Abstract：After the introducing of rock structure model with nonuniformities，the influence of stress concentration on the failure mode of rock are analyzed based on stress concentrates during deformation on nonuniformities. In order to investigate the behavior of rock in depth，three cases of stress conditions are studied. They are unconfined uniaxial compression，the loading and unloading of hydrostatic stressed rock in axial direction. Analysis shows that both in loading and unloading process，tension stresses appear in rock. In the loading case，the tension stress may result in splitting which is parallel to the loading direction. In the unloading case，the tension stress is parallel to the unloading direction. The main influential factors of tension stress are physical parameters of nonuniformities，initial stress of rock and unloading speed. The influence of unloading duration and initial stress on the stress concentrations of nonuniformities is analyzed in detail. Results show that the shorter the unloading duration is，the greater the stress concentration is. And if the scale of nonuniformities is large enough，the local tension stress will be approximately proportional to the initial stress. According to the expressions of local tension stress，rock mass will be destructed by tension during rapid unloading in deep rock engineering.
