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High Strain Pile Testing with the Pile Driving Analyzer System® (PDA)and CAPWAP®

PDA Wave Mechanics 1

Outline

• Introduction– Measurement Evaluation– Forces and Stresses in Pile– Integrity– Bearing capacity– Examples

• Summary • Problems


Measuring strain and accelerationat one point

Strain transducer AccelerometerPDA Wave Mechanics 3

Alternative force transducer or F=ma

For F=ma or top load cell testing, accelerometers must

be attached to pile top.


PDA testing and data acquisitionPDA testing and data acquisition

After securely attaching sensors to pile, it is important to input the pertinent and latest calibration values in PDA


Measurements on a follower, nearshore


The Pile Driving Analyzer - Model 8G

• Measures force and velocity, usually near the pile top, but also at other locations such as the pile toe.

• Determines Case Method resistance, iCAP®, energy transferred to pile and stresses in pile

PDA and CAPWAP 7

Site Link® for Remote MonitoringReduces travel cost and scheduling problems

Site Link® for Remote MonitoringReduces travel cost and scheduling problems

PDA and CAPWAP 8

Acceleration and Strain vs. TimeAcceleration and Strain vs. Time

Accelerometers, one on each side; acceleration, velocity, displacement

Strain Transducers, one on each side; yield strain, stress and average force


●

Compressive stresses, forces: FMX, CSX, CSI


●CSX = 233 MPa (33.8 ksi)FMX = 1280 kN

●CSX = 233 MPa (33.8 ksi)FMX = 1280 kN

●

● ●CSI = 245 MPa (35.5 ksi)

For H-piles, Load Cell or F=ma Measurements: no CSI


Compressive stresses, forces: FMX, CSX, CSI

Force, Velocity, DisplacementForce, Velocity, Displacement

FMX

DMX = ½ max (d1 + d2)

DFN = ½ (d1 fin + d2 fin)

d2(t) = ∫v2(t) dt

d1(t) = ∫v1(t) dt

d1 max


d1 fin

d2 fin

Pile top force and velocity from PDAPile top force and velocity from PDA

We are measuring the total force and the total velocityWe plot both together using Z to scale velocity

We are measuring the total force and the total velocityWe plot both together using Z to scale velocity

F(t) = ½ A E [ε1(t) + ε2(t)]

v(t) = ½ [v1(t) + v2(t)] Z


Fu = - vu (EA/c)Fu = - vu (EA/c)

u = - vu (E/c)u = - vu (E/c)

εu = - vu / cεu = - vu / cεd = vd / cεd = vd / c

d = vd (E/c)d = vd (E/c)

Fd = vd (EA/c)Fd = vd (EA/c)

If wave travels “downwards”

If wave travels “upwards”


Superposition of WavesSuperposition of Waves

Fd=ZvdFd=Zvd

Downward Waves

Fu=-ZvuFu=-Zvu

Upward Waves

F = Fd + Fu

v = vd + vuPDA Wave Mechanics 15

Wave Down and Wave Up from F and Zv

Fd=½(F+Zv) Fu=½(F-Zv)

Fd or Wd; Fu or Wu

Fd1 or Wd1

Fd2 or Wu2


If we know wave up and wave downWe can calculate

Pile forces at other locations

If we know wave up and wave downWe can calculate

Pile forces at other locationsThe force at any point along the pile length can be determined from the superposition of the forces in

the upward traveling and downward traveling waves

The force at any point along the pile length can be determined from the superposition of the forces in

the upward traveling and downward traveling waves

F = Fu + FdF = Fu + Fd


L

2L/ct = 0 L/c

Upward

Wave

Upward

Wave

Downward

Wave

Downward

Wave

Wave Superposition for Force below SensorsWave Superposition for Force below Sensors

X

Fd1

Fu2

Fx = Fu2 + Fd3

Fd3

2x/c


TopToe

t3

Tension Stress Calculation – Wave-UpTension Stress Calculation – Wave-Up

Point of max tensionmin Fu

min Fu


Pile Damage: BTA, LTD

LTD

•A reduction of pile impedance (Z) above the pile toe causes a tension reflection before 2L/c•The time at which the tension reflection arrives at the gage location indicates the depth to Z-reduction: LTD = (tdamage / 2) c

•The magnitude of the Z-reduction is calculated with the -formula


t1

t3

Fu,1 = ½(Ft3-Zvt3)

Fd,1 = ½(Ft1+Zvt1)

Damage Example


PDA Capacity Monitoring

The 1965 (Phase 1) equation was based on a rigid body model: Ru = F(to) - mp a(to)

Time to is time of zero velocity – no damping

to


But then we derived the 1968 Case Method

Resistance WavesL/c

L

x

Ri

-½Ri

RB

RB

Upward traveling wave at time 2L/c:Fu,2 = -Fd,1 + ½Ri + ½Ri + RB

RTL = Fu,2 + Fd,1

Fd,1

-Fd,1

½Ri


½Ri

RD = Jv vtoe = Jc Z vtoeRD = Jv vtoe = Jc Z vtoe

Calculated Damping Component

The Case Methoduses the pile toe velocity for damping calculations; it is

affected by shaft and toe soil resistance!

Calculated Damping Component

The Case Methoduses the pile toe velocity for damping calculations; it is

affected by shaft and toe soil resistance!


Jv … viscous damping factor [kN/m/s]Jc … the dimensionless Case Damping Factorvtoe = (2Fd1 – RTL)/Z based on wave mechanics

Case Method Static Resistance

Rstatic= RTL - RD

Rstatic= Fu,2 + Fd,1 - Jc(2 Fd,1 – Fd1 – Fu,2)

Rstatic= (1 – Jc)Fd,1 + (1 + Jc )Fu,2

Total Resistance = Static + Dynamic ResistanceTotal Resistance = Static + Dynamic Resistance


Fd,1 = 5,450 kN

Fu,2 = 2,730 kN

Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2

RTL = 5,450 + 2,730 = 8,180 kN

For example with Jc= .3

Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kN

RTL = 5,450 + 2,730 = 8,180 kN

For example with Jc= .3

Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kNPDA Wave Mechanics 27

Maximum Case Method Resistance, RXiMaximum Case Method Resistance, RXi

t1 t2

2L/c

Calculates Rstaticat all times after the first velocity peak

Selects the maximum Rstaticfor JC= 0.i

Calculates Rstaticat all times after the first velocity peak

Selects the maximum Rstaticfor JC= 0.i


Shaft and Toe Resistance2L/ct = 0 L/c

L

x

R-½R

RB

½R

RB

Fd,1 -Fd,1

½R


Ri - Wave upRi - Wave upR

½R


An Example: PDA Capacity ResultsEnd of Driving


PDA Capacity ResultsRestrike; Blow No. 1


Restrike Blow No. 2


Restrike, blow No. 4


PEBWAP for and End Bearing Pile20x0.5” OEP; LG = 22.3 m; D46-32; 0.6 mm/bl; JC = 0.3

0

1500

3000

4500

6000

7500

0 5 10 15

Res

ista

nce

-kN

Toe Displacement - mm

Total Resistance Static Resistance

Static Resistance = Total Resistance – Damping Factor * Toe Velocity

PDA and CAPWAP 35

THE CAPWAP METHODTHE CAPWAP METHOD

1 Set up pile and soil model and assume

Rshaft and Rtoe

1 Set up pile and soil model and assume

Rshaft and Rtoe

Rshaft

Rtoe

5 If no satisfactory match: Go to Step 25 If no satisfactory match: Go to Step 2

4 Adjust Rshaft and Rtoe4 Adjust Rshaft and Rtoe

3 Compare WUC with measured WUM3 Compare WUC with measured WUM

2 Apply measured WDM to pile model at top and calculate complementary WUC

2 Apply measured WDM to pile model at top and calculate complementary WUC

WUM

WDM

WUC

PDA and CAPWAP 36

First try (poor)

Final match (good)

Adjustments

CAPWAP is an Iterative Process

PDA and CAPWAP 37

Seg. i∆Li

Ri

Fdoi

Fdni

Funi

Fuoi

Rdi

Rui

The Pile is divided in Np

uniform pile segments of approximately 1 m length.

Segment lengths are chosen for equal time increment

∆t = ∆Li/ci.

Each Segment has:

impedance Zi,,= EiAi/ci ,

mass mi = Zi ∆t and

stiffness ki = Zi/∆t .

The Pile Model

PDA and CAPWAP 38

The Combined CAPWAP Pile and Soil ModelThe Combined CAPWAP Pile and Soil Model

Soil segment length:LSi = Nfac Li

Soil segment length:LSi = Nfac Li

Spring (static resistance)Dashpot (dynamic resistance)

Spring (static resistance)Dashpot (dynamic resistance)

t

t

t

t

t

t

t

Pile Model:

Impedance Zi

= EiAi/ci

Pile Segment Length Li

Wave Travel time in Pile t = Li/ci

Pile Model:

Impedance Zi

= EiAi/ci

Pile Segment Length Li

Wave Travel time in Pile t = Li/ci

PDA and CAPWAP 39

Rui, qi

Rt, qt

Ji

JT Shaft Resistance,Ns times

Shaft Resistance,Ns times

tG

The Basic

CAPWAP

Soil Model

The Basic

CAPWAP

Soil Model

End Bearing

End Bearing

PDA and CAPWAP 40

mt

Rui, qi

Rt, qt

Ji

JT

JSK

JBT

Add Radiation DampingInertia Resistance

Add Radiation DampingInertia Resistance

tG

ms

mPL

Some CAPWAP

Soil ModelExtensions

Some CAPWAP

Soil ModelExtensions

mSP

PDA and CAPWAP 41

Signal Matching ExampleSignal Matching Example

PDA and CAPWAP 42

First Trial Analysis (Lousy Match)First Trial Analysis (Lousy Match)

Input F

Matching F

Input F

Matching v

or

Input v

Matching F

or

PDA and CAPWAP 43

Working with Wave-UpWorking with Wave-Up

RU = 782 kips

RT = 68 kips

JS/JT = .05/.15 s/ft

(JCS/JCT = .75/.22)

QS/QT = .10/.12”

RU = 782 kips

RT = 400 kips

RU = 782 kips

RT = 600 kips

RU = 782 kips

RT = 705 kips

JS/JT = .45/.02 s/ft

QS/QT = .10/.12”

PDA and CAPWAP 44


RU/RT = 782/705 kips

JS/JT = .45/.02 s/ft

(JCS/JCT = .75/.22)

QS/QT = .10/.12”


JS/JT = .30/.05 s/ft

(JCS/JCT = .50/.76)


JS/JT = .29/.05 s/ft

(JCS/JCT = .50/.76)

Prev.

PDA and CAPWAP 45



JS/JT = .29/.05 s/ft

(JCS/JCT = .50/.76)


JS/JT = .28/.06 s/ft

(JCS/JCT = .48/.82)


JS/JT = .26/.07 s/ft

(JCS/JCT = .44/.97)

QS/QT = .06/.12”

Unloading Parameters

Pretty good match: let’s quitPretty good match: let’s quitPDA and CAPWAP 46

CAPWAP Help FeaturesCAPWAP Help Features

HC

CAPWAP Variable Help

HC

CAPWAP Variable Help

HR

CAPWAP Resistance

vs Displacement Help

HR

CAPWAP Resistance

vs Displacement Help

PDA and CAPWAP 47

CAPWAP’s Static Pile and

Soil Model

CAPWAP’s Static Pile and

Soil Model

kshaft, I = Ru,i/qi

ktoe, i

Ru, i

kp, i

Rtoe, i

Qu1

utoe

PDA and CAPWAP 48

CAPWAP Static AnalysisCAPWAP Static Analysis

The final static load displacement curve is from a t-z and q-z analysis

The final static load displacement curve is from a t-z and q-z analysis

PDA and CAPWAP 49

CAPWAP Static Analysis Options

CAPWAP Static Analysis Options

Smoothing

User Capacity

Uplift Test

Extrapolation

Failure Criteria

Smoothing

User Capacity

Uplift Test

Extrapolation

Failure Criteria

PDA and CAPWAP 50

Standard OutputStandard Output

PDA and CAPWAP 51

Comprehensive CAPWAP ReportComprehensive CAPWAP Report

• “Blow Count” isfrom Direct Input inCAPWAP or fromPDA-W

• “Job Information”provides for otherinformation input

EX1; BENT 17-2; Pile: EX-1 Test: 04-Sep-1991 16:15:D36-23; silt; 16"PSC; Blow: 1171 CAPWAP(R) 2013Beta Version - Pile Dynamics OP: xxx yyyy

Analysis: 28-May-2013

-2500

0

2500

5000kN F Msd

V*Z Msd

5 105 ms

-600

0

600

1200kN

15 L/c

Wup MsdWup Cpt

Pile Type: SteelPile Size: 12 H Pile

Pile Installed: 03-Mar-2013 13:04CAPWAP Capacity: 2677.1 (kN)

at Toe: 376.1 (kN)Set at Yield: 16.897 (mm)Blow Count: 200 b/m

Length: 22.0 (m)Length Bl. gage: 21.9 (m)

Penetration: 21.0 (m)Inclination: 10 (degree)

Hammer: Delmag:D36-23Rated E: 119.3 (kJ)

Transfered E: 30.9 (kJ)Max C Stress Top: 26.2 (MPa)Max C Stress Pile: 26.7 (MPa)Max Ten. Stress: -0.89 (MPa)

0 750 1500 2250 30000.0

7.0

14.0

21.0

28.0

Load (kN)

Displacement (mm)

0.00

5.00

10.00

15.00

20.00

25.00

Depth below Grade (m)

Sand

Sand

Clay

Sand

SPT Nbl/30cm

66

qukPa1000.0

CAPWAPkPa160.0

SoilDescription

Blow Countb/m

221

PDA and CAPWAP 52

EX2; CLARK; SOFT-ROCK; Pile: EX-2 Test: 02-Jun-1993MKT DE 70B, HP 14 X 89; Blow: 627 CAPWAP® 2003-1GRL Engineers, Inc.

CAPWAP FINAL RESULTS

Total CAPWAP Capacity: 764.6; along Shaft 79.5; at Toe 685.1 kips

ft ft kips kips kips kips/ft ksf s/ft in

764.61 6.7 4.2 2.0 762.6 2.0 0.30 0.06 0.255 0.0602 13.5 11.0 1.0 761.6 3.0 0.15 0.03 0.255 0.0603 20.2 17.7 1.0 760.6 4.0 0.15 0.03 0.255 0.0604 26.9 24.4 1.0 759.6 5.0 0.15 0.03 0.255 0.0605 33.7 31.2 2.0 757.6 7.0 0.30 0.06 0.255 0.0606 40.4 37.9 3.0 754.6 10.0 0.45 0.10 0.255 0.0607 47.1 44.6 4.0 750.6 14.0 0.59 0.13 0.255 0.0608 53.8 51.3 18.6 732.0 32.6 2.76 0.59 0.255 0.0609 60.6 58.1 1.0 731.0 33.6 0.15 0.03 0.255 0.06010 67.3 64.8 1.0 730.0 34.6 0.15 0.03 0.255 0.06011 74.0 71.5 1.0 729.0 35.6 0.15 0.03 0.255 0.06012 80.8 78.3 4.9 724.1 40.5 0.73 0.16 0.255 0.06013 87.5 85.0 39.1 685.1 79.5 5.80 1.24 0.255 0.060

Avg. Skin 6.1 0.94 0.19 0.255 0.060

Toe 685.1 503.31 0.066 0.120

Soil Model Parameters/Extensions Skin Toe

Case Damping Factor 0.437 0.971Unloading Quake (% of loading quake) 99 100Reloading Level (% of Ru) 100 100Unloading Level (% of Ru) 78

CAPWAP match quality: 2.88 (Wave Up Match)Observed: final set = 0.050 in; blow count = 240 b/ftObserved: final set = 0.009 in; blow count = 1323 b/ft

Summary Table Output

Summary Table Output

Ri, qi, Ji

PDA and CAPWAP 53

EX2; CLARK; SOFT-ROCK; Pile: EX-2 Test: 02-Jun-1993MKT DE 70B, HP 14 X 89; Blow: 627 CAPWAP® 2003-1GRL Engineers, Inc.

EXTREMA TABLE

Pile Dist. max. min. max. max. max. max. max.Sgmnt Below Force Force Comp. Tens. Trnsfd. Veloc. Displ.No. Gages Stress Stress Energy

ft kips kips ksi ksi kip-ft ft/s in

1 3.4 586.4 -24.4 22.549 -0.937 23.53 11.7 0.7382 6.7 588.7 -24.1 22.635 -0.927 23.40 11.6 0.7254 13.5 585.7 -22.1 22.520 -0.849 22.79 11.5 0.6996 20.2 587.3 -21.1 22.583 -0.810 22.30 11.4 0.6708 26.9 590.1 -19.6 22.691 -0.753 21.73 11.2 0.637

10 33.7 594.8 -18.4 22.870 -0.706 21.02 11.0 0.60011 37.0 592.6 -17.0 22.787 -0.653 20.42 10.9 0.57912 40.4 598.9 -17.2 23.029 -0.661 20.09 10.8 0.55913 43.8 596.6 -15.3 22.940 -0.590 19.39 10.6 0.53914 47.1 607.0 -16.4 23.339 -0.629 19.05 10.4 0.51815 50.5 602.3 -15.2 23.161 -0.585 18.21 10.2 0.49616 53.8 608.4 -15.4 23.393 -0.592 17.79 10.0 0.47317 57.2 568.4 -7.2 21.857 -0.276 15.45 9.9 0.44918 60.6 576.1 -17.7 22.152 -0.682 14.91 9.8 0.42319 63.9 589.0 -27.0 22.650 -1.039 14.16 9.7 0.39420 67.3 624.9 -35.8 24.028 -1.376 13.38 9.6 0.36321 70.7 668.4 -42.0 25.701 -1.613 12.39 9.4 0.32922 74.0 718.3 -48.2 27.622 -1.852 11.36 9.2 0.29323 77.4 756.7 -54.5 29.095 -2.095 10.14 8.8 0.25524 80.8 785.1 -61.7 30.188 -2.371 8.94 8.1 0.21625 84.1 793.0 -61.2 30.492 -2.355 7.59 6.8 0.17826 87.5 806.4 -63.8 31.007 -2.451 6.21 5.3 0.140

Absolute 87.5 31.007 (T = 27.2 ms) 87.5 -2.451 (T = 44.2 ms)

CASE METHOD

J = = 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9RS1 830.3 799.1 767.8 736.6 705.3 674.1 642.9 611.6 580.4 549.2RMX 862.6 839.8 821.8 808.3 795.0 782.0 769.8 757.8 745.7 733.7RSU 836.4 805.8 775.2 744.6 713.9 683.3 652.7 622.1 591.4 560.8

RAU= 595.0 (kips); RA2= 757.7 (kips)

Current CAPWAP Ru= 764.6 (kips); Corresponding J(Rs)= 0.21; J(Rx)=0.64

ft/s ft/s kips kips kips in in kip-ft kips 11.95 0.00 554.8 587.9 587.9 0.747 0.054 23.7 709.9

Numerical Output

Numerical Output

Case Method

Extrema

PDA and CAPWAP 54

TAMPA DRILLED SHAFT TESTING

PDA and CAPWAP 55

Instrumentation

PDA and CAPWAP 56

CAPWAP Results for several blows

0

5000

10000

15000

20000

25000

0 10 20 30 40

Displacement (mm)

Load

(kN

)

Toe Top

APE 750; 60 ton ram (2.4% of test load = 2470 tons). Four blows; 4.5 ft drop; 6 ft dia. shafts; (under pier) in limestonesee: Rausche, Likins, Hussein, (2008). GSP #180, ASCE

Proposed failure criterion for dynamic tests for the cumulative toe displacement: D/60

60 ton ram was 2.4% of failure load

2500 ton failure load

72” dia shaft; Cooper Marl

Large diameter shaft in soil

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 1000 2000 3000 4000 5000 6000

Pile

To

p D

isp

lace

men

t (i

n)

Pile Top Load (Kips)

Blow 3 = 2.5 FT Stroke Blow 4 = 4.0 FT Stroke

Blow 5 = 5.0 FT Stroke Elastic Line

PDA and CAPWAP 58

CAPWAP Comparisons with Static Load Tests – H-Pile

H-pile 14x73 (356 x 109);Penetration 45 mSoil: Silts and clays with N<15 for depths < 30 m, then clays and silts with 40<N<100 to 45 m.Hammer: D30-32EOD: 8 mm set/blowBOR: 5 mm set/blowEOR: 15 mm set/blow

0

500

1000

1500

2000

2500

0 20 40 60 80 100

Displacement (mm)

Lo

ad (

kN)

Top

Toe

SLT

CAPWAP 21-day Restrike (Blow 2): Ru=2060 kN; (Blow 25): Ru=1600 kNStatic Load Test (48 days): 2000 kN; Rausche, Likins, Hussein, 2008.

PDA and CAPWAP 59

Florida Drilled Shaft Florida Drilled Shaft

Diameter:

• to 20 ft (6.1m) 28” (710mm)

• to 44 ft (13.4m) 24” (610mm)

• Soil: Shaft: Sand

Toe: Soft Limestone.

• Hammer: 10 tons

Hussein et al., 1992

6.1 m

13.4 m

Toe 2

Toe

Shaft

Shaft

Note:

Toe 2 treatment much simplified in

CAPWAP 2014

PDA and CAPWAP 60

Florida Drilled Shaft: Class A Prediction Florida Drilled Shaft: Class A Prediction

• Required Rult:

1000 kips (4450 kN)

• Static and dynamic

tests indicate a

capacity less than

760 kips (3380 kN),

depending on criterion

3560 kN

• Offset Criterion yields

650 kips (2890 kN)

from static and

dynamic test.

PDA and CAPWAP 61

CAPWAP Correlation: Automatic ProcedureCAPWAP Correlation: Automatic Procedure

PDA and CAPWAP 62

CAPWAP Correlation:Radiation Damping Model

CAPWAP Correlation:Radiation Damping Model

PDA and CAPWAP 63

Combined Data Bases of GRL 1996and from Stress Wave Conferences

Mean: 0.98; COV: 0.17; N = 303

Likins and Rausche, 2004PDA and CAPWAP 64

CAPWAP Critique - iCAP Features

• CAPWAP is Non-unique?Just one result!

• CAPWAP is Slow?Real time result!

• CAPWAP needs Experience?Done by PDA Operator!

PDA and CAPWAP 65

iCAP Application• When?

– During Monitoring– During Restrike– During Reanalysis

• When Not?– When pile and/or soil properties are not well known– Problem data which lead to poor matches

• How?– Just turn it on

• Notes:– iCAP can be run directly from CAPWAP-2014 for non-

uniform piles– iCAP is no CAPWAP; differences must be expected;

review is recommended

66PDA and CAPWAP 66

Summary

• PDA Testing During Driven Pile installation, called monitoring, checks driving stresses, pile integrity, resistance at the time of testing

• Performing a resike test after waiting yields a dynamic load test.

• Case Method closed form measurements together with stress wave considerations yield information on – dynamic stresses

– pile integrity

– bearing capacityPDA Wave Mechanics 67

The EndQuestions?


The Second End

No more questions?


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