[{"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."},{"pid":"wsl:37249","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37249","citation":{"WSL":"Boaga J., Pavoni M., Bast A., Weber S. (2024) Brief communication: on the potential of seismic polarity reversal to identify a thin low-velocity layer above a high-velocity layer in ice-rich rock glaciers. Cryosphere. 18(7), 3231-3236. https://doi.org/10.5194/tc-18-3231-2024"},"doi":"10.5194/tc-18-3231-2024","abstract":"Seismic refraction tomography is a commonly used technique to characterise rock glaciers, as the boundary between unfrozen and ice-bearing layers represents a strong impedance contrast. In several rock glaciers, we observed a reversed polarity of the waves refracted by an extended ice-bearing layer compared to direct-wave arrivals. This phase change may be related to the presence of a thin low-velocity layer (LVL), such as fine- to coarse-grained sediments, above a thicker ice-rich layer. Our results are confirmed by the modelling and analysis of synthetic seismograms to demonstrate that the presence of a low-velocity layer can produce a polarity reversal on the seismic gather."},{"pid":"wsl:36687","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:36687","citation":{"WSL":"Bobillier G., Bergfeld B., Dual J., Gaume J., van Herwijnen A., Schweizer J. (2024) Numerical investigation of crack propagation regimes in snow fracture experiments. Granul. Matter. 26(3), 58 (15 pp.). https://doi.org/10.1007/s10035-024-01423-5"},"doi":"10.1007/s10035-024-01423-5","abstract":"A snow slab avalanche releases after failure initiation and crack propagation in a highly porous weak snow layer buried below a cohesive slab. While our knowledge of crack propagation during avalanche formation has greatly improved over the last decades, it still remains unclear how snow mechanical properties affect the dynamics of crack propagation. This is partly due to a lack of non-invasive measurement methods to investigate the micro-mechanical aspects of the process. Using a DEM model, we therefore analyzed the influence of snow cover properties on the dynamics of crack propagation in weak snowpack layers. By focusing on the steady-state crack speed, our results showed two distinct fracture process regimes that depend on slope angle, leading to very different crack propagation speeds. For long experiments on level terrain, weak layer fracture is mainly driven by compressive stresses. Steady-state crack speed mainly depends on slab and weak layer elastic moduli as well as weak layer strength. We suggest a semi-empirical model to predict crack speed, which can be up to 0.6 times the slab shear wave speed. For long experiments on steep slopes, a supershear regime appeared, where the crack propagation speed reached approximately 1.6 times the slab shear wave speed. A detailed micro-mechanical analysis of stresses revealed a fracture principally driven by shear. Overall, our findings provide new insight into the micro-mechanics of dynamic crack propagation in snow, and how these are linked to snow cover properties."},{"pid":"wsl:37843","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37843","citation":{"WSL":"Bobillier G., Fees A., Lombardo M., Schöttner J., Cabrera M., van Herwijnen A., … Schweizer J. (2024) Towards an improved understanding of glide-snow avalanche release: interface shear cold laboratory tests. 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. 745-749. "},"doi":"","abstract":"Glide-snow avalanches involve significant volumes of moving snow and present a major challenge to infrastructure in snow-covered mountain regions. Their initiation consists of a sequence of processes that remains poorly understood. It is conceptualized as starting with a loss of friction along the snow-ground interface due to the presence of liquid water. To shed more light on the effect of liquid water at the snow-ground interface on friction, we tested snow samples on a temperature-controlled substratum in a cold laboratory for different conditions of roughness and snow liquid water content (LWC). We performed 51 interface shear tests, analyzed the stress-displacement behavior, and studied the effect of interfacial water on the friction angles (static and kinetic). A sort of stick-slip behavior was observed on lubricated glass. On a dry and rough surface, the snow failed across the sample and no sliding occurred at the interface. Under dry conditions on a smooth surface or lubricated conditions on a rough surface, a strain-softening behavior with an interfacial strength was observed. For the tests where the frictional strength was exceeded, the friction angle, both static and kinetic, showed no dependence on the liquid water content. In the future, we plan to refine and extend the experimental setup to investigate snow compaction and analyze the effect of snowpack properties on gliding behavior."},{"pid":"wsl:37823","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:37823","citation":{"WSL":"Borner J., Rusterholz P., Margreth S., Bartelt P. (2024) Measuring snow pressure forces on supporting structures using low-cost strain gauges. 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. 1127-1132. "},"doi":"","abstract":"Predicting snow pressure forces exerted by the snow cover on structures on sloping terrain remains a challenging task. Especially with the increasing interest in alpine solar parks with little financial margin for safety, the demand for monitoring systems as well as accurate prediction models for snow pressure acting on slender supports is higher than ever before. This paper presents an experimental setup for measuring the reaction forces of the snow cover on various support and pressure bars of an snow supporting structure made of steel using strain gauges. In combination with the material properties and the entire static system of the structure, we can back calculate the pressure exerted by the snow cover. In order to interpret the measured forces correctly, additional field campaigns in winter are important to determine the local snow distribution, the snow temperature and the density of the snow cover. We extensively address challenges encountered during the measurement campaign, including eliminating temperature-induced strain, amplifying the signal in low strain ranges, handling combined bending and restraint stresses, and protecting sensors and cables against settlement and creep forces. Having overcome these challenges, the key advantages of using strain gauges are that the system is cost effective and non-invasive and therefore allows rapid installation on a large number of sections of interest. We discuss results obtained from the first winter of the campaign (2023/2024). The high measurement frequency of one measurement every five minutes provides an insight into the daily cycle of the forces. Most notably, on warm spring days with cold nights, we observed a continuous increase in forces starting at sunset, peaking at sunrise, followed by a rapid decline thereafter. The measurement data can be used to calibrate newly developed viscoelastic 3D snow creep models with various constitutive laws for the prediction of creep and glide forces on supporting structures. These models as well as the presented experimental setup show great potential to further optimise the design of supporting structures and installations of alpine solar parks."},{"pid":"wsl:36278","object_url":"https://www.dora.lib4ri.ch/wsl/islandora/object/wsl:36278","citation":{"WSL":"Bottero A., Moos C., Stritih A., Teich M. (2024) Editorial: impacts of global change on protective forests in mountain areas. Front. For. Glob. Change. 7, 1375285 (3 pp.). https://doi.org/10.3389/ffgc.2024.1375285"},"doi":"10.3389/ffgc.2024.1375285","abstract":""}]

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