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Monceau-sur-Sambre - Weir

At Monceau-sur-Sambre Ghent Dredging carried out repair works at the downstream side of the weir and its scour-bed.

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The reported damage:

  • Rupture of the concrete bottom of the weir. As a result a 3 m deep scour-hole had developed. Along approx. 100m about 800m3 of rip-rap was placed to fill the hole.
  • Damage to both banks, consisting of subsidence of both banks.
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The location where the damage has occurred made a hard job to repair with:

  • Stricted access by land
  • Shallow water and limited headroom
  • Huge variations in both waterlevels and flows
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The job in hand consisted of:

  • Dredging downstream of the scour area
  • Removal of the concrete floor around the scour area
  • Filling out the scour area, using armour stones 300/1000 kg on top of a bottom layer of rip-rap 0/180 mm.
  • Penetration with colloidal concrete of the armour stones
  • Reinstating both banks, using armour stones, concrete and cut-stones.
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To carry out the job a self-propelled pontoon, mounted with a 20T digger, equipped with DGPS was used.

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The pontoon had to be modified several times to be able to carry out the various stages of the contract, i.e. dredging, rock dumping, incorporating concrete and fixing both banks.

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Some quantities:

  • 2.300T armour stones
  • 400m³ colloïdal concrete
  • 300m bank reinstatement
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