逆断层下盘工作面回采扰动引发断层活化特征的试验研究

Experimental study of the activities of reverse fault induced by footwall coal mining

为分析逆断层下盘工作面回采对断层面错动失稳影响,在双轴等压加载条件下,试验获得了逆断层下盘煤层回采扰动下断层活化失稳特征。结果表明:回采工作面围岩由内向外形成采动卸压区、支承升压区、原始应力区的动态演化将诱发断层构造错动活化,且逆断层构造更易受回采工作面扰动区影响;双向等压条件下逆断层下盘煤层开挖,垂直方向扰动与水平方向扰动载荷比由1逐渐增加至6,断层面发生离层或剪滑失稳的危险升高;断层构造面附近应变呈不均匀分布,且煤层处应变明显高于顶、底板岩层;煤层开挖引发的声发射事件84%能量分布在10-13~10-10 J,主要分布于煤层顶板岩层,且跨越断层面声发射事件较少,表明断层构造对应力扰动有阻断作用;开挖煤层与断层面交叉处是声发射事件集聚区域,发生错动失稳危险性较高。对比赵楼煤矿1303工作面实际矿震数据,矿震震源与试验声发射源空间分布特征具有一定相似性,佐证了类逆断层组合结构岩石试验方法的可行性。

The reverse fault will slip with workface excavation in footwall. As the stresses loading on the combined sam ple were equal in the X and Y direction,the stress and strain along the fault,as well as acoustic emission signals,were monitored during the coal excavation. The analytical results show that stress decrease zone,stress increase zone and in situ stress zone occurred around the gob and their evolution will cause fault slip. Compared with normal fault,reverse fault has higher slipping risk under the same mining condition. As the workface locating in the footwall of reverse fault advances forward,the ratio of vertical force and horizontal force caused by mining increases from 1 to 6,which means the slipping risk of reverse fault rise. The strain along the fault face is not even,and the strain of coal seam is higher than that of rock strata. The energy of 84% of the acoustic events caused by coal mining are between 10-13 J and10-10 J and their focus mainly concentrate in the roof strata and unlikely transpass the fault face which means the fault can cut off the stress disturbance of mining. The conjunction of coal seam and fault face tends to cause large acoustic events which means this area has high slip risk. Compared with the in situ seismicity in Zhaolou Coal Mine,the spatial location of seismic focus and experimental acoustic focus have similar features to some extent,which could prove the feasibility of the experimental method adopted in this paper.