River and Canal Engineering, the characteristics of open flowing streams, and the principles and methods to be followed in dealing with them.Bellasis, E. S. (Edward Skelton)
Science
River and Canal Engineering, the characteristics of open flowing streams, and the principles and methods to be followed in dealing with them.
Bellasis, E. S. (Edward Skelton)
Canals; Hydraulic engineering; Rivers
The following is a curious case of misconception of the action
of spurs. In 1909 the river Indus was eroding its right bank and
threatening to destroy the town of Dera Ghazi Khan. A clump of date
palms formed a promontory and resisted erosion to some extent. A
suggestion was made--by an engineer of eminence who had formerly been
consulted in the case--to the effect that the date palms be removed,
the reason given being that they caused disturbance and scour. On this
principle spurs would have to be made not to protect a bank but to
cause it to be eroded.
3. =Continuous Lining of the Bank.=--The lining or protection of a
bank may be of stone or brick pitching (figs. 12 and 13), loose stone
(fig. 14), fascines (fig. 15), turfing, plantations, brushwood, or of
other materials laid on the slopes. Before protecting a bank it is
best to remove irregularities and bring it to a regular line. This can
generally be done most easily by filling in hollows, but sometimes it
is done by cutting off projections. It is also necessary to make the
side slope uniform. Where the slope is as shown by the dotted lines in
figs. 12 to 14, filling in can be effected, but cutting away the upper
part of the slope is also feasible. Such cutting away has been proposed
as a remedy in itself in cases where the steep upper part of the slope
was falling in, but it is not much of a remedy.
Stone pitching may rest, if boats are required to come close to the
bank, on a toe wall of concrete, as in fig. 13,[9] or otherwise on a
foundation of loose stone, as in fig. 12. When concrete is used the
bed is dredged to such a depth as will provide against undermining by
scour. Sloping boards attached to piles are placed along the front face
and the concrete is thrown in under water. The slope of stone or brick
pitching is usually from 2 to 1 to 1 to 1, but it may be as steep as
½ to 1. The earth behind the pitching must be well rammed in layers.
In order to prevent the earth from being eaten away by the water which
penetrates through the interstices of the stone or brick, a layer, 3
to 6 inches thick, of gravel or ballast is placed over the earth and
rammed. When loose stone is used, dredging is not necessary, but the
stone is allowed to gradually sink down and more is added at the top. A
certain proportion of the stones should be of large size.
[Illustration: FIG. 12.]
[Illustration: FIG. 13.]
When fascining is used, long twigs are made into bundles and tied up
at every 2 feet so as to form fascines about 4 to 6 inches thick, and
these are laid on the slopes and secured by pegs driven in at short
intervals, between the fascines.
[Illustration: FIG. 14.]
[Illustration: FIG. 15.]
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account