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