FrostLine

Frost Heave Susceptibility

USACE F1–F4 Preliminary estimate

Classify a soil's frost-heave susceptibility from its type and gradation, using the USACE F1–F4 groups and the Casagrande screening criterion.

From a hydrometer / gradation test
Used for clays

Results update as you type. These are educational estimates — confirm against the governing code and a licensed engineer before design use.

Method & references

Soils are classified into the USACE frost-design groups F1–F4 (plus NFS, non- frost-susceptible) based on soil type and the percentage of material finer than 0.02 mm:

  • F1 — gravels, 3–10% finer than 0.02 mm (low)
  • F2 — sands and gravels with more fines (medium)
  • F3 — silty/clayey coarse soils, clays PI > 12 (high)
  • F4 — silts, lean/varved clays (very high)

The Casagrande screen is applied first: a fairly uniform coarse soil with less than 3% finer than 0.02 mm is generally non-frost-susceptible. Frost heave also requires a frost- susceptible soil, freezing temperatures, and a water supply — remove any one and heave is controlled.

Reference: U.S. Army Corps of Engineers frost-susceptibility classification; Casagrande (1931).