地下采空诱发陡倾层状岩质斜坡失稳机制研究

 我国西南灰岩山区的褶皱山体经长期强烈的地质抬升运动与河流侵蚀，山体呈现出中上部厚层-巨厚层灰岩地层陡峭，下部页岩、泥岩地层平缓的“靴状”地貌形态，加之下部煤层、铝土矿层的开采，成为我国大型层状岩质崩滑灾害的高发区。本文以重庆武隆鸡冠岭陡倾层状岩质斜坡滑动为例，采用FLAC3D模拟分析了地下采空诱发陡倾层状岩质斜坡“弯曲变形-层间错动-采矿加速倾倒变形-下伏岩体阻滑-下伏岩体剪切破坏-整体失稳”的渐进失稳过程，认为鸡冠岭山体滑动是一类层状岩体的倾倒-滑移失稳的复合破坏模式。模拟结果表明：(1) 陡倾临空的斜坡在长期重力作用下，坡体沿山梁方向发生蠕滑变形，坡体逐渐产生拉裂缝；同时由于该斜坡位于背斜核部附近，应力集中导致上覆层状岩体呈现出弯曲变形的特征；(2) 长期岩溶作用加速坡体裂缝的发育与扩张；(3) 斜坡下部煤层开采时，导致鸡冠岭山梁发生应力发生重分布，上覆层状岩体逐渐发生层面分离，层状岩体下部产生裂缝，岩体强度逐渐降低；(4) 当斜坡下部煤层逐渐采空后，上覆层状岩体变形急剧增大，发生倾倒破坏，挤压矿层下伏稳定岩体，发生剪切滑移，最终从临空处剪出形成高速碎屑流。因此，对于西南灰岩褶皱山区，认识长期地下采空对层状山体的扰动作用，对大型灰岩山体防灾减灾与风险区划具有重要的现实意义。

FAILURE MECHANISM OF STEEPLY INCLINED ROCK SLOPE INDUCED BY UNDERGROUND MINING

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.