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| Study on failure mechanism of slopes induced by the underground coal mining subsidence |
| SUN Shuwei1，YANG Zhaoxi1，JIA Peizhi1，WANG Xiaolong1，LI Guojun2 |
(1. School of Energy and Mining Engineering，China University of Mining and Technology(Beijing)，Beijing 100083，China；
2. School of Safety Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221116，China)
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Abstract The underground mine workings cause the movement of overlying rock layers and changes in stress fields，leading to the deterioration of rock properties in slopes，which can easily cause disasters such as slope landslides. This study compared the failure process of the underground mine-slope system under different underground mine working conditions using bottom friction tests and numerical simulations. Thus，the failure mode and deformation mechanism of the slope under the influence of underground coal mining subsidence were analyzed. The findings include：(1) the effect of underground coal mining subsidence on slopes mainly includes reducing the integrity and strength of the slope rock mass，changing the inclination angle of the slope rock layer，enhancing the tension effect of the slope surface and causing cracking，and changing the geometric shape of the slope. (2) The fracture mechanism of the overlying rock strata is the gradual bending and collapse of the rock strata towards underground mine workings under the action of gravity. The shape of fracture surface of the rock strata develops in a geese-like pattern with the centerline of the underground mine working as the axis of symmetry in the deep field，and is connected to the tensile fracture in the slope surface in the near-slope field. (3) the mechanism of overlying slope failure induced by underground mine workings can be divided into two types：compression type and traction type. Compression type slope failure usually occurs in the lower slope of mining subsidence，and the process was divided into stages such as overlying rock collapse，subsidence compression，and slope sliding；Traction type slope failure usually occurs on the upper slope of mining subsidence，and the process was divided into stages such as collapse of overlying rock strata，traction and tearing，and slope sliding. (4) the geological structure has a significant impact on the instability and failure process of the overlying slope. When the rock layer of the slope was in a bedding orientation，the fracture surface pattern on both sides of the overlying rock layer rotated towards the dip direction，and the deformation and failure range of the slope induced by the mining subsidence was relatively large；When the rock strata were in a reverse inclined orientation，the effect of the underground mine workings with the same position and burial depth on the displacement of the slope was significantly reduced. The research results can provide reference for the identification of slope disasters in coal mining subsidence areas and the safety prevention of open-pit-underground mining transition projects.
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