Hydraulic and volume change behaviors of compacted highly expansive soil under cyclic wetting and drying

Abstract

The wide engineered application of compacted expansive soils necessitates understanding their behavior under field conditions. The results of this study demonstrate how seasonal climatic variation and stress and boundary conditions individually or collectively influence the hydraulic and volume change behavior of compacted highly expansive soils. The cyclic wetting and drying (CWD) process was applied for two boundary conditions, i.e. constant stress (CS) and constant volume (CV), and for a wide range of axial stress states. The adopted CWD process affected the hydraulic and volume change behaviors of expansive soils, with the first cycle of wetting and drying being the most effective. The CWD process under CS conditions resulted in shrinkage accumulation and reduction in saturated hydraulic conductivity (ksat). On the other hand, CWD under CV conditions caused a reduction of swell pressure while has almost no impact on ksat. An elastic response to CWD was achieved after the third cycle for saturated hydraulic conductivity (ksat), the third to fourth cycle for the volume change potential under the CV conditions, and the fourth to fifth cycle for the volume change potential under the CS conditions. Finally, both swell pressure (σs) and saturated hydraulic conductivity (ksat) are not fundamental parameters of the expansive soil but rather depend on stress, boundary and wetting conditions.