UFC 3-260-02

30 June 2001

the F-15, 4,000 passes of the C-17, and 4 pass of the B-52. (Since the B-52 is included in the design,

the runway must be 61 meters (200 feet) wide.) On-site and laboratory investigations have yielded the

following data required for design: (1) the subgrade material is classified as a silty sand (SM); (2) the

modulus of soil reaction, k, of the subgrade is 54 kPa/mm (200 pci); (3) a nearby source of crushed

gravel meets the requirements for base course; (4) frost does not enter subgrade material; and

(5) 90-day concrete flexural strength, R, is 4.8 MPa (700 psi).

b. Example Design, Slab on Grade. Figure 12-8 is entered with the subgrade k = 200 pci, concrete

design flexural strength R = 700 psi, and the pavement thickness is determined for the various traffic

areas and overruns as follows:

406 (16.0)1

A

B

406 (16.0)

C

302 (12.0)

D and overruns

229 (9.0)

1

Fractional values would be rounded up to the nearest full- or half-inch for design.

c. Example Design, Slab on Unbound Base. For comparison purposes, designs are developed

below for three base-course thicknesses. Field plate bearing tests conducted in a test section to

establish the modulus of soil reaction for three thicknesses of base course give k values of 68 kPa/mm

(250 pci) for a 152-millimeter (6-inch) base, 81 kPa/mm (300 pci) for a 305-millimeter (12-inch), and

95 kPa/mm (350 pci) for 460-millimeter (18-inch) base. These values are supported by Figure 8-1 and

are thus selected for design. Figure 12-8 is entered with the design flexural strength, modulus of soil

reaction, and traffic areas to determine the required concrete pavement thicknesses. Thicknesses for

shoulders were determined from Figure 12-17. The thicknesses for this example are summarized as

follows:

(1)

(2)

(3)

(4)

(5)

(6)

(7)

150-mm (6-in.)

68

370

370

290

215

150

base

(250)

(14.5)

(14.5)

(11.5)

(8.5)

(6)

300-mm (12-in.)

81

340

340

260

200

150

base

(300)

(13.5)

(13.5)

(10.5)

(8.0)

(6)

460-mm (18-in.)

95

330

320

250

200

150

base

(350)

(13)

(12.5)

(10)

(8.0)

(6)

Note: Final thickness should be rounded values.

1

Use minimum thickness of 150 millimeters (6 inches) for shoulders.

The final selection of concrete pavement thickness must be based upon a study of the cost of importing

and placing base course versus savings in concrete pavements.

12-3

Integrated Publishing, Inc. |