Stable Riprap Size for Open Channel Flows
Abstract
Riprap revetment is a widely used method for protecting the boundaries of erodible channels. Determining riprap size is an important step in the design process. Some of the existing methods for riprap sizing use the critical shear stress relations and logarithmic velocity laws to determine stable riprap size. Flume data used in this investigation show that use of a constant Shields coefficient in the critical shear stress relations is not valid for high relative roughness problems like riprap design. Neither are logarithmic velocity laws valid for high relative roughness problems. Another limitation of existing riprap sizing methods is lack of variation relative to the effects of gradation, thickness, or shape. Existing side slope relations used in the critical shear stress equation overestimate the decrease in stability that occurs when a particle is placed on a sloping bank. Comparison of velocity profiles over channel side slopes in straight and curved reaches shows that for the same average velocity over the toe of the side slope, the velocity and shear stress on the side slope are significantly higher on the outer bank of the curved channel. Depth and average velocity over the toe of the side slope are measured in straight and curved flume tests of riprap stability and are used to develop sizing relations for side slope riprap.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1988
- Accession Number
- ADA195245
Entities
People
- Stephen T. Maynord