ABSTRACT
Tunnels are important structures, often in severe aggressive environments and they need high strength and high durability. The tunnel lining is made of precast reinforced concrete segments. This chapter considers the actual evolution of tunnelling using mechanical boring machines combined with a prefabricated lining in concrete. On the French side where the tunnels are partly in permeable ground the linings have to be watertight. In addition to the pressure exerted by the ground, the lining has to support the head of water, which approaches 100 m at mid channel. Concrete compressive strength tests were carried out at the prefabrication laboratory. The capacity of the prefabrication works depends on the necessary time to strip the casting segments. The prefabrication works includes: two lines of prefabrication of service tunnel segments with 45 moving molds on each line, and three lines of prefabrication of running tunnel segments with 45 moving molds on each line.
