dike and stopbank breaching due to overtopping
TRANSCRIPT
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Dike and stopbank breaching due to overtopping
By
Ninger Kong
Supervised by
Associate Prof. Asaad Yahia Shamseldin
Prof. Bruce William Melville
Colin Nicholas Whittaker
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Contents
Previous
• Background
• Dike failures and reasons
• Parameters in dike erosion
• Previous physical experiments
• Research gap
Current
• Experiment setup
• Experimental groups
• Erosion process
• Flow velocity
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Background
Collapse of the water side slope of a stopbank due to scouring, Kōkōhinau Bend, 2004.
The storm surge produced by Hurricane Katrina overwhelmed numerous levees and caused failure of levees, New Orleans, 2005.
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The reason of dike failures
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Parameters in experiments
• Dike (stopbank) dimension (geometric design)
➢ Dike (stopbank) shape
➢ Dike (stopbank) size
• Material
➢ Sediment diameter
➢ Non-cohesive and cohesive material
➢ Mixed material
➢ …
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Parameters in experiments
• Hydraulic condition
➢ Constant upstream water level
➢ Constant inflow rate
➢ Wave impact
➢ Downstream boundary condition
➢ …
• Compaction
• others
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Previous physical experiments
Dike• Experimental setup
Coleman (2002)Purpose:Breach crest shape
Shortcoming:• Seepage effect• Flow velocity
field in the breach
Schmocker and Hager (2009)Purpose:Eliminate the effect of scale, side wall and cohesionShortcoming:Plane breach mode
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Previous physical experiments
• Experimental setup
Stopbank
Rifai (2017)Purpose: the development of stopbank breaching Shortcoming: use other data to deduce the velocity of one point
Wei (2016)Purpose: breaching processShortcoming: seepage effect and not suitable velocity measurement
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Research gap and our aims
• Measure the flow velocity in the breach
• Find the relationship between varies observations
• Use formula to calculate velocity distribution in the breach
• Study the scale effect on dike erosion
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Differences between dike and stopbank
Differences
• Breach evolution
• Breach shape
• Flow velocity in the breach
• …
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Dike experimental setup
12
3notch
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Experimental groups
Test w(m) h(m) Slope b(m) d50(mm) Qi(L/s)
Test 1 0.05 0.1 1:2 0.4 0.85 0.5
Test 2 0.05 0.1 1:2 0.4 0.85 0.8
Test 3 0.05 0.1 1:2 0.4 0.85 1.0
Test 4 0.05 0.1 1:2 0.4 0.85 1.2
Test 5 0.05 0.1 1:2 0.4 0.85 1.6
Test 6 0.05 0.1 1:2 0.4 0.85 2.0
… … … … … …
hmax=0.8m wmax=0.4m b=1.2m
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Erosion process
x
z y
Plane breach mode (1.2L/s)Spatial breach mode (0.5L/s)
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Flow velocity field
Dike upstream
Front of the breach
Middle of the breach
End of the breach
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Thanks!
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Vertical and horizontal erosion rate
x
z
x
y