Dynamic failure evolution law and damage constitutive model of coal rock under impact load

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.