Subgrade, also known as soil foundation, refers to the road groove formed by filling or excavation on subgrade according to the thickness and elevation requirements of pavement structure layer. Pavement subgrade The function is to bear the load from the road surface, and the subgrade part within 80cm below the bottom of the road surface is the road bed.

1. Subgrade is the foundation of pavement and bears the load from pavement. Within 500mm below the top surface of the road bed, the soil that meets the requirements of the road bed shall be filled and compacted in layers to achieve uniformity and compactness.

In order to reduce the project cost, the local materials should be selected for the subgrade filler in combination with the material situation at the project site.

2. According to the Technical Specification for Highway Subgrade Construction, the maximum particle size of the subgrade filler of the first-class highway should be less than 100mm, and the minimum CBR (California Bearing Ratio) of the filler should be 8%.

3. The reinforcement of individual subgrade should be carried out according to the actual situation of subgrade, soil quality, precipitation, groundwater type and buried depth, and the source of reinforcement materials. After comparison, reinforcement measures such as in-situ rolling, changing or improving soil, strengthening underground drainage and setting geosynthetics can be adopted.