| Summary: | During the winter ice is causing major problems in several of the Swedish Transport administrations railway tunnels. Freezing water is forming icicles and pillars that can fall down at track, and grow so large that they intrude on the clearance gauge. Lighting equipment and cables can be broken because of the ice load and tracks can become cowered with ice Periodic freezing can cause frost shattering and this process can cause fall-outs of rock and shotcrete. In order to maintain safety and prevent traffic disruption, many tunnels requiring extensive maintenance. In order to reduce maintenance of the tunnels, improved knowledge about frost penetration and the effects of ice pressure on the load-bearing capacity of the tunnel is required. 2002 the University of Gävle and KTH performed a model study to determine the temperature conditions in tunnels. To verify the model study field measurements are carried out in collaboration between the Transport Administration and Luleå University of Technology. This technical report describes the tests conducted so far in the Glödberget tunnel at Nyåker, 80 km south-west of Umeå. Measurements show that the developed models underestimate the frost penetration. Although the tunnel is 1680 meters long, the frost penetrates the entire length of the tunnel even if the temperature outside the tunnel is just a few degrees below zero. A contributing factor to why the field measurements and model do not conform can be that the model study is based on a completely uninsulated tunnel. In the Glödberget tunnel a large part of the walls and roof are covered the frost insulated drains. The function of the frost insulated drains is to prevent the cold tunnel air from reaching a leakage point and causing water to turn into ice. However, the insulation does not only prevent the cold air from reaching the rock, but also prevents the heat from the rock mass from entering the tunnel and warming up the cold tunnel air. Consequently, the frost penetrates further into the tunnel than it would do if ...
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