Item: ON TRIGGERING AVALANCHES, WHAT HAPPENS BETWEEN EXPLOSION AND RELEASE
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Date: 2024-09-23
Abstract: Triggering avalanches with explosives has been a well-established method for a long time, earliest records date back to the 1920ies. At least since Gubler 1977 we also know that it is most effectively done with explosives detonated at least 1 meter above the snow surface. Previous research was unclear about what types of explosives or gas explosions work best. Also, we were lacking a clear model of how the explosive transfers its energy through the air into the snowpack. Our new empirical model gives us a clear picture of what happens when the pressure wave travels across the snow surface and through the snowpack. It tells us what parts of the wavefront interact with which parts of the snowpack. After modelling the initial pulse of the explosion, we use a combination of Fourier-transform and non-linear attenuations to get a prediction of the pressure-waveform at an arbitrary distance from ground-zero. We have developed and verified this model with our own experiments. Now we can not only use this model to compare measurements taken at various distances on different ground conditions with a variety of explosive types and sizes and therefore verify our model with existing published data (e.g. Seitz). We could also leverage the model to predict the effects of a remote avalanche control system (RACS) in a location by combining it with terrain data. The model is a combination of a very simple geometric scaling law for explosives, first introduced by Hopkinson in 1915, an empirical model to predict blast pressures for explosives in free air and a frequency-based model accounting for the interaction of the pressure wave with the snowpack as it travels along its surface and through its pores. Our model confirms the work of Gubler 1977. More importantly, the model gives us insight into how the pressure wave induces an additional load and therefore breaks the weak layers and releases avalanches.
Object ID: ISSW2024_O3.8.pdf
Language of Article: English
Presenter(s): Benjamin Meier
Keywords: Explosives, Avalanches, Pressure, Shockwave, Experiments
Page Number(s): 442 - 448