Transfer Mechanism And Model Research On The Chloridion In Ballastless Track

As the main material for constructing the ballastless track structure,reinforced concrete is exposed to the atmospheric environment.Under the long-term erosion of the chlorine environment,durability problems such as steel corrosion and concrete protective layer peeling will inevitably occur.According to the different parts of the ballastless orbits eroded by chloride ions,it can be divided into two states: saturated and unsaturated.At the same time,there is cracking in the ballastless track,and it is under the train load for a long time.Therefore,the study of chloride ion erosion needs to consider the two cases of crack and fatigue load.Therefore,the transport of different types of chloride ions in concrete was studied;the chloride ion transport model under saturated and unsaturated conditions was established;the transmission mechanism under the coupling of fatigue load and chlorine environment was explored and the effect of cracks on the transport of chloride ions in concrete was analyzed.The main research contents are as follows:(1)The transport mechanism of chloride ion in saturated concrete was studied.The chloride ion diffusion model in saturated concrete was established.The model is applied to the CRTS I type double-block ballastless track,and the distribution of chloride ion content in the crack and interlayer gap between the sleeper and the variation of chloride ion content in the longitudinal reinforcement under different layers were analyzed.(2)The chloride ion transport test in saturated concrete under fatigue loading was carried out,and the relationship between chloride porosity and volumetric strain and the diffusion coefficient of chloride ion under fatigue load was established to establish the calculation model of chloride ion transport under fatigue loading.The finite element software COMSOL was used to couple the solid mechanics field with the dilute material transfer field,and then the model calculation results were obtained.The erosion law of chloride ion in concrete under different stress ratios and erosion time was analyzed.(3)The chloride ion transport model for saturated concrete with cracks was established,and the diffusion of chloride ions under different crack widths,crack depths,crack spacings,and crack orientations were analyzed.(4)The water transport model and a chloride ion transport model in unsaturated concrete was established and the model was solved by using finite method and MATLAB.The relationship between convective zone depth,peak chloride ion concentration,erosion depth and dry-wet cycle was analyzed.the chloride ion transport law under different dry-wet cycle systems,different initial saturations,different external temperatures and different external chloride ion concentrations was studied.