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厚黄土层极近距离采空区下相邻工作面相向开采时序研究

Study on time sequence for opposite mining of adjacent working faces under ultra-close coal seam goafs with thick loess layer

  • 摘要: 针对厚黄土层极近距离采空区下2个相邻工作面相向开采应力叠加效应显著, 工作面间煤柱易失稳诱发强矿压灾害问题, 以陕北侏罗纪煤田海湾煤矿三号井2206工作面和王才伙盘矿2201工作面相向开采为工程背景, 采用数值模拟方法分析了2个工作面相向开采前后上部覆岩应力环境及煤柱稳定性, 揭示了不同开采时序下2个工作面的围岩应力叠加效应及巷道围岩变形破坏规律。研究结果表明: 2−2上煤层开采后, 房柱区顶板和煤柱较为稳定, 长壁式采空区覆岩破坏使采空区内的应力降低, 工作面间遗留煤柱垂直应力呈非对称分布, 长壁式采空区侧垂直应力峰值高于房柱区侧; 2−2煤层相邻工作面相向开采过程中, 上部遗留煤柱集中应力和工作面采动应力的叠加效应影响工作面间煤柱和巷道围岩的稳定性, 当2个工作面相向开采距离小于30 m时, 仅2206工作面开采时煤柱最大垂直应力分别比仅2201工作面开采和2个工作面同时开采减小4.7%和10.0%; 仅2206工作面开采时2206回风巷围岩变形量最小, 2个工作面同时开采时巷道围岩变形量最大, 2个工作面交错−20 m后煤柱应力及巷道围岩变形量基本趋于稳定。最后, 结合现场开采实际情况, 确定了相邻工作面相向开采时序, 并通过物理模拟验证了其合理性。研究成果在现场进行了应用, 效果良好, 从而避免了工作面的搬家倒面和停产, 取得了显著的经济效益, 可为类似条件的工作面安全开采提供借鉴。

     

    Abstract: In opposite-direction underground mining of two adjacent working faces under the ultra-close goafs with the thick loess layer, significant stress superposition occurs and the coal pillar stability between the working faces is in question, which may trigger strong ground pressure disasters. Taking the opposite-direction mining of the 2206 working face in the Haiwan No. 3 Well and the 2201 working face in the Wangcaihuopan Mine of the Northern Shaanxi Jurassic Coalfield as the engineering background, the overburden stress environment and the stability of the coal pillar between the two working faces before and after the opposite-direction mining were investigated using the numerical simulation, and the stress superposition effect of the surrounding rocks of the two working faces under different mining time sequences and the deformation laws of the surrounding rocks of the roadway were analyzed. The results show that the roof of the room-and-pillar area and the coal pillars are relatively stable after the mining of the 2-2 upper coal seam. The overburden failure of the longwall goaf reduces the stress in the goaf. The vertical stress of the remaining coal pillars between the working faces is asymmetrically distributed, and the peak of vertical stress on the side of the longwall goaf is higher than that on the side of the room-and-pillar area. During the opposite-direction mining of adjacent working faces of the 2-2 coal seam, the superposition effect of the concentrated stress of the remaining upper coal pillars and the mining-induced stress of the working faces affects the stability of the coal pillars and the surrounding rocks of roadway between the working faces. When the opposite-direction mining distance between the two working faces is less than 30 m, the maximum vertical stress of the coal pillar during the mining of the 2206 working face alone is 4.7% and 10.0% lower than that during the mining of the 2201 working face alone and the simultaneous mining of the two working faces, respectively. When only the 2206 working face is mined, the deformation of the surrounding rocks of the 2206 ventilation roadway is the smallest, while the two working faces are mined simultaneously, the deformation of the surrounding rocks of the ventilation roadway is the largest. After the two working faces stagger by −20 m, the stress of coal pillars and the deformation of surrounding rocks of the roadway almost tend to be stable. Considering the actual situation of on-site mining, a reasonable and safe mining time sequence for adjacent working faces was determined, and its rationality was verified through physical simulation. The findings are implemented on site with good performance by avoiding the relocation and shutdown of the working faces and achieving remarkable economic benefits. The research provides a reference for the safe mining of working faces under similar geological and mining conditions.

     

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