Performance and Design of Laterally Loaded Piles in Frozen Ground

Frozen soils, including both those seasonally frozen and perennially frozen, exists extensively in Alaska and other cold regions. During past earthquakes, widespread damage was observed in deep foundations in the ground, and frozen ground appears to be the direct cause of at least some of that damage. The aim of this paper is to investigate the effects of seasonally frozen soil on deep foundations during lateral loads induced by earthquakes, ice, wind, vehicular impacting, and other loads with a short duration, and to recommend simplified tools for design practices. Two identical reinforced concrete-filled steel pipe piles were tested to large deformations at unfrozen and frozen soil conditions to demonstrate the effects of seasonally frozen soil on the lateral behavior of steel pipe piles. The pile tested at unfrozen condition behaved as a rigid pile, and the other at deep seasonally frozen condition formed a very shallow plastic hinge. Pile performance data in deep seasonally frozen silts were used to evaluate the fixity depth approach parameters, which include depth-to-maximum-moment, depth-to-fixity, and analytical plastic hinge length. In addition, the test data were used to calibrate a finite element (FE) model for assessing the effects of varying seasonally frozen soil depths on the pile lateral behavior and fixity depth approach parameters. These fixity depth approach parameters for various frozen soil depths can be used to account for the effects of seasonally frozen soil on pile lateral behavior in design practices.