| The response of submerged slopes on the continental shelf to
seismic or storm loading has become an important element in the
risk assessment for offshore structures and "local" tsunami
hazards worldwide. The geological profile of these slopes
typically includes normally consolidated to lightly
overconsolidated soft cohesive soils with layer thickness ranging
from a few meters to hundreds of meters. The factor of safety
obtained from pseudo-static analyses is not always a useful
measure for evaluating the slope response, since values less than
one do not necessarily imply slope failure with large movements of
the soil mass.
This paper addresses the relative importance of different factors
affecting the response of submerged slopes during seismic loading.
The analyses use a dynamic finite element code which includes a
constitutive law describing the anisotropic stress-strain-strength
behavior of normally consolidated to lightly overconsolidated
clays. The model also incorporates anisotropic hardening to
describe the effect of different shear strain and stress histories
as well as bounding surface principles to provide realistic
descriptions of the accumulation of the plastic strains and excess
pore pressure during successive loading cycles. The paper presents
results from parametric site response analyses on slope geometry
and layering, soil material parameters, and input ground motion
characteristics. The predicted maximum shear strains, permanent
deformations, displacement time histories and maximum excess pore
pressure development provide insight of slope performance during a
seismic event. |