Abstract: The combined finite-discrete element method (FDEM) numerical simulation method was used to study the prediction of the large deformation and its control of the weak surrounding rock in the deep tunnel under high in-situ stress condition. Firstly, the basic principle of the FDEM was introduced. Then the uniaxial compression, Brazilian disc and triaxial compression simulation tests were compared with laboratory experiments to calibrate the input parameters. Finally, the large deformation of the surrounding rock was simulated after deep tunnel excavation under high in-situ stress conditions; based on the solid modelling method, the reinforcement of the tunnel by using the method of rockbolt-shotcrete-grouting was simulated. The results show that the large deformation of the tunnel is primarily caused by the rupture and fragmentation of the surrounding rock. The shallow part is mainly a tensile failure, and the deep part is a shear failure. The shear failure angle is consistent with that of the uniaxial compression test result, 58°, the maximum crack propagation depth is 10.6 m, and the maximum surface convergence is 20.7 cm. The reinforcement method of rockbolt-shotcrete and rockbolt-shotcrete-grouting can effectively control the deformation of the surrounding rock, inhibiting the crack extension range (reduced to 5.8 m, 5.1 m). Besides, the convergence of the surrounding rock surface is greatly reduced (5.1 cm, 4.2 cm).

Key words: FDEM numerical simulation, deep tunnel, fracture and extraction large deformation；rockbolt-shotcrete support, grouting reinforcement