A Treatise On The Principles And Practice Of Dock Engineering
Forfatter: Brysson Cunningham
År: 1904
Forlag: Charles Griffin & Company
Sted: London
Sider: 784
UDK: Vandbygningssamlingen 340.18
With 34 Folding-Plates and 468 Illustrations in the Text
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232
DOCK ENGINEERING.
As illustrative of the variation in the amount of material carried in
suspension by tidal rivers the following table is inserted : — *
TABLE XXL—Showing Amount of Material in Suspension in 1 Gallon
of Mersey Water at Various Times of the Tide.
Flood Tide. Flood Tide. Ebb Tide. Ebb Tide. Ebb Tide.
A.M. Grains. A.M. Grains. P.M. Grains. P.M. Grains. P.M. Grains.
8.45 7-0 11.15 12-95 1.15 5-25 3.45 19-95 6.15 30-8
9.0 8-4 11.30 12-95 1.30 5-25 4.0 13-65 6.30 30-45
9.15 20-3 11.45 15-05 1.45 6-3 4.15 1-05 6.45 54-25
9.30 22-92 12.0 15-75 2.0 3-5 4.30 5-6 7.0 43-05
9.45 20-12 P.M. 2.15 1-75 4.45 14-0 7.15 38-85
10.0 24-85 2.30 2-8 5.0 34-65 7.30 46 '55
10.15 24-15 12.15 12-25 2.45 2-8 515 18-9 7.45 525
10.30 23-62 12.30 10-85 3.0 10-85 5-30 25-2 8.0 32-2
10.45 17-5 12.45 9-8 3.15 5-95 5.45 30-8 8.15 46 ‘55
11.0 21-7 1.0 9-8 3.30 8-4 6.0 22-05 8.30 38-5
The sediment in the River Hooghly, at time of flood, amounts to 3
inches per cubic foot. In the River Plate it is 1 in 10,000 by weight.
Great variation is to be found in the rate at which silting takes place.
The quantity which collects in the Tilbury tidal basin is stated to be 1 J, to
2 inches daily. At Avonmouth Dock entrance, the accumulation amounts
to only 15 inches per month.
Purely maintenance dredging at some ports reaches very high figures.
At Kidderpur, it is 37,000 cubic yards per annum; at Bordeaux, 380,000
cubic yards; at Ostend, 500,000 cubic yards; at Hull, 830,000 cubic yards;
and at Glasgow, 870,000 cubic yards per annum.
The power of currents to disturb deposited material may be gauged
from the following table which indicates the critical velocity, or the
velocity at which moving water just begins to exert its erosive power. To
TABLE XXII.
Material.
Critical Velocity.
Silt, mud, very soft clay,
Eine sand, loam, .
Ordinary clay,
Coarse sand, fine gravel,
Fairly coarse gravel,
Coarse ballast (l-inch pebbles),
Large shingle (IJ-inch pebbles),
Heavy shingle, broken stone,
Soft rock, ....
.3 inches per second.
7 »
12
2 feet ,,
3 »
4
5 „
* A. G. Lyster on “ Manchester Ship Canal,” Min. Proc. Liverpool Engineering
Society, vol. vii.