Advice

most suitable design and the conditions on the project location.

For the design of the breakwater, there has been executed a literature study on four different variants of a breakwater. The literature study can be found in the investigation report ‘Onderzoek naar de meest geschikte golfbreker voor de North Sea Wind Power Hub’, which is added to the projectmap.

The outcome of the literature study is, that for de conditions on the project location, the conventional breakwater with Xbloc elements in the armour layer, is the most suitable design.

the conditions  on the project location are:

design process of the breakwater

The conditions on the project location forms the basis for the design of the breakwater. First of all the height of the breakwater is calculated. With the requirement of a maximal wave height of 1 meter in the harbour, the transmissions coefficient could be determined. With the transmission coefficient the breakwater height is calculated on 20.5 meters. The extensive calculation can be found in the investigation report ‘Onderzoek naar de meest geschikte golfbreker voor de North Sea Wind Power Hub’.

After the calculation of the height of the breakwater, the size of the Xbloc elements is calculated. The front armour of the breakwater consist of Xbloc+ elements with a unit volume of 2.5 m³. the crest – and rear armour consist out of Xbloc element with a unit volume of 2.0 m³.

The filter layers of the breakwater are designed on the basis of two requirements:

Df15/Db85    < 4 à 5      geometric close filter for current

Mf50/Mb50  < 10 à 15   filter rule during wave attack.

The first filter layer is handed by the report ‘Guidelines for Xbloc concept design’. In this report the advised rubble stone grading is 300 – 1000 kg. The next layers are designed with the two requirements. The toe and the rubble stone in the rear armour are also designed with the ‘Guidelines for Xbloc concept design. In table 4.1 the structures of the different breakwater sections are presented.

calculation of the quantities and the total costs

The quantities of the breakwater are calculated, using the autocad drawing.

The total amount of construction materials are calculated in het investigation report  ‘Onderzoek naar de meest geschikte golfbreker voor de North Sea Wind Power Hub’. In this advice report, only the outcome of the calculations are given.

The total length of the breakwater construction is 734 meter. The surface of the breakwater is equal to 56092,28 m². the total amount of construction materials are given in table 4.3.

The total costs of the breakwater are calculated, using a graduation research from 1998, on the TU-Delft. In this graduation research the costs, for constructing a breakwater are given in Dutch guilders. To calculated the contemporary total costs of the breakwater, the total costs in Dutch guilders are converted to the total costs in euros. After that, the costs are multiplied with the ratio between the consumers price index of 1998 and 2018. The total costs of the breakwater construction are given in table 4.4 .