e " ree Under Mining" (mining under the buildings, the railways, and the waters) coal resources are stored in the central and eastern China. Many large-scale mine disasters occurred due to overburden strata movement and surface subsidence. Longwall mining with superhigh-water material backfilling technology has been improved efficiently to prevent the underground disasters and protect the surface ecological environment. Since underground mine pressure behavior and overlying strata movement are influenced by the backfilling strength and backfilling rates, rational design of backfilling parameters is key to realize the green mining of deep buried coal seams. Based on the combination of geological and production conditions of a deep buried coal seam with composite beam theory, the roof fracture distance was analyzed. e software of UDEC was used to simulate the overlying strata movement laws affected by the different backfilling strength and backfilling rates. With the comparative analysis of the vertical displacement movements and the vertical stress distributions, the reasonable filling rate and water volume fraction were determined to be 90% and 95%, respectively. According to the field experiments, the underground dynamic load was low enough for the safe mining, and the village building can be kept in a stable state with the application of the backfilling technology. e research results in a scientific basis for the coordinated development between the safe and efficient mining of deep buried coal resources and protection of the surface ecological environment.

Many dynamic disasters such as coal wall caving and roof falling have happened during longwall face crossing fault. Combined with the coal seam geological conditions in the 1302 longwall face AB coal mine, the paper comprehensively studies the overlying strata movement and the stress evolution laws of stope during superhigh-water material (SHWM) backfilling longwall face across fault by UDEC numerical simulation, theoretical analysis and on-site measurement. The results show that the stress during stable state is affected by the fault will increases abnormally.While the longwall face pass through the fault, the stress will abated and the vertical displacement of the overlying strata of two sides of the fault is significantly different. The fault significant blocks the propagation of stress and development of plastic zone. The superhigh-water material filling mining management roof has good protection effect on the roof when the longwall face encounters fault, which can effectively weaken the blocks effect of fault on stress propagation and plastic zone development. The numerical simulation results are consistent with the field experiments, and the research result provides theoretical basis and technical guidance for safe and efficient production during superhigh-water material backfilling longwall face through the fault.

Many problems exist in the layout of working surfaces in high-gas mines, such as the low efficiency of roadway excavation, difficulties in maintenance after excavation, and serious resource wastes due to difficulties in recovering coal pillars between roadways. Taking the project profile in the west wing mining area of Sihe Coal Mine as the background, this work proposed an optimization plan for the staggered-layer arrangement of roadways. The minimum retained size of the coal pillar was calculated through theoretical analysis, and the plastic failure and deformations of surrounding rocks under different coal pillar sizes and roadway layouts were compared based on finite difference numerical simulations. The reasonable retained size of the coal pillar was determined to be 45 m, and the roadway layout was determined according to the distribution of coal and rock strata in the mining field. The technical measures of base angle pressure relief blasting and strengthening support were proposed to ensure the safety and stability of surrounding rocks of roadways during the service period after the layout plan was optimized. Similar simulation tests were used to study the damage deformations and stress changes of the blasting pressure relief floor. On-site tests showed that the optimized roadway layout greatly improved the recovery rate of coal resources. In addition, surrounding rocks had good stability, and they could be simply repaired or serve the next working surface directly without being repaired. These research results provide a scientific basis and useful reference for similar projects.

Multiple roadways are opened to solve the difficulties in gas control in the high seam working face of high gassy mines, resulting in a large width of coal pillars between roadway groups. Moreover, recovering coal pillars is challenging during stoping, which causes serious resource waste. While the size of coal pillars is optimized, the reasonable horizon layout of roadway groups is performed to ensure a fine recovery rate of coal resources, mine safety, and efficient production. Theoretical analysis was applied to calculate the stress distribution of surrounding rocks around coal pillars based on the engineering practice of the W2302 working face in the Sihe Coal Mine. The MathCAD software Prime 2.0 combined with the on-site measured stress was used to draw the stress distribution under different coal pillar widths, which can derive the stress distribution data of the floor. The vertical stress concentration factors tended to be consistent at 10 m below the coal pillars and about 12 m from the centerline of coal pillars under different coal pillar widths, this area was suitable for the layout of floor rock roadways with a stress concentration factor of about 1. Numerical simulations were used to compare the stress distributions of the roadway floor and the deformation features of surrounding rocks under different coal pillar widths. The coal pillar width was finally determined to be 45 m, which optimized the size of coal pillars. The return air roadways were arranged at 9.8 m below the coal seam combined with the strata distribution on-site. According to the industrial test on-site, the return air roadways were available during the service period, which showed reliable theoretical analysis and simulation results. A reasonable horizon layout of return air roadways can provide a scientific basis and reference for similar projects.

In order to research on the issue of high-pressure gas blasting fracture deeply, a high-pressure gas blasting cracking experimental system was established; the effects of gas pressure and gas volume on the morphology of crack growth were studied; the p-t curve of pressure in the blasting process with time was obtained; and the mechanism of high-pressure gas blasting cracking was analyzed in this paper. The conclusion has shown that the stage of effect of high-pressure gas blasting on the test block includes three stages: the gas jet impact stage, the crack initiation and development stage, and the perforation fracture stage. In the design of gas pressure of 5 MPa, the experimental block only produces one longitudinal main crack. As the gas pressure increases to 7.5 MPa and 10 MPa, besides forming one longitudinal main crack, a transverse main crack is formed with further expanded 4–6 secondary cracks. In the same design of gas pressure regardless of volume size, each pressure variation stage has the same length, and the experimental block of the cracking pressure is basically the same. With the higher design pressure, the cracking pressure and the fracture pressure are higher. In the same design of gas pressure, with the larger gas volume, the fracture pressure required for the experimental block is smaller.