Study On The Structure Mechanics Response Of Asphalt Pavement Based On Moving Load And Continuous Variable Temperature Condition

Main diseases of asphalt pavement includes high temperature rut,low temperature crack and fatigue crack,etc,these are closely related to the temperature and load.Pavement damage is caused by more than the limits of the load applied,the change of temperature stress and vehicle load are main source of stress.In-depth analysis of characteristics of asphalt pavement deformation under temperature field change and the dynamic load is great significance to reveal the disease mechanism.In this paper,establishing three-dimensional finite element model of semi-rigid base asphalt pavement by ABAQUS software,from the perspective of continuous change of temperature、moving load,calculation of continuous variation of the temperature field、temperature stress and deformation of the pavement structure layer under dynamic load,in further to analyze the law and mechanism of rut,crack extension,the main content of paper is summarized as follows:（1）In order to study the influence factors of rule that the temperature field of asphalt pavement changing with environment temperature,choosing regular summer high temperature and three winter low temperature in 24 h a day,so as to calculate the pavement structure layer continuous variation of the temperature field and temperature stress.Through changing thermal physical parameters of asphalt mixture at surface（solar radiation absorptivity,thermal conduction coefficient,heat capacity,emissivity）,analyzing rule of the high temperature field varying with thermal physical parameters and the relationship between the elastic modulus、shrinkage coefficient and low temperature stress.Research shows that reducing pavement thermal conductivity and Solar radiation absorption rate,increasing heat capacity and surface emissivity,can decrease the high temperature of asphalt pavement structure during the day time.At the same temperature field,if the modulus of asphalt mixture and temperature shrinkage coefficient increase,the temperature stress increases in linear.（2）through applying moving load on load belts of semi-rigid base asphalt pavement structure 3 d simulation model by subroutine Dload and Utracload,to analyze the rule that brake force coefficient、temperature field and speed、contact stress influence on the deformation and stress.Brake force exerts significantly changing the internal longitudinal stress S13,S23,S33 of asphalt pavement structure,schedule change of longitudinal deformation U3 is increased with the increase of brake force.Under moving load,the stress of the pavement structure increases linearly with speed decreased and contact stress increased.（3）Applying way of"waiting for moving"load,inputting 1 day 24 hours continuous variation of high temperature field calculation results into the semi-rigid base asphalt pavement 3 d model,selecting each layer of asphalt pavement vertical deformation、compression creep、shear creep as calculation rut index.Analysis of rule that speed,temperature,contact stress factors influence on rut index,within the scope of asphalt layer 4--10 cm（surface）is high compressive creep and shear creep value area.By orthogonal analysis,temperature is the most significant factor impact on asphalt pavement rut,followed by contact stress and speed.Study from the view of material thermal physical parameters,reducing pavement thermal conductivity and Solar radiation absorption rate,increasing heat capacity and surface emissivity,can reduce rut of asphalt pavement structure.Solar radiation absorption rate,heat conduction coefficient,heat capacity have significant effects on rut index,the solar radiation absorption rate affects the most significant.More attention on the material will be changed in solar radiation absorption and thermal conductivity in asphalt mixture design.Putting forward conduction coefficient decreased within the range 5000 J/m?h?℃,heat capacity increased from 500 J/kg·℃to 1500℃,J/kg,the solar radiation absorption rate reduced from 0.9 to 0.5,the vertical deformation,shear creep,compressive creep of each layer will decrease,the conclusion can guide the material design of asphalt pavement.（4）Under the action of temperature and load,cracks in asphalt pavement extends deeply,the performance of pavements weakened.Respectively longitudinal surface crack is set in the inside edge of the wheel load,transverse surface crack is set in cross section.Crack tip stress intensity factor under dynamic load is obtained by using the stress extrapolation method,and further calculae the equivalent stress intensity factor of crack tip.Analysis of the rule between the brake force,the transverse、temperature field、contact stress and crack stress intensity factor and equivalent stress intensity factor of longitudinal and transverse surface crack.Fitting equation of different crack length and equivalent stress intensity factor is to predict the fatigue life of pavement by the Paris formula,then compare different influence factors affect on fatigue life of cracked pavement.The results show that:Brake force has little effect onK_I、K_II,which of the inside edge of the wheel track longitudinal top-down crack,butK_III increases obviously with brake force increased.K_I、K_II、K_{II I}、K_eff-maxof the inside edge of the wheel track longitudinal top-down crack,K_I、K_II、K_eff-maxof transverse top-down crack,all of these increase with the loss of temperature,increase with contact stress increased.Temperature has more significant influence on crack tip stress intensity factor.The fatigue life of asphalt pavement with longitudinal and transverse cracks reduces when brake force,contact stress increased and temperature field reduced.In winter,low temperature has the largest damage to fatigue life,the second is stress contact,the minimum is brake force.Longitudinal cracks on the edge of the inside of the wheel track not only bears the shear stress along the crack surface,but also bear tear shear stress,equivalent stress intensity factor of longitudinal crack is greater than which of the transverse crack,so longitudinal crack has less fatigue life than transverse crack.