This document discusses diversion head works, including: 1. Headworks divert water from rivers into canals and come in two classes - storage and diversion. Diversion headworks raise water levels and regulate flow into canals. 2. Components of diversion headworks include weirs, barrages, divide walls, fish ladders, channels, and sluices. Weirs and barrages both raise water levels but barrages use gates to control water. 3. Failures of weirs can occur due to piping, uplift, suction waves, or scouring. Design of weirs on permeable foundations must consider theories like Bligh's creep theory and Lane's weighted

1. Lecture – 9
Diversion Head Works

2. • Headwork & Its Classes
• Functions & Classes of Diversion Headwork
• Weir & Barrage
• Layout of Diversion Head Works
• Components of Diversion Head Works & their Functions
• Causes of Failures of Weirs & Their Remedies
• Design of Weir on Permeable Foundations
– Bligh’s Creep Theory
– Lane’s Weighed Creep Theory
– Solved Example
Diversion Head Works

3. Headwork & its Classes
Headwork Hydraulic structure which supplies water to off-taking canal
Classes of Headwork
1. Storage Headwork
Comprises the construction of a dam across a river
Water stores during excess supplies releases during demand
2. Diversion Headwork
Serves to divert the required supply into the canal from river

4. Functions Classes of Diversion Headwork
1. Functions of Diversion Headwork
Raises the water level in the river
Regulates the intake of water into the canal
Controls the silt entry into the canal
Reduces fluctuations in supply level of river
Stores water for tiding over small periods of short supplies
2. Classes of Diversion Headwork
a) Temporary Spurs/Bunds
Temporary structure constructed every year after floods
b) Permanent Weirs Barrages
Permanent structure if designed properly

5. Weir Barrage
1. Weir
Solid obstruction across the river to raise water level
2. Barrage
Function of barrage is same as weir, but the heading water by gates

6. Components of a Diversion Headwork their Functions
1. Weir or Barrage
Gravity Weir
o Vertical Drop Weir
o Sloping Weir
o Parabolic Weir
Non-gravity Weir
2. Divide Wall or Divide Groyne
3. Fish Ladder
4. Pocket or Approach Channel
5. Scouring Sluices
6. Canal Head Regulator
7. River Training Works i.e. Marginal Bunds Guide Banks
8. Silt Presentation Devices
Note:
Refer to Detail Description of Each Component,
Chapter 12 Diversion Headworks, Punmia B.C. ,
“Irrigation Water Power Engineering”,
Standard Publishers, Delhi

7. Components of a Diversion Headwork their Functions

8. Components of a Diversion Headwork their Functions

9. Components of a Diversion Headwork their Functions

10. Components of a Diversion Headwork their Functions

11. Components of a Diversion Headwork their Functions

12. Causes of Failures of Weirs Their Remedies
1. Piping
2. Rupture of Floor due to Uplift
3. Rupture of Floor due to Suction Caused by Standing Wave
4. Scour on the Upstream Downstream of the Weir

13. Bligh’s Creep Theory
Assumptions
1. Hydraulic slope or gradient is constant throughout the impervious
length of the apron
2. The percolating water creep along the contact of the base profile of
the apron with the sub-soil, losing head enroute, proportional to
length of its travel called Creep Length. It is the sum of horizontal
vertical creep
3. Stoppage of percolation by cut off (pile) possible only if it extends
up to impermeable soil strata
Considerations
For portion of floor upstream of barrier only nominal thickness
need to be provided since the weight of water will counterbalance
the uplift pressure.
A certain minimum length of impervious floor is always necessary
to the downstream of the barrier (thickness of downstream floor
for worst condition)

14. Bligh’s Creep Theory
Limitations
1. No distinction between horizontal vertical creep
2. Hold good as long as horizontal distance between piles is greater
than twice their depth
3. Did not explain the idea of exit gradient - safety against
undermining cannot simply be obtained by considering a flat
average gradient but by keeping this gradient well below critical
4. No distinction between outer inner faces of sheet piles or the
intermediate sheet piles, whereas from investigation it is clear that
the outer faces of the end sheet piles are much more effective than
inner ones
5. Loss of head does not take place in the same proportions as the
creep length. Also the uplift pressure distribution is not linear but
follows a sine curve
6. Does not specify the absolute necessity of providing sheet pile at
d/s, whereas it is essential to prevent undermining

15. Lane’s Weighed Creep Theory
Bligh recommended that in calculating creep length, the depth of
every cut-off be multiplied by a factor 2, however Lane analyzed over
200 dams all over the world evolved his “Weighted Creep Theory”,
and proposed:
a weight of 3 for vertical creep 1 for horizontal creep
effective
creep length is calculated by multiplying the vertical offsets by 3
adding it to the horizontal length

16. Bligh’s Creep Theory (Example)
Note: Specific gravity of floor material is 2.24, and
Specific weight of water is 1 ton/m3