FAILURE MECHANISM OF STEEPLY INCLINED ROCK SLOPE
INDUCED BY UNDERGROUND MINING
LI Bin1，WANG Guozhang2，FENG Zhen1，WANG Wenpei3
(1. Chinese Academy of Geological Sciences，Institute of Geomechanics，Key Laboratory of Neotectonic Movement and Geohazard，Ministry of Land and Resources，Beijing 100081，China；2. Shanghai Jiao Tong University，Shanghai 200240，China；
3. China Institute of Geological Environment Monitoring，Beijing 100081，China )
Abstract：The folded mountains in Chinese southwest limestone mountainous areas have been undergoing long-term active geologic uplift and river erosion，leading to a“boot”-shaped morphology as steep and thick limestone strata in the upper layers，while gentle shale and mudstone strata in the lower layers. Combined with the exploitation of coal and bauxite seams，this region has become a highly hazard-prone area of large-scale stratified rock collapse in China. In this paper，the steeply inclined Jiguanling rockslide in Wulong，Chongqing is taken as an example. FLAC3D is used to simulate and analyze the progressive failure process of steeply inclined rocks induced by underground mining，i.e.，“rock bending-interbedded shearing-toppling-toe breakout-overwhelming slide”. It is considered that Jiguanling rockslide is a compound failure mode of stratified rock mass with toppling and sliding. Simulation results show that：(1) under long-term gravity the steep slope creeps along the mountain ridge，gradually producing tensile cracks；meanwhile，due to the slope situated near the anticline core areas，the stress concentration results in bending deformation of the overburden strata；(2) the long-term karstification accelerates the development and widen of slope fissures；(3) the coal mining induces stress redistribution at Jiguanling mountain ridge，stratum separation is gradually shown in the overlying rock mass，cracks are formed in the underlying rock mass，and the strength of rock mass is gradually reduced；(4) after the gradual mining，the deformation of overlying rock mass increases sharply with toppling and failure，squeezing the underlying rock mass，leading to shear failure，and finally the collapse-debris flow is formed. Thus，in the southwest limestone folded mountains，the understanding of the effect of underground mining in stratified rocks is important for disaster prevention and mitigation of large limestone mountains as well as risk zoning.
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2015, Vol. 34 
