A four elements porous model to estimate the strength of unsaturated soils

Abstract

One of the most prevalent relationships for effective stresses on unsaturated soils was proposed by Bishop in the middle of the last century. However, only recently Bishop’s effective stress equation has been implemented in various constitutive models for unsaturated soils. These models have the advantage of naturally including the hydro-mechanical coupling that has been experimentally observed on these materials. Unfortunately, the problem of properly evaluating Bishop’s parameter χ still remains unsolved. This paper presents the results of a solid-porous model used to determine the value of Bishop’s parameter χ and evaluate the strength of unsaturated soils. These theoretical results are compared with a series of triaxial test performed on a silty sand subjected to different suctions in wet and dry paths. These comparisons show that the porous model proposed herein can be used to estimate the strength of unsaturated soils for both the wetting and the drying paths.