Impact of directly accounting for post-peak strength loss on the dynamic response of a soil column during earthquake loading

Abstract

This paper presents a numerical investigation of the impacts of post-peak strength loss on ground motion amplification and reduction for a soil column with a layer of strain-softening clay. Stress attenuation and amplification were modeled with a one-dimensional soil column using the finite difference program FLAC 8.1 with the PM4Silt constitutive model. Three calibrations of an idealized soil were developed consisting of different rates and magnitudes of post-peak strength loss. Alternative column geometries were devised, each with different clay layers thicknesses to establish how ground surface motions were affected. Impacts were quantified using both a cumulative ground motion intensity (Arias Intensity) as well as different spectral components (base to surface transfer function). The results illustrate that the thickness of the clay layer surface and strength loss in the layer have an impact on the magnitude and frequency content of the earthquake motion measured at the ground surface. The impact of these results on practice and future research needs are presented.