Abstract: A propelling apparatus includes a plurality of propellant cylinders series-connected to each other to be propelled by receiving a pushing force from behind, joints for series-connecting the propellant cylinders, a propellant head connected to a forward-most end of the propellant cylinders to be pressed into the earth, a leader member constituting a leading end of the propellant head, the leader member being rotatable about an axis of the propellant head by receiving a driving force from a driving device. An inclined pressure-receiving face is formed at a forward portion of the leader member for receiving an earth pressure in association with the underground propelling movement of the propellant head and steering the propellant head toward the direction of application of the earth pressure to the pressure-receiving face. The joint includes a flexible joint which is pivotally flexible about a transverse axis extending normal to an axis of the propellant cylinder.

Abstract: An underground propelling method uses a propellant apparatus including a propellant head having a pressure receiving face portion inclined relative to an axis of the head and a plurality of propellant cylinders flexibly and pivotally connected in series to a rear end of the propellant head. The propellant apparatus is propelled under the ground by applying a thrust to the propellant apparatus from behind. Each propellant cylinder of the apparatus is pivotal about a single pivot axis thereof alone. The apparatus is propelled with the pressure receiving face portion thereof being oriented along a pivotal direction of the propellant cylinder about the pivot axis.