France: special foundation works on the SEMAPA M10VP File F project

We look back on a technical site which called for our specialist expertise.

17.07.2020Project

The future 1,000m² slab, known as the M10VP block, is the last section of the ambitious SEMAPA project for which SNCF is main contractor. The project, which began in the 1990s, involves covering the railway tracks between Gare d’Austerlitz and Pont Masséna. Entrusted in 2019 to a consortium including Soletanche Bachy, this final stage will include the creation of two new pile lines (J1 and F), made up of foundation barrettes, topped with footings and curtains, supporting beams crossing the railway hub on either side. The future slab, due for delivery at the end of 2023, will provide space to construct a new district.

Almost a year after the bars for line J1, the last special foundation works on the M10 project are starting on line F.

The platform available for creating the future pile line F is located between a heavy protective curtain resting on piles (bored by Soletanche Bachy Fondations Spéciales in 2019) and a tremie pipe, not exceeding 4m in width.

The tremie pipe was created in around 1928, which is gradually sinking under the railway platform to connect the Gare d’Austerlitz to the technical maintenance centre via two railway lines.

The 4m width available does not allow use of the equipment necessary for the barrette works (HC05 Hydrofraise® and handling crane). Thus, a widening of the platform was necessary, by provisionally blocking one of the channels sinking into the tremie pipe. The expansion was carried out using two techniques:

  • installation of an L-shaped wall,
  • construction of a slab supported by micropiles.

 

Barettes/ micropieux / micropiles / railway

 

The 71 micropiles, which are 15m deep, were installed from November 2019 to January 2020. They are type II micropiles, bored using a lost tool.

Following creation of the slab supported on micropiles, Soletanche Bachy Fondations Spéciales returned to the project to take a core sample from remains 5m deep located at the future site of the barrettes.

Installation work on the bar site was able to resume at the end of lockdown, with a first excavation taking place on 25 May.

 

Find the article TRAVAUX dedicated to this project.