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切顶留巷贯通相邻采空区覆岩破断特征研究及应用

Research on the characteristics of overlying rock fracturing in roadway maintained by roof cutting and connecting adjacent goaf and its application

  • 摘要: 为研究切顶留巷工作面覆岩裂隙演化特征, 通过物理相似模拟分析了采动裂隙发育高度、离层量及应变分布规律, 探讨了切顶留巷开采顶板结构演变特征及覆岩非对称断裂模式。基于虚功原理与塑性铰相关理论, 给出了切顶留巷开采不同阶段顶板破断块体尺寸计算公式。研究结果表明: ①首采工作面切顶侧垮落带裂隙较为发育; 未切顶侧裂隙带裂隙较为发育。②非首采工作面贯通相邻采空区后, 覆岩裂隙及离层量曲线均呈非对称分布特征, 未切顶侧裂隙被压实闭合, 切顶侧裂隙稳定存在; 相较于未切顶侧, 切顶侧离层量小0.46~8.50 mm, 裂隙发育程度低。③首采工作面低位岩层初次断裂形态呈“U+Y”状, 切顶侧断裂线平行于切顶方向; 非首采工作面低位岩层破断呈“矩形”, 高位岩层初次破断形态呈非对称“O+X”状, 周期破断呈“U+Y”状, 断裂迹线偏向于未切顶侧。④非首采工作面高位岩层破断步距增加, 破断块体尺寸增大, 单位体积内裂隙数量减少, 瓦斯向上运移难度增大。⑤非首采工作面卸压瓦斯治理, 需适当降低抽采钻孔布置高度; 确定了切顶留巷工作面卸压瓦斯高效抽采区域, 现场试验钻孔瓦斯抽采效果验证了区域划分的准确性。

     

    Abstract: To investigate the fracture evolution characteristics of the overlying strata in a roof cutting and roadway retaining (RCRR) mining face, physical similarity simulation was employed to analyze the development height of mining-induced fractures, bed separation, and strain distribution. The evolution characteristics of the roof structure and the asymmetric fracture pattern of the overlying strata in RCRR mining were systematically explored. Based on the virtual work principle and plastic hinge theory, calculation formulas for the broken block size of the roof at different stages of RCRR mining were derived. The results show that tIn the first mining face, fractures are more developed within the caved zone on the roof-cutting side, while fractures within the fractured zone are more prevalent on the non-roof-cutting side. After the non-first mining face of the roof-cut retaining roadway penetrates the adjacent goaf, the overlying rock fracture and the separation volume curve are asymmetrically distributed. The fracture on non-roof-cut side is compacted and closed, while fractures on the roof-cut side are stable. The bedding separation is reduced by 0.46~8.50 mm, along with the reduction of fracture development degree. The initial fracture morphology of lower-level rock strata in the first mining face of the roof cutting roadway is ''U + Y'', and the fracture line on the roof cutting side is parallel to the roof cutting direction. The lower-level rock strata of the non-first mining face is broken in a "rectangle" pattern, and the higher-level rock strata is broken in an asymmetric ''O + X'' shape for the first time. The periodic breaking is in a combined ''U + Y'' shape, and the fracture trace biased towards the non-cut side. In non-first mining faces, the breaking step of high-level rock strata increases, producing the larger sizes of fractured blocks with a decrease in the number of fractures per unit volume. Consequently, the upward migration of methane becomes more difficult. Based on this, it is proposed that for methane pressure relief management in non-first mining faces with top-cutting and gob-side entry retaining technology, the height of methane drainage boreholes should be appropriately reduced. By considering fracture characteristics, the position of key strata and air leakage effects, an efficient methane drainage area for working faces with roof cutting and roadway retaining is determined. Field tests on methane drainage from boreholes have verified the accuracy of the zoning.

     

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