Research On The Shear Fatigue Performance Of Asphalt Mixture

With the increase of traffic volume and traffic channelling, pavement diseases such as rutting, jostle, crack are more and more serious which mostly caused by the lack of shear strength and shear fatigue resistance of asphalt pavement. By now road researchers have generally identified the shear failure and shear fatigue damage are important origin of asphalt pavement rutting disease, but a systematic in-depth research is still inexistent. During the using of asphalt pavement, rutting disease is not caused by vehicle load once time but a rapid process until shear fatigue failure, so it’s necessary to research the shear fatigue performance of asphalt mixture and asphalt pavement.At first, based on the viscoelastic theory and fatigue damage theory which are directions of asphalt mixture shear fatigue test, the shear fatigue of asphalt mixture is researched by repeated uniaxial penetration test, a method to determine the shear fatigue life from shear deformation-load times curve is designed.Secondly, designing several series tests and researching the effect of factors such as load levels, heavy traffic, asphalt and VV(percent air voids in bituminous mixture) to shear fatigue life of asphalt mixture, results indicate that the load is bigger the fatigue life is shorter, the load and shear fatigue life conform to double logarithm linear relationship, with the heavy traffic or overload the fatigue life reduce rapidly, using the modified asphalt(stabilized rubber modified asphalt) can increase the shear fatigue life twofold compared with base asphalt mixture, with the increase of VV, shear fatigue life of asphalt mixture increases at first and then decreases, existing an optimum VV. Considering these factors, a predicted formula is fitted by test date.Thirdly, based on viscoelastic theory and fatigue damage theory, assuming the asphalt pavement as Semi-infinite half space and continuity conditions at the layer interfaces, a three-dimensional finite element model is established by ABAQUS software to analysis the variation of asphalt pavement shear stress and shear deformation under half-sine wave load. Results indicate that with the increase of depth the shear stress of asphalt pavement increases at first and then decreases, the maximum shear stress is at about5cm, the shear deformation decreases with the increase of depth, and the compaction stage as weli as the stable deformation stage is obvious in the time-shear deformation graph.Fourthly, three-dimensional finite element models of semi-rigid base asphalt pavement and flexible base asphalt pavement and complex base asphalt pavement are established to compare their shear fatigue performance. Results indicate that the shear fatigue performance of semi-rigid base asphalt pavement is better, and the shear stress of semi-rigid base asphalt pavement is centralized and the shear deformation is bigger.Finally, in accordance with research and analysis of asphalt mixture and asphalt pavement an asphalt pavement structure design method considering shear fatigue is conceived.