Subgrade is the foundation of pavement, which refers to the part of subgrade within 80cm below the bottom of pavement. Subgrade is divided into upper and lower layers: the subgrade with a depth of 0 ~ 30cm below the bottom of the pavement is called subgrade; Subgrade within the depth of 30 ~ 80 cm below the bottom of pavement is called subgrade bed.
The subgrade will bear the large load stress transmitted by the pavement, and it is required to be uniform and dense to achieve the specified strength.
Subgrade structure
If it is an earthwork subgrade, the subgrade refers to the part from -80 cm to 0 cm. If the strength of earthwork subgrade cannot be guaranteed, it needs to be filled with soil or treated with 8% lime powder or cement powder. There is usually one item in the list, that is, 0-30cm lime treatment, which actually refers to the treatment of -30cm~0cm soil layer.