| 摘要 |
PROBLEM TO BE SOLVED: To provide a hollow shield machine and a widening method for a tunnel, allowing the outer periphery of the existing tunnel to be smoothly widened and excavated and permitting a sufficient cut-off effect to be secured. SOLUTION: In the hollow shield machine 1, wherein a hollow part having approximately the same inside diameter as the outer periphery of the existing tunnel (a) is installed in an opened manner, an inner cylinder 2 is mounted between the outer periphery of the existing tunnel (a) and the inner periphery of the shield machine 1 and installed C without being fixed in a radial direction relative to the shield machine 1. Gaps on both sides are hermetically sealed with a seal member 3 and a flexible material 4, and a filler 5 is injected into a void part. In the widening method for the existing tunnel (a), inner-surface protecting construction is carried out by means of a protective member installed within the existing tunnel (a) while the shield machine 1 allows the outer periphery of the existing tunnel (a) to be widened and excavated in a doughnut shape, a new segment having a larger diameter than the existing tunnel (a) is assembled, and the existing tunnel (a) is supported on a supporting trestle installed within the new segment. After that, the existing tunnel (a) is removed for the purpose of constructing a new widened tunnel.
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