Hydromechanical behavior of unsaturated swelling clays: review

Abstract

Expansive soils are materials composed mainly of active minerals of the smectite family, where montmorillonite is an essential member of that group. These types of soils tend to undergo volumetric changes due to variations in moisture content. Many geotechnical engineering practices, such as dam core design or subgrade compaction, require a thorough evaluation of the response of these soils to determine placement conditions. However, the main problem in evaluating the mechanical response of this type of soil lies in the nonlinear nature, which limits the use of most classical constitutive models that apply the basic rules of elastoplasticity. In this study, an analysis is carried out to understand the hydromechanical behavior of expansive soils in saturated and unsaturated conditions. Direct and indirect physical evidence is presented and discussed to evaluate the hydraulic response of the soil structural elements responsible for these adverse dynamics from a global (expansive phenomena as a whole) and individual (swelling and shrinkage) perspective. Since the response of these soils is hydrostatic dependent, the locus of water movement in porous media is examined, starting from the Richards equation (1931), in order to consider the flow mechanisms in unsaturated media under transient conditions.