As part of the effort to make the Dutch waterways CO2-neutral, a consortium consisting of, among others, CRUX Engineering BV and Delft University of Technology, initiated a case study in which the thermal and mechanical performance of an energy sheet pile wall is studied. This technology allows for the extraction of energy from the water and soil by means of collectors, i.e. a system of pipes welded to the sheet piles. The fluid flowing through these pipes is directed to a heat pump after which the extracted energy can be used to heat buildings. Moreover, during summer, the system provides the opportunity to be used to cool homes by storing heat in the subsurface. The primary objective of a sheet pile wall is to assure stability of the quay and by giving the sheet pile wall an additional purpose, that of heat sink or source, previously not present thermal loads are applied to the wall. In this thesis the temperature change of the sheet pile wall and soil is investigated after which the deformation of the sheet pile wall is analysed in order to answer the main research question: 'Can the structural safety of a sheet pile quay be guaranteed when the sheet pile is thermally activated?'.

In the town of Zweth, part of the municipality of Rotterdam, an investigation into the performance and consequences of thermally activating a sheet pile wall was conducted in the form of a case study. A sheet pile wall with a width of approximately 7.5 meters and a depth of 15 meters was placed. Two sets of loops were welded on the sheet pile: loops running to the bottom of the wall and loops running to a depth of 3 meters. The influence on the surroundings of these separately investigated loops was monitored by means of thermistor strings. The deformation of the sheet pile was measured with inclinometers. This thesis starts with the analysis of the collected data from the field test. To investigate the long-term behaviour of the sheet pile wall two models are developed in this thesis: a heat conduction model and a geotechnical stability model. The former is a thermal calculation only and aims to model the temperature changes in the subsurface as well as the heat extraction. The latter consists of a time dependent Thermo-Hydro-Mechanical (THM) analysis in PLAXIS and used the sheet pile temperature determined in the heat conduction model as thermal boundary condition on the sheet pile. The resulting temperature change of the sheet pile and subsurface in combination with mechanical loads results in a deformation of the sheet pile. Using the data acquired in the field test, these two models are validated. With the help of the validated geotechnical stability model, the thermal component in the total distortion of the sheet pile is investigated. Finally, a calculation with with a time span of 4 years is performed to see the long-term reaction of the sheet pile wall. Based on this research the main question is answered.

In the Netherlands, soil temperatures below 6 meters of depth stays approximately 12 degrees Celsius all year. Above that, the soil temperature changes with the seasons, yet with a delay. The test ran in the autumn and winter and due to the time of the year, the soil at a few meters depth still had the summer heat stored while the soil close to the surface already started to cool down. The interpretation of the collected data started with recognizing from the thermistor string data that the soil in the quay adjacent to the canal is heavily influenced by the water temperature. Deeper down, the heat extraction is the only external influence. Investigations into heat extraction based on the numbers of loops activated showed that there was no linear relation between the concentration of activated loops and the soil temperature decrease. When twice as many loops were activated on the same sheet pile wall area, the soil temperature decrease was only slightly higher. The maximum deformation of the sheet pile wall oscillated throughout the testing period. No direct correlation between thermal activation and deformation was identified.

The validation of the heat conduction model showed that the the soil temperatures in the model were generally too low in the subsurface below 6 meters in the comparison between the in-situ measured temperatures and the numerically determined soil temperatures. The numerically approached temperatures in the quay adjacent to the canal were strongly influenced by the canal water temperature. So much that the heat extraction was barely visible in the data. This emphasizes the importance of good water temperature data. Moreover, part of the energy extracted is a result of the turbulent flow of the canal water parallel to the sheet pile wall. This is not simulated in the model yet important to add. Despite this, the numerically determined extracted heat and the measured heat showed a reasonably good fit.

The comparison of in-situ measured deformation of the sheet pile wall and the numerically approached deformation was in the same order of magnitude as the measured data. The influence of the thermal component on the distortion of the sheet pile was found to be small. During the calculation, the distortion slightly oscillated in the range of tens of millimetres which falls within the numerical accuracy of the model. The measured oscillation was assumed to be caused by changing water levels and soil saturation as well as measurement errors. To investigate the long-term reaction of a thermally activated sheet pile wall, three THM computations with a time span of 4 years were conducted: one without thermal activation, one with natural soil temperature regeneration during summer and one with forced regeneration by the energy sheet pile wall. All had a sinus-like course with an accumulating deformation over time which was intensified by the amount of influence of the energy sheet pile. The computation with the forced regeneration -- i.e. the most influence -- by the energy sheet pile wall ended with the largest amount of deformation which was 5 millimetres larger than the computation without thermal activation. Extrapolating the results, the maximum deformation was determined to be approximately 6 millimetres after 6 years.

The thermal load on the sheet pile wall is not a design parameter and is generally not investigated in detail. Therefore, it is strongly advised to conduct additional research. However, based on these findings, it is concluded that the deformation resulting from the thermal activation of a sheet pile wall is not excessively large. This means the primary objective of keeping the quay stable won't be compromised. This leads to the conclusion that the technology is safe to be applied on a large scale to decrease the carbon footprint and contribute to a more sustainable society without interfering with the quay's primary function.

Geothermal energy is a way of reducing the cost of energy. Deep geothermal energy systems extract heat from very deep soil layers where the temperatures are very high. Shallow geothermal energy systems are about 150 metres deep and they are used to store heat in the soil, to extract it later and use it for space heating. These shallow geothermal systems are generally embedded in a borehole, but they can also be cast into structures, which are called thermo-active foundations. An example of such a foundation is the energy pile, a foundation pile with a heat exchanger embedded in it, connected to a heat pump. There is no need to drill an extra hole in the ground, but the downside is that it is not well known how the bearing capacity of the pile is affected by the heating/cooling cycles. An energy pile experiment is planned to investigate the thermo-mechanical behaviours of the pile and the goal of this thesis is a numerical investigation of the pile. It serves as an estimate of the pile and soil behaviour prior to installation and the results will be used to confidently design the experiment. The model was built with DIANA FEA software, that is capable of coupling thermo-mechanical behaviour. Firstly an experiment in London clay was recreated in order to verify and validate the model and modelling approach. The experiment in Delft was modelled using site investigation that was done at the location where it will be built. Along with old Cone Penetration Test (CPT) data the subsurface was mapped and soil parameters used in the material model were chosen. The thermal cycle that was imposed on the pile was chosen on the basis of preliminary modelling done at different temperature increments. The temperatures were chosen such that the pile was affected to a significant degree of its capacity. It was cooled for three weeks to 0 °C and then heated to 24 °C for three weeks, this was repeated for 6 years. The research focussed on finding which thermo-mechanical effects can be expected and what the scale of those effects could be. The effect directly linked to an increase in temperature is thermal strain. Materials tend to expand and contract with the temperature at different rates and so do the pile and the soil. The gradient of the heat flow is also an important factor as the pile is subjected to the temperature before the soil is. The pile will expand first and this will be resisted by the soil, the strain that is resisted by the soil is called the restrained strain and that is responsible for the change in stress in the pile. A pile that is heated will have more stress than with just a mechanical load and a pile that is cooled will see a reduction in stress. The pile will expand vertically around a null-point somewhere along the pile, this is the point that does not move. In principle, an unrestrained pile will have a null-point in the centre of the pile, but because some soil layers resist the pile movement more than others the null-point is closer to the stronger layers. In the Delft experiment model the null-point was halfway down the pile at first, but as the amount of cycles progressed it moved down. This is due to a decrease in resistance from the weaker layers and an increase in resistance in the strong sand layer on which the pile is based. The amount of stress that is generated is also less in these later cycles as the resistance of the soil became less. With that reduced resistance an increase in settlement is also seen. This can lead to differential settlements of structures that are built on such a pile, possibly damaging them. The results of the modelling are used to give an advice on the experiment details, such as geometry, thermal cycle and pile layout. An advice to the layout of the sensors is included as well as a prediction of the results.