Modeling Embankment Induced Lateral Loads on Deep Foundations Web Page/nsf workshop 2005... ·...
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Modeling Embankment Induced Lateral Loads on Deep Foundations By Siva Kesavan URS Corporation
Transcript of Modeling Embankment Induced Lateral Loads on Deep Foundations Web Page/nsf workshop 2005... ·...
Modeling Embankment Induced Lateral Loads on Deep
Foundations
BySiva Kesavan
URS Corporation
Problem
• Problem based on Failure of East Bound Patapsco Avenue Bridge – Baltimore, MD 1990
• Bridge approximately 50 ft from a 70-90 ft Landfill Construction
• Landfill Construction Caused Excessive Lateral Movement in 12” Concrete Piles and Piles and Bridge Deck Separated at the Top
Solutions
• Classical Approach– Linear Elastic
Stress Distribution– “Plastic Flow”
Approximate Sketch
Solutions
• Classical Approach– Linear Elastic Stress Distribution– “Plastic Flow”
• Finite Element Method– Simulations with FEM Program
HOPDYNE (Anandarajah, 1990)
Classical Approach
• Elastic Stresses on PilesHv = I w H
w - unit weight = 100 pcfH - Height of embankment I - Horizontal stress influence
factor = 0.004 z (at 50 ft)z - Depth v - Horizontal Stress
50’
v = 1.9 ksf @ 60 fttrangular distribution
Not Realistic
Not Enough Stresses to Cause Pile Failure
Classical Approach
• Plastic Flow of Soft SoilHc - Shear Strength (Cohesion)
Use Residual Shear strength of220 to 400 psf on both sides of the pile
Shear stress on concrete due to this loading 1.2 ksf or more
50’
Sand
Soft Clay
Stiff Clay
Enough to Cause Pile Failure
See Table
WT Silty Sand
Soft Clay
Stiff Clay
70’
80’
100’
Industrial Waste
Sand seams (p=0)
Failure of Pile
Loading: Construct the landfill in one year
Consolidate for another year
Simulations Using
HOPDYNE (Anandarajah, 1990)
Fully-Coupled Analysis with k = 1.0E-12 ft/s for clays and k=1.0E+02 ft/s for sands
What Constitutive Models to Choose?
21 ,,,,,, :dilation Controlled Hardening,,,,, :dilation Controlled ng,Nonhardeni
,,, :dilation Zerong,Nonhardeni
γγφνφ
φν
dcEdcvE
cE
ν,E
OCR,,, Mκλ
OCR,,,, hMκλ
inithM AOCR,,,,,κλ
DP
See Table
DP: Drucker-Prager
ABS: Anisotropic Bounding Surface Clay Model
(Anandarajah and Dafalias, 1986)
CC: Modified Cam-Clay
EE: Linear Elastic
CC or ABS with OCR=10
DP
WT Silty Sand
Soft Clay
Stiff Clay
70’
80’
100’
Industrial Waste
Sand seams (p=0)
Analysis Types
1 2 3 4
All elastic CC with M=0.6 ABS with M=0.6 CC with M=1.2
OCR=1 OCR=1, A=1.3 OCR=10
Failure of Pile
Horizontal Stresses in Soil Near the Pile
01020304050607080
0.00E+00
1.00E+03
2.00E+03
3.00E+03
4.00E+03
5.00E+03
Initial
Elastic
Horizontal Effective Stress
Depth
Horizontal Stresses in Soil Near the Pile
0
10
20
30
40
50
60
70
80
0.00E+00 5.00E+03 1.00E+04 1.50E+04
Initial
Elastic
CC
Horizontal Effective Stress
Depth
Horizontal Stresses in Soil Near the Pile
0
10
20
30
40
50
60
70
80
0.00E+00 5.00E+03 1.00E+04 1.50E+04
Initial
Elastic
All StiffABS CC
Horizontal Effective Stress
Depth
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Deformation
(click on the picture)
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Pore Pressure
(click on the picture)
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Shear Strain
(click on the picture)
DP
See Table
DP: Drucker-Prager
ABS: Anisotropic Bounding Surface Clay Model
(Anandarajah and Dafalias, 1986)
CC: Modified Cam-Clay
EE: Linear Elastic
CC or ABS with OCR=10
DP
WT Silty Sand
Soft Clay
Stiff Clay
70’
80’
100’
Industrial Waste
Sand seams (p=0)
Analysis Types
1 2 3 4
All elastic CC with M=0.6 ABS with M=0.6 CC with M=1.2
OCR=1 OCR=1, A=1.3 OCR=10
Soil Failure: Remove Sand Seams Increase Construction Rate
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Deformation
(click on the picture)
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Pore Pressure
(click on the picture)
M003-1: z = 10 to 60’ ABS with M=0.6 and OCR=1: Shear Strain
(click on the picture)
Horizontal Stresses in Soil Near the Pile
0
10
20
30
40
50
60
70
80
-5.00E+03
0.00E+00 5.00E+03 1.00E+04 1.50E+04 2.00E+04
No Sand Seams
Fast Loading
Slow Loading with Sand Seams
Initial
Horizontal Effective Stress
Depth
Comparison of Deformation
Slow Loading with Sand Seams 0.9’ 0.65’
Fast Loading with no Sand Seams
3.85’ 4.0’
On a Laptop? Forget it!
What happens to forces on piles when DP is used for the middle soft layer?
Horizontal Stresses in Soil Near the Pile
0
10
20
30
40
50
60
70
80
-5.00E+03
0.00E+00
5.00E+03
1.00E+04
1.50E+04
2.00E+04
Initial
ABS with M=0.6
DP with M=0.6
Horizontal Effective Stress
Depth
What happens to forces on piles when WT is lowered to the bottom of soft layer?
Horizontal Stresses in Soil Near the Pile
0
10
20
30
40
50
60
70
80
-5.00E+03
0.00E+00
5.00E+03
1.00E+04
1.50E+04
2.00E+04
Initial
WT at the top of Soft Layer
WT at the bottom of Soft Layer
Horizontal Effective Stress
Depth
0.00E+001.00E+002.00E+003.00E+004.00E+005.00E+006.00E+007.00E+008.00E+009.00E+001.00E+01
0.00E+00
2.00E+06
4.00E+06
6.00E+06
8.00E+06
1.00E+07
Time (sec)
Vert. disp. of soil
Near pile (feet)
CCABS
While the difference is not too significant in this case, the results suggest that, in general, quantitative prediction may depend on the choice of the constitutive model. The availability of a model to simulate a certain effect (e.g., anisotropy) allows that effect to be at least parametrically investigated.
USE OF AN MSE WALL TO SUPPORT A LANDFILL
MSE Wall
Soft Clay
Industrial Waste
(click on the picture)
Advanced Numerical Modeling Finite Element Method
• Tremendous Potential in Understanding the Problem
• Revolutionize Geotechnical Design and Analysis
• Verification is needed before using them for Quantitative Predictive Purposes
Final Deformed Configuration
(click on the picture)
Final Deformed Configuration (without displacement vectors)
Slip
(click on the picture)
Pore Pressure Response
(click on the picture)
Shear Strain Distribution
(click on the picture)
Fast Construction
(click on the picture)
Slow Construction
Fast Construction
0.00E+005.00E-011.00E+001.50E+002.00E+002.50E+003.00E+003.50E+004.00E+004.50E+00
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
A
Horizontal displacement of A
Time (s)
Fast Construction
Slow Construction
