April 12, 2012

Vermelding onderdeel organisatie

1

Chapter 17: Review

ct5308 Breakwaters and Closure Dams

H.J. Verhagen

Faculty of Civil Engineering and GeosciencesSection Hydraulic Engineering

Emergency closure at Westkapelle1944 (photo: National Geographic

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advantages and disadvantagesrubble mound monolithic

• simple construction• withstand unequal settlement• large ratio between initial damage

and collapse• many guidelines available• dependence on the availability of

adequate quarry• large quantity of material required

in deep water• large space required• difficult to use as quay wall

• short construction time on location• can function as quay wall• economical use of material in deeper

water• sensitivity to poor foundation

conditions• uncertainty about wave loads in

breaking waves• complete and sudden failure when

overloaded• reflection against vertical wall• limited support for the designer from

guidelines and literature

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Quarry stone or concrete ??

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which design formula ???

( )

3

33 cos sinrN gHW ρ

μ α α≥Δ +

3

3 cotr

D

g HWKρ

α≥Δ

0.20.18 0.5

50

0.20.13

50

6.2 (plunging breakers)

1.0 cot (surging breakers)

sc

n

Psc

n

H SPd N

H SPd N

ξ

ξ α

−

−

⎛ ⎞= ⎜ ⎟Δ ⎝ ⎠

⎛ ⎞= ⎜ ⎟Δ ⎝ ⎠

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SLS and ULS

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Closure dams: special conditions

• subdivision of the basin in order to reduce storage area

• subdivision because of two entrances• a closure with two or more entrances

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two ways to reduce the area of a basin

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a basin with two entrances

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an estuary with two channels

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The gap is not (yet) in equilibrium

• stabilise the bottom of the gap as soon as possible

• avoid erosion of gullies in the storage area

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closure dike breach Ouderkerk aanden IJssel (1953)

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closure alignments