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Numerical Thermo-mechanical Analysis and Parametric Study of Energy Piles Group

Vahedi, Amir Hassan | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58819 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. The escalating demand for energy, coupled with significant environmental concerns, has underscored the importance of ground heat exchange systems as a sustainable solution for building heating and cooling. Among these technologies, energy piles—representing the most common form of thermally activated foundations—play a pivotal role in facilitating heat transfer between structures and the subsurface. Despite the rapid development of these systems, a comprehensive understanding of their thermomechanical behavior and sensitivity to various design parameters remains a critical area requiring further investigation. In this study, the coupled thermal and mechanical response of energy piles subjected to thermal loading is examined using finite element numerical modeling in ABAQUS software. The numerical model was first validated against reliable data from previous studies. Subsequently, a comprehensive parametric study was conducted to evaluate the influence of key thermomechanical parameters—including the coefficient of thermal expansion, Young's modulus, thermal conductivity, specific heat capacity, and duration of thermal loading—on the response of the pile and surrounding soil. This approach enhances the understanding of thermal and mechanical interactions within energy pile systems, providing insights that can contribute to the optimization of engineering designs. The results indicate that within the investigated temperature range, the thermally induced stresses and strains during heating remain within permissible limits relative to the compressive strength of concrete. However, under cooling conditions, significant tensile stresses develop within the concrete piles, necessitating careful consideration due to the inherently low tensile strength of concrete. The parametric analysis reveals that variations in the elastic modulus and heat capacity of both soil and concrete significantly affect the axial stress distribution along the pile and the vertical displacement at the ground surface. notably, an increase in the coefficient of thermal expansion leads to greater vertical pile displacement and extends the depth at which the axial stress changes sign. Furthermore, the interaction between the duration of thermal loading and thermal conductivity results in pronounced nonlinear effects on axial strain, thereby increasing the sensitivity of the pile's response to temperature fluctuations. These findings highlight the importance of understanding thermal effects on the behavior of concrete piles under varying temperature and loading conditions, offering valuable guidance for optimizing engineering designs and enhancing structural safety
  9. Keywords:
  10. Pile Group ; Geothermal Energy ; Finite Element Method ; Thermomechanical Loading ; Coupled Thermo-Mechanical Behaviour

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