Research on mining technology of extra-thick coal seam under rich water aquifers in a bitter cold steppe region

The Mindong Mine, which belongs to the Shenhua group, China, is located in the bitter cold steppe region of the eastern part of Inner Mongolia, where the ecological environment is seriously restricted by underground water. In order to reduce the destruction of extra-thick coal seam mining to underground aquifer and the fragile surface grassland ecosystem, field engineering detections, theoretical analysis and simulation experiments were adopted to study the reasonable mining method of extrathick coal seam under rich water aquifer in Mindong Mine. Through the research on mining geological conditions and hydrogeological condition of mine, three extra-thick aquifers were detected over the roof of 16-3up coal seam, the first mining coal seam of mine. The upper water-enriched region was detected by the joint geophysical prospecting methods combined ground transient electromagnetic method and underground DC electrical method. The height of water-flowing fractured zone and its ratio to the mining height were measured through numerical simulation and grout loss of boreholes. By adjusting the mining height of coal seam to avoid the height of water flowing fractured zone reaching the upper aquifer, the aim of preventing groundwater system from destroying was achieved. Field practices indicate that the underground water is stable and the grassland ecosystem of mine is well protected.