Field Test On Subgrade-Culvert Transition Performance Of Ballastless Track And Subgrade FEM Analysis On Suiyu Railway

With the continuous development of the national economy,China has entered the time of increasing and high speed railway construction. The major content of China railway network planning is to build railway passenger dedicated line,and the ballastless track will be used largely.After more than ten years of research,our country has basically mastered sets of construction technology of the ballasted track subgrade engineering of high-speed railway.But for the ballastless track subgrade engineering,especially for the soil subgrade ballastless track,subgrade bed design parameter study is just beginning,which has brought new issues to our design and construction of the railway.At present,the first ballastless track comprehensive experimental section has been laid on Suining-Chongqing Railway.It is 13.157kilometers long.The slab track and double-block ballastless track,the current more mature types internationally,are laid on the experimental section.To study the operation security of the ballastless track further,the Ministry of Railways organized the comprehensive field test on Suining-Chongqing Railway ballastless track in January 2007.Integrating the comprehensive field test on Suining-Chongqing Railway ballastless track,through the test at the scene,this paper researched the slab ballastless track subgrade-culvert transition load performance and its variation rule in the direction of the railway line under the two various driving conditions(CRH2 multiple units and C80 heavy haul freight trains),and numerical calculation on dynamic response of ballastless track subgrade was also given by selecting relevant impact parameters(axle load,the material of the structure). The main conclusions are as follows:(i)Since the multiple units with the characteristics of light axle load,good performances of vehicle vibration,the dynamic stress and vibration deformation the ballastless track and subgrade structure beard was relatively smaller,and the dynamic role to the railway was not significant. Relatively speaking,the impact of heavy haul freight trains was significant and radical.Test data indicated that the dynamic stress and vibration displacement caused by CRH2 multiple units was only 1 /2 to 2/3 of which was caused by C80 heavy vehicles.(2)The use of damping ballastless track structure system is a feasible way to raise the elastic behavior of ballastless track.From the test data, we can see the vibration of the slab is 3.5 times that of the concrete base.(3)The test data showed that the concrete base dynamic stress of the culvert top was lower than that of the subgrade near the transition obviously,the slab vibration displacement of the culvert top was a little larger or not obviously less than that of the subgrade near the transition,and the concrete base vibration velocity of the culvert top was larger than that of the subgrade near the transition. The test result was quite different from the dynamics characteristics of the subgrade-bridge transition with approach slab.(4)The numerical calculation results showed that:In the ballastless track, the wheel load rail was basically shared by the five rail fasteners around it,close to the sleeper supporting force sharing ratio,which is often used in the ballasted track.But the stiffness of the ballastless track was relatively big,which would make the stress intensity.The mechanical properties of the structure layers of slab track were poor under the conditions of frictional contact than that under the conditions of coupling.The change of axle load wouldn't have an impact on the distribution rules of the vertical displacement, stress and strain of the structure layers of slab track,just only on the number.The axle load increasing,the mechanical indicators showed the increasing trend.The main load distribution extent of subgrade surface close to the length of a slab(5m),seen from the numerical calculation results calculated by using the existing conventional slab track structure size and material parameters.If the stiffness of track structure is quite different from that of the subgrade,the load distribution extent of subgrade surface would be expanded.