Study on the Destabilisation Pattern and Volumetric Water Content Evolution Characteristics of Underground Mining Rock Formations Under Heavy Rainfall Conditions

In order to study the stability of rock layers and the change in volumetric water content at different stages of mining under an environment of heavy rainfall, a self-developed large-scale open-pit-to-underground-mining similar physical model was used, and the intensity of continuous rainfall was set at 40 mm/h. The results of this study show that fissures accelerated the instability of rock strata, and when spreading to different rock strata, they were prone to form subsidence cracks and produce collapse zones. The volumetric water content is closely related to the stability of the rock formation. An 'arch-shaped collapse zone' was formed in an interval of (0.9 similar to 1.8 m), and a convex spreading zone of volumetric water content was formed in an interval of (1.2 similar to 1.6 m). The infiltration line shows different diffusion patterns in different mining stages. In the early stage of mining, the volumetric water content infiltration line is roughly parallel to the slope; in the middle stage of mining, the infiltration line diffuses parallel to the two ends of the interface with the slope and diffuses convexly in the middle; in the late stage of mining, the infiltration line shows a pattern of rapid diffusion in the lower area, rapid diffusion in the middle area, and slow diffusion in the middle area. Therefore, in the process of the mining stage, it is necessary to focus on mining area fissure changes and monitor the point water content for sudden changes and other indicators. This study has certain guiding significance for safe production.