Abstract
In the case of a sedimentation tank constructed in an upland field, its design conditions are affected differently by on-site environment such as rainfall and inlet structure, so that the changes in the calculated suspended soil trap efficiency can be of significant concern. The purpose of this study was to compare the calculated suspended soil trap efficiency with the observed in a sedimentation tank. For the purpose of this study, field observation was conducted to get the observed trap efficiency, and calculation was made using grain size distribution of suspended soil to get more precise planned trap efficiency. As a result, the observed trap efficiency ranged from 59% to 98%. The calculated trap efficiency changed according to suspended soil particle density ρ_p to be 29%-64%, 40%-73%, and 48%-77% to ρ_p = 1.5, 2.0, and 2.5Mg・m^<-3>, respectively. The results show that the observed trap efficiency and the calculated trap efficiency are in good agreement, and suggest that the flow similar to the one in an ideal tank was formed in the investigated sedimentation tank.
