洛河组砂岩含水层下大采高工作面导水断裂带演化规律

Evolution law of water-conducting fault zone in large mining height working face under sandstone aquifer of Luohe Formation

针对旬耀矿区厚煤层大采高工作面上覆洛河组砂岩含水层下的安全采煤问题,采用理论分析、相似材料试验和数值模拟研究了某矿1109大采高工作面覆岩破断及裂隙演化规律。研究表明:上覆岩层经历了直接顶破断、基本顶初次破断与周期破断、亚关键层初次破断与周期破断5个阶段,破断发生引起工作面煤壁上方裂隙密度和开度发生跃变,采空区覆岩裂隙经历孕育、产生、张开、闭合、压实5个动态阶段;从开切眼到充分采动过程中,在裂隙带的上部、工作面煤壁上方及开切眼上方裂隙较为发育,裂隙区近似"抛物线"状,采空区中部覆岩裂隙闭合而边界处裂隙不易闭合;工作面充分采动后,导水断裂带发育高度82~85 m,未导通上覆洛河组砂岩。

Aiming at the problem of safe coal mining under the sandstone aquifer covering Luohe Formation in the thick coal seam mining face of Xunyao Mining Area, theoretical analysis, similar material test and numerical simulation were used to study the overlying rock fracture and fracture evolution of large mining height in 1109 mining face. The results indicate that: under the condition of fully mechanized caving mining, overburden strata has experienced 5 changes, immediate roof broken, basic roof broken, basic roof periodic broken, key strata broken and key strata periodic broken. The density and width of fracture above working face will have a leap when the overburden rock is broken. In this process, the mining-induced fractures also have experienced 5 dynamic changes: preparation, production, stretch, close and compaction;many cracks will generate on fracture zone top, working face top and open-off cuts top in the course from open-off cuts to the full mining stage. The crack area which spreads around compacting area is parabolic shape. Namely, the cracks in central zone of overburden strata will close easily but the cracks in border zone will not;after the working face is fully excavated, the height of the water-conducting fissure zone is about 82 m to 85 m, and the sandstone overlying Luohe Formation is not connected.