1. Earthwork excavation: Before the subgrade construction starts, it is necessary to carry out earthwork excavation according to the design requirements, that is, to remove the soil layer below the subgrade foundation. The excavation shall be carried out according to the shape, slope and elevation of subgrade cross section, and at the same time, attention shall be paid to protecting the stability of subgrade and the safety of surrounding environment.
2. Leveling of road foundation pit: The excavated road foundation pit needs to be leveled, including reinforcing the bottom of subgrade to ensure that the bottom of subgrade is smooth and firm and meets the design requirements.
3. Subgrade filling: The leveled subgrade needs to be filled, that is, earthwork is filled to form a predetermined subgrade cross section. When filling, layered filling, compaction and inspection shall be carried out according to the design requirements to ensure that the filled subgrade meets the design requirements.
4. Subgrade slope treatment: the soil on the side of subgrade needs to be treated by slope to prevent the slope from collapsing. Slope treatment depends on different geological conditions and design requirements, and can be reinforced by digging holes, adding piles and retaining walls.
5. Drainage system construction: A drainage system is set in the subgrade to ensure smooth road drainage. The drainage system includes rainwater pipes, ditches and seepage pipes.
6. Grass curtain construction of subgrade: Grass curtain construction is needed on subgrade surface to protect subgrade surface from erosion and weathering. The material of the grass curtain can be lawn grass.
7. Acceptance of subgrade: After subgrade construction is completed, it needs to be accepted to ensure that the construction quality meets the design requirements and engineering standards, and at the same time, it also provides guarantee for subsequent road construction.