Immersed tunnels are underwater structures consisting of prefabricated elements that are floated to the construction site and then immersed in place. These elements are typically composed of segments, with all structural connections between the segments and elements formed by shear joints or the shear keys. These shear connections are essential for restricting movement within the tunnel, ensuring both waterproofing and structural safety. However differential settlement, a common issue in such structures can introduce significant shear forces within these joints, posing a threat to the tunnel’s structural integrity. The performance of these shear joints is heavily influenced by the complex interactions between the tunnel and the foundation. The foundation and subsoil stiffness variability plays a critical role in differential settlement between adjacent tunnel elements, thereby directly impacting the performance of the shear keys.
The existing design methodology for the shear joint design used in Fehmarn Belt project, rely on techniques like Gaussian random field, Monte Carlo sampling, and joint statistics in the post processing
to model the influence of the spatial variability. While these methods provide detailed insights into the effects of spatial variability, their complexity, and the time intensive nature of their application could effect the timely delivery for large scale projects where efficiency is paramount. Thus, the main objective of this thesis is to develop a simplified approach to Soil-Structure Interaction (SSI) analysis that remains effective without the cumbersome detail of the existing design methodology. The purpose of this simplified approach is to offer a reliable alternative to the existing SSI methodology used in the Fehmarn Belt project.
The approach presented in this thesis simplifies the modelling of the combined stiffness variability of the subsoil and gravel bed beneath the tunnel. This approach utilizes a multi-linear Winkler Spring model. The soil stiffness parameters are derived from the CPT-NEN approach, and the combined stiffness variability of the subsoil and gravel bed is calculated using the spring-in-series equation. The soil
deformations, simulated in PLAXIS 2D, are translated into springs using the multi-linear Winkler Spring approach. This simplification forms the basis for the subsequent analysis performed in SCIA Engineer
software, where joint shear forces are calculated under various stiffness variability schemes and load levels.
The thesis concludes by comparing the shear response of the simplified approach with those obtained from the complex soil-structure interaction design in the Fehmarn Belt project, validating the reliability of the used approach in terms of safety. The comparison demonstrates that within acceptable tolerances, the simplified approach produces reliable results for the considered design conditions, taking into account the scope defined in the thesis.

The Netherlands faces major housing shortages. The total housing shortage is 390 thousand homes and this is expected to increase in the near future because fewer building permits have been issued in recent years. By 2030, the Netherlands will need to have almost a million new houses. To solve this problem, it is essential to build more residential buildings in the near future, but limited space is available. Therefore, the focus shifts to traditionally less conventional spots that potentially can be used to construct residential areas.

One of the proposed solutions is to create residential buildings near dikes, thereby using the dikes not only to combat flood risks but also to relieve pressure on the housing crisis in the Netherlands. To check if buildings can be built on or next to a dike, the assessment method of the Legal Assessment Instrumentation is currently used. However, only a basic assessment is prescribed for this, which is a very conservative approach. This conservative approach often leads to the building not being built or to overdesigning of the dike and thus higher expenses than necessary.

The objective of this thesis is to develop a level I reliability assessment method for multifunctional dikes containing a structure, leading to a less conservative approach than the basic assessment of the Legal Assessment Instrumentation (WBI2017).

First, the possibilities of construction near dikes were studied per water board. The possibilities for building near dikes are prescribed in the water board regulations, previously known as the by-law (Keur). Although the water board regulations vary for each water board, the rules regarding building near dikes are consistent, and almost nothing regarding construction can be done in the profile of free space. Interviews were also held with water boards. During these interviews, the regulations were discussed, including the non-technical obstacles with regards to building near dikes and solutions for them were proposed.

The biggest concern is regarding the management of the houses that would be part of the flood defence. One of the proposed solutions is to use people to regularly send photos to ensure the quality of the parts of the house that will function as flood defence or to use sensors which could measure deformations. This could save much time for the dike managers.

Next, it was determined what failure mechanisms can be affected by the presence of a building on or near a dike. The failure probabilities of macro-stability, piping and overtopping differ when a building is placed on or next to a dike and have been considered in the calculation of the failure probability of the dike. It has been argued by means of an event tree that the absence of a house has a 0.1% probability of occurring.

Subsequently, a case was analysed probabilistically using FORM analyses to demonstrate the difference in failure probability between the current and the proposed schematisation. This showed a 75% reduction in failure probability for the assumed cross-section compared to the current schematisation. The effect of new construction on a standard dike profile can both have positive and negative effects on the failure probability of the dike section depending on the situation. Compensatory measures can be taken to reduce the probability of failure.

Since it is time-consuming to perform probabilistic calculations for every situation, it was decided to create a Level I reliability assessment. Based on the probabilistic calculations, partial safety factors were derived that take the probability of the disappearance of a house into account. These partial factors were calculated per stochastic variable. This allows for a Level I reliability calculation to determine whether a dike cross-section with a house meets the required failure probability of the dike section.

It is concluded that incorporating the proposed level I calculation with adapted partial factors has a different impact for each situation but can, in some cases, have a 75% reduction in failure probability. This is based on the case study, which is elaborated extensively in the report. The developed level I reliability method ensures that existing buildings near houses are assessed more realistically compared to the current WBI assessment, which assumes a gap at the location of the dike. As a result, when this method is used, more dike cross-sections with buildings will meet stability requirements as it is less conservative than the current assessment, which only takes into account the negative aspects of the building. This means that fewer dike sections will be rejected, potentially saving both money and reducing inconveniences. For the design of new structures near a dike, this Level I reliability calculation can provide insight into possible locations for construction in the cross-section of the dike and the potential dimensions of the house. With this method it can quickly be demonstrated whether a multifunctional dike still meets the dike's failure probability requirement, which can also lead to an increase in building possibilities near dikes, as extensive customized assessments are no longer necessary.

Over the last years the critical state of existing quay wall structures have gained a lot of concern. With the focus on urban quay walls in Amsterdam, a lot of aspects could play a role which limit the possibilities for both the design and the construction. The focus in this research is placed at the structural efficiency of the design for renovation projects. By using a parametric approach (with Grasshopper/Rhino) in the preliminary design phase, a design solution with the lowest use of material can be found.

From the total of embankment within the management of the municipality, a scope has been defined focusing on the most critical quays with respect to the limited design space and high expected loads. Within the assumptions made, the developed parametric tool can be used to indicate an efficient design solution for which the positioning of the piles, the diameter of the piles and the thickness of the floor follow from the location-dependent input. The indication of the effect of geometrical properties with respect to the defined objective (minimizing the material use) could help in the consideration of the design requirements.

Apart from indicating the savings that can be made on the material use by improving the structural efficiency of urban quay wall design, this research also contributes to proof of the power to be found in a parametric approach. The repetitive character in especially large-scale assignments as the renovation of Amsterdam's quay walls makes it a highly appropriate method.

Deep sea mining is an upcoming industry that comes with many unknowns. One of these uncertainties is the interaction between the deep sea mining collector and the seabed. Allseas collaborates with DeepGreen Metals to collect nodules in the Clarion Clipperton Zone (CCZ) in the Pacific Ocean. The CCZ seabed consists of a very soft cohesive soil. During a blackout, the collector sinks considerably into the soil. It must be retrieved as losing such an expensive asset is not desired. The umbilical is intended to lift the collector from the seabed. However, the umbilical has its limits due to its lifting capacity. Therefore, research is done to estimate the breakout force of the collector and to find possible load reduction options to stay within the umbilical’s boundaries. The breakout process is time-dependent and contains multiple soil resistance forces. These soil resistance factors are the suction, adhesion, side resistance and added soil mass. The soil suction is the dominant force, adding resisting during a breakout. Different load reduction options (e.g. eccentric lifting, perforations) are discussed, to reduce the breakout force of the object. However, in previous research the extracted objects are rigid, while the tracks of the collector are flexible to some extent. Experiments are conducted to investigate the effect of flexibility on the breakout force compared to rigid objects. Four experiments are executed in the laboratory, to test four different effects on the breakout, namely: the flexibility, grousers, eccentric lift and in situ time experiments. A test setup is designed to execute these experiments and five different test samples are selected, varying in size and material properties. During the experiments, the samples are extracted from an artificial CCZ soil. The experimental results are used to calibrate and validate the model. The model is developed to simulate the breakout process and to make an estimation of the required force to lift the collector from the seabed. The model consists of three main components: the lifting mechanism, soil and the object that should be lifted. A combination of the literature survey, experiments and the model provides sufficient information to estimate the lifting force of the collector. Load reduction options can be applied to reduce the breakout force during a quick lift. During a slow lift the collector can be retrieved from the seabed without additional load reduction options.

The clay adhesion phenomenon has been problematic in multiple engineering projects involving soft cohesive soils. In this dissertation, the adhesive characteristics of offshore high plasticity clay will be analyzed in support to deep sea mining applications. Adhesion of clays are particularly relevant in 2:1 swelling clays, where the magnitude of the force is highly dependant on the clay properties itself, working conditions and the soil engaging component surface material. The most prevalent force in offshore saturated conditions arises from the suction forces between micro-channels in the clay and the soil engaging component. Methods to reduce this adhesive force were assessed, ranging from solutions such as vibrations and electro-osmosis, to modifying the soil engaging surface to break continuous contacts between the clay and component. The natural adhesion of two typical offshore clays were experimentally determined by interface shear tests for the shear adhesion and pull-out tests for tensile adhesion. Interfacial shear strength was measured for typical materials found in the offshore industry, that being steel, aluminium, rubber and a polymer coating. Results from the tests showed that materials do have an impact on adhesive stresses. Similarly, pull-out tests showed this variation pattern. The influence of pull-out rates and contact time on adhesive tensile strength were also assessed and showed to increase with faster rates and longer contact times, respectively. In application to a typical rotational cutterwheel in deep sea mining, a scaled test-setup of a rack of cutter-teeth was dragged through the test clay to acquire horizontal cutting forces with the utilization of the experimentally found natural adhesion in the interface tests. The found adhesion value for the test clays were utilized to validate the cutting clay model from "The Delft Sand, Clay & Rock Cutting Model" (Miedema, 2019). Practical results from the scaled experiment seemed to coincide relatively well with the theoretical model. It is therefore recommended to further investigate the use of experimental means to determine adhesion of clays to develop an even more accurate empirical model.

Drag in pipelines is composed almost solely of skin friction drag. The most common technique to achieve drag reduction (DR) is by adding drag-reducing agents. However, in the aerospace industry, various impressive passive drag-reducing techniques have been suggested to reduce skin friction drag in the past decades. Among these techniques, dimpled surfaces form a relatively unexplored terrain. Research into reducing skin friction drag in the turbulent regime by using dimples has been performed in the aviation industry since the '80s. The excessive amount of skin friction drag in pipelines forms an intriguing challenge to break new grounds. Several researchers investigated the potential of DR of turbulent flows using dimpled channels. Even though most of these studies that found DR are disputed, studies published at the National University of Singapore (NUS) obtained positive results time and again. NUS's exact test setup was reconstructed at Delft University of Technology, which has not been done yet as far as the author of this report is aware. Identical pressure measurements were performed, yielding an absolute DR of ≈ 5%, which is slightly less than what was obtained at NUS (>7%). Flat plates return a DR between 8-15%, dimpled test plates returned at DR between 12-20%. The test plates were covered for 99.5% with diamond-shaped dimples of 100 mm long and 50 mm wide. In total, 29 pressure taps were used to determine the change in drag in an 8 m long channel of 20 mm in height. Tests were done at Reynolds numbers, based on half channel width and centerline velocity, between 6,000 and 40,000. Accurate results were perceived up to a Reynolds number of 21,000, likely due to test-setup limitations. Multiple verifications such as two-dimensionality of the ow, comparison of theoretical and experimental skin friction coefficients, and instantaneous pressure tests were used to allow for an objective analysis. The pressure measurements were also supported by 1D hotwire anemometry (HWA) tests and surface oil ow visualizations (SOFV). The majority of the investigated boundary layers were absent of anomalies. It should be mentioned that the viscous sublayer could not be captured, neither a quantitative momentum analysis was performed. However, a shift in the velocity profile, acquired at the same test location, for different test plates was observed. Furthermore, an increased velocity near the wall was observed for dimpled test plates. Surface oil ow measurements did show similar ow patterns to what was recorded at NUS. However, the actual behavior is not investigated through HWA. Hence, it cannot be confirmed nor denied if the change in drag is a consequence of these near-wall ow mechanisms. SOFV did not show irregular ow structures such as ow reversal. Finally, tests were performed with a correction for test volume increase caused by the dimples. After this correction, the drag over dimpled plates increased instead of reduced. Considering other studies on dimpled surfaces that also found an increase in drag, it is strongly believed that the positive effect of dimples in turbulent channel flows does not stem from skin friction drag but rather from the increase in channel volume. Although the precision of the results was relatively high, the accuracy of the wind tunnel was insufficient. Additional research is required to narrow down the 8-15% error that was obtained while testing at plates.

Offshore pipelines represent major items in the oil and gas industry nowadays. These submarine pipelines are usually covered with backfill for protection and a well-known method for this is sand backfilling with a trailing suction hopper dredger (TSHD). Although pipeline installation with a TSHD is a developed technique, there are still some challenges regarding uplift movements of the pipeline during the backfill procedure. This action is called pipeline flotation, which is a frequently occurring problem during the sand backfilling process and the costs for repair measures afterwards are very expensive. Accurate modelling of the sand backfilling process over a pipeline can lead to significant cost reductions by optimising the sand backfilling technique. Pipeline flotation is induced by the development of upward buoyancy forces from the sand-water mixture on the pipeline. If the weight of the pipeline is not sufficient enough, it will experience uplift movements during the backfilling process. The purpose of this research is to develop a better understanding of the mechanism of pipeline flotation. Due to a lack of available field data, it is anticipated that a set of laboratory experiments will provide a better insight into the parameters involved in pipeline flotation during sand backfilling. This research builds on the study Yang (2020), in which a small-scale set-up and 2D calculation model are designed to perform experiments concerning pipeline flotation during sand backfilling. A total amount of 50 experiments is performed with Geba Weiss sand in four different stages: with horizontal discharge, vertically upward discharge, elevated initial pipe positions and increased pipe specific weights. The set of experiments have provided better insight into physical processes that influence pipeline flotation during sand backfilling. The discharge of the sand-water mixture is dominated by its sedimentation and dispersion, so the model is based on empirical equations and the sedimentation theory. The main conclusion regarding the static force balance on the pipe is that the degree of pipe embedment influences the magnitude of an additional frictional force working downwards on the pipe body. A new approach for assessing this frictional downward force, due to the presence of sand that has deposited, is described and added to the model. In the small-scale experiments, this influence plays a significant role in pipe flotation triggering. An undesirable result from the small-scale experiments are the additional hydrodynamic effects from the fluid in the experimental tank, which are induced by the geometrical constraints. A pipe flotation limit was found in the parameter of sand volume concentration in the surroundings of the pipe. This flotation limit was defined at a domain concentration of approximately 7.5% for the experiments with a pipe specific gravity of 1.03. The boundary of flotation for heavier pipes was not achieved in this research, but evidence points towards a significantly higher flotation limit. The discharge flow rate and the total discharged sand volume are the key factors for development of domain concentration in the small-scale experiments. With the acquired data as a strong foundation, additional research regarding pipe flotation during sand backfilling is recommended. As there is still a strong variation in several important input parameters in the small-scale experiments, a Computational Fluid Dynamics (CFD) analysis is suggested to relate the domain concentration to the input parameters at every moment in time. Additional 3D experiments on a larger scale are also recommended to optimise the sand backfilling process and validate the CFD analysis. From this analysis, a prediction can be made regarding the boundary of pipeline flotation on the seabed when discharging with a TSHD. Moreover, additional research regarding the stress and drainage conditions underneath the pipe is proposed to validate the cause and accuracy of the relatively high friction coefficients. Finally, a model could be built to examine the friction force generated on the pipe due to its embedment. With this method, the suggested approach of the frictional resistance due to pipe embedment could be further analysed.

Geogrids are commonly used for reinforcement of soils in construction of railway and road embankments and bridge abutments. A relatively new application of geogrids is the anchorage of sheet pile walls, in which one or more layers of geogrid are attached to the sheet pile wall. This type of anchorage is particularly suitable for projects with sufficient space behind the sheet pile wall. This anchorage system has some mayor advantages in comparison to conventional sheet pile wall anchors as it is cost-effective and requires less steel. Moreover, prestressing is possible during construction and pile foundations can be installed through the geogrids. An analytical design calculation method for this type of anchorage is not yet available in the Dutch design guideline for the design of sheet pile walls (CUR166). The demand for short anchorage systems because of the commonly limited space behind sheet pile walls, shifts the focus of the design to the minimum required length of the geogrid-anchorage.
This report makes a first step into the formulation of a design-calculation for the mobilised anchor resistance as a function of the length of the geogrid(s) at ultimate limit state. By means of a 1g small-scale physical model and a 2D finite element model (PLAXIS) of the small-scale physical model, the global failure mechanism and soil-geogrid interaction have been analysed. In a series of these experiments, an 18 cm long geogrid anchor was connected to a 30 cm high sheet pile wall and installed in sand in a small transparent test box and loaded with a strip footing load. In addition, experiments were conducted while varying several features, among which the number and length of the geogrid anchors and the location of the slip footing load.

This study aims for a software tool that predict secondary settlements in soft layers on which secondary dikes are founded based on cone penetration test data. In the literature study five equations have been found that relate cone resistance and friction ratio to volumetric weight and over consolidation ratio. With the volumetric weight and over consolidation ratio the NEN-Bjerrum settlement parameters can be determined and with that the strain for a layer. After this study the focus lies on developing a software tool and the resulting output. In the end it seems, qualitatively, that the results are not useful in engineering practise because the resulting settlements are unexpectedly large.

To date, many fire accidents have occurred in tunnels all over the world. In the worst cases, there were catastrophic consequences with numerous human casualties and significant economic impacts. In the occurrence of such tunnel fires, besides the primary concern of saving human life, ensuring a certain level of structural integrity is also desired. Looking from the latter perspective, this thesis is focused on the fire-induced thermal exposure in concrete tunnels, aiming at coupling numerical simulations of idealized fire scenarios in computational fluid dynamics (CFD) software with the use of FEA for the analysis of structures, moving towards a performance-based approach in replacement of the currently adopted prescriptive approach.
In this sense, fire imposes one of the most hazardous conditions for concrete structures, characterizing severe thermal degradation of the mechanical properties of the material. During fire exposure, steep thermal gradients are formed within the concrete structure. Those will always lead to the development of thermal stresses, the state of which being determined by several conditions (i.e. elastic modulus, thickness and supports). Besides the structural consequences of a fire, this thesis also deeply investigates the interface between a fire and the structure, which involves the interaction of three different modes of heat transfer, namely conduction, convection (related to the gas temperatures generated by a fire), and radiation (related to the radiation temperatures generated by a fire). While conduction within the solid phase regulates the amount of heat absorbed by the structure during a fire, radiation overcomes convection and becomes the primary mode of heat supply to the structure. The adiabatic surface temperature (AST) combines both the radiation and convection contributions to the total heat transfer to the structure into a single term, fully characterizing the fire phase in the structural analysis. Based on this concept, the differences between the two methodologies (i.e. prescriptive-based and performance-based) are exposed. From the prescriptive-based perspective, the development of the RWS curve and its indistinct use among protected and unprotected concrete tunnels is deeply discussed, together with the current fire resistance furnace tests. For the performance-based approach, the thermal exposure generated by two pool fire scenarios (200 MW and 30 MW) within the Piet Hein tunnel is addressed and the effects of longitudinal ventilation are highlighted.

Ground improvement in the form of soil compaction plays a important part in reclamation projects. The development of the Cofra Roller Compaction (CRC), a non-circular impact roller, has proven to be valuable in these projects. However, the heterogeneity of the subsoil causes locally a non-uniform degree of compaction. Traditional compaction control tests are limited in measuring depth, expensive and cause time delay. Therefore, the Continuous Compaction Control (CCC) and Continuous Impact Response (CIR)method were developed
in order to provide more real-time information of the compaction based on the response of the drum of the roller. The aim of this study is to develop a semi-empirical energy model which is based on the contact forces of the roller-soil interface as most CCC systems, but also uses field test data as was given in the CIR system to validate this model. The relevant parameters needed for this model were obtained from the field test conducted for the HES Hartel Tank Terminal project in Rotterdam. These included the impact acceleration, the cone resistance, the in situ density, the dynamic modulus and the dynamic plate load test velocity. Two methods are considered in this thesis and both aim to reproduce the measured values from the dynamic plate load test during the field test. The first method considers the acceleration signals and includes double numerical integration of these signals to obtain the displacement, while the other considers modelling the roller as a dynamic plate load test and obtaining the displacement from solving a 2-DOF spring-mass-damper system.
However, after analysis of the motion of the roller, it was observed that due to the non-circular shape of the roller, a wedge effect was created where horizontal shearing forces caused loosening of the soil. This inhibited soil compaction up to 0.5 m depth. The impact acceleration signals were thus not representative of the soil compaction. Nonetheless, the DPL-Soil model was proven to be successful in correlating the soil settlement to the dynamic modulus. This study considers a silty sand, so further research should be carried out to obtain correlations for various soils. In order to develop the semi-empirical energy model, it is thus recommended to capture an accurate acceleration response. This can be done by placing accelerometers at a minimum depth of 0.5 m, replacing the 8G accelerometer with e.g. 16G accelerometer and increasing the sampling rate to at least 1000 Hz. In order to filter out the soil variability, a field test with the roller should be performed on a homogeneous sand without fines. Correlations can then be drawn again for the same field tests performed in this thesis. Finite Element Modelling (FEM) could be used to model the interaction between the non-circular shape of the lobe, the rolling motion and the soil. This might form a better correction method for the acceleration signals than those explained in this thesis. Low frequency geophones can be used to measure the velocity directly. This because low frequency data of the accelerometer should be removed and the roller works on a low frequency. The load imparted to the ground could also be measured directly by burying earth pressure cells at a minimum depth of 0.5m and at various depths to get a more accurate representation of the pressure distribution through the soil layers. By using other numerical integration methods such as Simpson’s 3/8 rule and Boole’s rule, the numerical accuracy of the displacement response of the roller could also be improved.

The objective of this research is to explore the possibilities in the use of digital twins towards the maintenance and operation of tunnels. This is explored by looking at the end users of the technology, to profile their needs and requirements and consider a digital twin design that focuses on this. This research is the start of a human centred design for a digital twin and provides the opportunity for further investigation of applications and discussion of their usefulness. To map out the functional needs of facility managers within the Dutch tunnel sector, ten interviews were compiled. These interviews are based on digital twin literature in other sectors. The discovered needs within the interviews are analysed for patterns and compared to the characteristics of digital twins. This comparison is validated through a focus group with two digital twin experts and is done to consider if digital twins may offer opportunities for the needs mentioned. It is found that for a large majority of the identified functional needs of facility managers requires the mirror like characteristic of a digital twin, when focusing on the needs related to tunnel behaviour. A digital twin that is designed for the identified needs, should focus primarily on decision supporting services for these facility managers, in other words, providing them with relevant data about the tunnel, at the right time and in a comprehensive manner. An indication is given towards seven digital twin implementations that could benefit a tunnel facility manager. The first two are the monitoring of energy use, and monitoring the health of the tunnel system. It is concluded that energy use should be accounted for in a digital twin, and that the monitoring of system health is required for the quick understanding of problems in the tunnel and stakeholder management. The next three are predictive applications: predicting dependent relations between technical tunnel systems, maintenance scheduling, and operational simulations. These applications help anticipate risks during tunnel processes and provide opportunities for reaching better informed decisions regarding maintenance tasks, problem management and configuration management practices. One application, namely energy optimisation, can be considered fully autonomous, as such is not for decision support, but rather for tunnel optimisation, towards the control of energy use of tunnel technical installations.

In this work the installation process of a cone penetrating into a sand system is modelled using a 2D-axisymmetric material point method (MPM) model in order to investigate the installation processes and to predict the plastic radius. One meter of cone penetration is modelled under a surcharge of 50 kPa. The used constitutive model is Mohr-Coulomb Strain Softening (MCSS). The validation of the model has been conducted by comparing the MPM results to those obtained from laboratory experiments performed by Arshad et al. (2014). It was found that the qualitative behaviour from the MPM model and the experiments were in agreement but the quantitative behaviour showed some discrepancies. These discrepancies could be caused by the fact that, in the MCSS model, the stiffness is constant and independent of stress which it is not in reality. The performed sensitivity analysis showed that the stiffness has the most influence on the numerical predictions further adding to the importance of accurately capturing the soil stiffness throughout the simulation. The 2D-axisymmetric MPM model showed to have the potential to be a good tool for modelling the installation process of a cone and predicting the plastic radius.

First of all, an overview was created of different problems that can occur by the construction of cast-in-situ concrete piles, discussing the mechanisms that cause these problems. From the overview it was concluded that little information is present about the exact cause of excessive bleeding. Two possible causes were identified, excess pore water pressure in the surrounding soil caused by the pile installation and concrete stability, these are further researched. Comprehensive measurement data of the hydraulic head in an intermediate confined sand layer, during the installation of displacement piles, showed a consistent trend. During the descending phase a large increase in the hydraulic head was measured which can be described by volume displacement in the sand layer. In addition, a cumulative effect in the hydraulic head was found at the start of withdrawal of the temporary casing as the excess pore water pressure, resulting from the volume displacement, was not fully dissipated. During withdrawal, two additional pore water pressure increments can be distinguished. The direct increase starting from the onset of withdrawal has been interpreted as being caused by the reaction force of the machine on the ground resulting from the pull up force on the casing necessary to get the casing in motion.
Unfortunately, no conclusive cause was found for the second increase in hydraulic head regarding the processes that take place during withdrawal. This calls for further research as the hydraulic head after withdrawal will influence the interaction between the fresh concrete and the surrounding soil. Then a literature study on (excessive) bleeding in cement based materials was performed to assess how concrete stability influences the initiation of bleeding. The literature study showed that in order to capture the full bleeding phenomenon three processes can be distinguished. Sedimentation, Consolidation and Cement Hydration.

During the advance of a tunnel boring machine (TBM), the torque applied to rotate the cutterhead must overcome the resisting moments acting on it. Hence, one of the major concerns of TBM design is to determine the torque and power requirements of the excavation machine. The first empirical approach for torque estimation was developed in the 80’s by JSCE. This estimation fits the recorded mean torque for 5-8m diameter projects, but overestimates torque as TBM diameter increases. Newer approaches estimate TBM torque and thrust requirements as sum of multiple components, focusing on the friction between ground and cutterhead. However, the recommended or selected friction coefficients range between a wide interval (typically 0.05-0.75), depending on soil and operational conditions. Consequently, the torque and thrust estimations relying on the above-mentioned friction coefficients can be considerably imprecise, as well. Previous research regarding soil-machine/steel friction coefficients has been collected and studied. Successively, interface shear tests have been performed at TU Delft, to study whether and how friction coefficients could be determined consistently in the laboratory. Three soil types have been examined, ranging from coarse sand to kaolin clay. A metal plate cut out from a worn TBM cutterhead has been added to a direct shear apparatus to test the abovementioned soils. The latter are either water saturated or treaded with bentonite or foam, to assess the influence of conditioners on soil interface friction. Bentonite slurries and foam suspensions have been prepared in the laboratory using common industry products. Overall, in excess of 60 interface shear tests have been performed, considering various permutations of soil, load and conditioning. Results show that lubricated friction coefficients (i.e. when soil samples are conditioned) are up to 25% and 50% lower than for water-saturated conditions, for sand and clay respectively. A direct shear apparatus proves to be useful to study and select friction coefficients for TBM preliminary design, as it provides satisfactory results for non-conditioned and bentonite-conditioned soils. The same apparatus, however, cannot fully capture the lubricating effect of foam on sand. Improved estimation of friction coefficients requires more advanced equipment, or substantial modifications to the direct shear apparatus.

Deep Soil Mixing is an often-applied technique in the reinforcement of embankments, but little has been done to investigate and understand its behavior when used in excavation projects. The present research presents a database of the results of previous studies on the Deep Soil Mixing technique in Scandinavian soils. An expression that can estimate the improved soil strength when a specific binder content and binder ratio is mixed with the soil is proposed and its pertinence is tested with two full-scale tests. The proposed mathematical expression to predict the improved strength yields a good representation of the available data. The full-scale tests, in which a braced steel sheet pile wall interacts with panels of DSM overlapping columns are used for back-calculating the improved soil strength and stiffness properties. It is observed that the weighted average procedure for calculating properties should be used with care and that the loading conditions affect the strength and stiffness that the improved soil can develop. The drained analysis with a fixed friction angle and a cohesion intercept estimated from the undrained shear strength is the suggested design procedure to assess deep excavations involving improved materials.

Reinforcing levees with traditional methods is becoming more difficult in the Netherlands. Often there is a lack of space near the levee or it is desired that the landscape is maintained. Because of this, alternative methods for reinforcing levees are still sought after (CUR-commissie C141, 2007). In this study, the technical feasibility of a possible alternative reinforcement method for regional flood defences is studied: mass stabilisation. Mass stabilisation is a soil improvement technique with which soft soils are mixed with a binder on site and in-place to create a stronger soil layer (Forsman et al., 2015). It is presumed that mass stabilisation requires no extra space at the levee, does not affect the landscape and requires little transportation of materials. For determining the technical feasibility of applying mass stabilisation for reinforcing regional flood defences, three criteria have been examined. First, the ability of mass stabilisation to solve a stability deficit at levees was examined using two-dimensional stability analyses. Secondly, the achievability of the required effective strength parameters in compliance with Dutch standards was examined in the laboratory. Thirdly, the practicability of mass stabilisation at levees was examined using two-dimensional stability analyses. Although the results of this thesis have shown that mass stabilisation is a technically feasible technique for reinforcing regional flood defences, further studies will be required before a definitive conclusion can be drawn. It is therefore recommended that additional analyses into the practicability are carried out and that the relationship of the properties and the variability thereof between soils stabilised in the laboratory and the field is studied.

Currently wind turbines are a popular source of renewable energy. Royal HaskoningDHV designs foundations for these turbines. Design optimization of these foundations becomes more and more important due to the growing demand for renewable energy, the development of increasingly large wind turbines and intensification of competition. Design improvements can reduce construction costs, and also reduce the carbon footprint of the tower foundation. Today these foundations are designed using the Eurocode in combination with the results from linear analysis of a 2D model. Expectations are that this yields a conservative model. A 3D non-linear model is expected to provide a more detailed insight into the actual structural behaviour of such a foundation. Specifically, the distribution of concrete and reinforcement stresses and strains can be found, and used to determine whether, and where, reinforcement can be reduced or should be increased. To obtain a non-linear 3Dmodel, first a linear 3D model is developed, starting fromthe existing 2Dmodel. Subsequently the results of the two linearmodels are compared. Once the linear 3Dmodel is deemed to function satisfactorily, it is further developed to incorporate non-linear material properties and reinforcement, taking into account observations made in the linear analysis.
Simplifications made for the 2D model cease to hold. Besides minor details, the pedestal, that was left out of the scope for the 2D model, is introduced in the 3D model. Additionally, the connection between the foundation piles and the structure are placed at the underside, instead of at mid-height. Results of the
2D and 3D linear models are generally similar. However, small differences were observed. In general, these differences can be attributed to these two main modelling differences. Modelling in 3D opened up more possibilities for detailing of the supporting foundation piles. However the effects on the results for different support cases was minor. After comparing the linear analysis results, the next step is a non-linearmodel. The non-linear 3D model includes several non-linear aspects. Reinforcement was incorporated. Non-linear constitutive models were studied and chosen for concrete in tension and compression as well as for the reinforcement steel. Connections between different parts of the structure, such as the anchor cage, were also modelled non-linearly. The results of the non-linear analysis seems to provide an improved insight into the structural behaviour of the foundation structure. More detailed information about concrete strains, reinforcement stresses, crack progression and displacements can be shown, and used to verify, or disprove, assumptions based on the 2D linear analysis. However, problems with non-convergence occur before the expected failure load without a
satisfactory structural explanation. Therefore the model does not provide a plausible structural failure load. Because no ultimate load was found it is difficult to determine whether, and if so, how much the applied reinforcement can be reduced. Nevertheless, the model could be used in a more qualitative way to show and describe where stress concentrations will occur and how the structure will deform. Internal splitting cracks are seen outside of the centre of the structure where only limited reinforcement is present. These splitting cracks may be a cause of model instability. Design alterations can be made to increase the load for which non-convergence occurs. An increased the ultimate load is found when splitting
reinforcement is elongated, or when the amount of applied prestressing load on the anchor cage is altered. Even applying a simply modified constitutive concrete model, to represent steel fibre reinforcement, appears beneficial. However, these alterations may only improved the behaviour of the model, while still no actual
failure mode is found. It cannot be said without a doubt that these modifications will improve the structuralbehaviour of the actual structure. Further research may lead to a solution for the model instability and consequently enabling its use to optimize the reinforcement design.

In total 326 terpen in the Netherlands are classified as national monuments. A large portion of the terpen are located in the province Groningen. Groningen is often in the news, because of the earthquakes that took place, which were caused by the gas-extraction activities. The earthquakes caused damage to infrastructure and they can also be a threat to the stability of the terpen. Since the earthquakes can lead to soil liquefaction. The goal of this report is to investigate the risk of liquefaction to the terpen due to induced earthquakes. Furthermore, fine sands was the most liquefiable soil type. The Naaldwijk and Eem formations have the highest liquefaction potential based on their soil compositions, densities and age. The Naaldwijk formation is the most prone to liquefaction since it is located more shallow in the underground. Afterwards, cone penetration test data was used to evaluate the soil classes, soil unit weights and soil behaviour indexes. The soil behaviour index values were used to asses the liquefaction potential. In the end, none of the three chosen terpen were liquefiable. Moreover, 2D and 3D visualizations were made in order to better understand the heights and slopes of the terpen.

Dikes constructed of a sand core, clay cover and natural vegetation as (landside) slope protection are common flood defence structures in the Netherlands. The design parameters, such as the crest height of dikes, are determined through risk assessment to reduce the remaining probability of a failure mechanism, such as overflow. Little is known about the exact process leading to failure of the typical Dutch dikes in case the failure conditions actually occur. The most notable floods in the Netherlands have all been caused by dike breaching, where local damage in the dike lead to breach formation. This research describes the process of breach formation due to overflow and determines what design parameters affect the resistance of a dike against breaching. The proposed model (BRAM, a Breach Resistance Analysis Model) combines existing methods to determine the time-to-failure of the grass and clay cover with a newly developed process-oriented headcut erosion model. The model assesses the total time-to-failure of a dike through sequential failure of its components. The following process is simulated. Overflow over a dike causes a turbulent flow along the landside slope, resulting in local damage to the grass cover on either a prescribed weak spot or slope transition. The clay cover is subsequently eroded and the granular core material becomes exposed to the flow. A key assumption in the applied method lies in the fact that every newly exposed layer is less resistant to erosion than the layer above, resulting in slope steepening. Therefore, a near-vertical cliff, referred to as a headcut, is formed. When the overflowing water no longer follows the profile of the steep slope, a cascading flow, resembling a waterfall, forms a scour pit. The turbulent flow in this scour pit also erodes the core material of the dike, allowing horizontal erosion to undercut the slope. The undercutting of the slope causes the headcut to tumble over, moving the headcut and jet impact point to move towards the waterside slope, essentially restarting the scour process. This iterative process continues until the invert height of the dike is lowered to zero and the overflow rate is increased further. Model validation shows good agreement with test results on both large and small scale, as long as the assumptions regarding the structure of the dike hold (a dike profile consisting of a granular core under a clay layer and grass cover). When applied to three case studies, the BRAM-model predicts a similar total time-to-failure as the most advanced current model, posed by d’Eliso (2007). The predicted time-to-failure for the grass cover shows a significant difference. The BRAM-model predicts the grass cover to fail significantly faster than the model by d’Eliso (2007). This difference is offset by a longer predicted time-to-failure of the clay cover. Finally, the proposed model predicts a 50% slower headcut migration rate, as compared to the results by D’Eliso. This is a result of the more advanced description of the headcut erosion process. As the time-to-failure of the headcut migration phase is relatively short compared to the total breach formation process (between 10% and 25%), the total predicted time-to-failure is quite similar between both models. The main advantage of the BRAM-model is its suitability for design testing. The main weakness remains the unpredictable location of headcut initiation, which depends too strongly on spatial variation of the resistance of the dike to be predicted accurately, based on available data. Design parameters to increase the time-to-breaching have been identified. The most relevant were the steepness of the dike slope and thickness of the clay cover. Sensitivity analysis showed that the steepness and thickness of the clay cover, but also the porosity of the core material can be adapted to increase the time-to-failure of a dike. A breach-resistant dike may be designed for a limited overflow duration. Case studies showed three test dikes to sustain an overflow rate of 100 l/m/s for various hours by the grass and clay cover. As soon as the core material becomes exposed, the breach formation process accelerates significantly. The exact duration depends on the profile and construction material of the dike.