Continuously Reinforced Concrete Rigid-Flexible Composite Pavement Research On Top-Down Cracking Of Asphalt Surface

In the initial stage of operation of the continuous reinforced concrete rigid-flexible composite pavement,under the repeated action of temperature shrinkage stress and traffic load,cracks are prone to appear on the asphalt surface layer.The thinner asphalt surface layer makes it easier for the cracks to penetrate the entire asphalt surface layer.Rainwater enters the interior of the pavement structure layer,causing diseases such as reduced durability of continuously reinforced concrete slabs,increased width of transverse cracks,corrosion of steel bars and voids at the bottom of the slab.Therefore,the research on the Top-Down cracking of the asphalt surface of the continuous reinforced concrete rigid-flexible composite pavement has theoretical significance and application value.In order to explore the cracking mechanism of the Top-Down cracks in the asphalt surface,the finite element method was used to analyze the influence of the temperature field and temperature stress of the asphalt surface on the top-down cracks,and combined with the physical engineering observation results,the early Top-Down cracks are mostly temperature-type transverse cracks,generally only at the position 1～3cm on the surface of the asphalt layer.At the same time,considering the contact performance of the tire and the road surface and the horizontal force,the three-dimensional finite element model of the rigid-flexible composite road surface under the action of the non-uniform three-dimensional stress is established,and the tensile and shear stress distribution rules at the different tire contact points are analyzed,and the vehicle The stress distribution law of the road surface under the turning situation is analyzed.It is found that the excessive longitudinal tensile stress and shear stress near the wheel track are the main reasons for the top-down cracking of the asphalt surface.Excessive vehicle load will aggravate the original The propagation speed of cracks is also an important cause of "watermark cracks";under non-uniform load,when the thickness of the asphalt surface layer is less than 6cm,the shear resistance of the interlayer material should be improved,and when the thickness of the asphalt layer is greater than 6cm,Should focus on the shear and tensile capabilities of road surface materials.Based on the extended finite element method and the improved Paris formula,the fatigue growth model of Top-Down cracks under the action of temperature shrinkage stress and traffic load is established,and the fatigue growth of Top-Down cracks under the action of temperature shrinkage stress and traffic load is analyzed.Under the action of shrinkage stress-traffic load,the Top-Down crack will develop a composite oblique crack growth.Under normal circumstances,the propagation path is the same side obliquely downward under the action of wheel load.The traffic load mainly changes the fatigue growth of Top-Down cracks from an open type.It is a composite type,and the temperature shrinkage stress mainly affects the fatigue life of Top-Down cracks.The research results can provide a theoretical basis for the structure and material design based on the Top-Down cracking control of the continuous reinforced concrete rigid-flexible composite pavement asphalt surface.