4. 1 Control measures in the planning stage
In the initial planning stage, the literature.
(1) light vehicle.
(2) The wheels are smooth. The vibration intensity of vehicles can be effectively reduced by adopting wheel smoothing measures such as elastic wheels, damping wheels and wheel tread grinding.
(3) Use heavy rails and jointless tracks.
(4) Use a disc brake.
(5) Adopt linear motor. Linear motor has many advantages, such as low cost, low vibration, low noise, low energy consumption, low pollution and good safety performance, and it is the development direction of urban rail transit in 2 1 century.
(6) Properly control the running speed of subway trains.
(7) Adopt appropriate elastic fasteners or track dampers. At present, the fasteners commonly used in domestic subways mainly include DTI ~ DTVII, WJ2 and single-toe spring fasteners. These fasteners are mainly used in road sections with general vibration reduction requirements, and most fasteners can reduce vibration by 2 ~ 9 dB. Track dampers are usually used in areas with high vibration reduction requirements. At present, the new shock absorbers commonly used in track shock absorbers include Kelong egg shock absorber, improved Kelong egg shock absorber, sleeper boots and so on. Among them, sleeper shoes have the best vibration reduction effect, which can reach19db; Secondly, the improved Kelong egg reduces vibration by 7 ~ 8db；; The vibration reduction value of Kelong egg is 3 ~ 5dB.
(8) Choose a reasonable track structure to reduce the excitation intensity of vibration source. At present, in addition to the traditional ballasted track structure, there are two kinds of vibration reduction track structures: floating slab track structure and elastic short sleeper track structure (LVT, namely Sony Weir low vibration track). According to the measured data in Germany, the vibration reduction effect of floating slab track structure can be as high as 30dB, but its disadvantage is high cost. Floating slab track structure and elastic short sleeper track structure are adopted in different sections of Hong Kong West Railway, which has achieved good vibration reduction effect and made Hong Kong West Railway one of the quietest rail transit lines in the world. The domestic Guangzhou Metro 1 Line and Line 2 also adopted these two track structures reasonably, and achieved the expected results. However, the cost of these two track structures is relatively high.
4.2.2 Vibration Propagation Path Control
Through the analysis of vibration propagation path and its influencing factors, some vibration isolation or other measures can be taken to reduce the influence of vibration.
The elasticity of (1) foundation greatly affects the sensitivity of buildings to vibration. The greater the stiffness of the foundation, the lower the vibration response of the building. Therefore, we should strengthen the foundation of buildings within the influence range of subway vibration.
(2) The building vibration is related to the building structure, and the vibration attenuation is zero for the light structural frame or foundation; For heavy structural frames or foundations, the vibration attenuation is (15 5) db; For heavy structure buildings, the vibration decreases with the increase of stories, and each story decreases by 1 ~ 4 dB, while the vibration of light structure does not decrease with the increase of building height.
(3) By adjusting the stiffness of the building structure system, the natural vibration frequency of the structure is changed to avoid the phenomenon of * * * vibration caused by the low-frequency coupling between the main vibration source and the building structure.
(4) The control device can be installed on the building structure to reduce the vibration response of the building structure caused by subway vibration.
5 Problems to be studied
Although scholars at home and abroad have done a lot of research work on the vibration caused by subway operation, there are still many problems to be solved. For example:
(1) In the mechanism of subway vibration, the main influencing factors of subway vibration sources are the conclusions obtained through actual measurement, and there is no mature and accurate expression for the relationship between parameters.
(2) At present, due to the limitation of time and space, when studying the influence of subway train vibration, this three-dimensional space problem is generally simplified into a two-dimensional plane problem, and the accuracy of the conclusion cannot be determined.
(3) In the aspect of vibration control measures, the vibration control measures with frequency higher than 20Hz are mature, but the low-frequency vibration is still an unsolved problem. In recent years, the research on urban rail transit in Toronto, San Francisco and Philadelphia shows that the design of vehicle bogies (mainly low-stiffness suspension system and elastic wheels) has a great influence on low-frequency vibration, which deserves further study.
(4) The research on the influence of subway vibration on ground buildings and the response control of buildings will have important engineering and social significance.