一侧采空高位硬厚关键层破断规律与微震能量分布

Fracture laws of one-side mined high-position hard thick key strata and microseismic energy distribution

针对工作面一侧采空边界条件,建立三边固支一边简支高位硬厚岩层板结构力学模型,推导出硬厚岩层破断能量释放公式;通过比较岩板上表面固支边和下表面中部最大拉应力,揭示了硬厚岩层的变形破断规律;并结合现场微震监测数据,分析了高位硬厚岩层下开采微震活动分布特征。研究结果表明:当悬露系数λ<1.024时,硬厚岩层倾向固支侧与下表面中部同时断裂,呈固支侧侧向跨度大于简支侧的竖向偏"O-X"型;否则,硬厚岩层走向固支边首先破断,呈对称的横向正"O-X"型;工作面开采时,小能量微震主要分布在厚关键层下方岩体内,且下方岩体运动易引发相邻采空区的微震活动;大能量微震活动发生在厚关键层破断失稳过程中,主要分布在厚关键层断裂线附近,集中于其内部及下方附近。

Aiming at the boundary conditions of one side mined working face, a plate model with three clamper edges and one simply supported edge was established as the mechanical model of high-position hard thick strata, and an energy releasing formula of hard thick strata fracturing was proposed. Deformation and rupture law of hard thick strata was revealed by comparing the maximum tension stresses in clamped edges of rock plate＇s upper surface and the middle of lower surface. In addition, characteristics of microseismic energy distribution during the mining operation under high-position hard thick strata were analyzed combined with the microseismic monitoring data in field. Research results show that fracture happens at the same time in both lateral clamper side and the central of the lower surface when λ1.024, the fracture form is an offset transverse ＂O-X＂ type, while the lateral span of the clamper side is lager than that of the simply support side. Otherwise, fracture first happens along the strike clamper edge, and the fracture form is a symmetrical vertical ＂O-X＂ type. During the mining process, small energy seismic events are mainly distributed in the rock mass below the thick key strata, and seismic events are easily triggered in the neighboring gob by the movement of lower rock mass. The high energy seismic events mainly happen in the fracturing process and losing stability of high-position thick key strata, mainly distribute near the fracture line of thick key strata, and concentrate in the vicinity of the internal and lower parts.