Transcript Roxburgh Dam

Roxburgh Dam
Combined Discharge of Spillway and Sluice
into the same Chute
Peter Silvester – Civil Engineer Contact Energy
Grant Webby – Principal Hydraulic Engineer Opus International Consultants
Roxburgh Dam - Location
Roxburgh Dam
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Roxburgh Dam
Commissioned 1956
50m high concrete gravity
320 MW power station
Mean flow 507 cumecs
PMF 7,000 cumecs
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Roxburgh Dam Spillway
Three Spillway Gates
15.2m wide x 13.4m high.
Discharge capacity 4,750
cumecs
Two diversion sluices
7.1m wide x 8.7m high.
Discharge capacity 2,900
cumecs.
Combined total discharge
capacity 7,650 cumecs.
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Roxburgh Dam Spillway
Spillway chute 3
dewatered
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Diversion Sluices
Sluices
7.1m wide
8.7m high
Spillway – Sluice Long Section
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Physical Hydraulic Model
University of Auckland
Tests covered:
•Sluice only operation -
25
•Spillway only operation - 25
•Combined operation -
125
•Total tests
175
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Physical Hydraulic Model Observations
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Physical Hydraulic Model Results
Maximum pressures along sluice
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Physical Hydraulic Model
Rooster Tails
Sluice only
operation
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Gate Tests
Jan 2013
Sluice 2 opened 6.77m (78%).
Discharge 862 cumecs.
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Sluice Gate Test
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Conclusions
• Physical hydraulic model investigations supported by prototype testing have successfully proved for the Roxburgh Dam
case that simultaneous discharge from a spillway gate and a low level sluice gate into the same chute is feasible and will
produce smooth merged flow lines.
• For sluice only operation the discharge will not pressurise the sluice tunnel.
• Spillway only operation will pressurise the sluice tunnel only at high lake levels and gate openings greater than 40%.
• Combined spillway and sluice operation will pressurise the sluice tunnel only at high lake levels and spillway gate openings
greater than 40%.
• The water levels induced in the sluice gate chamber by the back pressure from spillway only or combined spillway and
sluice operation are unlikely to flood the middle gallery in the dam where the sluice gate controls are located. However
further prototype tests are desirable to confirm the extreme water level values observed in the model tests.
• Although the sluice is back pressured by the spillway the discharge from the sluice is not reduced.
• ‘Rooster tail’ behaviour along each side wall at the sluice exit into the spillway chute could threaten the access bridge to the
power station under high sluice only flow conditions at a high lake level.
• Roxburgh Dam can safely pass the PMF inflow using the combined discharge from both the spillway and sluice gates fully
open at a lake level of RL 132.3m (I.e. with 1.2m freeboard).
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