Abstract: A simplified method based on the load transfer approach is proposed for the working performance analysis of single energy piles. In the method, the load transfer function is chosen as a hyperbolic curve, and the unloading and reloading characteristics of pile-soil interface during temperature cycling are simulated by Masing's criterion. The accumulation of plastic deformation is approximated by reduction of stiffness during reloading. The location of the null point can be naturally determined by solving the governing equations through the matrix displacement method. The pile displacement, the axial force, the shaft resistance, and the base resistance can also be obtained. The proposed method is validated by comparing the predicted values with the experimental data collected from literatures. Finally, the long-term performance of single energy piles is studied with an example. The computed results indicate that the thermal cycles increase the settlement of free pile top and decrease the stress of fixed pile top. The influence of the thermal cyclic loading is related to the static load level and the degree of the stiffness degradation of the surrounding soil.

Key words: energy pile, load transfer approach, thermal cycles, irreversible settlement, thermal stress