The Soil Dynamic Response Based On 2.5D Finite-element Method

With the development of track traffic and the increase of train speed in China, people have given more and more concern to the influence of vibration induced by traffic load. In the context, it is very important to research the calculated method of the dynamic response of soil under moving load.Understanding the mechanism of vibration generation and its propagation rule is the prerequisite to evaluate environmental vibration correctly and appropriately. The object of the paper is the influence of environment vibration induced by city viaduct railway traffic system. Generally, track structure consists of track, rail pad, sleeper and ballast. When train running on the track, there has interaction between wheels and track, and the track will bend because of the weight of wheels. Then, the bending waves will propagate to soil and around areas through the component of track structure, which can cause the second vibration on buildings. Based on above analyses, the main ideas of this paper can be summarized as follows:1. The basic principle of 2.5D FEM method is to reduce 3D problem to 2D problem through wavenumber transform along track direction, and the ground perpendicular to the track is discreted by finite element. Then the results of 3D problem can be obtained by wavenumber expansion of 2D calculation results along track direction. The essential process of the 2.5D FEM method has been deduced in chapter two of the paper, and it is the basis of last.2. For the 2.5D FEM method presented in chapter two, I developed a computer code applying Fortran computer language. By the step, we arrive to changing from theory to application. The validity of the method is verified by the mutli-layer method.3. Lastly, ground vibration induced by subway train load is analyzed by the method. During the simulation, different velocity and frequency of the load was considered, the results of different points has been derived.In the end, the content of this paper has been summarized, some problem which need further study have been proposed.