采场底板破坏特征及稳定性理论分析与试验研究

Theoretical analysis and experimental investigation on failure characteristics and stability of stope floors

为了研究承压水体上煤层开采后底板岩体的破断特征和突水危险性,基于弹性力学理论,分别构建周期来压时采场底板力学计算模型和隔水关键层稳定性分析模型,理论计算采后底板纵向破坏形态和横向突水危险区域;采用有限差分流–固耦合模拟方法验证承压水上开采底板损伤范围及渗流趋势;开展底板突水相似模拟试验揭示底板岩体破裂和渗流变化特征。研究表明:(1)理论计算采后底板沿着工作面走向和倾向分别呈"勺形"和"倒马鞍形"破坏形态,在采空区与煤体交界附近底板的破坏深度最大,与模拟得到的底板破坏范围大致相当。(2)底板隔水层的理论突水部位分别位于靠近工作面煤壁侧的区域A、煤壁后方采空区50m处的区域(B)及采空区倾向两边界区域(C),(D),但在靠近煤壁侧的区域(A)的中心位置的突水风险最高,这与试验观察到的"孔隙水主要经工作面煤壁斜下方底板渗透入采空区底部裂隙岩体"及模拟的"承压水沿采空区边界两侧的底板岩体涌入"等现象均较为吻合。(3)试验观察到在工作面和开切眼附近的浅部底板中剪切、竖向裂隙较发育,而采空区下方岩体出现层向裂隙,且最大损伤深度为12.8 m,略小于理论计算和数值模拟结果13和15.875 m。研究结果揭示了采场底板易发突水部位及突水风险,可为矿井底板突水治理提供一定的理论依据和参考价值。

In order to investigate the fracture characteristics and water outburst risk of mining floors above confined aquifer,mechanical models of both stope floors and water-resisting key strata were constructed to theoretically calculate the longitudinal failure range and transverse water-inrush zone of the floor under periodic weighting,and the fracture characteristics and seepage trend of the mining floor above confined aquifer were revealed using finite difference hydro-mechanical coupling modeling method and similar simulation test.The theoretical calculation shows that after coal seam excavation,the failures of the floor along the strike and inclination of the working face present"spoon-shaped"and"inverted saddle-shaped"respectively,and that the maximum failure depth of the floor is located near the boundary between the mined-out area and the coal body,which is roughly similar to the simulating result.The water gushing positions of water-resisting key strata are theoretically located in the areas including the side of the working face,50 m behind the coal wall and both sides of the goaf.However,the risk of water inrush in the central part of the side area of the working face is the highest,which coincides with the experimental observations and the numerical phenomena.It is observed that the shear and vertical cracks well develop in the shallow floor near the mining face and starting cut while that the layered cracks appear in the rock mass below the goaf.The maximum damage depth obtained by the test is 12.8 m,slightly less than the theoretical calculation and numerical simulation results of 13 and 15.875 m.The research results of this paper reveal the water inrush location and risk of mining floor,which can provide a theoretical basis for mine water treatment.