How effective is avalanche blasting? Scientists blow the lid

Ten seconds left until the charge ­detonates. Stephan Simioni takes shelter. A deafening explosion fills the wintry valley of Hinterrhein, not far from the A13, where tourists are heading south in search of warmer climes.

To protect ski slopes, and roads such as the A13, safety officers will often trigger avalanches with ex­plosives as a precautionary measure. In his doctoral thesis, Simioni is investigating what happens during these explosions in the snow and the effectiveness of the blast methods. Today he’s using video cameras to track if and where snow fails after an explosion. Microphones record how the waves caused by an explosion spread out across the snow, and ac­celeration sensors measure the extent to which the snow cover is deformed by the pressure. Since Simioni is carrying out his detonation ex­per­iment on level ground at a shooting range, it poses no danger to anyone. He completed his first blasting course – just for fun – while he was studying civil engineering. At the time, he did not know that it would soon become a passion.

Since then, he has detonated some­where in the region of 100 explosive charges; it is the largest series of experiments conducted by someone other than an explosives manufacturer, and the only one to compare different methods independently. And the work is not yet concluded; further experiments are planned, not just on level ground, but also on avalanche-prone slopes. Simioni would like to better compare the effect of systems that use explosives with those that use gas – a particularly useful plan­ning aid for practitioners. That’s why experts from various different cantons and ski regions are ac­com­panying him in his doctoral work. The Federal Office for the Environ­ment also sets great store by reliable results: Simioni’s mission, therefore, is to present a standard test for the comparison of blast methods.

This work has already produced its first results: his experiments show that the stress caused by the ex­plosion on areas within a certain distance of the blast is smaller than previously thought. To assess the practical implications of this, Simioni is working on a computer model that is able to simulate how simple topo­graphy, such as depressions or the slope angle, can influence the effec­tiveness of the blast. He is also happy with the experimental set up at Hinter­rhein: “The experiments on the level study plot and explosions on operational avalanche release sys­tems are comparable. We are not far from a reliable standard pro­cedure. The results of this work will give safety officers a valuable basis on which to assess where and how best to carry out avalanche blasting.” (Christine Huovinen, Diagonal 1/16)