PracticalProfileofSpillwaY
When the profile for the crest of the ogee spillway is plotted over the triangular profile the section of a gravity dam (non-overflow section) ,it is found that it goes beyond vie downstream face of the dam , thu requiring thickening of the section for the spillway .
However,this extra concrete can be saved by shifting the curve of the nappe in a backward direction until this curve becomes tangential to the downstream face of the dam .
Design of spillway
Design an ogee spillway for concrete gravity dam, for the following data :
(1) Average river bed level = 100.0 m
(2) R.L. of spillway crest =204.0 m
(3) Slope of d/s face of gravity dam = 0.7 H : 1 V
(4) Design discharge = 8000 cumecs
(5) Length of spillway = 6 spans with a clear width of 10 m each.
(6) Thickness of each pier = 2.5 m
If h/Hd is greater than 1.7 than high spillway so effect of velocity is neglected
The co-ordinates from x = 0 to x = 27.4 m are worked out in the table below :
2. Offsets and Risers on
Upstream Face :
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
2
3. PracticalProfileofSpillwaY
When the profile for the crest of the
ogee spillway is plotted over the
triangular profile the section of a
gravity dam (non-overflow section)
,it is found that it goes beyond vie
downstream face of the dam , thu
requiring thickening of the section
for the spillway .
4.
5. However,this extra concrete can be
saved by shifting the curve of the
nappe in a backward direction until
this curve becomes tangential to the
downstream face of the dam .
6.
7. Offsets and Risers on
Upstream Face
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
7
9. Design of spillway
Design an ogee spillway for
concrete gravity dam, for the
following data :
(1) Average river bed level = 100.0
m
(2) R.L. of spillway crest =204.0 m
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
9
10. (3) Slope of d/s face of gravity dam
= 0.7 H : 1 V
(4) Design discharge = 8000 cumecs
(5) Length of spillway = 6 spans
with a clear width of 10 m each.
(6) Thickness of each pier = 2.5 m
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
10
11. Step-1 : Computation of
design head
Hd = He + Ha
Where Ha = Va
2/2g
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
11
12. If h/Hd is greater than 1.7 than high
spillway so effect of velocity is
neglected
13. Its high spillway Ha = 0
13/2/14
Prepared by v.h,khokhani, assistant
professor, DIET
13
