Weir Design

MODEL CALCULATION FOR DESIGN OF H.C. WEIR

The Discharge per Meter length of weir 3/2

Q= Cd x L x h Q= 1.933

Q= Cd= Cd= L= h= H=

discharge per meter 2.26 2.264 4 proposed by poondy research station 1 Length of weir in meter 0.9 Head of Flow in meter 1.4 Height of Body wall

SCOUR DEPTH CALCULATIONS 2

1/3

1.35(Q /F) R= 1.663

Nominal Scour Depth= R=

metres Q= discharge per meter f= 2 Laceys silt factor

Down Stream cut off is taken up to 2R depth =2xR= Depth Below apron level=2R-d2= Provide:

3.325 m

below MFL

1.961

2.20 m which is safe

Top width of Body wall is taken as 0.45m as 0.45m for all heads of flow and height of body wall

STABILITY CALCULATIONS: Where there is water up to crest level on up stream side and no water on down stream side FIG side FIG I

CASE I:

L5=

FTL W7

0.22

W5 W4 c= 2.25

Specific gr gravity of co concrete

W6 L4=

1.18 W1

A

W2

W3

0.45

0.45

0.7

L1

L2

L3

Figure I

S.No. 1 2 3 4 5 6

TAKING MOMENTS ABOUT (A (A) Force Details W1 1/2xL1xL3x2.25 W2 L2xL3x2.25 W3 1/2xL3x(L3+L4)x2.25 W4 1/2xL2xL5x2.25 W5 1/2xL2xL5x1 W6 1/2xL1xL4x1

Magnitude L.A. 0.5974 0.3000 1.1948 0.6750 1.1025 1.1333 0.1114 0.7500 0.0495 0.6000 0.2655 0.1500

Moment 0.1792 0.8065 1.2495 0.0835 0.0297 0.0398

7 8

W7 3

WH /6 = TOTAL

L1xL5x1 3 1x1.4 /6 =

0.0990

0.2250

3.4200 Position of Resultant= E M/ EW=

The resultant falls within middle third of

0.533333

and

W8

W9

0.0223 0.4573 2.8678

0.838548 1.066667 Hence safe.

MWL

h= 0.9

L1=

0.22

FTL W7

W5

TWL W4

W6 L2=

1.18 W1

L3

W2

0.45

Figure II

W3

L5

DESIGN OF F.O.F WEIR Name of Work:

The Discharge per Meter length of weir 3/2

Q= Cd x L x h Q= 0.837

Q= Cd= L= h= H=

discharge per meter 1.8 proposed by poondy research station 1 Length of weir in meter 0.6 Head of Flow in meter 2.5 Height of Body wall


1.35(Q /F) R= 0.951


1/3



1.903 m

below MFL

0.539


Top width of Body wall is taken as 0.45m for all heads of flow and height of body wall

CASE I:

STABILITY CALCULATIONS: Where there is water up to crest level on up stream side and no water on down stream side FIG I FTL

c= 2.25 L3=

Specific gravity of concrete

2.5 W1

A

W2

0.45

1.55

L1

L2 2

Figure I

S.No.

Force 1 W1

TAKING MOMENTS ABOUT (A) Details L1xL3x2.25

Magnitude L.A. Moment 2.5313 #VALUE! #VALUE!

2 3 4 5 6 7 8

W2 W3 W4 W5 W6 W7

1/2xL2xL3x2.25 1/2xL3x(L4+L5)x2.25 1/2xL2xL5x2.25 1/2xL2xL5x1 1/2xL1xL4x1 L1xL5x1 3 WH /6 = TOTAL

4.3594 4.3594 0.0000 0.0000 #VALUE! #VALUE!

Position of Resultant= E M/ EW= Middle third is between #VALUE!

#VALUE!

#VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE!

#VALUE! #VALUE! #VALUE! #VALUE! #VALUE! #VALUE! 2.6042 #VALUE!

#VALUE!

and

#VALUE!

W5

W4

MWL

h= 0.6 FTL

W3

L3=

2.5 W1

A

H=L1+L2

S.No. 1 2 3 4 5 6 7 8 9 10

0.45 L1

W2

1.55 L2

Figure II TAKING MOMENTS ABOUT (A) Force Details W1 L4xL1x1.25 W2 1/2xL1xL5x1.25 W3 1/2xL1xL5x1 W4 hxL5x1 W5 1/2xL1xL4x1 W6 1/2xL2xL3x1 W7 L1xL3x1 W8 hxL3x1 W9 hxL4x1 W10 1/2xL5x(L1+L2)x1 3

2

Magnitude L.A. 1.4063 0.2250 2.4219 0.2250 1.9375 0.9667 0.9300 0.3000 0.0000 0.1500 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.2700 0.2250 1.9375 1.4833

3

MD=(H +3xdxH -D )/6

2.8125 8.7605

8.9031 Position of the Resultant( EM/EW)=

Moment 0.3164 0.5449 1.8729 0.2790 0.0000 0.0000 0.0000 0.0000 0.0608 2.8740

0.9840

The resultant falls within middle third of

0.666667 and

1.333333333

The resultant falls between middle Third, Hence safe

FIXING OF LENGTH OF SOLID APRON BASED ON HYDRAULIC JUMP THEORY:

d2

H d1

Ld

L j Lb=Ld+Lj

2

3

The Drop Number=Dn= q /(gH )=

0.005

The Length of the Apron before Jump,Ld=Hx4.3x(Dn) 0.425 The Jump depths are d1=Hx0.54xDn 0.27 d2=Hx1.66x(Dn)

0.27

2.509 0.137 0.969

The Length of the Apron after the Jump,Lj = 5x(d2-d1)

4.159

The Total Length of the Apron= Lb = Ld+Lj =

say

6.668 m

7.000 m

Rough Stone Apron Scour Depth, D= 0.80 m Length to be covered on a slope of 2:1= Sqrt(5)xD

1.789

Thickness of Settled stones after Scour=1.24xT (Assuming side slope thickness as T Quantity/m Run= 1.014 Length of Launching Apron=1.5D= Thickness=

0.567 1.5 feets i.e

1.200 metres

0.845 m or say

0.900 m

0.4572 metres)

TWL

STABILITY CALCULATIONS:

CASE I:

L5=

Where there is water up to crest level on up stream side and no water on down stream side FIG I FTL W7

0.22

W5 W4 c= 2.25


W6 L4=

2.28 W1

A

0.65 L1

W2

W3

0.9

1.25

L2

L3

2.8

Figure I

S.No. 1 2 3 4 5 6 7 8

TAKING MOMENTS ABOUT (A) Force Details W1 1/2xL1xL3x2.25 W2 L2xL3x2.25 W3 1/2xL3x(L4+L5)x2.25 W4 1/2xL2xL5x2.25 W5 1/2xL2xL5x1 W6 1/2xL1xL4x1 W7 L1xL5x1 3 WH /6 = TOTAL

Magnitude L.A. 1.6673 0.4333 4.6170 1.1000 3.5156 1.9667 0.2228 1.2500 0.0990 0.9500 0.7410 0.2167 0.1430 0.3250 11.0056

Position of Resultant= E M/ EW= Middle third is between 0.933333 and The resultant falls between middle Third, Hence safe

1.444617 1.866667

Moment 0.7225 5.0787 6.9141 0.2784 0.0941 0.1606 0.0465 2.6042 15.8989

MWL

h= 1.5

L1=

W8 FTL W7

0.22

W9

W5

TWL W4

W10

W6 L2=

2.28

1.6 W1

A

0.65 L3

H=L1+L2

S.No. 1 2 3 4 5 6 7 8 9 10

W2

0.9 L4

W3

1.25 L5

Figure II

TAKING MOMENTS ABOUT (A) Force Details W1 1/2xL2xL3x1.25 W2 L2xL4x1.25 W3 1/2xL2xL5x1.25 W4 1/2xL1xL4x1.25 W5 1/2xL1xL4x1 W6 1/2xL2xL3x1 W7 L1xL3x1 W8 hxL3x1 W9 hxL4x1 W10 1/2xL5x(L1+L2)x1 3

2

Magnitude L.A. 0.9263 0.4333 2.5650 1.1000 1.9531 1.9667 0.1238 1.2500 0.0990 0.9500 0.7410 0.2167 0.1430 0.3250 0.9750 0.3250 1.3500 1.1000 1.5625 2.3833

3

MD=(H +3xdxH -D )/6

5.6715 18.7171

10.4386 Position of the Resultant( EM/EW)= The resultant falls within middle third of

1.7931

0.933333 and


Moment 0.4014 2.8215 3.8411 0.1547 0.0941 0.1606 0.0465 0.3169 1.4850 3.7240

1.866667

DESIGN OF H.C. WEIR Name of Work: Constructing checkdam across Bhyrampalli vagu, Bhyrampally(v), Maganoor(M), Mahaboobnagar District The Discharge per Meter length of weir 3/2

Q= Cd x L x h Q= 2.976

Q= Cd= L= h= H=

discharge per meter 2.264 proposed by poondy research station 1 Length of weir in meter 1.2 Head of Flow in meter 2.7 Height of Body wall


1/3

1.35(Q /F) R= 2.217




4.434 m

below MFL

3.070


Top width of Body wall is taken as 0.45m for all heads of flow and height of body wall

STABILITY CALCULATIONS: Where there is water up to crest level on up stream side and no water on down stream side FIG I

CASE I:

L5=

FTL W7

0.22

W5 W4 c= 2.25

W6 L4=

2.48 W1

A

W2

W3

0.85

0.9

1.35

L1

L2

L3

3.1

Figure I


S.No. 1 2 3 4 5 6 7 8

TAKING MOMENTS ABOUT (A) Force Details W1 1/2xL1xL3x2.25 W2 L2xL3x2.25 W3 1/2xL3x(L4+L5)x2.25 W4 1/2xL2xL5x2.25 W5 1/2xL2xL5x1 W6 1/2xL1xL4x1 W7 L1xL5x1 3 WH /6 = TOTAL

Magnitude L.A. 2.3715 0.5667 5.0220 1.3000 4.1006 2.2000 0.2228 1.4500 0.0990 1.1500 1.0540 0.2833 0.1870 0.4250 13.0569

Position of Resultant= E M/ EW= Middle third is between 1.033333 and The resultant falls between middle Third, Hence safe

Moment 1.3439 6.5286 9.0214 0.3230 0.1139 0.2986 0.0795 3.2805 20.9893

1.607526 2.066667

MWL

h= 1.2

L1=

W8

W9

FTL W7

0.22

W5

TWL W4

W10

W6 L2=

2.48

1.6 W1

A

0.85 L3

H=L1+L2

S.No. 1 2 3 4 5 6 7 8 9 10

W2

0.9 L4

W3

1.35 L5

Figure II TAKING MOMENTS ABOUT (A) Force Details W1 1/2xL2xL3x1.25 W2 L2xL4x1.25 W3 1/2xL2xL5x1.25 W4 1/2xL1xL4x1.25 W5 1/2xL1xL4x1 W6 1/2xL2xL3x1 W7 L1xL3x1 W8 hxL3x1 W9 hxL4x1 W10 1/2xL5x(L1+L2)x1 3

2

Magnitude L.A. 1.3175 0.5667 2.7900 1.3000 2.2781 2.2000 0.1238 1.4500 0.0990 1.1500 1.0540 0.2833 0.1870 0.4250 1.0200 0.4250 1.0800 1.3000 1.8225 2.6500

3

MD=(H +3xdxH -D )/6

6.9718 23.6958

11.7719 Position of the Resultant( EM/EW)= The resultant falls within middle third of

Moment 0.7466 3.6270 5.0119 0.1794 0.1139 0.2986 0.0795 0.4335 1.4040 4.8296

2.0129 1.033333 and


2.066666667

FIXING OF LENGTH OF SOLID APRON BASED ON HYDRAULIC JUMP THEORY:

d2

H d1

Ld

L j Lb=Ld+Lj

2

3

The Drop Number=Dn= q /(gH )=

0.046 0.27

The Length of the Apron before Jump,Ld=Hx4.3x(Dn) 0.425 The Jump depths are d1=Hx0.54xDn 0.27 d2=Hx1.66x(Dn)

0.393 1.950

The Length of the Apron after the Jump,Lj = 5x(d2-d1)

7.784

The Total Length of the Apron= Lb = Ld+Lj =

say

12.836 m

5.052

13.000 m

Rough Stone Apron Scour Depth, D= 3.30 m Length to be covered on a slope of 2:1= Sqrt(5)xD

7.379

Thickness of Settled stones after Scour=1.24xT (Assuming side slope thickness as T Quantity/m Run= 4.183 Length of Launching Apron=1.5D= Thickness=

0.567 1.5 feets i.e

4.950 metres

0.845 m or say

0.900 m

0.4572 metres)

Weir Design

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