Study on pore structure and gas adsorption characteristics of coals with different burst liability

With the increase of mining depth, the features of high geopathic stress, low permeability and strong disturbance of coal seams gradually appear, and the form of underground disasters becomes more and more complicated, among which impact ground pressure and gas protrusion is the most important form of composite disaster manifestation. In order to study the intrinsic connection between microscopic pore structure and gas adsorption of different impact-prone coal samples, pore co-testing of different impact-prone coal samples was carried out by utilizing gas isothermal adsorption experiments and the idea of advantageous aperture segments of different pore testing experiments. The experimental results show that: the microstructural characteristics of the coal body can reflect the degree of macroscopic tectonic damage and the nature of the stress action in the coal seam to a certain extent, and the coal samples with less pore content have stronger impact tendency; the Wangzhuang coal sample is a strong impact tendency coal sample, with the least pore content, a dense structure, stronger hardness and brittleness, and more strain energy accumulated in the process of loading, and the high-stress environment leads to a larger number of micropores in the coal samples; the Tianchi coal sample is a no-impact coal sample, with large pores, and its porousness is larger than that in the coal samples. Tianchi coal sample is a non-impacted coal sample, which has a higher proportion of large pores and the pore content of the coal sample increases most obviously during the crushing and pulverization process. Further, through the gas isothermal adsorption experiments, it was found that under the same conditions, the gas adsorption amount of the Yuwu coal sample was the largest, the Tianchi coal sample was the second largest and the Wangzhuang coal sample was the smallest, and the complex pore structure and poor pore connectivity were more favorable to the gas storage, and the strong impact tendency of the Wangzhuang coal sample had stronger pore connectivity, which was favorable to the transportation and release of the gas. The coal body of Yuwu coal sample and Tianchi coal sample has high degree of fragmentation, and the channels between the pores are narrowed or blocked, forming part of the small roar channel connecting the large pores and closed pores, and the more concentrated the distribution of pore sizes, the stronger the non-homogeneity, the higher the pore complexity, and the worse the connectivity, and the growth rate of gas adsorption with the reduction of the size of the coal sample is more rapid. Meanwhile, the correlation between microporous structural parameters and gas adsorption was the highest, followed by mesopore, while macroporous parameters had no obvious correlation with adsorption, and the correlation between specific surface area and adsorption was generally higher than that of pore volume, which indicated that the pore surface was the main place where gas adsorption occurred. The multiple fractal dimension eigenvalues were further calculated based on the pore size distribution of the whole pore, and the amount of limiting adsorption could also be characterized by the multiple fractal dimension eigenvalues, and the influence of fractal parameters on gas adsorption amount varied among different coal samples, and the adsorption amount of the Yuwu and Tianchi coal samples showed a positive correlation with α, and a negative correlation with H, whereas the value domain maximum value of f(α)max had no obvious correlation.