In recent years the research on Surface-initiated longitudinal cracking along wheelpath (or Top-Down cracking) is become a fresh hotspot in the field of pavement damage focused by international asphalt pavement engineering.Because the traditional load is the vertical surface load with uniform tire pressure, this loading is applied at only one position and no effort is made to distinguish between tire pattern.The traditional method can’t explain the mechanism of the top-down cracking. In order to discuss the mechanism of TDC, this paper establish a 3D finite element model of semi-rigid pavement structure and use the large finite element software Abaqus. The analysis shows that, in the crack beginning stage, the main tensile stress appears under the center of the load on the sub-base of the pavement,and its value increases with the time. When cracks appear in the base, the position of the main tensile stress appears at the bottom of the surface layer, under the outside edge of wheel path. The value of the main shear stress increases at the stage of the cracks beginning, but the increase is small. The value of the main shear stress decreases when the cracks appear in the middle of the surface layer, and the position of the main shear stress changes with the depth of the cracks. With the increase of the cracks’ depth, the adverse influence of the shear stress becomes weaker and weaker.So the key of controlling the cracks in the surface layer is prevention. To prevent the development of the cracks, the tensile strength of the layer’s material should be enhanced in any way. The stress and its value resulted from the vehicle loaded on the structure layer is bigger than the other cases when the position of the cracks is at the edge of wheel path, and the stress is much bigger than the shear strength and the fracture toughness of the material of the layer. As the shear strength of the material is not enough, the vertical cracks are easier to appear at the edge of wheel path under the load of the vertical. Once it appearing, the cracks will extended into the layer because of the load of vertical. Eccentric load generates greater stress in the structure than the load loaded upright. In fact, though, non-channeling can reduce the appearance of the tracks, eccentric load enhance the development of the cracks in the surface because of the existence of the cracks in the surface layer.
Study of Top-Down Cracking Behavior of Asphalt Pavement under Korean Army K-1 Tank Loads using Finite Element Analysis