Question

Design an ogee spillway with the following data: (i) Height of spillway crest above river bed 100 m (ii) Design discharge 12,000 cumecs (iii) Number of spans 6 (iv) Clear distance between piers 15 m (v) Thickness of pier 3 m Slope of d/s face of the overflow section 0.8:1 Assume any other data if required.

Answer 1

Answer Design of Ogee Spillway: Given data: 1) Height of spillway crest 100m 2) Design discharge 12,000 cumecs 3) Number of spans-6 4) Clearwidth of 15m 5) Thickness of each pier 3m 6) Slope of d/sface of the overflow section 0.8:1

Solution- Computation of design head Assuming coefficient C, 2.2 Le = L= clear water width Va where, Ha = ag Thus, Le = L = 6 * 15 90 12000 2.2 (6 15) H H2 = 60.60 He = 15.50

Given, h 100m h 100 H 15.50 6.45 2 1.33 Velocity approach can be neglected, h +H 100+15.5 H, =. 15.5 7.45 1.7 Thus effect on discharge coeficient is neglected. Le 90-214 0.01+0.15.5 85.66

12000 = 2.2 * (85.66) * H. H2 = 63.67 H 15.9!5 x1.85 = 2 * H2.85 * y y21.05 dy 1 dx 0.8 dy 1.85x05 dx 21.05 dy ax = 0.08788xo.85 Comparing both dy/dx we getx-23.77 and y 16.68 1.85 21.05

0.047505938 0.171258995 0.362595342 4 0.617388995 0.932915713 1.30715688 1.738518329 05 2.225688469 2.767556796 10 3.363162871 4.011662302 12 4.712302971 13 5.464407788 14 6.267361794 18 9.977047371 14.46205002 23.77 16.68790758