A study of the dynamic properties and constitutive model of granite under active confining pressures

In order to study the dynamic characteristics and constitutive behavior of granite under different confining pressures and different strain rates, experimental tests were conducted by using the improved Split Hopkinson Pressure Bar (SHPB), and a damage statistical theory was introduced into the Poynting model. The constitutive model and the experimental data were fitted and analyzed, and then the influence of each parameter in the model on the stress-strain curve was discussed. The results show that the confining pressure and the strain rate can enhance the compressive strength of the granite, both of which are positively correlated with the dynamic increase factor of the specimen, and the presence of confining pressure increases the plastic property of the rock specimen and a plastic yield platform appears on the stress-strain curve. The elastic modulus of the specimen under the active confining pressure is improved, but generally there is no obvious rate effect and confining pressure effect. The predicted results of this model are in good agreement with the measured stress-strain curves of the specimen under different confining pressures.