Analysis of changes in the velocity diagram of gravity sewer networks with different thickness of sediment layer in the chute section of pipes

Abstract

The practice of operation of gravity sewer networks of domestic wastewater shows that sediment de-posits are formed in the chute section of pipes at certain velocities of the gravity flow. These deposits affect the hydraulic characteristics of the flow, which depend on the actual thickness of the sediment layer in sewer pipes. In this study, a velocity diagram reflecting the distribution of actual velocity values of wastewater flow along the depth of the wetted perimeter of pipes with sediment deposits in their chute sections is established. To this end, the dependences derived by the authors previously for hy-draulic calculation of drainage networks with internal sediments were used. It is confirmed on a specific example that the limiting value of sediment thickness preventing the continuation of further operation for concrete pipes with a diameter of 400 mm equals 80 mm. The obtained diagram of the vertical ve-locity distribution of sewage flow can be used to determine the actual pipeline fill level corresponding to the actual sediment layer thickness in sewer pipes.