浅埋近距离煤层开采超前煤柱群冲击失稳机制
Shocking failure mechanism of advanced coal pillars under the mining influence of shallow⁃buried closed distance coal seams
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摘要: 工作面前方遗留煤柱群( 后文简称“ 超前煤柱群” ) 在采动影响下会发生链式冲击失稳,诱 发动载矿压灾害并影响下伏煤层的安全高效开采。 揭示超前煤柱群链式冲击失稳机制是浅埋近距 离煤层安全开采的根本前提。 本文实测分析了元宝湾煤矿房式采空区下伏 6107 工作面开采的覆 岩移动规律,发现了超前煤柱群的回弹变形现象,开展了房式采空区下伏煤层开采的物理模拟实 验,研究了房采煤柱群-覆岩的变形破坏特征,分析了采动影响下超前煤柱群回弹冲击失稳的动态 过程,揭示了浅埋近距离煤层开采超前煤柱群的冲击失稳机制。 结果表明:1 浅埋柱采区近距离 下伏煤层开采过程中工作面前方覆岩呈现出“ 先短暂回弹后剧烈下沉” 的运动特征,即首先存在极 短时间的覆岩回弹变形现象,之后出现了部分覆岩的整体破断与垮塌。 由此,反推出采动影响下超 前煤柱群也发生了回弹变形。 2 柱式采空区下伏煤层开采过程中关键柱在覆岩沉降和超前支承 压力的作用下最早出现斜切破坏,引起载荷的转移,加剧邻近部分房采煤柱群的应力集中程度,进 而发生链式斜切破坏。 在此过程中,覆岩持续沉降,裂隙也不断发育,形成剪切贯通断裂面,发生破 断回转,促使超前煤柱群回弹变形与冲击失稳,引发层间岩层的全厚切落,带动更大规模房采煤柱 群的链式失稳,并造成下伏工作面动压灾害的发生。 3 浅埋近距离下伏煤层开采“煤柱群-覆岩” 的失稳垮塌过程可以细分为:关键柱斜切破坏阶段、关键柱邻近部分煤柱群破坏阶段、超前煤柱群 回弹冲击失稳阶段、覆岩垮塌与层间岩层切落致灾阶段。 4 浅埋近距离煤层开采超前煤柱群冲击 失稳是“煤柱群回弹变形”与“覆岩联动垮塌”共同作用且互馈影响的动态过程。 该研究可以解释 柱式采空区下伏近距离煤层开采超前动载矿压的显现原因,有望为超前动载矿压的预测和控制提 供理论指导,并进一步保障近距离煤层群的安全绿色高回收率开采。Abstract: Chain shocking instability of residual coal pillars in front of the working face will induce the dynamic load disasters under the mining influence and affect the safe and efficient mining of the underlying coal seam. It is the basic premise of safe mining to reveal the advance chain⁃shock failure mechanism of coal pillars under the mining in⁃ fluences of shallow⁃buried closed distance coal seams. In this paper, the movement law of overburden strata during the mining of the 6107 working face in the Yuanbaowan Coal Mine was monitored and analyzed. The spring⁃ back deformation phenomenon of advanced coal pillars was found. The physical simulation experiment of underly⁃ ing coal seam mining under the room and pillar goaf was carried out. The deformation and failure characteristics of re⁃ sidual coal pillars and overburden strata were studied. The springback shocking failure process of advanced coal pillars under the mining influence was analyzed. The shocking failure mechanism was revealed. The results show that 1 Dur⁃ ing the mining process of shallow⁃buried closed distance underlying coal seam,the overburden strata in front of the working face present a deformation characteristics of former short⁃time springback and then severe subsidence. That is,the overburden strata firstly present a very short⁃term springback deformation phenomenon. Afterwards,there is an overall collapse phenomenon of overburden strata. As a result,the springback deformation fact of advanced coal pillars under the mining influence could also be obtained. 2 The key pillars are suffered the earliest oblique shear failure un⁃ der the strata subsidence and advanced bearing pressure,which causes the load transfer and redistribution. It would strengthen the stress concentration of adjacent coal pillars,and lead the chain and oblique shear failure. During this process,the overburden strata continue to subside. The fractures continue to develop and the shear breaking surface is generated. The collapsing and rotating of overburden strata also occur. It promotes the springback deformation and advance shocking of residual coal pillars in front of the working face,and causes the full⁃thickness cutting of interbur⁃ den strata. Finally,larger range of coal pillars suffer the chain failure and the dynamic disasters are caused in the un⁃ derlying working face. 3 The springback shocking failure process of advanced coal pillars under the mining influence of shallow⁃buried closed distance coal seam could be divided into four periods: the oblique shear failure period of key coal pillar,the failure period of key pillar and adjacent partial coal pillars,the springback shocking failure peri⁃ od of advanced coal pillars,and the disaster period caused by overburden strata collapsing and interburden strata cut⁃ ting. 4 The advance shock failure of residual coal pillars under the mining influence of shallow⁃buried closed dis⁃ tance coal seam is a dynamic process with the combined and mutual feedback effect of “springback deformation of coal pillars” and “linked collapse of overburden strata”. This study can explain the reason why the advanced dynamic load is generated in the underlying coal seam mining under the pillar goaf. It is expected to provide a theoretical guidance for the prediction and control of the advanced dynamic load pressure,which can further ensure the safety,green and high recovery⁃rate mining of close⁃distance coal seams.