Microstructural Investigation of Soil Suction and Hysteresis of Fine-Grained Soils

Abstract

The relationship between soil suction and degree of water saturation (also known as the soil-water characteristic curve or SWCC) for a given soil depends on a number of variables such as the soil type, mineral type, fluid type, pore size distribution, and anisotropy. In addition, the SWCC is found to exhibit a form of hysteresis, in that it is different in wetting and drying. Design of structures founded on unsaturated soils requires an in-depth microscopic understanding of the variables controlling SWCC and the underlying hysteresis. Most of the past basic studies have focused on granular materials, with solid particles represented by spheres. The present study is focused on clayey soils involving platelike solids. The analysis method of molecular dynamics (MD) is used to understand the nature of clay-water capillary meniscus. On the basis of the observations from the MD analysis and the Young-Laplace equation, a model is proposed for predicting SWCC and the associated hysteresis. The microscopic parameters needed for the model are obtained by analyzing the fabric of numerical specimens prepared by the discrete-element method (DEM) of analysis of an assembly of clay particles. The results are shown to be consistent with experimental observations.