ASCE G-I Case History Night, April 28, 2016

Seismic Earth Pressure Variations in Retaining Walls with Cohesive Backfill Material

Siavash Zamiran, Abdolreza OsouliCivil Engineering Department

April 28, 2016

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Outline• Conducting numerical models to evaluate seismic

earth pressure• Using finite difference method, FLAC software• Assuming soil cohesion for backfill • Assuming soil-wall adhesion• Considering different earthquake loading• Considering hysteretic behavior of soil • Calibrating of the model with centrifuge tests

conducted by Agusti and Sitar, 2013

3Caused by Kobe Earthquake in 1995

Failures of Retaining Walls Due to Earthquake

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Failures of Retaining Walls Due to Earthquake Loading

Caused by Mid-Niigata Prefecture Earthquake in 2004

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Seismic hazard map of the USA

Reference: United States Geological Survey

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New Madrid seismic zone

Reference: United States Geological Survey

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Analytical methods

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2 0 . 5 2

c o s ( )s i n ( )s i n ( )c o s c o s c o s ( ) [1 { } ]

c o s ( )c o s ( )

aeKii

2a e

1 (1 )2 v aP H k K

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Analytical Method Parameters Other ConsiderationsReference Method Wall

AdhesionSlopingBackfill

Surcharge InclinedWall

Distribution ofPressure

TensionCrack

Ghosh et. Al (2008)

Limit-equilibrium (planar failure surface)

x x x x x

Viscone et al (2008)

Upper-bound limit analysis (workrule) (proposed by Chen & Liu, 1990) with log-sandwichfailure surface

x x x

Richards and Shi (1994)

Closed-formelasto-plastic solution (stress equilibrium)

x x x x

NCHRP (2008) Limit-equilibrium (proposed by Shamsabadi, 2006) with planar failure surface

x x x x

Nian and Han (2013)

Stress Equilibrium x x x x x

Das and Puri(1996)

Limit-equilibrium (planar failure surface)

x x x x x

Kim & Greco (2010)

Limit-equilibrium (planar failure surface)

x x x x

Sharma and Ghosh (2010)

Limit-equilibrium (planar failure surface)

x x x x x

Some of the analytical methods which consider backfill cohesion

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Centrifuge Model• Based on study by Agusti and Sitar, 2013• Seismic earth pressure on retaining structures in cohesive soils• UC Berkeley • Sponsored by California Department of Transportation

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Numerical Modeling Geometry

19 m

25 m

36 m

13 m

6 m

4.9 m

3 m

6 m

4.9 m

3 m1.75 m

0.35 m1.5 m

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Soil Properties

• Constitutive model: UBCHYST• Soil type: low plasticity lean clay (CL), called Yolo Loam

from a borrow pit at the centrifuge facility• Density= 2038.7 kg/m3

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Interaction of Wall and Soil

T

kn

ksS

Retaining wall structural element

Soil meshes

min

410( )3

n s

K Gk k

z

Property Unit Value

Shear stiffness GPa 2.53

Normal stiffness GPa 2.53

Shear strength (0.50 of soil cohesion) kPa 7.6

Normal strength (0.50 of soil cohesion) kPa 7.6

Shear friction angle (0.5 of soil friction angle) Degree 15

Normal friction angle (0.5 of soil friction angle) Degree 15

Tension kPa 0

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Computer simulation of retaining wall

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ACCELERATION AND DISPLACEMENT HISTORY

-1-0.8-0.6-0.4-0.2

00.20.40.60.8

0 2 4 6 8 10 12 14 16 18 20

Acc

eler

atio

n (g

)

Time (s)

-10

-5

0

5

10

15

0 2 4 6 8 10 12 14 16 18 20

Dis

plac

emen

t (cm

)

Time (s)

-5-4-3-2-1012345

0 5 10 15 20 25

Dis

plac

emen

t (cm

)

Time (s)

-0.15-0.1

-0.050

0.050.1

0.150.2

0 5 10 15 20 25

Acc

eler

atio

n (g

)

Time (s)

Kobe Kocaeli

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Seismic earth pressure coefficient versus free field acceleration

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1

ΔK

ae

Free-field PGA (g)

UBC13, 15 - with label

Centrifuge table

Kocaeli YPT060-2

Kobe TAK090 -2

Seed & Whitman (1970)

Okabe (1926)

Mononobe & Okabe (1929)

NCHRP,2008

Shukla et al. 2009

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Study phases in progress• Effect of strength properties: cohesion and friction

angle• Effect of different earthquakes• Effect of earthquake intensities• Effect of wall rigidity• Effect of soil-wall interaction• Effect of backfill saturation

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Analyzing the responses • Seismic earth pressure approach

• Analytical: Mononobe-Okabe, Shukla, etc, DOTs

• Displacement approach• Analytical: Newmark method, AASHTO

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Fragility analysis• Based on methodology developed by Argyroudis et. al, NIT, (2013)• Development of fragility functions for geotechnical constructions:

Application to cantilever retaining walls

Definition of damage states

Numerical modeling,

estimation of deformation

based on PGA

Probability of damage VS PGA

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Workshops held in SIUE:• Introduction to Computational Geotechnics, Jan 2016• Numerical Modeling of Foundations Using FLAC3D, Jan 2015• Underground Coal Mine Stability Analysis , Jan 2015• Numerical Modeling in Geotechnical Engineering 2, Oct 2014• Numerical Modeling in Geotechnical Engineering 1, Aug 2014

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Introduction to Computational Geotechnics, Jan 2016

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Numerical Modeling in Geotechnical Engineering, Oct 2014

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Thank you. Questions?

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References• Agusti, G. C., & Sitar, N. (2013). Seismic Earth Pressures on Retaining Structures in

Cohesive Soils (No. UCB GT 13-02). California Department of Transportation.

• Argyroudis, S., Kaynia, A. M., & Pitilakis, K. (2013). Development of fragility functions for geotechnical constructions: Application to cantilever retaining walls. Soil Dynamics and Earthquake Engineering, 50, 106–116.

• Shukla, S. K., Gupta, S. K., & Sivakugan, N. (2009). Active Earth Pressure on Retaining Wall for c-ϕ Soil Backfill under Seismic Loading Condition. Journal of Geotechnical and Geoenvironmental Engineering, 135(5), 690–696.

• Mononobe, N., & Matsuo, H. (1929). On the Determination of Earth Pressures During Earthquakes. In World Engineering Congress 9 (pp. 177–185).