Mechanical properties of artificial snow

Sammanfattning: Mechanical properties of snow have been a subject of research since the mid-20th century. The research done is based on natural snow. During the last decades the winter business industry has been growing and also the interest for constructing buildings and artwork of snow. Such constructions are generally built using artificial snow, i.e. snow produced by snow guns. Up to the present constructions of snow are designed based on knowledge by experience. Only minor scientific studies on artificial snow and its properties has been published. Hence it is of importance to investigate material properties for artificial snow. A survey of current state of the art knowledge of properties for natural snow was done and basic material properties for different qualities of artificial snow were investigated. Strength and deformation properties for artificial snow were evaluated through uniaxial compressive tests 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 deformation behavior where the initial deformation will cause a hardening of the snow structure. At higher deformation rates brittle failure may occur. For artificial snow with a homogeneous and fine grained structure the deformation behavior was found to change from plasticity to brittleness at a certain critical deformation rate. Artificial snow with coarse grained structure was found to be brittle giving unstructured results independent of the load level. Four point loading was applied on beams of artificial snow to study creep deformation, bending strength and to determine the ultimate load for the different snow qualities. The results showed coarse grained artificial snow underwent relatively small creep deformations. Both the creep behavior and the ultimate strength varied randomly at the same applied load. Large plastic deformations 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 high strength and were not confirmed by the experiments performed on different qualities of artificial snow. The performed tests indicate that fine grained artificial snow of lower density have more predictable strength properties of equally high or higher magnitude as for coarse grained artificial snow. The plastic deformations were however higher for the fine grained artificial snow. High deformations are not favorable for structures which should maintain the shape during the winter season. When designing constructions of snow both strength and deformation properties should be taken into account.