Study on the calculation method for rockfall impact and energy dissipation effect of energy dissipation shed tunnel

Based on the basic principle of structural dynamics and the dynamic characteristics of shed tunnel being impacted by rockfall, and also considering the elasticity and viscosity of shed tunnel and energy dissipation bearing, the calculation formula for time-varying rockfall impact force was deduced. According to the structural characteristics and stress conditions of energy dissipation shed tunnel, the vibration model of energy dissipation shed tunnel was established and the formula for calculating the stiffness coefficient of energy dissipation shed tunnel was derived, and then the computational formula for rockfall impact force of energy dissipation shed tunnel was obtained. Taking the shed tunnels of the national highway G319 and Feng-Sha Railway for example, the energy dissipation effect of energy dissipation shed tunnel was analyzed. The results show that, after energy dissipation shed tunnel being adopted, rockfall impact force decreases about 50%, the maximum bending moment of the crossbeam, the upper and lower side of longitudinal beam decreases more than 15%, 17.3% and 6.9% respectively. It shows that the effect of energy dissipation for energy dissipation shed tunnel is obvious and the bearing capacity of shed tunnel has been greatly increased.