4.2.2. Shear Stress Analysis

According to the existing service conditions of the highway, the asphalt pavement is mainly damaged by shear stress. In asphalt pavement, it is easy to cause the shear failure of asphalt structural layers, especially under high temperatures. Shear failure is one of the most common problems with asphalt pavements.

Figure 12 shows the time–history variation diagram of the horizontal shear stress of each node in the pavement structure layer under the action of the coupled dynamic load. It can be seen from the figure that the horizontal shear stress of the road surface is the most obvious, while the horizontal shear stress of the base and subgrade surface is relatively small, indicating that the horizontal sheer force of the asphalt road structure mainly has an effect on the asphalt road surface, which reminds us to pay special attention to the shear condition of the road surface in the design and construction process. At the same time, it can be seen that the horizontal shear stress can be positive or negative within the range of influence, and its value is approximately symmetric.

**Figure 12.** Time–history diagram of shear stress. (Note: ×10\*\*1 means ×<sup>10</sup>1, .5 means 0.5).

Figure 13 shows the variation in the shear stress of nodes in the pavement structure layer at the midpoint of the road, along with the depth of the road section. According to the data in the figure, the proportion of cushion and roadbed with horizontal shear stress below 1 m is almost zero. The shear stress of asphalt pavement mainly occurs in the road surface and the base layer, the maximum shear stress is in the middle of the surface layer, and the value of shear stress is 43,858 Pa.

**Figure 13.** Diagram of shear stress variation with road depth.
