Abstract:In order to improve the seismic safety and structural seismic performance of portal section of traffic tunnels in meizoseismal area, based on the research background of the Baiyunding tunnel portal in Wenchuan earthquake, a large-scale shaking table model test study on the seismic response of the soft and hard surrounding rock interface section of the tunnel portal was carried out. Firstly, the design of test scheme was introduced, including test equipment, similar design, dynamic load, dynamic characteristics and loading system. Then, the test data was analyzed, and the spatial variation law of peak earthquake acceleration (PGA), longitudinal strain, contact stress and internal force of tunnel structure during the transition from hard rock to soft rock at the soft and hard surrounding rock interface section of the tunnel portal were studied. The results showed that the development of the soft and hard surrounding rock interface section in the tunnel portal was hard rock to soft rock. The magnification factor of PGA increased from 1.04 to 1.68, the increasing multiple of longitudinal strain increased from 1.09 to 4.29, and the increasing multiple of contact stress increased from 6.34 to 32.16, the percentage reduction of minimum safety factor increased from 26.18% to 53.48%. The seismic inertia force and the forced displacement acting on the tunnel structure increased continuously with the influence of soft rock increasing, resulting in the structural safety decreasing continuously.The results of this research can provide a reference for the traffic tunnel design and the seismic fortificat in highly seismic regions.