The rehabilitation of a passive-ventilated slab on grade foundation using horizontal thermosyphons

• Published in: Canadian Geotechnical Journal
• Main Authors: McKenna, J K, Biggar, K W
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1998
• Subjects: Ellesmere Island; permafrost
• Online Access: http://dx.doi.org/10.1139/t98-020; http://www.nrcresearchpress.com/doi/pdf/10.1139/t98-020

Due to the plugging of the vents beneath a vented-slab concrete foundation of the Supply Building at Canadian Forces Station Alert on the northern tip of Ellesmere Island, excessive thermal degradation of the underlying permafrost caused unacceptable settlement of the slab. It was determined that maintenance of the existing system would be an ongoing problem and replacement of the structure would cost $3 million and 3 years to construct. To re-establish the thermal regime under the Supply Building, it was decided to use a newly developed horizontal thermosyphon system installed in the existing vents to rehabilitate the foundation. The thermosyphon installation presented some unique problems owing to the restricted access around the building and the requirement to drill horizontally beneath the building, which necessitated the fabrication of a special drill rig. In addition, the use of horizontally placed thermosyphons is a relatively new application of the existing technology. The paper briefly describes the initial problem, the development of the solution, and describes in detail the actual installation and performance of the horizontal thermosyphon system with 3 years of soil temperature data.Key words: permafrost, thermosyphon, foundation, settlement, ventilated slab, CFS Alert.