xbloc-design-guidelines-2011.pdf (2.2MB)

7 Guidelines for Xbloc Concept Designs
4 Front Armour Design
The required armour size is typically determined by the design wave height as
described in Section 4.1. Depending on the local conditions, there are however
phenomena that may require the application of a larger unit than based on the
equation in Section 4.1. These phenomena are described in Section 4.2.
4.1 Required Xbloc size
For the design of typical cross sections of breakwaters and shore protections, the
required Xbloc size depends on the design wave height and can be determined with the
following formula:
V =
Where:
7
3
H s
2.77 x Δ
V Xbloc volume [m 3 ]
H s
Design significant wave height 1) 2) [m]
Δ Relative concrete density (ρ c
- ρ w
) /ρ w
[-]
ρ w
Mass density of seawater [kg/m 3 ]
ρ c
Mass density of concrete 3) [kg/m 3 ]
1)
DMC does not recommend a reduction for oblique waves without physical model tests.
2)
If H mo
is higher than H s
, H mo
shall be applied.
3)
DMC does not recommend the use of concrete densities outside the range of 2350-2500kg/m 3 .
This formula in fact gives the same results as the Hudson Formula for an armour slope
steepness of 3V:4H and a K d
factor of 16. Please note that for Xbloc on a milder slope,
the required unit weight is not reduced.
Xblocs are typically applied on an armour slope steepness between 3V:4H and 2V:3H.