Calculation methods of seepage coefficient of water cut-off curtain

As an effective water prevention and control technology to block or reduce groundwater infiltration, water cut-off curtain has been continuously applied to underground and open pit coal mines in recent years. Influenced by quality defects such as joints and interlayer, the cut-off curtain generally needs to evaluate the anti-seepage performance by calculating the permeability coefficient, which can directly determine the anti-seepage quality of the cut-off curtain. Taking Zhanihe Open-pit Coal Mine and Yuanbaoshan Open-pit Coal Mine and Zhuxianzhuang Coal Mine as examples, the seepage coefficient of the water cut-off curtain is calculated by five methods, including the well enclosure pumping test, the complete well pumping test, the water injection test of the precipitation head, the water pressure test of the borehole and the core permeability test. The results show that there are differences in the results obtained by various calculation methods, but they can be mutually verified; the pumping test, water injection test and core permeability test are mostly used to test the permeability coefficient of the cut-off curtain in open pit coal mines, while the borehole water pressure test is more suitable for testing the seepage resistance of the grouting curtain in underground coal mines. The five calculation methods can respectively calculate the permeability coefficient of the water cut-off curtain from four different angles of point, line, surface and body, and comprehensive inspection of curtain wall seams and pouring quality. The combination of multiple methods can more comprehensively verify the permeability coefficient of the cut-off curtain.