Underwater road tunnels have become critical infrastructure in Norway and, more recently, in the Faroe Islands. Initially excavated to bypass fjords, they later developed to replace ferry services across longer marine straits. The 24 km-long Suðuroy Tunnel will be the longest underwater fixed link in the archipelago and among the longest worldwide. Due to its exceptional length and prolonged poorly lit driving conditions, special safety measures are planned, including two large equal-design caverns functioning as U-turn roundabouts for emergency vehicle evacuation. This study examined the feasibility of excavating these underground widenings within the geological and geotechnical context of the site, primarily composed of sub-horizontal basaltic lava flow cores interbedded with lava breccias and volcaniclastic sandstones. To address knowledge gaps in local lithostratigraphy, rock strength, deformability, and in-situ stress conditions, geological and geomechanical characterisation was carried out using desk studies and field mapping. Preliminary cavern geometries were defined for numerical modelling, with two design solutions emerging: one with a central pillar and one full-span cavern without internal supports.

Continuum-based simulations explored various cavern sizes. Within basaltic flow core units, the stress regime was mostly moderate, with maximum principal stress less than half the uniaxial compressive strength. Tensile stresses reached 80–85% of the rock’s tensile strength, and displacements remained under 4.5 mm, suggesting cavern excavation feasibility. The ratio of horizontal to vertical in-situ stress had a greater influence on stability than rock mass parameters such as Young’s modulus, Poisson’s ratio, or compressive strength. Caverns in both planned positions along the alignment showed similar stress and displacement responses and comparable geomechanical behaviour across the two sites. Simulations involving lava breccia and volcaniclastic sandstone indicated higher instability risks: breccia exhibited potential for spalling and damage accumulation, while sandstone approached the onset of failure. Based on modelling results, two optimal cavern configurations were proposed: (i) a 20-m outer radius with a 4-m central pillar, and (ii) an 18-m radius full-span excavation without support.

This study advances understanding of large-scale underground widenings designed for road roundabouts. It also highlights the need for more site-specific data on stress fields and rock mass strength for the current project, as the models primarily relied on desk-based estimates. Complementary approaches, such as combining continuum modelling with discrete element methods and incorporating structural reinforcement, would provide further insight into brittle failure mechanisms and help evaluate the full feasibility and improvement of such cavern excavations.
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Rising sea levels, combined with land subsidence, have heightened the concerns for safeguarding the coast and waterways of Europe. This effort will require a large amount of strained resources, such as marsh soil, which is becoming increasingly difficult to source. A promising alternative is utilizing the vast amount of dredged sediments extracted by ports each year. Studies have already been conducted on the feasibility of using such a material in dike construction and reinforcements, and guidelines have been developed. Treatment of the material is recommended before application, usually through stockpiling. Although this is widely accepted as a suitable method to treat sediments, the potential for optimizing it has been a subject of few studies. Therefore, focusing on physical ripening, this thesis set out to investigate the evolution of tensile strength and crack formation over time under different stockpile management practices. This research was motivated by the observation that unripened material tends to develop shrinkage cracks when applied in a dike, which creates preferential channels for water to flow through. An important factor influencing the formation of cracks is the material’s tensile strength. Other aspects investigated were the Coefficient of Linear Extensibility (COLE) , which characterizes the shrinkage behavior, and the Atterberg limits. The latter is an important parameter to determine the suitability of a material to be used in dikes. This thesis investigated mechanically de-watered dredged sediments processed in the METHA plant in Hamburg. After processing, the sediments were stockpiled (1,000-2,200 m3) with varying turning rates (none, 2x per year, and 4x per year) and vegetation management (removed before turning or not). Samples were collected over approximately two years, covering ripening times from six months to two and a half years. The results showed that tensile strength increased significantly after one turning event to around 105% of the original material, likely due to aeration improving structural stability. However, subsequent turning events led to a drop in tensile strength. SP7 and SP9 (4x turning per year) exhibited tensile strength 30 % lower than the original material after two years of ripening, suggesting that the repeated mechanical breakdown degraded soil structure. At the end of the investigated period, tensile strength was found to be highest in the control stockpile, where no turning was applied and vegetation was allowed to grow. Higher turning frequency, however, greatly benefited the compactability of the samples. When tensile strength tests were carried out compacting the samples to 95 % of their Proctor density, an increase in tensile strength of 430 % was found in the sample with the highest Proctor density (SP-9). In comparison, SP-4 (control) exhibited an increase of 280 % at 95 % Proctor density. COLE values stabilized after two years to values approximately half of the original material. This indicates reduced shrinkage potential and, therefore, a lower tendency for crack formation in ripened sediments. Crack formation experiments exhibited no consistent pattern across different stockpiling methods and ripening periods. Instead, the most influential factor appeared to be the reduction in shrinkage due to ripening. Crack Intensity Factor (CIF) and average crack width results were consistently lower in the stockpiled material than in the unripened original material. This was likely caused by the reduced shrinkage behavior observed in COLE tests. Finally, the results of the Atterberg limits determination showed that the material is unsuitable for use in the top layer of a dike, but is still appropriate for use as core material. Overall, the findings highlight that limited turning preserves tensile strength, while higher turning frequencies improve compactability. Under field conditions, however, the improved compactability also greatly benefits tensile strength, outweighing the structural instability caused by mechanical breakdown. Ripening also significantly reduces shrinkage potential, thereby decreasing crack formation behavior. These insights suggest a higher turning frequency is the best method for managing dredged sediment, when only tensile strength and crack formation are concerned. ... Read more

Understanding the behaviour of rocks subjected to high temperatures and pressures is essential for a wide range of subsurface applications. This thesis aims to develop an image analysis methodology to measure the porosities and permeabilities of rock samples. These samples were created as part of the doctoral thesis of K.H.A.A. Wolf by compacting rock rubble in a copper tube and subjecting it to various high temperatures and pressures. Despite earlier image analysis on these samples, there was an opportunity for improvement using higher-resolution imaging and more advanced processing techniques. UsingaDSLRcameraand2typesoflight (normal and UV), 33 samples were photographed and then analysed using Adobe Photoshop and ImageJ. Additionally, three samples were selected to be scanned using a µCT scanner. The image processing included the conversion to greyscale, binarisation and the use of the morphological ”open” operation. Porosity was directly measured, while permeability was estimated using a modified Kozeny-Carman equation. The quality of the impregnation of the sample with UV dye differed, yet for 28 out of the 33 samples, imaging with UV light worked better than with normal light. Using temperature data from when the samples were formed, a clear trend emerged showing that the higher the temperature, the lower the porosity and permeability become. This trend was also visible in the work by Wolf (2006) and the values were generally in agreement, except for the samples with extremely low porosities and permeabilities. While CT and image analysis gave similar porosity values, permeability results differed, highlighting the need for simulation-based permeability estimates from CT data. Further research into impregnation techniques is also recommended to enhance future image analysis workflows. ... Read more

In 2005, a pipeline construction was undertaken under the river IJ in Amsterdam. The microtunneling method was used and it consisted of a closed front TBM of 1800mm diameter over a length of 785m in Pleistocene Sand and extremely soft Holocene sediments and anthropogenic sediments. This construction was accompanied by instrumentation that registered the drilling process with force measurements in the main jacks and intermediate jacking stations, strain in the concrete, joint width, tilt of the element and displacement measurements.
All this data was analysed with the focus on the friction development over the entire boring length. The first part of data analysis was to plot and describe the findings of the available parameters, along the total route, that could have an influence on the friction. Next, the microtunnel route was divided into six sections based on changes in soil conditions and in alignment so the analysed parameters (horizontal and vertical deviations, tilt, main jacking force , front force and friction) could be correlated. In order to better understand the results, a Pearson’s correlation analysis was created to identify any statistically relevant correlation between the available parameters. The final analysis was performed to estimate the impact that subsequent pipe segment installations have on the friction over time at a specific location.
The friction development over the entire length at the boring under the river IJ (less than 2kPa, with the exception of the start) was compared with the friction coefficient value described in the NEN 3650 when overcut and lubrication are used for concrete pipes (f =7.5 kPa). The friction coefficient is overestimated during design phase and can be optimized. Also for all six sections, after a standstill, an increase in friction is observed. At locations where correlation between alignment and forces are apparently present, the horizontal deviation is observed as the influencing parameter. This is also confirmed by the Pearson’s correlation analysis results. Regarding the impact that subsequent pipe segment installations have on the friction, the results of this analysis clearly shows a tendency for a decrease in friction when considering soil type and changes in alignment.
Overall, this work indicates the need of a more thorough friction prediction calculation to be included in the design standards. One that includes more influencing parameters other than overcut and lubricant. Such understanding would enable more accurate predictions in future projects, reducing both risks and costs.
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The global rise in demand for critical metals has renewed interest in deep-sea mining of polymetallic nodules on the abyssal plains. Commercial concepts primarily adopt vehicles with tracks to collect these nodules from the soft cohesive seabeds at depths exceeding 4,500 m. These vehicles need to generate sufficient traction and maintain mobility while minimizing seabed disturbance. Predicting their performance, however, remains difficult because of the complex soil behavior and the limited amount of experimental data available. Most existing mobility models are empirical or assume perfectly plastic soils, which neglect strain-dependent softening and remolding.

This thesis develops a generic analytical framework that connects soil stress–strain behavior to track-scale mobility. The model couples a bearing-capacity-based sinkage formulation with a saturated soft-plastic shear–displacement relation. It allows the use of peak and residual shear strengths, as well as the characteristic displacement to peak strength (Kω), directly as input parameters. The framework handles traction and resistance under quasi-static, undrained conditions and applies to both straight-line and turning motion.

The results show that soil sensitivity (the ratio between peak and residual strength) and Kω control the shape of the traction-slip curve. Larger Kω shifts the peak to higher slip and delays remolding, while higher sensitivity steepens the post-peak drop and lowers available traction once the soil is remolded. Increasing the effective contact length improves traction up to a plateau, after which the additional gain becomes small. In heterogeneous (layered) soils, where strength increases with depth, traction increases with grounding pressure but at a decreasing rate. In homogeneous (uniform) soils, traction decreases with added normal load because increased grounding pressure limits shear mobilization before failure.

During turning, most of the track footprint exceeds the characteristic displacement Kω and the response becomes governed by residual strength. Turning is therefore traction-limited and controlled mainly by soil sensitivity, residual strength and geometry. A clear transition in the minimum turning radius is observed when the required thrust exceeds the residual traction level; beyond this point, small-radius turns become infeasible.

The results indicate that mobility can only be predicted reliably when post-peak soil behavior is included. Turning design should be based on remolded soil conditions, while straight-line operation should remain in the pre-peak region to prevent stalling. Design efforts should focus on optimizing contact length, adjusting grouser height to local seabed conditions, and measuring residual strength and sensitivity for the specific site.
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This thesis focuses on 76 pairs of Cone Penetration Tests and boreholes that include Kreftenheye, out of a full database of nearly 200 pairs from TNO - Geological Survey of the Netherlands, generally reaching depths up to 40 meters. The thesis presents this analysis, showing the geological and geotechnical patterns and variations within the Kreftenheye Formation and how the integration of geological and geotechnical knowledge can lead to more effective engineering designs. ... Read more

Frisia Zout B.V. extracts salt from the subsurface by means of solution mining in the north-western part of The Netherlands. The caverns are situated in the Zechstein-II Halite at a depth of around 2.5 km. Because of this depth and the low operating pressure (around 60% of lithostatic pressure) the salt creep within the cavern is high. Once a cavern is at the end of its lifetime it is decommissioned and shut in. During the shut-in period the cavern blanket fluid is removed and replaced with brine and gets time to equalize in pressure and temperature with its surroundings before being permanently abandoned. At the time of abandonment there is still a small pressure deficit (cavern brine at 98% of lithostatic pressure at roof of cavern). At this pressure deficit there is, in theory, still some salt creep because of the difference in pressure between the cavern brine and surrounding salt walls induced by lithostatic pressure. Since the cavern is closed and still creeps, the brine will escape by means of permeation through the surrounding salt walls and roof. At this point an equilibrium is reached between the cavern convergence and the brine permeation around the cavern.
This research aims to get a better understanding of the cavern convergence and permeation processes after abandonment. For this, a cavern convergence- and brine permeation model is made. Next to this the potential surface subsidence due to the migration of brine to more permeable layers is investigated. In the convergence model, the cavern is modelled as a stack of cylinders and a Norton-Hoff power law squeeze model is applied to the cavern. The squeeze model consists of 2 parts, a linear and a nonlinear part. The nonlinear part is most significant during the production phase and in these high-pressure deficits the squeeze model is fitted on the available production data. Recent creep tests on salt samples under lower pressure deficits (Bérest et al., 2019) have confirmed that the linear part becomes the most significant in the low-pressure deficit region and have shown that the linear creep is smaller than the linear component of existing squeeze model used for production.
Next to this a sensitivity analysis was done on the convergence model by varying the input variables of the model. The parameters that have a large uncertainty and have a large impact on the model were the linear part of the squeeze model and the width of a slice. To give a range of outputs of the convergence model a P10, P50 and P90 scenario is created where these are percentiles from the input range of the sensitivity analysis. The outcome of the convergence model at a cavern size of 1Mm3 suggests a yearly cavern convergence of around of 5, 103 and 2313 m3/year for the P10, P50 and P90 cases respectively.
Since there is an equilibrium between the cavern convergence and the brine permeation, the output of the convergence model (convergence rate) can be used as an input for the permeation model (permeation rate). For the permeation model, different paraboloid shapes are fitted on each layer and are filled with brine from the converging cavern. Once all the salt layers are filled in, the brine reaches more permeable layers and can freely flow over a larger area. The permeation model is run with the P10, P50 and P90 convergence model scenarios as an input and predicts that the system fills after 26, 588 and 12,363 years respectively. At this point there could be some subsidence because the brine can freely flow over a larger area in the more permeable layers above the Zechstein. This subsidence is 0.016 mm/year for the P50 case after 588 years. A negligible amount compared to unrelated subsidence processes.
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To conclude the cavern convergence rates (even the P10 at 5m3/year) are high compared to the permeability of salt according to the Darcy flow law (around 17 l/year). This could have multiple explanations. From the cavern perspective, the cavern convergence rates could be lower. This could be because of a threshold pressure for salt creep to occur (van Oosterhout et al., 2022) or because of some inaccuracies in the linear component of the squeeze model. Future research could focus on determining the creep rates of salt under low-pressure deficits. From the permeation perspective, other permeation paths next to permeability could be at play as well. In the cavern there could be permeation via anhydrite alterations or via micro fractures created during the production phase of the cavern. It would be good to look at these permeation processes in the future. Next to this the secondary porosity of the salt remains a question as well. A good understanding of this porosity is needed to assess the storage capacity of the overlying salt layers before the brine enters more permeable zones. ... Read more

Using a field classification, I have assessed the likelihood that a gas field caused a seismic event. I have put the focus on all of the minor gas fields located in the Rotliegend sandstone formation in the Netherlands. These gas fields were divided into five geologically distinctly different regions: the North Holland Platform (NHP), the Groningen Platform (GRO), the Lauwerszee Trough High Pressures (LTHP), the Frisian Platform (FP) and the Lauwerszee Trough (LT). I have investigated which reservoir factors are most influential in deciding whether or not seismicity occurs. The stress ratio has proven to be the most critical parameter. Then, for the stress ratio, I have computed the stress ratio range for each region at which failure will occur. Above the stress ratio, seismic activity will occur, and below the stress ratio, no seismic activity will occur. To answer the research question "Can the reservoir properties of small gas fields in the Netherlands predict the occurrence of seismicity?", I have taken the following steps.
First, I have examined the probability of all small Dutch gas fields being responsible for a seismic event. Based on the distance between the gas field and the nearest event, as well as the presence of other fields in the surrounding area, I have derived a classification for the likelihood that the field was associated with induced seismicity. Second, I have run a sensitivity analysis to identify which parameter was most significant. I have accomplished this by implementing a semi-analytical model that computed and depicted depletion-induced stresses and fault slip along an inclined fault. The model calculated the depletion pressure at which seismic slip starts to occur, here called the onset pressure, based on reservoir data and fault characteristics. The reservoir data contains the compaction coefficient, critical slip weakening distance, dip angle, dynamic friction coefficient, initial reservoir pressure, Poisson's ratio, porosity, reservoir depth, reservoir thickness, shear modulus, static friction coefficient and stress ratio while the fault characteristics included the absolute fault offset and whether the fault is bounding or not.
Afterwards, I have plotted the onset pressure versus the relative fault offset and assessed the sensitivity of the onset pressure whilst changing input parameter settings, namely the critical slip weakening distance, dip angle, dynamic friction coefficient, initial reservoir pressure, Poisson's ratio, porosity, reservoir thickness, shear modulus, static friction and stress ratio. The most critical parameter has turned out to be the stress ratio. I have examined the stress ratio ranges for each field in order to assess whether this parameter could predict the occurrence of seismicity for an entire region. Some fields that do not suit the optimal regional stress ratio have been considered anomalies and investigated further. The main explanations for the anomalies have been geological complexity, assumed synthetic fault offsets, over- or underestimated offsets, unregistered seismic events and substantial overpressure.
The answer to the research question is, yes, it is possible to predict whether seismicity will occur in a small Dutch gas field located in the Rotliegend formation based on reservoir data and fault characteristics. A regional stress ratio has been determined for each of the five regions. The regional stress ratio is 0.51 for NHP, 0.58 for Groningen, 0.69 for LTHP, 0.46 and 0.47 for FP and 0.50 and 0.56 for LT. Salt layers have most likely contributed to higher regional stress ratios for GRO, LT and LTHP. ... Read more

The dolmens erected in the province of Drenthe between 3350-2700 BC are the most ancient monuments of the Netherlands. They consist of a long assemblage of rocks capped with boulders which served as burial chambers for the Funnel Beaker population. Despite their robust look, dolmens are vulnerable. For example, one of the caprocks of dolmen D14 fell off in 2019, once again. The method currently used to repair megaliths is not optimal: a crane is mobilized and the rocks are repositioned using a trial and error strategy. The reconstruction scenario should be selected and fine-tuned digitally beforehand. Moreover, the structural stability of the new assemblage of rocks should also be checked numerically. This necessitates a digital model of all the rocks that have to be rearranged. Not only the visible part of these rocks has to be digitized. The buried parts of the support rocks have to be modelled too as these rocks might have to be displaced and tilted to obtain a more compact and interlocked structure. Since dolmens occupy a prominent position in the Dutch heritage, only non-destructive see-through techniques have to be used for imaging the hidden contours of the bearing rocks. In addition, the bearing stones have complex geometries and are not isolated, which increases the complexity of the problem.

Two suitable geophysical methods are the Ground Penetrating Radar (GPR) and seismic techniques with a focus on reflection measurements. For the GPR specifically, we choose a Common Offset Survey, which can map reflections from the subsurface. For the seismic techniques, we choose a line array measurement, among others. We use the GPR to estimate the buried rock contour of the keystone Sl2 of megalith D14, which is a bearing stone formerly supporting capstone D9. We perform several reflection tests on various rocks unrelated to D14 using different seismic sources and receivers to estimate the reflection depths. We follow a proposed approach for both methods.

To evaluate the GPR data from the field, we assume a simplified GPR with zero-dimensional antennas (GPR point model). Subsequently, we develop two mathematical models (GPR point-to-GEO and GEO-to-GPR point model), based on this conceptual model in order to I) calculate the (buried) rock surfaces from field data and II) model field data from estimated buried rock contours.

We first perform the Common Offset Survey on a non-buried boulder on the campus of the TU Delft to evaluate the accuracy of the developed GPR point-to-GEO model and to optimise the second survey on keystone Sl2. We first perform the seismic reflection measurements on several rock samples to determine the best seismic source. Finally, we perform a line array measurement on a cylindrical basalt column using 300 kHz transducers.

We calculate rock contour coordinates from the GPR data and these show a reasonable fit with the contour of the TU Delft boulder, with an accuracy of 5-10 cm. For the keystone Sl2, the maximum burial depth is determined to be 80 cm at the southern side. The bottom of the keystone is sloping downward starting from ground level at the northern side. The southern, eastern and western rock faces are steep, almost vertical, which is confirmed by historic photographs. However, the calculated (buried) rock surface coordinates consist of an incoherent set of coordinates with locally a lack of data or blind-spots. Estimating a coherent buried rock contour, therefore, requires shortcuts and a decrease of accuracy is to be expected especially for rock surfaces near blind-spots in the GPR data. Furthermore, the identification of relevant reflection surfaces is rather subjective and combined with blind spots in the acquired GPR data, this can lead to wrongful interpretations of the buried rock contour.

The seismic reflection measurements we perform give clear reflections for the 300 kHz transducers on rocks of limited size with simple geometries. However, the transducers should first be applied on rocks with increasingly more complex geometries before being applied in the field. The accuracy in the order of 1 cm can be considered promising, but its applicability for complex geometries and reflection depths larger than 0.5 m remains unknown. ... Read more

Undiscovered underground cavities might exist in the subsurface. A catastrophic ground failure event follows when such a cavity starts to migrate upwards and finally intersects with the surface, resulting in a sinkhole. Catastrophic collapse events are usually preceded by precursory subsidence. An upward migrating cavity causes the development of a (subsidence) trough at the surface. The trough deepens as the cavity nears the surface, changing its surface expression. With the technique called InSAR, displacements over a large area can be measured. Literature shows that precursory subsidence is measurable using InSAR. However, automatically detecting impending sinkholes from InSAR displacements has not yet been researched in depth. This study shows that the developed novel arc-based temporal strategy can early detect an impending sinkhole. The kinematic model is adequate to model the surface expression of an impending sinkhole. The results are used to implement an artificial sinkhole based on the kinematic model into a subset to test the developed strategies. The first strategy was based on spatio-temporal characteristics of a sinkhole. This strategy can locate the subsiding area and indicate a surface expression size range. However, during this study, a second strategy was developed to identify anomalous behavior quicker and more reliable than the spatio-temporal strategy. The second strategy is arc-based and marks point measurements behaving anomalously. The result demonstrates a potential automated early warning system based on the InSAR displacement time series. The developed strategies harbor the potential of monitoring for impending sinkholes on a large scale. This study is anticipated to be a starting point for more development in early warning systems for impending sinkholes. Future research could entail verifying the strategies in regions with collapsed sinkholes. ... Read more

The main reason for this research is the possibility of landslides that could trigger a tsunami together with general interest from the oil and gas industry. The goal of this thesis is to find out what the geotechnical properties are of the 7 different locations at the eastern flank of the Rockall bank which is located to the west of Ireland and to the south of Iceland in the Atlantic Ocean. The possible effects of these properties on slope stability are then discussed. This will be done by geotechnically testing the sediments in a laboratory. All standards used during testing can be seen in chapter 3.1.1. The gravity cores used for this research were found to contain parts of sediment that were quite intact together with other more disturbed parts of sediment. The sediments that were found could be classified as silty SAND, clayey SILTS and silty CLAYS which are calcareous to very higly calcareous,from medium to very high plasticity, low to medium-organic and have extremely low to very low undrained shear strengths. Grain size distribtions were found to be gap-graded and well graded and the the sediments were found to be inactive to normal soil based on the Atterberg limits.Geotechnical properties such as gravimetric water contents are found to range from 0.20 to 1.18, the volumetric water contents range from 0.50 to 0.80, a liquidity index from 0 to 3, specific gravities from 2.72 to 2.79, void ratios from 1 to 3, bulk volumetric weights from 14 kN/m3 to 18 kN/m3, dry volumetric weights from 7 kN/m3 to 13 kN/m3, clay contents from 10% to 60%, a silt content of 15% to 60%, a sand content from 8% to 70%, calcite contents from 17.3% to 57.4%, organic matter contents from 2.6% to 9.0%, liquid limits from 0.40 to 0.82 and plastic limits from 0.23 to 0.49. The undrained shear strength for the original and remoulded sediments from the UU DS tests is found to range from 2 kPa to 8 kPa and from 0 kPa to 4 kPa. The undrained shear strengths from original and remoulded sediments from the fall cone test range from 4 kPa to 33 kPa and from 0 kPa to 4 kPa. The undrained shear strengths from the original pocket vane tests range from 5 kPa to 22 kPa. The sensitivities of the sediments measured by the fall cone tests are found to range from 2 to 28 and the sensitivities obtained by direct shear testing are found to range from 0.5 to 4.Based on these undrained shear strengths a failure mechanism similar to that of a direct shear test is found to be more likely on the undisturbed sediments and a failure mechanism like that of a fall cone test is found to be more likely for the remoulded sediments. The non-phyllosilicate minerals that are present are Smectite, Illite, Muscovite, Chlorite and Kaolinite. The phyllosilicate minerals that are present are Quartz, Alkali feldspar, Plagioclase, Calcite, Ankerite, Siderite, Anatase, Rutile, Hematite, Pyrite, Halite and Apatite. This mineral composition can be logically explained by their possible weathering paths and indicates that the possible parent material is Monzogranite type 2 also called Muscovite-metagranite. Magnetic particles are found to be present in all sediments in small amounts that are not quantified. Similar sediments are found to be present from the research of ( Georgiopoulou, Krastel et al., 2019). This confirms the presence of turbidty deposits. These turbidity deposits are indicated to be present at all sites based on the fininng-upward sequences found. Also the presence of lighter interglacial and darker glacial sediments is found. It was also found that the likley reasons for slope instability on the eastern side of the Rockall Bank are the much higher water contents and clay contents of the sediments present compared to the sediments found on eastern side of the Rockall through.The risk of liquefaction upon distrubance is found at sites 1736, 1672, 1988, 1959 and 1604. No risk of liquefaction upon disturbance is found at site 688. The organic matter content is considered to not have an effect on strenght parameters of the sediments present whereas an increase in the amount of foraminifera shells could increase stability of the sediments. Only differential compaction is not found to be a probable factor in lanslide initiation. A long term instability could arise from weathering of Smectite minerals. Erosion could cause slope instability due to sediments with widely varying grain size distributions. The high water content sediments that are present are prone to liquefaction due a disturbance possibly from seismic activity. It is recommended that in future studies a quantification of the marine shell fraction is made. Also a microscope spectrometry is recommended to be done on the sand fraction together with an X-ray diffraction on the <63µm fraction. The most important recommendation is to do a slope stability analysis on the RBSC using the geotechnical properties presented in this thesis. ... Read more

In a bored railway tunnel project in the Middle-East, difficulties in terms of ovalization, water leakages and settlement of several lining rings located in a fault zone were observed at the end of the construction stage. The present research attempted to find the cause for this lining behaviour. The determination of critical loading conditions, the application of the longitudinal beam model and the analytical and numerical modelling (in Plaxis) of a monolith tunnel lining in abrupt ground property transition were analyzed. Thereby, the global lining stiffness reduction due to joints was also considered. The literature review led to the following expected factors that caused difficulties in the Middle-East case: the squeezing and submerged ground conditions, the rock mass disturbance and the improper backfilling of the rings. Additionally, the ring stiffness reduction due to joints was an essential factor for lining behaviour. The geotechnical conditions, the lining design and the observed difficulties in the case were defined in the next section. Critical missing information, such as geotechnical properties of the fault zone material and limited monitoring data, led to essential assumptions. The settlements were expected to be caused by rock mass disturbance and improper backfilling. These altered the water flow during and after the boring operations and led to lowering of the groundwater level and increase of effective stresses. The water leakages were caused by ring ovalization in the soft fault zone, leading to opening of joints. The analysis for this research was divided in 2D transversal, 2D longitudinal and 3D modelling of the lining in and around the fault zone. The 3D model was seen as the integral model, which took into account the transversal and longitudinal behaviour of the lining. However, most of the behaviour of the lining was analyzed by carrying out parametric analysis for both directions in 2D. Moreover, the 2D models were used to validate the results of the 3D model to identify the influence of the third dimension. The assessment of the results from these analyses led to the following conclusions. The behaviour of the tunnel lining in small width fault zones was governed by the transversal action. The ovalization was mainly influenced by the ground stiffness, the vertical to horizontal stress ratio, the backfilling stiffness and the ring stiffness. Using Erdmann's analytical solution, the approximate lining forces can be determined. However, this overestimated the ground pressures acting on the lining, especially in cases where vertical to horizontal stress ratios were not equal to 0.5. This was because the 2D transversal behaviour did not take into account the longitudinal arching effect, which depended mostly on the stiffness ratio between ground types. The final conclusion was that the global reduction of lining stiffness due to the joints led to a discrepancy with regard to the distribution of the longitudinal displacements. A complementary analysis using a numerical model taking into account the joint structure and discontinuous behaviour between rings would probably allow a better prediction of longitudinal displacements. ... Read more

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. ... Read more

Dams and reservoirs pose safety concerns to society worldwide. In case of a disaster, the water impounded in the reservoir escapes and destroys everything in its path. Reasons for failure range from geology, hydrology and seismicity, to design problems, lack of maintenance and poor field investigation. Prior cases show that various dams gave away mainly due to geological causes, so there is a particular interest to see how the local terrain features could influence the longevity of the structure. Three historical case studies are discussed in order to emphasize the impact of geology regarding dam failure. The Saint Francis Dam is a prime example of poor site investigation, where the lack of knowledge on the foundation rock led to the rupture of the gravity dam. The Malpasset Dam gave away predominantly due to underestimated effects of the uplift, nevertheless, the geologists were unaware of an active fault system and the mechanical properties of the rock mass. The Baldwin Hills Reservoir comes with a more thorough site investigation, yet still, due to earth movements, the water from the reservoir infiltrated through the embankment. Therefore, geological features at the site need to be included in the design options of the dam in order to ensure a safe, feasible and economical project. With respect to the way we build nowadays, engineers have learnt important lessons from past experiences, however, issues such as ageing of the structures and the unpredictability of geology and weather, could still influence the safety of modern dams. ... Read more

The interaction between fractures and the associated effects are studied in fields like geothermal engineering, seismology, volcanology and geo-engineering. Fractures can massively influence the permeability and porosity in a rock formation, reducing resistance to flow. However, to improve permeability, multiple fractures must connect to each other. Therefore, it is important to understand the effects of a stress field under varying orientations and how it influences new and existing fractures. Brazilian disc tests were filmed and performed on 18 Indiana limestone samples, after which 13 samples were fractured a second time under orientations varying from 20° to 90°. Afterwards, video footage of the tests was used to study fracture propagation and fracture roughness. Analysis of the results showed that four distinct types of fracture behaviour occurred. Each type was generally displayed between certain angles. Case 1, under 30° shows reactivation of the original fracture. Case 2, between 30 and 45°, shows largely reactivation of the primary fracture but new secondary fractures towards the ends of the sample. Case 3, between 45 and 60°, shows the primary fracture closing and formation of secondary fractures near the centre of the disk. Case 4, from 60° onwards, shows the primary fracture close completely while a new fracture forms perpendicular and independent of the first. The results imply that initiating a stress field in a certain orientation has differing consequences. A stress field more parallel towards the original fracture causes reactivation of the fracture, without much impact on the permeability. However, a stress field initiated perpendicular to the primary fracture causes a new fracture to form, independent of and straight through the primary fracture. This is likely to increase permeability and therefore reduce resistance to flow. ... Read more

Earthquakes in the past few decades has questioned the safety of people and infrastructure in Groningen region and its surroundings areas. The excessive gas extraction from the subsurface has led to human-induced earthquakes in this region. Liquefaction is a phenomenon that occurs as a result of earthquakes, reducing the soil shear strength to zero and the soil in turn behaving like a liquid. It has been observed in other parts of the world in case of natural and human-induced earthquakes alike. Thus, it is necessary to identify the liquefaction prone regions and taking steps towards creating better designs, equipped to handle earthquake loads along with precautionary measures, to save existing building and infrastructure. In order to do so, it is important to examine the existing the methods, various parameters and factors that influence the liquefaction potential analysis. In this project, the different factors that could influence Liquefaction Potential Analysis are studied based on the existing CPT-based correlations between Fines Content (FC) and Soil Behavior Index(IC). The previously proposed correlation by Boulanger and Idriss (2014) is examined for Groningen Soils to evaluate if it needs any modifications. Depth of the sample, Distance between CPT and borehole, Grain Size Distribution and Geology of the sample are main factors considered for the study. Each of these factors are analysed by collecting laboratory samples of Grain size analysis test from Groningen region. The strength of the correlation between FC and IC is evaluated based on the factors. This study would be beneficial for geo-technical software developers, construction and design engineers who highly depend on correlations and it gives insight of how different the onsite scenario can be from the predicted values using correlations. It contributes to the future research on creating a data base of the all samples in the Netherlands, to indicate high risk regions. It also helps in answering if IC is a good parameter to consider while evaluating liquefaction potential for Groningen Soils. ... Read more

Lagoons are connected to the sea by the presence of openings along their barriers. These openings, also known as tidal inlets, can either be natural or man-made and they highly determine the hydrodynamics within the lagoon system. Tidal inlet systems are found worldwide, and many of them are difficult to be understood due to their complex processes and lack of data. One of these systems is Lake Bardawil. Lake Bardawil, is located at the North coast of the Sinai Peninsula in Egypt and its ecological value is of great importance. Its existence mainly depends on the presence of three inlets which connect the lagoon with the Mediterranean Sea, called Boughaz 1, Boughaz 2 and Zaranik inlet. Boughaz 1 is located in the western side of the lake while Boughaz 2 and Zaranik are in the eastern side.
One of the recent researches that is carried out by the Dredging, Environmental and Marine Engineering (DEME), The Weather Makers (TWM) and Lanters (2016), studied how the ecosystem and the fish population of Lake Bardawil can be restored by new hydraulic interventions. This thesis is an extension of the aforementioned work, but current focus is put on the determination of an innovative design and associated methodology which is based on natural design elements and can improve the functionality of Boughaz 1 inlet.
Boughaz 1 was constructed in 1955 to allow the water exchange between the sea and the lagoon. Over the passing years, it has been subjected to a reduced tidal prism resulting in poor water quality in the lagoon, limited fish migration from the sea and sedimentation causes the need for dredging maintenance works. This led to the construction of breakwaters in 1985 until 1995 for the stabilization of the inlet and for the protection of the fish population in the lagoon. Although, the dredging works and constructed breakwaters minimized the abrupt sedimentation through the inlet and improved its stability in short term, the natural behavior of the system is gradually changed which worsen these conditions in longer term. For that reason, a design methodology is carried out to understand and improve the functionality of the Boughaz 1 inlet. The design methodology is based on the most important natural design elements, namely inlet cross sectional area, approach channel and inlet nourishment. Numerical models (Delft3D and Delft3D FM) are used to assess the influence of the different designs on the functionality of the system. A hydrodynamic analysis is carried out for each design element to define the final combined design of the initial phase of this design process. This final design is examined under hydrodynamics and the initial deposition and erosion patters. It is concluded that the functionality of the Boughaz 1 inlet can be optimized with the adapted design methodology. The tidal prism and flow velocities have been increased while the aim to mimic nature is validated with the initial deposition and erosion patterns.
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An investigation in the possibility to integrate fleet selection (through FPC) in the mine design process, allowing for the analysis of various potential haul road scenarios and from there being able to make a decision on an optimal fleet selection. ... Read more

The purpose of this thesis is to aid in the development of vertical cutting mining as a mining method. In order to do so, the technical feasibility and viability, and environmental benefit of vertical cutting as a complementary mining method were investigated. The investigation was performed for the case of the Victor Diamond mine in northern Ontario, Canada, where open pit mining ends by the end of 2018 or beginning of 2019.

Vertical cutting has been used for several decades for the construction of water retention walls in the civil engineering industry. By placing the vertical cutter system directly on top of an ore target and cutting straight, vertical trenches up to a maximum depth of 150 m, it is intended to cross over to the mining industry. Extraction with vertical cutting can occur according four extraction scenarios. Three of the scenarios are land-based, the fourth assumes flooding of the mine, and has not been considered for the Victor project.

Checkerboard mining is the base case extraction scenario with an extraction rate of approximately 30%. The long trenching scenario would increase the recovery with an additional 15% but induces a high risk of instability in the existing pit walls and the kimberlite in between the trenches. Application of backfill is the third scenario and achieves a recovery of 98%. Backfilling of the trenches requires the movement of significant volumes of additional rock as well as induces time delays due to the curing time of the backfill.

Financial evaluation of the vertical cutting scenarios shows a high dependency of the project value on a decreasing cutting performance. Cumulative cash flow analysis and NPV suggest that extending the mine life at the Victor Diamond mine with vertical cutting is favourable. Even in the case of increased rock strengths, as expected in the deeper parts of the Victor pipes, vertical cutting has a positive net present project value. Long trenching, which is considered to be of high risk for pit stability has only marginally greater project value than the base case.

The development of alternative mining solutions also aims to reduce the impact of the mining operations on the surrounding environment. Vertical cutting combines multiple mining processes into one operating piece of equipment. It reduces the GHG emissions, improves the safety of extraction process and is expected to increase the support from stakeholders. Extending operational life using conventional methods would require large expansion of the mine involving the increase of the operational fleet, pumping capacity and land usage. The application of vertical cutting has the ability to prevent the negative impact of enlarged open pit mining while maintaining the benefit of continued production. ... Read more