Highway A3 was opened in 1964 as a 2-lane road passing through the topographic bottleneck of the Walensee. The Walensee is one of the main thoroughfares between the Swiss plains and the mountainous regions and ski resorts. The roadway has always been exposed to rockfall and rockslides from the beginning. In 1986, due to increased traffic volume, one of the most frequented tunnels was expanded to four lanes. Naturally, geohazard protection measures were required to be installed along with the roadway expansion.
In 2012 it became apparent to the Swiss Federal Roads Office FEDRO that several hot spots for geohazards would require immediate maintenance to keep Highway A3 open. The identified hot spots include various tunnel entrances, steep slopes and sheer rock faces along the roadway. The project planning phase began in 2013, and by the end of 2015 the first protection systems of Geobrugg’s newest generation were installed.
Official project name at the FEDRO, Federal Office for Roads: Glarus Nord
Overall costs of the protection project (estimated in 2014): 11 Mio. Swiss Francs
This description only details the northwest oriented tunnel entrances of Ofenegg and Kerenzerberg.
The overall project included a portfolio of Geobrugg flexible barrier systems protection measures to contain rockfall events. The selection was based on extensive rockfall analysis, taking into account bouncing heights as well as energy impacts. System strength, height and line lengths were set to maximize safety and optimize cost-effectiveness.
Above the two tunnel entrances the following Geobrugg rockfall protection systems were installed in geographical order from southwest to northeast: