Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 351

10.5.2. Arecommendedstep-by-stepmethodology

We recommend a step-by-step methodology of seismic analysis in order to
formulate well-founded arguments on geo-structures when considering public
safety. The superposition of different simple approaches appears to be a good
method because it is accessible to most of the consulting firms and because these
approaches are able to justify the structural stability concerning distinct but
complementary physical phenomena. The methodology is developed in seven steps
(see Table 10.3).

Step Method for the seismic analysis of dams

1 Identification

2 Pseudo-static approach of stability

3 Approach of liquefaction

4 Pseudo-dynamic approach to displacements

5 Non-linear dynamic approach to liquefaction

6 Post-seismic approach to residual stability

7 Assessment

Table 10.3. The seven steps and associated methods for seismic evaluation

10.5.3. Identification

The first step concerns the inventory and critical analysis of the data necessary
for the study. These data are in connection with the three phases of the project:
studies, construction and operation. The hypotheses concerning the soil
characteristics are issued from the studies. During the phase of operation,
fundamental information is gathered, which enriches the project data: incidents,
visual observations of abnormal behavior, measurements on the geo-structure, and
maintenance works. The absence of such information leads to the need for
significant investigation programs based on in situ testing. The data needed are
assembled within four site models:

− the geometrical model which fixes the actual dimensions of the dam and the
different soil layers of the foundation. Often, the “as-built drawings” are not
available;

− the geological model that defines the nature of the foundation, the position of
the faults and the intensity of the seismic hazard;