UFC 3-260-02
30 June 2001
The reduced subgrade strength method produced the more economical design for all traffic areas.
A comparison must be made with the nonfrost pavement thickness. With F4 subgrade soils, in lieu
of drainage layer under the PCC pavement, a drainage layer between the subbase and the
separation layer should be considered. The divisions shown are one of many possibilities.
Judgment must be used when layer thicknesses are selected.
Total "Combined
S1 or S2
Drainage
Separator
Base" Thickness
NFS Base Layer
Subbase Layer
Layer
Layer
Traffic Area
mm (in.)
mm (in.)
mm (in.)
mm (in.)
mm (in.)
A
1,168 (46.0)
610 (24.0)
356 (14)
102 (4)
102 (4)
B
1,156 (45.5)
622 (24.5)
330 (13)
102 (4)
102 (4)
C
965 (38.0)
508 (20.0)
250 (10)
102 (4)
102 (4)
D
775 (30.5)
419 (16.5)
152 (6)
102 (4)
102 (4)
(3) Subgrade preparation. The depth of subgrade preparation D will be the lesser of the
following:
(a) D = 610 millimeters (24.0 inches).
(b) D = [2/3 @ (maximum frost penetration)] - (Combined thickness of PCC, base,
subbase and drainage layers).
Frost Penetration
Combined Pavement
Subgrade Preparation
Traffic Area
mm (in.)
Thickness, mm (in.)
Depth, mm (in.)
A
2,235 (88)
1,168 (46.0)
330 (13.0)
B
2,235 (88)
1,156 (45.5)
330 (13.0)
C1
2,285 (90)
965 (38.0)
178 (7.0)
D1
2,311 (91)
775 (30.5)
381 (15.0)
1
Use one-half rather than two-thirds frost penetration for traffic areas C and D.
(c) D = 1,829 millimeters (72 inches) - (Combined Pavement Thickness).
Traffic Area
Combined Pavement Thickness, mm (in.)
D, mm (in.)
A
1,168 (46.0)
660 (26.0)
B
1,156 (45.5)
673 (26.5)
C
965 (38.0)
864 (34.0)
D and Overruns
775 (30.5)
1,054 (41.5)
20-25
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