| 摘要 |
PROBLEM TO BE SOLVED: To surely and efficiently remove obstructions such as a sheet pile and a pile existing on a planned tunnel line. SOLUTION: A fixing head part 7 for projecting a soil excavation bit 27 on the edge of a center shaft 2 and a movable head part 8 for projecting an obstruction cutting bit 16 capable of frequenting for the fixing head part 7 are disposed, and a plurality of rotation arms 6 are radially projected from the circumference of the center shaft 2. A row of a soil excavation bit 11 and three rows of obstruction cutting bits 12 of longer projection length than the soil excavation bit 11 are longitudinally fixed on the rotation arms, normally the rotation arms 6 are not rotated, the soil excavation bit 11 is in a forward state, and excavation of the ground is performed while a cutter head is rotated by the excavation bits 11, 27 of the movable head part 8 and the rotation arm 6. During cutting of obstructions, the cutting bit 16 of the movable head part 8 is projected from the fixing head part 7, and the rotation arms 6 are rotated to cut and remove the obstruction by the cutting bits 12, 16. |
