UET Peshawar CE-402: Barrage Components and Seepage Theories

This report, prepared for the Civil Engineering course CE-402 at the University of Engineering and Technology Peshawar, focuses on the components and operational aspects of barrages. It begins by defining a barrage and its function as a river regulator, contrasting it with weirs. The report then details the various components of a barrage, including the main barrage portion, sheet piles, inverted filters, flexible aprons, under sluices, divide walls, fish ladders, canal head regulators, silt regulation works, and river training works. Each component's function is thoroughly explained. Furthermore, the report explores the causes of failure in weirs and barrages on permeable foundations, categorizing failures due to subsurface flow (piping or undermining, uplift pressure) and surface flow (hydraulic jump, scouring). Precautions against these failures, such as proper design of the impervious layer, use of sheet piles, and energy dissipaters, are also discussed. Finally, it introduces the theories of seepage and their importance in the design of hydraulic structures like barrages. This report provides comprehensive information on the design, operation, and potential failures of barrages, making it a valuable resource for civil engineering students.

Department of Civil Engineering
University of Engineering and Technology Peshawar
CE-402: Irrigation Engineering and
Water Management
Lecturer: Alamgir Khalil
8th Semester (4th Year)
Civil Engineering
Spring 2022
Lecture 9
Components of a Barrage,
Theories of Seepage
1

Department of Civil Engineering
University of Engineering and Technology Peshawar
Barrage
2
➢ If most of the ponding is done by gates and a smaller or nil part of it is done
by the raised crest, then the barrier is known as a barrage or a river regulator.
➢ A barrage is a diversion structure across a river fitted with a series of gates
over its entire length for creating the required ponding.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Barrage (cont.)
3
➢ A barrage is a type of low-head diversion dam which consists of a number of large
gates that can be opened or closed to control the amount of water passing
through. This allows the structure to regulate and stabilize river water elevation
upstream for use in irrigation and other systems.
➢ The main difference between a weir and a barrage is of gates, that is the flow in
barrage is regulated by gates and that in weirs, by its crest height. Barrages are
costlier than weirs.
Kotri Barrage

Department of Civil Engineering
University of Engineering and Technology Peshawar
Barrage (cont.)
4
✓ It diverts the required quantity of water from the river to the channels.
✓ It raises the level of supply so that water can reach the area proposed for
irrigation by gravity flow.
✓ It allows proper silt control.
✓ It provides permanent headworks for the canals in order to protect them
during floods by providing for complete closure.
✓ It provides better regulation than a weir.
➢ A barrage serves the following purposes:
Islam Headworks Balloki Headworks Sulemanki Headworks

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage
5
The following are the components of a barrage:
1) Main barrage portion
2) Sheet piles
3) Inverted filter
4) Flexible apron
5) Under sluices
6) Divide wall
7) Fish ladder
8) Canal Head Regulator
9) Silt Regulation Works
10) River Training works

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
6

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
7
Main Barrage Portion
➢ This is the main body of the barrage
normally of R.C.C. slabs which support the
steel gates. In cross-section it consists of;
✓ U/S concrete floor to lengthen the path
of seepage and to protect the middle
portion where the piers, gates and bridge
are located.
✓ A crest at the required height above the floor on which the gates rest in their closed
position.
✓ U/S glacis having the necessary slope to join the u/s floor level to the highest point,
the crest.
✓ D/S glacis of suitable shape and slope. This joins the crest to the d/s floor level
(which may be at riverbed level or below). The hydraulic jump forms on the glacis.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
8
Main Barrage Portion
✓ D/S floor is built of concrete and is constructed so as to contain the hydraulic jump.
Thus, it takes care of turbulence which would otherwise cause erosion. It is also
provided with friction blocks of suitable shape and at distances determined by
hydraulic model experiments in order to increase friction and destroy residual K.E.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
9
➢ An inverted filter is provided between the d/s sheet piles and the flexible
protection.
➢ It typically consists of 6” sand, 9’’ coarse sand and 9” gravel. The filter material may
vary with the size of the particles forming riverbed. It is protected by placing
concrete blocks of sufficient weight and size, over it.
Inverted Filter
➢ Its primary function is to
check the escape of fine soil
particles in the seepage
water. In the case of scour, it
provides adequate cover for
the d/s sheet piles against
the steepening of exit
gradient.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
10
➢ From the functional point view in
a barrage, these are classified
into three types i.e.
✓ u/s sheet piles
✓ intermediate sheet piles
✓ d/s sheet piles
Sheet Piles
➢ There are generally three or four sheet piles. These are made of mild steel, each
portion being with sufficient width and in thickness of the required length and
having grooves to link with the other sheet piles.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
11
➢ u/s sheet piles are located at the u/s end of the u/s concrete floor. These piles are
driven into the soil beyond the maximum possible scour that may occur. Their
functions are:
✓ To protect the barrage structure from scour.
✓ To reduce uplift pressure in the barrage floor.
Upstream Sheet Piles
Intermediate Sheet Piles
➢ They are situated at the end of u/s and d/s glacis and
serve as second line of defense. In case of the u/s or
d/s sheet piles collapse due to advancing scour or
undermining, then these sheet piles give protection
to the main structure of the barrage. The
intermediate sheet piles also help to lengthen the
seepage path and reduce uplift pressure.

Department of Civil Engineering
University of Engineering and Technology Peshawar
Components of a Barrage (cont.)
12
Downstream Piles
➢ These are placed at the end of the d/s concrete floor and their main function is to
check the exit gradient. Their depth should be greater than the maximum possible
scour.
Shutters or Gates
➢ The gates or shutters are made of steel
plates welded on the fabricated steel
framework.
➢ Their function is:
✓ To maintain pond level.
✓ To raise the water level during low
supplies.