Abstract: A shield tunneling machine has a shield body and a cutter head rotatably provided at the forward end of the shield body in the excavation direction. Abrasive jet spray nozzles for spraying abrasive jet water are movably provided on the cutter head. Obstacles encountered during excavation can be broken efficiently with high cutting quality by properly controlling the movable abrasive jet spray nozzles according to the size and configuration of each particular obstacle.

Abstract: A shield tunneling machine has a shield body and a cutter head rotatably provided at the forward end of the shield body in the excavation direction. Abrasive jet spray nozzles for spraying abrasive jet water are movably provided on the cutter head. Obstacles encountered during excavation can be broken efficiently with high cutting quality by properly controlling the movable abrasive jet spray nozzles according to the size and configuration of each particular obstacle.

Abstract: An excavator including a center shaft rotatably provided in a shield body in concentric relation to an outer cone. An inner cone for crushing excavated materials in cooperation with the outer cone is eccentrically provided on the center shaft. A cutter head provided in front of the inner cone is mounted on the center shaft. An internally-toothed gear is secured to the inner cone in concentric relation to the center shaft. A plurality of externally-toothed gears rotated by driving motors whose rotational speed and torque are variably controllable are internally meshed with the internally-toothed gear. Rotation of the externally-toothed gears causes the center shaft to rotate through the inner cone. A plurality of water jet spray nozzles are provided on the cutter head. The spray pressure is switched between high pressure and low pressure.