厚硬岩层下孤岛工作面开采“T”型覆岩结构与动压演化特征

Characteristics of T-type overburden structure and tremor activity in isolated face mining under thick-hard strata

为研究厚硬岩层下孤岛工作面开采对强矿震或冲击矿压的影响,理论分析鲍店矿103上05孤岛工作面厚硬覆岩空间结构及其破断运动对矿震活动的影响,并对孤岛面开采的冲击矿压危险性进行了动态评价。研究表明:103上05工作面在竖向剖面上为一非对称"T"型孤岛覆岩结构,其长臂侧易出现关键层大尺度破断运动,诱发强矿震与冲击矿压的危险性较高;在水平层面上亚关键层破断形成"O"型断裂结构,巨厚主关键层则以大尺度"OX"模式分层破断。各级关键层的逐级破断与运动是矿震活动的主要动力源。根据微震实测,矿震活动多集中在"T"型结构长臂侧,尤其是能量大于105J的强矿震主要出现在103上06采空区与103上05工作面巨厚主关键层中,并表现出很高的S,P波能量比。通过波速梯度异常区的动态反演,对"T"型孤岛面覆岩运动的动压危险性进行评价,效果良好。同时,分别进行煤层静载预卸压与低位顶板走向步距式超前预裂,降低了强矿震活动对煤体的冲击扰动效应。

To study the influence of isolated coal face mining on rock burst or strong tremor, the structure characteristics of thick-hard strata above 10305 isolated face were analyzed in this paper, and the seismic activity and burst risk were also monitored and analyzed. The results show that the strata structure above 10305 isolated face is an unsymmetrical isolated ＂T＂ structure, with the main key strata fractured on the short-arm side and non-fractured on the long-arm side, that is, the long-arm main key strata will fractrure and move in large-scale after face mining, and the risk of strong tremor or rock burst is relatively high. In addition, the inferior key strata can only form ＂O＂ fracturing structures, and the super-thick main key strata will form layered ＂O-X＂ structures, while the fracturing and movement of main and inferior key strata are the main sources of seismic activities. According to seismic monitoring, seismic events manily located on the long-arm side of ＂T＂ structure, especially the strong tremors occurred almost within the super-thick main key strata above 10305 and 10306. Moreover, the stong tremors present high ratios of S-wave to P-wave energy,which means they are mainly the results of shear fracturing or slip movement of main and inferior key strata. The burst risks caused by unsymmetrical ＂T＂ structure were evaluated by volocity gradient inversion, and the evaluation results are satisfactory. The big-diameter pressure-relief boreholes in coal seam and pre-blastings in main roof were implemented respectively in advance, and the burst effects of strong tremors were greatly reduced.