Reliability Simulation of Scouring Downstream of Outlet Facilities


Abstract: Alluvial streambeds downstream of an outlet facility may be seriously scoured under jet action. The degree of scour depends on the characteristics of the jet leaving the outlet facility, depth of tailwater, and properties of the bed material. Existing scour prediction equations reported in the literature are deterministic in nature, and do not account for the randomness of the parameters involved in the models. Therefore, the level of scouring risk is unknown. This paper is concerned with the investigation of the relationship between the reliability of scouring induced by vertical jets downstream of outlet facilities and safety factors. The scour equation proposed by Okyay has been used in the calibration of the simulation model based on Monte Carlo analysis. In reliability-based analysis, which can be carried out during the planning stage, the level of reliability for various foundation depths is estimated under design flow conditions. Furthermore, the relationship between the required size of armoring bed material and reliability under the desired foundation depth can be obtained. An example is presented to illustrate the use of the model.

Keywords: Scour, Reliability, Outlet Facility, Monte Carlo Simulation, Safety Factor.

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