UFC 3-260-02
30 June 2001
(e) Compare these reduced subgrade strength pavement thicknesses with those
required for the Limited Subgrade Frost Penetration Design procedure.
(2) Limited subgrade frost penetration design.
(a) From Figure 12-7, the minimum thickness of PCC concrete layer required in
nonfrost areas are:
Traffic Area
PCC Thickness, mm (in.)
A
406 (16.0)
B
394 (15.5)
C
305 (12.0)
D
241 (9.5)
The average moisture content and density of the combined base is assumed to be 3 percent and
2,403 kg/m3 (150 lb/ft3), respectively. The frost penetration a is obtained from Figure 20-5 or
from Equation 20-9. For pavement thickness exceeding 305 millimeters (12 inches), deduct
133-degree Celsius hours (10-degree Fahrenheit days) from the design freezing index for each inch
in excess of 305 millimeters (12 inches).
Design
Freezing Index
Frost Penetration,
PCC Thickness
a, mm (in.)1
EC-hr (EF-days)
Traffic Area
mm (inches)
A
406 (16.0)
8,800 (660)
1,067 (42)
B
394 (15.5)
8,865 (665)
1,067 (42)
C
305 (12.0)
9,331 (700)
1,118 (44)
D
241 (9.5)
9,331 (700)
1,118 (44)
1
Obtained from Equation 20-9.
(b) The required combined base thickness c for complete frost penetration into the
subgrade from Equation 20-12 is:
'
Frost Penetration,
PCC Thickness,
Combined Base Thickness
Traffic Area
a, mm (in.)
p, mm (in.)
c, mm (in.)
A
1,067 (42)
406 (16.0)
661 (26.0)
B
1,067 (42)
394 (15.5)
673 (26.5)
C
1,118 (44)
305 (12.0)
813 (32.0)
D
1,118 (44)
241 (9.5)
877 (34.5)
20-19
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