The combined sewer improvement projects dealt with in advanced sewer areas have issues in flowing water splitting accuracy in a rainwater discharge chamber, which is an important point in the combined sewer system. It is also pointed out that this measure has low improvement effect as well as complicated maintenance and management. The flowing water splitting function is made by organically combining the hydraulic phenomena of an overflow weir and an orifice. While the conventional technology directly controls the flow rate by splitting one time, this study proposes indirect control of the flow rate of suppressing water level fluctuation by splitting multiple times. This study has proven validity from the viewpoint of practical management through numerical analysis of the splitting phenomenon and careful examination of the data of a hydraulic model experiment to verify the technical theories of the conventional direct control and the new indirect control in flowing water splitting. The result of this study has confirmed the improvement effect where an error in the 45% level in the conventional technology can be reduced to 3% or less by the technology used in this study in the numerical analysis and the hydraulic model experiment focusing on the excessive interception error. It has also shown that the immediate issues in the combined sewer can be solved.
2016 Japan Society of Civil Engineers