Ground thermal modeling and analysis of energy pile foundations

Geothermal resources represent a great potential of directly usable and renewable energy for heating and cooling buildings. Energy piles are deep foundations that combine the structural function as a foundation with a heat exchanger serving the thermal needs of the buildings. These systems represent one of the most suitable systems for heating maximizing economic and environmental benefits. The purpose of this thesis is to evaluate ground thermal response to energy pile foundations using numerical models and methods because they are nowadays a powerful tool for engineering used in many areas of geotechnical design. Because of this, two different study cases were evaluated carrying out both 20 and 30 numerical models. The first case was a preliminary study that evaluates ground thermal response to energy piles foundations in a long term transient analysis for a new building in Kupittaa, Turku. The main objectives of this case were to study ground seasonal heat storage capacity keeping the ground thermal balance during seasonal operations and also the study of a vertical insulation barrier surrounding the pile foundation. The results showed that it was needed to balance the heat extraction from the ground in long term analysis. The effect of the insulation barrier was negligible at ten meters from it but presents good thermal results in points located close to the vertical barrier. The second case evaluated the melting process of the frozen soil below Myllypuro ice rink running several numerical models and studying the thawing settlement produced. The numerical models carried out showed that the time needed to melt the frozen ground was around 800 days. Otherwise, the estimated thaw settlement was around 1.8m until 6.6m of frost penetration