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Coalbed methane (CBM) content is a crucial parameter for CBM exploitation and disaster prevention, with accurate gas loss calculation being essential for improving measurement precision. To investigate the physical response to gas loss and quantify the impact and interrelation of various factors, this study developed a comprehensive model incorporating the effects of gas diffusion, temperature, and pressure effects on porosity and coal deformation. By utilizing the OpenFOAM platform and C++ for numerical solution development and establishing an experimental system for gas loss measurement, the model's reliability was confirmed. The new model demonstrates an 8.56% average error, representing a significant improvement over traditional methods, with error reductions of 26.59% and 18.31% compared to the square root of time and power function methods, respectively. The hierarchy of gas loss is determined to be gas flow > gas-coal deformation coupling > gas-temperature coupling > gas-coal deformation-temperature coupling. Average diffusion contributions are identified as 41.43% from surface diffusion, 30.71% from Knudsen diffusion, and 27.86% from viscous flow. The factors affecting gas loss, in decreasing order of impact, are adsorption equilibrium pressure, temperature, porosity, moisture, and adsorption constants. These findings provide theoretical support for enhancing gas content measurement accuracy and techniques, significantly benefiting CBM extraction and mine safety. [ABSTRACT FROM AUTHOR]

A three-dimensional numerical model of heading face was established based on Guoerzhuang Coal Mine in Handan, Hebei Province. The effects of different coal seam depths, driving speed and coal mechanical strength on the coal wall sudden extrusion are analyzed by using 3DEC discrete element simulation software, and the orthogonal experiment method is used to rank the influencing factors according to the degree of importance. The results show that there is a positive linear correlation between the maximum horizontal displacement of the fixed point on the heading face and the change of the buried depth, and the direction of the coal wall extrusion displacement is close to the central axis of the roadway, and the horizontal displacement is obviously larger than the vertical displacement. Under the condition of the buried depth of 600 to 1 000 meters, the width of stress concentration area of working face is about 10 meters, and the position of the stress peak is about 5 meters from the working face. The factors affecting the coal wall sudden extrusion in heading face are in the following order: buried depth of coal seam > driving speed > mechanical strength of coal body. The research results provide a reference for further understanding of the coal wall sudden extrusion and preventive measures.

In China, safety policies interfere with the occurrence of work accidents in the form of guidance and restrictions. In this study, the impact of types of safety policies on work accident prevention is quantitatively analyzed. Based on a statistical analysis of China's safety policies and work-related accidents from 2000 to 2020, the following four policy indexes that reflect the impact of safety policies are identified: the stringency level of the policy; the scope; its technical content; and its industrial target. A vector autoregressive model (VAR) is used, and a dynamic analysis of the model is conducted with an impulse response function. The model's degree of fit is 92.9%, the number of deaths and the number of safety policies are linearly related, and the relative error between the fitted values and the real values is approximately 5%. The negative correlation between the death rate per 100 million yuan and the stringency level, scope, technical content, and industrial targets of safety policies is first weak, then strengthened, and then weakens again over time. This study finds that the importance of safety policy indicators is different; especially, the strict safety policy has a long-term negative impact on mortality. For developing countries such as China, where the safety policy system is not yet perfect, increasing the number and implementation of safety policies can significantly improve the situation of production safety. [ABSTRACT FROM AUTHOR]