lateral load testing for pile design - · pdf filelateral load testing for pile design kyle...

Lateral Load Testing for

Pile Design

Kyle Rollins

Brigham Young University

Wind and Waves in

Hurricanes

Seismic Forces

Ship Impact

Landslides and lateral

spreading in Earthquakes

Lateral Testing

Useful where lateral loads may control design

Main Objective: measure soil resistance of

critical strata

Zone of most influence

Approx top 5 D

Objectives

Evaluate Soil Resistance

Confirm Design Assumptions

Improve Reliability

Reduce Foundation Cost

Stratigraphy & “the big picture”

Must have good geotech investigation at the

test site and elsewhere

Consider site variability when interpreting

results & applying to design; site specific

correlations w/ in-situ testing?

Scourable materials?

Field Test Setup & Loading

Calibrated Jack, Load Cell w/ rot’l bearing

Long travel jack, displacement transducers

Strain gages and inclinometers in piles

Test appropriate stratigraphy!

Single Pile Load Tests

324 mm OD Steel Pipe Pile 600 mm OD Steel Pipe Pile

Measurements - Purpose

Back-fit model to observations

Evaluate model for general soil conditions

across site

Develop model for design (using judgment)

Note: boundary conditions will differ between

test setup & design

Instrumentation & Measurements

At pile top:

Load cell & jack

Displacement

Rotation (use pair of LVDT’s)

I-15 Lateral Load Test Schematic

Swivel-Head End-Platens

12.75” Reaction Piles

12.75” Test Pile

300 kip Load Cell

300 kip Hydraulic Jack

Reaction Beam

Spacer box

LVDT attached to

reference frame

Inclinometer Pipe

Swivel-Head End-Platens


12.75” Test Pile

300 kip Load Cell


Reaction Beam

Spacer box

LVDT attached to

reference frameSwivel-Head End-Platens


12.75” Test Pile

300 kip Load Cell


Reaction Beam

Spacer box

LVDT attached to

reference frame

Inclinometer Pipe

Load-Deflection Curve (12.75” Pipe Pile)

0

50

100

150

200

250

0 20 40 60 80 100Deflection (mm)

Lo

ad

(k

N)

1st Cycle

15th Cycle

0

50

100

150

200

250

0 20 40 60 80 100Deflection (mm)

Lo

ad

(k

N)

1st Cycle

15th Cycle

Continuous

15th Cycle

Curves

Instrumentation & Measurements

Below Grade:

Slope & Displacement

Inclinometer probe

EL-Sensor (downhole inclinometer array)

Shape Array Sensors

Strains

Deflection vs. Depth Moment vs. Depth

0

5

10

15

20

25

30

-1.0 0.0 1.0 2.0 3.0 4.0

Displacement (in)D

ep

th B

elo

w T

op

of P

ile

(ft)

10 kips

20 kips

40 kips

50 kips

75 kips

88 kips

95 kips

0

5

10

15

20

25

30

-400 -200 0 200

Moment (kips-ft)

De

pth

Be

low

To

p o

f P

ile

(ft)

10 kips

20 kips

40 kips

50 kips

75 kips

88 kips

95 kips

Shape Accelerometer Array

Shape Accelerometer Array

Inclinometer Pipe Shape Array

Shape Sensor Array

0

50

100

150

200

250

300

350

400

450

500

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Displacement (in)

Dep

th F

rom

To

p o

f C

ap

(in

)

South Array

South Inclinometer

0

50

100

150

200

250

300

350

400

450

500

-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Displacement (in)

Dep

th F

rom

To

p o

f C

ap

(in

)North Array

North Inclinometer

Strain Gauges

Photos courtesy Applied

Foundation Testing

Interpretation of Instrumentation

M = ε(EI/c)

What is effective I (cracked section)?

What is concrete modulus?

What is precision of strain measurement?

Bending Moment vs Depth -50 0 50 100 150 200 250

Bending Moment (kN-m)

12

11

10

9

8

7

6

5

4

3

2

1

0

De

pth

Be

low

Gro

un

d S

urf

ac

e (

m)

Deflection

4mm

6mm

13mm

19mm

25mm

38mm

51mm

64mm

76mm

89mm

Analysis of Lateral Load Test Data

Lateral Load Analysis

Nonlinear

springs

p

p

p

p

p

y

y

y

y Interval

y

y

y

y

y

1

2

3

4

5

H

After Coduto

Develop Design Soil Model

• P-y criteria should reasonably match geotechnical

profile

Backfit to test results using LPILE or FLPIER

Match load vs displacement response

Match general displacement vs depth and moment vs

depth response

Nonlinear bending response of the pile can be

important

Evaluate possible soil variations across site

Recommend soil parameters for design model

su= 70 kPa 50= 0.005

k= 136 N/cm3

STIFF CLAY

Water Table

STIFF CLAYsu= 105 kPa 50= 0.005

k=271.43 N/cm3

SOFT CLAY su= 35 kPa 50= 0.01

k= 27 N/cm3

STIFF CLAYsu= 105 kPa 50= 0.005

k= 271 N/cm3

1.07 m

1.34 m

3.02 m

4.09 m

SAND = 36O k =61 N/cm3

1.65 m

3.48 m SAND = 36O k=61 N/cm3

SILTY SAND = 38O k=61.07 N/cm

3

5.15 m

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

0 100 200 300

Undrained Strength, su (kPa)

Dep

th b

elo

w e

xcavate

d s

urf

ace (

m)

Vane Shear Tests

Unconfined Comp. Tests

Avg CPT strength

Strength Used in Analysis

Measured & Computed Load vs Deflection

0

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25 30 35 40 45 50 55

Deflection (mm)

Lo

ad

(k

N)

Measured

Computed - LPILE

Computed & Measured Moment vs. Load

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500

Load (kN)

Mo

me

nt

(kN

-m)

Computed with LPILE

Measured

Computed & Measured

Moment vs Depth 0

1

2

3

4

5

6

7

8

9

10

11

12

-100 0 100 200 300 400 500 600 700 800 900

Bending Moment (kN-m)

De

pth

Be

low

Ex

ca

va

ted

Gro

un

d (

m)

133 kN

240 kN

300 kN

414 kN

Use of Model for Design

• Adjust for differing pile top boundary

conditions

• Allow for scour or other changes

• Allow for site variability

• Adjust for cyclic loading, group effects, any

other parameters which may not be

reflected in the load test data (liquefaction?)

Lateral Statnamic Load Testing

0 to 400 kips in 0.2 seconds

Large Displacement, High Velocity

Lateral Statnamic Testing

Have Safely Generated Loads >1000 tons

2000 ton Potential

Load Pulse Can Last Up To 200 ms

Rate of Loading Similar To Initial Pulse of

Earthquakes, Transient Wind Loads, Impact

Schematic of Statnamic Test

Test

Foundation

Statnamic

Sled

Load Piston

Combustion

Chamber

Statnamic Test Firing Videos

Downhole Motion Sensors &

Strain Gauges

Equation of Motion

F = Fa + Fv + Fu

= ma + cv + ku

where, F = applied force (statnamic load cell)

m = mass of the foundation

a = acceleration in g’s

c = damping coefficient

v = velocity

k = static stiffness

u = displacement

Comparison of Dynamic Forces

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

3000

0.4 0.5 0.6 0.7 0.8 0.9 1

Time (sec)

Lo

ad

(k

N)

Fstn

Fa

Fv

Fu

Damping

is

the

Difference 0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40

Deflection (mm)

Lo

ad

(kN

)

Calculated static load

Measured static load

Statnamic load

0

200

400

600

800

1000

1200

1400

0 10 20 30 40

Deflection (mm)

Da

mp

ing

fo

rce

(k

N)

Damping ratios

between 0.3

and 0.5

Computation of Equivalent Static Force

Fs = Fstn - ΣMiai - ΣCivi

Lumped Mass Model

of Drilled Shaft

Elevation View of Test Site

8 m

Liquefied Sand

Non-Liquefied

Sand

5 m

3x3 Pile Group 1 m Drilled Shaft

High-Speed

Hydraulic Ram

Treasure Island Naval Station

Test Site

Blast Charge Pattern

Blast Holes

Drilled Shaft Pile Group

Pore Pressure Dissipation Data

0 .00

0 .20

0 .40

0 .60

0 .80

1 .00

1 .20

0 600 1200 1800 2400 3000 3600

T im e [sec ]

Ru

7 .3 m E ast o f A

5 .5 m E ast o f A

4 .3 m E ast o f A

P o int A

3 .2 m W est o f A

6 .4 m W est o f A

Single Pile Test

Load vs Deflection Curves for Single Pipe Pile

-100

-50

0

50

100

150

200

250

-50 0 50 100 150 200 250

Displacement (mm)

Lo

ad

(kN

)

Non-Liquefied

Liquefied

-40

-20

0

20

40

60

80

100

0 120 240 360 480 600

Time (sec)

Ru (

%)

-50

0

50

100

150

200

0 120 240 360 480 600

Time (sec)

Load

(kN

)

Blast Liquefaction Video

(4 Pile Group and Shaft)

Moment Before & After Liquefaction

-2

0

2

4

6

8

10

12

-100 0 100 200 300 400 500

Moment (kN-m)

Dep

th B

elo

w E

xcavate

d G

rou

nd

(m

)

Before Liquefaction

After Liquefaction

Development of p-y Curves

Integrate Curvature

EI

Differentiate

P-Y curve

Slope

Moment

Strain

Distributed

load or

“pressure”, P Shear

Deflection, Y Integrate

Differentiate

Gerber p-y Analysis Routine

Generalized p-y Curves

Computed

vs Measured

Response

Cooper River Bridge Charleston, South Carolina

New Bridge-Completed July 2005

Longest Cable-stayed bridge in

North and South America

Charleston Statnamic Testing

Good Group Behavior

Poor Group Behavior

Angry Mob Congress

Group IQ = Lowest IQ of anyone in the group

Pile Group Interaction

Leading Row Piles

Trailing Row Piles

Direction of

Loading

Row 1

Row 2

Row 3

P-Multiplier Concept (Brown et al, 1988)

Horizontal Displacement, y

Ho

rizo

nta

l F

orc

e/L

en

gth

, P

Single Pile Curve

Group Pile CurvePSP

PGP = PMULT PSP

P-multipliers from Full-Scale Tests (Situation in 1998)

Soil Type

(Reference)

Front

Row

2nd

Row

3rd

Row Clean Sand

(Brown et al. 1988)

0.8 0.4

0.3

Stiff Clay

(Brown et al. 1987)

0.7 0.5 0.4

Soft Silty Clay

(Meimon et al. 1986)

0.9 0.5 -

BYU has conducted 11 Full-scale tests over the past 10 years

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2 3 4 5 6 7 8

Pile Spacing (c-c)/Pile Diam.

P-M

ult

ipli

er

Reese et al (1996)

Reese & Van Impe (2001)

WSDOT (2000)

AASHTO (2000)

US Army (1993)

P-multiplier vs. Spacing Curves

I-15 Pile Group Testing

9 Pile Group (324 mm) at 5.6 D Spacing



9 Pile Group (600 mm) at 3 D Spacing

15 Pile Group at 3.3 D Spacing


LVDT Tie-Rod

Load Cell

Pinned

Connection


0

50

100

150

200

250

0 20 40 60 80

Avg. Group Deflection (mm)

Avg

. P

ile L

oad

(kN

)

Single

Row 1

Row 2

Row 3


0

50

100

150

200

0 20 40 60 80


Avg

. P

ile L

oad

(kN

)

Single

Row 1

Row 2

Row 3

Row 4


0

50

100

150

200

250

0 20 40 60 80 100


Avg

. P

ile L

oad

(kN

)

Single

Row 1

Row 2

Row 3

Row 4

Row 5

9 Pile Group at 3 D Spacing

0

100

200

300

400

500

0 20 40 60


Avg

. P

ile L

oad

(k

N)

Single

Row 1

Row 2

Row 3

P-multiplier vs Spacing for Stiff Clay

(a) Leading Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2 3 4 5 6 7 8Pile Spacing (c-c)/Pile Diam.

P-M

ult

ipli

er

Stiff Clay-Rollins et al (2003)

Reese et al (1996)

AASHTO (1998)

(b) Trailing Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2


P-M

ult

ipli

er

Row 2-Stiff Clay Rollins et al (2003)

Rows 3-5-Stiff Clay-Rollins et al (2003)

Reese et al (1996)

AASHTO (1998)

Rollins et al. Oct 2006, ASCE JGGE

Brown et al

(1997)

Brown et al

(1997)

2 ft Pile

2 ft Pile

2 ft Pile

P-multiplier Curves vs. Spacing

0.0

0.2

0.4

0.6

0.8

1.0

1.2


P-M

ult

ipli

er,

Pm

1st Row Piles

2nd Row Piles

3rd or Higher Row Piles

AASHTO

Rollins et al. Oct 2006, ASCE JGGE

Test

Site

Layout

9 Pile Group at

2.8 D Spacing

15 Pile Group at

3.9 D Spacing

9 Pile Group at

5.6 D Spacing

1.2 m Drilled

Shafts

SLC

Airport

Pile

Group

Tests

(b) Trailing Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2


P-M

ult

ipli

er

Row 2-Stiff Clay Rollins et al (2003)

Rows 3-5-Stiff Clay-Rollins et al (2003)

Row 2-Soft Clay-This Study

Rows 3-5-Soft Clay-This Study

Reese et al (1996)

AASHTO (1998)

(a) Leading Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2


P-M

ult

ipli

er

Stiff Clay-Rollins et al (2003)

Soft Clay-This Study

Reese et al (1996)

AASHTO (1998)

Group Interaction Reduction Factors

(P-multipliers)

Pile Group Load Tests in Sand

3x3 Group at 3.3D Spacing




P-Multipliers vs Spacing (Sand) (a) 1st Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2 3 4 5 6 7 8


P-M

ult

iplier

Reese et al (1996)

Full-Scale Tests

Centrifuge Tests

Design Line

AASHTO

, f m (b) 2nd and 3rd Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2 3 4 5 6 7 8


P-M

ult

iplier

Reese et al (1996)

Full-Scale Tests

Centrifuge TestsDesign Line

AASHTO

, f m

(c) 4th or higher Row P-Multipliers

0.0

0.2

0.4

0.6

0.8

1.0

1.2

2 3 4 5 6 7 8


P-M

ult

ipli

er

Reese et al (1996)

Full-Scale Tests

Centrifuge Tests

AASHTO (2000)

, f m

Explanation of Variability in Sand

Natural variability of sand relative to clay

Sand more influenced by installation procedure than clays

Different installation procedures

Jetting

Driven, Open-ended

Sand compacted around previously driven piles

Drilled shafts

Influence of Friction Angle on Group Interaction

Passive failure wedge

inclined at 45-/2.

As increases the

angle gets smaller and

wedge gets longer.

Longer wedge causes

more group

interaction.

45-/2 45-/2

Elevation View

Influence of Friction Angle on Group Interaction

Passive failure wedge

fans out at .

As increases the

angle gets larger and

wedge gets wider.

Wider wedge causes

more group

interaction.

Plan View

Influence of Friction Angle on P-multiplier P

-Multip

lier

Drained Friction angle, ’

1.0

Soft

Clay Stiff

Clay Looser

Sand Denser

Sand

Less Group

Interaction More Group

Interaction

Post-Liquefaction Pile Response

-60

-40

-20

0

20

40

60

80

100

0 25 50 75 100 125 150 175 200 225 250

Displacement (mm)

Av

era

ge

Pile

Lo

ad

(k

N) Single Pile

Resistance due to

Pile alone

Resistance due to

Soil Dilation

P-y curves for Liquefied Sand

(ASCE JGGE, Jan 2005)

Built into LPILE/GROUP

Post-Liquefaction Group Effects (10th 200 mm Cycle)

-60

-10

40

90

0 25 50 75 100 125 150 175 200 225 250

-60

-40

-20

0

20

40

60

80

0 25 50 75 100 125 150 175 200 225 250

Displacement (mm)

Av

era

ge

Pil

e L

oa

d (

kN

)

Lead Row-Group

Middle Row-Group

Trail Row-Group

-60

-40

-20

0

20

40

60

80

100

0 25 50 75 100 125 150 175 200 225 250

Displacement (mm)

Avera

ge P

ile L

oad

(kN

)

Single Pile

Lead Row-Group

Middle Row-Group

Trail Row-Group

Rollins Pile Group References Rollins, K.M., Olsen, R.J., Egbert, J.J., Jensen, D.H., Olsen, K.G.,

and Garrett, B.H. (2006). “Pile Spacing Effects on Lateral Pile Group Behavior: Load Tests.” J. Geotechnical and Geoenvironmental Engrg., ASCE, Vol. 132, No. 10, October, p. 1262-1271.

Rollins, K.M., Olsen, K.G., Jensen, D.H, Garrett, B.H., Olsen, R.J., and Egbert, J.J. (2006). “Pile Spacing Effects on Lateral Pile Group Behavior: Analysis.” J. Geotechnical and Geoenvironmental Engrg., ASCE, Vol. 132, No. 10, October, p. 1272-1283.

Rollins, K.M., Lane, J.D., and Gerber, T.M. (2005). “Measured and Computed Lateral Response of a Pile Group in Sand.” J. Geotechnical and Geoenvironmental Engrg, ASCE, Vol. 131, No. 1 Jan., p. 103-114.

Rollins, K.M., Gerber, T.M., Lane, J.D. and Ashford. S.A. (2005). “Lateral Resistance of a Full-Scale Pile Group in Liquefied Sand.” J. Geotechnical and Geoenvironmental Engrg., ASCE, Vol. 131, No. 1, p. 115-125.

Rollins, K.M., Snyder, J.L. and Broderick, R.D. (2005). “Static and Dynamic Lateral Response of a 15 Pile Group.” Procs. 16th Intl. Conf. on Soil Mechanics and Geotech. Engineering, Millpress, Rotterdam, The Netherlands, Vol. 4, p. 2035-2040.

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