Load transfer of pile foundations in frozen and unfrozen soft clay

Abstract

ABSTRACT This paper investigates load-carrying capacity of two conventional and three helical piles in frozen soft clay and evaluates the changes in pile capacity corresponding to ground thawing. In-situ pile load tests were conducted in frozen and unfrozen Leda clay and used to establish stress-strain correlations to describe the load transfer of the test piles. The stress-strain correlations in frozen ground were favourably comparable within the small strain region. As the load was increased, however, the helical pile reached an adfreeze capacity of 1650 kPa followed by accelerated displacement. The smooth-shafted piles, in contrast, continued to withstand the applied loads because of their larger contact areas. The ultimate pile capacities were significantly decreased following ground thawing recording around 90% lower capacities. The load-carrying behavior of helical piles was dominated by their end bearing; therefore, it was important to drive the helical pile to a sufficient depth to ensure that the helix is located within the permanent frozen profile.