UFC 3-260-02
30 June 2001
Table 20-1
Frost Design Classification
Percentage Finer
than 0.02 mm by
Typical Soil Types Under Unified Soil
Frost Group
Kind of Soil
Weight
Classification System
NFS1
0-1.5
GW, GP
(a)
Gravels
Crushed Stone
Crushed Rock
(b) Sands
0-3
SW, SP
PFS2
1.5-3
GW-GP
(a)
Gravel
Crushed Stone
Crushed Rock
(b) Sands
3-10
SW-SP
S1
Gravely Soils
3-6
GW, GP, GW-GM, GP-GM
S2
Sandy Soils
3-6
SW, SP, SW-SM, SP-SM
F1
Gravely Soils
6-10
GM, GW-GM, GP-GM
F2
(a) Gravely Soils
10-20
GM, GW-GM, GP-GM
(b) Sands
6-15
SM, SW-SM, SP-SM
GM, GC
Over 20
F3
(a) Gravely Soils
SM, SC
Over 15
(b) Sands, except very
fine silty sands
CL, CH
--
(c) Clays, PI>12
ML, MH
--
F4
(a) Silts
SM
Over 15
(b) Very fine silty
CL, CL-ML
--
sands
CL, ML, CL-ML,
--
(c) Clays, PI<12
CL, ML, and SM,
(d) Varved clays and
CL, CH, and ML,
other fine grained,
CL, CH, ML, and SM
banded sediments
1
Nonfrost susceptible.
2
Possibly frost susceptible, requires laboratory test to determine frost design soil classification.
supporting capacity, including severe weakening during frost melting periods. The three methods
are (a) complete frost penetration method, (b) reduced subgrade strength method, and (c) limited
subgrade frost penetration method.
a. Complete Frost Penetration Method. In the complete frost penetration method, frost is not
allowed to penetrate into frost susceptible subgrade soils. This method completely prevents
affects of frost action, i.e., frost heave and thaw weakening in the subgrade, subbase, or base
course. The total pavement thickness from this method is seldom used in the final design since
prevention of frost penetration into the subgrade is nearly always uneconomical and unnecessary.
20-2
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