LAUSR

Using a self-researched micro-structure shear testing device for gas-containing coal, this paper studies the characteristics of micro-cracks forming, expanding, and ultimately destroying the sample at different shear rates and then discusses the macro-failure characteristics and the evolution law of micro-cracks in the gas-containing coal at different shear rates. The results show that the shear strength decreases with an increasing shear rate, and the relation between them is a logarithmic relation; the cracking tips are in the upper and lower parts of the coal, and a fine crack appears in the sample when the shear stress is 10% of the maximum shearing stress, while the cracks fully penetrate when the shear stress is 70% of the max; finally, macroscopic damage forms when the shear stress equals the maximum amount. The angle between the direction of the lower cracks and the shear increases with an increasing shear rate; the main fracture of the gas-containing coal is around the coal particles, the fracture surface of the coal is injustice, and the fracture surface roughness becomes worse with an increase in the shear rate. With an increasing shear rate, the gas-containing coal’s cranny ratio and crack fractal dimension increases, the degree of damage increases, and the carrying capacity decreases, which leads to a lower stability and a higher tendency for coal and gas outbursts.