Summaries
Steering the 'Cardium'
Some aspects of the 'Cardium' shifting system
have already been discussed in the previous
publication. A steering process comprising
three orders led to controlled manoeuvres with
eight winches at the corners of the pontoon.
But how is the conveyance of the steering
orders achieved? The control mechanism,
consisting of six blocks is decribed in detail in
this article. Block 1 comprises a delay-action
filter which prevents the occurence of lurching.
Block 2 converts the three orders into eight
steering signals and block 3 limits the power of
the steering equipment. Blocks 4 and 5 re-dis
tribute the tension in the cables, and block 6
keeps a check on the anchor pattern.
The blocks also exchange steering signals
mutually. A forecaster provides the skipper
with information on the effects of his steering
movements.
The execution of the foundation bed in the
Hammen
The actual placing of the foundation bed for
the Oosterschelde barrier in the Hammen
channel was started on in November 1982. It
was very quickly apparent that the working
cycle would have to be altered and that
adjustments would also have to be made in the
apparatus. Teething troubles were finally
overcome by April 1983. From that time on a
pier location was prepared nearly every week.
The quality of the foundation-bed is satisfactory
as regards filter composition and flatness.
Correction needed to be made in one spot only
with the assistance of a tile-mat. Sufficient
compaction is achieved although this demands
the utmost of the vibration equipment.
The filter quality in the space between the
foundation mattresses just meets the standards.
Problems concerning the edging of the
protective revetment
This article describes the study made by a
workgroup on the scouring of the edges of the
protective revetment, and the research which it
has carried out. It had to make recommendations
as to which measures should be taken against
landslides as well as against sand liquefication
and to indicate where these should be taken.
Further it was to predict the amount of mobili
sation time necessary between the establish
ment of scouring and the actual counter
measures. There was a report in the previous
publication on the final results. This time the
study itself is dealt with in greater detail.
Marine cultures in the mouth of the
Oosterschelde
Since 1981 research has been carried out into
shellfisch cultures, fisch farming and algae
cultivation in the mouth of the Oosterschelde.
Research is being carried out into possible
forms of renewal and in how far the
Oosterschelde barrier, the harbours,
construction docks and other facilities involved
in the project can be used for for this purpose.
Loads, located at one point on the sill-beams
The sill-beams which form the supporting
frames of the wet cross-section in the
Oosterschelde Barrier, are subject to hydraulic
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