Model Test Study Of High Temperature Stability For Longitudinal Connected Ballastless Track

With the rapid development of high-speed railway transportation,a variety of problems arised during the service process of ballastless track,one of the most prominent is the damage of ballastless track in extreme climate.Extreme climate often makes ballastless track suddenly bear temperature load beyond the design range,resulting in the sudden occurrence or development of track damage,which seriously affects the high-speed driving safety.This paper is aiming at the longitudinal track arch which is one of the typical diseases of ballastless track,based on field investigation,using similarity theory to design and manufacture the similar model,analyzed the effect of high temperature on the vertical stability of the longitudinal track through theoretical calculation,modal test and model test of temperature rise.First of all,the model test scheme of vertical stability of longitudinal connected track at elevated temperature is designed through similarity theory and the longitudinal track model is built based on field investigation and the existing stability research of the longitudinal track.Secondly,influence of transverse crack on the surface and tip displacement of the model in the heating test were studied through model test and theoretical calculation aiming at the longitudinal displacement of the track plate in the heating test.Research shows that the cracks have great influence on temperature force of longitudinal connected track and should be completely closed before heating test,tip displacement have little effect on the test results when the bottom of track plate is under frictional resistance and drain temperature force when the bottom of track plate is under bond strength.Then,modal of the model track plate was measured by hammering test to analyze the change of first order natural frequency and first order vibration mode of the track plate.The results show that the first order natural frequency decreases with the increase of the end force.By inference,when the end pressure is 1240kN which is heating 179 degrees to the track plate that the track plate reach the critical state of vertical instability.The heating amplitude is much larger than temperature amplitude that is possible.There is little possibility for the track plate to reach the critical state of vertical instability.First vibration mode of the track plate is changed from 1 peaks into 3 peaks after putting pressure at the end of the track plate.It can be seen that crack will affect the first vibration mode of the track plate.Finally,influence of high temperature on the vertical stability of longitudinal track is studied by heating test.The results show that crack will affect the deformation of the track plate after putting pressure at the end.Arch chord of the model track is 3 meters and arch chord of the real track is 15 meters.Too large temperature of heating plate will make too large vertical temperature gradient of the track plate.It is suggested that the difference between temperature of the heating plate and surface temperature of the track plate is controlled at 30 centigrade,and the maximum difference is not lager 50 centigrade.Arch deformation of longitudinal track with crack is essentially a deformation under the action of temperature load and crack.