PIPING PHENOMENA AT OSTROVUL CORBULUI DIKE.

Iron Gates II hydropower plant includes, for the protection of Ostrovul Corbului area, an embankment dam founded on highly permeable and easily trained alluvial soils. The initial protection dike project did not supply a cutoff wall and the solution adopted to maintain a certain water level within the enclosure area was to pump the excessive water over the dike and out in the lake. Groundwater movement between the retention arrangement and lower levels created by pumped water lead to damages brought to the soil structure. Such a phenomenon is reported near the pumping station, which is emphasized by changes in water levels after the drainage process. This study aims to identify the potential causes of the piping phenomena which have appeared at Ostrovul Corbului dike and the possible remedial solutions using the available data and mathematical modeling. To confirm the assumptions regarding the piping causes and to establish the appropriate solutions, a transient 2D model was realized using the finite elements method. Following the mathematical modeling some of the assumptions were confirmed and others were determined. To remedy the situation, two complementary solutions have been proposed: interventions on the pumps in order to be able to adjust the flow and to realize a cutoff wall which modifies the flow so that the current lines move away from the sensitive area near the pumping station. [ABSTRACT FROM AUTHOR]