Impact mechanical characteristics and damage evolution model of granite

By using the split Hopkinson pressure bar (SHPB),the impact test at different stress wavelengths(0． 8-2． 0 m) and strain rates (20-120 s-1 ) was carried on to study the dynamic mechanical properties and damage accumula- tion evolution law of granite. Test results show that the dynamic compressive strength and strain rate of granite have significant correlation,whose relationship is linear positive correlation and the relationship between the factor of dy- namic compressive strength and the natural logarithm of strain rate is linear positive correlation. The relationship be- tween peak strain and strain rate is linear positive correlation,and the increase of wavelengths makes the level of peak strain uplift overall. The multiple-impacts test indicates that at the same wavelength,the cumulative damage of granite shows exponential increasing form with the increase of strain rate;when keeping the increase of strain rate constant and increasing the stress wavelength,the damage accumulation effect of granite is intensified and still shows exponential in- creasing form;under the effect of multiple impacts,the damage development trend of granite is similar overall,but the increasing rate is accelerating. Thereby the damage evolution model was established based on the exponential function, and the physical meaning of parameters in the model was determined. The model can reflect the effect of the wave pa- rameters and multiple impacts. The validity of the model and the physical meaning of the parameters were verified by test.