Rockfall Mitigation Using Flexible-Net Systems
Ahren Bichler
Part 1: “Standardized approach to rockfall fence design”
The influence of the ETAG 27 guideline (now called E A D 340059-00-0106) for the certification of flexible-net rockfall catchment fences has played a vital role in the advancement of the industry. It makes it possible to compare products, from different material suppliers, through standardized reporting of testing and material data. However, not considered are best practices for the implementation or the evaluation of project safety and maintenance.
To help address this gap in application knowhow, the Austrian Standards Plus – the Austrian national standards body, similar to Standards Australia – published an application guideline that goes beyond system certification guidelines, though in a much more broad spectrum including stabilization with anchoring and mesh/nets, embankments, and galleries. The document is entitled “ONR 24810, Technical protection against rockfall – Terms and definitions, effects of actions, design, monitoring and maintenance”, first published in January of 2013, with the most recent updated version in 2021.
This presentation will focus on summarizing the parts of the ONR specific to catchment fences beginning with the initial site investigation through to establishing maintenance and inspection schedules.
Part 2: “Long-term relationships with rockfall catchment fences”
Flexible-net rockfall catchment fences can absorb large amounts of energy because of their ability to tolerate large deformations. Such deformations are commonly referred to as “damages” but are in fact evidence of normal function. The extent of deformations related to 3 major rockfall events impacting a single structure over the span of a decade are summarized and yield information on expectations of performance and maintenance. Observed deformations correspond well to those reported in full-scale testing. Each event was progressively larger and involved energies greater than the system’s rated capacity. The performance of the system in relation to the characteristics of natural events, site geometry, efficiency of flexible-net systems and the deformability of both the anchorage and the post base supports will be discussed.
About the speaker
Ahren Bichler General Manager, Trumer Schutzbauten Canada Ltd. and President of Association of Geohazard Professionals
Ahren Bichler is the General Manager of Trumer Schutzbauten Canada Ltd. and has been working with geohazards for more than 20 years. He hold’s a Master’s Degree in Earth and Ocean Sciences from the University of Victoria, where he specialized in Quaternary geology with a focus on subsurface mapping of landslides using geophysical techniques. Ahren worked for the British Columbia Ministry of Energy and Mines as a project geologist and as a research assistant and lecturer at the Friedrich-Alexander University in Erlangen, Germany where he worked on surficial mapping related to high-alpine debris floods and rockfall in the Austrian Alps. Ahren was involved with the compilation, review and recommendation of landslide hazard and risk mapping methods for the Geological Survey of Canada. In addition, he was part of the Asia-Link program, which brought geohazard specialists from Europe to Nepal and Bhutan to conduct knowledge sharing workshops. Since 2006 he has been working with geohazard mitigation products including avalanche protection systems, rockfall catchment fences, debris flow barriers and slope stabilization measures. Outside of Trumer, Ahren is active in the geohazards industry, sitting on the board of the Association of Geohazards Professionals since 2013 and serving as its president since 2017.
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