PLUNGE POOL DESIGN AT SUBMERGED PIPE SPILLWAY OUTLETS

Submerged pipe spillway outlet flow conditions can damage the downstre am channel and the downstream end of the pipe spillway. This study was conducted to develop criteria to determine the geometry of riprap-lin ed plunge pools downstream of pipe spillways with submerged outlet con ditions. Dimensionless relationships were developed to estimate the di mensions of plunge pool and riprap size required for stability using a laboratory-scaled physical model with the following test conditions: pipe diameter (D0; 0.0628 m, and 0.0884 m); five submergence depths (T W/D0; 0.5, 0.7, 1.0, 2.0, and 3.1); three downstream channel bed eleva tions (Z/D0; 0.0, -0.5, and -1.0); and flows varying from 0.0 to 5.0 Q 2/gD5. An example design problem is presented to illustrate the use of the recommended design method. The design equations and method will r esult in stable riprap-lined plunge pools downstream of pipe spillways with submerged outlet conditions over a wide range of flow conditions .