蒙陕接壤区典型煤层开采顶板周期性变形破坏及涌水响应特征

Periodic roof deformation and failure and associated water inflow characteristics during the mining of typical coal seams in the Inner Mongolia-Shaanxi contiguous area

  • 摘要: 【目的】 煤矿开采扰动破坏覆岩含/隔水层结构,造成集中涌水,影响矿井安全生产。【方法】以面临典型顶板砂岩水影响的蒙陕接壤区主采煤层3-1煤开采涌水过程为研究对象,采用物理相似材料模拟、数值仿真模拟、现场原位监测3种方法,并通过周边地质和开采条件相似矿井实测数据对比,分析3-1煤典型工作面开采煤体支承压力周期性演变规律、采空区覆岩垂直位移演变规律,定量获取实验室尺度顶板周期来压瞬间微震能量事件变化特征,综合确定顶板导水裂隙带随采发育特征,以及顶板涌水随覆岩周期来压变化趋势。【结果和结论】 结果表明:工作面开采覆岩初次来压步距约40 m,周期性来压步距12~28 m,覆岩破断瞬间围岩周期性来压呈现 “先增后稳定”的趋势,在推进至第5次周期来压(推进距离约140 m)时,超前支承压力达到最大,覆岩周期性来压、破断瞬间垂直位移峰值随采呈现“之”字型变化特征,同样,位移监测数据、微震事件总能量、事件频次等综合指标指示,在第5次周期来压瞬间,覆岩垂直位移变幅达到最大值,塑性区发育高度基本稳定;导水裂隙带发育最大高度在120 m左右,将直接沟通顶板直罗组砂岩含水层,地下水随采涌入过程呈现两种波动变化趋势,工作面全局尺度上呈现长周期“阶梯式”增长趋势,“阶梯式”增长周期约800 m,局部尺度呈现短周期“振荡”变化趋势,振荡周期16~48 m,并表现出与覆岩来压周期之间的较强关联性。研究结果为工作面涌水量预测以及防排水系统布设提供参考。

     

    Abstract: Objective The disturbance of coal mine mining damages the aquifer/aquiclude structures of the overburden, causing concentrated water inflow and further affecting safe production in mines. Methods Using methods of the physical simulation of similar materials, numerical simulation, and on-site in situ monitoring, this study investigated the water inflow during the mining of the dominant 3-1 coal seam, typically influenced by water in sandstones on the coal seam roof, in the Inner Mongolia-Shaanxi contiguous area. By comparing the measured data of mines with similar geological and mining conditions in the surrounding area, this study delved into the periodic evolutionary patterns of both the coal support pressure and the vertical displacement of the overburden in the goaf during the mining of typical mining faces of the 3-1 coal seam. Accordingly, this study quantitatively analyzed the variations of microseismic events at the moment of periodic roof weighting on the laboratory scale. Finally, this study comprehensively determined the development characteristics of the hydraulically conductive fracture zones on the coal seam roof with mining, along with the trend of water inflow from the roof varying with the periodic weighting of the overburden. Results and Conclusions Key findings are as follows: (1) With the mining face advancement, the overburden exhibited a step distance of about 40 m in the initial weighting and of 12-28 m in periodic weighting. At the moment of the overburden fracturing, the periodic weighting of surrounding rocks first increased and then stabilized. As the mining face advanced to the fifth periodic weighting (advancement distance: 140 m), the advanced support pressure peaked, with the peak vertical displacement of the overburden at the moment of both periodic weighting and fracturing showing zigzag-shaped variations with coal mining. Similarly, comprehensive indicators, such as displacement monitoring data, total energy of microseismic events, and event frequency, indicate that at the moment of the fifth periodic weighting, the vertical displacement amplitude of the overburden peaked, while the height of the plastic zone remained roughly stable. (2) The hydraulically conductive fracture zone, with a maximum height of about 120 m, would be directly connected to the sandstone aquifer of the Zhiluo Formation on the coal seam roof. The groundwater inflow with coal mining manifested two wavy changing trends. The groundwater inflow displayed stepped growth with a long cycle of about 800 m on the global scale of the mining face but, locally, exhibited oscillatory changes with short cycles of 16-48 m and a strong correlation with the weighting period of the overburden. The findings of this study provide a reference for both the prediction of the water inflow of mining faces and the arrangement of the water prevention and drainage system.

     

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