Abstract：When the underground caverns of brittle surrounding rock located in high geostress area are excavated，the longitudinal splitting cracks always are found and brittle cracks will appear. The splitting cracks will evolve into large parallel splitting crack groups together with intense deformation such as rockburst，and thus will endanger the safety of engineering. From the perforation mechanism of splitting cracks，the criterion of splitting failure is established based on analysis of stress intensity factor of fracture mechanics and the spread process of splitting cracks. Then the stress state and the splitting range of surrounding rock are evaluated. The splitting rock is regarded as thin plates. According to G. R. Kirchoff ¢s thin plate theory，the applicability of thin plate is verified. The stress and displacement are resolved by elastic thin plate under the condition of basic hypothesis and geostress. The resolution calculations of stress and displacement are settled in theory. Taking Pubugou hydropower station as an engineering case，the criterion is programmed into FISH language and embedded into FALC3D. The splitting failure range is confirmed；and the critical stress and the maximum displacement are calculated by the resolution formulae. The results agree well with the numerical results. It indicates that the splitting criterion can predict the splitting failure range；and the stress and displacement can also be calculated with thin plate mechanical method rather precisely. The method can offer references to evaluating stability of underground engineering and support design with high geostress.
