Suction can change the dynamic material properties of soil including the small-strain and strain-dependent shear modulus and damping. These changes influence the seismic site response of unsaturated soil layers by affecting the wave propagation mechanisms, acceleration amplification and deamplification, and seismically induced settlements. The higher shear modulus of unsaturated soils due to the presence of inter-particle suction forces could result in a different site response. To study this behavior, a set of equivalent linear site response analysis were performed using DEEPSOIL program. A 30-m layer of sand with different constant suction profiles was modeled under Northridge earthquake motion with different scale factors. Bishop’s single-parameter effective stress approach was implemented to incorporate suction into the effective stress equation. The site response was different in soils with various suction levels especially in shallow ground.

The objective of this paper is to pave the path for considering the effect of partial saturation on the site response analysis. A modified Bishop’s effective stress equation was employed to define the soil dynamic properties. Then, the estimated values were implemented in an equivalent linear site response analysis using DEEPSOIL software.