| 摘要 |
PURPOSE: To lessen the excavatingload, by enlarging the periphery of an advanced guide tunnel by a first cutter face to form an elliptic shape and further, opening it by a second cutter face to make a similar large diameter tunnel. CONSTITUTION: In the first stage enlarging cutting part B of a reaming machine, the first gripper 28 of the main beam 32 inserted in an advanced guide tunnel 1 is extended and after having pushed the tunnel wall, the front support leg 18 is retracted and the cutter head 22 is rotated and further, the periphery of the advanced tunnel 1 is excavated to form the first stage elliptic tunnel shape while pulling forward the first main beam 32. In parallel with the first stage enlarging cutting part B, the second gripper 42 fitted to the double-pipe structural and the third main beam 30 so as to be able to freely slide is extended by the second stage enlarging cutting part C to press the excavated tunnel wall to get a reactive force and the ground is cut by the second cutter head. In this case, a pushing-up force acts on the first and second roof supports 20, 46 when excavating a laterally long elliptic tunnel and the roof supports prevent the tunnel from bending upward. |
