Browsing by Author "Soininen, Suvi"

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Ratojen routaongelmat Suomessa
(2013) Soininen, Suvi
School of Engineering | Master's thesis
The objective of this study was to look into the problems caused by frost action on Finnish railways. One aim of this study was also to research the most common methods of railway track maintenance used to reduce the problems caused by frost heaving. Factors affecting the selection of maintenance methods and their costs were also examined. The majority of Finland's rail network was built before the 1950'S. Back then the quality requirements for the substructure materials and frost protection were less strict. Frost action occurs in frost susceptible soils when temperatures drop below zero and ice lenses begin to form. Frost heave may also occur in non-frost-susceptible soil. This phenomenon is referred to as in-situ frost heave and it must also be taken into consideration because no frost heave is allowed on main railways. Differential frost heave causes disturbance to the railway traffic in the form of speed restrictions. The funding available for track maintenance is very limited and therefore it is of great importance to identify the frost prone areas and determine the causes causing frost action. In order to make track maintenance cost-effective and sustainable the frost heave diminishing actions must be planned carefully. Frost depth modelling was carried out with the finite element program TEMP/W. A series of calculations were done in order to determine whether the position of the insulation slab has an influence on the depth of frost penetration. The insulation slab was placed either directly beneath the layer of track ballast or on top of the frost protection layer. Varying insulation slab thicknesses and freezing indexes were used in the modelling. The calculation results showed that when the insulation thicknesses of 40 mm and 80 mm were used, there were no substantial differences in the maximum frost penetration depths. When the insulation thickness of 120 mm was used, differences occurred. The deeper the insulation was placed, the deeper the frost line penetrated. One goal of the numerical modelling was also to determine the depth of frost penetration beneath the insulation slab in case if the substructure materials were frost-susceptible. The frost-susceptible soil must be replaced with non-frost-susceptible substructure materials. Based on the numerical results obtained, it can be concluded that a greater amount of the frost susceptible soil must be replaced in Northern Finland than in Southern Finland.
Teiden siirtymärakenteet pehmeiköllä
(2008) Soininen, Suvi
Insinööritieteiden ja arkkitehtuurin tiedekunta | Bachelor's thesis