Soil–Structure–Interaction inLiquefied Grounds and

Countermeasures:Lessons from Numerical Studies

Boris Jeremic

Department of Civil and Environmental Engineering

University of California, Davis

Jeremic 1

Introduction

• Dynamic effects (shaking)

• Kinematic effects (lateral spreading)

Jeremic 2

State of Practice (Art)

• Scaled p–y spring approach. (Suggested by old Japanese specifications for highway bridges (Japanese RoadAssociation [3]), by the Architectural Institutive of Japan [1], by Liu and Dobry [5], by Caltrans (Boulanger etal. [2] and Wilson et al. [8]), Wang et al. [7] and Lok and Pestana [6]: OK if for non–liquefying problems andgives consistent results using a range of computer platforms provided that: (a) appropriate p–y curves are used;(b) consistent radiational damping is implemented; and (c) appropriate gaping mechanics is used. However, forliquefied grounds this approach does not provide consistent results.)

• Limit equilibrium.This approach is adopted by the latest Japanese specifications for highway bridges (JapaneseRoad Association [4]). For example, Shin–Shukugawa Bridge was was designed using this methodology and (eg.Yokoyama et al. [9]). Land Road Bridge, (1987 Edgecumbe earthquake, New Zealand), barely made it. Need toassume actual failure kinematics a–priori?

Jeremic 3

Single Pile in Layered Soils

−1000 0 1000 2000−10

−8

−6

−4

−2

0

2

SAND

φ = 37.1o

−1.718

SAND

φ = 37.1o

−3.436

SAND

φ = 37.1o

Bending Moment (kN.m)

Dep

th (

m)

−400 −200 0 200 400 600−10

−8

−6

−4

−2

0

2

Shear Force (kN)−100 0 100 200 300

−10

−8

−6

−4

−2

0

2

Pressure (kN/m)−1000 0 1000 2000

−10

−8

−6

−4

−2

0

2

SAND

φ = 37.1o

−1.718

SOFT CLAY

Cu = 25kPa

−3.436

SAND

φ = 37.1o

Bending Moment (kN.m)

Dep

th (

m)

−400 −200 0 200 400 600−10

−8

−6

−4

−2

0

2

Shear Force (kN)−100 0 100 200 300

−10

−8

−6

−4

−2

0

2

Pressure (kN/m)

Jeremic 4

p− y Response for Single Pile inLayered Soils

0 2 4 6 8 10 120

50

100

150

200

250

300

Lateral Displacement y (cm)

Late

ral P

ress

ure

p (k

N/m

)

Depth −0.322Depth −0.537Depth −0.752Depth −0.966Depth −1.181Depth −1.396Depth −1.611Depth −1.825Depth −2.040Depth −2.255Depth −2.470Depth −2.684

0 2 4 6 8 10 120

50

100

150

200

250

300

Lateral Displacement y (cm)La

tera

l Pre

ssur

e p

(kN

/m)

Depth −0.322Depth −0.537Depth −0.752Depth −0.966Depth −1.181Depth −1.396Depth −1.611Depth −1.825Depth −2.040Depth −2.255Depth −2.470Depth −2.684

• Influence of soft layers propagates to stiff layers and vice versa

• Can have significant effects in soils with many layers

Jeremic 5

Pile Group Simulations

• 4x3 pile group model and plastic zones

Jeremic 6

Out of Plane Effects

• Out-of-loading-plane bending moment diagram,

• Out-of-loading-plane deformation.

Jeremic 7

Load Distribution per Pile

0 1 2 3 4 5 6 7 8 9 10 115

6

7

8

9

10

11

12

13

14

15La

tera

l Loa

d D

istr

ibut

ion

in E

ach

Pile

(%

)

Displacement at Pile Group Cap (cm)

Trail Row, Side PileThird Row, Side PileSecond Row, Side PileLead Row, Side PileTrail Row, Middle PileThird Row, Middle PileSecond Row, Middle PileLead Row, Middle Pile

Jeremic 8

Piles Interaction at -2.0m

• Note the difference in response curves (cannot scale single pile

response for multiple piles)

Jeremic 9

Comparison with Centrifuge Tests

0 1 2 3 4 5 6 7 8 9 1015

20

25

30

35

40

45

Late

ral L

oad

dist

ribut

ion

in e

ach

row

(%

)

Lateral Displacement at Pile Group Cap (cm)

FEM − Trail RowFEM − Third RowFEM − Second RowFEM − Lead RowCentrifuge − Trail RowCentrifuge − Third RowCentrifuge − Second RowCentrifuge − Lead Row

Jeremic 10

Seismic Behavior of Piles

• Example run for a single pile:

• TFixedBasen = 1.3s.

• TSFSIn ≈ 3.0s,

Jeremic 11

Fourier Amplitude Spectra

Jeremic 12

Displacements of a Single Pile

Jeremic 13

Detailed FEM Analysis

1. Laterally spreading grounds: influence of the type of top nonliquefied soil (loose sand, dense sand, soft clays, hardclays), size and shape of piles and pile cap (single piles, pile group, small cap, large cap), ground surface slope onthe forces applied to the foundation system by the laterally spreading ground.

2. Passive failure of the nonliquefied crust – unloads piles

3. If soil in the nonliquefied crust does not fail – increase lateral pressure on pile foundations

4. The pile foundation might significantly reduce the lateral spreading.

Jeremic 14

Counter Measures

• Soil fails, relieves the structure (weaken the soil around so that it

actually fails!)

• Soil liquefies, changes input motions (reduction, active control by

controlled liquefaction!)

Jeremic 15

References

References

[1] Architectural Institutive of Japan. Recomendation for design of building foundations, 1988.

[2] Boulanger, R. W., Wilson, D. W., Kutter, B. L., and Abghari, A. Soil–pile–suptestructure interactionin liquefiable sand. In Transportaion Research Record (1997), vol. 1569, National Academy Press, pp. 55–64.TRB, NRC.

[3] Japanese Road Association. Specification for highway bridges, 1980.

[4] Japanese Road Association. Specification for highway bridges: Part V Seismic Design, 1996.

[5] Liu, L., and Dobry, R. Effect of liquefaction on lateral response of piles by centrifuge model tests. In NCEERBulletin, vol. 9:1. National Center for Earthquake Engineering Research, January 1995, pp. 7–11.

[6] Lok, T. M., and Pestana, J. M. Numericla modeling of the seismic response of single piles in soft claydeposits. In Proceedings of the Fourth Caltrans Seismic Research Workshop (Sacramento, CA., July 9-11 1996),Caltrans Engineering Service Center.

[7] Wang, S., Kutter, B. L., Chacko, J., Wilson, D. W., Boulanger, R. W., and Abghari, A.

Nonlinear seismic soil–pile-structure interaction. Earthquake Spectra 14, 2 (1998). Earthquake EngineeringResearch Institute.

[8] Wilson, D. W., Boulanger, R. W., and Kutter, B. L. Lateral resistance of piles in liquefying sand. InOTRC Conference in Honor of Lymon Reese (1999), ASCE, Geotechnical Special Publications.

[9] Yokoyama, K., Tamura, K., and Matsuo, O. Design methods of bridge foundations against soil liquefactionand liquefaction induced ground flow. In 2nd Italy–Japan Workshop on Seismic Design and Retrofit of Bridges(Rome, Italy, 27-28 Feb. 1997), p. 23 pages.

Jeremic 16