A method of horizontal slices has been suggested for obtaining seismic passive earth pressure distribution by considering seismic forces in a pseudo-static manner. Only planar rupture surfaces have been considered and hence wall friction angle has been restricted upto one-third the soil friction angle. This approach results in the same seismic passive earth pressure coefficients as that obtained by Mononobe-Okabe approach, besides giving additional information about the distribution of earth pressures. It has been found that in the seismic case, passive resistance acts at a point other than at 1/3rd from the base of the wall. Under seismic conditions, the extension of failure zone is more than that under static conditions.
This method is an extension to Wang’s approach and is suggested for determining the seismic passive earth pressure distribution for a rigid inclined retaining wall supporting cohesionless backfill.
Analytical Model
The method of horizontal slices is considered in the analysis. In Fig.2.39a, a rigid retaining wall of vertical height H, supporting dry, homogeneous cohesionless backfill material with horizontal ground is shown. The seismic forces are considered as pseudo-static forces along with other static forces. The equilibrium of each elemental slice is considered. It is assumed that the occurrence of earthquake does not affect the basic soil parameters: soil friction angle f and soil unit weight  . |
