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

Compacted coal gangue is often used as subgrade soils in South Central China. To understand further the effects of drying-wetting (D-W) cycles on the hydromechanical behaviour 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 effects of vertical load and compaction parameters on the soil deformation behaviours during hydraulic loading are fully discussed. Based on the laboratory investigations, the shrinkage strain was found to decrease with the increase in the initial dry density; however, it increased with the increase in vertical load. Experimental results also revealed that the variation in soil water content was more pronounced in the first D-W cycle. The characteristics of the void ratio and water content change during D-W cycles were investigated, and the shrinkage behaviour (e-w) was obtained. Significant hysteresis was detected during the D-W cycles, and the size of the hysteresis loop was found to decrease with the increase in D-W cycles, while it increased with the increase in vertical load. Besides, the D-W cycles were found to influence the pore volume at the microscopic scale, where both the volumes of inter-aggregate pores and intra-aggregate pores were found to decrease as the hydraulic loading increased.