Analysis Based On Field Measurement Of Metro Tunnel Environment And Influencing Factors In Chongqing

As a part of urban rail transport,tunnel has direct or indirect influence on the normal operation of trains and the environment of platform.To fully realize the changing rules of tunnel environment and its influencing factors in actual operation is an important step to improve the control of tunnel environment with high efficiency and low energy consumption.Tunnel environment is divided into wind environment,thermal environment and air quality in this paper.Based on the special climate and geographical conditions of Chongqing,3 typical underground stations were selected to carry out field measurement of tunnel environment-related parameters.The dynamic change characteristics of tunnel environment of different types of stations and the factors affecting tunnel environment were obtained through analyze,and the input parameters were provided for SES numerical simulation.The result shows that tunnel structure,train departure frequency,number and location of piston air shaft are main factors affecting the piston wind.Departure frequency,tunnel structure,characteristics of piston wind,station operation life and tunnel depth are the main factors affecting tunnel thermal environment.The influence of the tunnel depth on tunnel thermal environment is greater than that of outdoor meteorology.Tunnel structure,track form,departure frequency,characteristics of piston wind and station service frequency are the main factors affecting tunnel air quality.Then the influence of location,area,length of piston air shaft and the interval tunnel length,departure frequency on single-cycle piston wind and tunnel thermal environment were discussed by using one-dimensional numerical simulation software SES.Departure frequency has the greatest influence on the single-cycle piston wind and thermal environment,followed by the area and location of piston air shaft.The length of piston air shaft has little influence on the cumulative air inflow and thermal environment of tunnel,but it has directly affects the effective air inflow.On the basis of test data,the relationship of PM concentration between inside tunnel and outside tunnel,between inside tunnel and on the platform was discussed respectively,as well as the influence of the train departure frequency,the operation of trains and the operating life of station on PM concentration in tunnel.The result shows that during daily operation period,the air quality in tunnel is not correlated with the outdoor,but is mainly affected by the the trains operation.Moreover,with the increase of train departure frequency,the PM concentration in tunnel has a higher correlation with the PM concentration outside tunnel and on the platform.Finally,the existing tunnel environment problems are divided into four categories:rush-hour effect,thermal accumulation,fresh air volume insufficient and particulate pollution according to the testing data.Based on the result of factor analysis,suggestions are put forward to improve the tunnel environment for stations already built and to be built.