Analysis Of Anchorage Reliability Of Type ? Sleeper Spiral Nail Based On Mesomechanical Method

The research work in this paper is carried out under the background that the high-speed rail ballastless track is in the early stage of construction and the durability research of concrete sleeper is still lacking.Based on the analysis of the concrete sleeper damage,combined with the structure,working environment and other characteristics of the type III sleeper,the deterioration mechanism and the law of the key local structure of the sleeper under various factors are explored,aiming at providing a basis for durability design of China's high-speed railway ballast track.The main contents are as follows:(1)The meso-mechanics method is introduced into the research of concrete sleepers.A three-dimensional random aggregate meso-scopic model suitable for sleeper concrete is established.Based on the existing modeling method of random aggregate model,a new method of controlling the shape of aggregates is proposed.(2)Based on the chloride ion diffusion mechanism and theory,a random aggregate model is used to simulate the chloride ion diffusion behavior of the sleeper,and then the chloride ion diffusion law of the sleeper concrete under different conditions is discussed.The results of the numerical simulation are regressed and analyzed,and the functional relationship between chloride concentration near the screw spike and boundary chloride concentration,erosion time,concrete internal defects are determined.(3)Combining with the basic theory of steel corrosion expansion,the prediction model of screw spike corrosion quantity is deduced,and then the corrosion pattern and corrosion distribution of screw spikes are given.From the microscopic point of view,the representative volume element method is used to establish the meso-mechanical model of the pull-out force of screw spikes,and then the factors affecting the anchorage strength of the screw spikes are studied.Finally,the functional relationship between the anchorage strength of screw spikes and boundary chloride concentration,concrete internal defects are determined.(4)Based on the theory of reliability,for the functional failure of the sleeper structure,the factors affecting the anchorage reliability and the structural resistance are analyzed and calculated.The functional reliability of the key local structure of the sleeper is also calculated.