A design approach for pile foundations in permafrost

Abstract

A design philosophy for piles in ice and ice-rich permafrost is proposed, whereby the pile settlements over the design life of the structure are retained within acceptable limits.The secondary creep law for ice is reviewed and the relationships between secondary creep rate, stress, and temperature are obtained using existing creep test data from many different sources. An analysis is performed which relates the steady pile settlement rate to the pile shaft stress and the constant ground temperature.A review of the pile load test data available in the literature is carried out, and the results are compared with the theoretical predictions provided by the pile settlement analysis. Reasonable agreement is obtained between prediction and observation, and it is thought that the analysis presented here provides a conservative (safe) bound on the observed results.The analysis is extended to account for the compression of the pile shaft, varying ground temperature profiles, stress readjustment along the pile shaft, and the end bearing capacity of the pile.The analysis presented here provides a rational basis for pile design in permafrost and, in addition, explains many of the phenomena likely to be observed in the behavior of piles under sustained loading.