Study On Influencing Factors And Stress Of Asphalt Concrete

In the past for a long period of time,semi-rigid base asphalt concrete was widely used at home and abroad,but it was easy to produce reflective cracks,which resulted to rutting,subsidence,fatigue cracking and other damage,in the early use of the concrete.Therefore,our country put forward the composite base construct,the new base course with semi-rigid base course as its subbase and asphalt macadam or graded macadam upbase.Through the inspection of a large number of literature shows that,for the prevention of reflection cracks,graded macadam composite base asphalt concrete effect is less than the effect of asphalt macadam,at the same time,the modulus of the asphalt mixture directly affects the stress of the concrete.Therefore,this paper takes the asphalt macadam composite base asphalt concrete as the research object,with ABAQUS finite element software,to analyze the influence of each layer modulus on concrete stress,which can provide some guidance for its further use.Through the comparison of the concrete mechanics model,determine the time hardening creep model to simulate the creep characteristics of asphalt mixture,and the wheel load is simplified to the rectangular uniform load,create the concrete model for stress analysis,it is concluded that:when the each layer modulus increases,the vertical pressure stress and Mises yield stress decreases,and the longitudinal shear stress become larger;when the above layer modulus increases,the transverse shear stress become larger,but when the middle layer and the following layer modulus increase,its value becomes smaller.Meanwhile,the above layer modulus has the greatest influence on the maximum transverse shear stress,the maximum longitudinal shear stress and the maximum Mises yield tensile stress,and the middle layer modulus has the greatest influence on the maximum vertical pressure stress,it is possible to select lower grades of asphalt,such as 30#asphalt,50#asphalt,or by adding an appropriate amount of high modulus admixture to the asphalt mixture to increase the middle layer modulus,thereby reducing the vertical pressure stress,and preventing the diseases of rutting and subsidence.In addition,in order to reduce the tensile stress and prevent fatigue cracking,the above layer should try to use the skeleton dense type gradation or increase the content of cementing material,or at higher temperatures for construction.Finally,when testing the maximum vertical pressure stress,the maximum longitudinal shear stress and the maximum Mises yield tensile stress of the asphalt macadam composite base asphalt concrete,just on either side in the center of the wheel testing samples,and testing the maximum transverse shear stress,just on either side in the inside wheel sampling.The research contents of this paper provide a theoretical basis for the design,construction and testing of graded macadam composite base asphalt concrete,but also increase the service life,reduce the rutting,sink and other damage,and enhance its service performance and operational safety,reduce maintenance and operating costs provide a very good guiding significance.