Study Of Soil Particle Size Effectine The Scour Reduction Behind Hydraulic Structures


Mamdouh Ahmed Dardeer
Lecturer of Irrigation and Hydraulics Faculty of Engineering, Al-Azhar University, Egypt.


Many ways have been studied to energy dissipate behind vertical gates, but not recommended that best size of soil grains downstream hydraulic structure, especially with the use of nonconventional sill Y-shaped. Theoretically, studies have been conducted using numerical analysis method to determine the relationships between variables and the various parameters. An intensive experimental study has been conducted in glassed wall flume with square cross section of (30 cm × 30 cm) and length of 4m. Different conditions of Froude‟s number`(Fr) from 5.38 to 10.4. In this study nonconventional sill has been studied with three inclined angles (45ᵒ, 30ᵒ, 15ᵒ) and the relative distance (Lb/Lf = 0.27, 0.22, 0.17) and the best results were given for an angle of 30 with Lb/Lf = 0.27 to reduce the scour depth and length. The soil remaining after the scour completion has been collected behind the vertical gates and sieve analysis was done. The scour area was backfilled was with the same specifications as the soil remaining. Re-experiments have been done with the same conditions, to detect the best case. Measurements using ultrasonic device were taken, analyzed, presented and discussed. It was deduced that the optimum particle size of soil for backfilling behind the hydraulic structures, where Fr ranges from Fr from 5.38 to 10.4 is relative soil diameter D50/B from 2.8×10-4 to 1.5×10-3 and relative soil diameter, the scour depth and length will be decreased by percentage 50% to 60%, and 40% to 60%, respectively.