[{"pid":"wsl:37989","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37989","citation":{"WSL":"Bartelt P., Stoffel L., Christen M., Bühler Y. (2024) Grain flow theory and snow avalanche rheology. In K. Gisnås, P. Gauer, H. Dahle, M. Eckerstorfer, A. Mannberg, & K. Müller (Eds.), Proceedings of the international Snow Science Workshop 2024. Oslo: Norwegian Geotechnical Institute. 360-365. "},"doi":"","abstract":"This paper explores the application of grain flow theory to snow avalanche dynamics, focusing on the interrelation between shear stress and fluctuation energy. The study employs a system of differential equations to model the mean velocity (U) and fluctuation energy (R) within snow avalanches. The key physical constraint highlighted is the relationship dR · S = −R₀ · dS, which provides a physical constraint on the omplex relationship between avalanche shear stress and the production of fluctuation energy. When fluctuation energy is produced by shearing, it generates not only directionless random kinetic energy but also directional energy fluxes that alter the configuration of the granular ensemble, leading to changes in shear stress. The analysis of the R-U phase plane reveals that avalanche behavior can be characterized by equilibrium points that shift with slope angle, highlighting the role of fluctuation energy in determining the flow regime. The R-U phase plane not only advances our understanding of avalanche dynamics but also facilitates the examination of flow regime transitions, driven by changes in the potential energy of the granular ensemble, and the emergence of different avalanche types."},{"pid":"wsl:37776","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37776","citation":{"WSL":"Bartelt P., McArdell B., Bühler Y., Graf C. (2024) Zweiphasenmodellierung von Murgängen für die Überprüfung von Schutzmassnahmen. In I. Schalko, D. Farshi, & A. Badoux (Eds.), WSL Berichte: Vol. 155. Fachtagung Wildbäche 2024: Modellierung von Wildbachprozessen. Birmensdorf: Eidg. Forschungsanstalt für Wald, Schnee und Landschaft WSL. 49-58. https://doi.org/10.55419/wsl:37776"},"doi":"10.55419/wsl:37776","abstract":"Die Ereignisse Ende Juni 2024 haben gezeigt, dass neue, konsistente Methoden zur Bewertung von Murgang- Schutzmassnahmen benötigt werden. Die Wahl geeigneter Gefahrenszenarien und die Modellierung der Murgänge sind zentral, um Schutzmassnahmen effektiv zu planen. Ein neues numerisches Zwei-Schichten-Modell, das feste und flüssige Phasen trennt, wurde eingesetzt, um die komplexe Dynamik von Murgängen besser nachzubilden. Zwei Fallstudien im Val Greva (GR) und in Sorte (GR) zeigen realistische Ergebnisse und verdeutlichen die Bedeutung der Erosion für die Mobilität von Murgängen. Die Ergebnisse weisen darauf hin, dass künftige Schutzmassnahmen differenziertere Informationen zum Fliessverhalten erfordern. Eine stetige Verbesserung der Modelle durch eine gründliche Analyse vergangener Ereignisse ist entscheidend, um die Genauigkeit und Zuverlässigkeit der Gefahrenbewertung zu gewährleisten."},{"pid":"wsl:37532","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37532","citation":{"WSL":"Bast A., Bründl M., Phillips M. (2024) CCAMM - A research program for studying the impacts of climate change on mass movements in alpine regions. In J. Schneider (Ed.), Interpraevent 2024. Conference proceedings. Klagenfurt: Interpraevent. 37-39. "},"doi":"","abstract":"According to various projections, climate change will alter the disposition for alpine mass movements, as well as their dynamics and the interaction of gravitational processes in process cascades. This will change the risks that people living in mountain regions are exposed to. The research program CCAMM - Climate Change Impacts on Alpine Mass Movements – initiated by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, fosters inter- and transdisciplinary research and thus addresses a socially relevant question and provides an important contribution to climate change adaptation of society. In this contribution, we provide an overview of the 22 projects and the envisioned outreach activities in 2025."},{"pid":"wsl:37174","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37174","citation":{"WSL":"Bast A., Kenner R., Phillips M. (2024) Short-term cooling, drying, and deceleration of an ice-rich rock glacier. Cryosphere. 18(7), 3141-3158. https://doi.org/10.5194/tc-18-3141-2024"},"doi":"10.5194/tc-18-3141-2024","abstract":"Observations in the European Alps show a long-term rise in rock glacier velocities, which is often associated with increased air and ground temperatures and, more recently, water content. Long-term rock glacier acceleration is superimposed by a high interannual variability of the velocity with a particular gap in the quantitative assessment of the role of water in rock glacier kinematics and the factors leading to short-term rock glacier deceleration.
To address this research gap, we drilled three vertical boreholes in the Schafberg rock glacier, Swiss Alps, in August 2020. We documented their stratigraphy and equipped one of the boreholes with temperature sensors and piezometers and the other two with cross-borehole electrodes for electrical resistivity tomography measurements. Rock glacier velocities were determined using repeated terrestrial laser scans. Using data from an additional borehole and nearby weather stations and ground surface temperature sensors, we analysed the interactions between meteorological and subsurface conditions during a rock glacier deceleration period, from January 2021 to July 2023.
Our findings show that a lowering of the water content in rock glacier shear horizons is crucial for interannual rock glacier deceleration. The impact of the snowpack, both as an insulator and as a water source, is significant for rock glacier kinematics. Winters with little snow and relatively dry summers appear to be ideal for rock glacier cooling and drying, leading to deceleration. Summer heat waves have limited impact on rock glacier velocity if they are preceded by snow-poor winters.
Our study uses an innovative combination of borehole data to gain insights into rock glacier temperatures and water contents, allowing us to detect relative changes in ice and/or water contents in ice-rich permafrost. The monitoring techniques used have the potential to contribute to a better understanding of the main drivers of rock glacier kinematics and water availability."},{"pid":"wsl:37737","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37737","citation":{"WSL":"Bebi P., Wohlgemuth T. (2024) Herausforderungen bei der Erhaltung von Schutzwäldern. Montagna Z. Berggeb. 34(8/9), 12-13. "},"doi":"","abstract":"Gebirgswälder erfüllen zahlreiche Funktionen. Sie sind Lebensraum für Pflanzen- und Tierarten, tragen zur Kohlenstoffspeicherung bei, laden zur Erholung ein und liefern Bau- und Energieholz. Unverzichtbar ist ihre Rolle als natürlicher Schutz vor Steinschlag, Lawinen und Erdrutschen. Seit dem Forstpolizeigesetz von 1876, das den Grundsatz der Nachhaltigkeit einführte, haben Fläche und Dichte der Bergwälder zugenommen. Heute sind diese Wälder im Rahmen des globalen Wandels einer neuen Dynamik unterworfen, in welcher wärmere Temperaturen, Dürren und Winterstürme, aber auch Holzpreise grosse Herausforderungen darstellen, die Waldfunktionen zu erhalten."},{"pid":"wsl:37999","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37999","citation":{"WSL":"Blatny L., Gray J.M.N.T., Gaume J. (2024) A critical state μ(I)-rheology model for cohesive granular flows. J. Fluid Mech. 997, A67 (46 pp.). https://doi.org/10.1017/jfm.2024.643"},"doi":"10.1017/jfm.2024.643","abstract":"The dynamic behaviour of granular media can be observed widely in nature and in many industrial processes. Yet, the modelling of such media remains challenging as they may act with solid-like and fluid-like properties depending on the rate of the flow and can display a varying apparent friction, cohesion and compressibility. Over the last two decades, the μ(I)-rheology has become well established for modelling granular liquids in a fluid mechanics framework where the apparent friction μ depends on the inertial number I. In the geo-mechanics community, modelling the deformation of granular solids typically relies on concepts from critical state soil mechanics. Along the lines of recent attempts to combine critical state and the μ(I)-rheology, we develop a continuum model based on modified cam-clay in an elastoplastic framework which recovers the μ(I)-rheology under flow. This model permits a treatment of plastic compressibility in systems with or without cohesion, where the cohesion is assumed to be the result of persistent inter-granular attractive forces. Implemented in a two- and three-dimensional material point method, it allows for the trivial treatment of the free surface. The proposed model approximately reproduces analytical solutions of steady-state cohesionless flow and is further compared with previous cohesive and cohesionless experiments. In particular, satisfactory agreements with several experiments of granular collapse are demonstrated, albeit with shear bands which can affect the smoothness of the surface. Finally, the model is able to qualitatively reproduce the multiple steady-state solutions of granular flow recently observed in experiments of flow over obstacles."}]

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