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Temperature and Density Dependent Constitutive Behaviour of Snow: Laboratory Experiments and Constitutive Equations
This joint-venture project between the IGT and the Swiss Federal Institute for Snow and Avalanche Research (SLF) Davos is based on the scientific and technical know how accumulated during the first joint-venture project started in 1996 for a duration of four years (see the report: “Field and laboratory experiments to determine the mechanical properties of snow”). The aims of this three years project started in august 2000 are: (1) To investigate both the temperature and density dependent ductile viscoelastic and the brittle behaviour of snow in compression and in tension under monoaxial and triaxial test conditions. (2) To investigate the temperature and density dependent acoustic emission response in relation to the macroscopic stress-strain behaviour of snow. (3) To develop both a one-dimensional and a three-dimensional constitutive equation in order to describe the density and temperature dependent viscoelastic behaviour of snow. The constitutive equation will be implemented in an instationary numerical model, which simulates the stress, strain and strain-rates distribution over time in the snowpack. The laboratory experiments were conducted both deformation and load controlled with different snow densities (from 200 to 400 kg/m3) and confining pressures (0 to 40 kPa), at different temperatures (-20 to –2 °C) and strain-rates (10-7 s-1 to 10-2 s-1). The test results show the high non-linear viscoelastic behaviour of snow. Therefore the constitutive equations are based on non-linear spring-dashpot-models. The newly developed constitutive equations will be used in two- and later three-dimensional numerical simulation of avalanche formation based on the numerical application of fracture mechanics and in the determination of snow pressure on avalanche defence structures.
Authors:Scapozza, Carlo and Bucher, Felix and Amann, Peter