| 摘要 |
PROBLEM TO BE SOLVED: To prevent the change of volumes in chambers and surely prevent the fluctuation of heading soil pressure by operating the other auxiliary excavation means in the direction of increasing the volume in the chamber when one auxiliary excavation means is operated in the direction of decreasing the volume in the chamber. SOLUTION: An overbreaking devices 4, 4 of spokes 3a, 3c are gradually contracted as a cutter head 2 is rotated counterclockwise, and the overbreaking devices of spokes 3b, 3d are gradually extended. Then, the contraction amount of the overbreaking devices 4, 4 of the spokes 3a, 3c is made to substantially agree with the extension amount of the overbreaking device 4, 4 of the spokes 3b, 3d. When the cutter head 2 is further rotated, the spokes 3a, 3c comes in the direction of the minor axis of an elliptical cross section and the overbreaking devices 4, 4 are in the most construction state, the spokes 3b, 3d comes in the direction of the major axis of the elliptical cross section and the overbreaking devices 4, 4 are in the most extension state. |
