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Ghent - Moervaart

Early 2012 client Maritieme Toegang and Port of Ghent had awarded JV Besix-Ghent Dredging the contract to provide a scour protection at the Moervaart at Ghent.

Located at the utter downstream part of the canal 2 types of scour protection were placed over a total lenght of 900m alongside the northern quaywalls.
The purpose of the contract was to reinstate the scour as a result of shipping traffic, causing an imminent stability problem to the quaywall.
Second goal was to dredge the waterway.

TYPE 1 : rock-armour

Over a length of 450m by a width of 24m a (temporary) bottom protection at variable depths was carried out using stones. Firstly overdepths in front of the quaywall were filled out using steel slag material size 32/90 mm, covered by a layer of armour stones size 10/300kg and partly penetrated with colloïdal concrete.

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TYPE 2: Asphalt-matrasses

In the zone to be covered by asphalt-matrasses, the area had to be dredged in advance up to the solid sub-strata.
Before any matrass could be placed deeper areas were filled out with steel slag material size 32/90mm.
After levelling the full width of 20m was ready to be covered by asphalt-matrasses.  Alongside the toe of the channel the edge was protected with a layer of stone, with a width of 4m.
Sealing alongside the quaywall was established using colloïdal concrete.
Finally the main channel was again dredged to the required depth.  The dredged material, sand and silt, were disposed of at the Rodenhuize lagoon area.

 
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The matrasses, measuring 10 by 5m, were fabricated at the adjacent Moervaartquay area in a 120 by 18m working area. For that purpose the existing road had to be realigned locally.
In the working area itself a number of 20 sets of prefab formwork units have been erected.
After positioning the steel wire webbing each formwork was filled with a 30cm layer of asphalt.  The asphalt in each formwork was then leveled with a beam to achieve an even layer.
Using a specially-designed hydraulic lifting frame, designed by our subsidiary Deco nv, jointly with a 160 tons crane the matrasses were lifted from the quay and stockpiled onto a pontoon.
After positioning the matrasses were placed using the frame, equipped with a RTK-positioning system with an centimeter-accuracy on top of the steel slag foundation.  The seams between the individual matrasses were sealed using hydro-mortar.

 
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In all 21.300m³ of silt has been removed, 10.560m² of asphalt-matrasses have been placed, about 11.000m³ of steel slag have been used and 17.670 ton of armour stones have been incorporated.

 
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