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 — 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

Ahren Bichler is the General Manager of Trumer Schutzbauten Canada and has been working with geohazards for more than 20 years and with flexible-net systems for 17 years. He is also the president of the Association of Geohazard Professionals.

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