A protective dyke from 100% reused sediments
By preparing material from maintenance dredging with selected additives, a protective dyke was constructed from 100% reused sediments.
The 700-m long and 6-m high primary dyke will protect the village from the water that flows into the flood control area.
The dredged material is delivered to a pontoon equipped with screens and a set of piston pumps able to push the relatively dry sediment approximately 600 m to the mixing plant.
After being mechanically dredged and transported by barges, the sediments are pumped ashore to the mixing plant. The dredged material is delivered to a pontoon equipped with screens and a set of piston pumps able to push the relatively dry sediment approximately 600 m to the mixing plant.
Laboratory testing followed by full-scale field trials demonstrated that the requirements in terms of stability and permeability could be achieved. The use of high-density pumps and a well-controlled processing plant eliminated the need for rehandling and intermediate storage of the solidified material.
All calculated safety factors are higher than the minimum design requirements.
Building with nature
In civil construction a widespread technique is to stabilise and solidify soft soils with additives such as lime, fly ash or cement. Jan De Nul Group came up with this ‘Building with Nature‘ solution to bring the dredged sediments ashore using high density pumps and to create engineered sediments from the soft not-suitable sediments by applying and optimising the stabilisation and solidification methodology. This technology has a lot of advantages:
- No transport water and associated environmental permitting for water treatment is necessary
- The dyke body can be built up with a high proportion of sediments, minimizing external supply and associated transport
- Workability, shear strength and bearing capacity of the sediments are quickly improved
- Permeability of the sediments is decreased because of physical and chemical binding
- Risk for internal slides is reduced as only one type of dyke material is used
- Internal settlements are reduced as no dewatering takes place and the solidified material gets its final shape in a couple of days to weeks.
The plan is governed by a Flemish government agency and since 2005 aims to combine flood defense with strengthening the river’s ecology through the creation of flood control areas.
The applied technique opens the door for a new approach in the application of fine sediments in large scale infrastructure works.
By effective selection of additive and application dose, unsuitable sediments are turned into useful construction material within days and with a minimum handling at a cost effect rate.
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