饱和层状场地中地铁隧道地震作用的精细化分析模型研究

Metro tunnel is one of the important civil infrastructures of large cities. Both construction scale and development speed in China are the first in the world, and the magnitude and the damage of Wenchuan earthquake in China and Tohoku earthquake in Japan in recent years are exceed people's expectation. Development of metros in our country is faced with the challenge of both seismic safety and leading seismic design in the world. It should be pointed that, engineering sites are often saturated in coastal area due to high ground water level, and the most common case is that the soil layer over water level is dry poroelastic, and the below is saturated poroelastic, while the bedrock is elastic, which forms special saturated poroelastic layered sites. However, all the seismic design codes of metro tunnel in the world are not involved with the case of metro tunnel in saturated poroelastic sites. This project tries to solve linear and nonlinear dynamic interaction between soil and tunnel in two-dimensional elastic homogeneous site, elastic layered site or staturated poroelastic layered site, and to solve linear and nonlinear dynamic interaction between soil and infinite long tunnel in three-dimensional elastic layered site or staturated poroelastic layered site, and to establish a fine dynamic analysis model for seismic response of metro tunnel in saturated poroelastic sites, and to study the fundamental law of seismic actions including pore pressure, and then to propose a fine static analysis model for all the seismic actions. This project will establish the dynamic and static analysis models for seismic design of metro tunnel in staturated poroelastic sites, and finally solve the problem of seismic design of metro tunnel in staturated poroelastic sites. This study can provide scientific foundation for the improvement of present seismic design code of metro tunnel, and is significant in science and engineering.

地铁是大中城市重要的土木基础设施之一。目前我国地铁建设规模和发展速度均居世界第一，而近年来我国汶川大地震、日本东海大地震等，无论是地震震级还是地震震害，均超出人们的预料。我国地铁的发展，既面临着抗震安全性的挑战，也面临着抗震设计水平走在世界前列的机遇。我国沿海地区地下水位比较高，地下水位以上为干土层，地下水位以下为饱和层，刚度较大的基岩为单相弹性介质，形成一种特殊的饱和层状场地。然而国内外现行地铁隧道抗震设计规范均没有涉及饱和场地中地铁隧道的抗震设计问题。本申请项目拟求解二维弹性均匀场地、弹性层状场地、饱和层状场地中土与隧道之间的线性和非线性动力相互作用，求解三维弹性层状场地、饱和层状场地中土与无限长隧道之间的线性和非线性动力相互作用，建立饱和层状场地中地铁隧道地震作用的精细化动力分析模型，研究地铁隧道地震作用的基本规律，并在全面准确把握各项地震作用基础上，建立各项地震作用的精细化静力分析模型。本项目最终建立饱和层状场地中地铁隧道抗震设计的动力分析模型和静力分析模型，解决饱和层状场地中地铁隧道的抗震设计问题，具有重要的科学意义和工程价值。

我国沿海地区地下水位比较高，地下水位以上为干土层，地下水位以下为饱和层，刚度较大的基岩为单相弹性介质，形成一种特殊的饱和层状场地。然而国内外现行地铁隧道抗震设计规范均没有涉及饱和场地中地铁隧道的抗震设计问题。本申请项目在求解二维弹性均匀场地土-隧道动力相互作用解析解答、二维饱和层状场地场地中土-隧道动力相互作用的间接边界元耦合解答、二维饱和层状场地场地中土-隧道非线性动力相互作用的有限元-间接边界元耦合解答、2.5维饱和层状场地中土-隧道非线性动力相互作用有限元-间接边界元耦合解答的基础上，建立了饱和层状场地中地铁隧道地震作用的精细化动力分析模型，探讨了地铁隧道地震作用的基本规律。研究表明，饱和土骨架和孔隙水的动力耦合作用对孔隙动水压力大小有显著影响，将饱和土简化为单相介质模型会导致较大的计算误差。水土合算的结果明显偏小，而水土分算的结果则过于保守，且水土合算和水土分算的动土压力分布与实际均有明显差异。土-隧道动力相互作用显著增加地下隧道地震动土作用的峰值。地震动土作用随隧道埋深增加呈增大趋势，随隧道刚度增加呈增大趋势，随隧道间距的减小呈增大趋势。地震动土作用与土体非线性关系密切。地震动土作用的分布以隧道零应力轴位置为参考近似呈线性分布。地震孔隙水压力与地震动入射角度密切相关，针对地震动垂直入射、水平激励而言，地震孔隙水压力占地震动土作用的比例约为10%。无限长隧道2.5维地震动土作用与二维情况有较大差别，将2.5维问题分解为二维平面内和二维平面外两个问题分别求解可能导致较大误差。项目在建立精细化动力分析模型和研究地震作用基本规律的基础上，建立了饱和层状场地中地铁隧道地震作用静力分析模型，静力分析模型具有良好精度，可以用于地下隧道的抗震设计。项目为饱和层状场地中地铁隧道的抗震设计中的地震作用问题的解决提供了科学依据，具有重要的科学意义和工程价值。

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