EXTENSION OF LINE B OF THE RATP (PARIS SUBWAY) UP TO THE GARE DU NORD

The author describes the work involved in the extension of line B of the Paris Metro from the station at "Chatelet-les-Halles" to "Gare du Nord". He gives a geometrical and geological description of the project and presents the work involved in carrying out the different contracts. These works are being carried out on a very densely populated urban site under very unfavourable geological and hydrogeological conditions. Consequently, different methods of construction have been adopted to deal with the conditions encountered: large-span arches made up of prefabricated articulated segments, mechanical pre-cutting, stabilization by grouting.