Xbloc

An Xbloc is an interlocking concrete block (or "armour unit") designed to protect shores, harbour walls, seawalls, breakwaters and other coastal structures from the direct impact of incoming waves. The Xbloc model has been designed and developed by Delta Marine Consultants since 2001 and has been subjected to extensive research by several universities.

Concrete armour units are generally applied in breakwaters and shore protections. The units are placed in a single layer as the outer layer of the coastal structure. This outer layer is called the armour layer. The function of the armour layer in these structures is twofold. Firstly, it shall protect the finer material below the armour layer against severe wave action. Secondly, the armour layer shall dissipate the wave energy in order to reduce the wave run-up, overtopping and reflection. These two functions require a heavy, but porous armour.

Common factors to apply single layer concrete armour units are:

Also compared to older concrete armour units, as e.g. Tetrapod which are normally placed in double layer as for rock protection, modern single layer armour units involve significantly less concrete. Therefore, less construction material (cement, gravel) is required, reducing costs and also the carbon footprint of coastal protection works.

Concrete blocks used for the same purpose are listed amongst others in [1]. Like Xbloc, most of these blocks are commercial developments and patented. As such Xblocs are not produced by the patent holder, but are fabricated and installed by a contractor who in return pays a license fee. Such an agreement involves certain technical support activities to ensure the correct application of the protection system.

The Xbloc armour unit derives its hydraulic stability from its self-weight and by interlocking with surrounding units. Due to the highly porous armour layer (layer porosity of almost 60%) constructed with Xbloc units, the energy of the incoming waves will be largely absorbed. The Xbloc armour layer is therefore able to protect the rock in the under layer from erosion due to waves. Besides empirical formulae derived from physical model testing, the interaction between breakwater elements (submerged or emerged) and waves as well as the filtration of the fluid into the porous breakwater has been investigated amongst others by MEDUS, based on RANS equations coupled with a RNG turbulence model.

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