Most Hydraulically Efficient Riprap-Lined Drainage Channels |
| |
Authors: | David C Froehlich |
| |
Affiliation: | Consulting Engineer, 303 Frenchmans Bluff Dr., Cary, NC 27513.
|
| |
Abstract: | Dimensions of the most hydraulically efficient trapezoidal and triangular drainage channels (that is, those with the smallest possible cross-section areas) whose banks are lined with loose rock riprap are found along with the stable stone diameter by solving a constrained nonlinear minimization problem. The problem statement is made dimensionless and less complicated by normalizing solution variables and combining parameters into two dimensionless quantities that describe the composite roughness of a channel and the stability of the rock lining. Normalized values of section bottom width, water depth, and rock diameter, along with the channel side-slope ratio, are found numerically. Results of the analysis are presented graphically and, when practical, in the form of empirical expressions. The solutions, which are comprehensive, give cross-section dimensions and the rock size needed to maintain a stable bank lining, greatly simplify design of hydraulically efficient riprap-lined open channels. |
| |
Keywords: | Drainage Open channels Riprap Design Hydraulic roughness Shear stress |
|
|