What You Need to Know
The mitigation of hazards posed by rockfall processes has a long history and takes on many forms. State-of-the-art practices are documented for many aspects, but of particular interest here are standards involving rockfall catchment fences. With the development of modern systems within the last decade, there has been significant changes to the standards. There are two main types of standards: 1) testing and certification standards and 2) design and application standards. The first deals with the materials used to carry out mitigation and the second with the way in which the materials are applied.
Testing and Certification Guidelines
Most commercial manufacturers of rockfall catchment fences originate from Europe where such systems have been in use for around 50 years. In the beginning the systems were untested constructions, often fabricated on site or in an unsophisticated way. Gradually as the products became more commercialized there was a need for a standardized approach to ensure performance. Several test facilities were built in different countries and local (national) guidelines began to take form.
In Austria, the first guidelines for testing rockfall catchment fences were set in 2002 by the Austrian Service for Torrent and Avalanche Control (WLV) within the Federal Ministry of Agriculture, Forestry, Environment and Water Management. These guidelines ensured 1:1 scale testing was carried out in a clear and reproducible way.
In 2008, the European Organisation for Technical Approvals published a Europe wide guideline called ETAG 27 Guideline for European Technical Approval of Falling Rock Protection Kits.The guideline defines the requirements for obtaining an ETA – European Technical Approval (until 2012) or European Technical Assessment (since 2013) – and serves as the basis for CE certification.
Since 2019 the ETAG 27 guideline was superseded by EAD 340059-00-0106 (European Assessment Document) published by the European Organisation for Technical Assessment. The contents of the new document closely resemble its predecessor with only minor changes.
Design and Application Guidelines
Design and application guidelines are those which help engineers, planners and contractors apply mitigation measures, such as rockfall catchment fences, in a systematic and efficient way. There is only a very limited number of such guidelines in the world and currently only one published in English. The ONR 24810 was published by Austrian Standards Institute, first in German in 2013 and in English in 2017.
The guideline is entitled “Technical protection against rockfall – Terms and definitions, actions, design and construction, and monitoring and maintenance”. The comprehensive document details rockfall mitigation procedures for various efforts including stabilization with anchors and mesh, embankments and galleries, as well as rockfall catchment fences. It does not concern itself with material testing but rather how mitigation structures are to be implemented through standardized site investigation, design, construction and maintenance.