Summaries
The foundation mattresses of the piers for the
Oosterschelde barrier
The foundation of the piers for the
Oosterschelde barrier must satisfy high
tydraulic and soil mechanical requirements.
The cyclic energy gradients appear to be
lighest directly under a pier, on the boundary
one between the pier and the natural sub-soil.
The first three filter-layers of the foundation bed
herefore could only be placed in a pre-packed
orm so as to prevent dissolution and the
nclosure of sand lenses. This method, in its
urn, created new problems; it proved that
ometimes the top of the layer was not
ufficiently smooth, preventing complete
dhesion between the filtermattress and the
eabed, thus allowing piping towards cavities
inder the mattress. This would be
nadmissable, in particular directly underthe
piers.
luctuations of the bed in the Oosterschelde
Since 1870, information has been available
bout regular soundings of the
)osterschelde-bed. From 1959 onwards, these
oundings have been taken annually. It is now
pparent that apart from the tendency of
hifting in the long run - as happens with the
couring of the channels and heightening of the
hoals - short term fluctuations also occur.
study has been made of these short-term
hanges in an area near the Roggenpiaat
eparately overthe period 1959-1969 and the
ieriod 1969-1979, in three different types of
ectors: the shoal areas, the beds of the
hannels and the sides of the channels. The
eneral conclusion of this study was, that the
influence of the execution of the works, if any,
was to slow down and stabilize the
morphological processes.
Study of flushing the Oosterschelde
As a result of the reduction of tidal action in the
Oosterschelde after the construction of the
Oosterschelde barrier, the mixing process of the
North Sea and Oosterschelde waters will
decrease; to what extent will actually depend
upon the processes in operation. The whole
process of mixing is of great importance to the
future salinity in the Oosterschelde. In order to
support already published literature and
existing field measurements, the anticipated
mixing situation has been investigated in two
models, i.e. in the M1000, a physical model of
the Oosterschelde and in the 'Ooster', a
computermodel. The result derived, confirmed
the validity of previous research and the
measurements.
Tree planting on the Volkerak-constructions
Tree planting on the Volkerak-constructions is
partially purely functional; in order to protect
shipping against heavy winds when coming
into the locks, belts of trees have been planted.
Plans have also been made to plant trees on the
extensive grounds which formerly served as
spoil dumps. One of these plans has already
evolved into 'the Willemstad Woods' and
covers an area of 65 has. The trees that have
already been planted are growing well. The
future management of this tree plantation is still
under discussion.
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