Heated Infrastructure

Heated infrastructure directly influences the thermal regime of the ground if the structure-ground contact surfaces are insufficiently insulated (Instanes et al., 2005). Active layer thickening and subsidence occurred, for example, beneath the northern tower of the

Kulmhotel Gornergrat (Zermatt) due to heating of the tower basement for over 20 years. Concrete was injected to stop the differential settlement, with apparent success (Hof et al.,

2003). Bedrock instability due to loss of ice (possibly also induced by climate change) has been observed in the vicinity of several cable car stations and mountain huts (Datwyler,

2004), causing damage to the buildings in recent years. Attempts have been made to stabilise the ground and buildings by pumping concrete into fissures and boreholes (e.g. approximately 200 tonnes of concrete were injected into the ridge under the Swiss Gemsstock cable car station in 1993, personal communication F. Nager, see also Fig. 16 ) or by inserting rock anchors (e.g. in 2001-2003 under the Erzherzog Johann hut on the Grossglockner, Austria). Even unheated structures can modify the thermal regime of the ground and induce subsidence, which has recently happened under garages on the Schilthorn (personal communication P. Feuz) and Gemsstock summits (Fig. 16). Tunnels can also have a disturbing effect, as air or water can warm frozen rock zones, as was observed during the drilling of access tunnels in Chli Titlis (Haeberli et al., 1979), Klein Matterhorn (Rieder et al., 1980) or in the Jungfrau east ridge (Wegmann, 1998). The heat transferred into the tunnel of the Klein Matterhorn tunnel by 490,000 visitors every year and generated by about 70,000 elevator movements in transporting people to the mountain top has caused the bedrock temperatures in the tunnel to rise from -8°C in 1999 to -3°C at present, as well as the refreezing of meltwater in the lift shaft, requiring remedial ventilation measures (King and Kalisch 1998, Baumann et al. 2005). Another current problem is thermokarst settlement in ground around water pipes for technical snow systems, leading to the formation of deep holes in ski pistes and damage to the pipes. Although steel trellis structures such as pylons and snow-supporting structures warm up to around 30°C diurnally under the influence of direct solar radiation, temperature measurements on micropiles below steel snow-supporting structures and in the surrounding ground have shown that the brevity of the warming periods prevents heat transfer into the ground (Phillips et al., 2000; Phillips and Schweizer, 2007). The main problem affecting these types of structure are temperature- and water dependent creep movements of the ice rich permafrost soils in which they are anchored (Phillips and Margreth, 2008; Rieder et al., 1980).

Figure 16. Fleece-covered snow ramp on the summit of Gemsstock, Swiss Alps (C. Danioth). To the right of the ramp, the rock wall was also covered and temperatures are being monitored. Concrete was injected into the ridge beneath the summit station in 1993 to increase the bearing capacity of the ground.

Figure 16. Fleece-covered snow ramp on the summit of Gemsstock, Swiss Alps (C. Danioth). To the right of the ramp, the rock wall was also covered and temperatures are being monitored. Concrete was injected into the ridge beneath the summit station in 1993 to increase the bearing capacity of the ground.

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