Xbase®

DMC had developed a new toe concept which combines easy placement and high stability. One of the most critical factors involving the design of a breakwater is the design of the toe. Toe design can be even more complicated in depth limited seas which give unpredictable high hydraulic loads on the toe armour. Further more extreme swell conditions complicate the placement of the toe.

Download the paper: Xbase® development and application of a special concrete toe unit for extreme conditions presented at Coastal Structures Venice 2007.

Model tests

Model tests were performed to test the stability of the toe of a breakwater at Swakopmund Namibia. Depth limited wave conditions and extreme swell conditions were critical factors for the toe stability at that location. Different conventional toe options were tested and proved to be unstable, until the idea came up to remove one of the noses of the Xbloc®.

These modified Xblocs, the Xbase® units are not sensitive to overturning and are kept in position by friction between the unit and the rocky seabed. The first row exists of toe units which form an integral part of the armour layer and are interlocking with the next row of armour units. This toe proved to be very stable even under depth limited conditions.

Advantages of special toe unit

High hydraulic resistance
Low centre of gravity
Easy casting

Advantages compared to conventional rock toe

Higher stability
Lower use of material
Easier and faster to construct

Xbase® units can also be applied as first row of armour units on a quarry run filter layer for sandy seabeds. Project specific tests have been carried out on this solution at the Danish Hydraulic Institute.

Xbase crest elements

Xbase® units can also be applied as crest units on wide rubble mound crests. This solution was tested at CSIR, and will be applied for the breakwater rehabilitation at Port of Poti.

Xbase® crest units are easy to place. Due to their low cente of gravity they have a high hydraulic stability, and are not susceptible to rocking.