First Canadian Geotechnical Colloquium: Foundation design approaches in permafrost areas

Abstract

The design of foundations in permafrost areas for large structures involves a knowledge of the thermal and mechanical properties of frozen soil. Recent creep data for frozen soils and ice are reviewed and some secondary (steady) creep relationships are established. A design approach for pile foundations in ice-rich permafrost is proposed and compared with available field case histories. The theory is found to provide reasonable predictions of pile settlements under load. It is suggested that the limitation of long-term pile settlements will control the design loadings.The thermal aspects of ventilated pad foundations are discussed and design curves are given for required pad and insulation thickness and ventilation capacity. Case histories indicate that in order to obtain the necessary ventilation capacity, forced air ventilation using electric fans is required for most practical situations.A settlement analysis for spread footings on permafrost is established and influence factors for settlement rate are given. Again it is apparent that allowable footing loads will be controlled by limiting long-term settlements, rather than by consideration of soil shear strength alone. Field data on the creep response of a tunnel in Fairbanks provide good correlation with theoretical predictions.