIT-W 2 009-2PIT-W 2009-2PIT-W 2009-2PIT-W 2009-2

-0.08

0.00

0.08

0.16cm/s

V 0.126 cm/s (0.138)

Pile: P4 309- 3: # 1

12009/24/2015 4:42:05 PM

2W 1.84 m 950.0 Hz

0 4 8 12 16 20 24 m

x 5.00 L/D=14 (D=120 cm)

17.25 m (3500 m/s)

-0.15

0.00

0.15

0.30cm/s

V 0.205 cm/s (0.229)

Pile: P4 309- 2: # 2

1200

9/24/2015 4:42:22 PM

2W 1.84 m 950.0 Hz

0 4 8 12 16 20 24 m

x 5.00 L/D=14 (D=120 cm)

17.25 m (3500 m/s)

-0.03

0.00

0.03

0.06cm/s

V 0.056 cm/s (0.059)

Pile: P4 309- 3: # 3

1200

9/24/2015 4:42:31 PM

2W 1.84 m 950.0 Hz

0 4 8 12 16 20 24 m

x 5.00 L/D=14 (D=120 cm)

17.25 m (3500 m/s)

-0.03

0.00

0.03

0.06cm/s

V 0.059 cm/s (0.068)

Pile: P4 309- 3: # 5

12009/24/2015 4:43:27 PM

2W 2.00 m 875.0 Hz

0 4 8 12 16 20 24 m

x 5.00 L/D=14 (D=120 cm)

17.25 m (3500 m/s)

Velocity Records of a Sound PileVelocity Records of a Sound Pile

Clear ToeClear Toe

reflection isreflection is

visible.visible.

WS is with inWS is with in

the rangethe range

ToeToe

Reflection isReflection iscompressioncompression

TopTop BottomBottom

-0.02

0.00

0.02

0.04 cm/s

V 0. 037 cm/s (0. 039)

Pile: P4 3- 3: # 36

1000

10/11/2014 3:33:05 PM

2W 2.00 m 875.0 Hz

0 1 2 3 4 5 6 7 8 9 10 11 12 13 m

x 2.00 L/D=9.3 (D=100 cm)

9.35 m (3500 m/s)

-0.03

0.00

0.03

0.06cm/s

V 0. 039 cm/s (0. 040)

Pile: P4 3 - 3: # 37

1000

10/11/2014 3:33:10 PM

2W 2.00 m 875.0 Hz

0 1 2 3 4 5 6 7 8 9 10 11 12 13 m

x 2.00 L/D=9.3 (D=100 cm)

9.35 m (3500 m/s)

-0.01

0.00

0.01

0.03cm/s

V 0. 023 cm/s (0. 024)

Pile: P4 3 - 3: # 38

1000

10/11/2014 3:33:17 PM

2W 2.00 m 875.0 Hz

0 1 2 3 4 5 6 7 8 9 10 11 12 13 m

x 2.00 L/D=9.3 (D=100 cm)

9.35 m (3500 m/s)

-0.03

0.00

0.03

0.06cm/s

V 0. 034 cm/s (0. 036)

Pile: P4 3 - 1: # 39

1000

10/11/2014 3:33:21 PM

2W 2.00 m 875.0 Hz

0 1 2 3 4 5 6 7 8 9 10 11 12 13 m

x 2.00 L/D=9.3 (D=100 cm)

9.35 m (3500 m/s)

Velocity Records of a Pile Terminated on Soft MaterialVelocity Records of a Pile Terminated on Soft Material

Clear ToeClear Toe

reflection isreflection is

visible.visible.

WS is with inWS is with in

the rangethe range

ToeToe

Reflection isReflection is

tensiontension

Accepted OrAccepted OrRejected ?Rejected ?


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1

Velocity Records of a Pile with a BulgingVelocity Records of a Pile with a Bulging

-0.05

0.00

0.05

0.10cm/s

V 0.087 cm/s (0.090)

Pile: P-114- 2: # 18

600

3/17/20164:04:14 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D=37 (D=60 cm)

21.93 m (3800 m/s)

-0.06

0.00

0.06

0.12cm/s

V 0.104 cm/s (0.107)

Pile: P-114- 2: # 19

600

3/17/20164:04:28 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D=37 (D=60 cm)

21.93 m (3800 m/s)

-0.05

0.00

0.05

0.10cm/s

V 0.095 cm/s (0.100)

Pile: P-114- 2: # 20

600

3/17/20164:04:43 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D=37 (D=60 cm)

21.93 m (3800 m/s)

-0.08

0.00

0.08

0.16cm/s

V 0.139 cm/s (0.147)

Pile: P-114- 1: # 21

600

3/17/20164:05:30 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D=37 (D=60 cm)

21.93 m (3800 m/s)

-0.06

0.00

0.06

0.12cm/s

V 0.064 cm/s (0.066)

Pile: P-34- 3: # 1

600

3/17/2016 3:53:28 PM

2W 1.00 m 1900.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D =37 (D=60 cm)

22.00 m (3800 m/s)

-0.04

0.00

0.04

0.08cm/s

V 0.053 cm/s (0.053)

Pile: P-34- 3: # 2

600

3/17/2016 3:53:47 PM

2W 1.00 m 1900.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D =37 (D=60 cm)

22.00 m (3800 m/s)

-0.05

0.00

0.05

0.10cm/s

V 0.063 cm/s (0.064)

Pile: P-34- 3: # 3

600

3/17/2016 3:53:59 PM

2W 1.00 m 1900.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D =37 (D=60 cm)

22.00 m (3800 m/s)

-0.05

0.00

0.05

0.10cm/s

V 0.068 cm/s (0.070)

Pile: P-34- 3: # 4

600

3/17/2016 3:54:09 PM

2W 1.00 m 1900.0 Hz

0 5 10 15 20 25 30 m

x 5.00 L/D =37 (D=60 cm)

22.00 m (3800 m/s)

-0.08

0.00

0.08

0.16cm/s

V 0.119 cm/s (0.119)

Pile: P-38- 3: # 90

600

2/25/2016 2:05:21 PM

0 5 10 15 20 25 m

x 5.00 L/D=27 (D=75 cm)

20.24 m (3800 m/s)

-0.06

0.00

0.06

0.12cm/s

V 0.086 cm/s (0.091)

Pile: P-38- 3: # 91

600

2/25/2016 2:05:45 PM

2W 2.13 m 891.8 Hz

0 5 10 15 20 25 m

x 5.00 L/D=27 (D=75 cm)

20.24 m (3800 m/s)

-0.05

0.00

0.05

0.10cm/s

V 0.071 cm/s (0.076)

Pile: P-38- 3: # 95

600

2/25/2016 2:06:41 PM

2W 2.13 m 891.8 Hz

0 5 10 15 20 25 m

x 5.00 L/D=27 (D=75 cm)

20.24 m (3800 m/s)

-0.05

0.00

0.05

0.10cm/s

V 0.067 cm/s (0.071)

Pile: P-38- 3: # 96

600

2/25/2016 2:06:49 PM

2W 2.13 m 891.8 Hz

0 5 10 15 20 25 m

x 5.00 L/D=27 (D=75 cm)

20.24 m (3800 m/s)

Velocity Records of a Pile with a NeckingVelocity Records of a Pile with a Necking

-0.05

0.00

0.05

0.10cm/s

V 0.067 cm/s (0. 073)

Pile: P-67- 3: # 8

600

4/23/2016 1:54:05 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 m

x 5.00 L/D =34 (D=60 cm)

20.21 m (3800 m/s)

-0.08

0.00

0.08

0.16cm/s

V 0.088 cm/s (0. 097)

Pile: P-67- 2: # 10

600

4/23/2016 1:55:23 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 m

x 5.00 L/D =34 (D=60 cm)

20.21 m (3800 m/s)

-0.15

0.00

0.15

0.30cm/s

V 0.163 cm/s (0. 179)

Pile: P-67- 2: # 11

600

4/23/2016 1:55:39 PM

2W 2.00 m 950.0 Hz

0 5 10 15 20 25 m

x 5.00 L/D =34 (D=60 cm)

20.21 m (3800 m/s)

0.00

0.06

0.12cm/s

Pile: P-67- 3: # 12

600

4/23/2016 1:56:09 PM

2W 2.00 m 950.0 Hz

x 5.00 L/D =34 (D=60 cm)


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Velocity Records of a Pile having a BulgeVelocity Records of a Pile having a Bulge

followed by a Neckingfollowed by a Necking

-0.08

0.00

0.08

0.16cm/s

V 0.052 cm/s (0.053)

Pile: P 158 (PDL)- 3: # 28

750

11/11/2014 5:53:11 PM

2W 2.00 m 875.0 Hz

0 2 4 6 8 10 12 14 16 m

x 5.00 L/D =15 (D=75 cm)

11.42 m (3500 m/s)

-0.08

0.00

0.08

0.16cm/s

V 0.089 cm/s (0.098)

Pile: P 158 (PDL)- 3: # 27

750

11/11/2014 5:52:58 PM

2W 2.00 m 875.0 Hz

0 2 4 6 8 10 12 14 16 m

x 5.00 L/D =15 (D=75 cm)

11.42 m (3500 m/s)

-0.08

0.00

0.08

0.16cm/s

V 0.103 cm/s (0.116)

Pile: P 158 (PDL)- 3: # 26

750

11/11/2014 5:52:53 PM

2W 2.00 m 875.0 Hz

0 2 4 6 8 10 12 14 16 m

x 5.00 L/D =15 (D=75 cm)

11.42 m (3500 m/s)

Lets look at some more real data setsLets look at some more real data sets


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1

Defect

Coring

4x/c

Driven prestressed pileDriven prestressed pile (600mm cylinder w/ center void)(600mm cylinder w/ center void)

Seafloor at approx.Seafloor at approx. --10 m. Client asks interpretation.10 m. Client asks interpretation.

MDMDdelay?delay?

Fixed end (compression reflection):

massive concrete mat at seafloor,or pile broken (top jammed into bottom)

C@ 2x/c

T@ 4x/c

C@ 6x/c

T@ 8x/c


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Averaging several blows (reduce random noise)Averaging several blows (reduce random noise)

Magnification versus time (compensate for losses)Magnification versus time (compensate for losses)

High pass filtering (or pivoting)High pass filtering (or pivoting)(eliminate low frequencies; keeps data near zero)(eliminate low frequencies; keeps data near zero)

Wavelet filters (or low pass);Wavelet filters (or low pass);(eliminate high frequencies)(eliminate high frequencies)

Rayleigh wave correction (experimental)Rayleigh wave correction (experimental)

ConclusionsConclusions

Important!Important!

UseUse similar processingsimilar processing forfor similar pilessimilar piles inin similar soilssimilar soils..Compare results to spot unusual piles.Compare results to spot unusual piles.

Data processing usually includes:Data processing usually includes:

Interpretation looks for:Interpretation looks for:

Good data (consistent & reasonable)Good data (consistent & reasonable)

Similarity or differences for different pilesSimilarity or differences for different piles

Rapidly changing features in dataRapidly changing features in data

Toe signal (tension or compression)Toe signal (tension or compression)

Shaft uniformityShaft uniformity

Indications ofIndications of major defectsmajor defects (+/(+/-- cycle)cycle)

Comparison with soil profile, installation recordsComparison with soil profile, installation records

Integrity testing locatesIntegrity testing locates major defectsmajor defects. It is limited to. It is limited togeneral interpretations rather than exact detail. Do not usegeneral interpretations rather than exact detail. Do not useheroic effort to read more than data really tells.heroic effort to read more than data really tells.



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ClassificationsClassifications(4 categories proposed by GRL)(4 categories proposed by GRL)

AA -- Clear toe response, no obvious defect;Clear toe response, no obvious defect;

sound shaft (good pile)sound shaft (good pile)

BB -- Clear identification of serious defect;Clear identification of serious defect;

toe not apparent (bad pile)toe not apparent (bad pile)

needs contingency tests or corrective measuresneeds contingency tests or corrective measures

CC -- Possible shaft defectPossible shaft defect

rere--test, other tests, reduce capacity or replacetest, other tests, reduce capacity or replace

DD -- Inconclusive data (poor pile top quality,Inconclusive data (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 info for upper pile shafttest; might give info for upper pile shaft

which is reason to accept pile.which is reason to accept pile.

Compare with other observationsCompare 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 testRequest a PDA test

Request a Static TestRequest a Static Test

Replace pile (or repair)Replace pile (or repair) Accept pile (?)Accept pile (?) -- is pile in group? Critical?is pile in group? Critical?

Other?Other?

Each option has different associated costsEach option has different associated costs

What to do if find a problem ?What to do if find a problem ?


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Limitations:Limitations:

full cracks or manufactured jointsfull cracks or manufactured joints

L/D ratio (high soil resistance) ,L/D ratio (high soil resistance) ,

multiple defects or highly variable shaftsmultiple defects or highly variable shafts

small defect size or short lengthsmall defect size or short length

gradual changes hard to detectgradual changes hard to detect

wave speed (length) accuracy plus or minuswave speed (length) accuracy plus or minus

12.5%12.5%

Integrity testing equipment should be low noise and highIntegrity testing equipment should be low noise and highresolution to extract the most information.resolution to extract the most information. Not allNot allequipment is sufficient for the task.equipment is sufficient for the task.

Studies suggested a 30 L/DStudies suggested a 30 L/D limitlimit based on old equipment.based on old equipment.Limit depends on soil strength, pile uniformity, pileLimit depends on soil strength, pile uniformity, pilediameter, and equipment resolution.diameter, and equipment resolution.



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Integrity testing isIntegrity testing is not applicable to ALL situationsnot applicable to ALL situations.. Do notDo notassure results and even try to discourage use in obviouslyassure results and even try to discourage use in obviouslyunusual conditions, or at least inform client of lowunusual conditions, or at least inform client of lowpossibility of success.possibility of success.

Because integrity testing has several limitations, integrityBecause integrity testing has several limitations, integritytesting professionals will question test if it seemstesting professionals will question test if it seemsuncertain (inconclusive data).uncertain (inconclusive data).

Impossible to predict load capacity by low strain PIT. AtImpossible to predict load capacity by low strain PIT. Atbest, gives relative stiffness from mobility analysis.best, gives relative stiffness from mobility analysis.


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Right Way of PIT