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Better rockfall protection through research
The WSL is conducting research into the processes involved in rockfalls. The main aims of this research are to improve rockfall risk assessments and enhance existing rockfall protection systems. To this end, researchers are monitoring rockfalls not only at the Walensee test facility, but also in laboratories and field studies and use the data for a computerized prediction model.
In a mountainous
country like Switzerland rockfalls are almost everyday occurrences. Falling
rocks damage houses, roads and railway lines and endanger human lives. In 2012
alone rockfalls and rockslides claimed five lives in Switzerland. Climate
warming might further exacerbate the dangers, as glaciers melt and the permafrost
thaws. Today, rocks and boulders are coming loose with increasing regularity in
places where ice used to stabilise mountainsides and hold rock debris in check.
In an effort to improve protective measures, the WSL is investigating the processes involved in rockfalls in a number of research projects specifically designed to improve technical rockfall protection systems and the mapping of danger hotspots in the various cantons.
The Walensee test facility
The WSL runs a test facility in Walensee, where experts put flexible rockfall protection systems through their paces (see WSL testing laboratory for rockfall protection systems) or test the resistance of protective galleries. At the facility, test bodies weighing up to 16,000 kg are dropped into various systems from as high as 63 m. The results are measured by hi-tech instruments, generating large volumes of useful data.
Rockfall in the lab and in the field
In addition, the WSL investigates how the shapes of rocks affect their trajectory. At what speed do rocks crash down a mountainside? How high and how far do they jump? And do they come to rest quickly or continue rolling down into the valley below (see rock shape). To find out, researchers drill sensitive probes into natural or artificial boulders and then roll them down various slopes under laboratory conditions or in the field, measuring their trajectories, acceleration and rotational velocities (see boulder probe). The resulting data provide a key to improving our understanding of the processes involved in rockfalls.
Computer model of how rocks fall and where they end up
Using above experimental data the WSL calibrates the simulation software RAMMS:rockfall. It calculates the rockfall trajectories and has been developed by WSL in collaboration with the Department of Mechanical & Process Engineering at ETH Zürich. The software simulates virtuell boulders rolling down into a valley through a range of terrains (flat or steep-sided, forested or rocky). The model predicts the boulders' path, how high they will jump, where they will land and with what force of impact they will land (see Testing rockfall models (German)). The model is now commercially available (see RAMMS website). The model's purpose is to help engineering companies draw up more sophisticated cantonal maps of danger hotspots.