Mechanical Response Analysis Of Asphalt Pavement Structure Based On Actual Tire-pavement Contact Pressure,Layer Interfacial Bonding And Viscoelastic Condition

In the design and analysis of asphalt pavement structure,it is the foundation and precondition to accurately grasp the mechanical response of asphalt pavement structure.There are many factors that affect the mechanical response of asphalt pavement,such as structure combination of pavement,material properties,temperature and humidity of environment,size and distribution of tire load,inter-layer contact conditions and so on.So,in order to accurately grasp the mechanical response of asphalt pavement structure,it is necessary to apply reasonable material constitutive relation,tire-pavement contact pressure,and inter-layer contact condition,etc.Whatever,the design and analysis of asphalt pavement structure at present,on the one hand,or assuming the distribution of tire load is circular uniform,or that the asphalt mixture is assumed to be linear elasticity,or that the inter-layer interface is assumed to be either completely smooth or completely continuous.On the other hand,ignoring the temperature change of asphalt pavement structure in the depth direction and the effect of temperature field in the structure is not considered.It is well known that the stress-strain characteristics of asphalt mixtures vary greatly with temperature.In order to accurately grasp the mechanical properties of asphalt pavement structure,on the basis of considering the actual load,the contact characteristics of inter-layer interface and the viscoelastic constitutive relation of materials,combing with the effect of temperature field in the asphalt pavement structure,this paper analyzed the stress response of asphalt pavement structure with the help of general finite element software.In the finite element modeling,the 95 viscoelastic parameters of asphalt mixture are needed,therefore,this research with the aid of UTM testing machine,got dynamic modulus of different asphalt mixture that used firstly,and calculated the storage modulus according to dynamic modulus,finally obtained the viscoelastic parameters of these asphalt mixture by the relaxation modulus.After a lot of calculations and analysis,the following basic conclusions as follows:(1)It is different of modelling factors between commonly elastic layered system and viscoelastic finite element system in this paper,the difference in mechanicalresponse is brought about,so the failure modes of two pavement structure under the two modelling are different,and researching on mechanical properties of pavement structure under elastic layered system is too simple.(2)In the same pavement structure,compared to the immediate layer and bottom layer,the top layer of asphalt pavement bears most of the strain,which is likely to be pressure or shear failure firstly,so the function of the top layer is very important.(3)The influence of pavement structure thickness on mechanical response of pavement structure is very complicated.Within the scope of the conventional asphalt layer thickness,increasing the thickness of asphalt layer can improve the mechanical properties,at the same time,that also can increase the tensile stress of bottom layer,but the change of the thickness has little effect on the rutting contribution rate of asphalt pavement.(4)The influence of temperature on mechanical response of pavement structure is greatly,especially in the higher temperature condition,the pressure strain and tensile strain of the surface layer are very large,which is very likely to be damaged by compression and tensile failure.As the temperature rises,the rutting contribution rate of the top layer will gradually increase.When the temperature in the pavement structure is 54?,the rutting contribution rate of the top layer reaches to 70%.(5)The mechanical response of pavement structure is significantly influenced by pavement materials.The top layer used modified asphalt can improve the high temperature performance of the top layer obviously,reducing the rutting contribution rate of the top layer and the total strain of asphalt layer greatly.Based on the top layer using modified asphalt,the immediate layer used asphalt joined 35% sulfur,which also can improve the high temperature performance of immediate layer significantly,reducing the rutting contribution rate of the immediate layer and the total strain of asphalt layer greatly.(6)Under the different temperatures and different material combinations,the different contact conditions between asphalt layer have little effect on the rutting of asphalt pavement and rutting contribution rate of asphalt layer,but the influence on tensile stress of bottom of asphalt layer and the maximum shear stress is very great.When the contact between layers is well,it can greatly reduce the tensile stress andmaximum shear stress of bottom of asphalt layer,especially,which can reduce the mutation of maximum shear stress of contact surface between the two layers,so it can improve the stress state of contact between the layers and reduce the possibility of tensile and shear failure in the inter-layer.When the contact of inter-layer and the bonding between layers are not good,the tensile and shear failure between the asphalt layers are strengthened.