The purpose of the Colline des Mathurins project in Bagneux (Hauts-de-Seine) is to transform a historically introverted location into a sustainable neighbourhood open to the city, ready to play a pivotal role in connecting the city centre and the southern neighbourhoods. The real-estate project involves developing the site by building 300,000m² of floor area, including renovation of 20,000m² of existing buildings.
This project concerns a 15.6ha site, a unique property that was previously home to Thomson-Thalès for 50 years, then the French General Armament Directorate between 2007 and 2016.
This is the background against which Sefi-Intrafor (head of consortium) signed up to rehabilitate the site. It is an exceptionally high-volume site: 170 linear km of drilling, 250,000m3 of backfill grouting, and 10,500m3 of compensation grouting are planned to secure this site, previously undermined by deep mining of shallow, intermediate, and deep gypsum strata.
Though the works are conventional, and of no particular technical difficulty, the complexity of this structure lies in successfully managing the phasing of the different packages (drilling, backfilling, compaction, compensation) and working around other ongoing works (demolition, earthworks). This requires the teams to very carefully and rigorously manage every package.
In spite of the impressive figures and challenges involved, the project is ahead of schedule. 90% of phase 1 is already complete and phase 2 will get underway 2 months ahead of schedule.
How was this efficiency achieved? It’s all down to the employees and equipment involved (4 drilling workshops instead of the 2 planned and the new grouting plant) as well as the good understanding between the teams from Sefi-Intrafor and Soletanche Bachy.
Currently, the site is keeping over thirty staff busy, featuring four drilling workshops per shift, a continuous backfill and compaction grout production plant, and a compression grouting plant.
Client: BNP Paribas Résidentiel, LBO France
Consortium members: Sefi-Intrafor, Soletanche Bachy