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
(a)
Gravels
0-1.5
GW, GP
Crushed Stone
Crushed Rock
(b) Sands
0-3
SW, SP
PFS2
(a)
Gravel
1.5-3
GW-GP
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
F3
(a) Gravely Soils
Over 20
GM, GC
(b) Sands, except very
Over 15
SM, SC
fine silty sands
(c) Clays, PI>12
--
CL, CH
F4
(a) Silts
ML, MH
--
(b) Very fine silty
Over 15
SM
sands
CL, CL-ML
--
(c) Clays, PI<12
CL, ML, CL-ML,
--
(d) Varved clays and
CL, ML, and SM,
other fine grained,
CL, CH, and ML,
banded sediments
CL, CH, ML, and SM
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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