Effect of loading rate on the mechanical and seepage characteristics of gas-bearing coal–rock and its mechanical constitutive model

The overall failure of gas-bearing coal–rock composite is the main cause of composite dynamic disasters. Investigating the mechanical-seepage characteristics of coal–rock specimens is the key to understanding the mechanism and minimizing composite dynamic disasters. In this paper, true triaxial mechanical experiments are designed and conducted under different maximum principal stress-loading rates. The mechanical properties, strength characteristics, and energy responses of samples under different loading rates are studied. A damage constitutive model of coal–rock specimens under different true triaxial loading rates is established; the solving methods for micro strength parameters m and F0 are described. The results show that as maximum principal stress-loading rate increases, the bearing capacity of the sample increases, the deformation parameters gradually increase, the degree of energy change increases, and the deformation failure becomes more severe. The model of gas-bearing coal–rock specimens under different true triaxial loading rates is in agreement with the test curves. Our model can provide useful references for predicting the stability of underground gas-bearing coal–rock.