The geological structures of the coal fields in China are complex. With a continuous increase in the mining depth, the coal seams show the characteristics of high gas and low permeability, and the disaster potential for a coal and gas outburst intensifies in the process of coal mining. Gas drainage is one of the primary measures used to prevent and control gas disasters. Effectively improving the permeability of a coal seam requires urgent attention. Currently, the method of loose blasting is used in engineering to enhance the permeability of coal seams. However, the technology of loose blasting easily leads to the poor development of coal fractures or the severe crushing of coal, which will affect the gas drainage. Thus, this paper studied the technology of liquid CO₂ phase-transition fracturing in a coal seam. COMSOL was used to determine the influence radius of the liquid carbon-dioxide phase-transition cracking, which was 13.4 m, and to design the scheme of the borehole. The field test was carried out in the 81,506th working face of the Baode Coal Mine. From the onsite-monitoring data, the results showed that the drainage effect increased by 293.9%, the gas-drainage concentration increased by 242.4%, the permeability coefficient of the coal seam increased by 3–7.75 times, and the permeability enhancement effect was good.

Outburst closed distance coal seam distances are extremely difficult to mine, and are commonly involved in safety accidents in the process of mining. Based on the engineering background of the Wulan Coal Mine at the western margin of the Ordos Basin, this paper presents a theoretical analysis, engineering analogies, and numerical simulations to determine the optimal mining sequence for the Wulan Coal Mine #7, #8, #2, and #3 coal seams. Floor penetration drilling was used to eliminate outbursts in the #7 and #8 coal seams, and gas control in the #2 and #3 coal seams was achieved using ground drilling to pump and release the pressured gas. We established a comprehensive management technology system for gas emissions from the short-distance joint protection layer in the outburst coal seams of Wulan Coal Mine, where pressure relief and drainage were carried out by drilling through the floor and surface drilling pressure relief extraction. Through field tests, the pre-drainage rate of the #2 coal seam in the Wulan Coal Mine was 66.8%, and the pre-drainage rate of the #3 coal seam was 68.1%. This shows that protective layer mining of the #7 and #8 coal seams combined with surface drilling to extract pressure-relief gas can protect the #2 and #3 coal seams.

To reduce the cost of coal mine filling materials, a novel composite cementitious material was developed by utilizing coal-based solid waste materials, including fly ash, desulfurized gypsum, and carbide slag, along with cement and water as raw materials. Initially, a comprehensive analysis of the physical and chemical properties of each raw material was conducted. Subsequently, proportioning tests were systematically carried out using the single-variable method. During these tests, multiple crucial performance indicators were measured. Specifically, the fluidity and bleeding rate of the slurry were evaluated to assess its workability, while the compressive strength and chemically bound water content of the hardened sample were tested to determine its mechanical properties and hydration degree. Through in-depth analysis of the test results, the optimal formulation of the composite cementitious material was determined. In the basic group, the mass ratio of fly ash to desulfurized gypsum was set at 70:30. In the additional group, the carbide slag addition amount accounted for 20% of the total mass, the cement addition amount was 15%, and the water–cement ratio was fixed at 0.65. Under these optimal proportioning conditions, the composite cementitious material exhibited excellent performance: its fluidity ranged from 180 to 220 mm, the bleeding rate within 6 h was less than 5%, and the 28-day compressive strength reached 17.69 MPa. The newly developed composite cementitious material features good fluidity and high strength of the hardened sample, fully meeting the requirements for mine filling materials.

With the increase of mining depth, the gas management problem in coal and gas outburst mine is more prominent. At the same time, gas is used as a clean resource to mine together with coal which is to realize the simultaneous extraction of coal and gas more practical significance. The relation between coal mining and gas extraction is mutually reinforcing and restricting. It is of great theoretical significance and application value to study simultaneous extraction of coal and gas technique optimization. The Qidong Coal Mine of the Wanbei Coal and Electricity Group is a coal and gas outburst mine. The spacing of the coal seam is small, the occurrence conditions are complex, and the mining is difficult. This study used theoretical analysis, numerical simulation, and engineering analogy to investigate the coordinated mining technology of coal and gas in outburst coal seams.