Effect of rayleigh wave on seismic active earth pressure behind retaining wall.

Abstract

Calculation of seismic earth pressures is very crucial in designing structures like retaining walls, ground anchors etc in earthquake prone area. Limit equilibrium method, limit analysis and method of characteristics are some of the commonly used methods for calculation of seismic earth pressure in seismic zone. Limit equilibrium method is more common and simple compared to other two methods. There are several approaches available in literature till date which calculates seismic earth pressure using limit equilibrium method. Pseudo-static is the oldest one among them. It considers the dynamic nature of earthquake loading in very approximate way without taking any effect of time and seismic waves. Pseudo- dynamic method is an improved method, which incorporates the effect of shear and primary waves for calculating the seismic earth pressure. It is well observed from seismic wave theories that the major energy contribution is from Rayleigh wave which is about 67% of total seismic energy. Even though, Rayleigh wave has not been included in the calculation of seismic earth pressure in the methods available till date. In this paper an attempt has been made to include Rayleigh wave along with shear and primary waves for calculation of seismic active earth pressure. It can be seen that the Rayleigh wave affects the value of seismic active earth pressure considerably. Hence, it can be concluded that the Rayleigh wave affects the seismic active earth pressure and hence needs to be considered while designing retaining walls against seismic activity.