Evaluating Seismic Stability of Embankment Dams - Multiscale Geomechanics: From Soil to Engineering Projects - page 369

10.6.7.3. Displacements

The failure threshold in displacement corresponds to:

− a vertical settlement greater than 1/3 of the “freeboard”;

− a horizontal displacement greater than 1/3 of the filter thickness or, in the
absence of filter, no higher than 1% of the total height of the dam or to 50 cm.

10.6.7.4. Liquefaction factor

The liquefaction factor is a key parameter that is calculated by the following
relation:

uu −

0

T =

liq

σ − u

yy 0

with:

− u : pore pressure at the time of the study;

− u o : pore pressure after impounding;
− σ yy : vertical stress at the time of the study.

A value of T liq higher than 0.8 is considered to represent the occurrence of
liquefaction.

10.6.7.5. Parameter determination

The model validation was conducted by simulating the behavior of the two dams
of the Van Norman developments in the San Fernando Valley. The determination of
the BRO model parameters is based on laboratory test results, mainly monotonic and
cyclic triaxial testing.

The common procedure consists of the step-by-step determination of the initial
state and, specifically, first the relative density, second the parameters of the shear
and volumetric strain laws, and third the residual strength. This procedure requires
the following experimental data:

− the elastic moduli K max and G max ;
− the curve (G/G max , γ) giving the shear modulus decrease with the shear strain
amplitude;

− the curve (D, γ) giving the damping ratio increase with the shear strain
amplitude;