# Thermo-hydro-mechanical response of energy-piled walls under varying wall configurations, pipe layouts, and seepage conditions

## TL;DR

This study explores how energy-piled walls respond to heat, water, and mechanical forces, offering design guidance for different configurations and ground conditions.

## Contribution

The study introduces a detailed 3D finite-element model to analyze the thermo-hydro-mechanical behavior of energy-piled walls under various configurations and seepage conditions.

## Key findings

- Wall type and thermal boundaries influence lateral displacements, remaining below ±2mm under all conditions.
- The 4U-shaped pipe layout is preferred over the spiral layout due to lower thermo-induced stresses.
- Seepage enhances heat exchange but alters bending moment distributions based on permeability thresholds.

## Abstract

Energy-piled walls combine earth-retaining and thermal energy-harvesting functions; however, their thermo-mechanical behaviour remains less understood than that of energy foundation piles. This study investigates the coupled thermo-hydro-mechanical response of energy-piled walls using 3D, time-dependent, coupled finite-element models over a six-month heating period, focusing on the effects of wall type, pipe layout, seepage, and thermo-induced pore water pressure. Key findings indicate that: (i) wall type and thermal boundaries influence lateral displacements, with magnitudes remaining below ±2mm under all conditions examined; (ii) the 4U-shaped pipe layout may be preferred over the spiral layout due to generally lower thermo-induced stresses; (iii) seepage enhances heat exchange capacity but introduces wall-slab-seepage interactions that invert bending moment distributions at excavation depth, with behaviour controlled by permeability thresholds (\documentclass[12pt]{minimal}
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\begin{document}$$k < {9.09}\times ^{-17}{\textrm{m}}^{2}$$\end{document} for pore-pressure-dominated behaviour); (iv) peak tensile stresses can exceed concrete capacity, particularly at slab-pile connections, indicating potential localised cracking. The findings are synthesised into a conceptual framework that accounts for these coupled interactions and provides quantitative design guidance across diverse wall configurations, pipe layouts and ground conditions.