PURPOSE: To increase the amount of overcut as much as possible and facilitate earth removal work by housing a drilling bucket in an outer peripheral part of a cutter head and enabling a chamber to be opened for a bucket casing.
CONSTITUTION: When a ground is excavated based on size expansion, generally, a drilling bucket 34 is housed in a cutter head 14 at first and then excavated in this state where the bucket is housed and excavated only by the dimension of the width of the bucket 34. A gripper 58 is operated so as to project and bite into the natural ground, thereby fixedly holing a shield main body 12. After that, the cuter head 14 is rotation-driven, thereby expanding the size of a bucket cylinder 48 and driving the cylinder. During this operation, the drilling bucket 34 lifts up the tip from the outer peripheral surface of the cutter head 14. As a result, the blade edge of the bucket 34 bites into the natural ground by the portion erected from the outer peripheral surface of the cutter head 14 so that expansion drilling may be carried out. The excavated earth and sand are ladled with the bucket 34 and taken into a shield chamber 26 by way of a bucket storage opening and removed. Bucket width forward motion and expansion drilling are repeated in this manner.
UCHIDA TAIZO
FUJII YOSHIBUMI
HARA KIYOSHI
MINAMI YOSHITO
TAKENAKA DOBOKU
KOMATSU MFG CO LTD