A Quick Approach for Estimating Load Transfer of Conventional and Helical Piles in Ice-Rich Frozen Soils

Abstract

This paper introduces a new approach for predicting load carrying capacity of circular section piles and helical piles in frozen ice-rich soils based on ground's freezing temperature and the temperature-dependent cohesion. Results obtained using this approach were validated against a field measured load carrying capacity for model single-helix helical piles, steel open-ended pipe piles, and cylindrical concrete piles in unfrozen and frozen Leda clay. The piles were first tested before wintertime while the ground was in unfrozen condition. The measured load carrying capacity in the unfrozen condition agreed well with the predicted capacity obtained from a modified previous design model for helical piles and the alpha method for the circular section piles. Modified formulae from these models were developed and used for predicting the load carrying capacity of the test piles in the ground after freezing. The predicted pile capacities agreed well with the measured load carrying capacities in the frozen ground. The introduced design approach was beneficial in providing accurate predictions for different pile types, under different loading conditions, and using readily obtained input parameters (i.e., ground temperature and the temperature-dependent cohesion strength). The presence of a snow layer on the ground surface reduced the frost depth penetration and led to a significant reduction of the load carrying capacity of the test piles particularly the helical piles.