The Concept of Effective Stress in Unsaturated Soils

This chapter talks about the concept of effective stress in unsaturated soils. The effective stress concepts are compared to the results of an experimental study on a compacted silty sand. The following points are examined: the behavior before failure, the influence of the capillary pressure on the maximum strength, the validity of an effective stress approach based on a simple microstructural model for unsaturated porous media to interpret the results. The results from all these tests provide a fairly broad picture of the properties of the sand, from nearly dry to nearly saturated, from the elastic to the perfectly plastic domain. The residual material exhibits original properties with the grain size distribution of a fine sand, on the one hand, and noticeable plasticity, on the other hand that results in large changes in capillary pressure.