Characterization of fissure distribution of overburden rock under roof cutting and entry retaining based on key strata theory
SHUANG Haiqing;XIN Yueqiang;LI Shugang;LIN Haifei;ZHOU Bin;SHANG Yingzhi;LIU Sibo
针对切顶留巷工艺使得切顶侧采空区覆岩裂隙分布改变的问题,采用物理相似模拟与数值模拟相结合的手段分析了切顶留巷工艺下采空区应力分布、覆岩运移和采动裂隙分布规律。在此基础上,基于关键层理论与采动覆岩卸荷膨胀累积效应,探讨了切顶与未切顶侧覆岩裂隙发育高度和离层裂隙区宽度的变化,分析了不同层位定向卸压瓦斯抽采钻孔抽采效果,验证和反演了切顶留巷工艺下覆岩裂隙分布规律。研究结果表明:切顶留巷工艺能有效降低切顶侧顶底板的应力集中,但应力仍会向煤岩深部传递;切顶使得垮落岩层厚度与顶板破断形式发生改变,导致裂隙带发育高度、亚关键层控制范围内离层裂隙区宽度产生变化;切顶侧端头垮落带高度为未切顶侧的2倍,裂隙带高度为未切顶侧的0.87倍,在裂隙带中下部,切顶侧的离层量和穿层裂隙数量均大于未切顶侧;切顶侧在煤层顶板8~30 m范围内裂隙发育量随距离增大而增大,在30~48 m范围内随距离增大而减小,裂隙主要分布于裂隙带中下部;不同层位抽采钻孔瓦斯浓度和流量的“错峰”验证了上述研究结论。研究结果对高瓦斯矿井切顶留巷工艺下卸压瓦斯治理具有一定参考价值。
Aiming at the problem of changing the distribution of overburden fissures in the overhead mining area due to the cutting and retaining roadway process, the stress distribution, overburden transport and mining fissure distribution law in the mining zone under the roof cutting and retaining roadway process were analyzed by means of a combination of physical similarity simulation and numerical simulation. On this basis, based on the key strata theory and the cumulative effect of unloading and expansion of mining overburden, the changes in the height of overburden fissure development and the width of fissure zones on the roof cutting and un-cutting sides were investigated, the extraction effect of the directional unloading gas extraction boreholes in different strata was analyzed, and the overburden fissure distribution law under the roof cutting and retaining roadway process was verified and inverted. The results shown that, the roof cutting and retaining roadway process can effectively reduce the stress concentration of the top and bottom plates on the roof cutting side, but the stress will still be transferred to the deeper part of coal. Roof cutting caused changes in the thickness of the collapsed rock layer and the form of roof breakage, which led to the changes in the height of the fissure zone development, and the width of the off-strata fissure zones within the sub-critical strata control range. The height of the collapsed zone on the roof cutting side was twice as much as that on the un-cutting side, and the height of the fissure zone was 0.87 times as much as that on the un-cutting side. In the middle and lower part of the fissure zone, the amount of off- strata and the number of penetrating fissures on the cut top side are larger than those on the uncut top side; the amount of fissure development on the roof cutting side were larger than those on the un-cutting side. The amount of fissure development on the coal seam roof of roof cutting side increased with the increasing distance in the range of 8~30 m, and decreased with the increasing distance in the range of 30~48 m, The fissures were mainly distributed in the middle and lower part of the fissure zone. The “staggered” gas concentration and flow rate of the extraction boreholes in different layers validated the above conclusions. The study results have certain reference value for the decompression gas management in high gas mines under the process of roof cutting and retaining roadway.
gas extraction;unpressurized gas;roof cutting and entry retaining;overburden fissures;cumulative expansion of overburden
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会