Author(s): Mario Oertel; Andreas Schlenkhoff
Keywords: No Keywords
Abstract: Cross-bar block ramps are a common nature-like solution to conquer large river bottom steps. Thereby, the level difference between the upstream and downstream part of the structure will be managed by several basins, which are separated by lateral cross-bars. These cross-bars are made of large stones with diameters up to 1. 0 m and more. To guarantee stable cross-bar block ramps, two main factors have to be analyzed. On the one hand, the large boulder’s stability is in the main focus of interest due to costreduction issues after flood events. On the other hand, also the base material within the basins has to be stable, because it is creating a relevant resistant force for the balance of total forces (uplift, drag, resistance, weight). If the base material will be eroded, the structure’s stability can be at risk and a malfunction might occur. To analyze the base material’s stability on cross-bar block ramps, an experimental investigation program has been carried out in a physical scaled model. For various discharges, slopes, cross-bar heights, and base material diameters the scour development and particle transport have been analyzed. Model runs were carried out with and without arranged openings in the cross-bars. Resulting particle densimetric Froude numbers give information about the material transport. Critical particle densimetric Froude numbers were developed in dependence of relevant parameters.