Saturation effects on ground motion of unsaturated soil layer-bedrock system excited by plane P and SV waves

We investigate seismic ground motion in the free-field, in the unsaturated soil layer overlying bedrock. The unsaturated soil is treated as a poroelastic medium, in which the solid matrix is filled with two coupled fluids (liquid and gas). The bedrock is assumed to be a linear elastic solid. The wave fields in the unsaturated soil-bedrock system for plane P-wave and SV-wave incidence are analyzed based on the fluctuation characteristics of an unsaturated porous medium. The undetermined coefficients of the waves are evaluated and analytical solutions to seismic ground motion of an unsaturated soil-bedrock system are obtained. Numerical results on the effects of saturation on surface displacement for five cases Sr = 0, 0.4, 0.8, 0.99, and 1.0), for different incident angles, wave frequencies, and soil porosity are illustrated. The results show that the existence of a gas phase in the soil has a significant effect on ground motions.