Void Fabric Tensor and Ultimate State Surface of Soils

Abstract

This paper presents a method to characterize the fabric of soils. Attention is focused on the directional distribution of voids in these materials. The mean porosity and void fabric tensor used in the description are obtained by the stereological technique. The use of a void fabric index to quantify the variation of the fabric tensor with deformation is highlighted. The fabric description is also used to expand the critical state soil mechanics framework. A proposal for an ultimate state surface of soils is made. The study shows that the representation of the ultimate state surface is dependent on the choice of the set of pertinent state variables. Its representation in reduced state dimensions may not be unique. The study further shows that the initiation of strain-softening in soils is the result of structural collapse of the solid skeleton. The use of the void fabric index to identify the initiation of collapse is explored.