Table 3.7. Sand Size Bed Material Properties.
Percent of
pIDI
Geometric
Bed Material
Percent
Fall Velocity
Size Range
Mean Size, DI
in this Size
Finer
(m/sec)
(mm)
(mm)
(pI)
.002 - .0625
0.011
0.8
0.8
0.01
0.0001
.0625 - .125
0.088
4.4
5.2
0.39
0.0061
.125 - .250
0.177
14.2
19.4
2.51
0.0183
.250 - .500
0.354
74.9
94.3
26.51
0.0457
.500 - 1.00
0.707
5.0
99.3
3.54
0.0884
1.00 - 2.00
1.41
0.5
99.8
0.71
0.198
2.00 - 4.00
2.83
0.2
100.0
0.56
0.335
TOTAL
100
34.2
The fall velocity is determined with the use of Figure 3.1 at 60o F. For the geometric mean size
of the first size range Di = 0.011mm, ω = .0001 m/s, similarly Di = 0.707 mm, ω = 0.0884 m/s
etc. The results are shown in Table 3.7.
The sand size distribution is plotted on log-probability paper in Figure 3.24 from which the
following values can be obtained:
=
0.33 mm
D50
D16
=
0.24 mm
=
0.46 mm
D90
D84
=
0.44 mm
10
10
8
6
5
4
3
2
1
1
0.8
0.6
0.5
0.4
0.3
0.2
0.1
0.1
100
90
80
70
60
50
40
30
20
10
0
Percent Finer
Figure 3.24. Bed material size distribution curves.
3.53
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