"Thin layer patching" refers to patching a layer of mixture with a thickness of less than 5cm in low-lying areas during the shaping process of the base layer. If the surface of the lower part is smooth and hardened, the patch layer and the base layer will not be firmly bonded. During the rolling process, under the action of the roller, the "thin layer patch" is easy to fall off, crushed, and pushed, seriously affecting the appearance quality of the subbase.