The design of the storm-surge barrier; its
evolution to date
From recent investigations we learned that the
perpendicular loadings on the storm-surge
barrier are estimated to be 20% less than
previously assumed. In other elements of the
design, adjustments are still being carried
out to meet the changing insights. The diameter
of the piers will be increased but the height can
be decreased. The sill beam which formerly was
designed as a rectangle will now have the shape
of a trapezium.
In the final design enough spare room is added
to the wet cross-section so that the desired tidal
range of 2.70 meter at Yerseke can certainly be
achieved.
Inter-action of the piers of the storm-surge
barrier with the sill and the sub-soil
The piers of the storm-surge barrier will have to
transmit the forces of the wave action and the
tidal range which are exerted on the barrier, to
the sub-soil. This partly occurs along the base
and partly along the walls of the pier. To be able
to calculate the dimensions of these
complements it is necessary to know how these
forces are distributed. Regarding the friction
resistance between the base and the foundation
bed large scale tests have been made in
Schelphoek.
At the same time the amplitude of the lateral
load on the piers was examined. Only a slight
dislocation of the lower sill beam was observed.
In view of the great differences in water level
which may occur between the outer water and
the estuarine water when the barrier is closed,
additional heavy blocks of stone will have to be
dumped atthe Oosterschelde side.
Geo-pontoon and diving-bell
The plan to construct a movable barrier across
the mouth of the Oosterschelde made it
necessary to intensify the soil mechanical
research in situ and to execute this research at a
much greater depth than before. Consequently
additional new equipment was needed. In this
paper two pieces are discussed namely the
geo-pontoon, an auxiliary vessel forthe
execution of soundings and drillings; and a
diving-bell - weighing 70 ton - which can be
lowered into the water from the geo-pontoon.
The diving-bell which can withstand a water
pressure of 200 meter is mounted on a footing
and can move in any direction by means of a
ball bearing. It can be jacked into a straight
upright position even on an inclining bottom.
From within the bell soundings and drillings can
be made. Windows permit visual observation.
Positioning service vessels across the mouth of
the Oosterschelde
During the construction of the storm-surge
barrier the works onorunderthe water will
mostly be done with the aid of vessels. They are
not permitted, however, to anchor in the
conventional way as this may damage the
bottom protection. Therefore a pattern of fixed
mooring-masts has been set out where vessels
can achor in the work-area. Every mooring-masl
has a cast iron top.
The masts, complete with the cast iron tops, are
driven into the sea-bed.
Water managerial aspects in the Delta area
The Zeeland waterways are interconnected
either via open water or via locks. The various
systems, especially as far as the salinity,
nutrients level and water level are concerned,
have either to be fully attuned to one and
another or to be strictly isolated by hydraulic
engineering structures. As the Oosterschelde
remains in open communication with the sea
and thus will retain its salt tidal system, the
water managerial aspects will all have to be
reviewed. In this paper an inventory is made of
the external influences which can affect the
system of the Oosterschelde.
To ascertain that the desired degree of salinity
will indeed be achieved in the partially closed
Oosterschelde an insight should be gained into
the extent of the various influences and their
mechanisms. In this paper various methods of
research into the matter are discussed. An
assumption has been made that, at a later date,
the stormsurge barrier can also be used to
control the salinity of the water.
The water level on the Zoommeer
The water level on the fresh water Zoommeer,
behind the Philipsdam and the Oesterdam,
could, if so desired, remain at a fixed level,
fluctuate or change with the seasons.
Investigations are made to establish which
situation corresponds best with the interests of
water management, navigation, recreation,
agriculture and energy supply. In general a
fixed target level around N.A.P. would be most
favourable for all parties concerned. Advice
will be given accordingly.
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