| The disease of mountain tunnel in our country is serious,especially in the tunnel base.According to the investigation,One of the main causes of the tunnel base disease is the reciprocating vibration and impact of train load.With the increasing demand of freight transportation in our country,the relevant departments will gradually increase the frequency of freight trains or the axle load.However,this change will directly lead to the increase of the vibration and impact force of the tunnel basement rock under the train load.On the other hand,in the process of construction of heavy haul freight line,there are some disputes about the selection of ballast and ballastless track.In order to solve these problems,it is necessary to study the propagation law of train vibration in tunnel and basement rock,and study how axle load,vehicle speed and different tracks affect the law.This study can provide reference for the prevention and treatment of the tunnel base disease and the selection of track.Based on the engineering background of Huo Jialiang tunnel in Shen Shuo line,the law of effect on rail,sleeper,tunnel wall and surrounding rock by axle load and base diseases are analyzed by comprehensive use of data research,situ measurement,numerical analysis and other means.Furthermore,the dynamic response laws of the tunnel basement rock under different axle load and vehicle speed conditions are analyzed and compared under ballast and ballastless track.The main research contents and conclusions are as follows:A vibration measurement was carried out in Huo Jialiang tunnel and the measured data of the vibration source was obtained and the vibration response characteristics of the track and tunnel was analyzed when different axle load trains cross through the normal(without disease)and the disease section.Conclusions show that the vibration response of the tunnel base increases with the increase of axle load,besides,increasing phenomenon is more obvious on 10Hz following and 50-1000Hz frequency band.With the increase of axle load,the vibration response of sleeper is enlarged on the 1-200Hz frequency band,and the rail vibration response is enlarged in 1-50 and 70-500Hz frequency band.The vibration response of the basement,tunnel wall and sleeper is increasing with the base disease.In the frequency domain,the frequency bands of these three increasing responses are 150-400Hz,100-330Hz,1-200Hz.Track-tunnel-soil three-dimensional dynamic finite element model was established according to the actual condition of Huo Jialiang tunnel.Using the measured data to check the method of model element division and boundary processing.Then the tunnel basement rock vibration effect range of Huo Jialiang was analyzed by this model.The results show that the effect range of the 27t axle load on the base rock was 10m range.The two indexes of the vertical stress and the acceleration value of the rock mass were used to carry on the follow-up research.Track-tunnel-soil three dimensional dynamic finite element model consisted of ballast and ballastless track was established by using the above modeling method.The effect law of axle load and vehicle speed on the dynamic response of the basement rock is analyzed by comparing the two types of ballast track and ballastless track.The results show that for the same position of basement rock under ballast track,vertical stress and effective acceleration values are less than the ballastless track,and the effective acceleration value and the peak value of the vertical stress of the basement rock under the ballastless track are more sensitive than ballast track to the change of the axle load,so in the same location with same rock grade,ballast track should be given priority for the construction of heavy haul railway in view of train vibration.With the increase of axle load,the vertical stress and effective acceleration values of the basement rock under the ballast and ballastless track are increasing,in other words the possibility of the occurrence of basement rock disease is greatly enhanced. |
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