隧道洞口软硬围岩交接段地震响应大型振动台模型试验研究

为提高强震区交通隧道洞口段的地震安全性和结构抗震性能，以汶川地震白云顶隧道进口段为研究背景，开展了隧道洞口软硬围岩交接段地震响应的大型振动台模型试验研究。介绍了试验方案设计，主要包括试验设备、相似设计、动力荷载、动力特性及加载制度。对试验数据进行了分析，主要研究了隧道洞口软硬围岩交接段由硬岩向软岩方向发展过程中隧道结构地震动峰值加速度（PGA）、纵向应变、接触应力及结构内力的空间变化规律。研究结果表明：隧道洞口软硬围岩交接段由硬岩向软岩方向发展，隧道结构PGA放大系数由1.04增大至1.68，纵向应变增加倍数由1.09增大至4.29，接触应力增加倍数由6.34增大至32.16，安全系数最小值减小百分比由26.18%增大至53.48%；随着受软岩影响的增大，作用于隧道结构的地震惯性力和强制位移不断增加，致使结构安全性不断降低。研究成果可为高烈度地震区交通隧道抗震设防设计提供参考。

Study on Large-scale Shaking Table Model Test for Seismic Response of Soft and Hard Surrounding Rock Interface Section of Tunnel Portal Part

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.