report no. gr 82-9, hydraulic model study of choke canyon ... … · 4 title and subtitle 5 report...
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HYDRAULIC MODEL STUDY OF CHOKE CANYON DAM SPILLWAY AND STILLING BASIN
August 7982 Engineering and Research Center
S. Department of the Interior Bureau of Reclamation
Division of Research Hydraulics Branch
4 T I T L E A N D S U B T I T L E 5 R E P O R T 3 A T E
Hydraulic Model Study of Choke Canyon Dam Spillway and Stilling Basin
7 A U T H O R I S I 8 . P E R F O R M I N G O R G A N I Z A T I O N R E P O R T N O .
Robert L. George GR-82-9
9 P E R F O R M I N G O R G A N I Z A T I O N N A M E A N D A D D R E S S 1 1 0 . WORK U N I T N O .
Bureau of Reclamation Engineering and Research Center 1 1 . C O N T R A C T O R G R A N T N O .
Denver, Colorado 80225 13. T Y P E O F ' ? € P O R T A N D P E R I O D
C O V E R E D 2 S P O N S O Q I N G A G E N C Y N A M E A N D A D D R E S S
Same
1 1 4 . S P O ~ ! S O R I I I G A G E N C Y C O D E
I ' 5 . S U P P L E M E N T A R Y N O T E S
Microfiche and or hard copy available at the E&R Center, Denver, CO
16 A B S T R A C T
A 1:80 scale hydraulic model of the Choke Canyon Dam spillway and stilling basin was studied. The dam will be 35 meters high and have a crest length of 5640 meters. The spillway chute is 112.2 meters wide and has a Froude number of about 4.4 at the stilling basin entrance. The stilling basin was designed to criteria developed for low Froude number flows. A modified entrance channel was developed as the model was tested. Stilling basin walls were shortened as a result of model studies. A 14-meter apron having 32 meters of riprap extended downstream from the end sill was recommended. The design worked well for all discharges and scour was limited to an area downstream from the riprap.
17. K E Y WORDS A N D D O C U M E N T A X A L Y S I S
3 . D E S C R I P T O R S - - / *scour/ approach channelslspillway approach1 *guide walls1 slopes1 *stilling basin
5 . I D E N T I F I E R S - - Choke Canyon Dam, TX
18. D l S T R l ! 3 U T I O N 5 7 A T E M E N T 19 S E C U R I T Y C L A S S 2 1 . N O . O F P A G E ! ( T H I S R E P O R T 1
U N C L A S S I F I E D 30 23. S E C U R I T Y C L A S S 2 2 . P R I C E
( T W ; P A G E )
J
- G P O 831 - 3 1 6
GR-82-9
HYDRAULIC MODEL STUDY OFCHOKE CANYON DAM
SPILL WAY & STILLING BASIN
byRobert L. George
.81 METRIC
Hydraulics BranchDivision of Research
Engineering and Research CenterDenver, Colorado
August 1982
UNITED STATES DEPARTMENT OF THE INTERIOR * BUREAU OF RECLAMATION
ACKNOWLEDGMENTS
The hydraulic model study described in this report was
conducted in the Hydraulic Structures Section and was
reviewed by E. 1. Carlson, Head of the Hydraulic
Research Section, in the Hydraulics Branch. Engineers
involved in design of Choke Canyon Dam made valuable
suggestions during the study.
As the Nation's principal conservation agency, the Department of theInterior has responsibility for most of our nationally owned publiclands and natural resources. This includes fostering the wisest use ofour land and water resources, protecting our fish and wildlife, preser-ving the environmental and cultural values of our national parks andhistorical places, and providing for the enjoyment of life through out-door recreation. The Department assesses our energy and mineralresources and works to assure that their development is in the bestinterests of all our people. The Department also has a major respon-sibility for American Indian reservation communities and for peoplewho live in Island Territories under U.S. Administration.
CONTENTS
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Model similitude parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Model tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Preliminary tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Entrance modifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Stilling basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radial gate calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety boom. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bibliography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FIGURES
1 Location map for Choke Canyon Dam. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Sketch of low Froude number stilling basin. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Drawing of the model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Model as designed originally. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sa Scour around left inlet wall, Qp = 7080 m3/s tested for 8.94 hours. . . . . . . . . . .
5b Scour around right inlet wall, Qp = 7080 m3/s for 8.94 hours. . . . . . . .. . . . . . .
6 Scour pattern with straight dikes, Qp = 7080 m3/s tested for 8.94 hours. . . . . . .
7 Sketch of model with 30° wingwalls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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445678
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CONTENTS-Continued
Figure
8 Scour around right 30° wingwall with 100-m dike,Qp = 7080 m3/s for 8.94 hours. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9 Scour around left 30° wingwall with 100-m dike, Qp = 7080 m3/s for8.94 hours. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 Scour in vicinity of 30° wingwall with 200-m dike,Qp = 7080 m3/s for 8.94 hours. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
lla Scour with segmented right inlet wall, Qp = 7080 m3/s for 8.94 hours. . . . . . . . .
Scour with segmented left inlet wall, Qp = 7080 m3/s for 8.94 hours. . . . . . . . . .llb
12 Model discharging 0.083 m3/s(Qp = 4750 m3/s),equivalent to1000-year flood. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13a Scour from 300-mm (24 m prototype) radius inlet wall with 400-mm wall(32 m prototype) extension at 90° to left inlet wall. . . . . . . . . . . . . . . . . . . . . . .
13b Scour from 300-mm (24 m prototype) radius inlet wall with 21O-mm(16.8 m prototype) extension at 120° to right inlet wall. . . . . . . . . . . . . . . . . . .
14 Recommended design of inlet walls and approach channel. . . . . . . . . . . . . . . . .
15a Scour pattern with sidewalls shortened 5.48 m and original apron,Qp = 7080 m3/sfor 8.94 hours. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15b Scour pattern with sidewalls and apron shortened 5.48 m,Qp = 7080 m3/s for 8.94 hours. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16 Scour pattern with 2-1/2:1 side slopes around sidewalls and basinshortened 5.48 m, Qp = 7080 m3/s for 8.94 hours. . . . . . . . . . . . . . . . . . . . . . .
17 Long-term scour test, Qp = 7080 m3/s for 53.7 hours. . . . . . . . . . . . . . . . . . . . . .
18 Scour after 8.94 hours at Qp = 7080 m3/s with 14-m apron. . . . . . . . . . . . . . . . .
19 Scour after 8.94 hours with 14-m apron and 32 m of riprapdownstream, Qp = 7080 m3/s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv
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CONTENTS-Continued
Figure
20 Scour after 33.5 hours, 14-m apron and 32-m of rip rap downstream,Qp = 7080 m3/s, (3.75 h model) . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21 Scour after 49.2 hours, 14-m apron and 32 m of riprap downstream,Qp = 7080 m3/s, (5.50 h model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
22 Final design of Choke Canyon Dam stilling basin. . . . . . . . . . . . . . . . . . . . . . . . .
23 Spillway discharge curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24 Sketch of Choke Canyon Dam model safety boom. . . . . . . . . . . . . . . . . . . . . . . .
25 Choke Canyon Dam safety boom in place, Qp = 7080 m3/s . . . . . . . . . . . . . . . . .
v
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PURPOSE
A hydraulic model study of Choke Canyon Dam spillway and stilling basin, requested by
the Embankment Dams Section, Dams Branch designers, was performed to provide in-
formation needed for design. The model study was initiated to verify stilling basin
design, flow conditions, and scour in the spillway approach channel. A spillway rating
curve for the seven 15 000- by 7230-mm radial gates was developed. Scour in the
downstream channel was studied.
INTRODUCTION
The damsite is located on the Frio River in south central Texas about midway between
Corpus Christi and San Antonio. It is 5.6 km above the confluence of the Frio and
Nueces Rivers (fig. 1).
The main purpose of the dam is to provide municipal and industrial water to Corpus
Christi and adjoining areas. The reservoir also will provide some flood control and
recreational benefits. Choke Canyon reservoir will have a total capacity of 880.6 X
106m3 at the normal water surfce of 67.21 m. The active capacity will be 860 X 106 m3.
An embankment 35 m high and 5640 m long will form the reservOIr. The embankment
will be a homogeneous earthfill. A 112.8-m-wide concrete spillway will pass major flood
flows. Immediately downstream from the stilling basin, the outlet channel turns to the
right and conveys flow to the original river channel.
A 51. Anthony Falls [1]* type stilling basin, a design developed at St. Anthony Falls
Hydraulic Laboratory using chute blocks, basin floor blocks and an end sill, was con-
sidered during preliminary model calculations. It was not used because a scour hole
would develop downstream and deep scour in the outlet channel was unacceptable.
*Numbers in brackets refer to the bibliography.
Drawing model dimensions are in millimeters unless noted and prototype dimensions are
shown in meters unless noted.
CONCLUSIONS
1. A low Froude number stilling basin was designed and tested in a hydraulic model for
the choke Canyon Dam (fig. 2). As designed, the spillway and stilling basin operated ex-
cellently. During model tests, a modified stilling basin was developed that eliminated
5.48 m of the prototype sidewalls and retained a 14-m apron, resulting in a lower cost.
2. The design recommended for Choke Canyon Dam has a concrete apron 14 m long,
downstream from the end of the stilling basin, followed by a 32-m-Iong section of riprap.
3. The approach channel recommended for the prototype spillway is 125 m wide at
elevation 54.40 meters mean sea level. The inlet walls and approach channel are shown
on figure 14.
4. The spillway discharge rating curve with all 7 radial gates opened equally is shown
on figure 23.
THE MODEL
The model was constructed to a length scale of 1:80 and is shown on figure 3. The
original model inlet walls and entrance channel were modified to obtain lower velocities
and to eliminate excessive scour along the inlet walls at each side of the spillway en-
trance. Figure 4 shows the model as designed originally. The head box contained the
reservoir portion of the model. Topography of the reservoir was formed by smoothing the
sand to the same shape as the prototype.
'1""'
The prototype approach channel is a trapezoidal channel having a bottom width of
125.0 m and 2:1 side slopes. The entrance channel was set at a prototype elevation of
54.40 m.
The spillway is an overflow crest having seven 15 000- by 7230-mm radial gates. Spillway
width is 112.2 m. A chute built on a 3-percent slope is located immediately downstream
of the gate section and is followed by a vertical curve which connects to the stilling basin.
The stilling basin was designed to Bureau of Reclamation criteria [2] developed for low
Froude number flows.
Below the stilling basin, the outlet channel curves to the right. The bottom width is
112.2 m and the side slopes are 2:1. There is no slope to the outlet channel which is
at elevation 41.0 m. About 450 m of the prototype channel downstream from the
stilling basin were included in the model. This reach modeled the effect of the
curved channel on the stilling basin.
Model Similtude Parameters
The model was constructed to an undistorted scale of 1:80 and was evaluated usmg
the Froude law of similtude. Model discharges were scaled from the prototype by
the following relationship:
where(
1
)
5/2Qm =
80Qp (1)
Qm = model discharge
Qp = prototype discharge
The maximum Qp of 7080 m3/s was represented by a 0.124-m3/s Qm discharge.
Spillway velocities and discharges were represented accurately at the 1:80 model
3
scale. All model elevations were measured with respect to mean sea level (metric
scale).
Sand used in the model was scaled-based on settling velocity [3]-to nearly the
same size as the largest soil and rock at the damsite. Smaller size sediment at the
damsite was less than 75 pm (passing a No. 200 seive). The laboratory had a limited
amount of 75 pm sediment and it was placed at the downstream end of the stilling
basin. Consequently, scour around the inlet walls indicated where scour would
occur in the prototype for the largest material and these areas should be protected.
Scour below the stilling basin represented the expected prototype conditions, and
scour holes in the model bed indicated places that would need to be modified or
protected.
MODEL TESTS
Preliminary Tests
Initial tests indicated that. the spillway and stilling basin functioned well for all
discharges. However, a sharp drawdown occurred around the inlet walls of the en-
trance channel and scour occurred at the base of the walls and deposited sediment in
the stilling basin. All tests for comparing scour are for a maximum Qm = 0.124 m3/s
for 1 hour (Qp = 7080 m3/s for 8.94 hours) unless otherwise noted. One hour model
time was selected because the rate of the material removed had stabilized and little
scour (model observation) appeared to occur after an hour. Figures 5a and 5b show
the extent of scour along the inlet walls for the model as designed originally. As a
result of this scour, alternate designs for the approach channel and walls were
developed and tested.
4
Entrance Modifications
The first entrance modification proposed by the designers was a dike formed by ex-
tending the 2:1 side slopes above the normal water surface. Figure 6 shows scour
around the inlet walls and erosion of the dikes. The approach velocity was too high
in the channel and the dike was destroyed.
A second alternative was straight wingwalls at 300 to the approach channel con-
nected by circular arcs as shown on figure 7. Neither the straight wingwalls nor
wingwalls having various lengths of dikes was acceptable as shown on figures 8
through 10. The approach channel was subsequently widened to 125 m and made
1.683 m deeper to decrease the entrance velocities.
The deepened and widened approach channel decreased the velocity enough to
minimize the transport of sediment into the stilling basin. A segmented wall
resembling an ellipse was installed in the model and the maXImum model discharge
of 0.124 m3/s (Qp = 7080 m3/s) was run for 1 hour. Scour was significantly less
than any previous run. Figures lla and llb show the smaller amount of scour. Next
a 300-mm (24-m prototype) radius arc for 1200 was installed having a 3:1 side slope
at the wall and a transition to the 2:1 side slopes in 200 mm (16-m prototype). After
this configuration was operated for several hours, the 3:1 slope had scoured to
nearly a 3-112:1 slope. Therefore, the side slopes were cut to 3-1/2:1 at the inlet
walls and then transitioned to 2:1 side slopes upstream in a length of 400 mm (32-m
prototype). Figure 12 shows a discharge of 0.083 m3/s (Qp = 750 m3/s), the
equivalent of a 1000-year flood with the 3-1/2:1 side slopes. Note that the
drawdown is minimal. Scour from the maximum probable flood Qm = 0.124 m3/s
(Qp = 7080 m3/s) was slight (figs. 13a and 13b).
The design recommended for the inlet channel is the deepened and widened channel
having 24.0-m radius inlet walls and short wingwalls extending beyond the curves.
Figure 14 shows the recommended design of the inlet walls, and approach and en-
trance channels.
5
Stilling Basin
The original design of the stilling basin is shown on figure 2. This design worked
well throughout the range of discharges tested with less than 2 meters of vertical
scour downstream from the apron. Several different floods were tested, from less
than the lO-year return frequency up to the maximum probable flood of 7080 m3/s.
The largest scour occured at Qm = 0.124 m3/s (Qp = 7080 m3/s) discharge and had
stabilized in about an hour of model time (8.94 h prototype). There was a slight
asymmetry to the scour pattern with more scour occurring on the left side of the
channel.
The designers suggested a test be performed usmg a discharge simulating a
lOOO-year flood (4750 m3/s) and that the length of the stilling basin site walls be
shortened so that this flood would still be contained in the basin. Tests were made
with stilling basin sidewalls shortened 5.48 m. These tests developed scour holes
downstream from the end sill, with the scour hole on the left side about 2 m deeper
than the right side. Figure 15 compares the scour with the sidewall cut back 5.48 m
from the original design with and without the downstream apron. Note the scour
hole on the left is about 2 m deeper than the right. Each contour line represents a
I-m difference in elevation.
As water flowed around the channel bend downstream from the stilling basin, it
. became superelevated and caused an upstream current along the left bank between'
the curve and the stilling basin. The upstream current mixed with water leaving the
stilling basin, and a scour hole was caused by the resulting vortex.
Several tests were made to obtain a solution to the scour along the left side of the
channel.
A 2-1/2:1 side slope around the inlet sidewall replaced the 2:1 side slope. A transition
to the 2:1 slope downstream from the stilling basin was made in 400 mm (32-m pro-
totype). Figure 16 shows the scour from a 1- hour test at the maximum probable
6
flood Qm = 0.124 m3/s (Qp = 7080 m3/s). Figure 17 shows the scour from a model
discharge that was allowed to run until equilibrium was obtained. This run
represented 53.7 hours in the prototype (6-h model).
A wall 14 m long along the left side provided an acceptable solution but was longer
than the original design. A more economical solution was desired. A low wall,S m
high and 14 m long, also was tried unsuccessfully.
Because scour was occurring along the floor of the stilling basin, the apron was ex-
tended 14 m downstream. Scour for this design with discharge of 7080 m3/s for 8.94
hours was acceptable (fig. 18). A 32-m-Iong blanket of riprap was placed
downstream of the apron for additional protection. This configuration was tested
and scour measurements were observed at 1, 3.75, and 5.50 hours model times (8.9,
33.5, 49.2 h prototype). Figures 19 to 21 show the scour that resulted from these
tests. Performance of the basin shortened by 5.48 m from the original design, and
with rip rap installed downstream was acceptable for the maximum design flood and
smaller floods.
The recommended design for the stilling basin was a concrete apron extending 14 m
beyond the end sill with a 32-m-Iong rip rap section downstream. The final design
(fig. 22) has an 8.8-m apron and 30 m of riprap. A savings was realized from the
shortened walls.
Radial Gate Calibration
The radial gate seat is 0.214 m below the spillway crest. All gate openmgs are
referenced to vertical distances above the crest for the model tests. Gate opening
curves at I-m intervals and for free discharge, were developed and scaled to pro-
totype values (fig. 23). Figure 23 represents the discharge capacity curve for the
gated structure with all seven gates opened equally. Gates were set at a particular
7
gate opening and the model was operated at a constant discharge until the water
surface remained stable. Data were recorded for the water surface and discharge.
Several discharges were tested for each gate opening to develop each curve. Each
discharge was run for about 1 hour model time-generally long enough to maintain
a stable water surface upstream of the dam in the model.
Safety Boom
A safety boom upstream from the spillway crest was designed and tested in the
model. The final layout for the safety boom and anchors is shown on figure 24.
Figure 25 shows the safety boom at the maximum probable flood, Qm - 0.124 m3/s
(Qp = 7080-m3/s). After the model boom was installed, several tests were run to
check if the safety boom affected the discharge curves. The discharge curves did not
change.
8
flood Qm = 0.124 m3/s (Qp = 7080 m3/s). Figure 17 shows the scour from a model
discharge that was allowed to run until equilibrium was obtained. This run
represented 53.7 hours in the prototype (6-h model).
A wall 14 m long along the left side provided an acceptable solution but was longer
than the original design. A more economical solution was desired. A low wall,S m
high and 14 m long, also was tried unsuccessfully.
Because scour was occurring along the floor of the stilling basin, the apron was ex-
tended 14 m downstream. Scour for this design with discharge of 7080 m3/s for 8.94
hours was acceptable (fig. 18). A 32-m-Iong blanket of riprap was placed
downstream of the apron for additional protection. This configuration was tested
and scour measurements were observed at 1, 3.75, and 5.50 hours model times (8.9,
33.5, 49.2 h prototype). Figures 19 to 21 show the scour that resulted from these
tests. Performance of the basin shortened by 5.48 m from the original design, and
with riprap installed downstream was acceptable for the maximum design flood and
smaller floods.
The recommended design for the stilling basin was a concrete apron extending 14 m
beyond the end sill with a 32-m-Iong rip rap section downstream. The final design
(fig. 22) has an 8.8-m apron and 30 m of riprap. A savings was realized from the
shortened walls.
Radial Gate Calibration
The radial gate seat is 0.214 m below the spillway crest. All gate openmgs are
referenced to vertical distances above the crest for the model tests. Gate opening
curves at 1-m intervals and for free discharge, were developed and scaled to pro-
totype values (fig. 23). Figure 23 represents the discharge capacity curve for the
gated structure with all seven gates opened equally. Gates were set at a particular
7
gate opening and the model was operated at a constant discharge until the water
surface remained stable. Data were recorded for the water surface and discharge.
Several discharges were tested for each gate opening to develop each curve. Each
discharge was run for about 1 hour model time-generally long enough to maintain
a stable water surface upstream of the dam in the model.
Safety Boom
A safety boom upstream from the spillway crest was designed and tested in the
model. The final layout for the safety boom and anchors is shown on figure 24.
Figure 2S shows the safety boom at the maximum probable flood, Qm - 0.124 m3/s
(Qp = 7080-m3/s). After the model boom was installed, several tests were run to
check if the safety boom affected the discharge curves. The discharge curves did not
change.
8
BIBLIOGRAPHY
[1] Blaisdell, F. W., "Development and Hydraulic Design, Saint Anthony Falls
Stilling Basin," Trans., Am. Soc. Civ. Eng., vol. 113, Paper No. 2342, pp. 483-
561, 1948.
[2] George, R. 1., "Low Froude Number Stilling Basin Design," REC-ERC-78-8,
16 pp., Bur. Reclam., 1978.
[3] Enger, P. F., "Hydraulic Model Studies of Bartley Diversion Dam-Progress
Report No.3 on General Studies of Headworks and Sluiceway Struc-
tures," Missouri River Basin Project, Nebraska, Laboratory Rep. Hyd-384,
February 1954.
9
. (f)
~\ :)
::!' :
Figure I.-Location map for Choke Canyon Dam.
AIL-~'"
-0.94 -.JAPLAN
~::::~ r
r--l
rT:6E3~ 410,~E~983. }--274 ~ 3154~
J---,I
"~'%~:;;e
I:
'''' ,;1"
""J ""
~.I
m
SECTION A-A
Figure 2.-Sketch of low Froude number stilling basin-Choke Canyon Dam-original design.
10
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r--- - ~
671-
N O T E S O r l g t n o f c a o r d n o t e i , nor theas t carr ier o t heod box
3 E T A I L A - A $'ALE i d
D I M E N 5 1 0 N S I N n m
Figure 3.-Drawing of the model-showing the original model design.
I I
Figure 4.-Model as designed originally. The inlet walls were modified as was the approachchannel. P801-D-79816
13
Figure 5a.-Scour around left inlet wall, Qp = 7080 m3/s tested for8.94 hours-model as designed originally. Contour lines in meters.P801-D-79817
Figure 5b.-Scour around right inlet wall, Qp = 7080 m3/s tested for8.94 hours-model as designed orginally. Contour lines in meters.P801-D-79818
14
Figure 6.-Scour pattern with straight dikes, Qp - 7080 m3/s tested for 8.94 hours.P801-D-79819
15
425
457.3
_El 550 ""
'".0
'"
~...
'"
El 393.7
430.5
El 393.7
A- --<1--
25.5
-<JA
1410
"-DAM CREST
STA 262.9
El 332.7
1410
~r
~El311.8
466.8
------~
j21
SANDEL 311.8
1562.1
PLAN
SCALE 1'8
El 527
~ ------
------
263.2
I.
SECTION A-AHALF SCALE
~
------
wooo
183
375
_El 550~
- ~
NOTE: ALL DIMENSIONS mm
95.3
------
El 332.7
Figure 7.-Sketch of model with 30° wingwalls.
16
------------
Figure 8.-Scour around right 30° wingwall with 100-m dike,Qp = 7080 mats for 8.94 hours. P801-D-79820
Figure 9.-Scour around left 30° wingwall with 100-m dike,Qp = 7080 mats for 8.94 hours. P801-D-79821
17
Figure 1O.-Scour in vicinity of 30° wingwall with 200-m dike, Qp8.94 hours. P801-D-79822
7080 m3/s for
18
~r.."..~
Figure lla.-Scour with segmented right inlet wall, Qp = 7080 m3/sfor 8.94 hours. P801-D-79823
",/\"
t~"A
.....
Figure llb.-Scour with segmented left inlet wall, Qp = 7080 m3/s for8.94 hours. P801-D-79824
19
Figure 12.-Model discharging 0.083 m3/s (Qp = 4750 m3/s), equivalent to lOOO-yearflood.P801-D-79825
20
Figure 13a.-Scour from 300-mm (24 m prototype) radius inlet wall with4OO-mm (32 m prototype) extension at 900 to left inlet wall.P801-D-79826
Figure 13b.-Scour from 300-mm (24 m prototype) radius inlet wall with21O-mm (16.8 m prototype) extension at 1200 to right inlet wall.P801-D.79827
21
----
NN
34.00
36.584- EL 13.65 "'"STAO+OO
R 24.000
TRANSITION 3 ~:I TO
2:1 SIDE SLOPES
60.256
2:1
34.440
2: I SLOPE TOPS OUT ATEL 64.00
112.200
It. DAM CREST EL 60.810
ST A 5 + 00.000
PIERSGATE SEATEL 60.596
INLET WALLS
32.000
30.000
--
', EL 73.65
-2:1
HYDRAULIC MODEL LENGTHSCALE I: 80
Figure 14.- Recommended design of inlet walls and approach channel- Choke Canyon Dam.
ENTRANCE CHANNEL EL 56.08
~EL
~t
54.40~
APPROACH CHANNEL
125.000
PLANSCALE 1:8
ALL DIMENSIONSIN METERS
,.
~ I J III ~J ~J
Figure 15a.-Scour pattern with sidewalls shortened 5.48 m and originalapron, Qp = 7080 mats for 8.94 hours. P801-D-79828
J ~} Jj
Figure 15b.-Scour pattern with sidewalls and apron shortened 5.48 m,
QE = 7080 mats for 8.94 hours. Contour lines represent I m.PtlOl-D-79829
23
Figure 16.-Scour pattern with 2-1/2:1 side slopes around side-walls, basin shortened 5.48 m, Q = 7080 m3/s for 8.94 hours.P801-D-79830
p
Figure 17.-Long-term scour test, Qp = 7080 m3/s for 53.7 hours(6-h model time). P801-D-79831
24
Figure 18.-Scour after 8.94 hours at Qp = 7080 m3/s with 14.m apron.P801-D.79832
Figure 19.-Scour after 8.94 hours with 14-m apron and 32 m of riprapdownstream, Q = 7080 m3/s. Contour lines represent 1 meter.P80I-D.79833
p
25
Figure 20.-Scour after 33.5 hours, 14-m apron and 32-m of nprapdownstream Qp = 7080 m3/s,(3.75 h model). P801-D-79834
Figure 21.-Scour after 49.2 hours, 14-m apron and 32 m of nprapdownstream, Qp = 7080 m3/s, (5.50 h model). P801-D-79835
26
,--I 0 0 m Riprap an symmli i ta lo&ul E i p i l l v o y -
SECTION C-C
SECTION 8 -8
~ " S P o r o a o u f i e t wirh R " S P urnin a d ~ e f with colked ioints . p - S T D 6+03 .0W Calked joints - - ST4 6 t03.WO
Cr J
' 8 " P e d o r o k d ' S P d r o r n -i--~ .,_-_, ,
AnchOr bori notshown ----- Anchor ban not shown/
S E C T I O N 0 - D SECTION E - E SECTION F - F
Floor t h i c k n e i ~
t i i Arlchar Dorr
NOTES 08meniiOns unless O ~ ~ P ~ Y I I P tho*" ore I m e t e r s i i o f i o n i ond elevat loni ore in m e t e r s
SECTION G - G Tor geoeral nottr and reference drowmqr see Ow9 1012-0-74
H Y L F PLDN DETAIL X
' ' ST& 6 + jl.LX70 .- ( id 5 *,'090- ~ S I B 6625. i00 F i A 6*36.150 - s i l 6 'U?OO L i ' ~
- -2 . ~--- , , , . ." . , Drto8i Y ' - " 0.750
511 61 56.000
, , r , ,
5 P droln
/ ( "<h" i b o r r no1 $how" COnciele pad
embedded into f o ino i i on - ~ ~ - ,-
DETAIL Y
"ii b n i h o r b o i i I
D E T A I L 2
SECTION A - A 8 "crm
@ nuunvr rvlnr SbfETY Y l i / E D 5 T l r r S
O C D l F i i l E h i O i ,Hi i l i i i F i o i e U e C l " OF R E C L I * l l r l D N
N U E C E S R i V E R P R O J S C T - T E X L 1 S
C H O K E C A N Y O N D A M SPILLWAY
FLOOR STA 5 + 9 3 . 5 0 0 TO STA 6 i 5 6 . 0 0 0
~ .,., o... ... "C"
e..,"... *DLD..DD CC.D.C" lS #.-I I 1012-D-90
Figure 22.-Final design of Choke Canyon Dam stilling bunin. 27
71
70
69
68
67E
Z0I- 66c(>ILl...JILl
6!S0::
N 0\0>0::ILl
64rnILl0::
63
62
61
60
70.96 MAXIMUMWATER SURFACEELEVATION
V V jY V
/ y~/ ">9
~~S / / y'"~I
V~<IISj I,
1/ 1/1/
+J........
..../
I
'" / /....'"!I J /
il 1/ / / /"/"'"
il 1/ / '1~:.;\..o~~~~~I
I<:r /"
II / '1 /',/
GATE OPENING IS VERTICAL DISTANCE ABOVE SPILLWAY CREST// 7 GATES OPENED EQUALLY
~'I
L1SPILLWAY CREST ELEVATION 60.810
'" GATE SEAT ELEVATION 60.596Q..0
.../ien
~/VLJ
/I-- //
VSPILLWAY CREST
ELEVATION 60.810
-
I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I!S90 1000 2000 40003000 !Sooo 6000 7000
DISCHARGE. m3/s
Figure 23.-Spillway discharge curves-Choke Canyon Dam.
2000
~1850 ~
~;;;,
~/~
~t
Note:All dimensions mm
Figure 24.-Sketch of Choke Canyon Dam model safety boom.
Figure 25.-Choke Canyon Dam model safety boom in place, QpP801-D-79836
7080 m3/s.
GPO 836.. 917
30
Mission of the Bureau of Reclamation
The Bureau of Reclamation of the U.S. Department of the Interior is responsible for the development and conservation of the Nation's water resources in the Western United States.
The Bureau's original purpose "to provide for the reclamation of arid and semiarid lands in the West" today covers a wide range of interre- lated functions. These include providing municipal and industrial water supplies; hydroelectric power generation; irrigation water for agri- culture; water quality improvement; flood control; river navigation; river regulation and control; fish and wildlife enhancement; outdoor recreation; and research on water-related design, construction, mate- rials, atmospheric management, and wind and solar power.
Burea~~ programs most frequently are the result of close cooperation with the U.S. Congress, other Federal agencies, States, local govern- ments, academic institutions, water-user organizations, and other concerned groups.
A free pamphlet is available from the Bureau entitled, "Publications for Sale". I t describes some of the technical publications currently available, thei~ cost, and how to order them. The pamphlet can be obtained upon request from the Bureau of Reclamation, Attn 0-922, P 0 Box 25007, Denver Federal Center, Denver CO 80225-0007.