## 2 Study Area and Objectives  
The Hanjiawan Coal Mine is located in the northern part of the ShenFu mining area. The mine has a production capacity of 4.0 Mt/a and mines three seams, namely the 2\({}^{-2}\) seam, 3\({}^{-1}\) seam, and 4\({}^{-2}\) seam, with the 3\({}^{-1}\) seam near completion and the 4\({}^{-2}\) seam in the primary stage. Seam production is gentle, and the seams are nearly horizontal, with an inclination of approximately 1-3\({}^{\circ}\). The seams are mined in a downward direction. The 2\({}^{-2}\) coal seam is located in the upper part of the fourth section of the Yan'an Group. The thickness of the coal seam ranges from 0.5 to 5.5 m, with an average of 4.06 m. The average depth of the coal seam is 80 m, with a recoverable area of 11 km\({}^{2}\). The thickness of the coal seam thus from west to east. The eastern boundary of the well field is the not mining area along the coal seam strike of 418 m. The room and pillar mining area is located between the long-wall mining area and the not mined area within a width of 135 to 550 m. The long-wall mining area is located to the west of the room-and-pillar mining area. The working face is 268 m long, with a mining height of 4 m and a strike length of 1820 m. The working face uses fully mechanized coal mining with a long wall, mining the entire height at once and managing the roof of the mining area by the collapse method. The thickness of the 3\({}^{-1}\) coal seam is 2.1-3.4 m, with an average of 2.9 m. The recoverable thickness is 1.5-3.4 m, with average of 2.95 m. The burial depth is 101.50-157.07 m, and the recoverable area is 12.77 km\({}^{2}\). The geological structure of the coal seam is simple; locally, it contains a layer of a band of approximately 0.3 m thickness, and the lithology of the band is mainly sandstone. The relationship between the upper and lower coal seams is shown in Figure 1, and the physical and mechanical parameters of the coal seams are shown in Figure 2. The overall research framework structure is shown in Figure 3.  
There are two reservoirs of the surface within the Hanjiawan coal mine well-field, one with an area of 9280 m\({}^{2}\) and the other with an area of 7876 m\({}^{2}\), half of which is within the Hanjiawan well-field. The average depth of water in the reservoirs is 1.8 m, and the depth of water can reach approximately 3 m during a period of abundant water. The total volume of water accumulated in the two reservoirs during the period of abundant water can reach  
Figure 1: Plane section location drawing of coal seam 2\({}^{-1}\) and 3\({}^{-1}\) in the study area. 51,468 m\({}^{3}\), forming a potential source of water for inrush water disasters. The northern part of the well field, approximately 1.5 km from the Bu Bag Trench to Liu Gen Ditch, is a water-rich area; the upper reaches are Bu Bag Trench wetlands. The exploration data show that the water-bearing rock section from 2\({}^{-2}\) to 3\({}^{-1}\) coal has a thickness of 29.08-56.66 m, with an average thickness of 39.24 m. Some boreholes show  
Figure 3: Physical and mechanical geological characterization and geological histogram. Figure 2: The whole work of a schematic figure. water gushing and leaking at the roof of the 3\({}^{-1}\) coal seam, indicating that the fracture development is uneven and does not constitute the same saturated water-bearing layer. The Middle Jurassic Zoro Formation and Yan'an Formation weathered rock fracture water-bearing rock groups are widely distributed and thick. With small spacing from the 2\({}^{-2}\) coal seam, the height of the coal mining inrush waters fracture zone will be directly penetrated, which is the main water-filled layer of the mine. In areas where the thickness of the loose sand layer is large, the diving of the loose rock type of the Fourth Series and the fracture water of the over rock of the coal system are the main sources of water filling in the mine.