OBSERVATIONS FROM CYCLES OF VARYING RESERVOIR LEVELS ON AN EXPERIMENTAL EMBANKMENT DAM

In 2019, Vattenfall AB together with several researchers, built an experimental embankment dam in Älvkarleby, Sweden. The dam was a four metres high small-scale conventional rockfill dam. The design and construction methods followed the Swedish dam safety guidelines for conventional dams. The dam was zoned, with a core made of glacial till, surrounded by fine and coarse filter zones and shoulder material. The dam was built and finalized in November 2019. Pore pressure, seepage, deformations and strains have been monitored in the dam. The impoundment of the dam was conducted in the first half of 2020, thereafter the water level in the reservoir was kept constant until early 2022. Then five cycles of emptying and filling up of the reservoir were conducted to evaluate the effects on the cyclic conditions of the embankment dam. In this contribution, the effects of varying reservoir levels on the dam body are assessed, based on the results from the monitoring of the pore pressures. Varying reservoir levels in hydropower dams, in a larger extent is usual today due to the new more flexible energy market, and are thus relevant for existing dams in the green transition.