Numerical investigation on effect of confining pressure on the dynamic deformation of sandstone

Abstract

In deep buried rock engineering, in situ stress is a significant factor affecting the mechanical response of rocks to dynamic loads. This work focuses on the effect of confining pressure on dynamic deformation of rocks. Considering the limitation of observation in laboratory experiments, numerical simulation method is adopted. The numerical model of split Hopkinson pressure bar test system with confining pressure is established in a two-dimensional particle flow code. Dynamic compression tests of sandstone under different confining pressure conditions are then simulated. The axial dynamic compressive deformation, crack evolution, failure modes and dynamic dilation of specimen are obtained. The results indicate that confining pressure has a constraint influence on both axial and transverse deformation of rock. Under the compression of confining pressure, the axial dynamic deformation, and damage degree are weakened while the elasticity of rock may be enhanced. Compared with that without confining pressure, the failure modes of rock specimens are different under the confining pressure. Dynamic dilation of rock specimen is triggered synchronously with the crack initiation. Confining pressure can weaken the dilation, and contraction of rocks may even happen after the dynamic unloading under a high confining pressure, resulting in a secondary damage to rocks. The results can benefit to comprehend the dynamic deformation and failure of deep buried rocks.