Diamond Award 2020

The work commissioned to RE-CORTA consisted of the formation of 57 windows in 3 of the 7 submerged precast concrete caissons, to facilitate the flow of water inside them and, in this way, dissipate the energy caused by the waves.
The unit dimensions of each of the windows were 5.20×0.83×0.40 m (16×0.83×0.40 ft).
Each cut block would weigh 4.3 tons.

The work was to be carried out in two types of cells:

• 27 cells of 3.5 meters in diameter (2 windows per cell)
• 3 cells of 1.68 m wide (1 window per cell)

Already during the study phase, the aim was to differentiate the company from the competition: from the very beginning, the objective was to carry out the work without the need for divers.
Consequently, the following tasks were chosen to achieve the opening of each window:

• Perforation.
  8 perforations Ø120 mm, for the lower horizontal cut, 2 perforations Ø50 mm in the upper corners (for thread passage), and 1 perforation Ø120 mm for the strobing.
• Cutting.
  1 horizontal cut of 83×40 cm in the upper area, and 2 vertical cuts of 520×40 cm on the sides.

To achieve this goal, the solution was to design structures that were as light and rigid as possible to allow personnel to work above the water level and, at the same time, to support the hydraulic cutting and drilling equipment so that it could be perfectly positioned to perform its task, including the lower cut of the window (deepest area) by means of secant drills.
Layher’s allaround multidirectional scaffolding system was the best choice.

Two types of structures were designed (for each type of cell), which could be positioned and removed with a crane.
The first one would be used to make the bottom cut of each window by means of the secant perforations.
The hydraulic drills were installed in the lower part of the structure, while the hydraulic units, control equipment and personnel were located on the platform at the top of the structure, practically at the same level as the upper level of the caisson.

The second structure, which had platforms on three levels, would be used for the rest of the tasks.
The highest level would house the hydraulic units, control equipment and personnel.
From the intermediate level, the perforations in the upper corners of the window and for strobing would be drilled.
The lowest level would only be accessed, taking advantage of low tide, to thread the diamond wire to make the vertical cuts (operating the machines from the highest level).

Drilling sequence for window undercuts in 4 phases To make each of the undercuts in each window, it was necessary to drill 8 holes.
Using 4 drilling rigs, the position of the rigs was changed only 4 times to make the cuts in the two windows of the cell.

Sequence of auxiliary perforations and cuts Once structure 2 was in place, the perforations were made for the thread passage in the upper corners of the two windows, with a Ø50 mm crown, and the perforation for the strobing, at 1.20 m from the top, Ø120 mm.
Then the 2 upper horizontal cuts were made with wire (one for each opening).
Then the first of the vertical cuts was made in each window and, finally, the last vertical cut was made in each case, after the cut block had been strobed with an auto crane.

Inclement weather conditions have also been a handicap during the time the works have been carried out.
To combat the rainy days, custom-made tarpaulins were designed for the structures built.
Wind speed and waves were measured by means of a buoy located in a nearby area.
Due to the values obtained, it was necessary to interrupt the work on several occasions. Even so, the work was completed on time.