Study On Effective Thermal Conductivity Of Asphalt Concrete Based On Modeling Method Of Physics Engine

Asphalt pavement has been developed rapidly in recent years, in the meanwhileearly diseases of various degrees come up. Rutting at high temperature and lowtemperature shrinkage crack are the most prominent in these diseases. At present, themain idea to deal with the problem is to improve the performance of pavement material,which greatly increased the difficulty of engineering and construction cost. As suchdiseases have a direct relationship with the serious temperature conditions of thepavement structure, we can start from the study on factors affecting pavementtemperature field, and search for technical means of actively controlling, adjusting thetemperature field.Based on the above ideas, a finite element model was established and validatedaccording to theory of transient heat transfer. The influence law of thermo-physicalproperties of the upper layer pavement material such as thermal conductivity, specificheat, absorption and emissivity to temperature condition of each pavement structurelayer was studied based on above model. After the importance of thermal conductivityhas been validated, reasonable distribution of thermal conductivity of three pavementlayers was studied to alleviate low temperature shrinkage cracking and high temperaturerutting. It was found that the increase of conductivity at up and middle layers cansignificantly improve low temperature situation at the surface layer, reducing thermalconductivity of up layer can improve the high temperature condition, especially there isa change sensitive point, approximately at around4500J/m·h·℃.To study methods of improving thermal conductivity of asphalt concrete,mesomechanics was applied to get the influencing factors. During Mesoscopicnumerical model building, taking into account defects existing in current modelingalgorithm, the concept of physics engine was introduced. Based on comparison of avariety of open source physics engine, the fundamental theories of physics engine wereclarified, as well as simulation process. To meet the requirement of modeling, Bulletwas selected as a calculation core. After its system framework analysed, it was compiledto a package using SWIG, making it easy to use Python for system integration. Databaseof aggregate vertex coordinates was built based on Monte Carlo method, further more,aggregates of specified graded was placed visibility using the physics engine. Aexample of three dimensional stochastic model building showed that this method ofbuilding mesoscopic numerical model is efficient and applicable.Finally, for the establishment of two-dimensional mesoscopic models, Walravenformula was validated to convert3D grading curve, besides, discrete formula and itscalculation program were got which is applicable for common grading curve. Effective thermal conductivity of asphalt mortar was calculated using a theoretical method as theparameter of finite element model. Based on the above, according to the two-stageresearch idea, a two-dimensional numerical model was established for numericalexperiments, then influence law of grading, aggregates, asphalt, fillers and other factorson the thermal conductivity of asphalt concrete were studied, as well as their mechanism.The result proved that, Thermal properties of asphalt had the most significant impact oneffective thermal conductivity of asphalt, followed by aggregate properties, while coarseaggregate content can be neglected. Results of the research have an importantsignificance for developing temperature-control asphalt concrete.