| 摘要 |
PURPOSE:To easily excavate an elliptic tunnel by providing a cutter face so that either one of upper and lower peripheries of a cutter is protruded and inclined in the excavating direction. CONSTITUTION:A cutter 11 is fitted to a circular plate 15 in a shield main body 14 via many arms 16. The circular plate 15 is fixed to a circular projection section 21 provided on the inner periphery of the shield main body 14 via many jacks 17. The face of the cutter 11 is inclined by the extension of the jacks 17 in response to the aspect ratio of the cross section of an excavated tunnel 12. An elliptic tunnel can be excavated accordingly. |
