Interaction of a Masonry Dam and the Rock Foundation

The Urft dam is an old German gravity dam located in the Eifel near Cologne. In order to ensure its stability and for adjustment to today's technical standards rehabilitation works were required. Two inspection galleries were excavated below the storage level by means of smooth blasting. To reduce the porewater pressure acting on the dam's base and thus to increase the stability of the dam also the drainage system was reconstructed and improved. Because the Urft dam is curved, its load bearing behavior reveals a certain arching effect. In order to take advantage of this arch action the stability proof was carried out by means of three-dimensional analyses according to the FEM. In these analyses the interaction of dam and the foundation rock was accounted for. Explorations, laboratory and in situ testing of the masonry and the foundation rock were carried out and a monitoring program was established. The monitoring results allowed a calibration of the three-dimensional model for stability analyses by means of back analyses. On this basis the final stability proof could be conducted.