| 摘要 |
PROBLEM TO BE SOLVED: To contrive the shortness of a construction period and the reduction of a construction cost by floating a casing group having a prescribed length by cutting it after the casing group is extruded on a water bottom and performing settlement after it is pulled to a prescribed place. SOLUTION: A double wall cofferdam 102 is constructed to excavate a ditch 10 from a starting part to the cofferdam 102. Next, a cut-off wall 200 is constructed to provide an extrusion yard 300 and a manufacturing yard 310. Next, a reaction force receiving wall 220 is constructed to set a sliding expansion bearing 230. A casing 400 is manufactured by the yard 310. Initial extrusion working is performed until the casing 400 penetrates the cut-off wall 200. After penetration, a revetment 101 is removed to set the extension of a ditch 103 and the bearing 230 so as to remove the cofferdam 102 to inject water. Subsequently, water is injected in the yard 300 lower than the outside water region of the wall 200 to reduce the front water pressure of the casing 400, which is set so that the casing 400 group is not returned. The working is repeated to be extruded along the ditch 103, and it is floated by a working boat 500, which pulls it to be settled. Thereby a wide manufacturing yard can be unneeded.
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