Problems with existing theories of snow avalanche impact on structures скачать в хорошем качестве

Problems with existing theories of snow avalanche impact on structures

Problems with existing theories of snow avalanche impact on structures (or how to make a snowball that hurts) SLF Kolloquium by Dr. Perry Bartelt held at WSL Institute for Snow and Avalanche Research SLF, Davos Dorf, Switzerland (23.01.2019) Abstract: A general problem in natural hazard engineering is to design structures that can withstand the impact of snow avalanches, rockfalls and debris flows. It is central to developing cost-effective technical mitigation strategies and long-term management policies for protective forests. Although the mechanics of collisional impact is well-understood, the application to snow avalanches is difficult because snow at impact exhibits both solid and fluid behaviour. In this colloquium we present practical methods to calculate impact pressures, dividing the interaction into three distinct processes: pile-up, deflection and jamming. By application of the work-energy theorem , we predict the impulsive (shock) loadings from pile-up and demonstrate the importance of inertial forces when predicting structural (breaking) stresses. This analysis helps explains why trees with low eigenfrequencies can easily withstand short-duration impacts arising from flowing avalanches. We then determine long-duration pressures arising from deflection and jamming, that are induced after the initial loading. Again the work-energy theorem helps us to highlight important differences to “shockwave” theories and problems with measurements. The colloquium is in English and designed to be understood by snow researchers outside the specific field of avalanche dynamics.