1. Phenomenon: In the dry season, in the process of soil subgrade, the water evaporates quickly, and the soil layer is dry within the compaction depth of subgrade, and the compaction layer of subgrade cannot reach the optimal density without sprinkling water or only sprinkling water on the surface.

2. Cause analysis:

(1) Ignore the importance of compactness of soil subgrade or emphasize the difficulty of water source or lack of sprinkler equipment.

(2) Intentional (knowing) or unintentional (not understanding) illegal operation.

3. Harm: the required density can not be reached, which can not stand the test of vehicle load, shorten the life of pavement structure and cause early cracking and damage.

4. Governance methods:

(1) Educate the constructors to understand the importance of subgrade soil compactness to the stability of the structural layer.

(2) If the subgrade soil layer is dry, the method of sprinkling and mixing shall be implemented until the subgrade soil layer (0 ~ 30cm) reaches the optimal water content before rolling.