| 摘要 |
PROBLEM TO BE SOLVED: To drill an elliptical cross-section by providing a plural number of spoke-type cutter heads to extend and contract in the radial direction and a shield main body of roughly the same cross-section of a drilling cross-section. SOLUTION: A modified cross-section shield excavator has a shield main body 1 of a cross section roughly similar to a tunnel to drill and a cutter head 2 consisting of flexible spokes 12A-12C. At the time of construction, a tunnel of an optional modified cross-section is drilled by increasing and decreasing a drilling diameter by extending and contracting the spokes 12A-12C by a drilling cross-section control device in accordance with a signal of a cutter rotational position meter to detect a rotational position of the head 2. At this time, a foundation which cannot be drilled by non-drilling parts 15A-15C of each of the spokes 12A-12C is drilled by fixed drilling parts 14a-14c and/or forward and backward drilling parts 16a-16c of other spokes 12A-12C by slipping positions of flexible non drilling parts 15A-15C. Consequently, it is possible to drill an optional modified cross-section tunnel by one cutter head and to drill it in simple structure. |
