through constant adjustment of the model that
the factor of uncertainty has been reduced to
an acceptable level. An extensive measuring
program had to be carried out for this pupose,
in which amongst other things photo-
reconnoitring apparatus was used in order to
make a record of so-called sediment tracks.
Clay as a foundation layer of a concrete block
slope
There are certain advantages in a clay layer
under the concrete block slope of a water
barrier. The stability of the defence is increased
when the proper clay sort is used in comparison
to other materials and when good processing
and condensing is applied. Much research into
this construction has been carried out recently
as clay layers are being applied under the
concrete block slopes of the Oester and the
Philips dams. Due to its sensivity to erosion
there remains an element of uncertainty, and
research will be continued into this aspect.
The siphon in the Grevelingendam
The completed Flakkeese Spuisluice, a siphon
construction in the Grevelingen dam which
conveys water from the Grevelingen into the
Krammer, has been delivered this year. Some
details of the outflow construction in the
original design have been amended. In this
article the construction designed to allow the
siphon to start up and turn off automatically is
discussed. An effective pressure installation
provides for a water parting between the two
waters when there is a high water level in the
Krammer.
Experiments were carried out with the new
sluice between October 1983 and January
1984, and a measuring program has been set
up for the coming winters which is to observe
the effects of the siphon on the hydraulics in
the upper Oosterschelde.
Future lay-out of the work island Neeltje Jans
On completion of the Oosterschelde the work
Island Neeltje Jans can be used for other
purposes besides hydraulic engineering. As a
result of 'Policy Plans for the Oosterschelde
1982', research has been set up into the
possible functions of the area. Functions can
be distinguished with regard to hydraulic
engineering, services, nature, fishery and
recreation, information and presentation.
Five alternative function combinations which
could be realised on Neeltje Jans have been
formulated. There is a minimum alternative
which is to await developments, a fishery
alternative, an alternative for presentation and
innovation, a day recreation alternative and an
integration alternative in which all imaginable
developments are represented in a balanced
whole.
The group in charge of the Oosterschelde has
recently chosen for the integration alternative.
The strengthening and raising of the water
barriers along the Rijkszeehaven 'Het Nieuwe
Diep' at Den Helder
Part of the water barrier along the Rijkszeehaven
'Het Nieuwe Diep' was strengthened and raised
during the fifties and sixties.
The second phase in this operation began in
1973 with the replacement of the Zeedok lock.
Next came the adjoining dike sections and
finally the last section of this water barrier was
built in 1978. As there was litttle opportunity of
extending the dike-body inland, dam-walls or
L-shaped walls were used in order to reduce
the inner slope.
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