Evaluation of structural fatigue properties of metro tunnel by model test under dynamic load of high-speed railway

Abstract

As the acceleration of urbanization and modernization process in China, there will be more and more cross-projects between metros and high-speed railways and other projects. For near distance cross-projects, the structural fatigue problems caused by dynamic loads of high-speed trains are also becoming increasingly serious in tunnel engineering. A large-scale model test was utilized to study structural fatigue problems of shield tunnels under high-speed railway dynamic loads. Firstly, based on a large number of numerical simulations, the complex dynamic load of high-speed railway was simplified to a simple sinusoidal wave, and the most unfavorable position of segmental linings was proposed. Then, the fatigue assessment method of segmental linings in the prototype and cyclic load times in the laboratory were also put forward. Finally, in the model test, some key technical details were also analyzed, including the types of segmental linings, similarity principle and materials, sensors layout, and model fabrication. The results illustrate that the simplified waveform is well applied to numerical simulation and model experiment under the action of a single load. The experiment reveals that there are no obvious fatigue cracks and structural failure during the whole loading process, and the research draws the conclusion that the fatigue life of metro shield tunnels can meet the requirements of the service life of 120 years. Furthermore, there is an important phenomenon of the uplift and dislocation of segmental linings in a certain range. Therefore, the research results can also provide a good guidance for the design of a new metro tunnel and the repair and maintenance of built metro tunnels.