Shaking Table Test of a Large-Scale Shield Tunnel Based on an Innovative Loading Device: Theory and Validation

The current centrifuge and shaking table test for a shield tunnel is constrained by the equipment available, leading to a low similarity ratio between the test model and an inconsistent relationship between the soil and structure. Hence, the design of a steel frame, composed of steel plates and springs, has been proposed as an innovative loading device for performing shaking table experiments on large-scale shield tunnels. The proposed loading device, inspired by the response displacement method, incorporates the steel frame to provide support for the tunnel model and transfer the seismic loading from the shaking table, while the springs serve as a representation of the soil-tunnel interaction. In order to validate the accuracy and effectiveness of the loading device, the device, and tunnel are simplified as Euler-Bernoulli beams and linked together with springs to establish an analytical model, and the high-order partial differential equation of the beam is solved to derive analytical solutions for the device and the tunnel. Furthermore, results from the numerical analysis and geotechnical box test on a shaking table system have also been obtained. Based on these results, the loading device is proven to be an effective method of applying seismic loading to the tunnel while maintaining its stability. With the use of the loading device, the shaking table test for a large-scale shield tunnel could be successfully executed, resolving the issue of mismatched similarity between the soil and tunnel model.