FöRFATTARE
Forsström, Anna

DATUM
2002-05-07

INSTITUTION
Väg- och vattenbyggnad / Geoteknik

SAMMANFATTNING
Thermopiles and thermosyphons are sometimes used in permafrost areas in preventing permafrost thawing and, in some cases, to reduce frost heaving. The system is used to maintain permafrost as well as to stabilise weak unfrozen soils. Thermosyphons might also be used in a slightly different way, i.e. to create permafrost in non-permafrost areas, but at locations where relative severe winters occur. Ski resorts in Sweden and the rest of Scandinavia are interested in extending their ski seasons in the autumn and spring and therefore want to have a continuous snow cover as early as possible.

For this reason a thermosyphon was installed at Dundret, Gällivare in November 2000. The aim was to investigate if thermosyphons could be used to make the ground cool enough to create permafrost, or so that initial snowfalls would not melt in early winter. If it is possible to create permafrost in areas without natural permafrost, this could be utilised to cool the ground. A substantial snow cover would then be easier to form earlier in the season. Early snowfall often melts from bottom and up, i.e. due to the non-frozen and warm ground. If the ground is cooled, melting is thus reduced.

The area tested had a width of 3.75 m and a length of 20 m. Loggers measured the ground temperature continuously with 72 thermocouples, where 132 thermocouples were available for manual measurements. The temperature measurements at the artificially cooled area were compared with the temperature measurements at the undisturbed ground.

In this report ground temperature measurements for November 2000 to May 2001 and November 2001 have been analysed. In general, the temperatures are lower within and closer to the installation than when compared to the undisturbed ground.

ISSN 1402-1536 / ISRN LTU-TR--02/07--SE / NR 2002:07