Hydraulic Stability
Xbloc® armouring has extensively been tested against wave loading in 2-D and 3-D models at several hydraulics laboratories including Deltares in the Netherlands and DHI in Denmark.
Results from these tests demonstrate that the Xbloc® possesses:
- Excellent hydraulic stability:
For concept design a Kd value [the stability coefficient in the Hudson formula] of 16 [trunk section] and 13 [head section] should be applied.
The stability coefficient of the Xbloc® is the same for breaking and non-breaking waves.
The design wave height may be exceeded by 25% without extraction of units.
- Automatic interlocking:
Xbloc® units naturally find a stable position on the slope
Self-repairing of the Xbloc® armour layer after damage is enhanced by automatic interlocking
The Xbloc® unit is simple to place as no specific orientation of the individual units is required
- Xbloc has been model tested on slopes varying between 3:4 (V:H) to 1:2. Although slopes of 3:4 and 2:3 are preferred to enhance interlocking, slopes of 1:2 may be required in earthquake zones and with soft subsoils. For a slope of 1:2 it is recommended to increase the unit size by a factor of 1.25. See also the Guidelines for Xbloc Concept Designs.
- Limited wave overtopping and refelection:
The highly porous armour layer minimises wave overtopping and reflection
Reflection and overtopping are strongly related, large roughness and high permeability, give low overtopping and low reflection. Read more on this topic at:
Wave reflection from coastal structures by B. Zanuttigh and J.W. van der Meer
