废弃矿井双煤层开采覆岩裂隙发育规律研究

    Study on the development laws of overburden rock fracture in double-seam mining of abandoned mine

    • 摘要: 随着矿产资源的不断开采,越来越多的矿井被废弃。然而,这些废弃矿井中仍然蕴藏着大量尚未开发的煤层气资源,具有巨大的潜在价值。煤层开采后形成的覆岩裂隙场成为了废弃矿井中煤层气运移的主要通道。因此,研究和掌握覆岩裂隙场的发育规律,对精准开发和利用废弃矿井中的煤层气资源具有重要意义。本文以潘一矿区的双煤层开采为工程背景,采用理论分析、UDEC数值模拟和物理相似模拟等方法,对双煤层开采后的覆岩裂隙场发育规律进行了系统研究。研究结果表明:上部煤层裂隙带发育高度为58.73~81.71 m,当下部煤层推进170 m时,关键层1处产生穿层裂隙,原先孤立的各离层裂隙相互连接,引起上采空区、下采空区连通,此时上下部煤层裂隙带贯通,下部煤层裂隙带发育高度约为41.8 m,裂隙带最终高度为116.64~139.62 m;上部采空区覆岩裂隙发育历程大致分为两个阶段,上部煤层开采时:裂隙产生-发育-闭合,下部煤层开采时:裂隙重新发育-重新闭合;长时蠕变作用使裂隙的分布更加密集,但其形态未发生显著改变,最终形成的双煤层裂隙场呈现出“马鞍+蟹壳”的复合型结构;研究成果揭示了废弃矿井双煤层开采覆岩裂隙发育规律,并根据长时蠕变后的覆岩裂隙场分布特点提出了废弃矿井中双煤层矿井瓦斯运移的主要通道,可为类似废弃矿井的瓦斯精准开采提供借鉴。

       

      Abstract: As mineral resources continue to be exploited, an increasing number of mines are being abandoned. However, these abandoned mines still contain significant undeveloped coalbed methane (CBM) resources, presenting immense potential value. The overburden rock fracture field formed after coal seam extraction becomes the main pathway for CBM migration in abandoned mines. Therefore, studying and understanding the development patterns of the overburden rock fracture field is of great importance for the precise development and utilization of CBM resources in abandoned mines. This paper takes the double-seam mining in the Panyi Mine Area as an engineering background and employs theoretical analysis, UDEC numerical simulation, and physical similarity simulation methods to systematically study the development patterns of the overburden rock fracture field after double-seam mining. The research results show that the fracture zone height in the upper coal seam is approximately 58.73 to 81.71 meters. When the lower coal seam advances 170 meters, key stratum 1 generates through-layer fractures, connecting previously isolated interlayer fractures and causing the upper and lower goafs to interconnect. At this point, the fracture zones of the upper and lower coal seams are connected, with the lower coal seams fracture zone developing to a height of approximately 41.8 meters and the final fracture zone height reaching about 116.64 to 139.62 meters. The overburden rock fracture development in the upper goaf can be roughly divided into two stages: during the upper coal seam mining, fractures generate, develop, and close; during the lower coal seam mining, fractures redevelop and reclose. Long-term creep effects result in a denser distribution of fractures, but their shape does not change significantly, ultimately forming a “saddle+crab shell” composite type structure for the double-seam fracture field. The research outcomes reveal the development patterns of the overburden rock fracture field in abandoned mines with double-seam mining. Based on the fracture field distribution characteristics after long-term creep, the study proposes the main pathways for CBM migration in abandoned double-seam mines. These findings can serve as a reference for the precise extraction of gas in similar abandoned mines.

       

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