Summaries
Planning of the works to be executed
At the preparation of the works in the
Oosterschelde a network planning has been
used. When the construction is in progress a
system of 'line balancing' will be utilized. Herein
both technical and spacial interdependencies can
be expressed. From some figures can be learned
that in actual fact a time/space diagram is given
for the route of service-vessels.
The foundation bed
The piers of the barrier will be positioned on a
foundation mattress. This mattress will serve as
a filter for the underlying Oosterschelde sand.
From top to bottom it consists of layers of coarse
gravel, fine gravel and sand. The various layers
are interlined with nylon cloth. Steelwire
baskets prevent shifting of the filter material
when the mattress is in an oblique position.
Steel pins fixed and locked through the entire
thickness of the mat strengthen the structure of
the mattress. This paper also describes the
set-up of the factory that is to produce the mat
tresses.
'Cardium'; a pontoon to lay foundation
mattresses
The foundation bed forthe piers of the barrier
will consist of a packed filter. A special pontoon
has been designed to lay the foundation
mattresses. The surface area of each mattress
is 42 x 200 m. This pontoon first levels the
sea bed, then lays the mattress to subsequently
compact them with the aid of vibrating plates. In
those places where, as a protective measure, a
second mattress is laid on top of the first one,
the sand that may have accumulated on the first
mattress will be sucked away by the 'Cardium'
before the second mattress can be placed.
Some delay occurred during the invitations for
tender for the building of the 'Cardium'. To make
up for the loss in time the work with the vessel
must be accelerated.
Compaction of the sandy sub-soil in the axis of
the barrier
If the sandy sub-soil has a porosity of more than
40 per cent, then a real danger exists that the
bottom wil be weakened when cyclic loads are
being exerted on the barrier in the
Oosterschelde.
In all places with high porosity the bed must
be artificially compacted through vibration.
Preparative to the design of the so-called
'compaction vessel' tests have been made
to determine the optimal mutual distance
between the vibrators and the engine power
needed for operation. Not only the degree of
compaction but also its homogeneity were
considered. To obtain accurate numerical data
laboratory and field tests have been made.
Ultimately the mutual distance between the
resonators was fixed at 6,5 m. This resonator
is equiped with two vibrators. Each resonator
has a diameter of 2.10 m.
Meteorological forecasts for the works in the
Oosterschelde
In September 1980 the Hydro Meteo Centre will
be put into operation for the benefit of the
Oosterschelde works. All hydraulic and
meteorologie information relevant to the works
under operation will be gathered and processec
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