Mechanical Responses And Damage Analysis Of Asphalt Pavement Structure With Graded Gravel Base

In order to meet the requirements of highway construction,structural types such as asphalt pavement with graded gravel base have been paid more and more attention.The materials of pavement construction used for flexible base asphalt pavement,such as granular materials and fine-grained soil,show strong nonlinear behavior,and their resilience modulus is deeply affected by the stress state.It is necessary to consider their real material characteristics in the analysis and design of pavement structure.On the other hand,with the ever-expanding of Chinese highway transportation and logistics industry,the damage effect of biaxial,triaxial and other multiaxial loads on pavement structure cannot be ignored and become more and more complex.On the basis of considering the material nonlinearity,this paper comprehensively used the layered system theory and finite element method to deeply discuss the influence of the material nonlinearity of graded gravel base on the mechanical response of pavement structure,and carried out the damage analysis of pavement structure based on the action of multiaxial load.The main contents of this paper are as follows:(1)The principle of nonlinear analysis carried out by KENLAYER program based on layered system theory were briefly introduced.Then,considering the nonlinearity of graded gravel materials,the layered system model of graded gravel base asphalt pavement structure under BZZ-100 standard axle load was established by using KENLAYER program.The mechanical responses of pavement structure,such as road surface deflection,strain along the driving direction,vertical stress and vertical strain on the top of roadbed,are obtained.The differences of mechanical responses between linear elastic and nonlinear granular materials was compared laterally.(2)Two typical axisymmetric nonlinear finite element programs,MICH-PAVE and ILLI-PAVE,used for asphalt pavement structure analysis,were selected to make comparisons between the application levels in pre-processing,calculation and post-processing.By taking the asphalt pavement structure with graded gravel base as an example,considering the nonlinearity of graded gravel and fine-grained soil materials,the differences of their critical mechanical responses were analyzed.Moreover,this paper expounded how to obtain the equivalent resilient modulus of nonlinear pavement structure by using MICH-PAVE program,which lied a foundation for the subsequent analysis and comparison of linear and nonlinear damage of asphalt pavement with graded gravel flexible base.(3)The basic theory of damage analysis by using KENLAYER program were briefly introduced,and established the damage analysis model of asphalt pavement with graded gravel base based on layered system under uniaxial,biaxial and triaxial loads.Furthermore,considering the linear and nonlinear conditions of graded gravel and fine-grained soil respectively,when the thickness of the asphalt surface layer changed,the change rules of the damage rate corresponding to the fatigue cracking and the permanent deformation.The damage rate rules between biaxial,triaxial and uniaxial and the interference effects between biaxial and triaxial were analyzed.Additionally,the damage control mode of pavement structure is clarified,which can provide reference for the structural analysis and design of asphalt pavement with graded gravel base under multiaxial loads.