Lateral Load Testing for Pile Design

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
Reaction Beam
12.75” Reaction Piles
Swivel-Head End-Platens
LVDT attached to
reference frame
Inclinometer Pipe
12.75” Test Pile
300 kip Load Cell
300 kip Hydraulic Jack
Spacer box

Load (kN)
Load (kN)
Load-Deflection Curve (12.75” Pipe Pile)
250
200
150
100
50
Continuous
15th Cycle
Curves
1st Cycle
15th Cycle
0
0 20 40 60 80 100
Deflection (mm)

Instrumentation & Measurements
• Below Grade:
Slope & Displacement
Inclinometer probe
EL-Sensor (downhole inclinometer array)
Shape Array Sensors
Strains

Depth Below Top of Pile (ft)
Depth Below Top of Pile (ft)
Deflection vs. Depth
Moment vs. Depth
0
Displacement (in)
-1.0 0.0 1.0 2.0 3.0 4.0
0
Moment (kips-ft)
-400 -200 0 200
5
5
10
10
15
10 kips
15
10 kips
20 kips
20 kips
20
40 kips
50 kips
20
40 kips
50 kips
75 kips
75 kips
25
88 kips
95 kips
25
88 kips
95 kips
30
30

Shape Accelerometer Array

Shape Accelerometer Array
Shape Array
Inclinometer Pipe

Depth From Top of Cap (in)
Depth From Top of Cap (in)
Shape Sensor Array
0
Displacement (in)
-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
0
Displacement (in)
-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
50
50
100
100
150
150
200
200
250
250
300
300
South Array
350
South Inclinometer
350
North Array
400
400
North Inclinometer
450
450
500
500

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?

Depth Below Ground Surface (m)
Bending Moment vs Depth
0
Bending Moment (kN-m)
-50 0 50 100 150 200 250
1
2
3
4
5
6
7
8
9
10
11
Deflection
4mm
6mm
13mm
19mm
25mm
38mm
51mm
64mm
76mm
89mm
12

Analysis of Lateral Load Test Data

Lateral Load Analysis
H
p
p
p
y
y
Interval
y
2
y
1
Nonlinear
springs
p
p
y
y
y
4
3
y
y
5
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

Depth below excavated surface (m)
Undrained Strength, s u (kPa)
0 100 200 300
1.34 m
1.07 m
STIFF CLAY
Water Table
s u = 70 kPa 50 = 0.005
k= 136 N/cm3
0.0
1.0
1.65 m
SAND = 36 O k =61 N/cm 3
STIFF CLAY
s u = 105 kPa 50 = 0.005
k= 271 N/cm 3
2.0
3.02 m
3.48 m SAND = 36 O k=61 N/cm 3
4.09 m
STIFF CLAY
s u = 105 kPa 50 = 0.005
k=271.43 N/cm 3
SILTY SAND = 38 O k=61.07 N/cm 3
3.0
4.0
5.15 m
5.0
6.0
Vane Shear Tests
Unconfined Comp. Tests
Avg CPT strength
SOFT CLAY
s u = 35 kPa 50 = 0.01
k= 27 N/cm 3
7.0
8.0
Strength Used in Analysis
9.0
10.0
11.0
12.0

Load (kN)
450
Measured & Computed Load vs Deflection
400
350
Measured
Computed - LPILE
300
250
200
150
100
50
0
0 5 10 15 20 25 30 35 40 45 50 55
Deflection (mm)

Moment (kN-m)
Computed & Measured Moment vs. Load
900
800
700
Computed with LPILE
Measured
600
500
400
300
200
100
0
0 100 200 300 400 500
Load (kN)

Depth Below Excavated Ground (m)
Computed & Measured
Moment vs Depth
Bending Moment (kN-m)
-100 0 100 200 300 400 500 600 700 800 900
0
1
2
3
4
5
6
7
8
9
133 kN
240 kN
300 kN
414 kN
10
11
12

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
Load Piston
Combustion
Chamber
Statnamic
Sled

Statnamic Test Firing Videos

Downhole Motion Sensors &
Strain Gauges

Equation of Motion
F = F a + F v + F u
= 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

Load (kN)
Comparison of Dynamic Forces
3000
2500
2000
1500
Fstn
Fa
Fv
Fu
1000
500
0
0.4 0.5 0.6 0.7 0.8 0.9 1
-500
-1000
-1500
-2000
Time (sec)

Damping force (kN)
Load (kN)
Damping
is
the
Difference
3500
3000
2500
2000
1500
1000
500
0
Calculated static load
Measured static load
Statnamic load
0 10 20 30 40
Deflection (mm)
Damping ratios
between 0.3
and 0.5
1400
1200
1000
800
600
400
200
0
0 10 20 30 40
Deflection (mm)

Computation of Equivalent Static Force
Lumped Mass Model
of Drilled Shaft
F s = F stn - ΣM i a i - ΣC i v i

Elevation View of Test Site
3x3 Pile Group
High-Speed
Hydraulic Ram
1 m Drilled Shaft
Liquefied Sand
5 m
8 m
Non-Liquefied
Sand

Treasure Island Naval Station
Test Site

Blast Charge Pattern
Pile Group
Drilled Shaft
Blast Holes

Ru
Pore Pressure Dissipation Data
1 .2 0
1 .0 0
0 .8 0
0 .6 0
7 .3 m E a st o f A
5 .5 m E a st o f A
4 .3 m E a st o f A
P o int A
3 .2 m W e st o f A
6 .4 m W e st o f A
0 .4 0
0 .2 0
0 .0 0
0 600 1200 1800 2400 3000 3600
T im e [s e c ]

Single Pile Test

Load (kN)
Load vs Deflection Curves for Single Pipe Pile
250
200
150
Non-Liquefied
Liquefied
100
50
0
-50
-100
-50 0 50 100 150 200 250
Displacement (mm)

Load (kN)
Ru (%)
100
80
60
40
20
0
-20
-40
200
150
100
0 120 240 360 480 600
Time (sec)
50
0
-50
0 120 240 360 480 600
Time (sec)

Blast Liquefaction Video
(4 Pile Group and Shaft)

Depth Below Excavated Ground (m)
Moment Before & After Liquefaction
-2
Moment (kN-m)
-100 0 100 200 300 400 500
0
2
4
6
8
Before Liquefaction
10
After Liquefaction
12

Development of p-y Curves
Strain
Curvature
Integrate
Slope
Integrate
Deflection, Y
EI
P-Y curve
Moment
Differentiate
Shear
Differentiate
Distributed
load or
“pressure”, P

Gerber p-y Analysis Routine

Generalized p-y Curves

Computed
vs Measured
Response

Cooper River Bridge
Charleston, South Carolina
Longest Cable-stayed bridge in
North and South America
New Bridge-Completed July 2005

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
Row 1
Row 2
Trailing Row Piles
Row 3
Direction of
Loading

Horizontal Force/Length, P
P-Multiplier Concept (Brown et al, 1988)
Single Pile Curve
P SP
Group Pile Curve
P GP = P MULT P SP
Horizontal Displacement, y

P-multipliers from Full-Scale Tests
(Situation in 1998)
Soil Type
(Reference)
Clean Sand
(Brown et al. 1988)
Stiff Clay
(Brown et al. 1987)
Soft Silty Clay
(Meimon et al. 1986)
Front
Row
2 nd
Row
3 rd
Row
0.8 0.4 0.3
0.7 0.5 0.4
0.9 0.5 -
BYU has conducted 11 Full-scale tests over the past 10 years

P-Multiplier
P-multiplier vs. Spacing Curves
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Reese et al (1996)
Reese & Van Impe (2001)
WSDOT (2000)
AASHTO (2000)
US Army (1993)
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.

I-15 Pile Group Testing
• 9 Pile Group (324 mm) at 5.6 D Spacing
• 12 Pile Group (324 mm) at 4.5 D Spacing
• 15 Pile Group (324 mm) at 3.3 D Spacing
• 9 Pile Group (600 mm) at 3 D Spacing

15 Pile Group at 3.3 D Spacing

9 Pile Group at 5.6 D Spacing
Pinned
Connection
LVDT
Tie-Rod
Load Cell

Avg. Pile Load (kN)
9 Pile Group at 5.6 D Spacing
250
200
150
100
50
0
Single
Row 1
Row 2
Row 3
0 20 40 60 80
Avg. Group Deflection (mm)

Avg. Pile Load (kN)
12 Pile Group at 4.5 D Spacing
200
150
100
50
0
0 20 40 60 80
Avg. Group Deflection (mm)
Single
Row 1
Row 2
Row 3
Row 4

Avg. Pile Load (kN)
15 Pile Group at 3.3 D Spacing
250
200
150
100
Single
Row 1
Row 2
Row 3
Row 4
Row 5
50
0
0 20 40 60 80 100
Avg. Group Deflection (mm)

Avg. Pile Load (kN)
9 Pile Group at 3 D Spacing
500
400
300
200
100
0
Single
Row 1
Row 2
Row 3
0 20 40 60
Avg. Group Deflection (mm)

P-Multiplier
P-Multiplier
P-multiplier vs Spacing for Stiff Clay
(a) Leading Row P-Multipliers
(b) Trailing Row P-Multipliers
1.2
1.0
Reese et al (1996)
1.2
1.0
Reese et al (1996)
0.8
2 ft Pile
0.8
0.6
0.4
0.2
Brown et al
(1997)
AASHTO (1998)
Stiff Clay-Rollins et al (2003)
0.6
0.4
0.2
2 ft Pile
2 ft Pile
Brown et al
(1997)
AASHTO (1998)
Row 2-Stiff Clay Rollins et al (2003)
Rows 3-5-Stiff Clay-Rollins et al (2003)
0.0
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.
0.0
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.
Rollins et al. Oct 2006, ASCE JGGE

P-multiplier Curves vs. Spacing
Rollins et al. Oct 2006, ASCE JGGE
1.2
P-Multiplier, P m
1.0
0.8
0.6
0.4
0.2
0.0
1st Row Piles
2nd Row Piles
3rd or Higher Row Piles
AASHTO
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.

Test
Site
Layout
15 Pile Group at
3.9 D Spacing
9 Pile Group at
5.6 D Spacing
1.2 m Drilled
Shafts
9 Pile Group at
2.8 D Spacing
SLC
Airport
Pile
Group
Tests

P-Multiplier
P-Multiplier
Group Interaction Reduction Factors
(P-multipliers)
(a) Leading Row P-Multipliers
(b) Trailing Row P-Multipliers
1.2
1.0
Reese et al (1996)
1.2
1.0
Reese et al (1996)
0.8
0.8
0.6
AASHTO (1998)
0.6
AASHTO (1998)
0.4
0.2
0.0
Stiff Clay-Rollins et al (2003)
Soft Clay-This Study
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.
0.4
0.2
0.0
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
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.

Pile Group Load Tests in Sand
3x5 Group at 3.9D Spacing
3x3 Group at 5.65D Spacing
3x3 Group at 3.3D Spacing
2x2 Group at 3.3D Spacing

P-Multiplier
P-Multiplier
P-Multiplier
P-Multipliers vs Spacing (Sand)
(a) 1st Row P-Multipliers
, fm
1.2
1.0
(b) 2nd and 3rd Row P-Multipliers
0.8
1.2
0.6
0.4
0.2
0.0
, fm
1.0
0.8
0.6
0.4
Reese et al (1996)
Full-Scale Tests
Centrifuge Tests
Design Line
, fm
AASHTO
Reese et al (1996)
0.8
Full-Scale Tests
2 3 0.2 4 5 6 7 8 Centrifuge Tests
0.6
Design Line
Pile Spacing 0.0 (c-c)/Pile Diam.
AASHTO
2 3 40.4
5 6 7 8
1.2
1.0
Pile Spacing 0.2 (c-c)/Pile Diam.
0.0
(c) 4th or higher Row P-Multipliers
Reese et al (1996)
Full-Scale Tests
Centrifuge Tests
AASHTO (2000)
2 3 4 5 6 7 8
Pile Spacing (c-c)/Pile Diam.

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
Elevation View
45-/2
• Passive failure wedge
inclined at 45-/2.
• As increases the
angle gets smaller and
wedge gets longer.
• Longer wedge causes
more group
interaction.

Influence of Friction Angle on Group Interaction
Plan View
• Passive failure wedge
fans out at .
• As increases the
angle gets larger and
wedge gets wider.
• Wider wedge causes
more group
interaction.

P-Multiplier
Influence of Friction Angle on P-multiplier
1.0
Less Group
Interaction
More Group
Interaction
Soft
Clay
Stiff
Clay
Looser
Sand
Denser
Sand
Drained Friction angle, ’

Average Pile Load (kN)
Post-Liquefaction Pile Response
100
80
60
40
20
Single Pile
Resistance due to
Pile alone
Resistance due to
Soil Dilation
0
-20
-40
-60
0 25 50 75 100 125 150 175 200 225 250
Displacement (mm)
P-y curves for Liquefied Sand
(ASCE JGGE, Jan 2005)
Built into LPILE/GROUP

Average Pile Load (kN)
Average Pile Load (kN)
Post-Liquefaction Group Effects
(10th 200 mm Cycle)
80
100
60
80
40 60
20 40
Lead Row-Group
Single Pile
Middle
Lead Row-Group
Row-Group
Trail Middle Row-Group
Trail Row-Group
20
0
0
-20
-20
-40
-40
-60
-60
0 25 50 75 100 125 150 175 200 225 250
0 25 50 75 100 125 150 175 200 225 250
Displacement (mm)
Displacement (mm)

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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