The first step in constructing the buildings of Anse du Portier 3/3
Interview with Leonardo Pedrazzi
Leonardo Pedrazzi is the managing director of SOGEFON, one of the companies of the SOGEFON/FONDAMENTA group which is in charge of the foundations. The group has chosen to use five drilling rigs of 4 different models to complete its task. Leonardo Pedrazzi explains the great complexity of the drilling and piling work in progress.
Leonardo Pedrazzi, managing director of SOGEFON. Photo © SAM L’Anse du Portier
How is the deep drilling on this site different from others?
The conditions encountered below the surface of the land reclaimed from the sea are not identical from one zone to another of the offshore extension:
The varying nature of the materials to be dug through, the different depths that need to be reached, the pressure exerted on the piles by the surrounding materials, the conditions under which the piles are fixed in the very hard substratum (each pile must enter 40cm into it).
There are many parameters to manage and we sometimes encounter totally new situations. These are the reasons why we use different machines with specific capacities.
Why did you choose Bauer drilling rigs?
We have been working with this pile driver manufacturer for a long time. It is one of the world’s leading manufacturers in this sector.
But Bauer is more than just a supplier. They have been involved from the design phase for the dimensioning of the piles and then during the testing. Our combined expertise enabled us to develop the most appropriate solutions and to validate our method of operation. Their teams also provided assistance in the various stages of assembling the drilling rigs, as we use complementary accessories to optimize yields.
What situations do you encounter that require the use of four different models of pile drivers?
The number that defines the model indicates the rotational force developed to drill. For example, BG 45 means an excavation power of 45,000kg/metre.
In the excavation phase, we are faced with two problems: the friction that occurs when the drilling rig goes through the backfill and the density of this material. The strain is particularly high when inserting and removing the temporary tubes. In order to understand the situation, the machine can push the tube down to a depth of 25 metres.
Then the pressure is so great that it is impossible to work the casing further without increasing the power of the machine. In order to increase the rotation force of the machine, we have equipped it with a torque multiplier and a casing oscillator. These two devices increase the rotational force to 220,000 kg/metre. This is the power we need beyond a depth of 25 metres.
How do you limit the effect on the environment in these conditions?
Bauer has done a great deal of research and development over the past several years to offer effective alternatives in terms of reducing the environmental impact of its machines. If we take the case of the BG 55, it is the largest machine available in Europe. There are only two of them. It is the latest drilling rig created by Bauer. Its engine meets the extreme environmental specifications applied here. It is labelled “Ecopower”. It uses a specific fuel from the Shell brand, a GtL product with a low environmental impact. The engine is also more efficient in terms of reducing noise emissions. It complies with the conditions imposed on this site.
There is an even more powerful pile driver, the BG 72. But it does not meet the environmental specifications.
What does it mean to you to be involved in this operation?
This is the most important project that SOGEFON and FONDAMENTA have had to carry out so far in terms of the complexity of the technical situations to be solved and the duration of the work. This project has a huge impact. We had to rethink our companies to meet this challenge. About 40 people are working on this project alone today. It is also an opportunity to invest in state-of-the-art equipment such as the new BG 55. This broadens our range of skills, experience and expertise.