The friction of tyres on roads has been of practical importance for many years with nearly 80% of terrestrial traffic making use of rubber tyres. Tyres provide the grip required for vehicle acceleration, braking and cornering. In order for a tyre to grip on a snow covered surface friction mechanisms such as “ploughing”, (where sharp tread block edges dig into and break bonds between the snow grains) and fluid film lubrication must be considered. These are not present when a tyre interacts with tarmac. In addition metamorphism of the snow over time can result in variations of the structure and mechanical properties, this can occur rapidly especially when dealing with temperatures close to snows melting point. When full car-scale outdoor testing is carried out the snow conditions cannot be controlled and vary daily. This means the snow properties must be measured every day so that any observed variations in friction can be attributed to the tyres rather than the snow. At present the simple measurements being carried out on the snow tracks have not proved sufficient to pick up on the variations in the snow. This leads to inconsistent results: one tyre behaves differently on two different days, even though the snow was measured to be the same. This has resulted in the need for further study of the way snow variations influence the grip of winter tyres. The primary aim of this study is to identify which snow properties contribute to the friction of tyres on snow and be able to estimate the friction from measurements of snow properties. This work is the first comprehensive study to combine: multiple snow properties, microstructure characterisation, measurement of friction behaviour and different snow (both artificial and natural). In order to study the way snow affects the grip of winter tyres, methods of manufacturing artificial snow with consistent mechanical properties and microstructure are used. A method of blending ice chips (a solid state fracturing process) and compressing the resulting snow to form a test track was developed during a previous PhD carried out in our group. An alternate snow microstructure was created by using an established process of creating snow by vapour deposition. The process was simplified and downscaled, the resulting snow consisted of large dendritic grains, very different to the blended ice chips. Both snows were pressed in identical manners to create snow testing tracks. In addition, natural snow collected from the field was tested to compare with the artificial snow. In order to investigate how the variations in the snow affected the friction of tyres extensive testing was carried out in a cold room using a linear tribometer, using procedures established in previous studies. Two analytical rubber samples were used to investigate the friction, a rounded edge sample and a siped sample. Testing was carried out at -10°C at speeds of 0.01m/s, 0.1m/s and 1m/s. A significant part of this PhD involved the development of new methods and equipment which have not been used to study snow in this way before. In order to characterise mechanical properties, shear testing, compression testing and cohesion testing were carried out. To investigate snow microstructure, surface profilometry, microscopy and X-ray microtomography were used. Correlating the changes observed in snow characteristics with the changes recorded in the coefficient of friction has allowed the development of an empirical equation. This can be used to predict the coefficient of friction of a given snow based on three relatively simple snow measurements: a compression test to calculate the effective modulus, a roughness measurement to calculate the peak count density and a snow penetration test. For the first time this study allows us to use the empirical equation to estimate the relative contributions of the ploughing and surface friction mechanisms to the total friction. This allows the comparison of full car-scale test data as it is now possible to account for variations in the snow test tracks.

Vegetation cover of 24 ski slopes both with artificial and natural snow was studied; on each slope 5 phytocenological relevés measuring 4 x 4 metres were taken. A method of direct gradient analysis (RDA) was used to detect differences in composition of phytocenological reléves on the ski slopes with natural or artificial snow. However, no impact of use of artificial snow on vegetation was identified. During the winter season of 2009 and of 2010 samples of artificial and natural snow were taken for chemical analyses. The chemical composition differed significantly; artificial snow contained more NO3-, SO42- and Ca2+ ions and its pH was more alkaline in comparison with natural snow.

Vegetation cover of 24 ski slopes both with artificial and natural snow was studied; on each slope 5 phytocenological relevés measuring 4 x 4 metres were taken. A method of direct gradient analysis (RDA) was used to detect differences in composition of phytocenological reléves on the ski slopes with natural or artificial snow. However, no impact of use of artificial snow on vegetation was identified. During the winter season of 2009 and of 2010 samples of artificial and natural snow were taken for chemical analyses. The chemical composition differed significantly; artificial snow contained more NO3-, SO42- and Ca2+ ions and its pH was more alkaline in comparison with natural snow.

Increased temperatures, changed snow conditions, increasing demand for skiing and other winter sports lead to increased demand and production of artificial snow. Besides the positive aspects of artificial snow, it is important to understand potentially negative effects of artificial snow on the environment and vegetation. This study investigated the differences between artificial snow and natural snow in two adjacent ski slopes. This was done by measuring and comparing the snow depth, duration of the snow cover, snow density, and ground vegetation between the slopes. Snow depth and density showed differences between artificial snow and natural snow. The artificial snow cover stayed about 11 days longer than the natural snow. A few variations in the vegetation were also found; earlier flowering and more species and colors in the natural snow slope compared to in the slope using artificial snow. Therefore, it is clear that there is a difference between artificial snow and natural snow, and that this results in effects on the environment, but it is difficult to assess to what extent and how large the negative impact is. For more general conclusions, I think it is important to study the vegetation under artificial snow during a longer period and in several areas.

This diploma thesis deals with the issue of energy requirements for operation of indoor ski slopes. The first part is dedicated to research of snow making, cooling and construction methods of ski halls along with the examples of specific projects. In the second part, the aim was to design a ski hall with specific geometry and insulation and then define energy losses of such building. Subsequently, all related energy flows were calculated, which led to the determination of the required cooling capacity. Based on this, the cooling cycle was calculated and the overall electricity demand for the operation of the ski hall during the year was set. In the third part, three options for covering electricity needs are evaluated and at the same time they are compared in terms of financial costs during the year.

This thesis is focused on members of two groups, rangers and ski lift operators of the area of Krkonoše mountains. In Krkonoše National Park there si a huge gain of using artificial snow lately, which is globally supposed to be kind of adaptation on climatic changes. It leads to extension of ski season, which is livelihood for many ski lift operators. This fact evokes conflicts. Rangers say that artificial snow has negative influence on environment, such as decrease of water, biodiversity, soil etc. I have decided to find out, using a quantitative sociological method of semi-structured interviews followed by analysis, how these two groups percieve the nature and how their differnces influence negotiation of reproduction of countryside in Krkonoše mountains. Sources of my research were works of authors such as Swyngedouw, Macnaghten, Urry or Escobar. These works describe various kinds of socio-countrysides and authors try to destroy stereotype of one nature. These socio-countrysides may be the main reason for arguing about nature. This thesis extends knowledge about heretofore missing analysis of conflict between two groups of ski lift operators and rangers. Main contribution of the thesis is undertsanding to two groups dealing with the same issue, but with different perspective and opinion.

Depuis quelques années le recours à l’enneigement artificiel est de plus en plus courant dans les stations de ski des Alpes mais également dans les autres massifs français et étrangers. Cependant la production de neige nécessite l’utilisation d’un volume d’eau important, souvent pompé dans les réserves d’eau potable, les rivières, les nappes phréatiques, ou bien dans les réserves collinaires, elles-mêmes alimentées par captage des eaux de ruissellement. Or l’enneigement n’est pas le seul usage de l’eau dans les stations de sports d’hiver, et ce nouveau besoin concerne la saison hivernale lors des étiages des cours d’eau et des besoins pour les diverses activités. Depuis quelques années, cette technique fait l’objet de nombreuses controverses au sein de la communauté scientifique, politique et des populations locales, car les volumes d’eau pompés sont particulièrement importants. Notre recherche s’appuie sur des enquêtes auprès des acteurs impliqués, des observations de terrain et des mesures, à différentes échelles de travail. Deux modèles de production de neige sont confrontés : Avoriaz (France) et Champéry (Suisse). Les impacts des usages sur le fonctionnement hydrologique du bassin versant de la Dranse de Sous-Saix, sur le domaine d’Avoriaz, sont aujourd’hui limités et dans les deux stations la ressource est actuellement suffisante pour satisfaire tous les besoins. A ce jour les situations de pénuries d’eau et de conflits autour de la ressource sont rares, et sont dues à des problèmes de gestion. Un ensemble de propositions inspirées d’initiatives locales pour une meilleure gestion de la production de neige et des usages de l’eau a été proposé. / For some years now the use of artificial snow has become increasingly frequent in Alpine skiing resorts as well as in the other French and foreign massifs. Nevertheless, snowmaking calls for a large amount of water, which is often pumped from drinking water reserves, rivers, groundwater tables or else from hill water reserves, themselves supplied from surface water capture. This relatively recent practice, added to the different activities already present, is of concern for the local populations and environmental associations. For several years now, this technique has been the subject of numerous controversies within the scientific and political community and local populations. As things stand, the work performed by researchers and, more particularly, geographers is thin on the ground, because the volumes of water pumped are particularly important. Our research is based on interviews whit those involved in snow production, field observation and measures. Two model of artificial snow are confronted : Avoriaz (France) and Champéry (Switzerland). The impacts of the uses on the hydrological functioning of the Dranse de Sous Saix catchment area, in Avoriaz’s area are now limited and in both resorts, the resource is currently sufficient to satisfy all the needs. At the present time water shortages or conflicts involving the resource are unusual, and are thus due to management problems. A set of proposals inspired local initiatives for a better artificial snow management and water uses management have been proposed.

The presented diploma thesis informs about the origin, history, and benefits of technical snowmaking. It introduces what snow equipment consists of and what processes artificial snow is produced. It also shows the price of tons of snow produced from individual commercially available equipment. In the experimental part, the work deals with the calculation of droplet freezing for various input parameters of water, environment, and equipment. A sample calculation was performed for a falling water droplet from a snow lances. The droplet of discharged water was 0.3 mm in size and had a temperature of 2 ° C. The temperature of the environment was chosen to be -10 ° C. Furthermore, the trajectory of the droplet from a snow gun was determined. In the design, a specific snow pole was designed for the specified parameters, including the speed of the environment. The results were then compared with snow poles available on the market.

No description available.

Today there is a growing issue of physical inactiveness, especially during the winter period, leading to various health issues. The new-found concept of a Winter Activity Park can be a possible solution for Swedish municipalities, as a means to increase spontaneous physical activity, and improve public health, during the winter season. The concept has originated from the need for increased spontaneous physical activity during winter and includes creating a physical activity facility with the usage of artificial snow. Södertälje is a municipality where a Winter Activity Park could act as a solution in order to increase spontaneous physical activity. The aim of the study is to assess the feasibility of a Winter Activity Park, using artificial snow, in Södertälje municipality. The study sets out to determine what is technically required in order to implement a Winter Activity Park, and by including two specific sites in Södertälje (Stadsparken and Tveta Friluftsgård), it can be assessed how well each site is meeting the requirements. Additionally, the study sets out to assess what possible environmental impacts the implementation may lead to at each site, as well as determining how artificial snow should be obtained to have the least contribution to climate change. The results show that there are several technical requirements that need to be fulfilled at a site in order to implement a Winter Activity Park. Neither of the chosen sites are currently meeting all the technical requirements for a Winter Activity Park, although it is considered possible for both sites to be able to fulfil them at a later stage. By conducting an EIA, it was concluded that Tveta Friluftsgård were likely to experience less negative environmental consequences from the implementation of a Winter Activity Park, compared to Stadsparken. By calculating the carbon footprint for the alternative ways of obtaining artificial snow, it was concluded that producing snow directly at a site, using a lake as a water source, would be the most favourable, in terms of least contribution to climate change. As a final conclusion, it was determined that a Winter Activity Park is feasible in Södertälje municipality, with Tveta Friluftsgård and production directly at the site seemingly being the best way to go. However, depending on what the purpose of the Winter Activity Park is, other sites and methods of obtaining snow can be more suitable. In order to create a more comprehensive view of the feasibility and sustainability of the concept of a Winter Activity Park, future studies should investigate social and economic aspects related to the concept. / Ett växande problem i dagens samhälle är fysisk inaktivitet, främst under vinterhalvåret, vilket leder till flera olika hälsoproblem. Det nyfunna konceptet Vinterparkleken kan vara en möjlig lösning för kommuner i Sverige för att öka spontan fysisk aktivitet under vintersäsongen och därmed förbättra folkhälsan. Konceptet har sitt ursprung från behovet av ökad spontan fysisk aktivitet, och innebär införandet av en anläggning för fysisk aktivitet med användandet av tillverkad snö. Södertälje är en kommun där en Vinterparklek kan vara en möjlig lösning för att öka den spontana fysiska aktiviteten. Syftet med studien är att utvärdera genomförbarheten av Vinterparkleken med konstgjord snö i Södertälje kommun. Studien syftar till att bedöma vad som är tekniskt nödvändigt för att genomföra en Vinterparklek och två specifika platser i Södertälje (Stadsparken och Tveta Friluftsgård) är inkluderade i studien för att bedöma hur väl varje plats uppfyller kraven. Studien syftar även till att bedöma vilka möjliga miljöeffekter implementeringen av en Vinterparklek kan leda till på varje plats, samt bestämma på vilket vis konstgjord snö ska erhållas för att ha minst bidrag till klimatförändring. Resultaten visar att det finns flera tekniska krav som måste uppfyllas på en plats för att kunna genomföra en Vinterparklek. Ingen av de valda platserna uppfyller för närvarande alla tekniska krav för en Vinterparklek, även om det anses möjligt att bägge platserna kommer kunna uppfylla dem i ett senare skede. Resultaten från MKB visade på att införandet av en Vinterparklek vid Tveta Friluftsgård rimligtvis skulle ha mindre negativa miljökonsekvenser jämfört med vid Stadsparken. Genom att beräkna koldioxidavtrycket för de alternativa sätten att erhålla tillverkad snö, drogs slutsatsen att snö producerad direkt på plats, samt använda en sjö som vattenkälla, skulle vara det mest gynnsamma, i form av minst bidrag till klimatförändringar. Den slutliga slutsatsen är att en Vinterparklek är genomförbar i Södertälje kommun, med Tveta Friluftsgård och snötillverkning direkt på plats som till synes bästa tillvägagångssättet. Vilken plats som ska väljas och hur snö ska erhållas kan dock även bestämmas utifrån vad konceptet är menat att bidra med. För att skapa en mer övergripande bild av genomförbarheten och hållbarheten av en Vinterparklek bör framtida studier undersöka sociala och ekonomiska aspekterna som är relaterade till konceptet.