Rockfall Attenuator Systems. A new design concept for protecting linear infrastructure

Helene Hofmann, James Glover, Duncan Wyllie, Tim Shevlin, Andi D Buechi

In the proceedings of: GeoEdmonton 2018: 71st Canadian Geotechnical Conference; 13th joint with IAH-CNC

Session: Geohazards in Linear Infrastructure

ABSTRACT: Rockfall impact attenuators intercept the trajectory, reduce potential bounce height, and dampen the rockfall velocity therefore attenuate the total kinetic energy of rockfall. A controlled guiding of the rock(s) to a designated collecting area is then possible avoiding costly clean-outs as with standard flexible rockfall barriers. This type of low maintenance, passive rockfall mitigation system is increasing in popularity worldwide but no design guidelines exist. The loading mechanisms and the importance of the rotational velocity and directional behaviour of the rocks upon impact remain largely unknown. The loading of the system, the attenuation processes and the importance of the rotational component are being analysed in a joint research program between Wyllie & Norrish Rock Engineers, Ltd. in Canada, Geobrugg North America, LLC, and Geobrugg AG, Switzerland. Full-scale testing was performed in 2015, 2016 and 2017 on a test site in British Columbia. The tests were conducted with instrumented concrete blocks and natural rocks, load cells were installed in all support ropes and the testing was recorded with two high speed cameras. Five different high-tensile strength structural nets were tested with more than 200 rolling rocks/blocks. This contribution provides the results of the loading analysis of the attenuator system, as well as the comparison of the acceleration and rotation components between the rock motion sensors, the video analysis and the RAMMS ROCKFALL simulation. Preliminary results highlight the importance of the rotational component and the importance of the impact angle of the rock into the mesh, affecting the translational velocities. Ultimately these analyses will be used to create standard Attenuator systems and ideally the framework for a design guideline.

RÉSUMÉ: La dynamique de chute de blocs et leurs interactions avec un système d'atténuation ou déflecteur sont étudiées dans le -importance de la Colombie Britannique. Les essais ont été documentés par deux caméras à haute vitesse, des cellules de mesures dans tous les câbles du système et des capteurs de mouvements tridimensionnels dans les blocs en béton renforcé. Le reste des blocs provient de la carrière de granite où est situé le site test. Cinq filets en acier à ultra haute résistance ont été testé au cours des années avec plus de 200 impacts de blocs. ation de chutes de blocs, RAMMS::ROCKFALL. Le but ultime est de pourvoir un standard pour déflecteurs.

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