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Structure Scour Mitigation

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Subsea structures placed on sandy soils can be susceptible to a type of erosion called
scour. Especially at sites with tidal currents, a significant section of the soil around a structure can be removed, due to the effect of the foundation on the local flow pattern and velocities.

The main disadvantages associated with scour are:
· Reduction of the stability of the foundation
· Variation in orientation with resulting stress on connected flowline or cables
· Variation in the natural frequency of the subsea structure

Subcon has a large track record in scour mitigation projects. Apart from regular articulating concrete mattresses, Subcon offers a range of engineered solution to prevent scour. Subcon’s range of fronded matts offer an active solution to remediating and protecting against scour in transient seabed scenarios, or Coastmatts backed by geotextile, actively consolidating the soil underneath while preventing any sediment migration paths. Grouted scour skirts provide a fast to install, in-situ grouted mitigation method that can be integrated into the mud-mad of a structure.


The main method to prevent scour is to stabilize a filter layer by covering it with rocks or concrete weights in the form of articulation mattresses.

Subcon’s coastmats consist of a woven polypropylene base layer with the concrete blocks casted directly onto it.

Articulating mattresses take a large deck space on a vessel for installation and need a relatively large crane capacity to be installed.

Scour skirt take minimal deck space on the installation vessel and can be easily moved in position by ROV or diver.

The buoyant fronds in frond mats dissipate the wave and current energy close to the seabed.

The lower velocities have a lower transport capacity as a result, therefore collecting sediment from its surroundings. As such, these can be used to remediate existing areas of scour.

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