Boring a Tunnel Under a Train Station Using Ground Freezing-Line 14-T03-Extension of a Subway Line in Paris (France)

摘要

A mixed brine-nitrogen artificial ground freezing method was used for the extension of Paris Metro Line 14. The project consisted in the excavation of a 26 m-long rectangular tunnel, carried out from two vertical shafts, with 122 freezing pipes. The tunnel intercepts three piles carrying an active commuter train station. The hydro-geotechnical context required the use of ground freezing as temporary support. The tunnel was divided in 6 sections, supported by heavy steel ribs and fiber shotcrete. During the works, several developments, such as the lifting of the station, water flows in the open frozen body shape and the thermal exchanges with the outside, added another level of complexity to the ground freezing handling.