基本顶板结构初次破断与全区域反弹时空关系

Space-time relationship between the first fracture of main roof structure and whole regional rebound

为了研究基本顶初次破断与全区域反弹压缩场的时空关系,建立弹性基础边界基本顶板结构初次破断扰动力学模型,基于有限差分理论与主弯矩破断准则计算研究了基本顶板结构初次破断时全区域反弹压缩场的基本形态特征以及基本顶破断长度、破断发展过程及破断程度对全区域反弹压缩场的影响。结果如下:①基本顶深入煤体断裂时,在破断线外侧依次产生“半椭圆形反弹I区”、“椭环形压缩区”、“椭环形反弹II区”及“椭环形压缩区”;②断裂线前侧反弹I区中部位置的反弹量最大,断裂线的两端部为压缩区;③首次断长与二次断长均较小时,破断线外围依次为“M形反弹I区”、“椭环形压缩区”及“椭环形反弹II区”;首次断长与二次断长均较大时,断裂线外围依次为“M形反弹I区”、“环8字形压缩区”及“环8字形反弹II区”;④基本顶破断程度越大,反弹量越大,而反弹压缩的分区特征与破断程度无关;⑤反弹II区包围了“悬顶区”且贯穿两巷及邻侧巷道区,反弹II区的内、外边界线的垂距基本相等,所以基本顶深入煤体破断时可在邻侧巷道及两巷区监测到反弹压缩信息。采用特制高精度位移传感器实验与工程实践验证了结论的合理性。形成预警基本顶大面积初次破断的“一同时与两滞后”原理及“两区域与两指标”监测位置及方法。

In order to study the space-time relationship between the first fracture of main roof structure and the whole regional rebound compression field,a mechanics model for the first fracture disturbance of main roof plate structure with elastic foundation boundary was established.Based on the finite difference theory and the fracture criterion of primary moment,the basic morphology characteristics of the whole regional rebound compression field formed in the first fracture of main roof structure were studied.Furthermore,the effects of fracture length,fracture development process and fracture degree of main roof on the whole regional rebound compression field were also studied.The following conclusions were obtained after those studies:① When the fracture of main roof arises ahead of the surface of coal body,“semi-ellipse rebound zone I”,“elliptical ring compression zone”,“elliptical ring rebound zone II” and “elliptical ring compression zone” are successively generated at the periphery of the fracture line.② The rebound volume in the middle part of rebound zone I in front of the fracture line is the largest,and the compression zone is at both ends of the fracture line.③ When the first fracture length and the second fracture length are smaller,“M-type rebound zone I”,“elliptical ring compression zone” and “elliptical ring rebound zone II” are successively generated at the periphery of the fracture line.However,when the first fracture length and the second fracture length are larger,“M-type rebound zone I”,“ring 8-shape compression zone” and “ring 8-shape rebound zone II” are successively generated at the periphery of the fracture line.④ The bigger the fracture degree of main roof is,the greater the rebound volume will be,but the partition features of rebound compression zone are independent of the fracture degree.⑤ The rebound zone II has encircled the entire “hanging roof area” with running through the two roadway areas and adjacent roadway area.Moreover,the vertical distance from the inner boundary line to the outer boundary line in rebound zone II is basically equal.Consequently,the rebound compression information can be detected in the two roadway areas and adjacent roadway area when the fracture of main roof arises ahead of the surface of coal body.The rationality of the conclusions has been verified by engineering practice and the experiment adopting the custom-built high-accuracy displacement sensor.The principle of “one synchronization and two delays” and the monitoring position and method of “two zones and two indexes” for the early warning of first fracture of main roof with large area are formed.