To explore the strain rate effect of deformation and failure of impact prone coal rock, uniaxial compression tests and triaxial compression tests with different strain rates were carried out. The mechanical properties and impact tendency of impact-prone coal rock were studied, and the energy evolution law and pre-peak energy self-promotion-inhibition mechanism of impact-prone coal rock were obtained. The results show that with the increase of strain rate, the peak strength of coal rock under uniaxial compression decreases gradually, and the peak strength of coal rock under triaxial compression increases first and then decreases, and the impact tendency of coal rock increases first and then decreases. The energy evolution of coal rock under uniaxial compression is mainly divided into four stages: initial energy damage, energy hardening, energy softening and failure. With the increase of strain rate, the total energy and elasticity at the peak point of coal rock under uniaxial compression decrease gradually, and the total energy, elastic energy and dissipation energy at the peak point under triaxial compression increase first and then decrease. The elastic energy promotion coefficient of impact-prone coal rock is much larger than the inhibition coefficient, and the increase of strain rate will promote the generation of elastic energy inside coal rock. The research results can provide reference for the prevention and early warning of dynamic disasters of coal and rock mass with impact tendency.

Joints and fractures lead to different failure mechanisms in rock masses under different environments. The mechanical properties and failure mechanisms of rocks with fissures are key problems in rock mass engineering. Parallel double-fracture quasi-sandstone specimens with different dip angles were prepared and subjected to triaxial compression tests after a single freeze-thaw cycle. Pore development, crack propagation, damage evolution, and failure characteristics were analysed. Combined with the strength distribution theory of microelements and the static elastic modulus theory, a damage constitutive model of double-fracture quasi-sandstone under freeze-thaw cycles and loads was established. This study explored the pore development, fracture propagation, damage evolution, and failure characteristics of fractured sandstone after thawing. The results showed that the compression wave velocity of the thawed specimens decreased, the nuclear magnetic resonance (NMR) T₂ curve shifted to the right, and the frost heave force promoted the development of the internal porosity in the specimens. With an increase in the crack dip angle, peak stress, expansion stress, cohesion and internal friction angle, the specimen showed a ‘U’ shaped change trend, compression cracks, and rock bridge penetration rate after failure decreased, and mixed failure of tension and shear gradually changed into shear failure. When the dip angles were 30° and 60°, the double fractured quasi-sandstone had larger total damage and more obvious brittle failure characteristics.

To explore the dynamic characteristics and damage evolution laws of deep coal rock under impact loads, the dynamic load response laws of coal rock at different strain rates under high-frequency dynamic loads were studied using the Split Hopkinson pressure bar test device, and the deformation and failure processes of coal rock were analyzed in combination with a high-speed photography acquisition system. The dynamic impact results of coal rock under different impact loads were calculated using the “Three-wave method”. The test results show that the peak stress and strain rate have an approximately linear increasing relationship, and the peak strain and strain rate have a logarithmic increasing relationship. With the increase of strain rate, the dynamic elastic modulus generally shows a logarithmic increasing trend. Under high-frequency dynamic loads, coal rock mainly show a tensile failure mode. Based on the Weibull distribution function and by introducing the damage variable, the Z-W-T constitutive model was improved and optimized. On this basis, a dynamic damage constitutive model considering the impact tendency index was established. The model is in good agreement with the test results and can well describe the damage evolution laws and dynamic mechanical behaviors of coal rock under impact loads, providing a basic research for the mining of deep coal resources under the influence of impact dynamic loads.