Permafrost Technology Foundation Library
The Cold Climate Housing Research Center is digitizing and cataloging the reports and information the Permafrost Technology Foundation (PTF) collected over 20 years. The PTF was formed to develop solutions to permafrost problems. The design manuals and videos created by PTF explain what permafrost is and where it occurs, the importance and procedure for a thorough permafrost site investigation, methods for permafrost stabilization, and some techniques used for building new structures and stabilizing existing structures on permafrost.
Permafrost is loosely defined as soil and/or rock that remains frozen for more than 2 years. Permafrost is found to some extent beneath 85% of Alaska. In the arctic, north of the Brooks Range, permafrost is at its thickest. Southward from the Brooks Range the thickness of the permafrost lessens and it becomes more and more discontinuous. Near Southcentral Alaska permafrost is only found in isolated masses. In Southeast Alaska permafrost is usually found only in high mountains.
When it comes to construction, the safest bet is to it avoid permafrost altogether and move on to another piece of land. If a structure must be built on permafrost, the first step is a good site investigation by a qualified soils engineer with an above- and below-surface examination. Then a building strategy must be defined: will you thaw the permafrost, remove the thaw-unstable material, or keep the soil frozen? The foundation must be designed around these goals.
PTF performed 10 case studies on houses that had been suffering from the effects of settling.
Grenac Road, Fairbanks AK
A house with a heated crawlspace had significant differential settlement that was remediated by opening up the crawlspace and placing the house on a crib foundation. While requiring periodic re-leveling, the new foundation strategy appeared to have stabilized the permafrost.
Cordwood Drive, Fairbanks AK
A house built in 1970 was originally predicted to settle significantly based on a 1990 geotechnical exploration. However, after several years of monitoring, it was found that the house was relatively stable as the underlying permafrost receded.
Ballaine Road, Fairbanks AK, June 1999
A two-story residence with a crawlspace located on permafrost, including several feet of clear ice, was remediated by ventilating the crawlspace and insulating the utilities. Settling continued through the monitoring period, but was substantially reduced by the remediation strategy.
Constitution Road, Fairbanks AK, September 2000
A heat pump was retrofitted for a house with a daylight basement to cool the ground underlying the building. The strategy was highly successful, but required proper maintenance of the heat pump to avoid further settlement or too much heat removal leading to frost jacking.
Glacier Avenue, Fairbanks AK, June 1998
Settlement problems with this home resulted from loose soils underlying the foundation, not due to permafrost. Injection of grout was considered as a remedial approach, but not performed due to the risk of poor results.
Jones Road, Fairbanks AK, June 1998
A house with a shallow pile foundation with settlement problems was replaced with a Triodetic foundation. Differential settlement continued after installing the new foundation, but was shown to be maintainable by periodic leveling maintenance.
Kivalina Street, Fairbanks AK, June 1998
This house was built on relatively thaw stable permafrost, which was rapidly retreating during the monitoring period. It was concluded that the settlement damage to the house was an initial condition that hadn't progressed any further.
Madcap Lane, Fairbanks AK
A house with a daylight basement on thaw-unstable permafrost had several thermosyphons installed under the entire house footprint. This was successful in slowing the rate of settlement.
Rise Road, Fairbanks AK, June 1998
A small house with a crawlspace had substantial differential settlement that was alleviated by placing the house on adjustable jacks. During the monitoring period, the permafrost thawing appeared to stabilize after separating the house from the ground.
Stanford Drive, Fairbanks AK, June 1998
A single story house had many signs of stress attributed to settlement, however, no evidence of permafrost was found around the house. It appeared that the damage was attributable to inadequate compact of soils during construction.