特大断面隧道地震动力特性的振动台试验研究

以福州市二环路金鸡山隧道扩建工程为背景，设计制作了特大断面隧道的1/30缩尺模型，并在福州大学土木工程实验中心的双向地震模拟振动台上，完成了21种工况下的模拟地震动试验。对试验数据进行傅立叶分析，发现浅埋条件下特大断面隧道的存在，显著地改变了原场地的动力特性；第一卓越频率主要体现原场地的动力特性，而第二卓越频率主要体现衬砌结构的动力特性。对试验数据进行频响分析，发现地震波自下而上传播至衬砌结构顶部以后，其第二卓越频率附近的频率成分发生了显著增益；其最大增益频率大致等于第二卓越频率。分析特大断面隧道动力特性与输入地震动幅值的关系，发现经历大振幅地震波激励后，衬砌结构上裂缝发展较为显著，其整体刚度明显降低，从而导致第二卓越频率和最大增益频率出现较为明显的下降。基于上述研究成果，进一步提出了特大断面隧道抗震设防的工程建议。

Seismic property of a large section tunnel based on shaking table model tests

In this study, a 1/30 model for a large section tunnel is firstly designed based on the extension project of Jinjishan Tunnel along Fuzhou 2nd ring road. Then the earthquake-simulating tests are conducted under 21 different loading conditions using a bidirectional earthquake shaking table apparatus at Fuzhou University. Through Fourier analysis of testing results, it indicates that the existence of the large section tunnel changes the seismic property of original ground significantly. It is also found that the 1st predominant frequency reflects the seismic properties of original ground, while the 2nd predominant frequency demonstrates seismic properties of the lining structure. The frequency-response analysis of testing results shows that the components augment significantly around the 2nd predominant frequency, when the seismic wave propagates from the bottom to top until the lining structure. The most-augmented frequency almost equals to the 2nd predominant frequency. The relationship between the seismic property of the large section tunnel and the amplitude of input ground motion is studied in detail. The apparent cracks emerge on the lining structure after the excitation by the large ground motion, which significantly reduces the overall stiffness of the large section tunnel. Moreover, both the 2nd predominant frequency and the most-augmented frequency show remarkable reductions. In conclusion, this study provides some useful suggestions for the earthquake fortification of the large section tunnel.