Catchment Area = 15.50 Sq.Km.

= 5.99 Sq.Miles

Bed level of nalla / river = 66.60 mtr.

Observed H.F.L = 70.60 mtr.

Bank level of nalla / river = 71.50 mtr.

Head Over Crest (Hd) = 4.00 mtr.

Discharge Coefficient = 2.333

Dicken's constant = 1400

Design Discharge = Q =C.A.0.75

= 5358.31 Cusecs

 Assuming the Section of river / nalla Bank s lope = 1 :1

Slope of River / nalla = 0.5 /1000

Maximum Design Discharge = 152.00 Cumecs

Depth of flow (D) = 4.00 mtr.

Rugosity coefficient =n = = 0.0300

 Assuming Base width = 28.00 mtr.

Cross section of nalla A =(B+nD)D = = 128.00 Sq.mt.

Wetted perimetre = P = = 39.31  mtr.

Hydrulic mean depth =R = A/P = = 3.26  mtr.

V = (1/n) R2/3

  S1/2

= = 1.637  m/sec

Maximum Design Discharge = 210.00 Cumecs

O.K

4.00

28.00

Bed width of Nalla / river = 26.50 mtr.

Hence adopt the length of structure. = 28.00 mtr.

(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.

Clear waterway, Lc = 11 x 2 = 22.00 m.

Head over crest He = 1.000 m.

 Q = Cb x Le x He /  

= 34.07 cumecs.

Effective waterway, Le = 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 = 5.75 Cumecs/mt

Scour depth (R) = 1.35(q²/f)^0.333 ( f = silt factor= 1.00 )

R = 4.33 Mt.

In Down Stream

Max scour = 1.50 R = 6.490

Bottom R.L of scour = D/S H.F.L. -D/S max. scour depth = = 64.11 mtr.

Depth of D/S cut off =Bed level - bottom R.L of scour = 2.49 mtr.

D/S cut off depth = = 2.50 mtr.

Bottom R.L of cut off = = 64.10 mtr.

In Up Stream

Max scour = 1.25 R = 5.41

Bottom R.L of scour = U/SH.F.L. -U/S max. scour depth = 65.20 mtr.

Depth of U/S Bed level - Bottom RL Of U/S Scour = 1.40 mtr.

Depth of U/S cut off = 1.5 mtr.

Bottom R.L of cut off = 65.10  mtr.

Check For Exit Gradient

Water storage level = 67.60 mtr.

HYDRAULIC DESIGN OF CHECK DAM

 

Max .Static Head( H )= POND LEVEL-D/S BED LEVEL = 1.00 mtr.

α = b/d

b = Creep Length = 3.50 mtr.

  d = Depth of D/S Cut off = 2.50 mtr.

hence α = 1.40

λ = 0.5x{1+(1+α²).

} = 1.360 mtr.

GE = (H/d)*(1/πλ.) = 0.11 SAFE

CALCULATION OF UPLIFT PRESSURE AND FLOOR THICKNESS

(I)For Up stream

Hence depth ofU/S cutoff = d = 1.50  - 

α =b/d = 2.33  - 

λ = 0.5x{1+(1+α²).

} = 1.77

ΦE={COS- ( (λ-2) / λ) } /π = 31.03

ΦD={COS-

( (λ-1) / λ) } /π = 20.44

ΦD1 = 100 - ΦD = 79.56

ΦΕ1 = 100 − ΦE = 68.97

 Assuming thickness of concrete t = 0.50 mtr.

Correction toΦE=t/d (ΦD1-ΦE1) = 3.53

Corrected ΦE = 72.50

(II)For Down stream

Hence depth ofU/S cutoff = d = 2.50 Mt.

α =b/d = 1.40

λ = {1+(1+α²) . }/2 = 1.36

FE={COS-

( (λ-2) / λ) } /π = 37.58

FD={COS-

( (λ-1) / λ) } /π = 23.76

 Assuming thickness of concrete t = 0.50 Mt.

Correction to ΦE=t/d (ΦE1-ΦD1) = 2.76

Corrected ΦE = 34.81

Pressure distribution

67.70

66.60 66.60

66.45

66.10

65.10 

0.5 64.10

 A 0.5 B

0.5 1.7 1.30

(Co ns id er in g 100% Pr es su re)

72.50 53.66

34.81

 A

B

Pressure at A = 53.66

Floor thickness Submerged density of concrete = 1.24 t/m

Thickness at beginning of D/s floor = (Static head/Submerged density of concrete)*% pressure at that point

Thickness at A = 0.43  mt. Provide 0.50 mt.

Thickness at end of D/s floor = (Static head/Submerged density of concrete)*% pressure at that point

Thickness at B = 0.28  mt. Provide 0.50 mt.