超千米深部矿井采动应力显现规律

Mining-induced mechanics behavior in the deep mine with an over-kilometer depth

我国浅部煤炭资源逐渐耗竭,开采深度逐渐进入1000~2000m水平,常常伴有大量的工程灾害,其根本原因是深部采动应力场的显现规律与响应规律不清楚。以平煤股份十二矿超千米深己15-31030工作面为研究基地,开展了不同开采速率下超千米煤层采动应力显现规律及响应特征研究,并集成“锚杆应力-钻孔应力-钻孔裂隙窥视”等研究手段进行现场原位测试。结果表明:随着采煤工作面的不断推进,超前支承压力峰值先是交替上升,回采距离超过80m时,由于埋深较大导致支承压力峰值增长变缓并最终在85MPa左右波动,应力集中系数达3.3,高于一般浅部工作面集中系数;同时上覆岩层在采动影响下形成垮落带、断裂带、弯曲下沉带的“三带”结构;其次,随着开采速度增大,超前支承压力峰值逐渐增大,峰值点距采煤工作面的距离相应减小,基本顶断裂形成的岩块长度也越长;工作面支架压力随着采煤工作面持续推进呈现出周期上升的趋势。在采动影响下,由于扰动后应力重分布及能量释放,锚杆应力呈现出先增长后降低的趋势,得出工作面采动影响范围大约为85m,钻孔应力距采煤工作面75m左右时进入采动影响范围开始上升,而后进入支承压力降低区,应力开始出现小幅度下降;随着采煤工作面不断推进,强烈的开采扰动导致裂隙不断发育,裂隙逐渐发育成纵横交错的破碎带,并向顶板上方发展。

In China,the shallow mineral resources of the earth have been gradually exhausted.There are lots of engineering disasters in deep mining when mining at 1 000-2 000 m depths due to the unknown mechanism in deep mining-induced stress field.At the Ji 15 -31030 mining face with an over-kilometer depth in Pingdingshan Coal Mine No.12,the research was carried out to study the mining-induced stress evolution law with different mining speeds.The in-situ monitoring tests including bolt stress testing,borehole stress testing and fractures in borehole monitoring were also carried out to investigate the appearance law of mining-induced stress field.Results showed that the peak advanced abutment pressure increases alternately as the mining face advances and fluctuates around 85 MPa due to great depths when mining over 80 m.The stress concentration factor is 3.3,which is higher than that at shallow mining face.Overlying strata forms “three-zones” consisting of the caving zone,cracked zone and bent zone.Meanwhile,the peak advanced abutment pressure increases as the mining speed increases gradually,and the distance between peak pressure position and mining face decreases correspondingly,and the longer the length of the rock formed by the main roof breaking is.Hydraulic support pressure increases periodically with mining face advances.The bolt stress increases first and then decreases due to stress redistribution and energy releasing under the influence of mining,which concludes that mining influenced range is about 85 m.Borehole stress increases in the mining influence range about 75 m from the mining face,and decreases slightly when entering the advanced abutment pressure reduction zone.Strong mining disturbance results in fractures developing continuously as mining face advances,and fractures develop into crisscross broken zone as developed upwards.