Soil-structure interaction of shallow tunnels in liquefiable soils during strong earthquakes

在快速发展的城市中，地下结构尤其是隧道是可持续和高效的交通系统的重要组成部分。在不久的将来，它们将在自动驾驶系统的实施中发挥更重要的作用。与结构损失甚至长期服务中断相关的经济和社会代价是巨大的，只有极小的发生概率才能接受。除了主要由土壤和地下水引起的静荷载外，地震区的隧道还必须经受住地震。在这种情况下，隧道结构的性态主要受周围土体与隧道结构(SSI)相互作用的影响。虽然隧道在静力和中弱地震荷载作用下的受力机理已为人们所熟知，并可在设计中得到适当的解决，但隧道在强震作用下的行为仍是研究的重点。尤其是液化土层中的浅埋隧道是隧道工程中最具挑战性的问题之一，同济大学(TJU)和慕尼黑工业大学(TUM)的联合研究将为分析和预测可液化土层中浅埋隧道在强震作用下的地震反应提供可靠的数值方法和独特的实验数据库。这种数值方法不仅可以评估液化对隧道结构的影响，为风险决策提供依据，而且还可以在考虑到与SSI问题相关的岩土和结构风险的情况下，通过计算机辅助设计和优化所需的缓解措施。在第一阶段，将研究SSI问题的各个组成部分(土壤、隧道和土-隧道界面)，并验证相应的本构模型。新设立的单元试验、独特的多向振动台试验和使用土工离心机的试验突出了该试验计划。第二阶段将致力于在第一阶段结果的基础上开发一个全面的SSI模型。合作研究在很大程度上得益于相互补充的经验和知识转移，以及先进的实验设施，特别是在天津大学结构实验中心。具体地说，在TJU将大型多向层流摇箱与离心机测试相结合的可能性在世界范围内是独一无二的，目前在德国还没有。

Underground structures in general and tunnels in particular are essential components of sustainable and efficient transportation system in fast growing cities. They will play even a more important role for the implementation of automated driving systems in the near future. The economic and social costs associated with structural loss or even a long-term interruption of service are huge and only acceptable with a very small probability of occurrence. In addition to static loads, mainly resulting from the soil and groundwater, tunnels in seismic regions must withstand earthquakes. The behaviour of tunnel structures under these conditions is dominated by the interaction between the surrounding soil and the tunnel structure (SSI). While the mechanism of the SSI under static and weak to moderate seismic loads is well understood and can be properly addressed during design, the behaviour of tunnel during strong earthquakes is still in the focus of research. Particularly, shallow tunnels in liquefiable soil are one of the most challenging problems in tunnel engineering.The joint research of Tongji-University (TJU) and Technical University of Munich (TUM) will provide a robust numerical approach and a unique experimental database to analyse and predict the seismic response of shallow tunnels in liquefiable soils during strong earthquakes. The numerical approach not only will enable the assessment of the impact of liquefaction on tunnel structure and provide the basis for risk-informed decision-making, but also will allow for computer-aided design and optimization of the required mitigation measures under consideration of the relevant geotechnical and structural risks associated to SSI problem.The joint research consists of two phases. In the first phase, the individual components of the SSI problem (soil, tunnel and soil-tunnel interface) will be investigated and the corresponding constitutive models will be validated. The experimental program is highlighted by newly set up element tests, a unique multidirectional shaking table tests, and tests using a geotechnical centrifuge. The second phase will be devoted to the development of a comprehensive SSI model based on the results of first phase.The collaborative research largely benefits from mutual complementary experience and knowledge transfer as well as the advanced experimental facilities available in particular at the Structural Experimental Center of TJU. Specifically, the possibility to combine large multi-directional laminar shakebox with centrifuge tests at TJU is unique worldwide and not currently available in Germany.