Rectangular Storm Sewer Design Under Equal Sediment Mobility

Abstract

Rectangular storm sewers are conduits delivering water to outfall locations and have sizes that are typically larger than standard pipes, by which they become subject to more sediment deposits during operation and thus require higher flow strengths to maintain the bed clean. This study suggests a design procedure of self-cleansing rectangular sewers based on maintaining a lower limit of Shields stress and an upper limit of dimensionless bedload transport capacity. The lower limit of Shields stress is proposed under two considerations: to sustain equal sediment mobility at the channel bottom instead of selective transport and to avoid progressive deposition of finer grains due to low and reducing flows. The upper dimensionless bedload capacity is determined rationally and confirmed by using experimental data obtained from the literature. An existing bedload transport equation developed under equal sediment mobility is modified to provide a basis for the design method. It is shown that the proposed design procedure can practically be applied for a channel to estimate sediment concentrations by setting the required flow strength of Shields tress and particle size. Charts are given as an example for determining explicitly the channel design parameters. The study demonstrates that despite the high flows imposed, the design specifications determined according to this criterion can reasonably be achieved in practice for a given project.

Evolutionary optimization of neural network to predict sediment transport without sedimentation

“…Many researchers have undertaken various experimental and empirical studies on sediment transport without sediment [6][7][8][9][10][11][12][13][14]. It can be said that classic methods do not have the capacity to estimate the flow velocity that prevents sediment deposition under different conditions, and there is a need for methods with such capacity.…”

Design criteria for sediment transport in sewers based on self-cleansing concept

“…Azamathulla et al (2012) used a multiple regression model and an adaptive neuro-fuzzy inference system (ANFIS) to predict the functional relationships of sediment transport in sewer pipe systems, which showed that the ANFIS approach gives more satisfactory results compared to previous methods. Almedeij (2012) suggested a self-cleansing design procedure for rectangular sewers based on the sediment transport theory. Ota and Perrusquía (2013) studied sediment transport at the limit of deposition in sewers, which suggested a modified dimensionless bed shear stress equation.…”