Vibration Analysis And Vibration Environment Impact Assessment Of Monolithic Roadbed Track System

With the rapid development of subway, vibration and noise caused by subway train have been already been concerned widely because of their shortcomings. However, our knowledge about subway vibration is limited, especially about subway vibration loads, propagation of subway vibration, damping measures of subway vibration and so on. Obviously, these problems need special researches.Based on Qingdao Subway Line3Environment Assessment Project, the dynamic characters of vehicle-track system, the impact of parameters on structural properties, subway vibration loads, propagation of subway vibration, and vibration prediction have been researched roundly in this thesis. The research methods include theoretical analysis and numerical simulation. The main work is as follows:1. Using theoretical analysis or numerical simulation, the modal information of vehicle-track system has been calculated. Meanwhile the impact of structural parameters is discussed:when the stiffness of the rail fastenings is greater than20kN/mm, the riding comfort and the transmission rate of the system will achieve a relatively high level; if the mass of sleepers is100kg, the force on the foundation is relatively small and the riding comfort of the vehicle is high; when the stiffness of the elastic pads is above3kN/mm, the structural properties of the system is relatively good.2. On the basis of the irregularity of rail, the subway vibration load on the monolithic roadbed war calculated. When the subway vehicle speed is60km/h, the amplitude of the load on the monolithic roadbed is42kN, and the amplitude is45kN as the speed is70km/h.3. Many questions, such as model size and element size, have been discussed under the premise of meeting the calculation accuracy. It tells us that horizontal size of the FEM model should be240m, the vertical size should be60m, the element size of clay should be0.5m and the element size of rock should be2.0m. The spring-damper element was used to simulate the artificial boundary of FEM model, and the equations of element parameter were also given.4. The calculation results show that structural maximum vibration velocity of Haibinlvguan is1.50mm/s, which can’t satisfy the national code. The vibration grade of Shuangshancun is76.2dB, which is also exceeds the vibration standards, and some isolation work is necessary. The propagation is analyzed:the subway vibration of Haibinlvguan which is the most violent vibration is10m from the tunnel. With the accretion of the distance away from the center of the tunnel, the grade of vibration is gradually up to the higher level and then down to the lower level. The most violent vibration of Shuangshancun is right upon the tunnel, and the grade of vibration is gradually down to the lower level with the accretion of the distance away from the tunnel.5. Prediction equation of subway vibration was built. The prediction results of Haibinlvguan and Shuangshancun were compared with FEM calculation results, and the conclusion was that the two vibration grade is very close to each other, and the deviation is small when distance to tunnel is within60m.