| 摘要 |
PROBLEM TO BE SOLVED: To provide a cut-off method for construction of an underground structure, which enables a bedrock section to be more accurately constructed than by excavation without timbering and a New Austrian Tunnelling Method, by constructing natural ground having an upper section with a high coefficient of permeability by a pneumatic caisson method. SOLUTION: The natural ground 21 with the high coefficient of permeability until a leading end of a cutting edge 2 of the caisson reaches bedrock 22 is excavated by the pneumatic caisson method, so that the caisson can be settled. When the leading end of the cutting edge 2 of the caisson reaches the bedrock 22, a grout material is infilled into a void between an outer surface of a caisson skeleton 1 and the natural ground 21. Subsequently, the bedrock section is excavated by the excavation without timbering and the New Austrian Tunnelling Method. In the case of the production of sump water from the bedrock 22 during the excavation of the bedrock section, after the sump water is temporarily stopped by applying working air pressure consistent with sump water pressure, cut-off grouting is performed, and the bedrock section is excavated to a predetermined depth, so that the prescribed underground structure can be constructed. COPYRIGHT: (C)2009,JPO&INPIT
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