2. Pile Testing Methods - Pile Driving Contractors Association · 2013-07-022. Pile Testing Methods...

2013

Frank Rausche

Pile Dynamics, Inc.

The Case Method and the

Pile Driving Analyzer® (PDA)

Outline

• Testing Objectives

• Hardware

– Standard

– Wireless testing

– Remote testing

• Methods

– Stresses

– Integrity

– Capacity

• Examples

• Summary

PDPI June 2013 – Case Method 2

Testing Objectives: Economical Load Testing D

yna

mic

Tes

tin

g

Sta

tic

Test

ing


Testing Objectives: Installation Monitoring Stresses, Integrity, Resistance, Energy (Case Method)


Basically We

Have to Measure

Pile Top Force and

Velocity

and Process Data with the

Pile Driving Analyzer®


Measuring Strain and Acceleration (need to do it on opposite pile sides)

Strain transducer Accelerometer


PDA testing data acquisition

• Need Minimum 2 strain measurements per pile to

compensate for bending


Mounting the sensors


Measurements on cylinder piles


Wireless testing components using

smart sensors

Transmitter


Strain and Acceleration Sensors

PDPI June 2013 – Case Method

Wir

ele

ss

Un

der

Wate

r

11

Sensor Installation/Protection

H-piles Pipe piles


Lofting pile into leads

PDA


Concrete Piles


Smart and Wireless Sensors

Make for Happy Testers


SiteLink and Wireless Testing


PAX - SiteLink Connect Operation

• PDA is being operated by office engineer

• Office computer acts as a remote keyboard and monitor

• PAX is used with PDA-L

• Data resides on PAX until downloaded


• No traveling/scheduling cost/delays/issues

• Immediate analysis and quick report submittal

• Increased efficiency of test engineer

• Remote supervision of inexperienced personnel avoids errors

SiteLink Advantages


Measurements on a follower, nearshore


Basic Strain and Acceleration Measurements

ε1(t), ε2(t), one strain on each side

a1(t), a2(t), one acc. on each side


Standard Presentation

F = ½ (S1 + S2 ) (EM * AR)


v = ½ ∫(a1 + a2 ) dt

Fu = ½ (F - vZ)

Fd = ½ (F + vZ)

21

Maximum Force, FMX


●CSX = 233 MPa (33.8 ksi) ●

● ●CSI = 245 MPa (35.5 ksi)

Calculated at Bottom: CSB = 264 MPa (38.2 ksi)


Compresisve Stress Results At Gage Location (CSX and CSI) and at Bottom (CSB)

23

Calculating Tension Stresses Below Pile Top From Force in Wave-down and Wave-up

Fd

Fu

F

vZ


L

Upward

Wave

Downward

Wave

Wave Superposition for Force Below Sensors

x

Fd1

Fu2

Fx = Fu2 + Fd3

Fd3

2x/c t = 0

2L/c

L/c


Tension Stress Calculation (Wave-Up)

Fu

Fd

Max. Tension - up

Minimum Compression - down

x


Tension Stress Maximum and Distribution

t3

top toe

Point of max tension

Max. Tension Wave Up

Equal


Another Tension Stress Example

top toe


Pile Damage: BTA, LTD

•A pile impedance reduction

(damage?) causes a tension

reflection before 2L/c

•The time at which the tension

reflection arrives at the gage

location indicates the depth to the

damage: LTD = (tdamage / 2) c


2L/c t = 0 L/c

Z2

Fd2

Fu1

Fd,1

2x/c

Z1

A

B

FA = FB: Fu,1 + Fd,1 = Fd,2

vA = vB: vu,1 + vd,1 = vd,2

2nd equation: (Z2/Z1)(Z1vu,1 + Z1vd,1) = Z2 vd,2

with = Z2/Z1: (- Fu,1 + Fd,1) = Fd,2 = Fu,1 + Fd,1

= (Fu,1 + Fd,1) / (- Fu,1 + Fd,1)

x


t1

t3

Fu,1 = ½(Fu,t3 - Zvt3)

Fd,1 = ½(Ft1+Zvt1)

Damage Assessment Example


Resistance Waves

L/c

L

x

Ri

-½Ri

RB

½Ri

RB

Upward traveling wave at time 2L/c:

Fu,2 = -Fd,1 + ½Ri + ½Ri + RB

Fd,1 -Fd,1

½Ri

RTL = Fu,2 + Fd,1

Fu,2

Fd,1


The Case Method Equation

RTL = Fd,1 + Fu,2

RTL is the total pile resistance:

Dynamic + static; shaft resistance + end bearing

RTL is mobilized during time 2L/c following time t1


The Static Resistance is Total Resistance - Damping

RS= RTL – RD

Assuming RD = Jv v [kN/m/s][m/s]

Introducing: Jc = Jv / Z ….. Case Damping Factor

Then RD = Jc Z v


Using pile toe velocity as representative vtoe = 2 Fd,1- RTL

Rstatic= RTL - Jc(2 Fd,1 – RTL)

Rstatic= (1 – Jc)Fd,1 + (1 + Jc )Fu,2

vtoe


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

F

= 5450 kN

F

= 50 kN

F

=2,820 kN

F

= 2,730 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 kN


Time of Fd,1

and Fu,2

t1 t2 2L/c

We calculate Rstatic at the time when it

gives the maximum

activated value


R

Compressive upward wave

Fur = ½R; vur = -½R/Z

Tensile downward wave

Fdr = -½R; vdr = -½R/Z

R/2

R/2

Δx

x

Pile with shaft resistance:

Equilibrium and Continuity


Shaft and Toe Resistance 2L/c t = 0 L/c

L

x

Rf

-½Rf

RB

½Rf

RB

Fd,1

-Fd,1 ½Rf


Friction Pile Records


Fd Fu

F

vZ

40

Wave-up Force Change Due to Friction

Rf

½Rf


PDA Soil Resistance Results End of Driving


PDA Soil Resistance Results Restrike; Blow No. 1


Restrike Blow No. 2


Restrike, Blow No. 4


• Quick signal

matching

• Total Capacity

• Shaft vs end bearing

• Tension stresses

• Compression strs.

• Recommended Jc

• Match Quality

• Computed match

• Load test curve

• Distribution

Another Method of Capacity Calculation: iCAP®

(a subset of CAPWAP®)

Best Results on uniform driven piles!

iCAP :

Ru 493 kips

MQ 2.12



A Monitoring Example: Rigolet Bridge

47

Cylinder Piles 66” dia.


PDA Measurements

including circumferential

strain measurements


Cylinder Pile Data (EOD)


Case Method Monitoring Results


An Example: Wave equation + Testing

Water Table at 3 m or 10’ depth

Depth Description N qu

m (ft) kPa (ksf)

4 (13) Sand 6

8 (26) Sand 13

13.4 (44) Clay 180 (3.8)

22 (72) Clay with Sand Lenses 300 (6.2)

52 PDPI June 2013 – Case Method

GRLWEAP Static

Soil Analysis

• Based on “SA” analysis

using: • N-value

• qu

Ru = 1700 kN

Rshaft = 1200 kN


Wave Equation analysis input


Wave Equation analysis: Bearing Graph

08-Aug-2012GRL Engineers, Inc.

GRLWEAP Version 2010GRLWEAP Example



Com

pres

sive

Stre

ss (M

Pa)

0

4

8

12

16

20

Tens

ion

Stre

ss (M

Pa)

0

4

8

12

16

20

Blow Count (blows/.30m)

Ulti

mat

e C

apac

ity (k

N)

0 60 120 180 240 300 360

0

800

1600

2400

3200

4000


Stro

ke (m

)

0 60 120 180 240 300 360

0

1

2

3

4

5

DELMAG D 30-32

Ram Weight 29.37 kN

Efficiency 0.800

Pressure 9645 (99%) kPa

Helmet Weight 17.79 kN

Hammer Cushion 19259 kN/mm

Pile Cushion 1009 kN/mm

COR of P.C. 0.500

Skin Quake 2.500 mm

Toe Quake 10.160 mm

Skin Damping 0.650 sec/m

Toe Damping 0.500 sec/m

Pile Length

Pile Penetration

Pile Top Area

20.50

14.01

3716.12

m

m

cm2

Pile Model

Skin Friction

Distribution

Res. Shaft = 71 %

(Proportional)

For 1700 kN capacity we would expect 170 bl/m = 51 bl/0.3m



At the statically predicted capacity of 1700 kN we would expect a

blow count of 51 bl/0.3m)

We would expect a transferred energy of 26 kJ at a stroke of 2.4 m






Com

pres

sive

Stre

ss (M

Pa)

0

4

8

12

16

20

Tens

ion

Stre

ss (M

Pa)

0

4

8

12

16

20


Ulti

mat

e C

apac

ity (k

N)

0 60 120 180 240 300 360

0

800

1600

2400

3200

4000


Stro

ke (m

)

0 60 120 180 240 300 360

0

1

2

3

4

5

DELMAG D 30-32

Ram Weight 29.37 kN

Efficiency 0.800

Pressure 9645 (99%) kPa

Helmet Weight 17.79 kN

Hammer Cushion 19259 kN/mm

Pile Cushion 1009 kN/mm

COR of P.C. 0.500

Skin Quake 2.500 mm

Toe Quake 10.160 mm

Skin Damping 0.650 sec/m

Toe Damping 0.500 sec/m

Pile Length

Pile Penetration

Pile Top Area

20.50

14.01

3716.12

m

m

cm2

Pile Model

Skin Friction

Distribution

Res. Shaft = 71 %

(Proportional)

Wave Equation analysis: Bearing Graph At Refusal we would expect a 4000 kN capacity



At refusal (1210 bl/m or 370 bl/ft) we would expect 4000 kN

capacity at a stroke of 2.5 m and a transferred energy of 26.8 kJ

Let’s check the analysis! 58 PDPI June 2013 – Case Method

• Measure force and motion near the pile top

• Calculate transferred energy, bearing capacity, stresses

PDA Testing + CAPWAP®


GRLWEAP

at Refusal

1210

(370)

27

(20)

17.5

(2.5)

1.1

(0.15)

PDA Results and Comparison GRLWEAP

PDA Wave Equation Rated/Mean

Stroke in m

in ft

2.7

8.8

2.5

8.3

3.5

11.3

Transfer Ratio(%) 21 27 29

Blow

Count

Transf’d

Energy

Comp.

Stress

Tension

Stress

Bl/m

(Bl/ft)

kJ

(ft-kips)

MPa

(ksi)

MPa

(ksi)

Measured

by PDA

1460

(445)

21

(15.5)

13.5

(1.9)

2.4

(0.35)


CAPWAP Results

Best Signal Match

• CAPWAP (Signal Matching) is a one-dimensional dynamic

analysis of the pile which uses the measured signals to determine

static and dynamic soil resistance values.

• Based on the static results, a simulated static test is performed

leading to a load-set curve, representation a (very) quick load test.

Measured Measured, F

and vZ


CAPWAP Results

Best Signal Match

Load-Set

Curve


CAPWAP Numerical Results Ru= 2100 kN Rshaft = 1110 kN Rtoe = 990 kN


Summary of Capacities Based on EOD

Static

Analysis

Capacity

Actual

Blow

Count

Wave

Equation

Capacity

CAPWAP

Capacity

kN

(kips)

Bl/m

(Bl/ft)

kN

(kips)

kN

(kips)

1,700

(382)

1482

(445)

4,000

(900)

2,100

(470)

Check whether additional capacity can be gained with

time by doing a restrike test.

Pile is driven 6 inches after 24 hours waiting time.

Blow Count now is 300 Bl/m (90 bl/ft)


Hammer Performance Results

End of Drive

PDA Wave Equation Rated/Mean

Stroke in m

in ft

2.7

8.8

2.5

8.3

3.5

11.3

Transfer Ratio(%) 21 27 (Refusal) 29

Beginnning of Restrike

PDA Wave Equation Rated

Stroke in m

in ft

3.3

10.7

2.5

8.3

3.5

11.3

Transfer Ratio(%) 35 26 (90 bpf) N/A


Revisiting the Wave Equation Bearing Graph

At 300 bl/m or 90 bl/ft we would expect 2500 kN capacity

with again 26 kJ transferred energy and a stroke of 2.5 m


Capacity Summary Based on EOD and BOR

Static

Analysis

Capacity

Actual

Blow

Count

Wave

Equation

Capacity

CAPWAP

Capacity

kN

(kips)

Bl/m

(Bl/ft)

kN

(kips)

kN

(kips)

End of

Driving

1482

(445)

4,000*

(900)

2,100**

(470)

Restrike

1,700***

(382)

300

(90)

2,500

(560)

2,550

570


Capacity and (LRFD) Safe Load Summary

Method

Nominal

Resistance

(kN)

Resistance

Factor, φ (AASHTO 2009)

Equivalent

F.S.

Safe Load

(kN)

Static

Formula 1700 0.40 (avg) 3.50 485

ENR

Gates

31,352

4,510

0.10

0.40

14.0

3.50

2,240

1,290

WE-EOD

WE-BOR

4,000

2,500

0.50

0.50

2.80

2.80

1,430

890

CW-EOD

CW-BOR

2,100

2,550

0.65

0.65

2.15

2.15

977

1,190


Back-calculation of Hammer Efficiency


Results from Wave Equation after Matching EOD and BOR Test Results

Quantity

EOID BOR

Normal or

CAPWAP GRLWEAP

Normal or

CAPWAP GRLWEAP

Hammer Efficiency (%) 80 50 80 73

Hammer Cushion

- Elastic Modulus (ksi) 550 275 550 550 Combustion Pressure

(%) 100 100 100 120

Pile Cushion

- Elastic Modulus (ksi)* 60 - 90 70 60 - 90 110

Pile Cushion

- Coeff. of Restitution 0.50 0.25 0.50 0.25

The hammer may have overheated at EOD after 4230 blows. and, therefore, had poor energy transfer.


• The PDA processes pile top force and velocity records

according to the (closed form solution) Case Method;

results allow for assessment of • Pile Stresses

• Hammer Performance

• Soil Resistance

• Pile Integrity

• These results are diplayed in Real Time and, therefore,

allow for real time monitoring of the pile installation

• For Dynamic load testing Restrikes + CAPWAP are

usually necessary

• After PDA+CAPWAP the GRLWEAP analysis can be

refined

Summary


Thank you for your

attention For further information see:

www.pile.com

QUESTIONS?

[email protected]

2. Pile Testing Methods - Pile Driving Contractors Association · 2013-07-022. Pile Testing Methods...

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Transcript of 2. Pile Testing Methods - Pile Driving Contractors Association · 2013-07-022. Pile Testing Methods...