Geoscience Reference
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Multiscale Geomechanics
Even if these results require validation relative to observations on real structures,
these numerical studies have helped to reveal the mechanisms and parameters that
govern the behavior of piles installed in granular soil and loaded axially at a low
velocity, considering the permeability of the surrounding soil.
9.5.3.
Earth and rockfill dams
To illustrate the contribution of numerical methods in the field of earth dams, we
present the example of the El Infiernillo dam in Mexico. In this example, we focus on
two aspects. The first concerns the methodology of identifying the model parameters
for a real structure containing rocks, which is particularly difficult to characterize.The
second example relates to the hardening induced during loading and its subsequent
influence on the response of the structure. This dam is of particular interest because its
materials have been the subject of several studies and because it has undergone regular
auscultations from the time it was built and during the earthquakes which hit the area.
The dam, whose maximum cross section is shown in Figure 9.34, is a zoned dam
with a height of about 140 m. It consists of a core of low plasticity silty sand (
I
p
=
26%=45w
L
%
), separated from the rockfill by well graded materials of the lateral
transition zones. It is located on an area of high seismicity of the Pacific plate.
Ever since its construction, it has suffered from several earthquakes. The strongest
ones were those of March 14, 1979 with a magnitude of 7.6 on the Richter scale,
and those of September 19, 1985 with a magnitude of 8.1. For the former, with the
epicenter located at a distance of 134 km, a maximum acceleration of 0.1 g was
noted at the outcropping rock. For the second earthquake, the epicenter was at 68 km
and the maximum acceleration was 0.13 g. For both earthquakes, the record showed
accelerations on the crest, the downstream face, and the foundation rock.
Figure 9.34.
Maximum cross-section of the El Infiernillo dam including different zones
and monitoring points: zone 1: core of silty sand; zones 2 and 3: transition zones; zone 4:
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