重复采动顺层岩质斜坡变形破坏动态演化规律研究

Dynamic evolution law of deformation and failure of the bedding rock slope induced by the underground repeated mining activities

在顺层岩质斜坡下覆岩层中进行采煤活动极易诱发滑坡、崩塌等地质灾害,严重威胁人民群众的生命和财产安全。运用UDEC离散元数值模拟方法,研究了近距离煤层群重复开采对其上覆顺层岩质斜坡变形破坏的动态演化规律。结果表明:1)重复开采导致斜坡的滑移范围扩大,坡面附近的下沉位移明显增加,且超过采高,同时坡肩附近的水平位移加剧,超过单层开采时的2倍;2)采动斜坡裂缝具有明显的动态阶段性发育特征,单层采动时坡面中下部临时性裂缝发育过程为“积累—产生—扩展—缩小闭合”,坡面上部及坡顶未贯通至滑面的裂缝发育过程为“积累—产生—扩展—稳定”;3)在重复采动影响下,部分临时性裂缝和未贯通裂缝均开始活化,其发育过程为“活化—扩展—稳定”,最终转化为永久性裂缝,同时坡体内出现离层,横向裂缝显著增多,坡表产生更多细小开口的裂缝群;4)重复采动不仅会导致新裂缝的产生,也会加剧横向裂缝的产生和扩展,使得坡体更加破碎,稳定性逐步降低。研究成果为采动顺层岩质斜坡变形破坏机理研究奠定基础,为采动顺层岩质斜坡稳定性分析提供参考。

Coal mining activities under bedding rock slopes can easily induce geological disasters such as landslides and collapses,which seriously threaten the safety of people's lives and property.In this paper,the UDEC discrete element numerical simulation method is used to study the dynamic evolution law of deformation and failure of overlying bedding rock slope caused by repeated mining of close coal seam group.The results show:(1)During single-layer mining,the subsidence of the slope is small,and only a small range of slip occurs at the foot of the slope,while repeated mining leads to the expansion of the slip range of the slope,and the subsidence displacement near the slope surface is significantly increased and exceeds the mining height.At the same time,the horizontal displacement near the shoulder of the slope is intensified,which is more than twice that of single-layer mining;(2)The mining-induced slope cracks have obvious dynamic stage development characteristics.The development process of temporary cracks in the middle and lower part of the slope surface during single-layer mining is'accumulation-generation-expansion-reduction and closure'.The development process of cracks in the upper part of the slope and the top of the slope not penetrated to the sliding surface is‘accumulation-generation-expansion-stability';(3)Under the influence of repeated mining,some temporary cracks and unpenetrated cracks start to be activated,and the development process is‘activation-expansion-stability',which eventually transforms into permanent cracks.Besides,there is delamination in the slope,so transverse cracks increase significantly,and more cracks with small openings appear on the slope surface;(4)Under the influence of underground mining,the slope does not only produce vertical cracks but also produces transverse cracks along the joint plane,resulting in discontinuous deformation of the slope.Repeated mining can not only lead to the generation of new cracks but also aggravate the generation and expansion of transverse cracks,making the slope more broken and the stability gradually reduced.The research results lay a foundation for the study of deformation and failure mechanism of mining bedding rock slope,and provide a reference for the stability analysis of mining bedding rock slope.