大倾角煤层长壁开采底板非对称破坏形态与滑移特征

Asymmetric failure pattern and slip characteristics of floor of longwall face in steeply dipping seam mining

底板破坏滑移是大倾角煤层开采亟待解决的关键问题之一,以2130煤矿25221大倾角综采工作面为研究背景,采用理论分析、数值计算和现场监测相结合的研究方法,系统研究了底板的破坏和滑移特征。结果表明,在采动应力和支架载荷作用下底板的力学性状发生改变,由层状连续介质状态演化为具有"结构体+结构面"的块裂介质状态;底板沿工作面倾向的破坏形态呈现为下大上小的非对称反拱,其最大破坏深度位于工作面倾向下部区域,且其破坏深度和范围随着煤层倾角的增大而减小;支架载荷对底板破坏影响有限,主要涉及采场直接底岩层;在底板重力倾向分量及支架和相邻块体载荷作用下,当滑移体存在临空面、滑移体所受主动力与滑移面相交、且主动力合力与滑移面法线方向的夹角大于滑移面的摩擦角时出现底板滑移,且底板岩体结构失稳滑移的概率随着煤层倾角的增大、支架倾斜幅度和范围的增大、直接底破碎程度的增大而增大。

The floor failure and slip is one of the key technologies to be resolved in steeply dipping seam mining.Based on geological conditions and characteristics of strata behaviors of No.25221 working face in 2130 Coal Mine,the mechanism of floor failure and slip is investigated by theoretical analysis,numerical simulation and field monitoring.The results show that the floor developed from continuum state to block-fractured state under cyclic loading and unloading.The failure pattern of the floor presents an asymmetric inverse arch along inclined direction of working face,the maximum damage depth is located at the lower part of the working face,and the floor damage depth and range decrease with the increase of the dip angle of the coal seam.And the impact of the support load on the failure of the floor is limited,which mainly involved immediate floor.If the included angle between the resultant force of active force acting on the sliding body and the normal direction of slip surface is larger than the frictional angle of the slip surface,floor slip will be appear.And with the increases of coal seam dip,fragmentation degree of immediate floor and range and scope of inclination of support,the slip probability of floor increases.