Author(s): Kazuhiko Takabe; Hitoshi Ikenaga; Masaki Matsuo; Shizuo Yoshikawa; Osamu Matsushima
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Abstract: In urban sewer pipe systems, the phenomenon that manhole covers are brown off has been taken when it rains heavily and drastically. The phenomenon is caused by flow and air-masses. We focus on behavior of air-masses in the inverted siphon with hydraulic model experiment. Firstly the air-masses are formed during the unsteady hydraulic bore appearing. When the water depth is getting near the pipe height, the air-masses are trapped at the pipe crown. Secondary the air-masses move pipe to manhole by hydraulic surging. Finally the air-masses spurt into the air, then the water level of manhole is moving hardly. Especially, if water level of the manhole is high, nearly the crown of the manhole, the air-masses affect the water level and manhole cover. Through the experiment, to prevent the phenomenon that manhole covers are brown off, we can obtain that it is necessary to install the system that can separate the water from the air-masses.
Year: 2009