Limited subgrade frost penetration design - cont'd

UFC 3-260-02

30 June 2001

(c) The required base thickness c for zero frost penetration into the subgrade from

Equation 20-12 is as shown in the following tabulation:

Frost Penetration, a

PCC Thickness, p

Combined Base Thickness, c

Traffic Area

mm (in.)

A

2,235 (88)

599 (23.6)

1,636 (64.4)

B

2,235 (88)

557 (23.5)

1,638 (64.5)

C

2,286 (90)

490 (19.3)

1,796 (70.7)

D

2,311 (91)

384 (15.1)

1,928 (75.9)

(d) Compute water content ratio r.

For r $ 2.0, for type A and B traffic areas, use r = 2.0 with Figure 20-6. For r $ 3.0, for type C

and D traffic areas use r = 3.0 with Figure 20-6. Determine the design combined base-course

thickness b and amount of subgrade frost penetration s for the combined base thickness.

Traffic Area

Design Base Thickness b, mm (in.)

Subgrade Frost Penetration s, mm (in.)

A

1,054 (41.5)

287 (11.3)

B

1,054 (41.5)

287 (11.3)

C

988 (38.9)

259 (10.2)

D

1,059 (41.7)

277 (10.9)

(e) Compare these design pavement thicknesses with those obtained with the

reduced subgrade strength design procedure.

Reduced Subgrade Strength Method

Limited Subgrade Frost Penetration

Combined

Base

Total

Base

Total

PCC

Traffic

PCC

mm (in.)

Area

mm (in.)

A

579 (22.8)

1,158 (45.6)

599 (23.6)

1,054 (41.5)

1,654 (65.1)

B

577 (22.7)

1,153 (45.4)

597 (23.5)

1,054 (41.5)

1,651 (65.0)

C

483 (19.0)

965 (38.0)

490 (19.3)

988 (38.9)

1,478 (58.2)

D

386 (15.2)

772 (30.4)

384 (15.1)

1,059 (41.7)

1,443 (56.8)

20-24