Author(s): Boriss Gjunsburgs; Andrei Kolyshkin; Elena Govsha
Linked Author(s): Boriss Gjunsburgs
Keywords: No Keywords
Abstract: Elliptical guide banks are used to guide the flow and sediments in and out of the bridge opening, to reduce the flow separation at the alignment of the bridge, and to remove scour hole from the abutment and embankment. The differential equation of equilibrium for the bed sediment movement for clear-water conditions is used and a new mathematical model for computing the scour development with time at the elliptical guide banks is elaborated. We suggest to solve initial equations numerically using software packages available for the solution of the Cauchy problem. In this case the time step can be chosen in order to guarantee desired accuracy of the solution. In particular, using adaptive integration formulas, one can select the step size automatically. There are at least two advantages of the proposed approach in comparison with the our method used before (Gjunsburgs et al., 2006): the next time step can be selected by analyzing the properties of the solution at the previous time steps, that is, one can choose a smaller time steps, where the solution changes quickly and larger time steps where the solution does not change too much, and there is no need to approximate scour depth h s by a constant at each time step. The scour depth computed during multiple floods can be compared with its equilibrium value calculated by the equations suggested early, and the flood damage risk factor for guide banks can be determined as a ratio of h s /h equil.