Abstrakt
Flotation devices are more and more frequently used. Their efficacy has already been demonstrated by field tests (Tschirky and Schweizer 1996; Kern et al. 2002; Meier and Harvey 2010) and retrospective studies (Tschirky et al. 2000; Brugger and Falk 2002; Brugger et al. 2007).
There are several systems on the market that differ in release mechanism and balloon shape. In general three different balloons shapes exist.
In the winter season of 2011/2012 a pilot study of three differently shaped floatation devices was made for the first time. The aim of this study was to investigate the behavior of each inflated system during an avalanche event.
Three human-weighted dummies were positioned on the slope and an avalanche was triggered with explosives. Several video cameras, installed on and beside the avalanche path, recorded the movement and final deposition of the dummies.
The track of each dummy was measured with high accuracy GPS (<1m) and avalanche flow properties (flow height, velocity and pressure) were simulated with the Rapid Mass Movements (RAMMS) tool. The video material together with the GPS measurements and numerical simulation was used to analyze the behavior of different floatation systems.
The burial grade differed for each dummy and none of them were completely or partially-critically buried. From this pilot study we cannot draw conclusions about the efficacy of the different shapes; further tests are needed for an in-depth comparison of the devices.