Block erosion of unlined rock spillway canals / Blockerosion av utskov i berg

David Saiang, Musa Adebayo Idris, Erling Nordlund


This block erosion study focuses on hydropower dam spillway canals in Sweden and their rock mass or geological conditions. Some observations may not be relevant to observations in the other places due to the differences in geological factors. However, the Swedish experience are comparable to the arctic region countries, that have similar geological conditions.

Another factor is the time history of the Swedish hydropower dams. Many of these dams are approaching either 100 years or have exceeded 100 years. During this long period design methodologies have evolved with better understanding of hydrological and geological conditions and even more so, the adaption of risk-consequence based design methodologies. Therefore, these dams face unique challenges not only related to geological conditions, but also the need to improve them to meet the current standards in dam safety that did not exist when they were constructed and commissioned.

This report does not dwell on the design issues of the dams, but it focuses on rock conditions of the spillway canals. Many of the Swedish hydropower dams have and are seeing erosion in the spillway channels, which in the long term will affect the safety of these dams. The report focuses on the geological conditions and mechanisms that promote block erosion. The term “block erosion” is used here because the majority (if not all) of the Swedish hydro-power dams are constructed on hard rock masses.
And therefore, the 
occurrence of erosion involves rock blocks.

Although there are well over 1000 hydro-power dams in Sweden this field inventory or field investigation only involved two hydropower dams. Both hydropower dams are among the largest in Sweden. The geological conditions of these two dams are uniquely different and thus provide a contrasting observation of block erosion and the mechanisms involved. It is observed that majority of the dams in Sweden may fall within the characteristics of these two dams with respect to block erosion or scouring of the discharge canals and tunnels.

The research was conducted at Luleå University of Technology by the Mining and Rock Engineering research group at the Division of Mining and Geotechnology Engineering. The research was led by David Saiang and assisted by Idris Musa, Erling Nordlund and Jonny Sjöberg. The research project was supported by a reference group consisted of Anders Isander (Uniper), Peter Viklander (Vattenfall), Eva Hakami (Geosigma), Fredrik Johansson (KTH) and Per Tengborg (BeFo).

Financial support was provided by BeFo and Energiforsk.

Stockholm, 2022
Per Tengborg

« Tillbaka