Pile—soil interactions in frozen soil foundations based on frost heave rate and soil stiffness variations

Abstract

The frost heave rate and stiffness of soil in frozen soil foundations varies remarkably with the freezing depth under the influence of the freezing-end temperature, temperature gradient, and overburden stress. The stress level of frozen soil increases with increasing frost penetration, leading to greater stiffness and a smaller frost heave rate. In this work, the freezing-end temperature and temperature gradient are introduced to the traditional Takashi model via the frost heave layering method and the overburden stress is modified to establish an empirical prediction model of frost heave rate and stiffness. Analytical solutions of load transfer differential equation of single pile considering stiffness increase and frost heave rate decrease along the frost penetration are derived on the basis of the mechanism of pile–soil interactions. The calculation results are in good agreement with measured values, thus confirming the correctness of the analytical solution. Variations in frost heave rate and soil stiffness with increasing depth are then combined to form four models, and changes in axial force and tangential frost heave force as a function of frost penetration are calculated and analyzed on the basis of these models. Results show that calculation of the frost heave rate and stiffness of soil along the frost penetration depth according to normal values will significantly underestimate the axial force of on the pile.