Author(s): Hung N. T. ; Dung D. V. ; Truc N. X.
Linked Author(s):
Keywords: Local scour depth; Bridge piers; Empirical coefficients in the formulae; River2D program; Finite element method
Abstract: Investigating local scour depths at bridge piers are drawing the attention from many investigators and scientists. However, most of scour-estimation-formulae are empirical (i.e. based on field data or laboratory data under simple experimental circumstances or under specific topography and geology conditions). They were thus used to build scour depth formulae at bridge piers or to adjust the parameters of the formulae. As a result, when applying these formulae to estimate for the local scour depths at bridge piers which are subjected to the effects of many different factors from the studied bridge piers; the calculated results vary significantly with distinct formulae, or are different from measured values. One of the parameters in the formulae which has a significant influence on the local scour depth value is the approach channel velocity. The values of approach channel velocity in most of the scour-estimating formulae are deriving from the one-dimensional flow. These values will be unreasonable when the bridge piers are located at the flood plain or at river curvatures and this might cause a large deviations. The calculated results of the local scour depth, in these cases, are normally very different from those in reality. In order to minimize these deviations, in this paper, the authors used the velocity field derived from a two-dimensional horizontal flow solved numerically by the finite element method from the River2D program, as a basis for determining approach channel velocities and then applying these values to the authors’theoretical formula. Based on the laboratory data and the field data, the authors identify the empirical coefficients in the formula.
Year: 2014