Seismic ground response analysis of unsaturated soil deposits

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 incorporating suction effects on G/G0 and D curves. Seismic ground response analyses were done with the computer program EERA for three sets of soil profiles, which are included in saturated, constant and linearly variable suction unsaturated soil deposits. The results of current study present the magnitude of variation in natural frequency, amplification ratio and spectral acceleration of unsaturated soil deposits.