Apparatus and method for large tunnel excavation in hard rock

Claim 1

An earth drilling machine for excavating tunnels comprising an elongated hollow hull having a frontal portion with cross section equal to the cross section of the final tunnel prior to installation of final tunnel wall lining and a rearward portion reduced in cross-section relative to the frontal portion, a rock melting kerf penetrator affixed to and projecting longitudinally forward of the front end of the hull and having a peripheral shape similar in configuration with the front portion of the hull, a hull closure face plate affixed to the interior of the hull at the front end thereof, a plurality of rod-shaped thermal stress fracturing penetrators supported in said hull closure face plate with their direction of elongation parallel to the direction of elongation of the hull, and projecting forward of the front surface of the hull closure plate, rock debris removal means supported in a peripheral portion of the hull closure plate, a nuclear reactor supported within the hull of the machine, heat pipe heat conduction means coupled to the reactor core at one end and to the kerf melter and thermal stress fracturing penetrators at the other end; the rear end of the kerf melting penetrator skirt and the front end of the hull being smoothly joined together, thermal cooling means coupled to the front end of the hull whereby said front end of the hull supports the molten rock against the excavation walls and simultaneously solidifies said molten rock into a tunnel wall initial supporting liner.