In this article, we will discuss divide wall.
A divide wall is constructed parallel to the direction of the flow of the river to separate the weir section and the under sluices section to neglect cross flows. It is also known as groyne or groyne wall.
If there are under sluices on both sides, there are two divided walls.
In other words, a divide wall is a masonry or concrete wall constructed at a right angle to the axis of the weir or barrage.
On the upstream side, the wall is extended just to cover the canal head regulator and on the downstream side, it is extended up to the launching apron.
Commonly, a cantilever retaining wall is used as a divide wall to resist the pressures exerted by silt and water.
2. Functions of Divide Wall
The function of the divide wall is as follows:
1. It separates the floor of the scoring sluices from that of the weir proper which is at a higher level.
2. It gives a silt pocket in front of the canal head regulator so that silt gets deposited in it and relatively clear water enters the canal.
3. It Separates the pocket upstream of the head regulator to ease scouring operation.
4. It stops the production of cross currents and the flow parallel to the weir axis.
5. It gives a straight approach through the pocket and thus supports concentrating the scouring action of the under sluices for washing out the silt deposited in the pocket.
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3. Designed Conditions
This wall should be designed for the following conditions:
(i) Silt pressure up to full tank level on the face opposite to the face placing near the head regulator and low possible or no water on the face placing near the head regulator.
(ii) During high floods the water level behind the weir must be taken about 1 m to 2 m up the level of water behind the under sluices.
(iii) Top width is assumed to be 1.5 m to 2 m, while the bottom width is noted on the basis that resultant of forces acting on divide wall life within the middle third of the base.
4. Advantages of Divide Wall
1. It helps to stop slit from entering.
2. It acts as a ladder for Fish.
|Read More: Types of Canal|