超长沉管隧道纵向地震响应频域分析方法

中国目前还没有专门的沉管隧道抗震规范,且以往的地震响应分析方法考虑的因素不够全面,比如通常忽略隧道惯性的影响、不能考虑复杂地基条件、不能考虑沉管底部非一致地震激励以及不能考虑土体动刚度系数和阻尼系数的外部激励频率相关性等。基于此考虑,在借鉴日本水下隧道抗震设计规范所推荐方法(响应位移法)的基础上,利用Winkler地基梁理论和快速Fourier变换技术,建立了动力Winkler地基梁频域分析方法。最后,分别采用响应位移法和本文所提之分析方法对港珠澳大桥海底沉管隧道工程进行了纵向地震响应计算,对两种计算方法作了讨论和评价,并提出了一些对港珠澳沉管隧道工程抗震设计具有参考价值的结论和建议。

Frequency-domain analysis method for longitudinal seismic response of super-long immersed tunnels

There is no special code for seismic design of immersed tunnels in China at present. Furthermore, inertia of the tunnel, complex ground conditions, non-uniform seismic excitation at the bottom of the tunnel and dependence of soil-structure interaction coefficient on earthquake excitation frequency are always neglected in the past analysis methods for seismic response of immersed tunnels. Based on this consideration, a frequency-domain analysis method for longitudinal seismic response of immersed tunnels is established using the Winkler foundation-beam theory and the fast Fourier transform technique. The response displacement method and frequency-domain analysis method based on Winkler foundation-beam theory are used to compute Hong Kong-Zhuhai-Macao (HZM) immersed tunnel, and difference between the two approaches is discussed. Some conclusions and suggestions are presented for the seismic design of HZM immersed tunnel. Although this research is prompted by need of a concrete project, the proposed methods are universal and can be applied to the analysis and design of other immersed tunneling projects.