Study On Distribution Law Of Temperature And Temperature Sress And Control Measures Of Ballastless Track Of Railway In Northwest China

In today's railway construction,the traditional gravel track bed is used to be replaced by the monolithic track bed of ballastless track in some sections,which improves the smoothness of the track and reduces the daily maintenance works.However,temperature stress that is brought by the temperature change under the impact of sunlight and air temperature change occurs in the monolithic track bed since the monolithic track bed is directly exposed to the external environmental conditions and the track bed has smaller volume-surface ratio and lower thermal conductivity.Therefore,this paper studies the temperature and temperature stress distribution laws of the monolithic track bed in the northwest region under complex temperature conditions based on the actual climate and environmental conditions in the northwest region of China,then the corresponding control measures is researched.The main research contents are as follows:(1)According to the related data,the actual cracking condition and cracking mechanism of monolithic track bed in Northwest China is researched and analyzed,the formation mechanism and development process of the temperature disease of monolithic track bed is analyzed,the meteorological characteristics of the Northwest region and its possible impact on the bed are clarified,and the research ideas of the monolithic track bed temperature field and temperature stress distribution and stress control measures are pointed out.(2)A new theory that can be applied generally to calculate temperature stress of sleeper end of ballastless track on monolithic track bed is raised by analyzing the theory and hypothesis of mechanics,combining the type of experimental apparatus,and considering the effects of concrete creep,stress relaxation and strain gauge self-deformation on the monolithic track bed.Then the thermal stress calculation formula was deduced and the thermal stress calculation of monolithic track bed is carried out during the test.(3)The horizontal and vertical temperature distribution of the monolithic track bed is analyzed through using the full track bed full-scale model,embedding the temperature sensors in model,and collecting the data of sensors.Then the effects of modified materials on monolithic track bed temperature distribution during the stage of concrete setting and hardening to the concrete age of 180 d is studied by blending the steel fiber,graphite powder and carbon fiber with the volume fraction are 1%,3%,and 0.2% respectively into concrete.(4)The development process and distribution laws of temperature strain and stress at the sleeper end and center of monolithic track bed during the stage of concrete setting and hardening to the concrete age of 180 d are analyzed by integrating the collecting data of temperature sensors and concrete strain gauges.And the effects of different stress control measures like modified materials and chamfer polishing on the temperature strain and stress of the corresponding position on the monolithic track bed are studied.(5)The working mechanism of modified materials in the prevention and control of monolithic track bed temperature diseases are clarified by analyzing strength changes of same condition test blocks of ordinary concrete and modified concrete,combining the monolithic track bed cracking conditions which are observed in different test areas during the test,and integrating the analysis results of temperature distribution and temperature stress,and then the ideal control measures of monolithic track bed temperature disease were obtained.