| 摘要 |
PROBLEM TO BE SOLVED: To provide a branch shield method capable of freely selecting the direction of a ramp exit without limiting to a starting shaft. SOLUTION: The full section excavation from a starting shaft to a ramp is achieved by a parent shield excavator M comprising three horizontally arranged shield excavators, i.e., a center shield excavator 1 and shield excavators 2 assembled on both sides, only main tunnels A, A are segment-assembled, and an excavated clearance between the main tunnels is filled with a modified excavation earth. The execution method comprises a process to excavate a ramp tunnel close to the ground surface through a replacement ground C between the main tunnels by the shield excavator 3 installed in the reverse direction at the ramp part, and a process to achieve the excavation by the parent shield excavator while segment-assembling an attachment/detachment portion of the ramp part, and to excavate the main tunnel by branch-starting the shield excavators on both sides built in the parent shield excavator.
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