Deformation and damage dynamic characteristics of coal–rock materials in deep coal mines

The deformation and damage characteristics of surrounding rock grow gradually with the increase of mining depth, and the mechanical behavior and damage mechanism of coal–rock materials vary greatly. In order to reveal the deformation and damage dynamic characteristics of coal–rock materials in deep mines, the macroscopic deformation characteristics of coal, rock, and concrete samples under uniaxial compression were studied. The macroscopic deformation amount, velocity, and acceleration of different samples were analyzed. The coal and rock samples exhibit regular dynamic characteristics before they lose stability and fail. The axial strain response of the coal samples changes significantly during the compact and elastic deformation stages. Besides, the relationship between the surface damage and the macroscopic deformation of sample was studied by means of visualization and image processing. The macroscopic deformation index of coal–rock materials changes significantly before and after the destabilization and failure. Based on the deformation and failure dynamic characteristics of coal and rock, the evolution rule of deformation critical values was taken as the deformation and destruction stages, which revealed the dynamic characteristics during the deformation and failure process of coal–rock materials in deep mines. The deformation critical values can be used to realize early warning of deformation and fracture of coal and rock materials in deep mines.