C. M. WORKS & C. D. WORKS
and
DESIGN PRINCIPLES OF DROPS & REGULATORS
by
J. Gunakar Rao
M.E., MIE, MISTE
E.E., C.D.O., VJA.
CRITERIA FOR SELECTION
OF CM & CD WORKS
➢ RELATIVE ELEVATIONS OF CANAL AND DRAINAGE BED
LEVELS AND FSL/ HFL.
➢ HYDRAULIC REQUIREMENTS
➢ FOUNDATION CONDITIONS
➢ MEN AND MATERIAL RESOURCES AND CONVENIENCE OF
CONSTRUCTION
➢ ECONOMIC CONSIDERATIONS
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REGULATION AND
CONTROL WORKS
• REGULATION AND CONTROL WORKS ARE STRUCTURES WHICH ARE
CONSTRUCTED TO ADMIT AND REGULATE REQUIRED DISCHARGE IN TO THE
CANAL NET WORK.
• TYPES OF REGULATION AND CONTROL WORKS
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HEAD REGULATOR
CROSS REGULATOR
OUTLET
MEASURING DEVICE
DROP
CANAL ESCAPE
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HEAD REGULATOR
These structures are as the name indicates, at the
heads of canals, branches, distributaries or minors. Their
function is to admit or regulate the discharge in to the
Off-taking canal.
Regulators
Head
regulator
Cross
Regulator
In – Fall Regulator
Out fall
Escape
Regulator
Regulator
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HEAD REGULATOR
• TO ADMIT AND REGULATE THE DISCHARGE INTO THE OFF
TAKING CANALS AT THE START.
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CROSS REGULATOR
• TO DIVERT AND REGULATE THE REQUIRED DISCHARE
INTO OFF TAKING CANALS LOCATED ACROSS THE
PARENT CANAL.
• GENERALLY LOCATED IMMEDIATELY AFTER A MAJOR
OFF TAKE. IF THERE ARE NO MAJOR OFF TAKES MAY BE
PROVIDED AT SUITABLE INTERVALS.
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OUTLET
• TO RELEASE REQUISITE QUANTITY OF WATER IN TO MINORS/ FIELD
CHANNELS.
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MEASURING DEVICES
• TO MEASURE VOLUME OF WATER FLOWING THROUGH A CANAL.
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DROP
• TO NEGOTIATE DIFFERENCE IN BED LEVELS AND TO
MAINTAIN UPSTREAM WATER LEVELS.
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• GLACIS DROP
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CANAL DROP
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OFF TAKE SLUICE
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HEAD REGULATOR (BIS 6531:1994 )
THESE STRUCTURES ARE AS THE
NAME INDICATES ,AT THE HEADS
OF CANALS,BRANCHES,
DISTRIBUTARIES & MINORS.
THEIR FUNCTION IS TO ADMIT&REGULATE
THE DISCHARGE INTO THE OFFTAKING
CANAL.
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HEAD REGULATOR – MADDUVALASA
RESERVOIR PROJECT – R.M.C
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CROSS REGULATORS
➢ TO DIVERT AND REGULATE THE REQUIRED DISCHARE
INTO OFF TAKING CANALS LOCATED ACROSS THE
PARENT CANAL.
➢ GENERALLY LOCATED IMMEDIATELY AFTER A MAJOR
OFF TAKE. IF THERE ARE NO MAJOR OFF TAKES MAY BE
PROVIDED AT SUITABLE INTERVALS.
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REGULATOR WITH HOIST BRIDGE
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CANAL ESCAPE
➢ TO DISCHARGE EXCESS WATER OUT OF CANAL SYSTEM
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CROSS REGULATORS
1.
2.
3.
4.
5.
In order to negotiate change in bed width & FSD,
When the reduction in Q is > 10% of, a cross regulator has to
be provided.
Constriction of less than 60 to 50% is permitted
By proposing crest with raised crest
Vent way is arrived at using drowning ratio as per *Malikpur*
graph.
Q = C Bt D3/2
Where C = coefficient depending upon the drowning
ratio
Bt = Clear throat width between abutments
D = Depth of crest below U/S T.E.L
Road way: Road way consists of DLB & SLB as per
requirement.
The bottom of road slab shall be with minimum
vertical clearance above U/S FSL.
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LENGTH OF CISTERN:
The length of cistern shall be checked for energy dissipatio
for different discharging conditions viz.,100%,
75%,50%,25%,15%,10% and 5% for one gate opening and
two gate openings etc,.
UPLIFT PRESSURES:
➢The uplift pressures at different sections are calculated by
using Khosla’s Theory and the floor thickness calculated
for the uplift pressure..
➢ The wings & returns are designed for an earth pressure
computed as per TVA procedure.
➢ Weep holes with inverted filter shall be provided above
bed level at 2.0m C/C in wings and returns.
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SCOUR DEPTH CALCULATIONS:
With factor of safety of 1.25 on U/S & 1.5 on D/S
In the initial stages of the opening of the regulator
shutters, where there is no water in rear, the water will shoot
out D/S till the tail water builds up. So it is possible in initial
stages for the bed to get scoured out in order to dissipate this
excess velocity, two or three rows of friction blocks may be
Provided on the D/S solid apron.
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EXIT GRADIENT
➢ The length of the apron floor should be such that
the two cutoffs at the U/S and D/S ends should give
a minimum Exit Gradient of 1 in 4 to 1 in 7
depending on type of soil.If,however,the apron
length is found inadequate,the D/S cutoff wall may
be deepened.
➢ Exit Gradient is given by the Formula,
GE =H/d x(1/  √λ )
Where λ =(1 + √ 1+α2 ) / 2 and α = b/ d .
➢ Safe Exit Gradients for different type of soils
Shingle
1/4 to 1/5
Coarse Sand
1/5 to 1/6
Fine Sand
1/6 to 1/7
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THANK YOU