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Study of triaxial compression mechanical properties and pore-fracture characteristics of coal rocks in the Yili Basin, Xinjiang

Shen Cheng, Yue Ling, Liu Yang

Journal of Theoretical and Applied Mechanics

2023

Vol. 61 nr 2

207--218

Compressive mechanical properties and pore-fissure characteristics of coal rock specimens from three stably developed coal seams M1, M8 and M12 in the Xinjiang Yili Basin were investigated in detail by a series of tests. The results show that the compressive mechanical properties of coal rocks in the Yili Basin are significantly affected by the confining pressure. The peak axial stress increases and the peak modulus of elasticity decreases as the confining pressure increases. The peak axial strain increases and then remains constant, while the peak circumferential strain and peak volumetric strain increase and then decrease. The confining pressure has almost no effect on Poisson’s ratio of the coal rock specimens. In addition, electron microscopy tests show that the microscopic fraction of the coal rock specimens is predominantly vitrinite, accounting for 83.1%-89.2%, while the percentage of the inertinite group is relatively small, at 10.3%-16.1%. The throat radius of the coal rock is mainly concentrated around 1-2μm, while the pore radius of the coal rock is between 150-200μm. The coal rock has an overall fine throat and low permeability, and the coal rock in the Yili Basin of Xinjiang is a typical low-permeability coal rock.

Study on the effect of coal microscopic pore structure to its spontaneous combustion tendency

Dong Xianwei, Li Gaojing, Dong Xuanmeng, Wang Fusheng

Journal of Sustainable Mining

2022

Vol. 21, iss. 2

120--127

Coal is a porous medium. Due to the large number of pores in coal and the pore size on its surface, usually ranging from millimeter to nanometer, it is difficult to measure and analyze the microscopic pore structure of coal. In order to investigate the effect of the microscopic pore structure of coal on its spontaneous combustion tendency, coal samples from different coal mines of the Kailuan Group were selected as the research objects, and the data of the microscopic pore distribution of three different coal samples were measured by using mercury injection apparatus. The regression analysis of microscopic pore data of coal samples obtained in the mercury injection experiment shows that the correlation coefficients of the regression curves are all greater than 0.94 and the fitting degree is good, indicating that there is a good correlation between the pressure, mercury intake and pore size of the coal samples, indicating that the fractal dimension of pore distribution is very effective. The fractal dimension is generally between 2 and 3, indicating that the microscopic pores of coal samples have good fractal characteristics and meet the fractal theory to describe the distribution characteristics of microscopic pores in porous media. Through the simulation system of natural combustion of coal, the simulation experiment of temperature rise oxidation of different coal samples (gas coal, fat coal, and coke coal) was carried out, and the curve of the concentration of gas products CO and CO2 in the process of temperature rise and oxidation of coal samples was drawn in the experiment. The experimental results show the relationship between the distribution structure of coal pores and its spontaneous combustion tendency, and the coal with a good distribution dimension has a stronger combustion tendency.