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A self-developed gas desorption and diffusion experimental system was used to conduct isothermal methane gas desorption and diffusion experiments, and the pore structure of coal samples was analyzed. A new mathematical model for gas diffusion in coal particles was established, and the diffusion coefficient was calculated using the new model. The influences of particle size and the adsorption equilibrium pressure on the methane gas diffusion rate, gas diffusion quantity, and diffusion coefficient were analyzed and discussed. The results show that under different adsorption equilibrium pressures and different particle sizes, the diffusion rate and quantity vary substantially. The larger the particle size, the slower the initial gas diffusion rate and the longer the time required to reach desorption equilibrium. The larger the adsorption pressure, the greater the initial gas diffusion rate and the larger the quantity of diffusion gas accumulated. However, the coal particle size has little influence on the amount of gas diffusion. It was found that as the particle size decreases, the diffusion coefficient in the first diffusion phase is significantly reduced, which decays with a negative exponential function over time. However, the adsorption equilibrium pressure has no obvious influence on the diffusion coefficient. In addition, the methane gas diffusion process was divided into three phases, namely, phase I, rapid diffusion phase (0-10 min); phase II, slow diffusion phase (10-100 min); and phase III, smooth diffusion phase (100 min); and the diffusion mechanism corresponding to each phase was analyzed. These research results provide a theoretical and practical reference value for gas prevention and control in coal mines. Keywords Gas desorption and diffusion . Mathematical model . Coal particle size . Adsorption equilibrium pressure . Diffusion coefficient . Three phases of gas diffusion This article is part of the Topical Collection on Mine Safety Science and Engineering Electronic supplementary material The online version of this article (

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Coal and gas outburst is a kind of complex dynamic disaster with short duration and strong explosiveness, and the modes and strength of the outburst are determined by the in situ stress, gas pressure, and physical and mechanical properties of the coal mass. In this paper, the status quo of research on the mechanism of coal and gas outburst in China is described from three aspects: the controlling effect of single factor, the controlling effect of multi-factor, and new understandings of the outburst mechanism in recent years. Firstly, controlling factors of coal and gas outburst are classified for an in-depth analysis of the main factors of the same type of disasters, and the research progress and new understandings of the mechanism of coal and gas outburst are systematically sorted out. Secondly, the influencing factors of the strength coal mass are analyzed, and the related issues of coal mass strength on coal and gas outburst disaster mechanism are discussed. The results show that the stages of incubation, occurrence, development, and stop on coal and gas outburst are affected by the coupling effects of in situ stress field, gas pressure field, and seepage field, and the coal strength becomes an important factor affecting outburst strength under the same in situ stress and gas pressure. Therefore, the scientific and reasonable improvement methods of such similar simulation experiment devices are proposed according to the existing experimental methods and devices, which is of great significance to provide ideas for the continuous transferring to deep mining and preventing coal and gas outburst in China in the future.