UFC 3-260-02

30 June 2001

(3) The design CBR of the subbase material has been determined to be 30. Enter

Figure 10-19 at a CBR equal to 30 and find that the required thickness of base and surface is

405 millimeters (16 inches) for the design aircraft. From Table 8-5, the required minimum thickness of

the surface course is 127 millimeters (5 inches) and of the 100 CBR base, 228 millimeters (9 inches).

Use a 127-millimeter (5-inch) asphalt concrete (AC) surface and 280 millimeters (11 inches) of 100 CBR

base to provide the 405 millimeters (16 inches) required above the 30 CBR subbase.

(4) The required thickness of subbase is 330 millimeters (13 inches), 735 minus

405 millimeters (29 less 16 inches).

(5) From Table 6-2, it is determined that for cohesive subgrade soils, 95 percent compaction

is required for 864 millimeters (34 inches) below pavement surface and 90 percent compaction for a

1,320-millimeter (52-inch) depth.

(6)

The design section for type B traffic area is illustrated below:

127-mm (5-in.) AC surface

280-mm (11-in.) 100 CBR Base1

330-mm (13-in.) 30 CBR Subbase1

Top of Subgrade

203-mm (8-in.) 95 percent compaction

457-mm (18-in.) 90 percent compaction

1

Base and subbase compacted to 100 percent.

(7)

Design for drainage layers is illustrated in TM 5-820-2/AFJMAN 32-1016.

b. Example 2.

(1) Design an Army Class III airfield apron (type B traffic area) for a single-wheel tricycle gear

aircraft with a gross weight of 11,200 kilograms (24.6 kips) for 50,000 passes plus 10,000 passes of a

CH-47 with a gross weight of 22,680 kilograms (50,000 pounds). The runway length is less than

1,220 meters (4,000 feet). Subgrade is a poorly graded sand with a design CBR of 16; in-place density

of the subgrade is 90 percent to a depth of 3 meters (10 feet).

(2)

From Figure 10-3, the total pavement section required is 240 millimeters (9.5 inches).

(3) From Table 8-3, the minimum required surface and base thicknesses are 50 and

152 millimeters (2 and 6 inches), respectively, for a total of 203 millimeters (8 inches).

(4) Use a 240-millimeter (9.5-inch) pavement section consisting of 50 millimeters (2 inches) of

AC surface and 190 millimeters (7.5 inches) of 100 CBR base on subgrade to provide the

241 millimeters (9.5 inches) required above the subgrade.

10-3

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