Experimental study on the deformation mechanism of upper-hard and lower-soft gently dipping rock on high slopes under the mining effect

Complex geological environments characterize karst mountainous areas in southwest China with frequent underground mining activities and large-scale landslide hazards. The purpose of this work was to understand the law of slope subsidence and ground fissure development during mining activities under the upper-hard and lower-soft gently dipping rock slopes. Taking the Pusa collapse in Guizhou Provinceas an example， using similar-model experiments， we studied the surface settlement， internal displacement， interlayer pressure variation rule and features of mining ground fissure development of the slope body under mining activities. The results show that under the action of underground mining， the surface settlement and internal displacement of the slope body increase linearly with the growth of mining length. When the mining length is about 16 times of the mining height， the surface settlement of the test model increases sharply with cracks appearing. The closer the measurement point to the ground fissure， the greater the settlement change rate. The location of ground fissures and the maximum change rate of surface settlement appear roughly in the same area. When the driving face is advancing， the unloading area appears in the roof rock above the goaf where the compressive stress decreases， while the rock mass above the mining face has the interlayer compression area where compressive stress increases. Outside the mining height range of about 20 times above the goaf， the interlayer pressure in the test model is less affected by the disturbance of underground mining activities. The research in this paper has a certain reference significance for the early identification and failure mechanism analysis of landslides under underground mining activities in karst mountainous areas of southwest China.