piano key weir: an innovative spillway upgrade at ... piano key weir: an innovative spillway upgrade...

Piano Key Weir: An Innovative Spillway Upgrade at Dartmouth Dam (Australia) Mike Phillips & Eric Lesleighter

Presented by: Blake Tullis

Utah State University

2nd International Workshop on Labyrinth and Piano Key Weirs Nov 20-22, Paris

PKW 2013 - Presenter: Blake Tullis

91 m

180 m


Purpose of Project Develop upgrade options to pass PMF for

Dartmouth Dam - PMF inflow = 20,000 m3/s

- Ogee crest spillway capacity of 4,400 m3/s

- Several upgrade options considered

Increase embankment dam height by 3.4 m

Replace linear ogee weir with Piano Key Weir (head = 11.4 m)


Piano Key Weir Option for Dartmouth Dam Piano Key Weir Preliminary Design

- Initial design based on available technical publications (HYDROCOOP in France)

- Max. head = 11.4 m

- W = 91 m (existing spillway width)

Piano Key Weir design progression - Test preliminary design in physical hydraulic model

- Optimize configuration in CFD model

- Test and confirm design in physical model

Initial Piano Key Weir Testing


Physical Model Study

1:60 Scale Model


7 cycles 91m wide (total)

Initial Testing of Piano Key Weir

1 2 3 4 5 6 7


1,080 m3/s


10,200 m3/s


Flow constriction

at discharges >6,000 m3/s

Vortex formation

Ineffective flow area


Streamlined support section


Nearly eliminated

vortex formation


Streamlined entrance

conditions


10,900 m3/s (11.4m head)

Optimisation in CFD Model


CFD Modeling (Optimization)

Model Verification to Physical Model with 11.4 m head: - Physical model = 10,900 m3/s

- CFD model = 10,950 m3/s


CFD Modeling (Optimisation)

Shape of wall crest (1/2 round) ~ +2% at low to mid-range flows

Approach depth (2m) ~ +2%

round crest

2m approach

depth

Flow


CFD Modeling

Upstream edge of slab shape (sloped) ~ +1.6% increase

Sloped entrance

Flow


CFD Modeling

Shape of block under downstream overhang to reduce flow constriction(45deg) ~ +2% for high flows

Evaluated 1.0 Wi/Wo 1.4 1.2 ratio selected (other ratios reduced discharge)

45deg exit support

Flow


Structural Analysis

Shear strength - Centre wall thickness

changed from 1.2 m to 0.75 m

- Upslope wall thickness changed from 0.6 m to 0.75 m

- Meets all load cases

45deg exit support

One Cycle

Flow

Flow


Structural Analysis

Sliding FOS > 4 (2.3 for zero cohesion)

Overturning: - Piers under downslope

Walls extended upstream by 3.5 m

- Slab extended downstream by 2.0 m

45deg exit support

One Cycle

Slab Extension Piers

Extended upstream

Flow

Flow

Final Piano Key Weir Testing


Detailed Testing Phase


486.0

487.0

488.0

489.0

490.0

491.0

492.0

493.0

494.0

495.0

496.0

497.0

498.0

0

1000

2000

3000

4000

5000

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7000

8000

9000

1000

0

1100

0

1200

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Res

ervo

ir Le

vel (

mA

HD

)

Discharge (m3/s)

Stage 2 PKW vs Stage 3 PKW

Stage 2

Stage 3

Dam Crest (El. 494.0)

Parapet Wall Crest (El. 497.4)

8,400 m3/s

11,500 m3/s

10% increase in capacity with

modifications from CFD model


11,500 m3/s

Negative pressure under downstream overhangs

(>9,500 m3/s)

Water impacting directly on the chute slab


Dual Aeration Splitters

(Cycles #2 to #6):

3m high; 4m long

PKW 2013 - Presenter: Blake Tullis 27

Negative Pressure Aerated Flow


Dynamic Pressure Testing

Weir centre wall - Frequencies not

likely to induce resonance

Spillway chute at jet impact location

- High static and dynamic pressures

- Increase chute slab thickness by 0.5m and anchor to rock

PKW 2013 - Presenter: Blake Tullis 850 m3/s 4,000 m3/s

8,400 m3/s 11,500 m3/s

piano key weir: an innovative spillway upgrade at ... piano key weir: an innovative spillway upgrade...

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