Coalbed gas content is the most important parameter for forecasting and preventing the occurrence of coal and gas outburst. However, existing methods have difficulty obtaining the coalbed gas content accurately. In this study, a numerical calculation model for the rapid estimation of coal seam gas content was established based on the characteristic values of gas desorption at specific exposure times. Combined with technical verification, a new method which avoids the calculation of gas loss for the rapid estimation of gas content in the coal seam was investigated. Study results show that the balanced adsorption gas pressure and coal gas desorption characteristic coefficient (K_t) satisfy the exponential equation, and the gas content and K_t are linear equations. The correlation coefficient of the fitting equation gradually decreases as the exposure time of the coal sample increases. Using the new method to measure and calculate the gas content of coal samples at two different working faces of the Lubanshan North mine (LBS), the deviation of the calculated coal sample gas content ranged from 0.32% to 8.84%, with an average of only 4.49%. Therefore, the new method meets the needs of field engineering technology.

The zoning of the coal seam gas is zonal, which has a significant impact on the prominent prediction indicators, resulting in different prediction results for the same prominent prediction indicators in the same coal seam soft and hard coal. In this paper, the hard coal and soft coal in the coal seam are highlighted. The adsorption and desorption rules of the soft coal and hard coal in the outburst coal seam and its influence on the sensitivity of the outstanding prediction index are studied. The results show that: (1) the initial desorption of soft coal is larger than that of hard coal; (2) the outstanding prediction index has an exponential function relationship with gas pressure; (3) the sensitivity of prediction indicators is different. And concluded that: (1) the initial desorption rate of soft coal is faster than that of hard coal; (2) the outburst prediction index K₁ and Δh₂ increase with the increase of gas adsorption equilibrium pressure; (3) outburst prediction index K₁ is more reliable than Δh₂.

The prediction of dangerous hazards in working faces is an important link to prevent coal and gas outbursts. Improving the accuracy of predictive indicators is of great significance for reducing the phenomenon of being prominently below the critical value and ensuring safe production. The fixed-size desorption index K₁ is one of the important indicators for coal face and gas outburst prediction. Based on the diffusion theory and the physical meaning of fixed-size coal samples, the mathematical expression of K₁ is established by the self-developed high/low temperature pressure swing adsorption-desorption experimental system. According to the equation, the effects of gas pressure, loss time, coal particle size and diffusion coefficient on K₁ are studied. The results show that the K₁ index is logarithmically related to the gas pressure. Under the same conditions, the longer the loss time is, the smaller the measured K₁ is, and the smaller the particle sizes of the drill cuttings are, the more notable the performance is; the diffusion coefficient represents the ability of gas to bypass micropores and the coal matrix. The greater the ability to bypass the matrix is, the larger the diffusion coefficient under the same conditions is, and the larger K₁ is; the coal particle size has a greater influence on K₁, and the smaller the size is, the more likely it is that the phenomenon of being prominently below the critical value occurs. Therefore, the particle size composition of coal during on-site measurements is crucial for obtaining the true K₁ and the exact critical values.

The permeability characteristics of gas‐containing coal under different radial stress, different axial stress, and gas pressure were studied by orthogonal experiments, using a self‐developed three‐axis servo fluid infiltration system with a gas‐solid coupling of gas‐containing coal, on the basis of a single‐factor influence on the permeability of gas‐containing coal. By considering the effective stress, three kinds of relationships between permeability and radial stress, permeability and axial stress, as well as permeability and gas pressure were established. The results show that radial stress, axial stress, and gas pressure have a great influence on the permeability characteristics of gas‐containing coal: (a) The influence of radial stress on gas permeability is significant, whereas the influence of axial stress is negligible. The degree of influence of radial stress, gas pressure, and axial stress on the permeability decreases in turn; (b) The permeability decreases following a power function with the increase of the radial stress; (c) The permeability gradually increases with the increase of axial stress. With the increase of axial stress, the permeability increases following a power function; (d) The increase in gas pressure will reduce the effective stress on the coal, and the number of pores and cracks inside the coal body will decrease. This will increase the effective seepage flow and gas flow rate of the gas and eventually lead to the increase of coal permeability. There is a quadratic function relationship between the permeability and gas pressure.

Hydraulic methods have been extensively employed to improve the production rate of commercially viable coalbed methane and prevent potential mining disasters resulting from the production of this methane by increasing the permeability of coal seams. In this paper, an experimental system with a stirrer was utilized to study the effects of water injection on the gas desorption characteristics of coal seams. Pressure‐released desorption values and total gas desorption values under conditions of different adsorption equilibrium pressures and water contents were determined. The results show that both the free gas and the adsorbed gas could be replaced by the injected water, causing the system pressure to increase significantly. When releasing the system pressure, the gas desorption value of the water‐injected coal sample was reduced. After water injection, the total desorption value of the coal was increased. Thus, water injection could help to promote coal gas desorption.