Research On Strength Parameters Of Asphalt Mixture Based On Boundary Effect Theory

Asphalt pavement is widely used in highway construction due to its many advantages.However,due to the duplicated traffic load and the deteriorated environment,cracks are developed in the early stage of service.Asphalt pavement cracking is the dominant disease form of asphalt pavement,and it has a significant impact on the pavement safety.Asphalt mixture is the main component of asphalt pavement,so it is important topic to study the fracture characteristics of asphalt mixture.In order to be able to predict the strength parameters of the asphalt mixture and optimize the gradation of the materials,considering the aggregate size and pre-crack offset position of the asphalt mixture;the existing boundary effect model is modified in this thesis.The model is validated by the comparison among the experiment,numerical simulation and other literature.The main work and conclusion are as follows:(1)Using AC-13 graded asphalt mixture,the fracture tests of asphalt mixture three point bending(3pb)beam under three different pre-crack positions are carried out,and the load-displacement curve is obtained.The results showed the distance between the centers increases,the peak load also increases,and the cracks tend to expand toward the center.Meanwhile the tensile strength is determined by the uniaxial tensile test.(2)With the help of the extended finite element method of ABAQUS software,the cracking process of the three bending beam was simulated,and the load displacement curve is obtained.the effectiveness of the extended finite element simulation is verified by the test result.Then the stress intensity factors of the crack tip in the 3pb beam are calculated by the method of contour integration.The result shows that with the increase of the offset distance,the influence of the type II cracks in the fracture process increases,however,type I crack is still dominant crack.(3)A boundary effect model with aggregate particle size is studied and the model is sufficiently accurate when the discrete parameter is 0.6-1.2.The concept of the normal distribution of the model is introduced,and the 95% confidence interval of the material parameters can be determined by the peak load.Finally,the boundary effect model is modified to predict the tensile strength and fracture toughness of the pre-crack specimens with different offset distances.The result show that the proposed model is reliable and reasonable through experiments,numerical simulations and other literature comparisons.The model also can be inversed to obtain the peak load of 3pb beam which sizes are given.The modified model supplies a creative idea for the mechanical characterization of asphalt mixture.