Design Criteria for Submarine Pipeline Crossings

This laboratory investigation of pipeline crossings of alluvial streams shows that the rate of scour above the pipe varies as the dimensionless shear stress which is a function of the grain size, the energy slope, and the hydraulic radius. The dimensionless shear stress is used to determine the depth of scour that will occur for various flood discharges. The use of rock riprap protects the pipe from being washed out during floods. Prototype size of riprap may be computed according to the two following criteria: (1) geometrical similarity; and (2) fall velocity. The coefficients of drag and lift are plotted against a modified Froude number so that drag and lift forces can be computed for exposed prototype pipes.