A pore-network model for hydromechanical coupling in unsaturated compacted clayey soils

The behaviour of deformable unsaturated soils is difficult to characterize with simple relationships. Unsaturated hydraulic properties, namely the soil-water characteristic curve and the hydraulic conductivity function, are dependent on both volume change and degree of saturation, whereas volume change itself often cannot be related to a single stress variable but must be described by independent functions of mechanical loading and suction. It is proposed that a means to obtain these functions is through pore-network modelling, by which it is possible to integrate the phenomena of drainage and volume change and the different effects of suction and mechanical loading. The implementation of a two-dimensional pore-network model is described. A simple algorithm for individual pore volume change is adopted. The model uses pore-size distributions measured by mercury intrusion porosimetry to initially generate the simulated pore grid. Predictions of soil-water characteristic curves, void ratio versus suction curves, pore-size distributions at specific suctions, unsaturated hydraulic conductivity, and compression curves are compared with measured values from two compacted clayey soils.