COASTAL ENGINEERING - Introduction to Soft Soil Geotechnique: Content, Context and Application - page 281

A
B
A
F d
B
F s
t [s]
Figure 16.14 Wave induced effects on dynamic slope stability
Earthquake impact
Earthquakes and water waves cause a dynamic response of earth slopes.
Earthquakes manifest at the surface as a volumetric force related to the soil mass.
For impermeable soils the saturated soil mass will be triggered, and the effect can
be incorporated as a dynamic addition to the static soil gravity. For permeable soils
the pore water may partly be triggered (via drag forces at micro-scale)
The dynamic energy will mostly be transferred to the solid part. Hence the effect
should be incorporated as a dynamic addition to the gravity of the solid part. Fig
16.15 shows the dynamic response of a large breakwater subjected to a heavy
earthquake, simulated by a numerical simulation model. The response reveals
residual displacements and plastic deformation at the lee side due to pore pressure
build-up. The local weakening of the toe of the lee-side slope may cause the slope
to shift down, allowing waves to erode the core and finally inducing collapse of the
entire structure.