Study On Temperature Field And Temperature Effect Of Ballastless Track With Asphalt Concrete Layer In Seasonal Frozen Soil Area

The application of asphalt concrete layer in ballastless track structure has shown good crack resistance and waterproof sealing effect,and engineering experience from relevant test sections also indicates that it is conducive to alleviating frost heave on high-speed railways and other foundation diseases.The experience of using asphalt pavement in seasonal frozen area shows that the temperature effect of layered asphalt concrete structure is one of the key factors affecting its long-term service performance.Compared with the asphalt pavement in the same area,the temperature environment and stress characteristics of sub-rail asphalt concrete are quite different.In order to clarify the temperature effect of this new structure,it is necessary to analyze the temperature field and temperature effect field of ballastless track with asphalt concrete layer under complex climate conditions in seasonal frozen areas.In this thesis,the temperature field model of ballastless track with asphalt concrete layer was established and verified by the measured temperature data of sub-rail asphalt concrete layer from test section of Zhengzhou-Xuzhou High-speed Railway passenger line,and the influence factors of temperature field were analyzed from two aspects of thermophysical parameters and meteorological factors.Then,based on the verified temperature field model,the time-varying law and spatial distribution law applied to the temperature field of ballastless track with asphalt concrete layer in the seasonal frozen areas were analyzed.Then the coupled thermal-mechanical analysis model of ballastless track with asphalt concrete layer was established and verified by indirect coupling method,and the model is verified by the field monitoring data of the test section,and then the stress characteristics of the asphalt concrete layer under the action of thermal-mechanical coupling were analyzed.Finally,based on the verified thermal-mechanical coupling model,the influencing factors of the maximum thermal strain at structural joint were explored from three aspects,including extreme low temperature conditions,geometric parameters and material parameters through using the method of single factor analysis and multi factor analysis.The results show that the thermal analysis model established in this thesis has good applicability and accuracy.The change of meteorological parameters has greater impact on the temperature of sub-rail asphalt concrete layer than the shift of thermal physical parameters does.The temperature variation period of asphalt layer beneath the base plate is about 17.5h～22h and20h～25h later than that of the track plate surface and shoulder respectively.The coverage of sub-rail asphalt concrete layer makes the daily average minimum temperature on the surface of the subgrade bed increase about 5℃ compared with that without the asphalt layer,and the daily average temperature difference is also about 4℃ lower than that without the asphalt layer.The distribution of transverse temperature field of sub-rail asphalt concrete layer varies differently,the temperature difference between the asphalt layer under the base plate and the asphalt layer on the shoulder is about 16℃ in summer and 8℃ in winter.The internal temperature of ballastless track structure demonstrates a significant non-linear distribution along the depth direction.The thermal-mechanical coupling model established can well simulate the stress state of asphalt concrete layer in ballastless track structure.At low temperature,the temperature strain of the asphalt concrete layer at the structural joint of the base plate appears concentration.When the initial temperature is fixed,the maximum temperature strain increases 370με for every 5℃ increase in the cooling range;when the cooling range is fixed,the maximum temperature strain increases 520με for every 5℃ decrease in the initial temperature.Under the same low temperature condition,the order of the influencing factors of the maximum temperature strain at the structural joint is as follows:Linear shrinkage coefficient of base plate,thickness of asphalt layer,modulus of asphalt layer,linear shrinkage coefficient of asphalt layer,thickness of base plate and width of structural joint.The results of multi factor and single factor analysis show that the maximum temperature strain at the structural joint increases with the increase of base plate linear shrinkage coefficient,asphalt layer linear shrinkage coefficient and base plate thickness,and decreases with the increase of asphalt layer modulus and asphalt layer thickness.Although the width of the structural joint of the base plate has an effect on the maximum temperature strain at the structural joint,the amplitude of the strain change caused by its change is very small.