Tunnel excavation apparatus and tunnel excavation method

A tunnel excavating method for excavating tunnels in earth using a tunnel excavating apparatus, the tunnel excavating apparatus comprising:

• tubular shell bodies defining a cylindrical space inside and comprising a tubular excavating portion shell body, a tubular front shell body, and a tubular rear shell body disposed axially in series in this order from a leading end of the tunnel excavating apparatus towards a tail thereof, each shell body being shaped tubularly by coaxially arranged inner and outer cylindrical surfaces;
• an excavating mechanism disposed on a front face of the excavating portion shell body and having a rotationally driven annular cutting portion;
• and
• a propelling mechanism disposed within the front and rear shell bodies for propelling the excavating mechanism forward in an excavation advancing direction,
• wherein the propelling mechanism comprises:
• a projection mechanism that includes front radial jacks being arranged in the front shell body circumferentially of the front shell body, the front radial jacks being extendable to radially push out parts of the outer cylindrical surface of the front shell body to secure the front shell body against a tunnel being excavated, and rear radial jacks being arranged in the rear shell body circumferentially of the rear shell body, the rear radial jacks being extendable to radially push out parts of the outer cylinder surface of the rear shell body to secure the rear shell body against the tunnel being excavated;
• and
• an extension mechanism that includes front axial jacks being interposed between the excavating portion shell body and the front shell body to axially push the excavating portion shell body forward relative to the front shell body and rear axial jacks being interposed between the front shell body and the rear shell body to axially push the front shell body forward relative to the rear shell body, and
• further wherein the annular cutting portion is formed with an intake opening for introducing excavated dirt inside the excavating portion shell body, and the excavating portion shell body is formed with a discharge gap for discharging the introduced dirt out from the excavating portion shell body into the cylindrical space,
• said method comprising:
• a step for excavating ground in an annular shape by extending the front axial jacks and pushing the excavating mechanism forward while the front and rear radial jacks are extended and the front and rear shell bodies are secured against the tunnel being excavated;
• a step for contracting the front axial jacks and extending the rear axial jacks to push the front shell body forward while the front radial jacks are contracted to thereby free the front shell body, and the rear radial jacks are extended to thereby secure the rear shell body against the tunnel being excavated;
• a step for contracting the rear axial jacks to pull the rear shell body forward while the rear radial jacks are contracted to thereby free the rear shell body, and the front radial jacks are extended to thereby secure the front shell body against the tunnel being excavated;
• a following excavation step for excavating ground inside the shell bodies;
• and
• a step for introducing excavated dirt from the intake opening into the excavating portion shell body and discharging the introduced dirt out from the excavating portion shell body into the cylindrical space through the discharge gap.