深部巷道底板岩体渗透性高压压水试验研究

High-pressure water injection tests on permeability of deep rock mass under tunnels

岩体渗透性是反映岩体水力学特征的重要参数,为探究深部岩体的渗透性,采用钻孔高压压水试验手段,对东滩煤矿深部巷道底板四段岩体进行了现场原位压水试验,获得了大量实测数据。试验和数据分析结果表明:岩体在压水过程中经历了"隔水–导渗–稳渗"的过程,随着压水的进行,岩体的渗透性不断增强。东滩煤矿深部底板的厚层泥岩具有低阻弱渗的特点,厚层砂岩和互层具有高阻弱渗的特点,四段岩体原始状态下渗透性均较差。注水压力与流量关系曲线具有很好的指数关系,除厚层砂岩外,厚层泥岩和互层的注水压力–流量关系具有明显的分段性。岩体等效裂隙宽度随着注水压力的增大具有较好的指数关系且具有明显的分段性,即可分为突变点前的稳定阶段和突变点后的突增阶段。可通过裂隙宽度变化量?b是否大于0来判断岩体内是否发生明显渗流。研究结果有助于加强对深部岩体在水压作用渗透性变化的认识,为深部煤层的安全开采提供重要的参考依据。

The permeability is a very important factor to determine the hydraulic characteristics of rock mass. To study the permeability of deep rock mass, high-pressure borehole water injection tests are carried out to analyze the four segments of rock masses in Dongtan Coal Mine, and numerous data are obtained. The test results and analyses of data show that the rock mass goes through the process of“water resistance-seepage guiding-stable seepage”. The permeability of rock mass increases with the test process. The thick mudstone under the tunnel of Dongtan Coal Mine exhibits the behavior of low water anti-pressure and permeability, while the thick sandstone and other two rock masses show that of high water anti-pressure and low permeability. The four test rock masses are of low permeability. The regression results indicate the exponential relationship between injection pressure and flow rate with high regression coefficients. The curves of injection pressure and flow rate of thick mudstone and interbed exhibit significant segmentation expect those of thick sandstone. The relationship between injection pressure and equivalent fracture width shows obvious exponential relationship as well, and two significant segmentations appear, that is, stability before mutation and sudden increase after mutation. Whether seepage in the rock mass happens or not can be judged by the relation between?b and 0. The conclusions will help further understand the permeability of deep rock masses under high water pressure and may make an important reference for safety mining of deep coal mines.