As part of the Monaco offshore extension project, Bouygues Travaux Publics is in charge of design & build a maritime infrastructure as the first step of the six-hectare expansion of the city into the sea. This maritime infrastructure consists of a fill enclosed by a band of 18 trapezoid reinforced concrete caissons and will serve as base for construction of the new eco-neighborhood in Monaco. The caisson precasting area is located in the port of Marseilles, using a dedicated floating dock.

The paper focuses on some of the problems which had to be solved, among which :

  • The optimization of promenade level, searching for :

    • a compromise between architectural point of view and safety related to storm wave overtopping, taking into account sea level rise and correlations between extreme waves and water levels;

    • minimal reflection coefficient for vertical concrete caissons, so as to minimize impact on existing Port Hercules wave disturbance.

  • Caissons and rubble mound foundation stability related to waves and seism, including extra seismic forces due to buildings considering the high reclamation height (up to 40 m) and the immediate proximity of building foundations.

  • The presence of a small craft harbor, whose location was fixed for urbanistic reasons, which requested optimizations in detail of anti-overtopping devices as much as possible integrated in the urban context, including a low crested "swimming pool caisson breakwater"

  • Design and build of a dedicated floating yard

Design has required a multidisciplinary approach (urbanists, landscapers, architects, marine infrastructure engineering, biologists), with unconventional infrastructure solutions due to the very specific context (direct exposure to offshore waves, proximity of sensitive port and natural areas, seismic hazard associated with buildings very close to 25 m high concrete caissons …).

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