Effect of drying–wetting cycles on the hydromechanical behaviour of compacted coal gangue

Abstract

Compacted coal gangue is often used as subgrade soils in the South-central China. To further understand the effects of drying-wetting (D-W) cycles on the hydro-mechanical behavior of compacted coal gangue subgrade, this paper presents a series of laboratory test results on reconstituted coal gangue subjected to multiple D-W cycles. The effect of vertical load and compaction parameters on the soil deformation behaviors during hydraulic loading are fully discussed. Based on the laboratory investigations, the shrinkage strain was found to decrease with the increase of the initial dry density, however, it increased with the increase of vertical load. Experimental results also revealed that the variation of soil water content is more pronounced in the 1^st D-W cycle. The characteristics of the void ratio and water content change during D-W cycles was investigated and the shrinkage behavior (e - w) was obtained. Significant hysteresis was detected during the D-W cycles, and the size of hysteresis loop was found to decrease with the increase of D-W cycles while increase with the increase of vertical load. In addition, the D-Ws cycles were found to influence the pore volume at the microscopic scale, where both the volume of inter-aggregate pore and intra-aggregate pore were found to decrease as the hydraulic loading increased.