Study On The Vibration Of Bridge Of Adjacent Existing Lines From High-Speed Train Viaduct Under Operation And Vibration Reduction Measure Of Isolation Trenches

Recently,high-speed railway has been developed rapidly in China,and gradually become one of the most important middle and long distance transportation means.With the increasing train speed, the vibration problem induced by trains is getting much more serious. Research has shown that when the velocity of train is greater than the Rayleigh wave velocity of the topsoil, the vibration will be enlarged. Hu-Ning high-speed railway line is the first high-speed railway built on soft soil in China, and the vibration data has not been tested since it was put into use not too long ago. Meanwhile, the new line was designed to be comparatively close to those existing lines and in some sections the distance between them is even smaller than ten meters, the problem that the train-induced vibration impacts on the adjacent existing structure in the soft soil is still undefined and need further research.In this paper,thereotical analysis, field test and numerical calculation methods were used in combination,taken the Huning high-speed railway viaduct section and its adjacent existing bridge structure as the objects, to study the train-induced vibration impact under different conditions. Also the different vibration isolation effects provided by various trenches in the CFG pile embankement structure was discussed.The main research results are as follows:1.A vibration test in Desheng river section has been conducted to analysis the vibration characteristics of Hu-Ning high-speed railway and its effect on the adjacent existing bridge. The test results were analyzed from acceleration time history, acceleration level, vibration peak particle velocity and1/3octave band of acceleration. The results are concluded as:Fastener system and bearing are the key point of vibration attenuation; the vibration induced by the high-speed railway almost has no effects on the structures of adjacent existing lines; when trains with different locomotive type pass, the frequency spectrum of rail is different,while the others’nearly the same.2.In this paper,a three dimensional vibration analysis model with ANSYS was established and the vibration characteristics of Hu-Ning high-speed railway under different conditions was also discussed. The main conclusions are as follows:when high-speed train run over the viaduct section with speed of200km/h,250km/h,290km/h and350km/h respectively, trains with250km/h induce the largest vibration while the trains with350km/h produce the smallest; the smoothness of rail is very significant,the vibration acceleration level of soil under America’s sixth track spectrum is thirty percent-thirty five percent more than now; when it is close to the excitation source, the harder the subgrade soil is, the larger the vibration will be. However, vibration wave spread much further in the softer soil.3.A two dimensional vibration analysis model with ANSYS was bulit to analysis the isolation effect of open and filled trenches with different sizes. The conclusions are as follows:Increasing width can improve the performance of vibration isolation obviously, but with depth increases, the increase of width hardly has effects on the performance; for CFG pile embankment structure in high-speed railways, the closer the open trenches is to the rail central line, the better the performance of vibration isolation could be.