A Four Elements Porous Model to Estimate the Strength of Unsaturated Soils

One of the most successful 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 include the coupling between the hydraulic and the mechanical behavior experimentally observed on these materials. Unfortunately, still remains the problem of properly evaluate Bishop ́s parameter χ. This paper presents the results of a solid-porous model used to determine 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 subject to different suctions in wetting and drying paths. These comparisons show that the porous model proposed herein can be used to estimate the strength of unsaturated soils