Summaries
Gates and operating mechanisms for the
Oosterschelde-barrier
This article can be seen as a sequel to one on
the same subject in the previous Threemonthly
Review of the Deltaproject.
Two independently operating hydraulic
lift-mechanisms will be installed at each gate.
These mechanisms will be housed in containers.
The electric installation must be of a prime
quality with the lowest chance possible of
failure - one thousandth time per annum. It
must react immediately if the tolerated incline
of the gates is exceeded. The electric power
required for special circumstances will be
provided by an independent power plant. A 10
kV circuit will continuously supply electric
power to all installations.
Local electric installations check the functioning
of the electric and the hydraulic installations
uninterruptedly.
The design of the sill
The sill of the Oosterschelde-barrier will be
built as an open filter construction. The
material used for the lowest layer of this filter
will have a diameter of 0,02 m, whereas the top
layer will consist of material with a diameter of
1 m. The dimensions required for the interme
diate layers have been defined in hydraulic
models.
Here the stability of each layer during construc
tion was checked. In the end situation the
assumption has been made that one gate will
fail to close. Exposure of the next layer was
maintained as a criterion for failure.
The top layers wil be positioned with the aid of
special grabs.
Morphological changes in the Krammer and
Slaak channels
Since 1962, great morphological changes have
taken places in the Krammer and Slaak channels,
as a result of the closures of the Grevelingen
and the Volkerak, as well as of the construction
of the working-island for the Krammer Sluices.
The Krammer has been expanded and bent out
continuously. Finally, the maximum depth had
increased to 24 m below MSL, mainly as a
result of the permanent dominance of the
ebbtransport over the floodtransport.
In fact, the Plaat van de Vliet, a shoal on which
the working-island was built, came into being
only after these developments started.
Breach of the western dike of the Markiezaat
On March 11, 1982, the western part of the dike
surrounding the area known as the Marquisate
of Bergen op Zoom, was breached during a
storm. This incident endangered particularly
the shipping on the Schelde/Rijn-connection as
well as a power pylon in the immediate
vicinity. Emergency measures had to be taken
immediately.
The breach must be repaired as soon as
possible. Various possibilities to do this have
been investigated. It was decided that the new
closure will be executed in the axis of the
former alignment. As the breach can only be
filled after the stormy 82/83 season, this means
that throughout next winter period there will
remain a breach, enlarged to 800 m.
After the closure has been completed the entire
Marquisate dike will be raised. The costs will
approximate 35 million guilders.
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