Study On The Vibration And Secondary Noise Characteristics Of Sensitive Buildings Along Metro Lines Induced By Metro Operation

In recent years,China has been vigorously developing metro and other forms of urban rail transportation,but the vibration and secondary noise caused by sensitive buildings along the line are becoming more and more serious,and there are a large number of complaints every year,so it is necessary to carry out research on vibration and secondary noise of sensitive buildings under metro operation.Based on an actual project,this paper establishes a method for predicting the vibration and secondary noise of sensitive buildings under metro operation,and grasps the impact of metro operation on the vibration and secondary noise of office buildings and secondary schools through the study,and finally puts forward a plan for effective control of vibration and secondary noise of sensitive buildings based on the calculation results.(1)Firstly,we introduced the background of this thesis,including the introduction of the target buildings(including two sensitive buildings,namely a school and an office building),the situation of the target site and the situation of the operating metro line;then we proposed a research method for the study of vibration and secondary noise of sensitive buildings under metro operation for this practical engineering application;based on this method,we established a vibration prediction model for sensitive buildings along the metro operation,which Based on this method,a vibration prediction model for sensitive buildings along the underground operation is established,which mainly includes two sub-models,namely the train-track system coupling dynamics sub-model and the track-tunnel-soil-buildings system dynamics sub-model;at the same time,a secondary noise prediction model for sensitive buildings along the underground operation is formed by relying on the prediction formulae given in the Guidelines for Environmental Impact Assessment of Urban Rail Transit(HJ 453-2018)(referred to as "18 Guidelines");and at the end The evaluation criteria of building vibration and secondary noise for this paper are given,which mainly rely on the relevant standards for the three key indexes of maximum z-vibration level,maximum vibration level of split frequency and maximum sound pressure level of secondary noise.(2)In terms of the impact of underground operation on sensitive building vibration,the amplitude of the fastener force is about 32 k N,and the excellent frequency is below10 Hz and in the range of 40～80Hz;the wheel-rail force also exists in the range of40～80Hz with large energy;the vibration frequency of the affiliated secondary school caused by underground operation is mainly concentrated in the vicinity of 8Hz and63 Hz.The maximum vibration level of the sub-frequency is 60 d B and the maximum z-vibration level is 63 d B,both of which are lower than the values specified in the standard,indicating that the vibration impact of the underground operation on the building structure of the secondary school is not obvious;the vibration frequencies of the office building caused by the underground operation are mainly concentrated around8 Hz and 63 Hz.The maximum vibration level is 70 d B and the maximum z-vibration level is 73.6d B,which is much higher than the value specified in the standard,and the locations of exceedance are mainly concentrated in the basement,the ground floor and the first floor,indicating that key attention should be paid to these floors when the office building construction scheme is subsequently adjusted.(3)In terms of the impact of the metro on the secondary noise of sensitive buildings,the sound pressure level of the entire frequency range decreased after the noise data was A-weighted,especially in the low frequency region,the decrease was more obvious;the superior frequency range of the secondary noise of the building changed to a certain extent compared to the time when it was not weighted,the first main frequency appeared near 200 Hz,while the second main frequency was in the range of 50-80 Hz,which also illustrates from the side The maximum sound pressure level of the basement reached 42.8 d B(A),exceeding the standard by 4.8 / 7.8 d B(A)(daytime / nighttime),while the third floor exceeded the nighttime standard by 0.7 d B(A)and did not exceed the daytime noise standard;the office building Secondary noise exceedances were found on all floors of the building,with the basement of the office building exceeding the standard by 15.4 d B(A),even during the daytime when 12.4 d B(A)was still exceeded;even the highest floor of the building,the fifth floor,threw up exceedances of3.8 and 6.8 d B(A);the use of secondary noise from the structure to assess the environmental impact of the metro line operation is more stringent than the use of vibration alone.The use of structural secondary noise to assess the environmental impact of the metro line operation is more stringent than the use of vibration alone,and is more likely to ensure the comfort of living and working for the residents and staff in the building.It is recommended that when assessing the impact of the operation of the metro on the vibration and secondary noise of sensitive buildings along the line,we should not simply consider vibration alone,but should take into account the secondary noise of the structure in order to more comprehensively assess the impact of the operation of the metro line on the entire building along the line.(4)From the perspective of vibration control,it is recommended that the distance between the office building and the underground line should not be less than 65.3m,and for the sake of engineering control,it is recommended that the value be taken as 66 m.From the perspective of secondary noise control,for the affiliated secondary school,the distance between the secondary school and the underground line needs to be pushed beyond 71.7m,while for the office building,the distance needs to be greater than 73.7m,so for the sake of engineering Therefore,in order to facilitate control in the project,it is recommended that the distance between the affiliated secondary school and the subway line in this project should be no less than 72 m,while for the office building,it needs to be no less than 74 m.