Inspection method and analysis of the effect of water cutoff curtain in open-pit coal mine

In order to reduce the water drainage of the studied open-pit mine, a curtain wall was constructed to cut off the river supply on the north side. According to the site construction conditions, four technologies were applied to construct the water cutoff curtain, such as the low-strength impermeable concrete underground continuous wall, HDPE impermeable film, ultra-high pressure angular variable speed jet grouting, and occluding pile. To test the effect of water cutoff curtain in the open-pit coal mine during construction, four surrounding well tests were carried out for three kinds of water cutoff curtain technologies, including low-strength impermeable concrete underground continuous wall, HDPE impermeable film and ultra-high pressure angular variable jet grouting. The test results show that the three technologies all had good water-blocking effects under the conditions of dynamic water and low temperature in the deep sand and gravel layer of the open-pit coal mine. The permeability coefficients respectively were 8.34×10^-7, 6.28×10^-7 and 7.85×10^-7 cm/s, which were basically consistent with the permeability coefficient obtained from the laboratory test of raw materials. Under the joint action of four curtain technologies, the water discharge was reduced obviously and the water intercepting effect was remarkable. The surrounding well test plays an inspecting role in the process of water cutoff curtain construction.