不同开采方式下煤的损伤特性及渗流路径分布特征研究

Study on the damage characteristics and seepage path distribution of coal under different mining methods

  • 摘要: 突水灾害是深部煤矿开采过程中最具危险性的灾害之一。煤在采动应力的作用下产生损伤裂隙形成渗流路径, 直接影响突水风险。文中通过含轴、围压循环的三轴渗流试验, 并利用高精度扫描仪进行三维裂隙扫描, 系统研究了保护层开采(PCM)、放顶煤开采(TCM)和无煤柱开采(NM)3种开采方式下深部煤的损伤特性和渗流路径分布特征。结果表明: 高应力加载幅值显著加剧了煤样的变形, 并驱动滞回环由稀疏型向发散型转变, TCM与NM在循环后期存在失稳风险; TCM与NM的损伤积累速率显著高于PCM, 其破裂面损伤程度也更加严重; 渗透率随应力水平的提升呈阶段性增长, 高应力加载幅值促进裂隙扩展与贯通, 显著增强渗流通道的连通性; PCM、TCM和NM的渗流路径分别呈现分叉树型、网状型和面状型, 渗流效果依次递增。

     

    Abstract: Water inrush disaster is one of the most threatening disasters in the process of deep coal mining, coal under the action of mining stress to produce damage fractures to form seepage paths, groundwater through these seepage paths into the working face to cause water inrush disasters, different mining methods caused by different damage degrees and fracture distribution, resulting in different distribution of seepage paths, directly affecting the risk of water inrush. Therefore, the damage characteristics and seepage path distribution of deep coal under three mining modes: protective layer mining (PCM), top coal mining (TCM) and pillarless mining (NM) were systematically studied through the triaxial seepage test with axial and confining pressure cycles, and the three-dimensional fracture scanning with a high-precision scanner. The results show that the high stress loading amplitude (NM>TCM>PCM) significantly aggravates the deformation of coal samples and drives the hysteresis loop to change from sparse to divergent, and the strain mutation of TCM and NM in the late cycle indicates the risk of instability. The damage accumulation rate of TCM and NM was significantly higher than that of PCM, and the damage degree of the rupture surface became more serious. The permeability increased in stages with the increase of stress level, and the high stress loading amplitude promoted the fracture propagation and penetration, which significantly optimized the connectivity of the seepage channel. The seepage paths of PCM, TCM and NM showed bifurcation tree, network and surface shape, respectively, and the seepage effect increased sequentially. This study provides a reference for the damage control and prevention of water inrush in deep coal.

     

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