Design and Analysis of Shaking Table Test on Shield Tunnel-shaft Junction

A shaking table test was carried out to investigate the seismic response of the shield tunnel-shaft junction. The similitude ratio of geometry was 1: 60 and the shield tunnel model was made of polyethylene. However, the shaft model was fabricated by 3D print technology as well as nylon. The model soil was a combination of saw dust and dry sand with the mass ratio of 1: 2.5. The rigid model container was 10.0 m long, 4.5 m wide and 1.5 m high. The shield tunnel model was an assembly of tunnel lining ring models with grooves along the longitudinal direction. The simulation of the longitudinal joints weakened the transverse stiffness of lining ring models to some extent. Keys connecting lining ring models were used to simulate longitudinal bolts. By rotating the ring models, staggered joints of segments occurred in the tunnel model. Firstly, a free field model test was conducted, and acceleration responses of the model soil in consideration of different seismic motion input were obtained. Then, various conditions were considered in the shield tunnel-shaft junction model test, including different input directions of seismic motions, different types of seismic motions. And the circumferential joint openings, the acceleration responses and the transverse strains of the model were recorded and analyzed. The results show that with the valid design of the container, boundary conditions meet requirements and test data are credible. The frequency components of the acceleration responses of the shaft model and the tunnel model are the same and they are controlled by the surrounding model soil, while the major difference lies in the amplitude of the acceleration responses. The circumferential joint openings near the tunnel-shaft junction are significantly larger than the ones at the regular tunnel model. The former can be 1.6 to 4.5 times as much as the latter. The input directions of the seismic motions could greatly affect the circumferential joint openings at the regular tunnel model, while circumferential joint openings near the tunnel-shaft junction were hardly affected. Great transverse strain may occur at the shaft model around the tunnel-shaft junction under seismic effect, while the transverse strain of the tunnel ring models show no obvious increment.