Embed Size (px)
Citation preview
NAME OF PROJECT :
DESIGN DATA :
1 Full supply discharge of distributory 0.116 Cumec
2 Full supply level of distributory 269.800 m
3 Bed level of distributory 269.460 m
4 Bed width of distributory 0.300 m
5 Average bed level of parent channel 270.440 m
6 F.S.L. of parent channel 271.300 m
7 Safe exit gradient for canal bed material 0.200
8 Lacey's silt factor 0.700
9 270.230
(1) FIXATION OF CREST LEVEL AND WATERWAY :
Generally the crest level of the distributory head regulator is kept .3 M higher than Bed level of Distributory.
Adopt crest level of the regulator = 270.440 + 0.300
= 270.740
Waterway shall be worked out with the following formula
Q = C.BeHe3/2
Where,
hd = 271.300 - 269.800 = 1.500 m
He = 271.300 - 270.740 = 0.560 m
hd
He
From fig. 6.5,Varshney vol-II, The ratio of modified coefficient to free discharge works out to
Cs
C
Thus the coefficient of discharge = 1.820 X 0.993
= 1.807
(The value of 1.82 is for sharp crest free fall)
Substituting the values,
Be = 0.154 m
Thus clear waterway required = 0.154 m
Provide 1 bays of 0.154 m giving a clear water way of 0.154 m
Hence O.K.
(2) LEVEL AND LENGTH OF DOWNSTREAM FLOOR
The discharge and length of waterway is given by,
Q= 0.116 Cumec, l = 0.154 m
0.116
Discharge intensity q = --------- = 0.757 cumec/m
0.154
Head loss = u.s. F.S.L. - d.s. F.S.L.
= 271.300 - 269.800
= 1.500 m
0.993
= 0.800
Average N.S.L.
pkn
=
for, q = 0.757 cumec/m and HL = 1.500 m
D/s specific energy Ef2 (from Blench curves) = 1.003 m
Cistern floor level required = D/s F.S.L. - Ef2
= 269.800 - 1.003
= 268.797 m
U/s specific energy , Ef1 = Ef2 + HL
= 1.003 + 1.500
= 2.503 m
from energy of flow curves
Prejump Depth D1 corresponding to Ef1 = 0.111 m
Postjump Depth D2 corresponding to Ef2 = 0.972 m
Length of cistern floor required = 5 (D2 - D1)
4.306 m
The downstream floor may be provided at R.L. 268.797 with a horizontal length
of 5.000 m. (from energy consideration)
(4) Depth of sheet piles from scour considerations :
U/S sheet pile :
As per IS 6531 : 1994, on the upstream side of the head regulator, cut-off should be provided
to the same depth as the cut-off stream of diversion work, if it exists or may be calculated as
below :-
Discharge intensity 'q' = 0.757 cumec/m
Depth of scour 'R' = 1.35{q2/f}
1/3 = 1.263 m
Anticipated scour = 1.25 R = 1.579 m
R.L. of the bottom of scour hole = 271.300 - 1.579
= 269.721 m
269.230
Bottom R.L. of cut off =
= 269.230
D/S sheet pile :
Discharge intensity 'q' = 0.757 cumec/m
Depth of scour 'R' = 1.35{q2/f}
1/3 = 1.263 m
Anticipated scour = 1.5 R = 1.895 m
R.L. of the bottom of scour hole = 269.800 - 1.895
= 267.905 m
yd
2.000
(where yd is water depth im m at d/s ) = 0.670 m
R.L. of the bottom of scour hole = 268.790 m
(by minimum depth consideration) (Min. 1 m below cistern bed) = 267.797 m
Provide sheet pile line down to elevation = 267.797
(5) Total floor length and exit gradient
The floor shall be subjected to the maximum static head when full supply is being maintained in the
upstream for running the parent channel and there is no flow through the distributary head.
Maximum static head = 271.300 - 268.797
= 2.503 m
Depth of d.s. cut off = 269.460 - 267.797
= 1.663 m
Since, H 1
GE = ---- ---------
d
Hence,
1 GE.d
------------- = -------------- = 0.133
Minimum depth of d/s cutoff below bed level =
Provide U/S cut off depth = 1m minimum
+ 0.500
From Khosla's exit gradient curve a = 10.428
Hence requirement of total floor length b = a.d
= 17.343 m
Adopt total floor length = 18.000 m
Therefore,
length of d/s floor = 2/3 X total impervious length
= 12.000 m
The floor length shall be provided as below:-
Downstream horizontal floor = 12.000 m
D/s glacis length with ( 2.000 :1 slope) = 3.886 m
Crest width = 0.373 m
U/s glacis length with ( 1.000 :1 slope) = 0.300 m
Upstream floor = 3.000 m
Total = 19.560 m
(6) Pressure calculations
Let the floor thickness in the u/s be 0.300 m and near the downstream cutoff
be 0.550 m.
(i) Upstream sheet pile
Let the thickness of sheet pile = 0.500 m
d = 269.460 - 269.230
= 0.230 m
b = 19.560 m
1 d 0.230 ----- = ------ = -------- = 0.012
a b 19.560
From Khosla's Pressure curves
= 43.024
fD= 0.931
fC= 0.903 ; fD-fC = 0.029
Correction for Depth = 0.037 (+ ve)
b' = 18.560
fCcorrected = 0.903 + 0.037
= 0.940
(ii) Downstream sheet pile
d = 269.460 - 267.797
= 1.663 m
b = 19.560 m
1 d 1.663
------ = ------ = --------- = 0.085
a b 19.560
From Khosla's Pressure curves
= 6.401
fE1= 0.259
fD1= 0.180 ; fE1-fD1 = 0.078
Correction for Depth = 0.026 (- ve)
b' = 18.560
fE1corrected = 0.259 - 0.026
= 0.233
Toe of Glacis Pressure =
0.667
(7) Floor thicknessMinimum Thickness of U/S Floor = 0.300
Thickness under the crest = 0.600 m
Thickness under the toe of Glacis = 1.346 m Provide thickness for a distance 3.000 from toe of Glacies 1.35 m
Provided 1.35 m
% Pressure = 0.558
1.127 m
Provide the thickness for a distance 6.000 from toe of Glacies 1.13 m
Provided 1.15 m
% Pressure = 0.450
0.908 m
Provide the thickness for a distance 9.000 from toe of Glacies 0.91 m
Provided 0.95 m
% Pressure = 0.341
0.689
Provide the thickness for a distance 12.000 from toe of Glacies 0.69 m
Provided 0.55
NOT FOR EXECUTION 1 All dimensions in m
2 The drawing is not to the scale
3 The barrels detail is as below
271.30 No. of barrels = 1 No.
Width of each barrel = 0.154 m
D/S F.S.L. 269.80 Clear waterway = 0.154 m
CREST 270.74 M
1 2 :1 d/s glacis
:1 u/s Cistern Level 268.80
0.30 m 0.55
1.35 1.15 0.95
267.80
3.00 0.30 0.37 3.89 3.00 3.00 3.00 3.00
19.6 m
1 Full supply discharge of distributory 0.116 Cumec
2 Full supply level of distributory 269.800 m
3 Bed level of distributory 269.460 m
4 Bed width of distributory 0.300 m
5 Average bed level of parent channel 270.440 m
6 F.S.L. of parent channel 271.300 m
7 Safe exit gradient for canal bed material 0.200
8 Lacey's silt factor 0.700
Data supplied by S.E. Irrigation Circle Sriganganagar vide No.RWSRP/4089/15.10.04
Assumed data are very important for design, if it differs from above,than the design will be reviewed.Submit copy of Test results.
ACCEPTED
A.En Ex.En Director Canal Chief Engineer (North) Chief Engineer
Gates Gates Dn ID&R Irrg Unit Hanumangarh. ID&R Irrg Unit
Jaipur Jaipur
269.23
pkn
U/S F.S.L.
270.44U/S Bed Level
DETERMINATION OF CONJUGATE DEPTH(Refer IS 4997-1968)
HL/DC = 0.231 0.235 0.240 0.244 0.249 0.254 0.259 0.264
D1/DC = 0.6 0.598 0.596 0.594 0.592 0.59 0.588 0.586
HL = 1.50
q = 0.76DC = 0.39
HL/DC = 3.87
D1/DC = 0.29
D1 = 0.11
D2 = 0.97
Ef1 = 2.48
Ef2 = 1.00
0.2
0.3
0.4
0.5
0.6
0.7
D1/D
C
Sequent depth determination
