Spillways ppt...

1. SPILLWAYS
PRESENTED BY :
ARADHYA SHASTRI
ROLL NO. – 140970104009
M.E. 4th Year

2. CONTENT
1. INTRODUCTION
2. TYPES OF SPILLWAYS
I. FREE OVER FALL SPILLWAY
II. OGEE SPILLWAY
III.SIDE CHANNEL SPILLWAY
IV.CHUTE SPILLWAY

3. INTRODUCTION
• Before knowing about Spillways, we will know about where
the spillway is built. So spillway is built over the dam and dam
is constructed on a eservoir of the river to control the flow and
prevent the area from flood.
• Generally the excess water is drawn from the top of the
reservoir created by the dam amd conveyed back to the iver
through the artificially created waterways, these waterways are
of sufficient capacity to convey the excess water, and these
structures are thus known as Spillways.
• In a spillway, flood water flows from high elevation to low
elevation through a passage, the higher elevation is the
reservoir surface whereas the lower elevation is the sdea level.

4. TYPES OF SPILLWAYS
• Spillway are generally classified according to there most
prominent features. The common types of Spillways used are
as follows :
1. FREE OVERFALL (STRAIGHT DROP) SPILLWAY
2. OVERFLOW (OGEE) SPILLWAY
3. CHUTE (OPEN CHANNEL/TROUGH) SPILLWAY
4. SIDE CHANNEL SPILLWAY
5. SHAFT (DROP INLET/MORNING GLORY) SPILLWAY
6. TUNNEL (CONDUIT) SPILLWAY
7. SIPHON SPILLWAY
8. STEPPED SPILLWAY

5. FREE OVERFALL SPILLWAY

6. FREE OVERFALL SPILLWAY
• This is the simplest type of spillway which is constructed in
the form of low hieght weir having downstream face either
vertical or nearly vertical. Water drops freely from the crest
and the underside of the falling rapple is vertical. Water drops
freely from the crest and the underside of the falling rappe is
ventilated sufficiently to presvent a pulsating, fluctuating, jet.
• Occasionally, the crest is extended in the form of an
overwhelming lip to direct the small discharge away from the
face of overfall section.
• This type of spillway is not recommended for high head since
the vibrations caused by piping or undermining.

7. OVERFLOW SPILLWAY

8. OVERFLOW SPILLWAY
• This is the most common type of spillway provided on gravity dams.
The profile of the spillway is Ogee or ‘S’ shaped.
• The overflowing water is guided smoothly over the crest and profile
of the spillway so that the overflow water doesn’t break contact
with the spillway.
• In addition to cavitation,vibration from the alternate making and
breaking of contact between the water and face of the dam may
result in serious structural damage.
• The essential difference between straight drop spillway and the
ogee spillway should be clearly noted. In former type, jet clearly
away from the face of spillway and the gap between the gap and
the face is kept ventilated, whereas in the latter,thr falling water is
made to guide over the spillway provided.
• This reserve curve turns flow on the apron of a stilling basin or into
the spillway discharge channel.

9. SIDE CHANNEL SPILLWAY

10. SIDE CHANNEL SPILLWAY
• A side channel spillway is one in which the flow, after passing over a
wier or ogee crest, is carried away by channel running essentially
parallel to the crest.
• However this flow may differ from that of overflow spillway in that
the flow in the trough may partly submerge the flow over the crest.
Side channel spillway is suitable earth or rockfill dams in narrow
canyons and for other situations where a direct flow is not
permissible.
• Side channel spillway is also the best choice where a long overflow
crest is desired in order to limit the surcharging head and the
abutments are steep.
• This type of spillway i9s also desired where the spillway discharge is
to be connected to narrow discharge channel or a tunnel.

11. CHUTE SPILLWAY

12. CHAIN SPILLWAY
• A chute spillway is one which passes the surplus discharge
through a steep sloped open channel, called a chute or trough
placed either along a dam anutment or through a saddle.
• Generally this type of spillway is provided in earth or rockfill
dams, and isolated from the main dams.
• It’s crest is kept normal to it’s centre line.
• The chute is sometime of consent width, but usually
narrowed for economy and then widened near the end of
reduce discharge velocity.

13. THANK YOU