Fatigue Damage Regularity And Microscopic Analysis Of Asphalt Mixture Under Water Immersion

When free water was present in the asphalt pavement structure,each cycle was loaded on the saturated asphalt pavement structure once,and the structural damage caused by pore water pressure which the internal aggregate skeleton generated was more than several times or even more times greater than that in the relatively anhydrous condition.In order to study the fatigue damage mechanism and its meso-change law of asphalt mixture under the action of immersion,the relationship between the meso-change law and the macroscopic performance of the asphalt mixture under the action of immersion was studied,through the combination of theoretical basis,experimental method and numerical simulation analysis.Finally the changes of pore water pressure inside the asphalt pavement structure and the meso-deformation and evolution of the internal structure of the asphalt mixture under water immersion were obtained.The main results of this paper are as follows:(1)By investigating the relevant references at home and abroad,it is generallybelieved that the water damage of the asphalt mixture was related to the porosity.SMA-13 mixture specimen with different porosity was obtained by rotating indoor compaction test.Then,the porosity and permeability coefficient of the specimens with different porosity,the relationship between the degree of damage and porosity and permeability of different compaction specimens of SMA-13 mixture were obtained under different fatigue damage.The results show that the fatigue damage degree of asphalt mixture was related to its permeability,it was of great significance to take preventive maintenance measures to prevent and control water damage effectively.(2)Based on the fluid-structure interaction theory of porous medium and the elastic layered system theory of asphalt pavement structure,the distribution regularity of dynamic pore water pressure,stress,strain and displacement of saturated asphalt pavement structure under standard load and overload were simulated by using the method of laboratory experiments and finiteelement numerical simulation software ABAQUS.In the end,the relation between the damage degree of the upper layer and the dynamic pore water pressure is obtained by analyzing the fatigue damage law under the action of water immersion.(3)Usually,the internal microstructure of the asphalt pavement structure was considered to be isotropic and its complex meso-structure was rarely studied deeply,the internal mesoscopic structure of the SMA-13 mixture with different porosity was obtained by CT non-destructive scanning technique,the distribution characteristics of the internal void sand the change of the damage density of the specimens with different porosity of SMA-13 mixture were obtained,to a certain extent,the influence of meso structure change of asphalt mixture on the whole was revealed.(4)By using the self compiled program,the digital image files into other image software to exchange data with AutoCAD file format,the SAT interface in CAD using digital image processed will set the vector edge information,and the two-dimensional mesoscopic structure using ABAQUS finite element software to get SMA-13 mixture of meso numerical model.Finally,the parameters obtained from laboratory tests were applied to a two-dimensional numerical model to illustrate the change of meso mechanical properties of asphalt mixtures under soaking conditions.