陷落柱填隙物全应力-应变过程的渗流特性研究

岩溶陷落柱易导通含水层与煤层从而引发底板突水事故,已经成为我国华北地区下组煤开采的重要安全隐患。对于固结良好的陷落柱,其填隙物的渗透性直接影响着陷落柱的整体渗透性,且在采动压力的影响下,陷落柱填隙物的渗透性也在不断发生变化。为研究不同应力状态下填隙物渗透率的变化规律,对填隙物进行固结重塑,并利用MTS815.02渗流试验系统对重塑后不同初始含水率的填隙物试样进行了不同围压条件下的全应力-应变过程的渗流特性试验。试验结果表明:1)陷落柱填隙物全应力-应变过程渗透率的变化曲线可划分为压密段、破坏段和蠕变段,渗透率对应的呈现出减小-增大-减小的变化规律;2)填隙物的全应力-应变过程的渗透率峰值随围压的增大而减小,其峰值比与围压差存在指数函数关系;3)填隙物的初始渗透率和孔隙度随初始含水率的增大而增大,渗透率比和孔隙度比存在幂函数关系,在全应力-应变过程中渗透率峰值与初始值的差随初始含水率的增大而减小。

Research on permeability characteristics of karst collapse column fillings in complete stress-strain process

The floor water-inrush accident caused by karst collapse column is easy to break over the aquifer and coal seam. This kind of accident has become the serious danger of lower group coal mining in northern China. For the well-consolidated collapse column, the permeability of the fillings directly affects that of the overall collapse column, and the permeability of fillings constantly changes under the influence of mining. The study on seepage characteristic of collapse column fillings is conducted with MTS815.02 seepage test system in a complete stress-strain process and the variation of permeability under different strain states. Meanwhile the influence of initial moisture content and confining pressure on the fillings permeability is analyzed in this test. The results show that: 1) The representative stress-strain-seepage relationship of fillings is divided into pressure elastic segment, damage and creep stage, and the permeability presents the change rule of decrease-increase-decrease in complete stress-strain process; 2) The peak value of permeability decreases with the increasing confining pressure, and the ratio of the permeability in the complete stress-strain process has a exponential function relation with the confining pressure difference in complete stress-strain process; 3) The initial permeability and porosity of fillings decreases with the increase of initial moisture content, and the ratio of permeability and porosity have a power function relationship. The difference between peak and initial permeability decreases with the increasing initial moisture content in complete stress-strain process.