特厚煤层变面采场覆岩破断释能规律与防冲技术研究

    Research on energy release laws and rock burst prevention and control technology in extra-thick coal seam variable face stopes

    • 摘要: 针对变面采场开采中围岩稳定性控制难度大、冲击危险性高等问题,以新疆宽沟煤矿I010206工作面为工程背景,建立工作面顶板FLAC3D数值模型与周期断裂力学模型,分析变面采场围岩应力与能量演化特征,揭示工作面覆岩破断诱冲机制,提出了水力压裂顶板超前弱化解危技术并对卸压效果进行对比检验。结果表明:在采场开采期间,随着工作面宽度增加,超前支承压力峰值和应力集中程度大幅增高,超前支承压力峰值由13.05 MPa增加至16.67 MPa,应变能密度峰值由46.77 kJ/m3增加至96.72 kJ/m3;工作面回采期间,由于坚硬顶板的存在,易形成大面积悬顶,顶板内集聚的弹性应变能明显上升,当坚硬顶板达到其极限跨距时发生破断,释放的大量能量易引起矿山压力显现;工作面变宽后顶板载荷增加,上覆岩层载荷向工作面前方煤体和工作面两端煤体进行传递,B4−1煤层I010408工作面开采后支承压力与B2煤层I010206工作面开采后超前支承压力叠加后应力集聚程度较高,采空区侧向支承压力与形成的高静载和顶板大面积垮落的高动载更易诱发冲击地压。针对顶板能量集聚程度较高、坚硬顶板发生垮落时动载扰动较强等现场冲击危险因素,提出了水力压裂顶板超前弱化措施。通过支架压力与微震数据对水力压裂与预裂爆破卸压效果进行对比检验发现,使用水力压裂技术后,工作面顶板来压步距降低,微震信号呈现出低能高频特征,工作面冲击危险性明显下降,保障了工作面安全回采。

       

      Abstract: Aiming at the problems of difficulty in controlling the stability of surrounding rock and high impact risk in the mining of variable face stope, taking I010206 working face of Kuangou Coal Mine in Xinjiang as the engineering background, FLAC3D numerical model and periodic fracture mechanical model of working face roof are established, and the stress and energy evolution characteristics of surrounding rock in variable face stope are analyzed, and the mechanism of induced impact caused by overburden failure in working face is revealed, and the technology of hydraulic fracturing roof to relieve danger in advance is put forward, and the pressure relief effect is compared and tested. The research results show that: during the mining period, with the increase of the width of the working face, the peak value of the advanced abutment pressure and the degree of stress concentration increased significantly, the peak value of the advanced abutment pressure increased from 13.05 MPa to 16.67 MPa, and the peak value of strain energy density increased from 46.77 kJ/m3 to 96.72 kJ/m3, during the mining process of the working face, due to the presenece of hard roof, large areas of unsupported roof are prone to form, the elastic strain energy accumulated with the roof significantly increases. When the hard roof reaches its limit span, it breaks and releases a lot of energy, which is easy to cause the mine pressure to appear; after the working face is widened, the roof load increases, and the overburden load is transferred to the coal body in front of the working face and the coal bodies inclined to the upper and lower sides of the working face. The stress concentration is higher after the abutment pressure of I010408 working face in B4-1 coal seam is superimposed with the abutment pressure of I010206 working face in B2 coal seam after mining, and the lateral abutment pressure of goaf and the high static load and the high dynamic load of roof caving in a large area are more likely to induce rock burst. In view of the site impact risk factors such as high energy concentration of the roof and strong dynamic load disturbance when the hard roof collapses, the advanced weakening measures of hydraulic fracturing roof are put forward. Through the pressure relief effects of hydraulic fracturing and pre-splitting blasting compared and tested by support pressure and micro seismic data, it is found that after using hydraulic fracturing technology, the weighting step of roof in working face is reduced, micro seismic signals show the characteristics of low energy and high frequency, and the impact risk of working face is obviously reduced, which ensures the safe mining of working face.

       

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