Multiphysical Modelling of Pile Behaviour Under Combined Vertical and Lateral Loads in Thermally Variable Soils

Modelling of the Thermo-Hydro-Mechanical Response of Bridge Pile Foundation–Soil System to Degrading Permafrost

Thermomechanical Framework for Settlement Calculation of Geothermal Energy Piles in Multilayered Soil

In this study, a continuum-based analytical model of the geothermal energy pile subjected to an axial mechanical load and undergoing temperature change is presented, in which soil displacements are assumed considering the kinematic compatibility between the pile and the soil. Stresses caused by the temperature change are explicitly taken into account by relating it to the restrained thermal strain. The principle of minimum potential energy and calculus of variations are used to obtain the differential equations of the pile and soil displacements. The differential equations are solved using an iterative algorithm. Verification and validation studies with equivalent finite-element analysis and experimental/field studies show that the analysis produces accurate pile responses in terms of vertical displacement, strain, and stress and can produce field pile response with reasonable accuracy. The novelty of the developed framework lies in its ability to incorporate the effect of soil temperature change on the thermomechanical pile–soil interaction, a feature missing in all other existing analytical frameworks. The effect of soil temperature change on the mechanical response of the pile is examined and is found to have negligible effects on energy piles. Subsequently, closed-form solutions for vertical displacement, strain, and stress are developed for energy piles under mechanical and thermal loads embedded in different soil profiles that can be directly used by designers. Another novel feature of this framework is that the soil spring parameters representing elastic soil compression and shear resistances are obtained iteratively as part of the solution without requiring ad hoc empirical equations. Fitted equations for these parameters are developed after a thorough parametric study that eliminates the need for iterations in obtaining the pile responses analytically.

A Theoretical Framework for Predicting Soil Setup in Laterally Loaded Piles in Clay

Soil setup is known to enhance the capacity of jacked piles and is well documented for axial resistance, but its influence on lateral behavior and corresponding evaluation methods remain limited. In this study, a new theoretical framework is proposed to estimate the time-dependent lateral response of closed-ended piles in normally consolidated clay by jointly considering installation-induced disturbance and subsequent consolidation. The framework couples cavity expansion theory with an effective stress approach to capture the evolution of pore pressure, effective stress and strength from installation through reconsolidation, and to quantify the attendant changes in pile–soil interaction. Its performance is demonstrated against finite-element simulations and a field experiment, showing close agreement. Results reveal a strong link between lateral capacity gain and the dissipation of excess pore pressure. Parametric studies further show that rigid piles experience significantly greater capacity improvements than flexible piles, as their associated soil flow mechanisms enable the mobilization of a wider zone of strength-enhanced soil. In addition, increasing pile diameter prolongs the dissipation of excess pore pressure and thus the setup process. While the setup effect for laterally loaded piles is generally less substantial than that widely reported for axially loaded piles, especially for flexible piles, the present framework offers a useful means of evaluating its influence in applications where lateral stiffness and deformation are particularly sensitive and govern performance.

Thermo-Hydro-Mechanical Response of a Transmission Tower Pile Foundation in Seasonally Frozen Ground

Freeze–Thaw Infiltration Governed by Soil Freezing Characteristic Curves and Hydraulic Impedance in Unsaturated Sands

Seasonally frozen soils strongly influence infiltration, runoff generation, and infrastructure performance in cold regions. However, infiltration modeling in partially saturated sandy soils remains poorly constrained due to limited experimental characterization of hydraulic parameters under freezing conditions. This study investigates coupled thermo–hydraulic behavior in sandy soils using laboratory column experiments and finite element modeling implemented in COMSOL Multiphysics. Instrumented soil columns were subjected to controlled freeze–thaw cycles to measure transient temperature and liquid water content profiles. A coupled TH model incorporating the van Genuchten–Generalized Clausius–Clapeyron formulation was used to represent phase change and cryosuction. The soil freezing characteristic curve and impedance factor were experimentally determined. Model simulation reproduced measured thermal and hydraulic responses with good agreement. Results show that frozen hydraulic conductivity is highly sensitive to the impedance factor and initial moisture conditions, with an approximately exponential relationship. Freeze–thaw cycling caused hysteresis in the soil–water retention behavior, which is attributed to pore structure modification caused by ice formation and thawing. These results improve parameter estimation for frozen sandy soils and establish a validated framework for simulating coupled heat and moisture transport in cold-region environments.

A thermo-mechanical constitutive model for fine-grained soils under cyclic and monotonic loading

Geothermal systems and geostructures, as sustainable energy sources, undergo daily and seasonal temperature fluctuations that significantly influence their mechanical response. Reliable prediction of thermally induced deformations therefore requires advanced thermo-mechanical constitutive models. Existing approaches often address constant elevated temperatures but fail to capture multiple thermal cycles or the coupled effect of mechanical cycling under heating. This study presents a hypoplastic thermo-mechanical model enhanced with the extended intergranular strain anisotropy concept to reproduce small-strain behaviour. Experimental evidence shows that normally consolidated fine-grained soils, when subjected to repeated thermal cycles, exhibit a transition to an overconsolidated state after the first heating–cooling cycle. To capture this, the model introduces a temperature-dependent preloading surface, enabling the evolution of the three-dimensional overconsolidation ratio under thermal cyclic loading. In addition, the original viscous strain-rate mechanism at ambient conditions is preserved, ensuring a consistent representation of rate effects under coupled thermal and mechanical actions. The proposed model is validated against diverse thermo-mechanical loading paths, including monotonic and cyclic scenarios, across different soil types. The results demonstrate its capability to capture key aspects of the complex response of fine-grained soils under combined thermal and mechanical loading, indicating its potential applicability to energy geotechnical problems.