Modelling Snow Slab Release Using a Temperature-Dependent Viscoelastic Finite Element Model with Weak Layers

A two-dimensional thermo-mechanicalplane-strain finite element model forsnow is presented. Snow is modeled asa two component porous medium consisting ofa solid ice matrix and interstitial pore air.The ice and air phases are not always in thermalequilibrium. Therefore, heat transport is governedby two non-stationary energy conservation equationswhich are coupled by free convection heat exchangesat the interfacial ice-air boundary. The icematrix deforms viscoelastically according to anexperimentally-based temperature dependent constitutivelaw. Creep deformation rates are governed by a powerlaw with a density dependent exponent n.The highly nonlinear character of the mechanical modelis illustrated by simulating snowcovers with layersof variable height and density. Weak layerinterfaces – believed to be the location of initiationof snow slab fracture – are modeled using specialfinite elements which transfer normal stresses buthave little or no shear resistance. Stress andstrain-rate concentrations at the boundaries ofweak zones are calculated and compared withbrittle fracture strain-rates.