The transition to renewable energy in the heating sector faces significant challenges, particularly the mismatch between the availability of renewable thermal energy sources and fluctuating demand. High Temperature Aquifer Thermal Energy Storage (HT-ATES) systems offer a promising solution to mitigate this mismatch and further decarbonize heating systems by bridging the gap between supply and demand.

This thesis explores the integration of HT-ATES into the heating system at TU Delft, which is transitioning from gas-fired boilers and a combined heat and power plant to a geothermal well-based thermal energy system. During periods of low demand in summer, excess geothermal energy will be stored in the HT-ATES system, to be utilized during high-demand periods in winter when the geothermal well's capacity is exceeded. The objective is to meet 85% of the annual heating demand through sustainable thermal energy sources.

In this study, two design options for integrating the HT-ATES into the heating system are analyzed. Besides the geothermal well and the HT-ATES, the heating system also comprises a heat pump to reach the required supply temperatures. One option is to locate the HT-ATES behind the evaporator of the heat pump and therefore use the previously cooled down temperature to extract thermal energy from the HT-ATES. In the second option, the HT-ATES is located directly behind the heat sink in the system, using the return temperature of the consumers to discharge the HT-ATES.

An energy system model is set up using TESPy and coupled to a numerical model to simulate temperature changes in the HT-ATES. With the results of the model, the influence of the integration concept on the system performance is explained. Furthermore, the effect of varying input parameters such as supply and return temperatures as well as overall demands in the system are examined.

The results indicate that, when comparing the two design options with HT-ATES, locating the HT-ATES behind the evaporator yields the better results across all evaluated performance indicators – mainly a reduction of GHG emissions, an improved system SCOP and a better thermal recovery efficiency of the HT-ATES. However, compared to a base design without HT-ATES, the integration of a HT-ATES leads to additional financial costs and a substantial intervention into the subsurface. Due to its lowest electricity consumption, the base design also shows the best system SCOP.

The Uppermost Ablasserdam Member and Delft Sandstone Member are of high interest for geothermal energy extraction. The stratigraphy, sedimentology, and depositional environment of these members have been studied by different researchers over time. However, due to the lack of physical and extensive logging data within the West Netherlands Basin, there is still uncertainty about their depositional environment and how these sandstone bodies are vertically and laterally connected. Without this data, determining the depositional environment is challenging, and so is developing an optimized reservoir model.

This study performs a sedimentological analysis on the core, sidewall cores, and plugs, together with an investigation of the wireline logs of the DEL-GT wells. The main goal behind this is to determine the different lithofacies types and facies associations and interpret this while considering the limitations of the available data.

The Uppermost Ablasserdam Member and Delft Sandstone Member show characteristics of a fluvio-deltaic system and is located in an upper to lower delta plain environment. With observed facies associations of multi-stacked fluvial to distributary channels, single fluvial channels, crevasse splays, levees, overbank fines, and paleosols. The wireline logs help determine the vertical distribution of the facies, which showed a trend and lateral heterogeneous distribution between the wells. Thus, I could not correlate the wells to each other due to the lack of clear markers and indications that certain sandbodies are connected. Hence, more research on this is needed.

The wireline logs did show a trend from more sand-prone deposits to more silt-prone deposits, which can be related to the the different allogenic and autogenic controls. The controls likely influencing the depositional patterns are the tectonic activity and eustatic sea level change. In combination with climate change affecting the sediment supply and discharge rate, which influences the autocyclic controls of the channels.

This study is based on physical data from the first 80m interval of the one dimension DEL-GT-01 and side wall cores from DEL-GT-02-S2 wells. This brings an uncertainty in determining the lithofacies types and facies associations. Broader research must be done not only on the lithofacies types and facies associations but also on the lateral and vertical distribution. This will help determine the determine the limits of the reservoir.

Moreover, this study brings attention to the importance of extensive core and wireline log data collection.This data will reduce uncertainty for the reservoir model and increase the efficiency of the project and other future projects. It is also highly advised that all the findings and data should be open and free to use for future projects to reduce the uncertainties within the reservoir model.

Discontinuities have an important influence on the bulk behaviour of geomaterials. Discontinuities can be physical openings like fractures and joints, interfaces between different material types, or zones with different material behaviour like mortar or reinforcement material. Bulk material behaviour is often determined by the behaviour of the discontinuities by providing preferential pathways for flow or by acting as failure planes.
FEM simulations with continuum elements are typically not suitable for modelling discontinuities with no width, due to the inability to model discontinuous fields. One solution is to represent discontinuities using zero-thickness interface elements. Inserting zero-thickness interface elements allows for discretely modelling discontinuous behaviour between neighbouring continuum elements. The continuum elements are then used to represent the bulk behaviour and the zero-thickness interface elements discretely model the discontinuity.
A new constitutive law for zero-thickness interface elements that expands the cohesive zone model with friction is formulated in this thesis. The tangential stress response of the interface elements consists of a cohesive and frictional contribution. The cohesive component of the constitutive law is based on the Crisfield’s cohesive elasto-damage model, which is characterised by a linear elastic response to increased relative displacement, followed by degradation of the cohesive strength and stiffness. The elasto-plastic frictional component is based on the Dahl friction model and implemented in parallel to the cohesive component.
The implemented new constitutive law is verified in a large variety of loading conditions, including tangential loading, tangential loading with a reversion of loading direction and combinations of mixed-mode loading. The constitutive laws are validated based on shear box experiments performed on London clay where interface elements are used to model a predefined shearing plane.
The cohesive and frictional constitutive law can represent confinement-dependent tangential stress and residual stress at large relative displacements. These features, observed in the shear box experiments, could not be reproduced by the purely cohesive constitutive law. This new constitutive law can be used to better model discontinuities in geomaterials represented by zero-thickness interface elements.

One-third of the Dutch dike system consists of peat dikes. Drought causes these dikes to crack and fail more easily. Visual dike inspections are therefore inefficient, especially considering the increasing climate changes of the future. Research has shown that a fiber optic sensor cable (FOS), used in distributed temperature sensing (DTS), can help measure soil thermal responses, but the question remains whether it is also suitable as a replacement for visual inspections of dikes. This study helps to answer this question by coupling a finite element method (FEM) model with measured DTS information collected at Flood Proof Holland (Delft). In addition, (thermal) images are used to calibrate the FEM model. The measurement period was 20 summer days. The measured data consisted of webcam images, thermal images, and temperature time series of a FOS cable. The meteorological data was obtained via a weather station located in Rotterdam. The FEM model, calibrated and validated with the measured data, helped to find the thermal response of the system in situations of which no data was available, for example having various crack dimensions, cable positions or climatic conditions. The more distinguished the material properties of air and soil are (days with high water content and/or high radiation), the better the crack detection via DTS. After correction for the overestimation influence of radiation on the black FOS cable on sunny afternoons, the thermal response of the crack is corresponding to the air temperature more compared to the thermal response of grass. Crack detection via DTS turned out to be possible by x,T- and t,T-plots (diurnal temperature variation) and a regression plot with the daily peak-to-peak amplitude of the air temperature on the one hand and the daily peak-to-peak amplitude of the cable on the other. The advantage of the regression plot is that only one DTS thermal time series is needed to determine if the segment is most likely cracked or not. Furthermore, the peak-to-peak axes allow for diurnal climatic condition indications, and with it the heat storage and release of the system: rainy, cloudy days are in lower axis regions whereas sunny, clear days are in higher axis regions. However, due to a small measurement period, this method is only fully proven for sunny afternoons. Future studies have to map the thermal processes for other situations too.

Projections show that urban areas are growing at an increasing rate and produce 60% of the global greenhouse gas emissions (United Nations, n.d.). In Europe, the thermal energy sector consumes about half of the energy resources, of which 85% is produced by fossil fuel-based energy systems (Drijver, Bakema, & Oerlemans, 2019). As a result of this, district heating companies have set climate targets to
lower the harmful emissions produced by the thermal energy sector. This can only be done by replacing fossil fuel-based energy systems by sustainable energy systems. One of the promising sustainable energy systems is the high
temperature aquifer thermal energy storage (HT-ATES) system. HT-ATES
is a buffer system used to store waste heat from industrial processes in a suitable aquifer and transfers this heat to buildings to heat them up in the winter and cool them down in the summer. However, this system is very complex in use and carries many risks. Due to the HT-ATES being a buffer system, complex in use and carrying many risks there are not many running projects incorporating this system. This makes the revenue model and possible exploitation for commercial use very unclear. Therefor, the goal of this thesis is to develop a business case for the commercial use of HT-ATES systems and to assess the business case sensitivity to the thermal energy demand. The research goal will be achieved
by performing a literature study. Assessing the business case viability against other geothermal energy systems will not be in the scope of this thesis. This thesis is merely meant to gain insight on the business case of HT-ATES systems.

The findings of the research show that a project is solely profitable when the benefit outweighs the cost. The total business expenditure of a 30-year lifecycle HT-ATES project with 3,000 households will be fixed upfront expense of EUR 1,236,991 and an additional yearly expense of EUR 695,795. The benefit of the project is strongly dependent on the thermal energy demand. The revenue model of this project consists of a heating price model and government provided subsidy. This business model assumes a heat price of EUR 3.89 per kWh and a subsidy of EUR 2.73 per kWh thermal energy produced. Assuming the annual thermal energy demand is 12.66 kWh per household, the 30-year HTATES project with a district heating network of 3,000 households will have a payback time of 8.4 years. This means that the project will be profitable after 8.4 years. A sensitivity analysis on the thermal energy demand proved that a HT-ATES will be more profitable if the thermal energy demand is higher. This sensitivity analysis also shows that the project will need to have a minimum of 1,300 households in the network in order to be financially feasible, as the payback time of less households will not be within the project lifecycle. A district heating network with a 30-year lifecycle HT-ATES system will have a payback time of 22 year. When this same network where to incorporate 4,000 households the payback
time will be reduced by a factor of 4.

There are multiple numerical methods for analysing the stability of slopes. Commonly used methods for assessing the slope stability are the slip surface method, strength reduction methods or methods based on load increments. What those methods have in common is that the stability of a slope is assessed by a factor of safety or critical stability number. These dimensionless factors give an indication of the global stability of a slope. A critical stability number is computed through load increments while a factor of safety is based on the strength parameters of the soil. A relatively new XFEM-based method for analysing slope stability is being implemented in the finite element software of Diana FEA. Unique with respect to the other methods is that this method detects onset of localisation and captures the propagation of the slip surface. Therefore, this method is referred to as the propagation method in this work. The propagation method consist of three main procedure steps. First, onset of localisation is detected during incremental loading of the model and the direction of the localisation plain is obtained. In step two, enrichment elements are implemented at the location of localisation, which are able to reproduce a jump in the displacement field. This is followed by a search algorithm for detection of localisation in adjacent elements. From here on, the implementation of the enrichment elements continues till a fully developed slip surface is present, resulting in global failure of the slope. Those procedure steps need to be tested and verified. The objective of this thesis is to verify onset of localisation on element level and to provide a method for verification of the point of global failure in analyses with the propagation method. Onset of localisation is verified with analytical expressions and with numerical results. A critical stability number is used to assess the slope stability in analyses with the propagation method. A relation between the critical stability number and the factor of safety is needed, to be able to compute a factor of safety with the propagation method which is similar to a factor of safety of the slip surface method and a strength reduction method. This relation is obtained through the definitions of those factors. This creates possibilities to asses the stability of a slope with the propagation method by a factor of safety and this factor of safety can be verified with the results of a strength reduction method and a slip surface method. In addition, benchmarks are generated with the aforementioned slope stability analysis methods, which can be used for verification of the factor of safety of the propagation method. The benchmarks are the result of parameter and convergence studies. In the parameter studies, the effect of the Poisson ratio and the dilatancy angle on the factor of safety is studied. This is done by computing the maximum vertical displacements during stability analyses with various values of the Poisson ratio and the dilatancy angle. Those displacements are plotted versus the corresponding factor of safety. The resulting plots provide characteristic information which can be used for verification of the propagation method. The convergence studies are performed in order to obtain reliable factors of safety that can serve as a benchmark. The factors of safety are computed for various mesh sizes and different convergence criteria. From the results, a reliable factor of safety is obtained that can be used as a benchmark for the corresponding finite element model. In the end, a development version of the propagation method is tested and the results are verified with a benchmark which is generated with a finite element model containing interface elements.

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.

Tailings are the rock flour which result from the process of mineral extraction at a mine. This waste material is stored in tailings storage facilities, also known as tailings impoundments. These impound­ments gradually grow in size during operation as more tailings are produced and stored over time. These structures are however also prone to failure. Well known failures in the past years are that of the Feijão and Fundão dams in the Minais Gerais state in Brazil. Static liquefaction of the dams has caused mud­streams in which many people were killed and the environment became heavily polluted. This study researched the probability of rainfall­-induced static liquefaction, as meteorological causes have often been named the trigger of failure. The study was limited to upstream raised decommissioned dams in the Minas Gerais state in Brazil. An analysis methodology was established in which the needed rainfall intensity to failure was calculated for different durations of rainfall. In a geohydrological analysis, the Richards equation for unsaturated flow was solved, to model rainfall infiltration. A quasi­-2D procedure was implemented to allow for a computationally efficient solution. Following the results of the geohydrological analysis, a limit equi­librium method was employed to calculate the factor of safety against liquefaction of the dam. In this case, the undrained strength analysis was applied together with an effective stress analysis to model both liquefiable tailings and non­liquefiable tailings in the tailings storage facility. If the factor of safety was equal to a predefined factor of safety associated with failure, the failure intensity was found. The failure intensity was converted to a return period of failure by the application of the Gumbel distributions that are part of the intensity­-duration­-frequency curve of rainfall. These IDF­-curves describe for all possible combinations of intensity and duration the probability of occurrence. Integration of the IDF­-curve for the failure intensities yields the total return period of failure as a single perfor­mance indicator. The analysis was restricted to a period of 5 days of continuous rainfall (storm events) as evaporation effects were not considered and no longer rainfall events were observed in the precipi­tation data used. A series of sensitivity studies was performed to observe how rainfall influences the stability of a tailings dam. It was found that failure is attributed to a loss of suction in the unsaturated zone upon rainfall in­ filtration as well as a loss of strength due to mounding of the water table. Because of the low strengths that liquefiable tailings have, there was the tendency to develop deep slip surfaces below the phreatic surface, causing only marginally stable dams to be prone to failure because of rainfall infiltration. The factor of safety upon rainfall is reduced in the order of 2 to 5 % depending on the parameters used. The strength parameters were of the largest influence. Increasing the friction angle of the non­-liquefiable tailings by 10 % increases the return period of failure by approximately 400 years. The strength ratios used to model the liquefiable tailings are of even larger influence. Adjusting that by only 2 % leads to a jump in the return period of failure of around 1000 years. The chosen boundary conditions for the phreatic surface in the impoundment were also of great influence. A difference of 0.3 meters for the water table for a dam of 20 meters high brings the dam to marginal stability. Given the little sensitivity to storm events, it is recommended to shift focus towards the behaviour of the phreatic surface over longer simulation periods to model the effect of e.g. extremely wet seasons. In addition, construction defects should be considered in which perched water tables could arise, severely decreasing the stability of a tailings dam.

During intense periods of drought, the development of cracks is observed in peat and clay dikes. Asset managers of the dikes increase the inspection frequency in times of drought to be able to monitor these cracks. Significant development of the cracks contributes to the development of different failure mechanisms. In this study, the occurrence of the cracks is predicted at a large spatial scale. An inspection database in which the observations from the last three years are stored is used as the basis. The database contains hundreds of observed cracks including the location and time in which they were observed. The database was extended with attributes such as the precipitation deficit, the peat width at the surface, the orientation of the dike body, the subsidence of the dike body and the soil stiffness. Decision tree algorithms were then used to classify which circumstances will lead to cracks and which circumstances will not. From the resulting decision trees it was deduced that high precipitation deficits, low soil stiffness and the peat width can be used as the main predictors for the occurrence of cracks. Both subsidence of the foundation and the dike body being orientated to the sunny side are also contributors, although less prominent. Time-independent cracking criteria were then used to classify which regions are prone to cracking. Dikes which are rich in peat with a low stiffness were thus highlighted. The Mathews correlation coefficient was used as performance criteria resulting in a 0.3 value for the obtained tree. Application of a random forest increased the coefficient to 0.8. An important conclusion is that proper monitoring of the peat width, soil stiffness and precipitation deficit may result in better asset management. On behalf of more classification validity, it is advised to register negatives during inspections as well. Besides, making a clear distinction between drought-induced cracks and cracks due to macro-instability will reduce the likeliness of the model predicting cracks not related to drought.

The material point method (MPM) is gaining increasing amounts of attention due to its capacity to solve geotechnical problems involving large-deformations. While some problems require dynamic analysis, simulating the (infinite) continuous domain using typical Dirichlet (fixed) boundary conditions induce spurious reflections causing (1) unrealistic stress increments at the domain oundary and (2) the appearance of multiple unnatural stress waves in the domain. Aiming to eliminate this numerical artifact in MPM, two solutions for absorbing boundary conditions found in FEM are implemented and investigated; these are (1) a viscous boundary condition and (2) a viscoelastic boundary condition. The use of such dynamic boundary conditions in MPM is scarce and no validation of them has yet been presented in the literature. In this work, these absorbing conditions are implemented alongside other recent developments, which improves the numerical stability (Double-Mapping, Generalized Material Point Method, Composite Material Point Method), using two approaches: (1) directly imposing at the external active boundary nodes and (2) imposing via shape function interpolation. The proposed solutions are then validated with a one-dimensional benchmark: a soil column under dynamic load in small-deformation and large-deformation, and a 2D symmetric plane strain model under one loading pulse. The benchmark results demonstrate that the numerical reflections that lead to inaccuracies of stress and velocity can be removed using GIMP interpolation and, together with the other numerical technics, render high-quality and realistic results. A study of shallow foundation failure under repeated loading is also presented, showing the potential of applications of the proposed solution for modelling extreme geotechnical events.

Aquifer Thermal Energy Storage (ATES) is a geothermal technique that is an important component in the transition towards renewable energy in the heating and cooling industry, which accounts for half of the world's energy consumption. However, the technology has not yet been implemented in many countries. The main reason is that extensive preparation and site-specific analysis are required for the implementation of ATES systems and many stakeholders need to be involved. These stakeholders are typically unfamiliar with the technology and unaware of the potential applicability. To stimulate stakeholders and the decision-making process within the ATES sector, several studies emphasise the necessity of examining the potential of ATES technology on a local level. Such potential studies support ATES decision-makers as they evaluate the technology, potential scale and its commercial viability.

The objective of this research is therefore to develop a methodology to determine the technical and commercial potential of ATES while incorporating local characteristics. Until now, ATES feasibility studies have mainly been focused on large-scale ATES suitability. For generating more representative results, however, this new methodology also incorporates local geohydrological conditions and the interests of and restrictions imposed by its local ATES stakeholders. The methodology can be applied globally to every region that has available aquifers and moderate climate conditions. The developed methodology in this study is applied to the region of New York State (NYS). High expected energy savings and promising geothermal trends are among the main reasons for this geographic selection. Moreover, no commercial ATES project is yet in operation in the US, a country of which the potential energy savings are expected to be highest in the world. A successful introduction of the technology in NYS could therefore function as a valuable use-case for many other states in the US and also for other countries.

Firstly, the stakeholders in NYS are identified and analysed in this study. They are assessed based on their level of influence, attitude and their ability to solve current barriers that are preventing ATES from being adopted. This analysis indicated that geothermal architects are the most influential stakeholders and are therefore essential to engage for the successful implementation of ATES in NYS.

Secondly, the technical and commercial ATES potential is examined by analysing local geohydrological conditions, building characteristics and the identified requirements from geothermal architects. It is concluded that over 99\% of all buildings in Nassau County (around 400,000) could technically receive the required amount of heat and cold if an ATES system was installed for those buildings. Moreover, it is found that for buildings with ATES systems, heating is twice as efficient as conventional methods in Nassau County and cooling is even 10-30 times more efficient, depending on ATES design parameters. Furthermore, it is concluded that ATES is already a commercially attractive solution for 385 separate buildings in Nassau County, accounting for an estimated 10\% of the total heating and cooling demand of buildings in the county. This number is expected to increase significantly when multiple buildings are connected to a single ATES system.

This research shows that ATES is a technically and commercially viable geothermal solution for buildings in NYS. Therefore, it is critical that ATES is included in the existing evaluation tools developed and currently used by the city and state authorities of New York. The methodology developed in this study is characterised by the inclusion of local characteristics such as the interests and requirements of a region's key stakeholders and local geohydrological conditions, which are found to be essential to generate realistic and accurate insights into the technical and commercial potential of ATES. The model that has been developed is scalable and can be applied to other regions and the accuracy of the model can be increased further by also incorporating groundwater models in the analysis. All in all, the methodology developed in this study offers valuable support for local decision-makers and is an effective resource to increase the adoption of ATES technology worldwide.

This research has demonstrated the applicability of a DTS system to estimate the volumetric water content in saturated mud material. 2 samples of synthetically generated mud and 1 sample of natural mud from the port of Rotterdam were investigated, first by conventional methods and subsequently also with DTS. The system set-up and heating strategy were optimized by testing with different media (air, water) and with different FO coil diameters. A step-by-step approach was then designed to translate the thermal response recorded in the muds into volumetric water contents. Early- and late- time cutoffs were applied to the slope selection procedure (∆T vs ln(t)), and a mud dependent correction factor was applied to obtain the effective heat flux. The average VWC’s (ϴ) subsequently derived from the DTS data were in good agreement with those obtained by conventional methods (core sampling); the standard deviation in the VWC’s (ϴ) of all three tested muds was between 0.030 and 0.040 m³/m³. For saturated conditions, Sayde et al. (2010) and Striegl and Loheide (2012) published larger standard deviations of 0.046 m³/m³ and >0.050 m³/m³ respectively. The approach detailed in this investigation has enabled DTS to perform as a guideline on the continuous volumetric water content profile in saturated muds.

Internal erosion is a frequent cause of dike failure, also known as piping or backward erosion. Uplift is considered a submechanism of internal erosion, together with heave and piping, where all three submechanisms must occur for the dike to reach a failure condition. The principle of the uplift phenomenon is straightforward: it occurs when high pore water pressures in the aquifer lift the cover layer, which is located at ground surface. If the pressure is great enough, the cover layer begins to float ('opdrijven'), and may also bulge ('opbollen') or crack ('opbarsten'). Currently, the assessment for uplift is based on a vertical equilibrium, which relates to a floating condition of the cover layer. The forming of an exit point for concentrated seepage is presumed to happen simultaneously with the increase in uplift pressure and is therefore not explicitly considered in the current assessment. This thesis aimed to investigate in what way the uplift assessment may be improved, both to describe the complex behavior better and to decrease the need for costly countermeasures. The evaluation of uplift was conducted in two parts: by making explicit what the causes of uncertainty are in the current assessment, as well as by proposing a new model to describe the complete uplift behavior better. It is recommended to evaluate the ‘floating’ and ‘bulging-cracking’ phases directly. In the ‘bulging-cracking’ phase, the forming of an exit point can either occur by a tension or shear failure.

Geothermal energy is generally seen as a sustainable source of energy and therefore could be part of the solution for the energy transition. However, there is still a lack of clarity about the conditions under which a geothermal system can be used sustainably. This study investigates the sustainable use of a geothermal system. The geothermal production process in a homogeneous geothermal reservoir with one doublet was simulated using SEAWAT. This model provides the possibility to conduct a sensitivity analysis to examine which parameters play an important role in the geothermal production process. The aim of this analysis was to asses the effect on the well temperature and the thermal recharge, i.e. heat flow from the confining layers towards the reservoir. The tested parameters include four geological uncertainties and two production parameters. From the tested geological uncertainties the thickness of the reservoir has the largest effect on the production profile. Also, it has an impact on the effect of all the other parameters tested, especially on the effect of the confining layers. The confining layers play an important role during the simulation of the production process because they control the thermal recharge, and this enhances the lifetime of the geothermal project. The thinner the reservoir, the larger is the effect of the confining layers and the change in its properties and the more impact the thermal recharge has on the production profile. By examining the effect of the production parameters, the aim was to define a sustainable production design and strategy. It was proven that the production rate has a large impact on the lifetime of a geothermal project, and that an increasing well spacing enhances the sustainable use of a geothermal system. To enhance the sustainable extraction of geothermal energy from a geothermal system the production rate should be kept low. When making a production optimisation two rules of thumb apply to maintain a sustainable production. The first rule says that with a doubling of the reservoir thickness, the production rate can be increased by approximately 50%. The second rule says that with an increase of well spacing of 20%, the production rate can be increased by approximately 50%. Overall, this study emphasizes the positive effect of thermal recharge on the production profile and its enhancement on the sustainable use of a geothermal system. We can conclude that with a sustainable production design and strategy the production from a geothermal system can continue for generations.

To fulfil the new safety standards of the Netherlands against flooding in the future, a great deal of work needs to be performed to prepare the flood defences system, at a quicker pace than is currently achieved. For this reason the HWBP is researching methods which can improve the efficiency of dike reinforcement projects. This thesis was initiated to analyse what could be done in the transition period between registration of a dike reinforcement project at the HWBP programme and the start of the reconnaissance phase of the project, as it is potentially useful to utilize this time period. This thesis focuses on the impact of implementing monitoring and soil investigation earlier was analysed, because information collected before or during the transition period can be used for the benefit of the dike reinforcement projects. For this a theoretical case of the dike trajectory at Amerongen was used, for which piping is the dominant failure mechanism. The benefit in performing additional soil investigation and monitoring is dependent on the project phase in which the measurements are started and/or performed. The aim of this research was determine when the methods need to be implemented, how much investment is needed and what the expected benefit of the measures is. The benefit can be expressed in expected project costs in case of stronger parameters are found and in expected annual risk if weaker parameters are found. For the applied case dike trajectory at Amerongen the expected reduction in project costs is 19,4% of the initially estimated project costs if the measurements were performed or started early. In comparison, the expected project cost reduction for the common project structure is 13,3%. The investment costs due to monitoring and soil investigation was 4,6% of the estimated project cost when starting early and 4,1% for the common project structure. In conclusion, by investing 0,5% of the estimated project costs on starting monitoring and soil investigation early in the dike reinforcement project a 6,1% reduction in the project costs is expected.

Underground thermal energy storage (UTES) is an efficient technique to fulfill the heating and cooling demand of buildings. UTES uses stable subsurface temperatures store and extract energy. This study covers two types of UTES systems: aquifer thermal energy systems (ATES) and borehole heat exchangers (BHE). UTES systems in the Netherlands have seen a significant growth over the past years (Bloemendal, 2018) and are expected to contribute up to 20% of the heating and cooling demand of buildings by 2050 (Naber et al., 2016). As more UTES systems are installed, the risk of unwanted interaction between different system increases. However, ATES-BHE interaction is largely unknown.
The objective of this study is to gather more insight in the interaction of ATES system on the efficiency of BHE systems. A numerical model is used to simulate an ATES well near a BHE system using SEAWAT (Langevin et al., 2008). The model is used to run different simulations, from which the efficiency of a BHE system is computed under different circumstances over a five year period. Four conclusions are drawn from the results. First, groundwater and temperature interference from ATES systems affect the efficiency of a BHE system differently. Simulations show that the effect of groundwater flow induced by an ATES system always has a positive effect on the efficiency of a BHE system. The effect of temperature interference is dependent on the temperature of the ATES well. Groundwater was also found to interfere at larger distances between both systems compared to temperature. Second, the degree of interference is related to the distance between the ATES and BHE system. For distances smaller than 0.5 times the thermal radius of the ATES system, interference from temperature was found to be dominant in the simulations. For distances larger than 0.5 times the thermal radius of the ATES system, groundwater interference was found to be the dominant factor. The third conclusion is that the depth placement of the ATES well screen has little to no effect on the amount of interference on the BHE system. Fourth, it is important to realize that no energy is spontaneously generated or lost as BHE efficiencies increase or decrease respectively. Energy is simply exchanged between the ATES and BHE system through the subsurface. Whether that is disadvantageous depends on the energy demands of both systems. Most energy demands are imbalanced, meaning either cooling or heating demand is larger than the other. It is recommended to consider UTES system installations from a holistic point of view.

A transition towards more renewable energy sources such as wind- and solar energy is underway. These sources can be unpredictable with regard to energy production and therefore energy storage has become a major concern. A promising technique, Underground Hydrogen Storage (UHS), converts excess energy into hydrogen and stores it underground, after which, by reversing the process, the stored energy can be used when the imbalance between supply and demand is great. Hydrogen storage in salt caverns is particularly attractive because of their high sealing capacity, low amount of cushion required, the inert nature of rock salt and high possible injection and withdrawal rates. For energy storage purposes, these salt caverns are exposed to different cyclic loading conditions during operation, resulting in variations in stress in and around the cavern. Investigation of the mechanical response of rock salt under cyclic loading conditions is essential for the safety assessment and usability of the cavern. The response of the system to varying loading conditions can be mainly divided into two groups, either time-dependent or stress-dependent. The main focus of this thesis is to record the stress-dependent behaviour of rock salt under varying loading conditions. More specifically, it focuses on nonlinearity that occurs due to viscoplasticity. This phenomenon can be described as the rate dependent
behaviour of a material that occurs when a material exceeds a certain stress level, after which irreversible deformation occurs. This thesis describes the development of a 2D FEM (finite element method) simulator on an unstructured grid that captures the mechanical response. To model the stress-dependent behaviour, the viscoplastic model proposed by Desai is used. This model is
based on the non-associated flow rule and takes into account material dilatancy and compressibility. In addition, the model allows for hardening, the tensile strength of rock salt and variation in yield behaviour with pressure variation. Sonar data from cavern EPE S43 is utilised to test the simulator. This case showed that irreversible deformation occurs as a result of the stress-dependent behaviour of rock salt. For this specific cavern, the total working volume of the cavern decreased roughly by 0.0003% over three operating cycles, indicating that viscoplastic deformation itself does not pose significant risks to the cyclic storage of hydrogen in salt caverns.