ABSTRACT
The geopolitical conditions following the outbreak of war in Ukraine led to the decision by French authorities to urgently install a new Floating Storage Regasification Unit (FRSU) at the port of Le Havre, to secure gas supply both at national and European level. The connection of the FRSU to the existing gas transport network involved the design and construction of a 650 m long curved microtunnel to underpass the main navigation channel of the harbour at a depth of about 7 m under its bed. Two shafts were constructed at the microtunnel entry and exit points: secant piles and jet-grouting were executed for ground retention and waterproofing prior to excavation. The microtunnelling technology, profile and installation methods were selected to minimize environmental impact, mitigate construction risk and optimize schedule. Due to the constrained project timeline, it was essential to compress the design and construction phases by overlapping them, adapting the design and execution process as new geological data became available, in a close collaboration between the Main Client, Contractor and Engineers. As a result of this fruitful cooperation and of the technical solutions adopted to cope with the on-going evolution of the reference set of knowledge, works were successfully completed one month ahead of schedule, making it possible to anticipate the pipe laying and connection phases and to commission the system before the cold season.
