Effects of flow regime and sensor geometry on snow avalanche impact-pressure measurements

• Main Authors: Baroudi, D., Sovilla, B., Thibert, Emmanuel
• Other Authors: Érosion torrentielle, neige et avalanches (UR ETGR (ETNA)), Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF), Aalto University, WSL INSTITUTE FOR SNOW AND AVALANCHE RESEARCH SLF DAVOS DORF CHE, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2011
• Subjects: FLOW REGIME; LIMIT STATE ANALYSIS; SHEAR FAILURE; DEAD ZONE; VALLEE DE LA SIONNE; AVALANCHE IMPACT PRESSURE; [SDE]Environmental Sciences; Journal of Glaciology
• Online Access: https://hal.inrae.fr/hal-02595096

International audience Impact pressures of snow avalanches have been measured at the Swiss Vallée de la Sionne experimental test site using two kinds of sensor placed at different locations in the avalanche flow. Pressures measured in a fast dry-snow avalanche and a slow wet-snow avalanche are compared and discussed. The pressures recorded using the two types of sensor in the dense flow of a dry-snow avalanche agree well, showing negligible dependence on the measurement device. On the other hand, significantly different pressures are measured in the slow dense flow of a wet-snow avalanche. This is attributed to the slow drag and bulk flow of this type of avalanche, leading to the formation and collapse of force-chain structures against the different surfaces of the sensors. At a macroscopic scale, limit state analysis can be used to explain such a mechanism by a shear failure occurring between freely flowing snow and a confined snow volume against the sensor, according to a Mohr Coulomb failure criterion. The proposed model explains (1) how impact pressure can be up to eight times higher than hydrostatic snow pressure in wet cohesive slow avalanches and (2) its dependence on sensor geometry.