Lesson 3/Learning Event 2
Subgrade Frost Groups
Soils are classified into four groups for frost design purposes. These classifications are described in
Table 13, Frost Design Soil Classification.
TABLE 13. FROST DESIGN SOIL CLASSIFICATION
Material with optimal frost protection characteristics will not always be available for each project.
Examine and test available materials and determine into which group they fall. Having determined the
subgrade frost group category of material available, use the frost group to enter into design calculations
of thickness required. Calculations for required thickness for the category of material will be covered
later in the lesson.