Model framework for structure and volume changes in cracking expansive clay soils

摘要

This paper presents a review of research on the structure of heavy clay soils and their volume change behaviour in response to changes in water content. It is based on a soil fabric model that considers the soil to be composed of a packed array of discrete aggregate blocks (peds), each bounded by surfaces that represent potential planes of weakness. Within these blocks, there exist hierarchies of structural units and pore structures. When the soil is in a fully swelled state the ped surfaces, and hence the soil blocks are in intimate contact. As the soil undergoes drying, the soil experiences three stages of shrinkage in succession, each with its own particular characteristics. These are the structural, normal and residual shrinkage phases. On the basis of the considered literature, a theoretical framework for a cracking swelling clay soils is outlined, that is sufficiently general to describe many of the observed soil behaviours, yet sufficiently simple to accommodate numerical implementation. The importance of a persistent crack structure within the soil on its mechanical and hydrophysical behaviour is emphasised.