Le Mégaron - Community, sports and cultural centre, Lancy (GE)

Le Mégaron - Community, sports and cultural centre, Lancy (GE) - civil engineering and earthworks


Ville de Lancy


  • Start of the works: November 2014
  • Duration of the civil works and earthworks: 18 months


Atelier d'architecture Brodbeck-Roulet SA

Total costs

Civil engineering : 2.2 mio EUR / Earthworks : 4.2 mio EUR

Project description

The objective of this project was the construction of a community centre with underground parking (218 places), and a civil protection shelter (500 places) over two basement levels.

Projects constraints

  • The project was constructed between an existing cut-and-cover motorway tunnel and an existing local road.
  • An existing tramway passed above the basement and was operational throughout the construction.


Excavation in two stages to allow the temporary diversion of the tramway.

  • During the first phase of the works, the tramway ran to the north of the project. Diaphragm walls and piles were installed from ground level to allow the street-level slab to be cast. This allowed the tramway to be diverted onto the new slab.
  • During the second phase of the works, the basement was completed using a top-down construction sequence through a moling hole in the street level slab. This enabled the tramway to remain operational, mitigating the inconveniences which are typically experienced during basement excavation.

Technical characteristic


  • Top-down excavation of 25,000m3 below the street level slab, on which the tramway operated throughout.
  • Excavation dimensions: 80 m x 40 m.
  • Excavation depth: 7m.

Diaphragm walls and basement columns

  • Diaphragm walls: 240 m long, 80 cm thick, 20 m deep, (area of the walls: 4 800 m2).
  • Installation of 70 concrete basement columns from the street level slab (30m length and 1 to 1.2m in diameter). 

Services provided 

  • Geotechnical surveying programme including pollution monitoring.
  • Feasibility studies including alternative options.
  • Scheme design.
  • Detailed design.
  • Tender documentation, comparison of offers, adjudication proposal.
  • Construction design.
  • Construction phase.

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