Abstract: Based on the size of cavern section and the development characteristics of discontinuities, the preliminary bolt-shotcrete parameters were obtained for specific Q-value cavern surrounding rock using Q system. A water-sealed liquefied petroleum gas rock cavern in Shandong province was taken as research background. In view of the distribution characteristics of in-situ stress, the relationship between Q value and equivalent mechanical parameters of rock mass were established via GSI and Hoek-Brown failure criterion. Using 3DEC software, the preliminary bolt-shotcrete parameters were checked respectively from the aspects of continuous and discontinuous surrounding rocks using 3DEC software, respectively. Moreover, the security safety of support structure was evaluated based on the overloading safety factor law. Results show that: 1) when surrounding rock is continuous, the bolt-shotcrete support has an obvious effect on the displacement of surrounding rock, and the minimum safety factor of bolt is 2.75,while that of the shotcrete layer is 1.25, which indicate that the bolt-shotcrete parameters are safe and reasonable; 2) when surrounding rock is discontinuous, the bolt-shotcrete support fails due to the local unstability of blocks; 3) since the support object of Q system does not include local unstability block, so it is necessary to adopt discrete element numerical simulation for the support design, and it is important to discriminate local instability problems during construction stage.

Key words: underground rock cavern, Q system, discrete element simulation, bolt-shotcrete support, equivalent mechanical parameters of rock mass