| 摘要 |
PROBLEM TO BE SOLVED: To provide a construction method for forming a widened section of a shield tunnel which is equipped with a steel bent pipe functioning as protecting work for covering the periphery of the widened section while having rigidity high enough to enable utilization as a part of a mainly installed structure, and capable of dispensing with the installation of a support during excavation, and a structure of the widened section. SOLUTION: The steel bent pipes 16 which are laterally protruded in an arc shape with a constant curvature are provided at a predetermined pitch along the longitudinal direction of the tunnel between steel segments 41a which are arranged at upper and lower edges of a section for forming the widened section 8 by using a pipe-jacking excavator. A reinforcing steel material is inserted inside so that both ends can be fixed to a main girder of the steel segment via a joint plate, and stiffening is applied by infilling a solidification material. After solidification, a segment 41c of the portion for forming the widened section is removed, lateral sediment is excavated, the inside surface of the steel bent pipe is exposed, and a lining body is formed by covering an exposed surface. A cross section of the steel bent pipe is formed in such a rectangular shape that its aspect ratio is set at 2:1 or 3:1, and the pipe-jacking excavator is constituted by providing a leading end with two or three excavators performing excavation while forming a square cross section. The steel bent pipe allows the penetration of a skin plate by avoiding a rib of the steel segment. COPYRIGHT: (C)2008,JPO&INPIT
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