Rock scours after a spillway of a dam can lead to major problems regarding the stability of the structure. The pressures on the floor are dependent on the height of the dam and the water cushion in the pool. They can reduce the effective stress between the rock blocks significantly and hence the friction resistance. This mechanism leads to proper instabilities in the foundation and the structure. A model test at the Institute of Hydraulic Engineering and Water Resources Management should expose the pressures on the bottom floor. The results of the test case show a significant decrease of these pressures due to the evaluated configuration of the model. Further investigations, in a more detailed model, with cracks in the rock for different quantities of the jet velocity and the depth in the stilling basin are planned as well as numerical simulations by means of fluid-foundation interaction for comparison reasons.
Rock scour next to the spillway of dams can influence the stability of the structure significantly. Dynamic pressures on the rock foundation due to the impact of high velocity jets lead to abrasion and hence instability. The increasing accuracy of methods for determining the hydrological data lead to assessment criteria that are more exact (Achterberg et al. 1998). This fact concerns mainly older structures, where additional measurements will therefore be necessary. In addition, newer structures are also affected by rock scour, because the knowledge about theses dynamic pressures is still very limited. Although, more and more papers have been published in this field recently (e.g. Bollaert 2002). However, the foundation at the impact zone will crack eventually and the dynamic pressures induced will propagate through the cracks and possible fault zones. These water pressures can reduce the effective stress between the rock blocks significantly and hence the friction resistance. A model test for a survey at the Institute for Hydraulic Engineering and Water Resources Management at Graz University of Technology led to the idea to investigate this problem more elaborated. Therefore, a more detailed model with a wedge and joints is planned to be evaluated along with different discharges and water depths (water cushion) as well as numerical simulations for comparison reasons.
