Research On The Dynamic Response Of Ballastless Track And Limit Value Of Uneven Settlement Subgrade

In recent years, the rapid development of high-speed railway has brought new vitality and new opportunities for railway transportation. Compared with ordinary railway, high-speed railway puts more emphasis on comfort and safety. Ballast-less track structure has obvious advantages of stability and durability of the high-speed railway due to its better stability of concrete or asphalt road bed board and a hydraulic support layer instead of ballast to transfer the traffic load. The high-speed railway subgrade as the foundation to bear the track structure and train load must have sufficient strength, stiffness, stability and durability. Under long term cyclic loading of high-speed train, soil subgrade inevitably settle, which not only restricts the upgrading of train speed, but also has a great influence on the travelling comfort and stability, as well as the track structure because of the added stress. Ballast-less track geometry adjustment ability is limited, once the deformation of subgrade settlement is beyond the adjustment, a high price will be paid to deal with the settlement. So from the perspective of dynamic interaction of the train and track, studying on the influence of uneven settlement to the vehicle and track structure is of great significance to ensure the driving comfort and safety as well as the durability of the ballast-less track structure.According to the subgrade of CRTS-II slab ballast-less track of the Beijing Shanghai high-speed railway, with the help of finite element analysis tool-ABAQUS, the coupled finite element dynamic model of the high-speed train and ballast-less track and subgrade has been established to analyze the dynamic response of the system when the train goes through the uneven settlement of subgrade sections.Studies have shown that:the ballast-less track structure above the maximum subgrade uneven settlement is easily affected by the settlement and the structure tends to broke. With the upgrading of settlement, the adverse effect on the upper structure is increasing simultaneously, which is not conducive to the stability and durability of the track structure as well as driving comfort. Under the same condition of uneven settlement, with the increase of the running speed of the vehicle, the dynamic response of the vehicle, ballast-less track as well as the interaction of both present an increasing trend. The vertical acceleration of the vehicle and the longitudinal tensile stress of supporting layer of the ballast-less track structure are the determinant factors to derive the limit value of the uneven settlement. Aiming to different speeds, the corresponding subgrade uneven settlement limits are advised in accordance with evaluation criteria. At last, some subgrade treatment measures are proposed to eliminate the adverse effects of ballast-less track subgrade uneven settlement. The conclusions in the paper can provide reference for the design, maintenance of ballast-less track structure and the treatment of the subgrade to guarantee the driving comfort and safety and durability of ballast-less track.