The development and application of a hinged sidewall fault-crossing tunnel model container

To meet the current demand for anti-seismic testing technology in underground engineering in China, a hinged sidewall fault-crossing tunnel dynamic model container has been developed. The structures and operational principles of the model container are introduced, and a concentrated-mass model of soil, hinged sidewall and spring is established. Using the 2-norm deviation of acceleration response as the criterion, the influence of spring stiffness on the boundary effects of the model container was analysed. This analysis provides a process for determining the stiffness of the spring. Finally, large-scale shaking table model tests were conducted using the model container to investigate the impact range of fault interfaces on tunnel structures under strong seismic actions. The results revealed that, the boundary effects of the model container gradually diminish with an increase in the damping ratio of the model soil. With the increase in spring stiffness, the 2-norm deviation between the model soil response and the free-field soil response, as well as the 2-norm deviation between the hinged sidewall response and the model soil response, initially decreases and then increases. The stiffness of boundary spring should be determined based on the minimum 2-norm deviation between the model soil response and the free-field soil response, following the principle of ‘flexible but not rigid’. The results of the shaking table test indicate that the model system can well reproduce the zonal impact characteristics of tunnel near the fault interface. By analysing the overall bending moment and axial force distribution characteristics along the longitudinal direction of the tunnel, the impact range of the fault interface on the tunnel is determined to be 4B (hanging wall) and 5B (fracture zone). The findings enrich the seismic testing technology for tunnels in high-intensity seismic zones in China, providing valuable references for shaking table test in underground engineering.