Study on shear characteristics of straight joints of coal under different normal stress and shear rate conditions

The shear mechanical parameters of coal are important parameters for analyzing the deformation and stability of coal. In order to study the shear characteristics of straight joints of coal under different normal stress and shear rate conditions, the shear numerical simulation and laboratory test were carried out to study the influence of normal stress and shear rate on the shear characteristics of straight joints of coal. The results show that the shear strength of joints decreases with the increase of shear rate, and increases with the increase of normal stress. The higher the normal stress, the greater the influence of shear rate on the shear strength of joints. Shear stiffness is positively correlated with normal stress and negatively correlated with shear rate. When the shear rate reaches a certain value, the influence of shear stiffness is not obvious. The increase of shear rate makes the simulated joints more prone to shear slip, which is easy to cause coal and rock dynamic disasters. This phenomenon is more serious in high normal stress.