Characteristics and sedimental control of mine water outflow in Hujirt mining area

Hujirt mining area in Ordos basin is a deep-buried Jurassic coalfield with high water pressure, large water volume and uneven water abundance. Each mine is facing serious pressure of mine water hazard prevention and control. In order to clarify the water outflow conditions and main controlling factors of the coal seam roof of the mine in this area, the research on geological deposit and water-producing horizon of roof boreholes, water-inrush from boreholes and water-inrush from working face was carried out. The results showed that within the water conducting fractured zone of Hujirt mining area, there are mainly meandering river sedimentary facies in Zhenwudong sandstone section of the third Member of Yan'an Formation and Qilizhen sandstone section of the first Member of Zhiluo Formation. The lithology of these two sections is fine-medium-coarse sandstone. In the early stage of the Zhiluo Formation, a set of fluvial facies deposits developed, which resulted in erosion of Yan'an Formation. coal seam 2^-1 was missing in the Menkeqing and Muduchaideng minefields in the middle of the mining area, and the thickness of Qilizhen sandstone section is large. However, the coal seam 2^-1 on both sides of the mining area is relatively preserved, and the sandstone thickness in Qilizhen is relatively thin. The water inflow from pre-drainage boreholes in coal working face roof mainly came from Qilizhen sandstone aquifer, and there are significant differences in water inrush from bore holes in different mines. The water inflow from boreholes in the middle of the scouring zone of paleao river bed is larger than that from boreholes on both sides of the scouring zone of paleao river bad, which corresponds well to the geological sedimentary facies of the roof. The difference of geological conditions(sedimentary facies) of coal seam roof not only controlled the amount of water inflow in the mining process, but also affected the variation law of water inflow in the working face.