Under Complicated Load Curve Section Of Roadbed In Double Block Without A Frantic Jumble Rail Fatigue Characteristics Research

Double-block ballastless track on subgrade is a main ballastless track structure on subgrade. It is widely applied in a number of high speed passenger lines in our country, including Wuhan-Guangzhou passenger dedicated line and Zhengzhou-Xi’an passenger dedicated line.At present, at home and abroad people have carried out some researches on the fatigue characteristics of double-block ballastless track on railway subgrade, but most to the straight double-block ballastless track, without considering that curve section’s un-balanced superelevation and wheel/rail lateral force of vehicle’s guidance etc will bring fatigue characteristics of curved double-block ballastless track negative influences.So,the fatigue characteristics findings of double-block ballastless track on subgrade at home and abroad also have certain limitations and no longer fit for the requirement of curved double-block ballastless track designing in our national high-speed railway. In order to provide better service for our national high-speed railway designing,it’s imperative to carry out deep research in the fatigue characteristics of curved double-block ballastless track in high speed railway.For this reason, on the basis of absorbing the research achievements home and abroad, considering the time-varying characteristics and dynamic coupled action of every load in curved double-block ballastless track during service period, it established theoretical model of stress spectrums for curved double-block ballastless track on railway subgrade under complex loads during service period in this paper;combining Miner linear damage accumulation theory and the S-N curves of steel bar and concrete, it also established the fatigue life prediction model for curved double-block ballastless track on railway subgrade under complex loads during service period.And, take climatic conditions of Changsha area as an example, the fatigue failure characteristics of curved double-block ballastless track on railway subgrade under complex loads during service period were studied by this fatigue life prediction model;the effects of different superelevations of outer rail on curves、different thicknesses of slab、 different ratios of reinforcement of slab、different thicknesses of supporting bed、different modulus of elasticity of supporting bed、 different construction temperatures on the fatigue life of curved double-block ballastless track on railway subgrade were studied.The conclusions are as follows:fatigue lifes of the concrete and steel bar in slab of curved double-block ballastless track on railway subgrade under complex loads are decreased with the superelevations of outer rail on curves increase, but they will increase with the thicknesses of supporting bed increase; with the modulus of elasticity of supporting bed increase, fatigue life of the slab concrete are decreased, fatigue life of steel bar increases; with thicknesses of slab increase, fatigue life of the slab concrete increases, fatigue life of steel bar is decreased, their fatigue lifes will be balanced when the thickness of slab is0.25m; fatigue lifes of the concrete and steel bar in slab increase with ratios of reinforcement of slab increase, but decreasing ratios of reinforcement has more significant influence on fatigue lifes of the concrete and steel bar in slab than increased ratios of reinforcement;fatigue lifes of the concrete and steel bar in slab are decreased with the construction temperatures of the slab concrete increase. According to the specific construction environment, the highest construction temperature of the slab concrete of double-block ballastless track on subgrade could make an appropriate reduction.Research results can provide reference for enriching and improving theories standards our national ballastless tracks.