煤层底板厚层砂岩含水层可疏性综合评价

    Comprehensive evaluation of drainage feasibility for thick sandstone aquifer of floor

    • 摘要: 为了指导煤层底板砂岩水害的防治工作,需要对含水层的可疏性进行合理评价。结合典型矿井的水文地质条件和水害案例,对水文地质钻孔抽水试验资料进行分析,初步评价了底板砂岩含水层具有可疏性。采用大流量大降深放水试验,对观测孔水位单位时间内的变化曲线斜率进行研究,底板砂岩含水层疏降快,恢复慢,增加放水量可有效加快含水层水位的疏降,多孔大流量疏放水可以最大程度上激发地下水流场的变化,在一定范围内对底板砂岩含水层进行疏水降压,可以持续降低地下水水位;单孔放水和多孔放水过程中水位恢复时间分别占放水时间的77.92%和86.21%,而水位仅分别恢复了最大降深的39.11%和46.56%,说明了含水层水位易疏降,难恢复。根据对放水孔的水量和水压变化情况分析,长时间疏水降压会使水量逐渐减小,并产生大幅降深,证明底板砂岩含水层补给条件一般。结合井田地层和构造条件,提出底板砂岩含水层位于相对较为封闭的隔水空间有利于疏水降压。结果表明:利用抽水试验和放水试验资料,从含水层水位单位时间变化速率、抽水和恢复水位曲线、放水孔水压变化和含水层边界条件等方面,可以对底板厚层砂岩含水层可疏性进行综合评价。

       

      Abstract: In order to guide the water disater prevention and control of floor sandstone, it is necessary to make reasonable evaluation on the aquifer. Based on the hydrogeological conditions of typical mine and water disaster case, the pumping test data of hydrogeological boreholes are analyzed, and the floor sandstone with drainage feasibility was proved. The water level variation curve slope per unit time of observation boreholes was studied by the dewatering test with large inflow and drawdown. The drainage rate of floor sandstone aquifer is fast and the recovery rate is slow. Increasing the drainage amout can accelerate the drawdown of aquifer water level effectively. The drainage with large inflow can stimulate the change of groundwater flow field to the greastest extent. In a certain range, the groundwater level can be decreased continuously by drainage of sandstone aquifer below the coal seam. In the process of single-borehole and multi-borehole drainage, the recovery time of groundwater level accounted for 77.92% and 86.21% of the dewatering time, while the groundwater level only recovered 39.11% and 46.56% of the maximum of drawdown, indicating that the groundwater level of sandstone aquifer is easy to drain and difficult to recover. According to the change of water quantity and water pressure of the dewatering boreholes, the water quantity will gradually decrease and the groundwater level will decrease significantly after a long time drainage, which proves that the recharge condition of the sandstone aquifer is general. Combined with the strata and strucural conditions of the coal field, it is suggested that the location of the sandstone aquifer in a relatively closed water-repellent space is conducive to drainage. The results show that based on the data of pumping test and dewatering test, the drainage feasibility of thick sandstone aquifer can be comprehensively evaluated from the unit time change rate of groundwater level, pumping and recovery goundwater level curve, water pressure change of dewatering boreholes and boundary condition of aquifer.

       

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