United States Department of Transportation
i
Design and Performance Evaluation of a Semiflexible Snow Barrier for Avalanche Protection
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2020-03-01
[PDF-6.67 MB]
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Edition:Final Report – December 13, 2016 to March 31, 2020
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Abstract:A new type of avalanche risk reducing snow supporting structure called a “snow supporting umbrella” or “SSU” was investigated for its potential effectiveness in preventing natural release of snow avalanches. Because no existing design specifications or other publications address how the geometry, member arrangement, and connection details of a SSU should be selected, a research project to develop the SSU concept and a generic design process was funded by and performed for the Wyoming Department of Transportation (WYDOT). Additional motivation for the project included the need to reinforce a region of the Milepost 151 Avalanche starting zone where small natural snow slab releases have occurred in between two rows of existing rigid steel snow supporting structures. An analysis of the interplay of various design parameters was performed, followed by application of a structural analysis and design process for the design of three SSU to be fabricated and installed at the project site. Due to the lack of redundancy of the single ground anchor foundation of the SSU, a novel load-limiting slip device for the connection between the SSU and foundation was developed and implemented on the fabricated SSU. Three SSU were installed at the site where the previous small avalanches were observed and then monitored over a period of two winter seasons. No subsequent avalanche activity was observed after the row of SSU was added to the facility. Annual inspections of the SSU over two summer periods indicated that the SSU performed as intended and without noticeable distress in any of its elements. Installation of the SSU at the project site required significantly less labor on-site in the steep starting zone area compared to what would be needed to install rigid steel snow bridges or flexible snow nets. A cost comparison using data from four different passive avalanche defense projects in the United States including rigid, flexible, and semiflexible snow supporting structures indicates that the SSU concept has the potential for significant construction cost savings over the other two systems, primarily due to reduction in the number of foundations and the required onsite installation labor.
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