Research On Vibration Characteristics Due To Surface And Underground Moving Loads

With the continuous growth of urban population,the traffic condition of the city becomes worse.In order to alleviate the pressure of urban transportation,underground transportation facilities such as subways are widely used in major cities.Underground transportation facilities often pass through densely populated areas and buildings.While these transportation facilities can reduce the pressure of urban traffic,the vibrations generated by subways will be transmitted to the buildings and the surface through lining and soil.These vibrations will disturb the lives of residents along the line,cause damage to surrounding buildings,and interfere with the use of precision instruments.In addition,in the construction and operation stage of shallow tunnels in cities,the surface traffic load will also have a significant dynamic impact on the tunnel.Therefore,the vibration characteristics of the foundation due to the surface and underground traffic load have important research significance.Based on the existing research background,this paper has carried out the research on vibration characteristics due to surface and underground traffic loads.The main research work is as follows:1.A vibration analysis model of the tunnel in the three-dimensional elastic half space under a surface moving load is established,and the vibration response of an adjacent shallow tunnel caused by surface traffic load is obtained.The ground is modeled as a viscoelastic half-space with a circular cavity and the tunnel wall is made of a viscoelastic medium.The vehicle load is represented by four rectangular pressures,which can be decomposed into symmetric and antisymmetric components with respect to the tunnel axis.The displacement field is decomposed into the displacement fields caused by the down-going plane waves and the outgoing cylindrical waves.The solution to governing equations of viscoelastic material is obtained.Based on the transformation of plane wave and cylindrical wave in rectangular coordinate system and cylindrical coordinate system,the boundary conditions of soil-tunnel interface and ground surface is described.The change of the horizontal distance between the vehicle load and the tunnel axis at different speeds on the dynamic stress distribution of shallow-buried tunnels with different burial depths is analyzed.2.A three-dimensional analytical element model of layered soil with a circular cavity is established.The model is composed of an analytical element with a cavity,a thin cylinder element and a number of thin shell elements.The wave function method and Fourier transform are used to solve the model.And the model can predict the vibration problems of the layered foundation with a cavity under the action of the surface moving load and the moving load inside the cavity.This paper focuses on the influence of tunnel depth on the response of ground vibration under the surface moving load.In addition,the influence of the natural frequency of the rail slab on the ground vibration response caused by the underground moving train load is also studied.3.Based on the analytical element model of three-dimensional soil layer with circular cavity,a method of non-stationary random vibration analysis of train-track-tunnel-soil system in three-dimensional layered foundation is proposed by pseudo-excitation method.The subway train is simulated by rigid body system with multiple degrees of freedom,and the rail and rail slab are simulated as infinitely long Euler Beams,this paper studies and compares the random vibration response under the floating slab track and the direct fixed slab track.In addition,it also analyzes the influence of train speed and inter-story stiffness on the random vibration response.In this paper,the theoretical analysis model of vibration caused by surface traffic load and underground traffic load is established,and the environmental vibration problem of foundation with tunnel under the surface and underground traffic is deeply studied.And it provides technical support for the precise assessment of the vibration caused by the surface vehicle load and the subway train.