The increasing demand for rare minerals, such as lithium, cobalt, and copper, driven by the growth of the world population and the transition towards sustainable energy technologies, has become a pressing concern. These minerals are crucial for electrifying the transportation sector through electric vehicle production and are in high demand for the thriving high technology industry. However, their scarcity and high prices due to supply shortages necessitate alternative sources to meet these demands. In recent years, deep-sea mining has emerged as a promising solution to address the growing need for rare minerals. The vast potential reserves in the ocean floor offer an enticing opportunity for exploration and extraction. However, deep-sea mining comes with its engineering and environmental complexities that require thorough investigation and understanding. This research delves into the experimental study of a Coandă-Effect-Based Collector, aiming to understand its behaviour regarding water entrainment and cohesive sediment erosion. The focus is on understanding the collection mechanism to minimize clay pickup and maintain low clay concentration in the discharged mixture. This is vital in mitigating the impact of deep-sea mining activities on the marine environment. This research provides valuable insights into water entrainment and cohesive sediment erosion in the context of the Coandă-Effect-Based Collector. The findings emphasize the significance of operating parameters and shed light on the complexities of the collection mechanism. Future studies should explore additional data collection to understand the influence of the secondary jet duct better and employ reliable methods for measuring clay concentrations in the discharged water. Overall, these findings have important implications for optimizing collector design and mitigating the environmental impact of nodules mining activities.

In this research, a new measuring method to detect shear parameters in fluid mud is proposed, namely using shear waves, or S-waves opposed to the conventional pressure waves, or P-waves. Currently, detecting fluid mud is done by the use of P-waves. This paper shows that conventional P-waves velocity measurements are unsuitable for linking velocities to the yield stress, which is likely caused due to gas in the mud. Opposed to this, S-wave velocities do show an logarithmic increase, which most likely can be linked to the yield stress development of fluid mud. Both S-wave velocities and yield-point measurements show an exponential increase over time and, because of this, it could be that there is a linear relation between them. The difference why S-waves are more suitable for shear-strength measuring is due to their nature of propagation. S-waves do not propagate through gas and are therefore hardly effected by gas production, opposed to P-waves. For this research, both P-and S-wave velocities are estimated from a transmission seismic experiment. Also, a frequency analysis has been conducted showing large similarities over time and for dissimilarities between different mud samples. The yield-point measurements are derived from a rheometer with the same mud sample used for the seismic experiments. Besides a velocity analysis from the transmission measurements, also a reflection measurement has been conducted. The aim for this is to detect converted P-to S-waves and to detect the Scholte wave. Furthermore, a dispersion analysis has been conducted, which is likely important since the relative change in S-wave velocities is small and the velocities are frequency-dependent.

The Port of Rotterdam experiences large amounts of siltation from the upstream rivers in its basins and canals every year. Furthermore, container vessels increase in size every decade and therefore require a larger navigational depth. These two factors cause the yearly amount of dredged material to increase. Currently, mainly trailing suction hopper dredgers are used to remove the large amounts of sediment, but these vessels come with high costs and operational time. A more time and cost-efficient dredging method is therefore desired. A potential solution to the increasing problems of costs and operational time by dredgers is the technique of water injection dredging. To make this technique as efficient and effective as possible, this thesis has the objective to measure and analyze flow and sediment properties for different parameter settings of water injection dredging and find the optimal parameter settings of this dredging technique on mud from the Port of Rotterdam. Large-scale experiments have been conducted in the water-soil flume of Deltares, where a jetbar was trailed (or run) over a bed 27 meters long and 0.5 meters deep of port mud while injecting it multiple times with water. A positive correlation is observed between the production rate and jet momentum. The production is related linearly with the jet momentum using the Vlasblom equation combined with a non-dimensionless empirical fitting parameter per run per traverse velocity. What is remarkable is that the intrusion depth by the jets increases with ascending runs while the jet parameter settings stay the same. The data shows that the difference between the mass flux by the density current and the mass flux stirred up by the jets when the sediment concentration of an undisturbed bed is assumed, increases between runs when an increased intrusion depth between those runs is observed as well. This indicates that the volume penetrated by the jets contains a smaller amount of sediment than was initially assumed, thus is disturbed by the previous run and is therefore decreased in strength. This decrease in strength results in a larger intrusion depth during the run itself in comparison to the previous run. The influence of the SOD of the jets is analysed by comparing runs with a SOD to runs without a SOD but with similar remaining jetting parameter settings. When a SOD is applied, the jet pressure applied to the bed is outside the flow development region and therefore the jet pressure decreases with distance from the jet nozzle. The mass of sediment stirred up by the jets, for a SOD of 300 mm, is lower in comparison to a SOD of 0 mm. The density current transports relatively more sediment, however, when a SOD of 300 mm is applied. So, if a large amount of sediment needs to be stirred up, and therefore a large intrusion depth is required, no SOD should be applied and when large horizontal transport by the density current is desired, a SOD outside the flow development region of the jets should be used.

The significant adverse contribution of the construction industry to greenhouse gas emissions and natural resource depletion has to be reduced. Regarding jetty platform structures, this challenge can be faced by designing for reusability, a promising concept for environmental impact reduction. However, this principle is not yet being widely implemented, leading to the absence of reusable jetty structures. This research aims to identify the feasibility of designing a jetty platform for reusability and the contribution of reusability to the environmental impact reduction of jetty platform structures. A jetty, that is being constructed in the port of Rotterdam during the execution of this research, was taken as a reference structure. By creating a design according to the Design for Disassembly requirements, while fulfilling similar functions as the reference jetty, a concept of a reusable jetty plat- form design was created. A numerical prediction model was created in the SCIA Engineer software so that the global behaviour and robustness of the structure were found when using simple connection solutions. Next, demountable connections were designed based on existing configurations from other applications. The practical aspects of assembly and maintenance were assessed through an interview with a maintenance expert from Port of Rotterdam. Furthermore, a brief study was done to investigate the possibilities of modularity and applicability to other jetties in the port. To quantify the environmental impact reduction, a life cycle assessment was performed, in which the impact of the reference structure was compared to that of three reusable structure variants: the reusable design, the modular reusable design and the modular reusable design using concrete with a lower impact. Due to the use of simple connections in the reusable jetty design, discontinuities in the displacements are found between elements. These cause limitations in the flexibility of placing the superstructure and may cause deformations in pipelines when those are placed on the platform. Therefore, a solution was presented to mitigate the discontinuities. Also, the reusable jetty has to be constructed with a larger crane than is conventionally used, which may cause hindrance to the surroundings. However, the duration of construction will be reduced. The results of the life cycle assessment show that the initial impact of each reusable variant was larger than that of the reference jetty. However, already for reusing once in the structure’s lifetime, this investment can be compensated when compared to replacing the reference jetty with a new structure. When assuming a structure is reused or needs replacement once during its lifetime, a tipping point was found when 24 to 44% of the structures are being replaced or reused, at which the investment is compensated. When not constructing the platform entirely directly, but adapting it when future requirements become more certain, potentially no investment is needed to be made. From the results, it can be concluded that reusability contributes to lowering the environmental impact of the jetty platform when it needs replacement or reuse at least once during its lifetime or when the given percentage of the structures are being reused once during this time. Thus, reusability can be applied to reduce the environmental impact of jetty platform structures.

When a ship reaches the shore, the water depth reduces and thus the under-keel clearance also reduces. The ship keel clearance influences the maneuverability of the sailing ship. In this thesis project, the link between the fluid mud rheology and its density is first investigated. The exponential relation reformulated between the density and yield stress necessitates the direct measurement of rheology for navigability. It was confirmed true that the yield strength grows exponentially with the density of the fluid mud. However, at higher densities of mud, more thixotropy is observed in the flow curves. Besides, the Power-law relations were found for the relation with volumetric concentration, for yield stress in agreement with fractal dimension theory. Second, quantification of the thixotropy effect of fluid mud is conducted to justify the importance of the time-dependency effect in the rheological modeling. We found that an unremolded fluid mud has high thixotropy even at high shear rates. However, diluted and remolded fluid mud at high shear rates found a negligible thixotropy effect. We also observed that Houska's modeling curve coincides perfectly with the flow curve of fluid mud at high shear rates, and also it integrates the thixotropy into the modeling. Third, the total resistance of a plate moving through fluid mud is measured and compared to the frictional forces calculated using the available analytical formulas of a plate moving in Bingham fluids and Power-law fluids. The moving plate is an abstraction of a vessel's keel sailing through the fluid mud. We found that the total resistance of the plate moved in fluid mud at low velocity agrees with the frictional force of a plate moved in Bingham fluids. As the velocity increases, the stagnation pressure becomes significant, and the deviation of the total resistance of plate and frictional force of a plate increases. Thus, to estimate the total resistance of a plate moved in mud, normal forces (stagnation pressure) and vortices at edges should be investigated because these need to be subtracted. The experimental data in this thesis are made resourceful to help researchers validate their Computational fluid dynamics(CFD) models in the application of sailing through the mud.

Recently, deep-sea mining has acquired renewed interest from commercial companies due to a rise in the demand of minerals and metals. Deep-sea mining is focussed on different minerals and rare earth elements found in the oceans that are increasingly used in the manufacturing of goods and products related to renewable energy. In order to collect these minerals, a mining operation at several kilometres depth has to be undertaken. Apart from the technical challenges that mining at several kilometres depth poses, also the environmental consequences receive a lot of attention and criticism from environmental agencies. Deep-sea mining operations are believed to cause damage to the environment by the sediment plume, as well as by producing light and noise which are absent under normal conditions at the deep ocean floor. The sediment plume is generated by the movement of the miner, but more importantly by the discharging of the picked up and unwanted sediment. This happens at the back of the miner using a set of diffusers. In order to acquire a better understanding of the effect that the initial concentration of the slurry has on the spatial spread of the sediment plume and turbidity current caused by the deep sea mining vehicle, experiments have been performed in which the initial concentration has been altered so that the characteristics of the ensuing current can be compared. The main objective of this research is to determine how changing the initial volumetric concentration of the discharge mixture influences the flow parameters after impingement and sediment flux inside the turbidity current for a constant sediment flux and discharge velocity. One of the most important assumptions for investigating the influence of initial concentration of the slurries has to do with the different phases of the discharged flow. During the initial phase, the density difference between the slurry and ambient mixture is thought to be dominant for the settling process, as the mixture behaves as one coherent fluid. After impingement on the bottom, the mixture spreads downstream as a turbidity current. During this phase it is the weight of the solids inside the slurry that causes it to settle. Because there are a lot of solids present in these slurries this process of settling is controlled by both hindered settling and flocculation. Flocculation is the aggregation of cohesive particles, forming a larger, heavier particle. Clay, which is cohesive, is expected to be present at most mining sites, resulting in flocculation to be an important factor in the process. The research has been performed by conducting a total of three different experiments. These experiments consist of pumping a pre-mixed slurry of water and spherical glass particles into a large modular tank, where is it discharged through a diffuser. For each experiment a mixture is prepared with a different concentration, which is discharged into the modular tank with three different flow rates in order to keep the sediment flux constant between each experiment. A total of three diffusers are used, one for each concentration. The diffusers differ in cross section in order to achieve a constant discharge velocity for all experiments. Experiments have been performed using both spherical glass particles and clay. The sediment flux is kept constant between different experiments as it is assumed that the sediment flux of real deep sea mining operations will be mainly determined by the width, cutting depth and velocity of the mainly vehicle. For performing measurements during the experiments, an ADV was used. This device is capable of measuring the velocity in three directions over a profile of 30 mm with 1 mm intervals. The ADV also measures the signal-to-noise ratio, which after performing a calibration can be used for calculating the concentration inside the turbidity current. Together this data can be used for determining the spatial spread of the turbidity current. Based on the findings of this research, it is believed that a higher concentration than the 1% volumetric concentration that is currently being assumed by deep sea mining companies could prove to be beneficial in preventing the spatial spread of the sediment plume and subsequent turbidity current. It is believed that in general, increasing the initial concentration of the discharged slurry, and thereby decreasing the momentum/buoyancy ratio of the buoyant jet, directly leads to both the velocity and concentration of the turbidity current to decrease over a shorter distance after impingement, while the impingement distance itself is also decreased for a higher initial concentration. As such, the total reach of the turbidity current resulting from the slurry discharge from a deep sea mining vehicle can be decreased by using a higher initial concentration of said slurry. It is believed that mainly the higher density difference with the ambient water plays a vital role in decreasing the spatial spread of the sediment plumes produced by deep sea mining operations. The higher density achieved by a high concentration results in the plume to deflect towards to bottom over a shorter distance and a decrease in turbidity current height. This decrease in height is beneficial for the later stage of the turbidity current in which the dying out is dominated by the settling velocity of individual particles.

Regular maintainance dredging is a large expense to the Port of Rotterdam, therefore the installation of sediment traps is considered. By increasing the bathymetry locally, an increase of local accumulation is expected and a decrease deeper in the harbour basin. This thesis describes the functioning of sediment traps in a stratified tidally energetic estuary, where sediment is supplied by the river and sea. A numerical 2DV representation is set up for the Botlek Harbour with the hydrostatic Delft3D software. A calculated salinity time-series by Operationeel Stromingsmodel Rotterdam (OSR) is combined with a measured water level time series for the same time period to describe the hydrodynamic boundary conditions. Simulations are done with a variable and constant Suspended Particulate Matter (SPM) time series boundary conditions, that were generated based on the measurements of De Nijs (2012). Flow expansion caused by the sediment trap reduces the flow velocity, but increases the turbulent kinetic energy locally. A reduction of bed shear stress is observed in the trap, except near the edges where an increase is observed. Density currents caused by salinity differences govern the vertical flow velocity distributions, while tidal filling causes the net exchange. The depth of the trap plays a significant role in the internal flow characteristics. The sediment trap changes the properties of the internal flow, which may change the hydraulic state of the flow, i.e. from supercritical to subcritical, resulting in large instabilities and even an internal hydraulic jump. Shallow sediment traps result in less frequent internal hydraulic jump and weaker jumps compared to deeper sediment traps. To investigate the dominant mechanism for the trapping of sediment in the sediment trap, a distinction is made between an erosion and a fluid mud scenario. The erosion scenario shows the largest agreement with the survey data, i.e. maintenance dredging data and Echosounder multibeam surveys, but contribute only marginally to the trapping of sediment. The fluid mud scenario yields the largest contribution to the trapping of sediment. The decreased amounts of accumulated sediment in the basin for substantial to lots of fluid mud behaviour may vary between 10% and 14%, depending on how this fluid mud behaviour is modelled. Various shapes have been tested on erosion and fluid mud scenarios. Both for erosion and fluid mud a more extreme choice of parameters might yield also more extreme results, this is however not considered realistic. The creation of an overdepth has shown to result in a marginal improvement in the capturing of sediment in an environment where erosion is important. A regular sediment trap decreases accumulation in the harbour basins by 2%. A trap twice as shallow increases this amount to 4%, but deepening the trap further may even enhance accumulation in the basins. A shorter or longer trap did not improve the situation. Installation of a sill did however result in a decrease of 6% compared to the situation without trap. It is concluded that this effect can be largely contributed to the internal flow properties and the presence of internal hydraulic jumps. The presence of an overdepth results in a significant improvement in the capturing of fluid mud flow. For the trapping of fluid mud flow, an overdepth results in 6% less sediment in the harbour basins no matter the depth or shape of the trap. The length of the trap did influence the accumulation in the basins. A trap twice as short shows an increase of 4 % of accumulation in the basins compared to a regular trap. A trap twice as long or installation of a sill results in similar accumulation in the harbour basins as a regular trap. For fluid mud flows, any type of overdepth decreases accumulation of sediment considerably. The amount of overdepth or the shape does not influence this. The length of the trap should be sufficient. A trap that is too short results in an increase of accumulation in the basins. For environments where erosion is important, only shallow sediment traps have proven to reduce accumulation in the basins. Traps that are too deep actually increase accumulation in the basins. A sill has proven to be the best measure for both mechanisms. If overdepth is desirable for navigation a shallow sediment trap is advised. This leads to a reduction of accumulation in the harbour basins for both erosion and fluid mud scenarios.

Phenomena like sea level rise, global warming and erosion together contribute to increasing flood risk in vulnerable coastal areas. As this flood risk increases, initiatives to mitigate the effects of climate change in the coastal zone are also increasingly sought. During recent years, the view that these measures should be circular has gained significant momentum. In line with this, the idea that sediment should not be treated as waste, but as a valuable product in a circular economy has been widely accepted. Within this theme, the sediment uses as resources in circular and in territorial economies (SURICATES) was created to develop and execute eco-innovative solutions for the reuse of sediments in Western Europe. As a part of SURICATES, over the course of a nine week pilot, a total of 500 tonnes of sediment was reallocated in a designated area in the Rotterdam Waterway, with the expectation that this sediment would be transported out of the Rhine-Meuse estuary into the North Sea. The SURICATES project is one of the first real large-scale efforts to reuse sediment for economic as well as ecosystem services. Effective implementation of the SURICATES project, however, requires a thorough understanding of the governing physical processes impacting the distribution of the deposited sediment locally. Furthermore, to assess the feasibility of similar future applications, efficient modelling of the pilot project is necessary. The work presented here aims to elucidate the hydrodynamic processes that are governing in the Rotterdam Waterway, within the framework of the SURICATES pilot project, and assess the reproducibility of these processes by (two) predictive models that are currently operational at the Port of Rotterdam. A special 6-hour monitoring survey was set up to measure salinities, velocities, temperature, and suspended particulate matter (SPM) along a transect crossing the reallocation location. In combination with a literature review, this dataset provides the basis for research into the predictive capabilities of two currently operational hydrodynamic models. Analysis of this dataset reveals the dominant terms in the momentum balance, the influence of Coriolis, the occurrence of internal waves, and the effect that all these mechanisms may have on the SPM distribution around the reallocation location. When the system dynamics are elucidated, the model performance of the two hydrodynamic models is assessed—both quantitatively and qualitatively. It is also investigated whether phase shifts are introduced in the models. It is found that the primary hydrodynamic processes in the Rotterdam Waterway are related to the barotropic tidal asymmetry imposed at the river mouth, the tidal excursion of the salt wedge, baroclinic exchange flow processes, and turbulence damping at the pycnocline. Turbulence damping at the pycnocline generally poses an upper limit to the (re)distribution of SPM over the water column, although field data suggests that this damping may not be sufficient to counteract diffusion processes locally. This effect occurs under certain forcing conditions and during low water slack. Furthermore, an internal Froude number analysis provides evidence for the possible generation of internal waves in one of the river’s bends. The evaluated models, however, are not capable of reproducing all of these hydrodynamic processes adequately. Although both models adequately reproduce water levels and the vertical velocity structure, they have difficulties predicting the pycnocline height. Additionally, it is found that both models introduce a small phase shift in the velocity and salinity prediction. The research presented here is a contribution to the understanding of the governing hydrodynamic processes in the Rotterdam Waterway, and the effect that (in)accurate modelling of these processes may have on future studies. Recommendations following from this research could improve future modelling practices.

The port of Rotterdam is located within the Rhine-Meuse estuary where a substantial amount of fine sediment transport takes place. Therefore, the port of Rotterdam is subject to significant siltation, requiring maintenance dredging to guarantee a sufficient nautical depth of fairways and harbour basins. To optimise the dredging strategy in the port of Rotterdam, a pilot study has been carried out wherein sediment is reallocated in the Rotterdam Waterway, during ebb, instead of offshore in the North Sea. Between May and November 2019, 210,000 tons of sediment has been reallocated. This pilot study has been carried out in the context of the larger EU-Interreg Sediment Uses as Resources in Circular and Territorial Economies (SURICATES) project. The main goals are to re-use the sediment as a resource and to reduce the sailing time of the dredging vessels. Both ideas comply with the Building with Nature philosophy; a concept gaining popularity over recent years in The Netherlands focusing on, amongst others the optimisation of dredging strategies. It is expected that the reallocated sediment is mainly transported offshore, while at the same time some of the sediment will nourish the river banks of the Rotterdam Waterway enhancing its flood resilience. This thesis focuses on understanding the fine sediment behaviour of the SURICATES pilot project on two different scales. This is done by analysing measurements and model hindcasts. The measurement campaign is set-up by Deltares and the Port of Rotterdam. For the model hindcasts an operational hydrodynamic and sediment model is used. On the small scale this is done by focusing on the behaviour of a single disposal over a tidal cycle. The large scale focuses on the cumulative long term behaviour of all sediment reallocations. For the small scale two measurement surveys are analysed. In both surveys it is found that a sediment reallocation executed by bow coupling is subject to mixing up to halfway the water column. Subsequently, the sediment plume is advected around and below the pycnocline. Further measurements in the mid field are lacking, but it is hypothesised that the majority of the sediment settles during subsequent low water slack. For the other execution method, drawing the bottom doors, which is used to reallocate the majority of the sediment, useful measurements are absent. It is hypothesised that the majority of this reallocated sediment is confined in the salt wedge and therefore mainly transported upstream over time. To assess the long term behaviour of the cumulative behaviour of all sediment reallocations, a different measurement campaign is set-up. In this measurement campaign, bed samples are collected prior to and during the pilot study to determine the change of the bed composition. In this campaign an indication for increased sedimentation related to the pilot study is found for nearly all the sample locations. The short term model study is set-up to enhance the understanding of the short term behaviour of a sediment plume, to derive an accurate source term for the sediment disposals and to carry out a sensitivity analysis. This sensitivity analysis is executed to derive the influence of differences in disposal method, timing of disposal, and uncertainties in the model. It is found that the execution method has the largest influence on the critical sediment fluxes on the short term, followed by the timing of disposal. From the long term model hindcast, in which the entire pilot study is hindcasted, it is found that 27% of the total amount of reallocated sediment flows downstream from the location of disposal and 73% upstream. These estimations are in line with the hypothesis and long term measurement results, but a thorough calibration of the results is lacking. To conclude, in this thesis a pilot study utilising a different sediment reallocation strategy in the port of Rotterdam has been investigated. This study shows that majority of the sediment disposed, in the current set-up of the pilot study, is estimated to flow upstream. In the sensitivity analysis, it is predicted that this might be caused by the timing of disposal or method of execution. It is also found that the initial behaviour of the sediment plume and the long term measurement contain a large amount of uncertainties. As most important recommendation for future work an expansion of the current measurement survey is proposed with at least two fixed locations: one downstream and one upstream of the location of disposal. In this way sediment fluxes can be established, which can also be used to verify and calibrate the sediment model.

The nautical bottom (the level at which contact with a ship’s keel causes either damage or unacceptable effects on controllability and manoeuvrability of a ship) should be associated to a measurable physical characteristic. Bulk density is typically used as a criterion for nautical bottom by many ports worldwide. However, the rheological properties particularly the yield stress of mud would be better parameters for defining a criterion for nautical bottom due to their strong correlation with the flow properties of mud and navigability. The density-yield stress correlation depends significantly on different parameters of mud such as organic matter type and content, clay type and content, particle size distribution and salinity. Therefore, a single critical value of density cannot be chosen for the nautical bottom criterion in a port like Port of Hamburg, where the above mentioned parameters are varying from one harbour location to another. This justifies the need for a study of the rheological properties (yield stress) of mud in Port of Hamburg.@en