The publication "Norwegian Hydropower Tunnelling II" is part of the English language series published by the Norwegian Tunnelling Society, NFF. The aim is to share with our international colleagues information on rock technology, - this time with focus on tunnelling and underground works related to hydropower. As indicated in the title, this publication is the second publication in our series devoted to hydropower tunnelling. The first publication was published in 1985 as No. 3 in this series, contained 18 papers and has during the years been spread all over the world. A list of content is included in this publication as an appendix.
Some brief information about the hydropower industry in Norway: Annual production is in the order of 140 - 150 TWh and covers 95-96% of the electricity consumed by the 5 million inhabitants, - one of the highest (if not the highest) consumption per person in the world. During the last 50-60 years practically all hydropower stations have been located underground, - in total more than 200, which is in the order of 25% of all underground power stations in the world. A total of 4000 km of tunnels have been excavated for the hydropower projects, - the majority by the drill and blast method, but also approximately 200 km by the TBM method. So-called small hydropower
projects, i.e. less than 10 MW, are now built at a rate of almost 50 per year. Special Norwegian solutions like the unlined high pressure tunnels and shafts, the air cushion surge chamber, the lake tap, the sand trap and concrete plugs are described and discussed in several papers in this publication. A very special solution is to use ice to plug a tunnel for inspection and repair works. Raise drilling and directional drilling for small and mini hydropower projects are also described. Norwegian engineers have been involved in hydropower projects in a number of countries and have learned important lessons in an international market. Some of this is included in the papers presented in this publication.
On behalf of NFF we express our sincere thanks to the authors and contributors of this publication. Without their efforts the distribution of Norwegian tunnelling experience would not have been possible.
Oslo, April 2013
Norwegian Tunnelling Society NFF - International Committee