Research On Mechanical Behavior Of Asphalt Pavement Structure Under Complex Heavy Loads

With the continuous improvement of highway traffic facilities and vehicle equipment in China,highway traffic is developing toward rapid and heavy loading,and the phenomenon of high speed and heavy load of heavy trucks are becoming more and more serious.Therefore,the research on the mechanical behavior of asphalt pavement structure under heavy loads is an urgent need in the field of road engineering and highway construction management.In the analysis of the mechanical behavior of many asphalt pavements,it is assumed that the road is subjected to quasi-static vertical uniform load,which deviates greatly from the complex contact stresses of the real road which is subjected to dynamic three-way non-uniform load.At the same time,researchers in the domestic and overseas have not deeply studied the structural mechanical behavior of asphalt pavement under complex heavy loads from the perspective of the longitudinal pattern and highly nonlinear characteristics of truck tires.Aiming at the shortcomings in the study of the highly nonlinear and spatial characteristics of complex contact stresses of longitudinal pattern tire,the dynamics theory of automobile system,the steady-state rolling analysis method of the tire,the dynamics analysis theory of asphalt pavement,and finite element analysis method were comprehensive application.Three-dimensional finite element models of longitudinal pattern tire of trucks,the structure of asphalt pavement,and temperature field were established respectively.The influence of thermal physical parameters of asphalt surface materials on temperature field was revealed,and the spatial distribution characteristics of contact stresses under typical working conditions and different parameters were deeply studied.Then the dynamic response of asphalt pavement and the rule of rutting change under complex heavy loads were predicted and analyzed.In the first instance,three-dimensional finite element models of longitudinal pattern tire,the structure of asphalt pavement and the temperature field of the pavement were established.According to the theory of vehicle system dynamics,tire dynamics and finite element method,aiming at modeling the highly nonlinear characteristics of longitudinal pattern tire 275/70R22.5,the complete three-dimensional finite element model of tire was established,and the nonlinear modeling method of truck tire was studied.The viscoelasticity material parameters of asphalt mixture were tested by the MTS Landmark test equipment,and the three-dimensional finite element model of asphalt pavement structure was established based on the actual measured parameters.The accuracy of the tire-pavement contact model was verified by finite element analysis and measurement by the tire-pavement load testing system.Then the temperature field model of asphalt pavement was established,the temperature fields at different time and depths were analyzed and calculated,and the influencing factors of the temperature fields of asphalt pavement were discussed.Secondly,the spatial distribution characteristics of contact stresses under different typical working conditions were obtained based on the mixed Lagrange-Eulerian method and steady-state transport analysis.In view of the steady contact problem,the steady-state condition of the three-dimensional finite element model of the longitudinal pattern tire was defined.Combined with the dynamics theory of the tire,the steady-state rolling contact problem was described mathematically,and the finite element analysis process of steady-state rolling contact problem was proposed.The developed tire-pavement contact model can accurately predict the complex contact stresses under different working conditions.The influences of different parameters and typical working conditions on the complex contact stresses of the tire-pavement were researched and analyzed,and different typical spatial distribution characteristics of contact stresses under working conditions were revealed.Then,the dynamic responses of asphalt pavement structure under complex heavy loads were predicted and analyzed.According to dynamic analysis theory and the dynamic equilibrium equation of the asphalt pavement structure,the complex contact stresses and the changing temperature field of the asphalt pavement structure were considered,the Dload and Utracload subroutines were used to realize the movement of complex contact stresses,and the finite element analysis model of transient dynamics of asphalt pavement under the contact stresses of the three-direction dynamic movement was established,that focused on the analysis of the influence of different driving conditions,tire loads,temperature fields,driving speeds and other factors on the deformation and strain.Finally,the rutting analysis process of asphalt pavement structure under complex heavy loads was proposed.Through comparative analysis,the rutting performance analysis and evaluation index under different typical working conditions were determined.The rutting prediction analysis of asphalt pavement structure was carried out by introducing the changing temperature field,and the influence of different speeds,tire loads and changing temperature environment on the vertical permanent deformation and compression creep under free rolling condition and the vertical permanent deformation and compression creep under full braking condition were analyzed.Combined with the orthogonal test method and mathematical statistics method,the range analysis and variance analysis were applied to quantify the primary and secondary and significant characteristics of multi-factor and multi-level influences on rutting evaluation indexes.