Environmental Engineering Reference
In-Depth Information
Grain size D
(log scale)
H, mass fraction
between D and 4D
0.6
0.4
0.2
0
1.0
1.0
0.8
0.8
Grading curve
0.6
0.6
Shape curve
0.4
0.4
H
H
0.2
0.2
F
4
0
0
D4D
Figure 9.16.
Method of characterising the shape of a grading curve by Kenney and Lau (1985).
Figure 9.17.
Method of assessing internal instability by Kenney and Lau (1985, 1986), revised criteria
from Kenney and Lau (1986).
Sherard and Dunnigan (1989) suggested issuing filters with a maximum size not greater
than 50 mm and required no less than 40% sand and fine gravel passing 4.75 mm. Ripley
(1986) recommended for filters in contact with the core:
- Maximum size 19 mm;
- Not less than 60% finer than 4.75 mm;
- Not greater than 2% finer than 0.075 mm.
 
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