Study on Gas Control Methods Optimization for Mining Safety

Abstract

Effective gas control is of significance for safe efficient coal mining in Haizi Coal Mine and other mines with similar geological conditions. This study concentrates on gas control theories and techniques in multiple coal seams of Haizi Coal Mine (No. 7, No. 8, No. 9, and No. 10 coal seam from top to bottom). To minimize risk of high gas emission and outburst hazard, No. 10 seam was mined first as a protective seam prior to the mining of its overlying outburst-prone No. 7, No. 8, and No. 9 seam. Four gas drainage measures were determined for gas control, including cross-measure boreholes into overlying coal seams, surface goaf wells, roof boreholes, and roof gas drainage roadway. These gas control measures, if implemented through entire coal seam extraction, would be possibly uneconomic. An investigation was undertaken to analyze effects of those four measures on gas emission, methane concentration, and gas drainage quantity in No. 2 1024 mining panel of No. 10 seam. Results indicate that the highly expensive gas drainage measure of a roof roadway has poor drainage performance and could be effectively replaced by roof boreholes. When adopting the optimized combination of gas drainage measures, drainage efficiency of No. 7 seam, No. 8 seam, and No. 9 seam could reach 58.64% and decrease gas pressure to be below 0.74 MPa. Outcomes of this study could provide beneficial guidance not only for gas drainage design optimization in Haizi Coal Mine but also for other multiple-seam mines with similar mining and geological conditions, for increasing gas drainage efficiency and guaranteeing mining safety.

Optimization of the Layer Location of Extraction Wells Based on the Unpressurized Gas Transport Law

“…When it occurs, hundreds of tons of coal and rock are suddenly thrown out and carrying a large amount of gas can cause underground workers to be impacted, buried, suffocated, and injured. Also the equipment and facilities were damaged and even caused gas and coal dust explosions. − Protective layer mining is the most effective way to prevent the danger of coal and gas outbursts. − This process is achieved by mining the adjacent coal seam (i.e., the protected seam) before the outburst coal seam (i.e., the protected seam). , After the protective layer is mined, the pressure of the adjacent coal seam is relieved and cracks are generated, which changes the stress balance state of the original rock, increases the permeability of the coal seam, , and releases gas in the protected layer. The use of surface mining wells for coalbed methane extraction has the significant advantages of high drainage concentration and large flow. − The entire construction process is located on the ground and does not affect the coal production.…”

“… 6 − 9 Protective layer mining is the most effective way to prevent the danger of coal and gas outbursts. 10 − 12 This process is achieved by mining the adjacent coal seam (i.e., the protected seam) before the outburst coal seam (i.e., the protected seam). 13 , 14 After the protective layer is mined, the pressure of the adjacent coal seam is relieved and cracks are generated, which changes the stress balance state of the original rock, increases the permeability of the coal seam, 15 , 16 and releases gas in the protected layer.…”

Study of Reasonable Grouting Pressure in the Process of Measuring Coal Seam Gas Pressure and Application

“…In recent years, with the deepening of mining depth and the increasing complexity of coal mining, the deep coal seams have generally exhibited high ground stress, high gas content, and high gas pressure characteristics. Gas disasters have become one of the factors seriously affecting mine safety production. , Gas pressure is an important indicator for preventing gas disasters, which directly reflects the gas content in coal seams and the potential danger level of coal and gas outbursts. − However, accurate measurement of coal seam gas pressure is very difficult under complex production conditions. , According to the long-term experience in coal seam gas pressure measurement, the success rate can reach as high as 70% . Low success rate and inaccuracy of measurement will increase the danger in production, which limits the production speed of the mine.…”

“…Gas disasters have become one of the factors seriously affecting mine safety production. 2 , 3 Gas pressure is an important indicator for preventing gas disasters, which directly reflects the gas content in coal seams and the potential danger level of coal and gas outbursts. 4 − 6 However, accurate measurement of coal seam gas pressure is very difficult under complex production conditions.…”

Morphological characteristics and permeability evolution of deep mine gas drainage boreholes

“…Unloading is a deep mine gas disaster management technology. Hydraulic punching is a tectonic coal unloading extraction gas effective technique, and its role is mainly reflected in the following three aspects (Wu et al, 2002;Wang et al, 2013;Jiang et al, 2018;Liu and Liu, 2019;He et al, 2021): 1) high-pressure water is used to break the coal body, forming a certain range of pressure relief area around the hole, in which the permeability increases substantially, so as to achieves the purpose of gas extraction; 2) wetting coal reduces its elastic potential energy; and 3) water lock reduces gas desorption speed. The pore shape is a key influencing factor in the design of gas drainage.…”