FIELD EXPERIMENTS ON WEAK LAYER FAILURE AND CRACK PROPAGATION DUE TO EXPLOSIONS

ABSTRACT: Avalanche control by explosives is among the key temporary preventive measures and fixed avalanche control installations are frequently installed today. Hitherto, little is known about weak layer failure and crack propagation due to an explosion. In the winter 2013-2014 we performed field ex-periments on a flat study site. We triggered slurry explosive charges ranging from 4.25 to 5 kg as used in avalanche control at different heights above the snow surface. At three different distances from the point of explosion we measured surface air pressure and accelerations within the snowpack at various depths. Cameras were placed in the snow pits for recording weak layer failure and crack propagation and to monitor the snowpack deformation by particle tracking velocimetry. We assessed whether weak layer fail-ure occurred and if so whether it was caused by crack propagation or the direct impact of the air pressure wave above the point of observation (pit). We compared these results to the data recorded by the accel-erometers and microphones to obtain magnitudes required to cause weak layer failure in a given snow-pack. First results show loading conditions using explosives required to fail a weak layer given a certain snowpack