Bed level of nalla / river Observed H.F.L Bank level of nalla / river Head Over Crest (Hd) Discharge Coefficient Dicken's constant 0.75
Design Discharge = Q =C.A. = Assuming the Section of river / nalla Bank s lope Slope of River / nalla Maximum Design Discharge Depth of flow (D) Rugosity coefficient =n = Assuming Base width Cross section of nalla A =(B+nD)D = Wetted perimetre = P = Hydrulic mean depth =R = A/P = 2/3
28.00 Bed width of Nalla / river = Hen c e ad o p t t h e l en g t h o f s t r u c t u r e. = (Note:- Length of structure should not be less than actual bed width of nallah or river.) Number of spans = 11 Clear span = 2.000 m Width of pier = 0.600 m Hence water way, L = 28 m. m. Clear waterway, Lc =
11 x 2 = 22.00
Head over crest He = 1.000 Q = Cb x Le x He
/
26.50 mtr. 28.00 m t r .
=
m.
m. 34.07 34.07 cumecs cumecs..
Effective waterway, L e = L - 2*(N*Kp + Ke )*He - W =
19.980
Where N = No of piers =
10
Kp = Pier contraction co-efficient. =
0.1 (For round nosed piers)
Ka = Abutment contraction Co-efficient=
0.01 (For splayed wing walls to abutment)
W = Total width of all piers = N*w =
6 m Cb =
1.705
4.00
28.00 Cut off q = Discharge intensity = Q/Le = Scour depth (R ( R) = 1.35(q²/f)^0.333 ( f = silt factor= R In Down Stream Max scour = 1.50 R Bottom R.L of scour = D/S H.F.L. -D/S max. scour depth = Depth of D/S cut off =Bed level - bottom R.L of scour D/S cut off depth = Bottom R.L of cut off = In Up Stream Max scour = 1.25 R B ot ot to to m R .L .L o f s co co ur ur = U /S /SH .F .F. L. L. - U/ U/ S m ax ax . s co co ur ur d ep ep th th Depth of U/S Bed level - Bottom RL Of U/S Scour Depth of U/S cut off Bottom R.L of cut off Check For Exit Exit Gradient Water storage level
5.75 Cu Cumecs/mt 1.00 =
) 4.33 Mt. = = = = =
6.490 64.11 mt m t r. 2.49 mtr. 2.50 mtr. 64.10 mtr.
GE = CAL CULATION OF UPLIFT PRESSURE AND FLOOR THICK NESS (I)For Up stream Hence depth ofU/S cutoff = d α =b/d . λ = 0.5x{1+(1+α²) } ΦE={COS ( (λ-2) / λ ) } / π ΦD={COS ( (λ-1) / λ) } /π ΦD1
= 100 - ΦD
-
(II)For Down stream
Assuming thickness of concrete Correction to ΦE=t/d (ΦE1-ΦD1) Corrected ΦE Pressure distribution 67.70
66.60
66.60 66.45 66.10
65.10 0.5
64.10 A
0.5
0.5 B
1.7
1.30 (Co ns id er in g
72.50
100%
Pr es su re)
53.66 34.81 A B
Pressure at A = Floor thickness Submerged density of concrete = Thickness at beginning of D/s floor = (Static head/Submerged density of concrete)*% pressure at that point Thickness at A = 0.43 mt. Thickness at end of D/s floor = (Static head/Submerged density of concrete)*% pressure at that point Thickness at B = 0.28 mt.
