Mechanical properties of artificial snow

Sammanfattning: Mechanical properties of snow have been a subject of research since the mid-20th century. Theresearch done is based on natural snow. During the last decades the winter business industryhas been growing and also the interest for constructing buildings and artwork of snow. Suchconstructions are generally built using artificial snow, i.e. snow produced by snow guns. Up tothe present constructions of snow are designed based on knowledge by experience. Only minorscientific studies on artificial snow and its properties has been published. Hence it is ofimportance to investigate material properties for artificial snow.A survey of current state of the art knowledge of properties for natural snow was done andbasic material properties for different qualities of artificial snow were investigated. Strengthand deformation properties for artificial snow were evaluated through uniaxial compressivetests where cylindrical test specimens were subjected to different constant deformation rates.The results show that artificial snow at low deformation rates will have a plastic deformationbehavior where the initial deformation will cause a hardening of the snow structure. At higherdeformation rates brittle failure may occur. For artificial snow with a homogeneous and finegrained structure the deformation behavior was found to change from plasticity to brittleness ata certain critical deformation rate. Artificial snow with coarse grained structure was found to bebrittle giving unstructured results independent of the load level.Four point loading was applied on beams of artificial snow to study creep deformation, bendingstrength and to determine the ultimate load for the different snow qualities. The results showedcoarse grained artificial snow underwent relatively small creep deformations. Both the creepbehavior and the ultimate strength varied randomly at the same applied load. Large plasticdeformations were observed with the fine grained artificial without any failure of the beams.The ultimate load was relatively high and repeatable results were achieved for all test.Previous presumptions that coarse grained artificial snow with high density would have highstrength and were not confirmed by the experiments performed on different qualities ofartificial snow. The performed tests indicate that fine grained artificial snow of lower densityhave more predictable strength properties of equally high or higher magnitude as for coarsegrained artificial snow. The plastic deformations were however higher for the fine grainedartificial snow. High deformations are not favorable for structures which should maintain theshape during the winter season. When designing constructions of snow both strength anddeformation properties should be taken into account.