Environmental Engineering Reference
In-Depth Information
(a)
WELL GRADED
BASE SOIL
FILTER
(b)
POORLY GRADED
BASE SOIL
FILTER
Figure 9.4.
Filtering and self filtering concepts, (a) well graded base soil, (b) gap graded, or concave
graded soil, deficient in medium sized particles.
0.075mm
4.75mm
75mm
100
90
Soil with 'smooth'
gradation with a
flat 'tail' in the finer
80
70
60
50
Gap-graded soil
40
30
20
10
0
0.001
0.01
0.1
1
10
100
Particle Size (mm)
CLAY TO SILT
SAND
GRAVEL
Figure 9.5.
Soils gradation types which are susceptible to suffusion or internal instability.
