Seismic Ground Response Analysis of Unsaturated Soil Deposits Using Suction Dependent Shear Modulus and Damping Ratio

Abstract

Seismic ground motion is profoundly affected by geometrical and mechanical properties of soil deposits overlaying bedrock. Local seismic ground response of saturated soil deposits was studied in literature by applying the effects of soil stress state and index properties on the strain-dependent normalized shear modulus reduction, G/G0, and damping ratio, D, curves in an equivalent linear analysis. However, experimental investigations revealed that, G0, G/G0, and D of unsaturated soils are influenced by stress state as well as suction. This study presents the results of linear and equivalent linear seismic ground response analysis of unsaturated soil deposits with considering suction effects on G/G0 and D curves. Seismic ground response analysis was done with the computer program EERA for two sets of soil profiles, which include in saturated, constant and linearly variable suction unsaturated soil deposits. Results show that natural frequency of the soil profile increases as the suction increases.