Study On Finite-Element Analysis And Isolation Of Soil Layer Vibration Under Excitation Of Subway

It is important to discuss the dynamic responses of structures induced by subway trains since the subway develops rapidly in China, and more and more noise and circumstance problems caused by the vibrations produced by passage of subway trains are encountered. This paper attempts to demonstrate three problems based on the deep-covered soft soil in Shanghai and the new construction in Shanghai Music University. A famous commercial FEM analysis software MSC.Nastran is used to build planar FEM models to discuss these questions associated with actual measurement data. The main research work is described as follows:1. The soil was assumed to be homogeneous and linear viscoelastic medium under vertical vibration of subway trains. Planar FEM models of soil-subway system were established for model analysis and transient response analysis under excitation of the sine-wave with different frequency. Several numerical examples are computed to compare the influence of mesh scale and artificial boundary on the soil dynamic responses and model characteristics. Some conclusions are obtained from the examples.2. Several numerical examples with different horizontal lengths and vertical thickness of the limited soil layer are computed for comparisons of the natural frequencies and dynamic responses of the systems. The soil vibration response to harmonic excitation with different scope of soil is discussed. It will be the foundation for how to consider the scope of soil layer in soil layer response analysis under subway vibration which was calculated by direct finite-element method.3. The effect of vibration insulating walls to suppress the soil vibration is discussed by using several numerical examples. The numerical results are compared with actual measurement data in order to analysis the actual effects of walls and verify their reliability. Some useful conclusions which could give suggestions to engineering design are conducted. Based upon the case study, the influence of the wall's depth and exciting frequency on its isolating effect is analyzed.