Thermal effects on yielding and wetting-induced collapse of recompacted and intact loess

Abstract

Yielding and wetting-induced collapse are two important interrelated aspects of unsaturated loess behaviour. Previous studies on loess were generally conducted under a single temperature condition. The principal objective of this study is to investigate thermal effects on yielding and wetting-induced collapse of recompacted and intact loess. Isotropic compression tests were carried out to determine yield stress at different suctions (0 and 100 kPa) and temperatures (5, 23, and 50 °C). Moreover, wetting tests were conducted at various temperatures and stresses. Results of the wetting tests were interpreted using the measured yield stress at various suctions and temperatures. It is found that yield stress decreases with decreasing suction (wetting-induced softening). The wetting-induced softening of recompacted loess is more significant at a higher temperature. The observed thermal effects on wetting-induced softening are likely because with decreasing suction, the stabilizing interpar-ticle normal force decreases more at a higher temperature. In contrast, when the applied stress reaches the yield stress during wetting, yielding and plastic volumetric contraction can be observed. More importantly, wetting-induced contraction of recompacted loess at 50 °C is about three times of that at 5 °C. The larger contraction at 50 °C is mainly because the wetting-induced softening is larger at a higher temperature.