Within Grand Paris Metro project (extension of the line 14 South), SWS has supported the JV Léon Grosse / Soletanche-Bachy in designing a complex set of temporary works. A Few days ago the first shaft at Maison Blanche Station has been completed. More in detail SWS has been appointed for the conception of the shafts required for the demolition of the ancient railway tunnel called “Petite Ceinture”, that is currently interfering with the construction of the diaphragm walls of the new metro station located at Maison Blanche in the 13th district.
The “Petite Ceinture” is an historical Parisian railway constructed in the second part of the XIX century with some underground tracks. The existing tunnel of Petite Ceinture is a masonry tunnel, of about 5 x 10 m, with few meters of overburden. In the area of the new Maison Blanche station, the ancient railway passes under a +14 floors residential building, a 4-lane route (Avenue d’Italie) and over the existing tunnel of metro 7.
Hystorical drawing of the masonry tunnel
The complex urban and underground pattern, the poor quality of the overburden ground, the large presence of underground utilities and a limited site construction area were the main constrains that SWS had to face in the design.
In order to successfully handle these conditions, SWS has developed a multistage process. The final project provides:
- Construction of shield walls inside the Petite Ceinture tunnel;
- Excavation of the shafts by traditional method (puits blindé);
- Demolition of the tunnel;
- Shafts closure by back-filling of the Petite Ceinture.
Schematic of the implemented construction sequence