Leaching Damage Characteristics Of Double-Block Ballastless Track Under Water Environment

With the large-scale operation of high-speed railway,the damage detection and disease repair of ballastless track has gradually become a hot issue to be solved.The premise and foundation to solve the above problems is to clarify the formation mechanism of various diseases of ballastless track.In the area with abundant rainfall,the double-block ballastless track is bound to be leached by water for a long time,which leads to the deterioration of the performance of the track slab and the supporting layer,and causes the change of the mechanical properties of the ballastless track structure,especially the interface between the sleeper and the track slab,under the action of train load and temperature load.Therefore,to explore the leaching damage characteristics of double-block ballastless track under water environment,to clarify the deterioration law of ballastless track materials,and to analyze the difference of local mechanical properties of ballastless track before and after leaching,has certain practical significance for enriching the water induced damage theory of ballastless track and improving the understanding of ballastless track durability.In this paper,based on the leaching of concrete mechanism,combined with theoretical model and laboratory test,the leaching damage characteristics of double-block ballastless track are studied.Based on Fick’s law of diffusion and mass conservation law,the control equation of calcium ion diffusion transport is derived.Combined with the solid-liquid equilibrium curve,porosity and diffusion coefficient evolution equation,the numerical analysis model of concrete calcium leaching is established,which is solved and verified by finite element software.The calcium leaching model of double-block ballastless track is established,and the spatial distribution of calcium ion concentration,solid calcium concentration and porosity with the leaching time of track slab and supporting layer are compared and analyzed.The results show that the leaching depth of the track slab is smaller than that of the supporting layer,but the porosity changes greatly,and the initial material parameters have a great influence on the leaching process of concrete.Based on the mix proportion parameters of track slab,the accelerated leaching test of concrete is carried out.The results show that there is a good linear relationship between the leaching depth and the square root of the leaching time,which verifies the correctness of the theoretical model of calcium leaching.A large number of white powdery substances appear on the surface of concrete after leaching,and there are many small depressions on the surface after washing.After leaching,the compressive strength and splitting tensile strength of concrete decrease in varying degrees,and the splitting tensile strength is more significantly affected by leaching.The spatial finite element solid model of double-block ballastless track is established to analyze the mechanical characteristics of the interface between sleeper and track slab before and after leaching under train load and temperature load.The results show that: under the train load,the stress at the midpoint of the long side of the interface bottom increases significantly after leaching.The maximum principal stress of interface increases by 26.9% and 10.5% respectively under positive and negative temperature gradient loading after leaching.