Study On Effect Of Vibration Isolation Barrier On Mitigation Of Low Frequency Vibration Induced By Metro Traffic

Although the subway transportation is convenient for citizens,the vibration generated by its operation will have a certain impact on the sensitive instruments in some laboratories along the subway line.In general,compared to the high-frequency vibrations,sensitive instruments have higher requirements for low-frequency vibrations in the environment where it is used,and the vibration reduction measures in the subway vibration source cannot meet the requirements for the low-frequency vibration reduction.Measures should be considered to reduce the low frequency vibration caused by subway train operation.In this paper,the vibration isolation barrier of the subway vibration propagation path is taken as the research object.Through field testing and finite element numerical simulation and other means,the effects and laws of low-frequency vibration isolation of the vibration isolation trench,vibration isolation wall and vibration isolation pile are explored.Vibration isolation effect of two damping measures for slab track and vibration isolation barrier.Finally,based on the engineering background of the influence of a subway line in Hefei on the surrounding laboratory's environmental vibration,the vibration-reduction effect of the vibration isolation trench,vibration isolation wall and vibration isolation pile in this laboratory is studied.The main research contents of this paper are as follows:(1)The vehicle-rail coupling analytical model based on infinite periodic structure is used to simulate the vibration source excitation of the subway transportation system,and the MIDAS-GTS numerical software is used to establish a tunnel containing vibration isolation trenches,vibration isolation walls and vibration isolation piles under different working conditions The formation dynamic finite element model has studied in detail the influence of barrier position,barrier depth,barrier width,barrier row number,layout form and other factors on the low-frequency vibration reduction effect of the vibration isolation barrier,and proposed the optimal parameter combination of various vibration isolation barrier in the low-frequency vibration isolation of subway traffic.(2)Using numerical methods and field vibration testing,the vibration effect of a subway in Hefei City on the surrounding laboratories was predicted,and three vibration isolation measures of vibration isolation trench,vibration isolation wall and vibration isolation pile were designed,and the actual low frequency vibration isolation effect was studied.The research results show that:(1)Different vibration isolation laws were shown between the vibration isolation trench and vibration isolation wall,vibration isolation pile.The low-frequency vibration of the subway will amplify before the vibration isolation trench,and will produce a relatively stable and significant vibration isolation effect within a certain range after the vibration isolation trench.(2)Compared with the vibration isolation trench,the subway vibration reduction effect is more significant within 5m behind the vibration isolation wall.After 5m,the vibration reduction effect gradually decreases.The width and depth of the vibration isolation wall have a greater impact on the vibration isolation effect;the vibration isolation law of the vibration isolation pile is similar to that of the vibration isolation wall.After the vibration isolation pile is applied,the vibration will be significantly attenuated at the interface of the vibration isolation pile and the soil,and the vibration reduction effect is obvious within 5-10 m after the vibration isolation pile.The vibration attenuation tends to be gentle beyond 10 m after the vibration pile;the arrangement form of the vibration isolation pile has little effect on the vibration isolation effect,and the vibration isolation effect of the matrix arrangement and the plum blossom arrangement is basically the same.(3)Vibration isolation barriers works above 5Hz.The amount of vibration isolation reaches the maximum around 10 Hz,but it cannot isolate extremely low frequency subway vibration below 5Hz.The location of the vibration isolation barrier has a significant impact on the vibration isolation effect of vibration sensitive targets,the closer the vibration isolation barrier is to the sensitive target,the better the vibration isolation effect;the depth of the vibration isolation barrier also has a greater impact on the vibration isolation effect of the sensitive target,only when the depth of the vibration isolation barrier reaches at least the depth of the tunnel base,the vibration isolation effect is more significant;the number of rows of vibration isolation walls and piles also have a certain effect on the vibration isolation effect.As the number of rows increases,the vibration isolation effect becomes better and better.