Study On Mechanical And Deformation Characteristics Of CRTSⅢ Slab Ballastless Track Under Complicated Temperature

China has a vast territory.High speed railway(HSR)passes through a variety of climate from north to south,wherefore the temperature of service environment for ballastless track is complex and changeable.The large-scale operation of HSR in China has illustrated the complicacy of the relationship between mechanical characteristics of the ballastless track and temperature within past decade.The CRTS III slab ballastless track is a new type of the ballastless track structure developed by China,which integrates the advantages of all sorts of ballastless track structures and is now extensively used in domestic HSR,confronted with multiple temperature challenges.Hence,in view of the current operating status of CRTSIII slab ballastless track,this paper investigates temperature effects of the ballastless track taking the influence of complex temperature into account,and discusses the mechanical,deformation characteristics and the damage of CRTSIII slab ballastless track development and evolution,which has theoretical significance and engineering value.On account of the concrete damage plasticity theory,this paper establishes the linear elastic constitutive model and damage plastic constitutive model of CRTSⅢ slab ballastless track.A variety of temperature loads are applied to simulate the actual environment temperature,to analyze the mechanical,deformation and damage characteristics of ballastless track.The research of this paper are summarized as follows.(1)Based on the concrete constitutive relation and concrete damage plasticity theory,the concrete material parameters of the ballastless track components for modeling are deduced.By means of the finite element software,the elastic and plastic static analysis models of CRTSIII slab ballastless track are established.The integrate temperature,temperature gradient and extreme high temperature loads for models are determined and the coupling of the train loads and temperature loads is considered.Thermal stress analysis model is established,and combined with the field test data,variable temperature curves are confirmed,which is applied to the thermal stress analysis model of ballastless track.(2)On the basis of the linear elastic model and damage plasticity model of the ballastless track,the mechanical and deformation characteristics of slab,self-compacting concrete layer and the base plate are analyzed.Under integrate temperature loads,the stress in the recess of the base plate is relatively large.Although no damage is caused in the track,the elastic cushion is easily damaged due to the cyclic loading.When the positive temperature gradient reaches 40℃/m,the corners of the self-compacting concrete layer begin to crack.The cracks easily happen at the corners and edges of the self-compacting concrete layer under the temperature loads extracted from test data.Under the effect of the coupling of temperature loads and train loads,the stress concentration is likely to occur around the position of the train loads,and the force and deformation of the track structure increase;When the integrate temperature reaches 50℃ and the positive temperature gradient reaches 100℃/m,the base plate occurs cracks.(3)In view of the damage plasticity model,the damage characteristics of the ballastless track are analyzed.When the positive temperature gradients reach 40℃/m and 80°C/m,damages may be observed in the corners and bulgy blocks of self-compacting concrete layer.Under temperature loads extracted from test data,the damage occurs in the corners and the edges of self-compacting concrete layer.Under coupling of the temperature loads and train loads,the position of slab track under train loads is easy to damage due to the stress concentration.Compared with the positive temperature gradient,the coupling of negative temperature gradient and train loads makes the damage of the ballastless track more serious with relative concentration of distribution.(4)In the light of the field investigation and theoretical analysis results of CRTS Ⅲslab ballastless track,the mechanical and damage characteristics of CRTS Ⅲ slab ballastless track are researched,setting the failure of the elastic cushion at the recess of the base plate and the shrinkage of self-compacting concrete as initial damage conditions.Under the condition of failure of the elastic cushion,the damage of the base plate begins to occur.The self-compacting concrete shrinkage causes the damage of the self-compacting concrete to intensify,and parts of it is completely destroyed.To explore the measures to reduce the temperature effect of the ballastless track,taking the coating material into consideration,smearing the coating material can effectively reduce the temperature forces of the ballastless track,delaying the occurrence of damage and reducing the degree of damage.