Tunnel construction under river - involves staged side walls for caissons lowered onto revetting walls

摘要

Opposite resetting walls (4), spaced at prescribed tunnel width, are constructed into the bottom of the bed (3), to initiate construction of tunnels (1) under waterways (2), esp. rivers. A caisson (5) is lowered onto both, at the tunnel periphery, and cleared of water by increased air pressure. A tunnel roof section (7) is made in this area (6) and anchored to the walls. The caisson is moved forward for the construction of the next section. The working area (8) is excavated below the tunnel roof, and a tunnel floor (10) and walls (11) are constructed, forming a tube, and connected to the roof.