Mechanical Responses And Damage Analysis On Asphalt Pavement In Plateau-Cold Region Under Wheel Load

The plateau-cold region is widely distributed in China with climatic characteristics of high altitude,low temperature,large temperature difference,abundant sunshine and strong radiation.Meanwhile,the asphalt pavement has been seriously damaged in plateau-cold region.Hence it's very important for the reasonable selection of asphalt pavement structure.The mechanical response analysis of asphalt pavement structure in plateau-cold region is not comprehensive,either not considered nonlinearity of granular and cohesive materials,or not fully combined with environment and climate characteristics to carry out damage analysis of fatigue cracking and permanent deformation under wheel load.Based on a comprehensive survey about the research status at home and abroad,the main work carried out as follows:(1)The fundamentals of axisymmetric nonlinear finite element software MichPave(the mechanistic analysis module of MFPDS)were introduced,including material models,gravity and lateral stresses,lateral and bottom boundaries,mesh generation,stress modification and convergence criterion,equivalent resilient moduli of nonlinear layer,fatigue life and rut depth predictions,which laid foundation for the subsequent mechanical response analysis of asphalt pavement in plateau-cold region.(2)The fundamentals of elastic layered system software KENLAYER(the flexible pavement analysis module of KENPAVE)were introduced,including superposition of wheel loads,viscoelastic analysis,nonlinear analysis and damage analysis,which laid foundation for the subsequent damage analysis of asphalt pavement in plateau-cold region.(3)Based on four kinds of asphalt pavement structures including semi-rigid,sandwich,full depth and flip-over type,considered nonlinearity of graded crushed stone in flip-over type structure and roadbed in four structures,the axisymmetric nonlinear finite element models were established under wheel load by MFPDS software.Displacements,stresses and strains of four structures were analyzed under wheel load,and their road performance was compared.(4)Considered the viscoelasticity of asphalt surface layer,the nonlinearity of graded crushed stone and roadbed,the mobility of wheel load,based on the theory of elastic layered system,models of four kinds of asphalt pavement structures were established including semi-rigid,sandwich,full depth and flip-over type under wheel load by KENPAVE software.Damage analysis of a load group was carried out in the spring,summer,autumn and winter during a year respectively from fatigue cracking and permanent deformation.The influence of pavement temperature and soil thawing in spring on the damage rule was discussed,the damage mode and degree were defined,the damage rule of four kinds of structures was compared.(5)Combined with results of mechanical response and damage analysis,some suggestions were put forward on the structural design of asphalt pavement in plateau-cold region.