Scour at Cantilevered Pipe Outlets: Plunge Pool Energy Dissipator Design Criteria

摘要

Cantilevered pipe spillway outlets are used at most farm-pond and many upstream flood-control principal spillways. Allowing pipe spillways to scour their own energy dissipation pools may be acceptable for small farm ponds. However, preexcavated and rip rap-lined plunge pools or more elaborate stilling basins may be required for larger, upstream flood-control reservoirs that flow at full capacity for prolonged periods. Presented herein are a research plan to provide the needed information, a description of the special experimental apparatus and instrumentation constructed for the study, and an explanation of the experimental methods used. Background information is; a description of the scour process, a method of computing the ultimate scour hole dimensions from short time tests of the scour progress, and the geometry of the jet after emerging from the pipe. The test program completed and a summary of the test data define the scope of the tests. Equations and procedures for the design of cantilevered pipe spillway plunge pool energy dissipators resulted from a detailed analysis of the experimental data. The design procedure and equations are summarized in chapter XII, and examples are given.