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采动覆岩破断影响下裂隙诱发机制及三维空间特征

Mechanisms and three-dimensional spatial characteristics of fissures induced under the influence of fracture of mining overburden rocks

  • 摘要: 为掌握厚煤层开采覆岩破断及裂隙演化规律,以高河能源E2306工作面为背景,搭建了三维物理相似模拟试验平台,采用分布式光纤感测技术、钻孔窥视监测等相结合的方法,明晰了覆岩破断来压规律与裂隙分布特征。结合薄板弯曲理论,建立采场覆岩结构力学模型,揭示了采动覆岩破断影响下覆岩裂隙诱发机制,推演了采动裂隙区域发育形态。结果表明:工作面回采完毕,总计来压7次,垮落带、裂隙带发育高度分别为39、71 m。与该工作面现场结果一致,与理论计算数值吻合,符合该矿实际情况。处于垮落带高度内低位近场覆岩呈“对扇形”竖向破断,以“走向悬臂梁−倾向砌体梁”结构破断运动为主,纵向破断裂隙大量发育,横向水平剪切交错裂隙伴生。覆岩自下而上逐渐破断,处于裂隙带高度内高位远场覆岩呈横向破断,以“走向砌体梁-倾向砌体梁”结构破断运动为主,横向水平张拉离层大量发育。采空区边界区域内覆岩裂隙数量随工作面推进呈先增加后稳定的变化规律,走向裂隙数量变化呈抛物线型;采空区中部区域内覆岩裂隙数量随工作面推进呈先增加后减少的变化规律,走向裂隙数量变化呈马鞍型。覆岩破断来压后采空区中部持续承载受压,两侧岩层遭剪切破坏形成剪切下凹区与承载下凹区,区域范围随不同层位覆岩弯曲破断而扩大。采动裂隙区域发育形态由椭圆抛物带演变为两端下凹的椭圆抛物带形态,最终呈现为两端及顶部下凹的椭圆抛物带形态。

     

    Abstract: In order to grasp the overburden breakage and fissure evolution law of thick coal seam mining, a three-dimensional physical similarity simulation experiment platform was built with the background of E2306 working face of Gaohe Energy, and a combination of distributed fiber optic sensing technology and borehole peeping monitoring was used to clarify the overburden breakage and fissure distribution characteristics. Combined with the thin plate bending theory, the structural mechanics model of overburden rock in the quarry was established, revealing the mechanism of overburden rock fissure induced under the influence of mining overburden rock breakage, and deducing the regional development pattern of mining fissure. The results show that: after the face is mined back, the total number of pressures is 7 times, and the development height of the collapse zone and fissure zone is 39 m and 71 m respectively, which is consistent with the field results of the face, and matches with the theoretically calculated values, which is in line with the actual situation of the mine. In the height of the collapse zone, the low near-field overburden rock is broken vertically in a “pair of fan-shaped” way, with the structural breaking movement of “towards the cantilever beam-inclined to the masonry beam” as the main, with a large number of longitudinal breaking fissures developed, and transverse horizontal shear intersecting fissures accompanied. The overburden rock is gradually broken from the bottom up, and the overburden rock in the high far field within the height of the fissure zone is transversely broken, with the structural breaking movement of “towards masonry beam-inclined masonry beam” as the main movement, and a large number of transverse horizontally tensile delaminated layers are developed. The number of overlying rock fissures in the boundary area of the mining airspace shows the change rule of increasing and then stabilizing with the advancement of the working face, and the change of the number of strike fissures is parabolic; the number of overlying rock fissures in the middle area of the mining airspace shows the change rule of increasing and then decreasing with the advancement of the working face, and the change of the number of strike fissures is saddle-type. After the overburden rock breaks and pressurizes, the central part of the mining zone continues to bear pressure, and the rock layers on both sides are sheared and damaged to form shear concave area and bearing concave area, and the scope of the area expands with the bending and breaking of the overburden rock at different layers. The development pattern of the mining fissure area evolves from an elliptical parabolic zone to an elliptical parabolic zone with concave ends, and finally to an elliptical parabolic zone with concave ends and top.

     

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