Efficient sediment management is crucial to maintain accessibility into the port. This thesis investigates the application of the bed leveller in conditioning pre-consolidated mud, comparing its efficiency and impact on turbidity with that of the water injection dredger. The research is conducted for pre-consolidated mud from the Botlek in the Port of Rotterdam. Instead of traditionally reallocating the dredged material, the mud’s properties are modified so that it is safe for vessels to navigate through the mud. The WID is the primary conditioning vessel at the Port of Rotterdam. Since maintenance dredging is a logistical challenge, however, it is attractive to optionally deploy other vessels for conditioning purposes. The bed leveller, a type of plough normally used to level the port’s bed, could potentially be used for condition ing. It is cheaper to deploy and more easily accessible for the Port of Rotterdam. Therefore this study investigates if the bed leveller can achieve comparable results as the WID regarding conditioning dredging. To accomplish this knowledge, the research includes the design of a conditioning plough and testing and comparing it to the conventional plough and WID on a laboratory scale. The different treatments on the pre-consolidated mud are measured on density, yield stress and turbidity so the outcomes point out the differences in conditioning effectiveness and impact on turbidity. Furthermore, experiments are executed to discover what is needed to successfully condition pre-consolidated mud and the influence that frequency in a conditioning activity has. To support the findings from the laboratory, field tests are con ducted with the bed leveller and the WID as well. This experiment also gives insight into the conditioning efficiency in terms of production rate, costs and fuel consumption. The findings are that an improved design of a new piece of bed levelling equipment, based on research and experience in the field of agriculture, can increase the ability to condition mud. Stirring and mixing, breaking up cohesive bonds within the mud and suspending it, are key for successful conditioning. Increasing frequency in a conditioning activity, increases the effectiveness of conditioning as well, however this relation stagnates. Furthermore, the bed leveller can indeed condition pre-consolidated mud like the WID can. Although in comparison, a higher dredging frequency needs to be applied, for the strength and density of the mud to be reduced just as much. Thus in terms of production rate, the bed leveller is a lot less effective than the WID, resulting in higher average costs and fuel consumption per volume of effectively conditioned pre-consolidated mud. In terms of impact on turbidity, the bed leveller has less effect than the WID and the design of a new plough specifically for conditioning, contributes to reduced environmental impact.

Sedimentation is a common issue in navigating through channels, berths and anchorages of many ports and harbors. In order to address this issue, maintenance dredging can be done in three different ways; relocating of the sediments, keeping the sediments in place, or dredging with nature and using the natural currents to remove sediment. Trailing Suction Hopper Dredging (TSHD) is currently the preferred method for dredging and relocating sediment, however, this method is both costly and time-consuming. As a result, more nature-based solutions are becoming attractive, like the Water Injection Dredger (WID). The Underwater Plough (UWP) is another commonly used method usually for dealing with irregularities in the seabed. Harwich Haven Authority has recently developed a new dredging technique called the Tiamat, this is a new agitation dredging method and a potential environmentally friendly solution. The Tiamat employs a water injection technique to dredge sediment from the seabed. The system injects water into the seabed to fluidize the sediments and then uses a suction pump to bring the sediment plume higher in the water column, such that it can be carried away by the natural currents.

To ascertain the boundary conditions for the Tiamat, tests were conducted at three locations in the Port of Rotterdam, each with different sediment classifications (cohesive and non-cohesive), current strengths (high and low), and depths. Because the Tiamat was developed by the Harwich Haven Authority, it was expected that the Tiamat would perform optimally in areas with strong currents and cohesive sediment at moderate depths. In order to evaluate the performance of the Tiamat, two other dredging techniques - WID and UWP - were tested alongside the Tiamat in these areas.

The results of the pilots and monitoring indicated that the boundary conditions for the Tiamat are primarily influenced by the depth, currents, and sediment characteristics. The depth is limited by the length of the discharge pipe. The Tiamat has the highest production rate in cohesive sediments, as production rates tend to be lower in coarser sand sediments due to their higher tendency to settle. For non-cohesive sediments, a highly energetic river with strong currents is necessary to achieve a certain sediment transport distance.

In order to estimate the performance of the Tiamat, the dredging technique is compared with the WID and UWP. Different parameters such as turbidity, sediment transport, development of the top sediment layer, depth limitations, the production rate in different grain sizes, fuel consumption and costs are compared and discussed.

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 feasibility of installing a suction system, which consists of a pump and pipeline for transporting sediment from the sediment trap to the reallocation site to complement the water injection dredging (WID) method is accessed in this thesis. The combination of a suction system and a water injection dredger is called central suction-WID system. This thesis analyses the sediment return volume, necessary pump power, greenhouse gases production and necessary costs for implementing a central suction-WID system. Three different reallocation sites with different distances for central suction-WID are assessed: Inside of Nieuwe Waterweg, Outside of Nieuwe Waterweg, and Verdiepte Loswal..
Delft3D-Flow numerical model is used for modelling the hydrodynamic and the sediment return volume. The simulation is run for 14 days period in order to simulate spring and neap period. The numerical model result shows that discharging the sediment at the inside of Nieuwe Waterweg leads to the most sediment return, while discharging at the Verdiepte Loswal leads to the least sediment return volume. Increasing the sediment volume or reducing the particle size does not affect the sediment return rate.
The necessary pump power and energy consumption for reallocating the sediment to each location are assessed. The calculation shows that the major contributor to the energy consumption is the friction between the fluid mud and the pipe wall. Reallocating the sediment to the inside of Nieuwe Waterweg consumes the least energy while transporting it to Verdiepte Loswal needs more energy as it is the furthest reallocation site alternative.
Using a WID vessel produces fewer greenhouse gases than hopper dredger as it consumes much less fuel. Costs analysis shows that using a central suction-WID system is more expensive compared to hopper dredger. The costs of using a central suction-WID system increases as the distance between the sediment trap and the reallocation site is higher. However, combining it with another dredging method can be an alternative as it reduces the operational costs.

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.

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.

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.

This Master thesis presents an improved model for the transport of fine suspended sediment (SPM) in the Rhine region of fresh water influence (ROFI) and in the Port of Rotterdam. It is known that the transport of SPM in the Rotterdam harbor depends on marine as well as fluvial processes. SPM transport inside the harbor has been modelled in the past, but these studies did not take into account the dynamic nature of SPM concentrations at sea because they employed constant sediment boundary conditions and did not resolve wind waves. At the same time, numerous model studies of SPM transport in the Southern North Sea have been carried out, but none included the Rotterdam harbor as more than a discharge point. This MSc thesis is the first study to combine a North Sea SPM model with a detailed model of the Port of Rotterdam. By doing so, it incorporates the dynamic nature of sediment concentrations in the North Sea, and its effect on sediment transport in the Rotterdam harbor.

A new suspended sediment model of the Rotterdam harbor was set up with the
Delft3D-WAQ software package and the NSC-Course model grid already in use by Port of Rotterdam. A validated hydrodynamic model was available for this grid schematization, and has been used as model forcing. At the open sea boundaries, the validated ZUNO-DD model for SPM transport on the North Sea was used to compute suspended sediment concentrations, which were then applied as boundary conditions. In addition, a wave buoy assimilation technique was used to include the effect of wind
waves on the resuspension of sediment. A set of initial conditions was created by repeating a single spring-neap cycle with calm, virtually waveless conditions until sediment concentrations reached a dynamic equilibrium. A byproduct of this method was that it created a large sediment availability in the bed, which lead to higher than expected resuspension during storms. To investigate the response of the system to variable forcing conditions, three 14 day periods have been selected from measured environmental conditions of the year 2007, containing different combinations of storms and river discharges.

The model shows positive results, but does need improvement. Principally, the episodic nature of siltation in the harbor basins lining the mouth of the Rotterdam Waterway was reproduced. In line with observations, storms at sea correspond to high SPM concentrations at sea, large influxes through the harbor mouth, and increased siltation rates in the harbor basins. Furthermore, differential advection of the salinity structure and the trapping of SPM in the Rotterdam Waterway was observed. However, erosion was also observed, and harbor basins lining the Rotterdam Waterway showed a strong response to events at sea which contradicts observations. This is attributed to
the wave stress assimilation performed on NSC-Coarse grid which generates large wave stresses inside the harbor and causes unwanted resuspension. Three different forcing scenarios were chosen to highlight the differences between marine and fluvial processes, but a clear distinction could not be made. This is expected to be caused by the erroneous wave shear stresses which obfuscate the effects of different siltation mechanisms. It is recommended that this aspect of the model is improved and that the model is reassessed using measurements.

Current Port of Rotterdam procedure is to define the nautical depth based on the density of a fluid-mud layer, that settles at the bottom of the port. Rheological parameters could be an improved indicator for nautical depth and decrease the frequency and cost of dredging. I investigate the use of reflected seismic waves to derive in situ rheological parameters. I model a simplified port profile to investigate the effects of o_set on the types of seismic reflections acquired. Four models of how the density of the fluid-mud layer varies with depth are proposed. I undertake simple laboratory experiments to measure the effects of consolidation time, density and frequency has on the seismic velocities of the fluid-mud layer. From these laboratory experiments I calculate the shear modulus, bulk modulus, Young's modulus and Poisson's ratio for the fluid-mud layer of varying densities. Reflected seismic-wave velocities prove to be promising in deriving in situ rheological parameters, elastic constants and, potentially, viscosity.