近距离煤层群沿空掘巷巷道围岩破坏特征与应力分布及控制

    Research on failure characteristics and stress distribution and control of surrounding rock in gob-side entry driving of closed-distancecoal seam groups

    • 摘要: 针对土城矿近距离煤层群留窄煤柱沿空掘巷巷道变形量大、难支护的问题,为确定合理的巷道围岩控制方案,本文采用理论分析、数值模拟及现场实践相结合的方法,研究了上覆煤层工作面回采后底板最大破坏深度,留设窄煤柱的合理宽度,上煤层、下煤层开采后叠加应力对掘巷位置的应力影响,掘巷后巷道围岩应力分布及变形破坏特征,并以此提出巷道围岩控制方案,以及根据现场实测数据验证所提方案的合理性。研究结果表明,上覆煤层回采结束后,底板最大破坏深度为17.1 m,小于两煤层间的垂直距离;窄煤柱的合理宽度范围为2.48~3.57 m,并根据工程类比法最终确定窄煤柱宽度为3.0 m;数值模拟结果显示,单一的上煤层或下煤层开采对于巷道掘进区域的应力影响较小,而当上煤层、下煤层均开采时,对掘巷区域的应力影响显著;巷道围岩呈现非对称变形,煤柱侧顶板和帮部变形量大于实体煤侧,实体煤侧底鼓量大于煤柱侧;采用主被动协同支护方案后,巷道顶底板变形量缩减至原支护的82%,帮部变形量缩减至67%,巷道围岩控制效果理想,验证了所提支护方案的合理性。研究揭示了上煤层、下煤层开采对中间煤层留窄煤柱沿空掘巷的应力影响,为类似条件下留窄煤柱沿空掘巷提供借鉴与参考。

       

      Abstract: Aiming at the problems of large deformation and difficult support of gob-side entry driving with narrow coal pillar in closed-distance coal seams group of Tucheng Coal Mine, to determine a reasonable surrounding rock control scheme for the roadway, this paper adopts the combination of theoretical analysis, numerical simulation and field practice to study the maximum failure depth of the floor after the stoping of the overlying coal seam working face, the reasonable width of the reserved narrow coal pillar, the stress influence of superposed stress induced by upper and lower coal seam mining on the roadway driving position, as well as the stress distribution and deformation-failure characteristics of roadway surrounding rock after excavation. On this basis, a surrounding rock control scheme for the roadway is put forward, and its rationality is verified by field measured data. The results show that the maximum failure depth of the floor is 17.1 m after the stoping of the overlying coal seam, which is smaller than the vertical distance between the two coal seams; the reasonable width range of the narrow coal pillar is 2.48-3.57 m, and the final narrow coal pillar width of 3.0 m is determined by engineering analogy method. Numerical simulation results demonstrate that the mining of single upper or lower coal seam has little impact on the stress of roadway driving area, while the simultaneous mining of upper and lower coal seams produces a remarkable stress effect on the driving area. The surrounding rock of the roadway shows asymmetric deformation: the deformation of roof and rib on the coal pillar side is larger than that on the solid coal side, and the floor heave on the solid coal side is greater than that on the coal pillar side. After adopting the active-passive combined support scheme, the roof-floor deformation of the roadway is reduced to 82% of that with the original support, and the rib deformation is reduced to 67%, presenting an ideal surrounding rock control effect and verifying the rationality of the proposed support scheme. This research reveals the stress influence of upper and lower coal seam mining on gob-side entry driving with narrow coal pillar in the intermediate coal seam, which can provide reference for similar gob-side entry driving engineering with narrow coal pillar under the same mining and geological conditions.

       

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