综放工作面采动诱发逆断层张剪失稳特征及矿震活动规律分析

由于综放工作面开采空间大,对周边煤岩体扰动强烈,易引发断层构造活化,进而诱发大能量矿震导致冲击地压灾害,基于赵楼煤矿1303综放工作面生产和地质条件,理论分析了工作面回采对断层构造扰动影响的主控因素。采用相似模拟方法分析了断层构造错动滑移时空演化特征,并统计分析了工作面采动实际矿震震源活动演化规律。结果表明:逆断层下盘工作面回采,断层面发生张拉离层和剪切滑动的主控因素为表征开采扰动垂直作用力Pv和水平作用力Ph的比值k、表征断层几何特性的断层倾角θ、以及表征断层力学特性的内摩擦角φ;工作面开采首先引发覆岩低层位断层岩块滑动,并随工作面与断层面距离的减小逐渐向高层位断层岩块扩展;断层诱发矿震需满足断层产生滑动失稳且滑动表现为黏滑两个条件。工作面矿震活动规律:采空区范围越大,矿震活动越剧烈;矿震震源丛集于采空区区域,且随工作面推进向前方及高层位岩层转移。对1303工作面矿震事件影响程度:Fd96断层张剪失稳采空区覆岩破断运动FZ14断层张剪失稳。

Characteristics of seismic activity and tensile slip features of fault under stress and displacement disturbance in full mechanized workface

Full mechanized mining method leads to large size gobs and serious stress and displacement disturbance on surrounding rock mass,which would cause a fault tensile slip motion that induces high energy seismic tremors and further cause rockburst around the mining face.To solve this problem,based on the mining and geological background of 1303 full mechanized workface in Zhaolou Mine,the tectonic and mining induced stress as well as their main controlling elements were analyzed.The relationship between tensile slip displacement along fault face and mining procedure was studied with analogue model,and the characteristics of seismic tremors were analyzed statistically.The results show that in the circumstance of mining the footwall coal seam of reverse fault,the tensile slip motion of fault is determined by several key parameters,such as the ratio (k) of vertical force (Pv) and horizontal force (Ph) caused by mining activity,the dip angle of fault (θ) which represents the geometric features and the friction angle of fault (φ) which represents the mechanical features of fault.Additionally,the mechanical circumstance of the fault face should satisfy the stick slip requirements as to cause seismicity.The stress and displacement disturbance induced by mining appear first in low overlaying strata of coal seam and then develop to high strata as the excavation processing,these would further cause the tensile slip motion of fault.Seismic tremors mainly concentrate around the mining gob.With the increase of gob size,the daily frequency and energy of tremors around the mining face rise steadily,and the location of tremor focus propagates to upper strata.The tensile slip motion of Fd96 fault is the main cause for the tremors occurred in 1303 mining face,followed by the fracture and movement of overlay strata,and the tensile slip motion of FZ14 fault has least influence on tremor activity.