UFC 3-260-02
30 June 2001
Water Content Ratio (r)
f
g
0.6
0.881
0.216
0.8
0.850
0.209
1.0
0.806
0.200
1.2
0.781
0.197
1.4
0.756
0.188
1.6
0.725
0.181
1.8
0.706
0.178
2.0
0.644
0.175
2.5
0.613
0.156
3.0
0.550
0.144
g. Step Six. When the maximum combined thickness of pavement layers required by this
design procedure exceeds 1.5 meters (60 inches), a total combined thickness to 1.5 meters
(60 inches) will be used. Limiting the combined thickness of pavement and base to 1.5 meters
(60 inches) may result in a greater surface roughness because of the greater subgrade frost
penetration. To minimize pavement damage and roughness, steel reinforcements can be used in
the concrete slabs to prevent large cracks. Smaller unreinforced slabs can also be considered.
Alternatively, the design could incorporate subbase layers of uniform fine sand with a high moisture
content to reduce frost penetration into the subgrade. These materials would be allowed only in
the lower 500 millimeters (20 inches) of the subbase. When using this alternative the designer
must be certain that materials of Frost Groups S2 or better are used as subbase layers. If either
the high moisture retention subbase course or a combined thickness over 1.5 meters (60 inches) is
selected for frost design purposes, specific approval of HQUSACE (CEMP-ET), the appropriate Air
Force Major Command, or Naval Facilities Engineering Command shall be obtained.
h. Step Seven. The combined thickness of pavement layers required for limited subgrade frost
penetration is then compared with that obtained for nonfrost conditions, and the thicker of the two
cross sections will be adopted as the design thickness.
7. GRANULAR BASE- AND SUBBASE-COURSE REQUIREMENTS. The base-course material used
in pavements in seasonal frost areas will meet the requirements for base course outlined in
Chapter 8. In addition, the following requirements must be met:
(1) The top 50 percent of the combined base thickness must be nonfrost susceptible.
(2) The lower 50 percent thickness of combined base may be either nonfrost susceptible
material, partially frost susceptible material, S1 or S2 material. If the separation layer meets the
minimum S1 or S2 frost susceptibility criterion, then it can be considered to be part of the
combined base. If not, then an additional 100-millimeter (4-inch) separation layer is required.
20-10
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