| 摘要 |
PURPOSE: To prevent floating of a manhole simply at low cost. CONSTITUTION: An overhang section 20 is formed on an outer face of a manhole main body 14 in such a manner that it is positioned in a non-liquefaction layer. When buoyancy that a manhole 10 receives from a liquefaction layer is F, the weight of the manhole is F1 , the weight of earth and sand 24 above the overhang section 20 is F2 , and shearing resistance force between the earth and sand 24 and its peripheral ground is F3, the lengthδof the overhang section 20 and the depth h from the ground level to the overhang section 20 are set to satisfy an equation F1 +F2 +F3 >=F.
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