Properties of snow with applications related to climate change and skiing
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Snow has been a subject of research since the mid-20th century. Research on mechanical propertiesof snow started as an o-shoot of soil mechanics, where methods, tools and instrumentsused often are the same. However, during the last decades the winter business industry hasbeen growing requiring a number of new elds of research. The aim with this PhD thesis is toinvestigate and contribute to solutions of some of the new research problems appearing in thisarea.Machine-made snow is commonly used for buildings and artwork of snow. Only minorscientic studies of machine-made snow and its properties have been published. Therefore,mechanical properties of machine-made snow were investigated. Strength and deformationproperties were evaluated through uniaxial compressive tests where cylindrical test specimenswere subjected to dierent constant deformation rates. Creep deformation, bending strengthand ultimate load were also evaluated through beam tests. The results showed that the deformationrate is crucial if the snow will deform plastically or if brittle failure will occur. Thegrain size and structure of the snow had a strong inuence on the strength properties.Snow is a constantly changing material with a large variety of grain sizes and shapes.Therefore it is of importance to classify snow. Classication of snow can be done using dierentmethods depending on the property that is to be investigated. Several non-contact detectionmethods to evaluate snow properties exist. In this thesis, spectral reectance measurementswere performed to investigate liquid water content in snow using two dierent systems, a spectrometerand an optical sensor called Road Eye. The Road Eye sensor was also used to classifysnow in cross-country ski tracks. This method enables a fast classication of a complete trackwhere dierent types of snow can be distinguished.The properties of a ski track and the characteristics of the snow determine the type ofskis that should be selected for optimum sliding properties. Cross-country skis have dierentmechanical properties, which to a large extent can be evaluated from the span curve of theski. Depending on the skiing style, the skier's skills, terrain and track conditions dierent skiproperties are required, which is particularly important for competitive skiing. Span curves ofcross-country skis were measured using a digital instrument called Skiselector. Results from theinvestigations showed that skis within the same pair may have signicantly dierent properties.Moreover, temperature inuences the span curve and thus the mechanical properties of the skis.Therefore, skis should be measured at a temperature close to where they are aimed to be used.Field tests of skis with similar span curves but dierent ski base topography were tested duringwet and cold snow conditions. The results indicate that dierent topographies are preferableduring dierent snow conditions.Due to the climate change, winters have become shorter and warmer with less natural snow.To compensate for the lack of natural snow, ski resorts and other stakeholders produce machinemadesnow in order to run their business. Storing snow in insulated piles is an alternative and sometimes a complement to snow production. Studies on stored snow show that the surfacearea of the pile should be minimized in order to reduce the melt rate. Furthermore, the pileshould be covered with a suciently thick insulating layer, preferably with good evaporationproperties. Theoretical calculations can be used to estimate the amount of snow that melts andto predict the eciency of dierent materials as thermal insulation on snow. These calculationscoincide well with experiments performed in northern Sweden where snow melt was measured.This PhD thesis consists of ve publications and an introduction to this area which inparticular puts these publications into a more general frame.
Place, publisher, year, edition, pages
Luleå tekniska universitet, 2016.
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Research subject Soil Mechanics
IdentifiersURN: urn:nbn:se:ltu:diva-59846ISBN: 978-91-7583-731-4ISBN: 978-91-7583-732-1 (pdf)OAI: oai:DiVA.org:ltu-59846DiVA: diva2:1038717
2016-12-20, F1031, Luleå tekniska universitet, Luleå, 10:00
Knutsson, Sven, ProfessorPersson, Lars-Erik, Professor