Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 344

Hence, the dams can be classified into three groups:
− dams located in moderate to significant seismic zones, including the zones
with Cs = 1, which require a detailed safety verification;
− dams located in a zone of low seismicity with Cs = 2, but highly prone to
seismic loading or to submersion due to landslide within the reservoir;
− other dams without any particular danger.
10.4. Evaluation of seismic hazard
A panel of experts was established in 2009 in France by the Ministry of Ecology
in order to create a method for evaluating seismic hazard. Numerous discussions on
how to meet the ever-growing social demand for better protection took place. As a
result, the level of the probability of a maximum earthquake was raised. The rules
are:
− to define the scenario for the different situations of dimensioning;
− to establish the seismic level for each situation;
− to characterize the seismic loading for each level;
− to define the accelerographs to be used.
10.4.1. Scenariosfordimensioningaparticularsituation
The method for dimensioning must include the verification of the durability of
the geo-structure in accordance with its use (water stocking, control of the
downstream flow and the upstream level) and its main functions (waterproofing,
stability, filtration, drainage, evacuation and protection) during each life phase:
construction and operation. A seismic loading will interfere with the reservoir.
Major earthquakes being a rare occurrence, we have to study two of the three
types of scenarios proposed by the Euro Code: that corresponding to rare conditions
(called transitory) and that corresponding to extreme conditions (called accidental).
Indeed, we have to distinguish at least one level of the average seismic loading,
cumulated with rare events, and one high level not cumulated with other loadings.
10.4.2. Choiceofseismiclevels
The ICOLD proposes four levels of seismic intensity, classified in decreasing
order of occurrence or by increasing intensity: