Hydrogeological Characteristics of Roof of Deep Buried Working Face in Hujirt Mining Area

Jurassic deep-buried coalfield in Ordos Basin was the key area of coal resources development in the future. Water control was the most important task for mine safety production. In order to make clear the hydro-geological characteristics of the coal seam roof, researches were carried out on geological deposits, spatial distribution of aquifers, water-rich laws and surface water inflow in deep-buried working face of Hujirt Mining Area. The results showed that sand shale interbed was developed on the roof of main coal seam in Hujirt Mining Area, which was influenced by fluvial deposits. Due to the infiltration of the strong water-rich loose layer in Maowusu Desert, the Zhenwudong sandstone and Qilizhen sandstone had the characteristics of high water pressure, strong water-rich and non-uniform. Especially in undisturbed Qilizhen sandstone aquifer, the water pressure and the single borehole water inflow were 6 MPa and 150 m3/h to 160 m³/h respectively. The results of drainage test and pre-drainage before coal mining showed that the aquifers directly filled with water had good drainability. Most of the roof borehole water inflow and pressure were reduced to less than 5.0 m³/h and 1.0 MPa respectively before coal mining in advanced mining section (0 m to 600 m). During the whole mining process, the total drainage was 787×10⁴ m³ and the water-rich coefficient was 1.48. The water-rich coefficient was greater than the value in Shenfu and Xinjie Mining Area. Direct water-filled aquifers of coal seam roof were rich in water in Hujirt Mining Area. In order to ensure the safe development of coal resources in Jurassic deep-buried coalfield in Ordos Basin, it was necessary to strengthen water prevention and control work.