An Experimental Study for Reduction of Sedimentation Deposit at Straight Path Manholes in Urban Sewer

In general, accumulation of sediment within pipelines, manholes, and other components of urban sewer have a serious effect on sewerage arrangements, such as the resistance of the passage of flows, the cause of urban flooding, the premature operation of combined sewer overflows, and the inevitable pollution of watercourses. Therefore, it is necessary to analyze that the movements and sedimentation shape of sediment loads in straight path manholes need to be explained by experiments. In this study, hydraulic experiment model and conditions were decided by the results of documentary and field survey. The experimental apparatus which can be replaced the manhole shapes(square, circle) and invert types(general type, half circular invert, inclined benching) in straight path manholes were installed to measure deposited sedimentation quantity. The quantity of deposited sediment loads was measured by different conditions, for instance, the inflow conditions of sediment(continuous and certain period) and the amount of inflow sediment. The straight path manhole that was set up a inclined benching demonstrated the considerable effect of reduction of sedimentation in manholes without apropos of the change of manhole shapes. Moreover, the improved manhole showed that the substantial influence of the prevention of sedimentation in manholes because those would be completely removed the deposited sediment in manhole by the ideal designed velocity(1.0s) that was proposed in the design criteria of sewerage facilities. As a results, the improved manholes were able to increase the drainage capacity of sewerage arrangements in urban sewer.