Load-controlled test apparatus for snow

Natural dry-snow slab avalanches start with a failure at a weak snow layer. In order to understand the mechanical behaviour and the failure mechanism, we designed an experimental setup to perform loading experiments with homogeneous and layered snow samples under controlled conditions in a cold laboratory. We here present our loading apparatus where the snow sample can be tilted by a “slope angle” and is loaded by an increasing weight analogous to a snowfall. The force and the global displacement are measured with a force and two displacement sensors, respectively. The local displacement can be computed with a particle image velocimetry algorithm (PIV). Additionally, we record acoustic emissions (AE) to monitor the damage (breaking of bonds) in the snow sample before catastrophic failure. To demonstrate the capability of the system we present preliminary results with both homogeneous and layered snow samples. The AE count rate increased before fracture, as the samples progressively weakened. For the layered samples we measured a concentration of strain within the weak layer.