Abstract: Apparatus for tunnelling through soil, in which a cutting head is rotatably mounted on a housing and atmospherically sealed from the housing. A muck ring is located in the housing to collect loose soil through an opening into the chamber of the muck ring and the opening is closable to maintain a pre-set earth pressure in the cutting head.

Abstract: A device for positioning segments to line a tunnel wall. An axially rotatable drive shaft carries at one end of an articulated arm with pivotably connected upper and lower arm members. A jack interconnects the two arms intermediate their ends. The upper arm member is pivotably connected at its free end to the drive shaft on an axis normal both to the shaft and to the upper arm member, and the arm lies in a plane through the normal axis. Preferably a shoe is detachably connectable to the lower arm member and to a segment to be positioned against the tunnel wall.

Abstract: A rib expander, for use with tunnelling apparatus, in which a plurality of arcuate segmental members form a ring, at least two of the members being separable longitudinally to expand the ring. The ring is mounted to provide pivotal movement about a vertical circumferential axis of the ring as well as transverse movement in the plane of the ring and movement along the normal axis of the ring.

Abstract: An apparatus for tunnelling through soil, of the type in which a conical cutting head is rotatably mounted coaxially on a cylindrical housing and a toothed cutter bar is mounted radially on the cutting head adjacent an aperture in the cutting head. A flood door is mounted on the cutting head and is movable to open or close the aperture. Preferably a pair of doors are individually operable to converge or diverge in varying the size of the aperture. The cutter bar may be movable radially outward beyond the circumference of the cutting head to describe an arcuate path eccentric to the face of the cutting head.