水力压裂对末采矿压显现规律的影响研究

Influence of hydraulic fracturing on the behavior of mine pressure at the end of mining

为研究水力压裂对工作面末采矿压显现规律的影响,以隆德煤矿213综采工作面为背景,采用FLAC3D建立其末采数值模型,考虑水力压裂前后岩体的力学变化特征,对比分析了有无水力压裂对末采悬顶长度以及矿压的影响,在此基础上设计了213综采工作面水力压裂方案,实测了工作面矿压以及回撤巷道变形。数值计算结果表明,无水力压裂条件下,213综采工作面顶板岩体在末采贯通阶段周期来压步距约为10~15 m,采空区上方岩体悬顶长度约为13 m;而水力压裂条件下周期来压步距则减小为5~10 m,悬顶长度减少为5 m。现场开展末采水力压裂施工后,工作面剩余可采长度为4~6 m发生周期来压,卸压区平均支架工作阻力减小9.7%;回撤巷道顶底板移近速度在工作面剩余可采长度低于26 m时由缓慢变形阶段的2.5~5.7 mm/d增加至快速变形阶段的13.0~66.9 mm/d。水力压裂在末采阶段的实施,有效控制了工作面的悬顶长度,成功实现了工作面的安全开采,切实保证了末采撤架工作的顺利完成。

In order to study the influence of hydraulic fracturing on the pressure behavior law of the end mining of the working face,the numerical model of the end mining was established by using FLAC3D in the background of 213 fully mechanized mining face in Longde Coal Mine,and the influence of hydraulic fracturing on the length of hanging roof and rock pressure at the end of mining was compared and analyzed considering the mechanical change characteristics of rock mass before and after hydraulic fracturing.On this basis,the hydraulic fracturing scheme of 213 fully mechanized coal mining face was designed,and the mine pressure of the working face and the deformation of the withdrawal roadway were measured.The numerical calculation results show that the periodic weighting step of 213 fully mechanized coal mining face roof rock mass is about 10~15 m at the end of mining through stage,and the hanging roof length of rock mass above the goaf is about 13 m without hydraulic fracturing.The periodic weighting step is reduced to 5~10 m when hydraulic fracturing occurs,and the hanging roof length is decreased to 5 m.After the hydraulic fracturing at the end of the mining period is carried out in the field,periodic weighting occurs when the remaining minable length of the working face is 4~6 m,and the average working resistance of the support in the pressure relief area is reduced by 9.7%.When the remaining minable length of the working face is less than 26 m,the convergence velocity of the roof and floor of the withdrawal roadway increases from 2.5~5.7 mm/d in the slow deformation stage to 13.0~66.9 mm/d in the rapid deformation stage.The implementation of hydraulic fracturing in the last mining stage effectively controls the length of the hanging roof of the working face,realizes safe working face mining,and efficiently ensures the completion of the final mining support removal operation.