多层浅埋煤层开采触发岩溶坡体动力崩滑机制研究

Dynamic formation mechanism of a karst landslide triggered by mining of multiple-layer&shallow-seated coal seams

因内外动力地质作用活跃和人类工程活动频繁致使我国西南岩溶山区坡体灾害频发,进行该类灾害防控的相关研究必要而迫切。采用原位地质详查、全域块体离散元数值模拟和工程地质力学理论分析,选择贵州纳雍张家湾普洒滑坡为研究对象,系统提出了该类“井工开采诱发型”滑坡的致灾特征、主控触发因素和动力成灾机制。结果表明:(1)该滑坡动力崩滑的影响因素包括高陡坡体微地貌、“上硬下软”岩性组合、斜坡岩体结构和物理化学风化等主导因素和多层浅埋采空区、强降雨和采掘爆破振动等触发因素,其中前者的存在或长期作用较为明显地降低了原始坡体的稳定性,而后者的存在或短期作用急剧地劣化了坡体地质条件并最终触发了坡体的“临界崩滑”;(2)该滑坡在采空区和强降雨作用下形成的“渐进变形”具有明显的“整体下座”和“顺时针旋转”特征,其中“整体下座”为“井工开采诱发型”滑坡的典型特征,其为受区内井工开采引起的地表开采沉陷所致;(3)邻近坡体的采掘爆破振动最终触发该滑坡形成“临界崩滑”后,其后续动力响应可细化为“解体破碎→铲刮滑床→碎屑流动→堆积稳定”4个阶段。最后,基于分析驱动该滑坡各阶段动力响应的力学作用类型及其效应,即:坡体岩溶裂隙渗透压力、竖向和水平爆破振动应力、坡脚处剪切应力、采空区边界卸荷应力和采空区中冒落岩块压实过程产生的侧向膨胀应力等及其岩体破裂效应,系统提出了考虑其崩滑全程力学模式演变的动力崩滑机制。

Catastrophic geo-hazards have occurred frequently in the karst areas of Southwestern China for these years because of internal,external geologic processes and human engineering activities,which makes it urgently necessary to reveal their triggering mechanisms for their consequences controlling.Detailed site geological investigation,full-scale block distinct-element-code modeling and related engin-eering geological analysis were conducted to recognize main characteristics,controlling factors and dynamic formation mechanism of a so-called underground mining-induced landslide.Results on the Pusa landslide show its dynamic formation is influenced by micro-landform,rock strata types,rock mass structure,weathering,goaf,heavy rainfall and,especially blasting vibration during underground developing and mining,i.e.controlling factor.Based on the numerical modeling,whole subsidence and clock-wise rotation are obvious characteristics of deformation caused by the goaf and the heavy rainfall during pre-failure of the landslide.What’s more,the whole subsidence which was caused by the goaf is one of the key characteristics of the underground mining-induced landslide.After the landslide behaves its critical failure,following dynamic responses include shattering,scraping off part top of the bed,debris flowing and final depositing.Finally,the dynamic formation mechanism is proposed based on evolution of main forces contributing the Pusa landslide.The forces are actuated by the seepage stress,vertical and horizontal blasting stresses,shear stress,unloading stress and dilation stress caused by the caved rock mass.