Determination of Johnson-Holmquist-Ⅱ Constitutive Model Parameters and Study on Tunnel Surrounding Rock Damage under Coupling of Dynamic and Static Loads

In order to study the deformation and damage of tunnel surrounding rocks under the coupling action of static and dynamic stresses, a tunnel model under the coupling action of ground stresses and blasting loads is established. Firstly, the JH2 constitutive parameters of surrounding rock are deduced based on the on-site monitoring data of Wenbishan tunnel and the wave velocity of the rock mass. According to the surrounding rock grade, combined with the known parameters and wave equation, a simple method to determine the JH2 constitutive parameters is given, and the damage model of the surrounding rock is established by embedding a subprogram into ABAQUS. In order to make the simulation model closer to the reality, this research first balances the ground stress, takes the soil state at this time as the initial stress state of the blasting simulation, then using the equivalent blasting load method to simulate the tunnel blasting, so as to realize the blasting simulation for large-scale geotechnical engineering under the coupling of static and dynamic stresses on a macro level. The simulation model not only considers the blasting effect on the working face, but also focuses on the impact of blasting on the surrounding rock of the tunnel. The results show that the initial ground stress plays a significant role in the damage and deformation of the surrounding rock during tunnel excavation. The existence of the initial ground stress induces damage propagation. The greater the ground stress is, the greater the damage is. The maximum damage depth of the arch bottom in vertical direction is 2.2 m. At the same footage, the smaller the ground stress is, the greater the deformation is. The maximum deformation of 11.7mm is produced at the arch crown near the excavation face. The horizontal convergence deformation of the surrounding rock is different. The upper part is away from the tunnel, and the lower part points to the tunnel. In addition, the surrounding rock at the boundary between the upper and lower benches is subject to shear load. The damage and deformation of the surrounding rock are closely related to the actual project.