A Seminar ON Spill Ways

A
SEMINAR
ON
SPILL WAYS
SUBMITTED TO:- SUBMITTED BY:-

ER. BALKISHAN DHUNDHARA YASIN HAWARI
( H.O.D. ) CIVIL ENGG. DEPT. Roll No. 13esgce041
CE (2013-14) 4th Year
SPILL WAYS
When the water in the reservoir increases, the large

accumulation of water endangers the stability of the dam
structure. To avoid this a structure is provided in the body of
a dam or near the dam or periphery of the reservoir. This
structure is called as spillway.
Mainly used to discharge water during flood period.
Requirements:
Provide structural stability to the dam under all condition
Should able to pass the designed flood without raising the
reservoir level above H.F.L.
Should have an efficient operation
Should be economical
FUNCTION
The spillway has the function of
discharging all the water not utilized
for generation. The maximum
discharge capacity of the spillway is
62.2 thousand m3/s; 40 times greater
than the mean discharge of the
Iguau Falls.
LOCATION OF SPILLWAY
Generally, the spillways are provided
at the following places
Spillways may be provided within
the body of the dam.
Spillways may sometimes be
provided at one side or both sides of
the dam.
Sometimes by-pass spillway is
provided which is completely
separate from the dam.
TYPES OF SPILLWAYS
Overfall spillway
Chute spillway
Saddle spillway
Shaft spillway
Side channel spillway
Emergency spillway
siphon spillway
FIGURES
Overfall spillway: Chute spillways:
that allows water to pass over its crest In this type water is conveyed from the
widely used on gravity, arch, & reservoir to the river or to nalla below
buttress dam the dam through an excavated open
This is a simplest type channel, through fairly steep slope
Overfall spillways
SHAFT SPILLWAY
The shape is just like a funnel .
water drops through a vertical shaft in a the foundation material to a
horizontal conduit that conveys the water past the dam.
Lower end of shaft is turned at right angle and then water taken out
below the dam horizontally.
Also called as glory hole spillway.
SADDLE SPILLWAYS
This type is mainly used when other types are not favourable.
In some basins formed by a dam, there may be one or more natural
depressions or saddles in the rim of the basin, which can be used as
spillway.
It is essential that the bottom of the depression should be at full reservoir
level.
It is usually necessary for the saddle to be on firm rock.
SIDE CHANNEL SPILLWAY
When the dam is not rigid and it is undesirable to pass flood
water over the dam , this type of spillway is used.
After passing crossing over the spillway crest ,water flows
parallel to the crest.
SIPHON SPILLWAYS
It is designed by the principle of a siphon.
When water rises over the FRL then water start spilling.
There is a air vent for removing the entrapped pressure from the
water.
EMERGENCY SPILLWAY
This type is rarely used .

Extra spillways provided on a project in rare case
of extreme floods(emergency)
Used to convey frequently occurring outflow
rates.
ADVANTAGES
Very stable. The likelihood of serious
structural damage is less than for other
types of structures.
The rectangular weir is less likely to be
clogged by debri,s than the openings or
other structures of comparative discharge
capacities.
They are relatively easy to construct. The
concrete block type can be built with farm
labor, while the reinforced concrete or
steel sheet piling type usually
DISADVANTAGES
It is more costly than some other
types of structures where the
required discharge capacity is less
than 100 c.f.s. and the total head or
drop is greater than 10 feet.
It is not a favorable structure where
temporary spillway storage is needed
to obtain a large reduction in
discharge.
A stable grade below the structure is
SAFETY
Spillway gates may operate suddenly without warning,
under remote control. Trespassers within the spillway run
the risk of drowning. Spillways are usually fenced and
equipped with locked gates to prevent casual trespassing
within the structure. Warning signs, sirens, and other
measures may be in place to warn users of the downstream
area of sudden release of water. Operating protocols may
require "cracking" a gate to release a small amount of
water to warn persons downstream.
The sudden closure of a spillway gate can result in the
stranding of fish, and this is also usually avoided.
CONCLUSION
Hydroelectric developments include
flood-control structures designed to
let excess water escape safely from
the reservoir. This "safety valve"
prevents water from spilling over the
dam crest. It takes the form of a
spillway, a weir or sometimes a
combination of both.
Th a n k
y o u

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SUBMITTED TO:- SUBMITTED BY:-

When the water in the reservoir increases, the large

This type is rarely used .

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