直覆硬厚顶板临空巷强动载矿压显现及多层次卸压防控技术研究

Strong dynamic mining pressure behavior in gob-side roadways and multi-level pressure relief prevention and control of thick-hard and overlying roof

  • 摘要: 为了改善二次复用巷道受采动高应力影响引起的强动载矿压显现,基于直覆硬厚顶板煤层开采地质条件和力学参数,采用钻孔窥视、MEMS倾角传感器监测、理论分析等方法,研究了单侧采空下侧向顶板垮落特征,分析了临空巷围岩变形特征,揭示了直覆硬厚顶板临空巷强动载矿压显现机理。研究结果表明:直覆硬厚顶板在工作面侧向以“悬梁”状态存在,悬梁长度为28.8 m。采动影响下顶板破断微震特征显示,垂向上临空巷强动载矿压主导岩层为30 m范围内低位顶板岩层,倾向上微震事件集中在临空巷侧,工作面中部及靠近下一工作面侧顶板微震事件少,顶板难以充分垮落。相邻工作面回采后,临空巷煤柱侧应力大于采煤侧,煤柱侧和采煤侧围岩应力呈非对称性分布状态。受采空区直覆硬厚顶板侧向垮落不充分影响,应力一直维持在高位,进而导致本工作面回采时,临空巷发生强动载矿压显现。为此,提出了顶板爆破联合区域压裂多层次卸压技术,有效切断本工作面侧中部、隅角区顶板及相邻工作面隅角区顶板,在二次复用巷道受动压影响前,超前治理巷道顶板,从源头上调控临空巷围岩应力分布,促使采空区侧向顶板及时垮落。卸压后,巷道整体变形降到巷道断面10%以下,煤柱支承压力影响范围和应力集中程度显著降低,改善了临空巷围岩应力环境。

     

    Abstract: In order to improve the mine pressure behavior of strong dynamic load caused by high stress in secondary reuse roadway, based on the mining geological conditions and mechanical parameters of directly covered hard thick roof coal seam, the methods of drilling observation, MEMS tilt sensor monitoring and theoretical analysis are adopted. The caving characteristics of lateral roof under unilateral goaf are studied, the surrounding rock deformation characteristics of goaf roadway are analyzed, and the mechanism of strong load pressure behavior of goaf roadway with direct hard thick roof is revealed. The results show that: the straight covered hard thick roof exists in the state of “suspended beam” in the lateral direction of the working face, and the length of the suspended beam is 28.8 m. Mining activities have revealed specific microseismic features in roof fracturing. In the vertical direction, the strong dynamic load mine pressure in gob-side roadway is dominated by low roof strata within the range of 30 m. In the inclination, microseismic events are mainly concentrated on the side of the goaf, with fewer events occurring in the central part of the working face and near the side of the adjacent working face,which shows that the roof collapse is insufficient. After the mining of the adjacent working face, the stress on the coal pillar side of the gob-side roadway is greater than that on the coal mining side, and the stress distribution of surrounding rock on the coal pillar side and coal mining side is asymmetrical. Under the influence of the insufficient lateral collapse of the hard thick roof directly covered in the goaf, the stress has been maintained at a high level, which leads to the strong dynamic load pressure in the gob-side roadway during the mining of the working face. For this reason, the multi-level pressure roof relief technology of blasting combined with fracturing is put forward to control the roof of secondary reuse roadway ahead of mining, which effectively separate the roof in the central and corner areas of mining face, as well as the roof in the corner areas of the adjacent mining face. Before the secondary reuse tunnel is impacted by dynamic pressure, proactively manage the tunnel roof. Regulating the stress distribution in the surrounding rock of the adjacent empty tunnel at its source ensures the timely collapse of the lateral roof in the mined-out area. After pressure relief, the overall deformation of the roadway is reduced to less than 10% of the roadway section, the influence range of abutment pressure and stress concentration of coal pillar are significantly reduced, and the surrounding rock stress environment of the gob-side roadway is improved.

     

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