TM 5-822-12
Table 5. Frost design soil classification.
Percentage
Finer Than
Typical Soil Types
Frost
0.02 mm
Under Unified Soil
Group
Kind of Soil
by Weight
Classification System
NFS*
(a) Gravels
0-1.5
GW, GP
Crushed stone
Crushed rock
(b) Sands
0-3
SW, SP
PFS**
(a) Gravels
1.5-3
GW, GP
Crushed stone
Crushed rock
(b) Sands
3-10
SW, SP
S1
Gravelly soils
3-6
GW, GP, GW-GM, GP-GM
S2
Sandy soils
3-6
SW, SP, SW-SM, SP-SM
F1
Gravelly soils
6 to 10
GM, GW-GM, GP-GM
F2
(a) Gravelly soils
10 to 20
GM, GW-GM, GP-GM
(b) Sands
6 to 15
SM, SW-SM, SP-SM
F3
(a) Gravelly soils
Over 20
GM, GC
(b) Sands, except
Over 15
SM, SC
very fine
silty sands
(c) Clays, PI > 12
--
CL, CH
F4
(a) All silts
--
ML, MH
(b) Very fine silty
Over 15
SM
sands
(c) Clays, PI < 12
--
CL, CL-ML
(d) Varved clays
--
CL and ML
and other fine-
CL, ML, and SM
grained banded
CL, CH, and ML
sediments
CL, CH, ML and SM
*Nonfrost-susceptible.
**Possibly frost-susceptible, but requires laboratory test to
determine frost design soil classification.
possible points while taking advantage of the natural
Table 6. Frost-area soil support indexes of subgrade
surface geometry to the greatest extent possible.
soils.
Frost Group
Frost Area Soil
of Subgrade Soils
Support Index
b. Adequate drainage must be provided outside
F1 and S1
9.0
the road or airfield area to accommodate maximum
F2andS2
6.5
possible drainage flow from the road or airfield. Ditches
F3 and F4
3.5
and culverts will be provided for this purpose. Culverts
should be used sparingly and only in areas where
adequate cover of granular fill is provided over the
culvert. Additionally, adjacent areas and their drainage
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