Abstract
A complex cross-section reinforced concrete pipe that combines a sub-pipe for the flow of sewage in dry weather and a main pipe for the flow of rainwater was developed to reduce sedimentation of the combined sewer system in dry weather. The sub-pipe was designed, considering the flow velocity, constructability, and maintenance. By fitting the sewage data in the dry weather to the normal distribution, the ratio of the cross-sectional area of sewage flow to that of the pipe was determined to be approximately 0.418, which could cover 99.85% of the sewage volume of the target site. Based on this ratio, the diameter of the sub-pipe corresponding to the combined sewer system with a pipe diameter between 450 and 1300 mm was determined. The hydraulic performance analysis results showed that the flow velocity increased by 11 to 12% compared to the circular pipe based on the full sub-pipe and by more than 15% depending on the water level. The shear stress increased by more than 16.5%, and higher tractive force was observed. Structural safety was determined as the crack load and failure load far exceeded the minimum criteria, thereby verifying the feasibility and field applicability of the complex cross-section reinforced concrete pipe.
Highlights
Sewer systems play an important role in public health, and sedimentation in sewer pipes is a chronic problem that degrades the quality of public services
In the combined sewer system, sedimentation and odor occur in dry weather conditions due to a small sewage flow rate
A complex cross-section reinforced concrete pipe was proposed in this study
Summary
Sewer systems play an important role in public health, and sedimentation in sewer pipes is a chronic problem that degrades the quality of public services. The low flow velocity of sewage causes sedimentation of external substances and pollutants involved with sewage [1,2,3], and intensifies the coagulation of fat, oil, and grease [4]. Sedimentation aggravates the odor in sewers by stagnating odor-causing substances or causing anaerobicization [3,7]. For combined sewer systems that drain both sewage and rainwater, odor is discharged to the outside through manholes and street inlets, and rainwater washes sediments, thereby deteriorating the combined sewer overflow (CSO) concentration [9,10]
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