SCOURING PATTERN AT DOWNSTREAM OF DIFFERENT TYPES OF ENERGY DISSIPATORS ON FLAT BED AND INCLINED BED USING TWO DIFFERENT SIZE OF AGGREGATE

Abstract

Dams and barrages play a very vital role in the economy of a country by providing essential benefits like irrigation, hydropower, flood control, drinking water, recreation, etc. However, when these fail in rare conditions, these may cause catastrophic flooding in the downstream area resulting in huge loss to human life and property. The spillway is among the most important structures of a dam project. It provides the project with the ability to release excess or flood water in a controlled or uncontrolled manner to downstream to ensure the safety of the project. The surface of the spillway should also be such that it is able to withstand erosion or scouring due to the very high velocities generated during the passage of a flood through the spillway. So the safety of spillway against the scouring at downstream is also important. To prevent the scouring of the riverbed and failure of the hydraulic structure, energy dissipators are commonly used for the purpose of dissipating the excessive kinetic energy of flowing water downstream of hydraulic structures. An experimental study was conducted to understand the scouring pattern below downstream of the spillway. A rectangular flume of dimensions 6.0m(length)X0.30m(width)X0.60m(depth), four spillway models(ogee spillway, ski jump bucket, ogee spillway with subsidiary dam, ogee spillway with baffle wall) and locally available material to prepare bed were used in this study. A pitot tube was used to measure the flow velocity and discharge. To measure the pre-jump and post-jump for the calculation of energy loss point gauge was used. In this experimental study total 40 tests were conducted using same run time. The scour pattern (depth and length) were measured after each test run.