The snow study center (CEN, CNRM-GAME, Meteo-France/CNRS) and the team “Torrent erosion, snow and avalanches” of Irstea are now seeking for a motivated and talented PhD student to investigate the link between snow microstructure and its mechanical behavior.The project involves numerical modeling based on 3D micro-tomgraphic data and field measurement of the snowpack. The PhD is fully funded and will take place in Gerenoble, France. Expression of interest or request for information should be made to Dr. Pascal Hagenmuller (pascal [dot] hagenmuller [at] meteo [dot] fr) as soon as possible. Details of the project can be found below. *Title*: Investigation of the relationship between snow microstructure and its mechanical behavior *Supervision*:-Pascal Hagenmuller, Researcher, CNRM-GAME/CEN-Guillaume Chambon, Researcher, Irstea *Context* 72 1024×768 Characterizing the complex microstructure of snow and its mechanical behaviour is a major challenge for avalanche forecasting. Indeed, the snow cover stratigraphy, i.e., the vertical arrangement of different snow microstructural patterns, has long been recognized as the key contributing factor for snow avalanche formation.
In particular, the presence of a collapsible weak layer below a relatively cohesive layer leads to avalanche-prone situations. Usually snow mechanical properties are parameterized phenomenologically as functions of density and subjective classes of snow types, which lacks to capture the variety and continuum of microstructural patterns. Thanks to X-ray tomography, it is now possible to capture high-resolution three-dimensional images of the snow microstructure. These images have recently been used as inputs of numerical mechanical models in order to decipher partially the link between the snow microstructure and its mechanical properties. In parallel, snow penetrometers (e.g. SP1, SMP) measuring the penetration resistance of the snowpack with a micrometric resolution are under active development. These field measurements provide qualitative information about the snowpack, but a way to derive mechanically-relevant structural properties from this data is still open.
Objective: The aim of this thesis is (1) to better quantify the link between snow microstructure and its mechanical properties controlling the overall snowpack stability, with the help of micro-tomographic data, and (2) to provide methods to estimate the identified relevant microstructural indicators with accessible field measurements. To this end, numerical mechanical experiments based on the Discrete Element Method (DEM) will be conducted on a large number of 3D snow images.
Two main types of loading conditions will be considered: combined shear and compression, and penetrometer tests. From these numerical experiments, quantitative parameterizations of the mechanical properties using microstructural indicators will be formulated. The numerical penetrometer tests will provide a way to link the developed parameterizations to field measurements and to evaluate the predictive capabilities of the proposed model.
This project is an important step to improve the avalanche forecasting model (SAFRAN-SURFEX/Crocus-MEPRA) and to better quantify the initial snow volume involved in avalanche releases.
Candidate: The candidate must hold a Master degree in geomechanics or material sciences. This project requires skills in numerical modelling (discrete element, finite element) and image processing (3D tomographic images). Field and cold-lab measurements are also part of the project and require specific motivations for cold and snow.
Expression of interest or request for information should be made to Pascal Hagenmuller (pascal.hagenmuller@meteo.fr) as soon as possible. To apply, please provide the following documents: – CV – Motivation letter – Copy of the obtained degrees (bachelor and Master) with the grades – Copy of the Master thesis
Closing date: 2016-08-10