Free Board Calculation of Dams

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this calculation is used only in reservoir type scheme only. don't consider specific mythology for R-O-R schemes. Assume 2 or 1.5 m free board for these schemes.

Transcript of Free Board Calculation of Dams

Master CopyReference- IS6512-1984, Appendix A Full Reservoir Level FRL = 146.3 m Reservoir Maximum Fetch Fmax = 11 km Reservoir Effective Fetch Fe = 5.1 km Maximum wind Velocity over Land UL 140 km/h Wind Ratio, (Table-A-1.5) Wr 1.27 Wind Velocity over Water, UW=Wr*UL UW 177.8 km/h Significant wave Height, (From Fig 5) Hs 2.8 m Design wave Height, (From Table A-1.7) H 3.6 m Wind Set up=V2Fmax/(62000D) HWS 0.3 m Computed Free Bard=4/3(H)+HWS FBcomp 5.1 m Similar computation should be done with reference to MWL for 2/3 wind velocity. Minimum Free board to be Provided above MWL 1m Top of Dam=max of (FRL+Fbcomp), (MWL+FBcompMWL),MWL+1) 151.4 Calculation of Effective Fetch 0 Cos x1Cos x1 in km 42 0.743 Aa 3 2.23 36 0.809 Ab 4.85 3.92 30 0.866 Ac 3.65 3.16 24 0.914 Ad 4.8 4.39 18 0.951 Ae 5.5 5.23 12 0.978 Af 5.9 5.77 6 0.995 Ag 6 5.97 0 1.000 AB 4.5 4.50 6 0.995 Ag' 4.7 4.67 12 0.978 Af' 5.3 5.18 18 0.951 Ae' 4.2 3.99 24 0.914 Ad' 5.25 4.80 30 0.866 Ac' 6.2 5.37 36 0.809 Ab' 6.55 5.30 42 0.743 Aa' 5.1 3.79 13.511 68.28 i) Effective Fetch=sum(x1Cos)/sum(Cos) 5.1 km ii) Maximum Fetch CD 11 km Computation of Fetch of Water Along Fetch Line C-D S. No. FRL in m GL in m Depth in m 1 146.3 146.3 0 2 146.3 140 6.3

93.3333 1.27 118.533 2.8 3.6 0.1 4.9

3 4 5 6 7 8

146.3 146.3 146.3 146.3 146.3 146.3

135 130 125 120 115 112

Total Average depth=Total/8

11.3 16.3 21.3 26.3 31.3 34.3 147.1 18.3875 m

Master Copy

Reference- IS6512-1984, Appendix A Full Reservoir Level FRL = 424.8 m Reservoir Maximum Fetch Fmax = 2.95 km From Drawing Reservoir Effective Fetch Fe = 0.8 km From Drawing Maximum wind Velocity over Land UL 158.4 km/h Wind Ratio, (Table-A-1.5) Wr 1.1 Wind Velocity over Water, UW=Wr*UL UW 174.24 km/h Significant wave Height, (From Fig 5) Hs 1.028 m Design wave Height, (From Table A-1.7) H 1.4 m Wind Set up=V2Fmax/(62000D) HWS 0.000 m Computed Free Bard=4/3(H)+HWS FBcomp 1.87 m Similar computation should be done with reference to MWL for 2/3 wind velocity. Minimum Free board to be Provided above MWL 1m Top of Dam=max of (FRL+Fbcomp), (MWL+FBcompMWL),MWL+1) 426.67 m Calculation of Effective Fetch 0 Cos x1Cos x1 in m 1. Computation of free board - FRL Condition 42 0.743 Aa 268.03 199.19 Depth of water (D) = 36 0.809 Ab 296.08 239.53 Step 1 FRL 30 0.866 Ac 324.9 281.37 Step 2 Reservoir maximum fetch Step 3 Reservoir effective fetch 24 0.914 Ad 354.27 323.64 Step 4 maximum wind velocity over land 18 0.951 Ae 388.24 369.24 Step 5 Wind velocity overwater=158.40X1.1 Step 6 Significant Wave height ( Hs ) 12 0.978 Af 1350.54 1321.03 Step 7 Design Wave height (H)= 1.27 X Hs 6 0.995 Ag 1646.74 1637.72 Step 8 Wind set up = V 2 F/62000D Step 9 Computed free board = 1.33 X H + wind setu 0 1.000 AB 2945.64 2945.64 Step 10 Top of the dam 6 0.995 Ag' 736.13 732.10 Prov 12 0.978 Af' 666.79 652.22 18 0.951 Ae' 628.04 597.30 24 0.914 Ad' 571.42 522.02 30 0.866 Ac' 456.37 395.23 36 0.809 Ab' 398.7 322.56 42 0.743 Aa' 119.1 88.51 13.511 10627.28 i) Effective Fetch=sum(x1Cos)/sum(Cos) 0.79 km ii) Maximum Fetch CD 2.95 km Computation of Fetch of Water Along Fetch Line C-D S. No. FRL in m GL in m Depth in m 1 424.8 294.5 130.3 2 424.8 360 64.8

390 340 295.5 296.5 390 340 330 Total Average depth=Total/9

3 4 5 6 7 8 9

424.8 424.8 424.8 424.8 424.8 424.8 424.8

34.8 84.8 129.3 128.3 34.8 84.8 94.8 786.7 87.4111 m

From Drawing From Drawing

87.41 m 424.80 m 2.95 km aximum fetch 0.79 km fective fetch 158.40 km p h ind velocity over land 174.21 km p h y overwater=158.40X1.1 1.084 m Wave height ( Hs ) 1.38 m e height (H)= 1.27 X Hs 0.0165 = V 2 F/62000D 1.86 m ee board = 1.33 X H + wind setup 426.66 m am Provided - 426 .80 m

ree board - FRL Condition er (D) =