| 摘要 |
PROBLEM TO BE SOLVED: To protect a manhole made of a resin from being damaged even if crushed stones are employed as a backfill material in place of sand and generated soil, the sand being in short supply as natural resources, the generated soil being unsecurable in quantity. SOLUTION: The manhole 1 made of a resin has a connecting riser 3 (insertion port) extended upward from a main body 2 thereof, and pipe connecting portions (an insertion port 4 and a receiving port 5) extended sideways. At least a surface of the main body 2 is coated with a protective layer 11 formed of an resin-impregnated nonwoven fabric or a resin coated layer, and therefore the surface of the manhole 1 is protected from being damaged by acute angle portions of crushed stones and external pressure. COPYRIGHT: (C)2004,JPO
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