采空区下近距离煤层开采时,下层煤回采巷道将受到上煤层采空区遗留煤柱、本煤层相邻 工作面动压的影响,针对孙家沟煤矿特厚煤层放顶煤工作面 13311 回风巷严重的冒顶、两帮内挤和 底臌等变形破坏现象,采用现场实测、理论分析及数值模拟等研究方法,探讨了回采巷道失稳机理 及主要影响因素。 研究表明,13311 回风巷变形失稳主要影响因素为迎邻近工作面回采动压响掘 进、巷道布置方式和巷道支护参数不合理。 与上层煤回采巷道垂直布置、巷道支护强度低且迎采动 掘进时,下层煤回采巷道容易失稳。 为改善 13313 回风巷围岩稳定性,有效控制巷道变形,根据试 验巷道围岩物理力学性质及受力特征,研究提出了有针对性的解决方案:首先改进巷道布置方式, 将下煤层回采巷道布置在采空区下,且应距离上煤层采空区遗留煤柱不小于 20 m;其次增大护巷 煤柱宽度,把区段护巷煤柱宽度增加到 20 m 以上,减少迎采动掘进动压的影响;最后,采用高预应 力全锚索加强支护,提高锚杆锚固段的整体性及其承载能力。 据此,在 13313 回风巷进行了工业性 试验并进行了巷道矿压观测,结果表明:经受相邻 13311 工作面回采动压影响后,区段煤柱整体完 整,具有良好的承载性能;锚索受力达到了250~300 kN,约为其破断力的 50% ,锚索受力增长平 稳,较好地控制了巷道离层和围岩变形;13313 回风巷顶底板移近量为 400 mm 左右,两帮移近量为 300 mm 左右,巷道围岩变形量得到了有效控制,保证了巷道的整体稳定性,取得了良好的支护效 果。 但是,采用该种巷道布置方式,下层 13 号煤层 13313 工作面回采时,因工作面上方 11 号煤层 区段煤柱集中应力的影响,对其顶板和煤壁管理提出了更高的要求,需引起高度重视。

During the mining process of the close distance coal seams under goaf,mining roadway in the lower seam is affected by the coal pillars left over in the goaf of the upper seam and the adjacent working face’s dynamic pressure.In view of the serious deformation and failure phenomenon of roof fall,the inward extrusion of two roadsides and floor heave in 13311 air return roadway of top coal caving face of the extra-thick coal seam of Sunjiagou coal mine,the field measurement,theoretical analysis and numerical simulation are adopted to study the mechanism of roadway’s instabili-ty and the main influencing factors. The results show that the main factors affecting the deformation and instability of 13311 return air roadway include the driving under the influence of mining dynamic pressure in adjacent working face, the influence of the unreasonable layout of roadway and the support parameters of roadway. When the roadway is ar-ranged vertically with the upper coal seam,the support intensity of the roadway is low and the roadway is driven under the influence of mining dynamic pressure in adjacent working face,the lower coal mining roadway is easy to lose stabil-ity. To improve the stability of surrounding rock of 13313 return air roadway and effectively control the deformation of roadway,according to the physical and mechanical properties and stress characteristics of surrounding rock of test road-way,a targeted solution was put forward. Firstly,the layout of roadways is improved,and the lower coal seam mining roadways are arranged under the goaf,and the distance between the lower roadway and the remaining pillars in the goaf of the upper coal seam is not less than 20 m. Secondly,the width of coal pillar in roadway protection is increased,and the width of coal pillar in roadway protection section is increased to more than 20 m,so as to reduce the influence of dynamic pressure of adjacent working face. Finally,the high pre-stressing full anchor cable is used to strengthen the support,so as to improve the integrity and bearing capacity of the bolt anchorage section. Industrial test was carried out in 13313 return air roadway and the roadway pressure observation was carried out. The results show that after being af-fected by the mining dynamic pressure of the adjacent 13311 working face,the coal pillars in the section are integral and have good bearing capacity. The force of anchor cable reaches 250-300 kN,which is about 50% of its breaking force. The force of anchor cable increases steadily,and the deformation of roadway separation and surrounding rock is well controlled. The displacement of roof and floor of 13313 return air roadway is about 400 mm,and the displacement of two sides is about 300 mm,the deformation of roadway surrounding rock is effectively controlled,which ensures the overall stability of the roadway and achieves a good support effect. However,with the roadway layout,during the lower 13313 working face mining,due to the influence of the concentrated stress of the coal pillar in No. 11 coal seam above the working face,higher requirements were put forward for the management of its roof and coal wall,and great attention should be paid to it at that time.