滨海软土地层隧道衬砌地震动力响应及损伤特征

地震作用下穿越软土地层的地铁隧道易受到严重破坏。因此,研究该类型地层下隧道的地震响应及损伤特性对地铁的安全运营至关重要。为此,首先结合分段曲线损伤模型和Druker-Prager弹塑性模型推导出反映混凝土损伤的弹塑性方程。然后借助FLAC3D有限差分程序及二次开发接口建立以混凝土管片损伤模型为基础的土-盾构隧道相互作用模型。最后对水平和竖直方向地震波影响下盾构隧道的动力响应及结构损伤进行研究。研究结果表明：(1) 通过FLAC3D数值软件的单轴拉伸和压缩试验得出所建立的混凝土管片弹塑性损伤模型能够很好的反映混凝土的力学损伤特性及材料的软化发展规律,从而验证了该模型的合理性与准确性。(2)盾构隧道的动力响应及损伤度与地震振幅呈现正相关性。水平方向地震波、竖直方向地震波作用下隧道结构的最大损伤增量位置分别为隧道拱脚、拱肩处和隧道两侧处。其中,竖直方向入射地震波对隧道损伤度的影响更为显著。

Study on seismic dynamic response and damage characteristics of tunnellining in coastal soft ground

Subway tunnels crossing soft ground under seismic action are susceptible to severe damage. Therefore, the study of seismic response and damage characteristics of tunnels under this type of stratum is essential for the safe operation of subways. To this end, the elastic-plastic equations reflecting the concrete damage are first derived by combining the segmental curve damage model and the Druker-Prager elastic-plastic model. Then, a soil-shield tunnel interaction model based on the damage model of concrete pipe slice is established with the help of FLAC3D finite difference program and secondary development interface. Finally, the dynamic response and structural damage of shield tunnels under the influence of seismic waves in horizontal and vertical directions are investigated. The results show that: (1) The uniaxial tensile and compressive tests with FLAC3D software show that the elastic-plastic damage model can reflect the mechanical damage characteristics of concrete and the softening development of the material, thus verifying the reasonableness and accuracy of the model. (2) The dynamic response and damage degree of the shield tunnel show positive correlation with the seismic amplitude. The maximum damage increment locations of the tunnel structure under the action of horizontal direction seismic waves and vertical direction seismic waves are at the foot of the tunnel arch, at the shoulder of the arch and at the sides of the tunnel, respectively. Among them, the effect of the incident seismic wave in vertical direction on the damage degree of the tunnel is more significant.