Inclusion of hydraulic hysteresis in a new elasto-plastic framework for unsaturated soils

Experimental results from cycles of wetting and drying on unsaturated compacted clays show forms of irreversible volume change that cannot be predicted by conventional elasto-plastic models for unsaturated clays. These additional forms of irreversible behaviour are attributed to the occurrence of hydraulic hysteresis in the variation of degree of saturation. A new form of elasto-plastic model, incorporating the influence of hydraulic hysteresis, is presented in qualitative form. The proposed modelling framework is able to predict either net swelling or net shrinkage over a cycle of wetting and drying (depending on the previous history of compaction and variation of net stress and suction).