Design of Riprap Stilling Basin for Overhanging Pipe

The rock rip-rap basin is the most common and economical method of handling the problem of scour at a pipe outlet. The advantage of the method is speed of construction, absence of the need for skilled labor, and utilization of inexpensive local deposits of rock. The most important step for designing the rock basin is to determine the riprap criteria including: 1. proper rock size, large enough to withstand the action of the jet and small enough to be economical; 2. proper size distribution (gradation); 3. proper thickness of the layer of rock riprap; 4. proper filter beneath the layer of rock riprap, and development of such criteria is the main purpose of this paper.