Research On Smoothness And Fatigue Life Of High-speed Railway Rails Under Subgrade Frost Heave

In recent years,high-speed railways have been built on a large scale in seasonally frozen soil areas.In order to ensure the planning and the operation safety of high-speed railways,the problem of subgrade frost heave should be focused on.Subgrade frost heave will cause many negative effects on the track structure,which is not conducive to maintaining the smooth state of the track.The rail is one of the important components of the railway track,which mainly guides the wheel to travel forward and transfers the pressure of the wheel to the sleeper.At the same time,as the speed of rail increases,the fatigue failure of rails cannot be ignored.Reasonably predicting the fatigue life of rails under subgrade frost heave is of great significance to ensure the safety of the line and guide the scientific maintenance of the rails.Therefore,the paper uses the finite element analysis combined with the indoor frost heave test to explore the mapping relationship between the subgrade frost heave parameters and the smoothness of the track,evaluate the fatigue life of the rail under the subgrade frost heave.The main research contents and results are as follows:(1)Take the subgrade soil along the Harbin-Dalian line to conduct a one-way freezing test,control the three variables of cooling gradient,initial moisture content and compaction degree,and analyze the soil temperature field and frost heave rate.The results show that with the decrease of the ambient temperature,the temperature of each layer of the soil sample decreased slowly,then entered the rapid cooling stage,finally stabilized with the extension of time.The greater the soil sample cooling gradient,the higher the initial moisture content,the greater the compaction degree,and the faster the cooling rate;the smaller the soil sample cooling gradient,the higher the initial moisture content,the greater the compaction degree,and the greater the frost heave rate.(2)Use the ABAQUS finite element software,establish the CRTS I-type slab ballastless track-subgrade model,and calculate the mapping relationship of the rail irregularity under single-wave subgrade frost heave.The results show that if the frost heave position appears in the middle of the track slab,the rail smoothness is poor.When the location and amount of frost heave are constant,the smaller the wavelength of frost heave,the greater the changing rate of rail irregularity;when the location and wavelength of frost heave are constant,the greater the amount of frost heave,the greater the changing rate of rail irregularity.(3)Combined with the metal fatigue theoretical method,evaluate the fatigue life of a rail in the middle of the track,and calculate the residual life of the rail according to the Paris formula.The results show that whether frost heave affects the fatigue life of rails.The predicted fatigue life of the rail increases with the amount of frost heave.The increase trend first decreased and then increased;with the increase of frost heave wavelength,it first increased and then decreased.The larger the frost heave amount,the smaller the frost heave wavelength,and the smaller the remaining life of the rail.In order to improve the unevenness of the rails,the railway work department should grind the rails in time when the fatigue life of the rails does not decrease significantly.