-Spillways types.pptx

8/9/2019 -Spillways types.pptx

1/32

CE 3205Water and Environmental

Engineering

Spillways


2/32

SPILLWAY

A spillway is a structure used toprovide for the controlled releaseof flows from a dam or levee intoa downstream area, typically being

the river that was dammed.

to prevent overtopping andpossible failure of the dam.

2

Four Mile Dam, Australia

Ogee Spillway


3/32

Upper South Dam, Australia Ogee

Spillway

3


4/32

4Source:http://www.leanhtuan.com/


5/32

5

Hoover Dam Spillway Crest


6/32

6

Hoover Dam Spillway


7/32

New ro!to! Dam NY Steppe"

hute Spillway

7


8/32

Sippel Weir, Australia Drop Spillway


9/32


10/32

Upper South Dam, Australia Ogee

Spillway

"#


11/32

Itaipu Dam, Uruguay hute

Spillway

""


12/32

Itaipu Dam Flip #u$%et

"2


13/32

Common type of spillways:

"$ %ree over fall&straight dropspillways

2$ 'verflow or ogee spillways.3$ (hute spillways

4$ )iphon saddle spillway

"3


14/32

"4

%ree overfall or straight drop spillway

*n this type, water drops freely from the crest.

'ccasionally the crest is e+tended in the form ofoverhanging lip to direct small discharges away from theface of overfall section.


15/32

'gee or overflow spillway

he 'gee spillway is generally provided in rigid dams and forms apart of the main dam itself if sufficient length is available.he overflow type spillway has a crest shaped in the form of anogee or )shape.he upper curve at the crest may be made either larger or sharperthan the nappe.


16/32

(hute spillway

chute spillways are used in flow ways where water is to belowered from one level to another and where it is desirable to

avoid a stilling basin.hese are mostly used with earth dams and have the followingmerit.

*t can be provided on any type of foundations.)implicity of design.

/owever this type of spillway should not be providedwhere too many bends are to be given as per topography.

0affle apron or chute spillway


17/32

)addle spillways

A siphon spillway is a closed conduit system formed in the shape ofan inverted 1.

his type of siphon is also called a )addle siphon spillway.

)iphonic action taes place after the air in the bend over the

crest has been e+hausted.

"7


18/32

euired spillway capacity

)pillway capacity should be eual to the ma+. outflow ratedetermined by flood routing. he following data are reuired forthe flood routing.

*. *nflow flood hydrograph*ndicates rate of inflow respect totime.

**. eservoir capacity curveindicates the reservoir storage atdifferent reservoir elevations.

***.'utflow discharge curveindicates the rate of outflow throughspillways at different reservoir elevations.

"


19/32

O&er'low Spillway

"!

0asic euation flow over weirs,

here

discharge m3&s(dcoefficient of discharge8eeffective length/eactual effective head

/ddesign head/ahead due to velocity of approach9sometimes neglected$

eape HKKNLL )*(' += 2

23 /

eed HLCQ =

ade HHH +=

8e effective width of crest8: net width of crest9clear waterway +

no.of spans$; number of piers


20/32

o!tra$tio! oe''i$ie!ts

Table 1: Pier Contraction Coefficient (Kp)

Table : !butment Contraction Coefficient (Ka)

=>ier contraction coefficient depends on several factors such as shape andlocation of pier nose, thicness of piers and velocity of approach.=Abutment contraction coefficient depends on factors such as shape of

abutment and velocity of approach.


21/32

Design head, Hd

2"

23 /

edd LC

QH =

Downstream profile

d&s profile of spillway can be represented by

x,y coordinates of the point on the spillwaysurfaceHddesign headK,n constant, depend on inclination of theupstream face of spillway


22/32

22

Different inclination of upstream face of spillway

=%or overspillway&ogee, the upstream face is vertical

he slope of the d&s face of theoverflow dam usually varies in therange of #.7?" to #.?"

@ is total fall from the upstream

water level to the floor level

> is height of spillway crest abovethe bed.

depth of flow at toe is radius

B is velocity of flow at toe


23/32

23

80

1

.=dxdy

slope of the d/s face of the overflow section


24/32

C. vs.

24


25/32

Cd. vs. (P/Hd)

(P/Hd)>1.33 velo!ity is "e#le!ted


26/32

$ailwater %&&e!t o" C

26


27/32

Pro(lem )*

>roblem #"? An overflow spillway with the upstream face vertical is tobe designed for a flood pea of 3### m3&s. he height of thespillway crest is ept at 8 "3#.5# m. he average river bed levelat the site is "#2.5# m. he number of spans is 6, clear waterwaybetween piers is "2 m, thicness of the pier is 2 m, piercontraction coefficient,


28/32

Sol'tio"

>ea flow, 3### m3&s. he no. of spans is 6, clear waterway between piers is "2 m, thicness of the pier is 2 m, pier contraction coefficient,


29/32

2!

23 /

CL

QH =

mH 11222

300023 .

)(./ ==

a$ Cetermine the design head

b$ design head is determined by taing the effect of endcontraction of piers and spans

dape HKKNLL )*( += 2;6


30/32

c$ Cetermine the tangent point of + ordinate of the downstream profilefrom the origin of the crest.. yHK

n

e

n

X )(1

=

)(1

=n

e

n

HK

Xy

%or verticalupstream


31/32

).( .

.

8*0

8*1

11(2

Xy=

7ifferentiate both $i+e$ with re$pect to 8

8*1

8*0

8*1

8*0

8*1

0,)011(211(2

.

.

.

.

.

.).().(

XXX

y ===

8*0

18*1

8*1

1()0

101()0

0,)0

.

.

.

.

).(.

.

Xdxdy

Xdx

dy

Xy

=

=

=

Since $lope of the +/$ face of the o%erflow $ection i$ -.: 1 So...

80

1

.=

dxdy

8*01()0

80

1 ...

X=mx

x

1(10

1()080

1 8*01

.

.*.

.

=

=


32/32

%"d

Documents

-Spillways types.pptx