Abstract
The power plant “Røldal Kraftverk” is located close to the village of Røldal in the Vestland county, Norway. Røldal power plant operates with a water head of 382 m. The installed capacity is 172 MW (two Francis turbines), with an average annual production of about 919 GWh. The project has been designed and in operation since 1966. This was the time when rock stress measurements were not common, so the steel lining of the project was designed based on guidance from an empirical rule of thumb. During 60 years of development, since Røldal HPP was built, the rock stress measurement technology has developed and is capable to provide a far more accurate and precise description of the in situ stress conditions. So, for the new in situ stress evaluation at Røldal HPP, the NoRSTRESS research project carried out a campaign of rock stress measurement at this site in 2023, using hydraulic test methods. For the measurement, 9 drillholes were drilled in three mutually perpendicular orientations. This is to test different layouts of measurement and to test different method for estimating in-situ stress. Attempt to obtain orientation of pre-existing and induced fractures was also made by using impression packer and optical televiewer (OTV).
This paper presents practical experiences and challenges during the measurement campaign together with the measurement results.