I

C

L

Surface

Pipe

Course

A

D

B

C

Base Course

Subgrade

Original Ground Surface

Stage 1:

dx

x

0 < *U *≤ 50%

A

.

D

t + dt

t

Stage 2:

H

50% < *U *≤ 100%

2*S *- 2*US *+ 1

- *S*2 ln

B

L tan α

α

(2 - 2*U *)(*S *+ 1)

C

where *U *= drained area/total area

Stage 1 (U ≤ 50%)

A

(Fig. 12)

D

t

2*tkH*

dh

H

0.8

h

3

t + dt

B

L tan α

α

α = angle of slope of base layer

C

Stage 2 (U ≥ 50%)

U.S. Standard Sieve Numbers

Hydrometer

6" 4"

2"

1"

10

40

200

3/8"

100

0

80

20

60

40

k = 0.0035 cm/s (10 ft/day)

40

60

1.06 (3000)

0.35 (1000)

20

80

0.039 (110)

100

0

100

10

1

0.1

0.01

0.001

Grain Size (mm)

Gravel

Sand

Cobbles

Silt or Clay

Coarse

Fine

C'rse

Medium

Fine

18