Prediction of Pile Performance in Permafrost Under Lateral Load

In 1971 lateral pile tests were performed at Inuvik, N.W.T. to determine design values in creep for timber and steel pipe piles. Formulation of a theoretical method for prediction of pile load capacity from basic permafrost creep parameters was a part of this program.In 1972 pressuremeter creep tests were performed at the same site so that test pile performance could be predicted independently and compared with measured results. The pressuremeter tests made and the creep parameter values obtained, the predicted pile performance curves and the comparisons with actual test data are presented in this paper.A Menard pressuremeter was used to determine permafrost creep parameters at an average ground temperature of 29.2 °F (−1.6 °C). Values for the representative creep modulus and exponents for this soil were derived from the test data. These were used for calculating pressure–deflection curves and subgrade reaction moduli for the laterally loaded piles.To demonstrate the applicability of the theory, the subgrade reaction moduli derived from the pressuremeter tests were compared with those deduced directly from the pile load tests. A reasonable agreement was found with the subgrade reaction moduli values obtained for the timber piles. However, the steel pipe piles responded as though the modulus was much higher.The confirmation field tests were made at a site having ice-rich permafrost whose behavior approaches that of pure ice. To apply the basic theory generally, additional field confirmation tests would be needed, for example, in ice-poor permafrost and covering much longer periods of time.