Study On The Dynamic Response Of High-speed Railway Tunnel With Cavities Under The Train Load

The high-speed rail tunnel in use will be affected by the dynamic load of running train,but there are few researches about the dynamic response of high-speed railway tunnel under train loads,especially the acceleration response of tunnel lining with cavities behind.This paper is supported by the National Natural Science Foundation of China——U1434211(joint fund of high speed rail).In the study on the tunnel structure of the typical double-track high-speed railway in our country,the methods field test and numerical simulation were adopted.The response characteristics of the lining arch of a tunnel with and without defects under the train vibration load were systematically studied.Further more,the vibration acceleration response of the lining arch of the high-speed railway tunnel with sickness was discussed.The research result is of great significance for reference in revealing the long term structural dynamic behavior,the evolution rule of structural damage,the precursor of catastrophic damage and in increasing the safe operation coefficient of high-speed railway with defects.The main research contents and achievements are as follows:(1)By analyzing the radar detection data,the field investigation and referring to railway related data,this paper sums up some common diseases in high-speed railway tunnels by means of mathematical statistics.At present,railway tunnel diseases generally exist in the lining vault,while the diseases are mainly uncompacted backfill and cavities.And the severe defects are more likely occur in the vaults,which provides practical data support for the focus on the further research about the vault defects.(2)In the double track tunnel,the tunnel-subgrade-track was used as the whole structure,and the acceleration test was carried out under the vibration of high-speed train.Based on the analysis of the measured data,the distribution law of the transverse acceleration and the vertical acceleration along the arch ring under a fixed train speed is given out,and also the vibration response of the lining to the side of the vehicle and the far side of the vehicle is obtained.From the frequency spectrum of lining vibration caused by each speed class train,it can be seen that at the same location,the vibration frequency of lining caused by vibration of different velocity levels is close to each other.The frequency response of the measuring point 1 is 133.125Hz~136.25 Hz with high frequency.The frequency response of measuring point 2 is 176.25Hz~190Hz with high frequency attenuation.The frequency response of the measuring point 3 is 196.875Hz~218.125 Hz.The frequency response of the measuring point 4 is 190.75Hz~231.25 Hz,and the measuring point 5 is 174.375Hz~178.375 Hz,while the high frequency vibration attenuation is obvious at the measuring point 5.When the bullet train,light engine and track inspection car at different speeds pass through the tunnel,the main acceleration frequency of lining is between 130Hz~230Hz,and the frequencies below 200 Hz are easy to pass.(3)The application of solving method of dynamic load in ABAQUS finite element software was briefly introduced,and the input mode of load was carried out by using classical train load formula.Based on the measured wheel-rail force and frequency spectrum analysis,the control value geometric irregularity of track of calculation formula was modified to control the track irregularity of tunnel line and to compensate for the shortage of measured load,which reduced the frequency error caused by using classical formula in the model,calculation,and to make the model closer to the actual load,making the calculation of model load more close to reality.(4)Based on ABAQUS software,the two-dimensional finite element model was used to simulate the vibration response of arch structure under the train load and to analyze the vibration response of arch ring with cavities or without cavities behind lining.The model calculation results are in good agreement with the experimental results,and the applicability of the model parameters is verified.The transfer law of the acceleration response of the lining arch rings with cavities or without caviyies behind was got,and the influence of the train speed on the acceleration response of the lining arch with cavities in the same size behind the lining was obtained.Besides,the influence of different cavity sizes on the acceleration response of arch ring at the same train speed was acquired,which showd the most unfavorable size of cavities.(5)A three-dimensional finite element model of tunnel was established,and the acceleration responses of linings without cavities,with parallel cavities and with misplaced cavities were studied.The results show that the parallel cavity has more influence on the vibration response of tunnel lining.Further more,according to the model with parallel cavity,the acceleration response of lining was studied by considering the cavity length,width and distance.At last,the most unfavorable condition for the influence of cavity length,width and distance on the acceleration response of the lining arch was obtained.