Abstract: The high-speed railway bridge and tunnel junction is considered as a complex engineering project. At the event of strong earthquake, serious damage or even completely destruction of this junction would occur under complex topography or poor geological conditions. However, there is limited information on the seismic damage mechanism and dynamic response of interactions between different structures and locations in the complex bridge-tunnel-rock system. Therefore, large-scale shaking table tests were carried out on soft surrounding rock. The seismic dynamic response characteristics of the bridge-tunnel junction and the influence mechanism of the excitation direction were analyzed as well. The experimental results showed that the effect of strong earthquake is detrimental to the safety and stability of the bridge-tunnel-soft rock system. There were significant differences on variation laws of dynamical responses such as the acceleration, displacement and strain parts at the tunnel entrance and the end of the bridge under different earthquake excitations. Relatively large values of seismic responses could occur at the overlapped parts or sections of the bridge-tunnel junction (arch waist and arch foot at lining expansion section, arch foot at the tunnel standard section, the bridge beam end and top of the abutment inside the tunnel portal, and the soil above the cave roof etc.), which required special reinforcement or treatment. The obtained results provide useful references for the further study of structural seismic design and seismic response analysis of bridge-tunnel connecting structures in soft surrounding rock conditions.

Key words: soft rock, bridge-tunnel approaching part, large scale shaking table, different excitation directions, seismic responses