Measuring explosive airblast of remote avalanche control systems

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Montana State University - Bozeman, College of Engineering


This research was established to evaluate the explosive blast waves from operational remote avalanche control systems (RACS). Testing was performed on Gazex, O'Bellx, and Wyssen Tower systems installed near Alta, Utah. Air pressures were measured in many directions and at a range of distances around each explosive using high-pressure microphones and custom measurement equipment. The air pressure data from each system was then evaluated based on the peak pressures generated, effective blast wave energy, the rate at which pressure increased, and the decay of these parameters with distance. Distinct differences, and some similarities, between the explosives tested were found that both validated and expanded upon previous research efforts. It was found that an 11-lb Pentolite charge (designed to be deployed from a Wyssen Tower) had the strongest effects overall, followed by the standard 11-lb gel emulsion charge from a Wyssen Tower, then by the 1.5 m 3 Gazex system (which was comparable to the gel charge in the direction of the exploder, but weaker in other directions), and lastly by the O'Bellx system (which had a more localized, but more symmetric, effect than the Gazex). In addition, many other tests were conducted utilizing 2-lb Pentolite charges, simulated Avalanche Guard charges, flat-field testing of Wyssen Tower gel emulsion and Pentolite charges, and explosives or RACS placed near unique terrain features. The 2-lb Pentolite testing validated the instrumentation for this project and showed that the equipment performed similarly to other systems from prior research efforts. The simulated Avalanche Guard charge was shown to have a very similar effect to the 11-lb gel emulsion charge. Flat-field testing of the Wyssen Tower charges showed similar blast wave strengths as was observed at the operational tower but indicated differences in the symmetry of the waves when compared to the operational tower. Lastly, the initial investigation of terrain features indicated that features such as cliffs and gullies can increase the directionality of an explosive. Overall, this work will provide avalanche control experts with much needed performance data on operational RACS and will also help to facilitate future work in this subject area.




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