"Snow avalanche is the most frequent type of slope failure in mountainous areas of the world. In total, approximately 15% of Europe’s and 6% of Earth’s land may be considered as avalanche prone-areas. Avalanches claim hundreds of lives annually worldwide and there have been historical cases with death tolls between hundreds and thousands of people during one event or winter season.One of the main goals of snow avalanche research is to forecast natural or induced mechanical failure of a sloping layered snowpack in order to estimate potential damage to human activities in mountain regions and to be able to conduct risk-oriented planning. The deadliest type of snow avalanches are slab avalanches, which start from a failure of a cohesive horizon of snow, or “slab”, underlaid by a so called “weak layer”. The nature of weak layer deformation is considered the crux of slab stability. At present, the origin of initial failure and the failure process in the weak layer remain poorly understood.In order to contribute to development of a mechanical model of snow fracture, and to provide tools to estimate initial conditions for avalanche dynamic models for hazard mapping and risk management, we propose to investigate the mechanical behavior of weak layers and their relationship to slope-scale instability.Key objectives of the study are: 1) To design instrumental apparatus for both cold laboratory and in situ field work to study the mechanical behavior of snow weak layers. 2) To obtain, through experiment, fully operational mechanical laws of different types of alpine snow weak layers. 3) To critically review existing modeling approaches for weak layer and slab in order to couple best existing practices with experimentally obtained results. 4) To relate the micro and meso-scale weak layer behavior to the macro-scale slab failure by means of numerical modeling for development of a next generation numerical model describing the mechanical behavior of a snow slab on a slope."