| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that a proposal to improve drainage of a top plate part by providing a large number of slit holes, drain grooves, etc. for the top plate part has been extremely insufficient in reality since a top plate substantially contributes to the maintenance of strength in a portal block, it has not been possible to provide a large opening part, and it has been difficult to adopt a technique for providing drainage by covering a whole top surface with a grating. Ž<P>SOLUTION: In a portal integrally molded block constituted of both a pair of opposing sidewall plate parts and a top surface part comprising the top plate part and a large opening, one or a plurality of lines of bottomed drain grooves are provided for the upper surface of the top plate part, and at least one line among them is provided along the length of a body. Water-permeable holes communicating with the inside space of the block are provided for a plurality of locations of the grooves. The bottom surfaces of the drain grooves with bottoms are provided with a slope sinking toward the locations of the water-permeable holes or end parts. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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