Simplified Procedure For Estimating Earthquake-Induced Deviatoric Slope Displacements

Simplified Procedure for Estimating Earthquake-Induced
Deviatoric Slope Displacements
Jonathan D. Bray, F.ASCE1; and Thaleia Travasarou2
Abstract: A simplified semiempirical predictive relationship for estimating permanent displacements due to earthquake-induced deviatoric deformations is presented. It utilizes a nonlinear fully coupled stick-slip sliding block model to capture the dynamicperformance of
an earth dam, natural slope, compacted earth fill, or municipal solid-waste landfill. The primary source of uncertainty in assessing the
likely performance of an earth/waste system during an earthquake is the input ground motion. Hence, a comprehensive database containing 688 recorded ground motions is used to compute seismic displacements. A seismic displacement model is developed thatcaptures the
primary influence of the system’s yield coefficient ky , its initial fundamental period Ts , and the ground motion’s spectral acceleration
at a degraded period equal to 1.5Ts. The model separates the probability of “zero” displacement i.e., 1 cm occurring from the
distribution of “nonzero” displacement, so that very low values of calculated displacement do not bias the results. Theuse of the seismic
displacement model is validated through reexamination of 16 case histories of earth dam and solid-waste landfill performance. The
proposed model can be implemented rigorously within a fully probabilistic framework or used deterministically to evaluate seismic
displacement potential.
DOI: 10.1061/ ASCE 1090-0241 2007 133:4 381
CE Database subject headings: Dams; Earthquakes;Displacement; Structural reliability; Seismic effects; Slope stability.

Introduction
The assessment of the likely performance of earth/waste structures during earthquakes is important, because the failure of an
earth dam, solid-waste landfill, natural slope, or constructed earth
embankment can result in significant human and financial losses
and severe environmental impact. Incorporatingprobabilistic
methodologies allow the engineer to quantify the uncertainty in
the assessment of the likely performance of earth/waste slopes.
Simplified procedures for evaluating earth/waste slope stability
are required to bring probabilistic methods into daily practice.
Although some previous efforts have partially addressed this
need, the wealth of new earthquake recordings that have recentlybecome available with more realistic nonlinear, coupled stick-slip
models and probabilistic procedures offers the opportunity to advance the manner that engineers evaluate seismic stability of
earth/waste slopes in practice.
The goal of this paper is to describe a simplified semiempirical
procedure that can be used in the assessment of the likely performance of earth/waste structures that mayslide during earthquakes. The procedure is developed to work within a fully
probabilistic seismic hazard assessment, but it can be used also as
1

Professor, Dept. of Civil and Environmental Engineering, Univ. of
California, Berkeley, CA 94720-1710. E-mail: bray@ce.berkeley.edu
2
Project Engineer, Fugro-West Inc., 1000 Broadway, Suite 200,
Oakland, CA 94607-4099. E-mail: ttravasarou@fugro.comNote. Discussion open until September 1, 2007. Separate discussions
must be submitted for individual papers. To extend the closing date by
one month, a written request must be filed with the ASCE Managing
Editor. The manuscript for this paper was submitted for review and possible publication on June 1, 2005; approved on September 28, 2006. This
paper is part of the Journal of Geotechnical andGeoenvironmental
Engineering, Vol. 133, No. 4, April 1, 2007. ©ASCE, ISSN 1090-0241/
2007/4-381–392/$25.00.

a simple predictive relationship that includes quantification of the
uncertainty of key input variables. Pertinent previous studies are
summarized, and while describing the model used to develop the
“database” of simulated seismic displacements, the key improvements of the proposed...