Apparatus for and a method of constructing a tunnel

An apparatus for constructing a tunnel;

• said apparatus comprising a drive shield composed of a plurality of elongate cutter plank members arranged side-by-side in parallel configuration and forming a cylindrical array extending generally around the axis of the tunnel in contact with the tunnel wall, a frame for supporting and guiding the cutter plank members for longitudinal displacement, means for causing relative displacement between the frame and the cutter plank members in the direction of the axis of the tunnel to effect driving of the tunnel, a movable rear shield positioned rearwardly of said frame and separate therefrom to support the tunnel wall rearwardly of the frame relative to the direction of tunnel driving, and movable relative to said frame for following advancement of the drive shield, said members of the drive shield having rear end portions which peripherally overlie, are in contact with and are guided by the rear shield regardless of the position of the rear shield relative to said frame and said cutter plank members of said drive shield.

In a tunnel driving apparatus which comprises a plurality of elongate drive members arranged side-by-side in parallel configuration and generally around the axis of the tunnel in supporting contact with the tunnel wall, a frame for supporting and guiding the drive members for longitudinal displacement and means for causing relative displacement between the frame and the members in the direction of advancement of the tunnel;

• the improvement comprising:
• a support structure disposed rearwardly of the frame relative to the direction of advancement of the tunnel, the support structure being movable with the frame to follow advancement thereof and facilitate sealing of said tunnel wall immediately behind said support structure and having an external support surface disposed radially outwardly from the tunnel axis relative to the frame so as to lie closely adjacent the tunnel wall and narrow tongue-like rear portions on the drive members which engage in an annular gap between the tunnel wall and the external support surface of the support structure so as to be guided by said surface, the rear portion and the remainder of each drive member having a continuous exterior surface engaging on the tunnel wall and the rear portion defining a recess on the opposite side to the exterior surface which receives the rear structure.