Geoscience Reference
In-Depth Information
CHAPTER 14
SIMPLIFIED SEISMIC SLOPE DISPLACEMENT PROCEDURES
Jonathan D. Bray
1
Dept. Civil & Environ. Engineering, Univ. of California, Berkeley, USA
Abstract.
Simplified seismic slope displacement procedures are useful tools in the evaluation of
the likely seismic performance of earth dams, natural slopes, and solid-waste landfills. Seismi-
callyinducedpermanentdisplacementsresultingfromearthquake-induceddeviatoricdeformations
in earth and waste structures are typically calculated using the Newmark sliding block analogy.
Some commonly used procedures are critiqued, and a recently proposed simplified procedure is
recommended for use in engineering practice. The primary source of uncertainty in assessing the
likely performance of an earth/waste structure during an earthquake is the input ground motion, so
theproposedmethodisbased onthe responseof severalrealisticnonlinear fully coupled stick-slip
slidingblockmodelsundergoinghundredsofrecordedgroundmotions.Thecalculatedseismicdis-
placement depends primarily on the ground motion's spectral acceleration at the degraded period
of the structure and the structure's yield coefficient and fundamental period. Predictive equations
are provided forestimating potential seismic displacements forearth and wastestructures.
1. Introduction
The failure of an earth dam, solid-waste landfill, or natural slope during an earthquake
can produce significant losses. Additionally, major damage without failure can have
severe economic consequences. Hence, the potential seismic performance of earth and
waste structures requires sound evaluation during design. Seismic evaluations of slope
stability range from using relatively simple pseudostatic procedures to advanced non-
linear finite element analyses. Performance is best evaluated through an assessment of
the potential for seismically induced permanent displacements. Following largely from
the landmark paper of Newmark (1965) sliding block analyses are utilized as part of
the seismic evaluation of the likely performance of earth and waste structures. Simpli-
fied Newmark-type procedures such as Makdisi and Seed (1978) are routinely used to
provide a rough assessment of a system's seismic stability. Some of these procedures
are critiqued in this paper, and a recently proposed simplified method for estimating
earthquake-induced deviatoric deformations in earth and waste structures is summarized
and recommended for useinpractice.
