Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 342

10.3. Method for analyzing seismic risk

A method for analyzing seismic risk is currently being re-evaluated in France by
a panel of experts established by the Ministry of Ecology. The following section
provides a general overview as well as my own contribution to this topic.

10.3.1. SeismicclassificationofdamsinFrance

Seismic risk is defined by connecting seismic hazard, the vulnerability of a given
dam shaken by a major seismic loading, and the potential risk to the downstream
site. A panel of experts set up and led by the Technical Department of Electrical
Energy, Large Dams and Hydraulics has already made a risk assessment and
produced a method for classifying dams in relationship to seismic risk [DUB 03].
The purpose of this classification is to determine which dams need to undergo a
safety re-evaluation. The three criteria mentioned above are given a coefficient
whose value decreases whenever risk increases.

The coefficient Cs characterizes the risk of exposure to a major earthquake. It
includes the intensity of a historically likely maximum earthquake (SMHV). Its
values are presented in Table 10.1.

Coefficient Cv represents the vulnerability of a given dam subjected to a major
earthquake. It has four components:

− the type of dam (C1);

− its age and behavior (C2);

− the type of foundation soil (C3);

− the slopes of the reservoir (C4).

Coefficient Cr characterizes the potential risk for the downstream site. It
represents the energy released by the sudden failure of the reservoir. It is correlated
to the number of victims after failure (not due to seismic loading) of large dams. It is
calculated as a function of the parameter 2 H × , H being the dam height in
meters and V the volume of the reservoir in millions of cubic meters.