| Design of Trench
Weir |
| Design
Discharge |
Q40 |
1.47 |
|
|
| Design Flood
Discharge |
Q100 |
120.00 |
|
|
| Length of
river |
L |
20.00 |
m |
|
| River bed
level |
Z |
1020.00 |
amsl |
|
| Ratio of area of opening to total area of trashrack surface over
trench |
E1 |
0.50 |
|
|
| Ratio of opening in the trashrack likely to be clogged |
E2 |
0.40 |
|
|
| Coefficient of discharge through broad crested weir |
C |
1.53 |
|
|
| Coefficient of discharge through opening |
Cd |
0.46 |
|
|
| |
|
|
|
|
| Assumed length for trench |
L' |
10.00 |
|
|
| Discharge to pass through weir |
Q |
2.21 |
m3/s |
2.2 |
| Specific Energy at any section of the stream |
E |
0.17 |
|
|
| Width Required to pass design discharge |
W |
0.65 |
|
0.65 |
| |
|
|
|
|
| Width by Considering velocity |
|
|
|
|
| Velocity |
v |
0.75 |
m/s |
|
| Width |
W |
0.15 |
m |
0.15 |
| Width required for 50% clogging |
W |
0.30 |
m |
|
| Minimum width Required |
Wmin |
1.25 |
m |
|
| |
|
|
|
|
| Final width of weir at top |
W |
1.25 |
m |
|
| Final Length of trench |
L |
10.39 |
m |
10 |
| |
|
|
|
|
| constant depending on bottom profile of channel |
η |
0.50 |
|
|
| |
|
|
|
|
| Depth required |
d |
1.00 |
m |
|
| Area |
A |
1.25 |
m2 |
|
| Velocity head at the end of trench |
H |
0.17 |
m3/s |
|
| Discharge |
Q |
2.26 |
m3/s |
|
| |
|
|
|
|
| Final Depth |
d |
1.00 |
m |
|
| |
|
|
|
|
| Slope of
trench |
|
0.06 |
|
|
| Depth at
end |
|
1.625 |
|
1.63 |
| Depth at Start
(from Intake Criteria) |
|
1.00 |
|
|
| Trench bottom
slope level at start |
|
1019.00 |
amsl |
|
| Trench bottom
slope level at end |
|
1018.37 |
amsl |
|
| |
|
|
|
|
| Check for
adequency of waterway |
|
|
|
|
| Average depth |
|
1.31 |
|
|
| Area |
|
1.64 |
|
|
| Wetted
Peimeter |
|
3.25 |
|
|
| Slope Provided |
S |
0.06 |
|
|
| Mannings
Coefficient |
|
0.0018 |
|
|
| Discharge |
Q |
25.22 |
m3/s |
|
| |
|
|
|
|
| Check for
adequency of capacity with 50% area clogged |
|
|
|
|
| Average depth |
|
0.66 |
|
|
| Area |
|
0.82 |
|
|
| Wetted
Peimeter |
|
2.56 |
|
|
| Slope Provided |
S |
0.06 |
|
|
| Mannings
Coefficient |
|
0.00 |
|
|
| Discharge |
Q |
13.16 |
|
|
| Slope of
trashrack |
|
0.10 |
|
|
| Width of
trashrack |
|
1.30 |
|
|
| |
|
|
|
|
| Design flood
discharge (Qflood) |
|
120 |
m3/s |
|
| Discharge
Passing through the Spilling portion |
|
0 |
m3/s |
|
| Provide height
of the weir above river bed level
= |
|
0 |
m |
|
| Qweir(flood) |
= |
Cw * L weir * H overtop 3/2 |
|
| coefficient of
discharge |
|
2.2 |
assumed |
|
| Weir Crest
width L weir = |
|
17 |
|
|
| Head over crest = |
|
2.18 |
m |
|
| |
|
|
|
|
| River Bed
level at Weir axis = |
|
1020.00 |
m |
|
| Crest level of
weir = |
|
1020.00 |
m |
|
| High Flood
Level = |
|
1022.18 |
m |
|
| |
|
|
|
|
| Scour Depth
Calculation |
|
| Design
Flood |
Q25 |
84.0 |
m3/s |
| Width of
Stilling Basin @ Q25 |
B |
17.0 |
m |
| Specific
Discharge |
q |
4.94 |
m3/s |
| Average
Particle size |
D |
7.28 |
mm |
| Silt Factor |
f=1.76*D50^0.5 |
4.7 |
|
| Lacy's Scour
Depth |
R=1.35 *(q^2/f)^(1/3) |
2.3 |
m |
| Adopted U/S
Scour Depth= Cutoff wall |
1.25R |
2.91 |
m |
| Adopted D/S
Scour Depth= Cutoff wall |
1.5R |
3.5 |
m |
| |
|
|
|
|
| Design flood
discharge (Qflood) |
|
|
85.0 |
m3/s |
| Discharge
Passing through the Spilling portion |
|
|
0 |
m3/s |
| Provide height
of the weir above river bed level
= |
|
|
0 |
m |
| Qweir(flood) |
= |
Cw * L weir * H overtop 3/2 |
| coefficient of
discharge |
|
|
2.2 |
assumed |
| Weir Crest
width L weir = |
|
|
17 |
|
| Head over
crest = |
|
|
1.73 |
m |
| High Flood
Level |
|
|
1021.73 |
|
| Bottom of cut
off U/S |
|
|
1018.82 |
|
| Height of
Cutoff U/S |
|
|
1.18 |
1.16 |
| Bottom of cut
off D/S |
|
|
1018.23 |
|
| Height of
Cutoff D/S |
|
|
1.79143 |
1.75 |
