Water resources protection of mining area in Toutun river basin of Tianshan Mountains: a case study of Liuhuanggou Coal Mine

The ecological environment of the Northern Slope of Tianshan Mountain (Xinjiang Uygur Autonomous Region) is very fragile and water resources is in severe shortage due to a long time of coal mining. To solve water pollution and wasting problems caused by the seepage of the Toutun river on the northern slope of Tianshan Mountain, we analyzed the geological conditions of the Liuhuanggou Coal Mine, investigated the source of the goaf water recharge by hydrochemical methods and verified the goaf water recharge channel by ground transient electromagnetic and drilling methods, and the thickness of the water lock wall was theoretically calculated. On this basis we proposed the method of constructing a water cut-off curtain by grouting in small spaced straight boreholes on the ground. Finally, the construction effect was evaluated. The results showed that the hydrochemical characteristics of the goaf water in the Liuhuanggou Coal Mine are similar to those in Toutun river. It can be inferred that the recharge source of the goaf water is the Toutun river, and the water is recharged to the goaf through seepage channels such as fissures, abandoned roadways or mined-out areas. The results of TEM survey are consistent with the measured results by more than 75%, with the accuracy of plane positioning as high as 80%. The accurate location and boundaries of goafs and roadways were obtained by intensive borehole drilling with an interval of 2 m. C30 concrete and cement grout were used to fill the cracks and pores of the water channel, and then a 150-m-long and 30-m-wide water cut-off curtain was built between the goaf and the riverbed of Toutun river. The final goaf water inflow decreased to 251 m(3)/d, which was 97.2% lower than the maximum water inflow in 2018. It is estimated that goaf water will decrease 1 650 713 m(3) per year, which is of great significance to water resources protection and mine safety production in this area.