厚煤层一次采全高低位厚硬岩层垮落致冲机理与防治

Mechanism and prevention of rock burst caused by the collapse of low-level thick hard rock strata at full-height mining face in thick coal seam

基于某矿31103工作面煤层及顶板的基本参数,结合该工作面已发生冲击事件,发现低位厚硬岩层垮落是该矿发生冲击地压的主要原因。为此,以防治低位厚硬岩层垮落诱发冲击地压为目的,选取该矿31103回采工作面顶板垮落控制为工程背景,采用现场调研、理论分析等方法,研究了厚煤层一次采全高低位顶板支托层与随动层的运动规律,建立了采空区侧向支承压力力学计算模型,揭示了低位厚硬岩层垮落诱冲机理。所获主要结论:(1)确定了工作面低位顶板岩层的基本参数,并计算得出了工作面低位岩层中较厚的协同垮落岩层。在工作面开采过程中,随动层随支托层运动发生同步变形,当工作面顶板发生大面积悬顶垮落时容易造成大能量动力现象;(2)建立了采空区侧向支承压力力学计算模型,得到了采空区侧向支承压力峰值位置距采空区边缘约为45 m,影响范围约为90 m,支承压力峰值约为55 MPa, 31103工作面回风巷处于采空区侧向高支承压力影响范围。在工作面开采过程中,回风巷围岩应力已达到发生冲击地压的应力水平;(3)揭示了低位厚硬岩层垮落致冲机理:采空区侧向支承压力形成的高应力静载是主要冲击力源,回采工作面厚硬支托层与其随动层同时垮落造成的扰动动载是主要诱发力源,两者叠加作用导致冲击地压事故;(4)提出了针对性的防治措施:在本工作面同时采用水力压裂技术与爆破切顶技术;在下一临侧工作面则采取小煤柱护巷布置方式,并在采空区侧进行爆破断顶;基于上述卸压措施,在工作面继续推采过程中微震事件总体呈现为频次降低、单次能量减小、总能量减小的特征。

Based on the basic parameters of coal seam and roof in No. 31103 working face of a mine, combined with the rockburst events occurred in the working face, it is found that the collapse of low-level thick-hard rock strata is the main reason of rockburst occurred in the mine. Therefore, in order to prevent and control the rockburst induced by the collapse of low-level thick-hard rock strata, the roof collapse control of No. 31103 working face in the mine was selected as the engineering background. The motion law of the full-height roof support layer and follow-up layer in the thick coal seam mining was studied by field investigation and theoretical analysis. The mechanical calculation model of the side abutment pressure in the goaf was established, and the mechanism of the rockburst induced by the collapse of low-level thick-hard strata was revealed. The main results are as follows:(1) The basic parameters of the low-level roof strata of the working face are determined, and the thick cooperative caving strata in the low-level strata of the working face are calculated. In the mining process of working face, the follow-up layer deforms synchronously with the movement of the support layer, and leads to large energy dynamic phenomenon when the roof of working face falls in large area.(2) The mechanical calculation model of side abutment pressure in goaf is established, and the peak position of side abutment pressure in goaf is about 45 m from the edge of goaf, the influence range is about 90 m, and the peak value of side abutment pressure is about 55 MPa. The return roadway of No. 31103 working face is in the influence range of high side abutment pressure in goaf. In the mining process of working face, the stress of surrounding rock in return roadway has reached the stress level of rockburst.(3) The mechanism of rockburst in low thick-hard rock strata is revealed. The high static load formed by the side abutment pressure in the mining area is the main force source of rockburst, and the disturbance dynamic load caused by the simultaneous collapse of thick-hard support layer and its follow-up layer is the main inducing force source, and the both superimposed influence causes the rockburst.(4) Targeted prevention and control measures are proposed. Hydraulic fracturing technology and blasting roof-cutting technology are used simultaneously in the working face. In the next neibourghing working face, the layout of small coal pillar roadway protection is adopted, and blasting roof-cutting is conducted on the goaf side. Based on the above relief-pressure measures, the micro-seismic events in the continuous mining process of the working face are characterized by frequency reduction, single energy reduction and total energy reduction.