|Owner||S.A.M. L’ANSE DU PORTIER|
|Main Contractor||Bouygues Travaux Publics|
|Duration of work||2019-2020|
The construction of the buildings required the preliminary consolidation of the seabed soils. In fact, part of the marine sediments on which the works are carried out can be subject to the phenomenon of liquefaction in case of earthquake.
For this purpose, the following two types of intervention were adopted:
- Soil compaction by vibro-replacement columns: this type of intervention, which reduces the voids index, densifying the soil increase its resistance to seismic cycling stresses that could induce liquefaction.
- Construction of a structural cellular grid, made up of elements of soil treated with jet grouting technology: with this intervention, the pore pressures remain confined within the cells which, characterised by their own structural resistance, prevent the increment of the pore pressure avoiding to reach the liquefaction limits of marine sediments.
The first type of intervention was not applicable in the area closest to the original coastline due to the presence of a buried rocky reef.
The jet grouting solution,on the contrary, was adequate in this area as well. The structural cellular lattice was constructed using pseudo-elliptical elements using double fluid jet grouting technology.
The intervention covered a strip of coastline approximately 250 metres long and 30 metres wide, located near the existing breakwater wall. In the north-eastern area of the platform, where the soil treatment was close to the coastline of the Larvotto marine reserve, circular jet grouting columns were constructed using single fluid technology in order to prevent the pollution of the seabed potentially induced by the execution of the high energy double fluid treatment.
The entire process of creating the anti-liquefaction cells involved the execution of more than 1,330 jet grouting columns, for a total of over 24,500 m3 of treated soil.
Thanks to this consolidation work, it will be possible to build the foundation piles for the district’s structures and minimise the risks of soil liquefaction and buildings damage in the event of an earthquake.