School of Civil Engineering, Henan Polytechnic University, Jiaozuo, 454000, China.
School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, 454000, China.
Environ Sci Pollut Res Int. 2023 Nov;30(51):110995-111007. doi: 10.1007/s11356-023-30230-3. Epub 2023 Oct 6.
Conduction between the unique geological formation karst collapse pillar (KCP) and the fractures caused by mining in the coal seam floor can lead to catastrophic water inrush disasters in many coalmines in Northern China. It is widely recognized that seepage mutation induced by the migration/loss of KCP fillings (highly broken rocks filling the fractured rocks) happens during occurrence of the KCP-related water inrush. However, roles of fluid path (mining-induced fracture) scale and KCP filling porosity in seepage mutation evolution remain unclear. Here, we conducted seepage tests on natural KCP fillings containing rock particles of different sizes. The filling specimens were deformed to different porosities from 14 to 26% through axial compression, and small to large fluid paths were simulated by seepage plates with distinct pore sizes from 2.5 to 12.5 mm. We found that seepage mutation occurs with significant permeability enhancement by 2 orders of magnitude under a pore diameter of 12.5 mm and a specimen porosity of 26%. There is a strong linear relationship between specimen permeability and Reynolds number (Re) over seepage mutation. The mutation is caused by the sudden collapse of the specimen skeleton and subsequent quick outflow of the particles. Therefore, it is inferred that the KCP-related water inrush is more likely to happen when highly porous KCP fillings are present and mining-induced fractures are well developed.
在中国北方的许多煤矿中，独特的地质构造岩溶陷落柱（KCP）与煤层底板采动裂隙之间的导通可能导致灾难性的突水灾害。人们普遍认为，在 KCP 相关突水发生时，KCP 填充物（高度破碎的岩石填充破碎的岩石）的迁移/损失会引起渗流突变。然而，流体通道（采动裂隙）尺度和 KCP 填充孔隙率在渗流突变演化中的作用仍不清楚。在这里，我们对含有不同粒径岩石颗粒的天然 KCP 填充物进行了渗流试验。通过轴向压缩，将填充试样的孔隙率从 14%变形到 26%，并通过具有明显孔径为 2.5 至 12.5 毫米的渗流板模拟从小到大地域的流体通道。我们发现，在孔径为 12.5 毫米和试样孔隙率为 26%的条件下，渗流突变会导致渗透率显著提高 2 个数量级。试样渗透率与雷诺数（Re）之间存在很强的线性关系。突变是由试样骨架的突然坍塌和随后颗粒的快速流出引起的。因此，可以推断，当高度多孔的 KCP 填充物存在且采动裂隙发育良好时，KCP 相关突水更有可能发生。
