Thermoplastic stabilisation of floating energy pile settlement: A TSL-enhanced constitutive model and finite-element analysis

Floating energy piles subjected to cyclic thermal loading may develop ratcheting settlement due to irreversible thermoplastic deformation of the surrounding soil. Existing models may either neglect this mechanism or overpredict long-term accumulation when no stabilisation process is considered. This study presents a thermo-mechanical bounding surface (TMBS) model enhanced with a thermal stabilisation line (TSL) for analysing floating energy pile settlement. A thermal state variable is introduced to describe the distance between the current soil state and the thermally stabilised state, allowing thermal plastic strain increments to decay during repeated heating–cooling cycles. The model is implemented in ABAQUS through a UMAT subroutine, evaluated against cyclic thermal element-test data and centrifuge observations for a floating energy pile in lightly overconsolidated clay. Extended numerical simulations over 50 thermal cycles are then used to examine the model-projected long-term settlement response and its accumulation rate. Parametric analyses further show that the temperature-dependence parameter r N , TSL intercept N T , thermal amplitude and initial OCR strongly affect the severity of thermal ratcheting settlement. The proposed framework links element-level thermal accommodation with pile-scale serviceability prediction.