Studies Of Asphalt Pavements Structure By The Methods Of Mathematics And Mechanics

In this paper,the performance of asphalt pavement under the condition of ambientternperature,high temperature and low temperature was analyzed by the methods ofmathematics and mechanics.According to the elastic layers system theory,the equivalent elastic modulus oflayed-foundation of asphalt pavements under ambient temperature was formulated andcalculated,and the parameters influencing it were analyzed.The comparision of equivalentelastic modula under flexible and rigid bearing plate and got by the specification showed thethree methods were difference each other very much,especially the method in thespecification existed a fatal error that it can lead the modulus to be a negative,which wasimpossible in fact.This paper discussed the idea and signification of long-life pavement and its design target.The structures of two kinds of long-life pavements were analyzed,and the most sensitiveparameters of its design target.Based on the analysis,four kinds of test road structure wereproposed for the Shan-Meng highway.Optimizing methods of pavements structure and roadcost were used to analyze the long-life pavements.The visco-elastic half space was solved according to the correspondence principle,andthe influencing parameters of surface displacement were analyzed;the results indicated thatthe surface displacement's most sensitve parameter was the inrecoverable viscocitycoefficient,and the two insensitive paramenters were the recoverable elasticity coefficientand recoverable viscocity coefficient.The two-layer visco-elastic system was solved by thenumerical inversion of Laplace transform,and the general solution of multilayeredvisco-elastic system was concluded.Taking the three-layer visco-elastic asphalt pavement asan example,three nonlinear visco-elastic models were introduced to consider the asphaltlayer's consolidation with the increasing of load times.A computing method of rut wasproposed to analyze the relation between the rut and load times,and the influence factorswere also studied.As for the anti-crack performance of asphalt concrete,several test methods werediscussed and the emphase was put on the SCB(Semi-Circular Bending)specimen.The stress intensity factors of the cracks in SCB specimen were calculated by the fracturemechanics theory and FEM(Finite Element Method);its fiting formula was got and itsinfluence factors were discussed.The SCB specimens from pavements and laboratory weretested at 0℃and-20℃,and their fracture toughnesses were got.As for the reflective crackand top-to-down crack in the asphalt pavements,FEM models were constructed for them,andtheir stress intensity factors at 5℃and 20℃were calculated and fitted.The results of fourthicknesses of asphalt layer were analyzed and compared,and the effects of asphalt layermodulus on crack's stress intensity factor were discussed.Using the Paris law,the relationbetween load times and crack length forⅠtype cracking was obtained,and the lifes ofreflective cracks and top-to-down cracks in asphalt layer with different thickness wereanalyzed.