Suggested best practice for geotechnical characterisation of permafrost in the Nordic countries

Even though permafrost is a specialty within Nordic geotechnical engineering, engineers and researcher will be faced with managing the consequences of projected climatic influences to construction design in permafrost areas. This requires the determination of the frozen soil engineering properties largely influenced by the content of ice in the soil.

This paper presents and discusses different methodologies for laboratory determination of the soil bulk density, ice content, unfrozen water content, strength and deformation properties as well as thermal properties from frozen soil core samples. It is proposed that a best practice for permafrost characterisation employs sample volume determination based on the Archimedes principle and that ice contents are presented as the volume fraction of excess ice to the frozen sample volume.

Furthermore, direct measurements of unfrozen water content and thermal properties should be preferred, while soil residual salinity should always be determined. The procedure for determination of strength and deformation properties should be subject to projected soil temperature at end of construction service lifetime.