4.4 Prerequisites for frost dimensioning
When designing for frost, consideration must be given to the fact that the
surface temperature during the winter is generally lower than the air temperature 2 m above ground, where air temperature measurements are taken. When using the design curve for blasted rock, this is included.
Reference is made to 'Frost action in ground' no. 17 for estimating climatic loads. In respect of frost dimensioning of railways, the winter surface temperature is calculated based on the method stipulated for asphalted roads. The summer surface temperature is calculated based on the air temperature during an ordinary summer.
The insulating effect of snow layers is not taken into account when frost dimensioning.
It must always be assumed that the formation has been drained when frost dimensioning.
In the case of a single-track line, the width of the frost protection layer at the top must be at least 5.0 m. In the case of a double-track line, or a line comprising several tracks, the frost protection layer must be at least 2.5 m on either side of the centre of the track.
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