盾构隧道纵向地震响应的多尺度分析方法

针对目前盾构隧道抗震设计仅限于横断面分析,缺乏有效的纵向地震响应分析方法的问题,提出了一种用于模拟盾构隧道纵向地震响应的宏-细观多尺度分析方法,其中宏观等效模型用于描述盾构隧道结构整体的地震响应特性,细观精细化模型用于捕捉结构关键断面接头处的变形响应。宏观等效模型采用黏弹性地基梁来模拟,即将盾构隧道沿纵向简化为作用在黏弹性地基上的三维梁单元,且充分考虑了由于环缝影响引起的梁纵向等效刚度折减以及隧道内部结构对纵向等效刚度的附加效应。基于宏观等效模型的地震响应规律分析,确定出盾构隧道沿线的最不利断面位置,从而将这些关键区段替换为考虑隧道环缝接头的细观精细化模型,即采用沿环向分布的轴向拉压弹簧和切向剪切弹簧来真实模拟地震作用下的环缝张开量和错位量等变形,克服了传统连续均质化模型无法反映环缝变形量的不足。最后,将该多尺度分析方法成功应用于世界首个特高压GIL电力盾构隧道,为实际重大工程的结构纵向抗震设计和安全性评价提供了科学依据和技术手段。

Multi-scale Method for Longitudinal Seismic Response Analysis of Shield Tunnels

The number of effective longitudinal seismic analysis methods is limited, and seismic design of shield tunnels mainly concentrates on cross-sectional analyses. This paper presents a multi-scale method for calculating the longitudinal seismic responses of shield tunnels. A macroscopic equivalent model was used to describe the seismic response of the entire shield tunnel, and a mesoscopic model was used to obtain the deformations in the critical joints. The macroscopic equivalent model was simulated as a beam supported on viscoelastic foundations. The shield tunnel was simplified as a three-dimensional beam supported on viscoelastic foundations. The reduction in the longitudinal stiffness due to the influence of joints and the additional effect of internal structures was taken into consideration. Based on the results obtained from the macroscopic equivalent model, several dangerous cross-sections were identified, and the mesoscopic model was used in these sections. The opening and dislocation of circumferential joints is reflected in the deformations of the axial tensile and compressive springs and the tangential shear springs. This method overcomes the drawback of the traditional continuous homogeneous model that is unable to reflect the deformations in tunnel joints. Finally, application of the multi-scale analysis method to the world's first UHV GIL power shield tunnel provides the scientific basis and technical means for seismic design and safety evaluation in actual engineering scenarios.