Hysteresis soil-water characteristic curves of highly expansive clay

Abstract

The main objective of this study is to evaluate the hysteresis of soil–water characteristic curves (SWCC) of highly expansive clay subjected to wetting and drying cycles. Variables considered included hysteresis suction range (i.e. low and high suction ranges), suction determination technique (vapour equilibrium technique, axis translation technique and contact filter paper technique) and initial specimen condition. Experimental results revealed that the degree of SWCC hysteresis was higher in the low hysteresis suction range (less than 1.5 MPa) than the high hysteresis suction range (greater than 1.5 MPa). The results further revealed notable difference between matric and total SWCCs of this expansive clay. Furthermore, a hysteresis was observed that is inherent to suction determination technique and is independent of soil characteristics. Also, it was concluded that initial specimen condition (i.e. as-compacted and saturated) had a significant impact on degree of hysteresis, especially in the low suction range. Plausible explanations of observed trends in view of soil–water retention mechanism were provided. Finally, volumetric strains during drying and wetting paths were evaluated and its impact on SWCC was assessed.