Contractors World

The online digital publication for the construction, demolition, mining and quarrying industries.

  September 2009
 
Buyers Guide
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REPORTS in this issue from:

  • Brazil
  • Hungary
  • Italy
  • Mongolia
  • Qatar
  • Singapore
  • UAE
  • United Kingdom

COMMENTS

     Precision Working

All the works are designed to very demanding specifications. The many kilometres of breakwaters have varying specifications depending on their location.

However, a typical cross section is, at sea bed level, approximately 133 m wide from toe extension on one side to extremity of armour rock on the other side. They rise to a maximum height of almost 21 m (of which 12 m is below the waterline). The breakwaters are profiled to a slope of 33º on the seaward side and 37º on the harbour side.

Typically, the seaward-side of the embankments comprise 3.0 m layer of selected quarry stone up to 500 kg; a 1.8 m layer of heavier 500 – 2,000 kg rock and a 3.2 m protective layer of antifers or acropods depending on position. At the foot, there is a large breakwater toe with 5 m extension.

On the harbour side, the composition is a 1.80 m layer of 500 kg quarry stone; a 1.15 m thick under layer of 100-500 kg quarry stone and an outer layer, 1.80 m thick, of armour rock (500 – 2000 kg).

127 t Hitachi Zaxis 850 uses articulating boom attachment to place antifers.
However, such is the variation in the dimensions, according to the water depth and where additional protection is required such as on the roundheads against possible ship impact, that there is nothing ‘typical’ about the project. This is why it has proved to be so challenging.

The challenges for the contractors were many and included the scale of the project, the time restraints, logistics, the many variations, very demanding quality control for materials and the construction tolerances (as little as ±0.2 m). To achieve this, they had to deploy the very latest technology, advanced computer aided systems, sophisticated, heavy-duty machines configured specially for the works and a team of highly skilled operators.      [cont]

Captions: Top Right
    Hitachi ZX870/3 carefully position boulders during final profiling.
Bottom Left:
   127 t Hitachi Zaxis 850 uses articulating boom attachment to place antifers.
Bottom:
    View across harbour showing extent of seawall constructions.

CW- Kilometers of seawalls under construction at Ras Laffan
 
 

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