Placement

Placement of Xbloc units is straight forward. The units are placed with random orientations on predefined coordinates which are provided by DMC. This placement grid is a half brick bond so each unit is placed in between 2 units in the row below and covered by 2 units in the above lying row. This way Xblocs get their stability from interlocking with the surrounding units on the slope.

It is therefore important that the blocks on the slope are secured by the 2 units placed above and furthermore the units should be in contact with the under layer. There are no restrictions on the orientation of the units, but it is important that the units are placed with randomly varying orientations. If multiple units are placed in regular orientations, this can lead to an increased placement density and therefore to the use of more units than necessary.

Before the start of the placement process, DMC provides the design coordinates for the units on the basis of the construction drawings. DMC provides the Contractor with instructions prior to the start of the placement followed by a trial placement on land. Placement will start and DMC will provide guidance throughout the construction period.

Placement rates

Based on several projects the achievable placement rate of Xbloc armour units lies between 8-25 units/hour. The Xbloc units can be placed by an excavator or a crawler crane. Highest placement rates are achieved with the use of an hydraulic excavator equipped with a clamp or a quick release hook.

Underwater placement

For underwater placement the guidance of divers is often used or placement with an echoscope, which is attached to the excavator or crawler crane. With the echoscope the operator is able to see the unit in the sling with its surrounding units and therefore it facilitates easier placement under water.