On the mechanical damage to tailings sands subjected to dry-wet cycles

The safety of tailings ponds is considered to be one of the greatest environmental challenges in the field of energy and mining engineering. Impacted by factors such as rainfall infiltration, recycling water, dry beach face evaporation, tailings sands close to the saturation line in tailings ponds are subject to frequent dry-wet (DW) cycles. DW cycles aggravate the potential for damage to the mechanical properties of tailings sands, reduce the safety of tailings ponds, and pose a threat to the life and property of downstream residents. However, the behavior of the mechanical properties of tailing sands subjected to DW cycles due to damage to the tailing sands is still poorly understood from a stability analysis perspective. Therefore, we have conducted laboratory tests, including direct shear and matric suction tests, on tailings sands under conditions of DW cycling to improve our understanding of the DW cycling process of tailings sands. Based on the test results, we propose an innovative damage mechanism of shear strength, cohesion, and internal friction angle of tailings sands in association with DW cycles. We also introduce the cumulative damage rate of cohesion (D-c) and the cumulative damage rate of internal friction angle (D phi) parameters in order to determine the relationship between the number of DW cycles (n) and D-c, and between n and D phi. Finally, the effect of number of DW cycles on the matric suction of tailings sands was analyzed. We found that with increasing number of DW cycles, the soil-water characteristic curve of tailings sands tended to shift to the left. The results of this study provide a foundation for understanding the mechanical behavior of tailings sands under conditions of DW cycles as well as guidelines for the prediction and mitigation of the stability of tailings ponds.