Relatively small, lightweight buildings in permafrost areas can be constructed with adjustable screw jacks to compensate for differential ground thaw.
Early construction in northern communities often followed southern building practices. If the buildings were constructed directly on ice-rich soil, warming of the ground often resulted in collapse. Photo from Norman Wells, Northwest Territories in 1953, courtesy of the National Research Council of Canada, Divi- sion of Building Research.
Thermosyphons act to preserve permafrost underneath this large industrial building in Norman Wells, allowing for the structure to be placed in direct contact with the ground.
Thermosyphons passively preserve, and can even create, permafrost, although it is an expensive undertaking. Thermosyphons use cold winter air and convection of a liquid or liquid and gas, commonly ammonia, to preserve permafrost. Currently they cool a roadbed in Yellowknife, are underneath a large industrial building in Norman Wells, and create permafrost in a tailings impoundment dam at the Ekati Mine north of Yellowknife. The Trans-Alaska Oil Pipeline uses thermosyphons along much of its length. Several large, heavy buildings, such as the oil storage tanks at Norman Wells, are constructed on a ventilated gravel pad. Engineering and design in northern regions have come a long way since the early days of simply transplanting southern techniques to permafrost regions. However, with the threat of a warming climate, it is possible that the stability of frozen ground cannot be assumed into the future. Warming ground temperatures have already been noted in Alaska, Sibe- ria and northern Canada. Although the permafrost regions of Canada are not densely populated, their economic importance has increased significantly in the last few decades, especially as strategic areas for natural resources. New construction and design techniques will have to be adapted to reflect the increased instability of the permafrost regime upon which northern infrastructure depends.
Stephen Robinson is an Assistant Professor of Geology at St. Lawrence University in Canton, New York. He holds a PhD from McGill University, and has conducted permafrost research in the Canadian Arctic since 1990. He can be reached at srobinson@stlawu.edu
On Site review 11
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Spring 2004
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