Numerical and field investigation of the Thermo-Hydro-Mechanical response of geothermal energy piles

Abstract

Deep foundations provide structural support to buildings, safeguarding against the risk of potential subsidence or ground movements. The piling industry, currently valued at £600M to £650M annually in the UK, continually evolves to address new engineering challenges amid rapid urbanisation.
Moreover, the imperative to address climate change, driven by human activities and fossil fuels, necessitates a shift towards sustainability.

Energy piles offer eco-friendly heating and cooling solutions, utilising geothermal energy naturally stored in the ground. Despite extensive research and numerous buildings adopting energy pile technology, the industry is still hesitant to fully embrace it due to concerns about thermal-loading cycle effects on the structural stability and potential degradation of energy piles, and lack of clear guidelines for incorporating thermal actions for their design. This thesis work contributes to understanding the thermo-mechanical energy pile response through numerical simulations and field measurements. It analyses temperature and strain data from the Lambert College energy pile test, highlighting the importance of different monitoring techniques. The field data validate the numerical predictions from one-dimensional load-transfer and two-dimensional thermo-hydro-mechanical (THM) finite element models.

The study identifies the best back-calculation approach for non-linear load-transfer numerical analyses, leading to better predictions with respect to the published work. Furthermore, stress paths obtained from two-dimensional THM finite element models and the introduction of the stress ratio, as an index able to quantify local energy pile structural stability, helped in identifying load configurations at higher risk of collapse. Finally, it is shown that the simple load-transfer analysis technique can offer reliable results, but for more elaborate cases involving complex time-dependent temperature changes the full transient THM analysis should be adopted.

Date of Award	26 Jun 2024
Original language	English
Awarding Institution	University of Bath
Supervisor	Loizos Pelecanos (Supervisor), David Coley (Supervisor) & Kenichi Soga (Supervisor)