right way of pit
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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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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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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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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:
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?
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Question:Question:
How do we acquire data and process it soHow do we acquire data and process it so
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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Real data is not perfectReal data is not perfect
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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Real data is not perfectReal data is not perfect
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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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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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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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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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.
ConclusionsConclusions
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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.
ConclusionsConclusions
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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.
ConclusionsConclusions
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