1 

Discrete Element Modelling: The influence of High Hydrostatic Pressure on the Cutting Processes of Hard Rock
Seafloor Massive Sulfide (SMS) contains high levels of metals such as copper and gold. Water depths of 2000 up to 3000 meter make mining of SMS a challenge. Despite this, mining industry encourages research into feasible extraction methods of SMS, pushed by the high metal prices nowadays. This research focuses on the influence of hydrostatic pressure on the cutting process of hard rock. A 2D numerical model of the cutting process is created using discrete element modelling (DEM). The software package Particle Flow Code 2D (PFC2D) from Itasca Consulting Group is used. The rock material creation in PFC2D consists of reproducing numerically the physical UCS, biaxial and Brazilian tests executed on the benchmark material. SMS is the rock of interest for deepsea mining, nevertheless Langmeil Sandstone is chosen as benchmark material. This consideration is taken because SMS samples are rare and no strength test results obtained on SMS samples are published. In addition the high heterogeneity of SMS makes their numerical modelling difficult. It was not possible to come up with a singular numerical rock sample matching the mechanical properties of the Sandstone for a large range of confining pressures (0 to 40 MPa). Therefore two samples were created: the first sample is valid for unconfined tests, the second sample is valid for confining pressures between 20 and 40 MPa. It appeared that the material unconfined compressive strength and elastic constants are independent of the particle size. The transition point from brittle to ductile failure is simulated successfully for the second rock sample. Three different cutting scenarios are studied: cutting of dry rock without hydrostatic pressure, cutting of dry rock under hydrostatic pressure and cutting of saturated rock. The boundary particle method is an algorithm capable of simulating hydrostatic pressure. This method applies a force similar to the hydrostatic load on each boundary particle of the sample. The method simulates the transition between brittle and ductile rock cutting successfully, by increasing the effective stress, while fluid and pore pressures are absent. The transition from brittle to ductile cutting is reached at a hydrostatic load of 20 MPa for the Langmeil sandstone. The cutting force (450 kN) obtained by the numerical model for the unconfined calibrated rock is compared with existing semiempirical models. Goktan’s (1995) model (300 kN) provides the best match , Evans’ (1961) model (75 kN) underestimates the required cutting force. The horizontal cutting force increases with increasing hydrostatic pressure. The increase of hydrostatic load is mainly transferred into an extra load on the cutting tool in horizontal direction. The specific energy calculated from the cutting force obtained by the numerical model (4.9 MJ/m3) is in good accordance to the values for sandstone found in literature (5.5 MJ/m3). The influence of the tool shape, the cutting velocity and depth of cut on the cutting process of dry rock is modelled. The chisel pick tool shows to be more efficient than the pick point tool for shallow water depths. The difference in efficiency between these tools becomes smaller with increasing hydrostatic pressures. Measurement circles in PFC2D are able to register porosity changes during the cutting process. These measurements are used to estimate pressure differences in the crushed zone. This method provides a good qualitative insight in the development of pore pressures during the cutting process. Useful quantitative values were not obtained. The measurement circle method indicates that cavitation will not occur for high hydrostatic loads such as 20 or 30 MPa, which implies that the required cutting force will continuously increase for an increasing cutting velocity. The main recommendations are introducing the Biot poroelastic equations and heterogeneity into a 3D discrete element model. Quantitative estimations for the specific energy and pore pressures during the cutting processes should be obtained. Execution of laboratory tests of rock cutting under varying hydrostatic pressures is of most importance to check the performance of the numerical rock cutting models.

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2 

Reservoir Geology and Modelling of Carboniferous Coalbearing marginal Marine and Fluvial Deposits of Eastern Kentucky and Implications for Hydrocarbon Exploration and Development
Successful search and exploitation for hydrocarbons form the subsurface demands the acquisition of a thorough understanding of the basin’s geology, attainable by analyzing critically the stratigraphic framework and facies architecture of analog outcrops and mature fields with a dense network of wells. In this study Petrel was used to construct such a conceptual facies model for the Breathitt Group in the Central Appalachian Basin, with the aim of investigating the pattern of depositional environments and how they influenced the vertical and lateral distribution of facies in the foreland basin. The model provides excellent guidelines to the distribution of depositional energies in analogous subsurface progradational coastalplain and fluvialdeltaic reservoir sequences. The study area is an appropriate analogue used by many oil and gas companies to understand and solve stratigraphic problems in subsurface coal mines and coalbearing hydrocarbon reservoirs. Cored borehole data from 12 quadrangles in Eastern Kentucky was loaded into Petrel to generate vertical sedimentological logs. The logs were correlated using extensive coal seams and marine flooding surfaces to obtain stratigraphic columns of the strike and dip sections of the basin. 3D stratigraphic surfaces and isochore maps, embedded with piecharts, were generated to quantify the proportions of lithofacies along every well that wholly penetrates any given isochore, including the determination, prediction and interpretation of lateral and vertical distribution of facies, depositional energies and paleoenvironments. Basic principles of sequence stratigraphy were applied to explain the role and interactions of tectonics, subsidence and eustasy in the evolution of the delta system in the foreland basin. Results show that differential subsidence, including active tectonics (orogenesis) and quiescence gave rise to two broad depositional systems. The upper system, which is predominantly composed of immature sediments, was deposited by braided and meandering streams from the tectonically active thrustfront in the southeast toward the northwest in a fluvialdeltaic environment, whilst the lower system is composed of mature sediments whose deposition was mainly influenced by waves/storms and tides from the sea in the northwest that frequently transgressed the subsiding basin during the long periods of tectonic quiescence. The stratigraphy further shows a tendency to increase slope inclination and a series of anticlinal and synclinal structures, mainly in the upper system, which may provide reservoir traps or control the dynamics of fluid flow in the basin. The analysis shows that the fluvialdeltaic system has better reservoirs with a good vertical and lateral connectivity than reservoirs in the lower coastalplain system, where vertical connectivity and permeability, is hindered by the thin laterally extensive shales between units. Nevertheless, this system could provide a good source region for the generation of hydrocarbons, due to its high content of organic matter and depth of burial, offering optimal pressures and kitchen (enough heat energy) for the generation of hydrocarbons. Facies analysis using isochores and piecharts may be applied during both frontier exploration and exploitation phase to provide a simple and quick method of reserves estimates based on the predicted geometrical dimensions of reservoirs and non reservoirs. The method yields important petrophyical parameters that can assist reservoir engineers to design simulation models required for optimal well spacing and positioning, well numbers and better enhanced oil recovery (EOR) methods.

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3 

Source Decomposition and Receiver Composition for ElectroKinetic Measurements
At interfaces between porous media acoustic energy can be converted into electromagnetic energy or vice versa by the electrokinetic effect. Operators exist describing this conversion, however these act on (oneway) upgoing and downgoing waves, while in nature only the total (twoway) wavefield exists. In this thesis mathematical formulations are developed for the source decomposition operator, describing the relation between the twoway source wavefield and the oneway downgoing wavefield, and for the receiver composition operator, describing the relation between the oneway upgoing wavefield and the twoway wavefield at the receivers. The behavior of these operators is visualized by numerical modeling.

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4 

Design of a Heating System with Geothermal Energy and CO2 Capture
Heating constitutes about 40% of the final energy consumption at TU Delft. In the present, the district heating system in campus obtains its energy from the combustion of natural gas in a combined heat and power plant. Although this plant produces heat and electricity with an efficiency over 80%, the dependance on a fossil fuel presents an opportunity for improvement by introducing a renewable energy source. In May 2013, the drilling for a geothermal plant in campus was approved.
The present heating system operates at high temperature (HT  130°C) with 3way valves. In the new heating system, a geothermal plant will provide part of the energy and some buildings will undergo renovations to work at medium temperature (MT  70°C); they will be connected in series after HT buildings, constituting a cascade system.
In this study, steady state simulations of the heating system are performed using CycleTempo. The results are then used for an exergy analysis of different configurations in the system.
The analysis of the ongoing transition in the present heating system from a 3way to a 2way valve configuration reveals that up to 180 kW of electricity from the grid used for pumping can be saved and replaced by heat produced locally at a higher efficiency, representing up to 36% in primary energy savings. Within the system boundaries, the exergy efficiency does not improve with the transition, but a reduction in the return temperature from 7580°C to 5075°C allows for geothermal energy utilisation.
For the new heating system, three configurations of the network are devised: a parallel network at high temperature, a cascade system renovating small buildings and a cascade system renovating large buildings. The exergy analysis reveals that the best option is to renovate the small buildings in campus. In this way, geothermal energy can provide 19% to 50% of the heat demand.
The suggested configuration for the new system can operate with an exergy efficiency 14% higher than the present system, reducing the primary energy consumption and the associated emission of CO2 by 47%.
Carbon capture and sequestration can decrease the emission of CO2 further by 51%. However, the capture process by means of the dominant technology, amine absorption, requires additional consumption of fossil fuels, which worsens the scarcity of these resources.

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5 

Anchor Chain Cutting Through a Rock Cover
An everincreasing number of cables and pipelines are being laid on the bottom of lakes, channels, rivers, seas, and oceans. Various hazards threaten these pipelines and cables, which in case of occurrence can cause (severe) environmental and/or economic damage. Pipelines and cables can be protected against these attacks by dumping protective rock layers over the pipelines or cables.
The main hazard concerning this research is the attack of a dragging anchor preceded by the cutting process of the anchor chain while dragged over / through the rock cover.
For dragging anchors the effect of any lifting force is detrimental to its holding capacity. A good design of the rock cover can reduce the cutting of an anchor chain in the rock cover, resulting in an earlier lifting of the anchor.
No generally applicable design tool exists for dimensioning these rock covers and especially in relation to anchor chains. Therefore the objective is set to find and test a theoretically based relation for the interaction between an anchor chain and a protective rock layer.
The simplified solutions for describing the interaction between an anchor chain and clay are used as a basis for the interaction between the chain and rocks. The interaction forces are described as uniformly distributed forces in parallel and lateral directions of the anchor chain.
There are several types of rock covers feasible but the loosely dumped rock cover on top of the existing seabed is chosen for this research.
The bearing capacity of the rock berm is modelled as the bearing capacity of a strip footing on a shallow foundation. Since the bearing capacity equations do not provide information of loads in the lateral direction to the strip footing the formulas are adjusted to the research situation.
A theoretical model with dimensionless normalized axis is used. The model describes a failure curve with all possible combinations of parallel and lateral forces applied to the rock berm by the anchor chain and normalised by the bearing capacity of the rock berm. A physical model has been designed to validate the theoretical model.
In the physical model five different anchor chains have been dragged through three different sizes of rock covers with a few different constant anchor holding capacities. The forces on both sides of the rock cover are indirectly measured by the load cells on both sides of the model. The guiding wheels in the model cause significant friction in the model during dragging.
In experiments without the presence of a rock cover a friction factor is determined to quantify the force loss over a guiding wheel. This friction factor lies within a range of 0.10<friction factor<0.16.
It turned out that this friction factor has a major influence on every single data point when plotted in the theoretical model plot. However correlation is found between the data sets acquired by the experiments and the normalized failure curve presented above with the use of a semiarbitrarily determined friction factor for each experiment. The semiarbitrarily friction factor lies within the range specified above and is only changed when structural modifications to the model are made.
The bearing capacity of the rock berm, which is mainly influenced by the effective width of the anchor chain and the internal friction angle of the rocks, only determines the location of the acquired data in the theoretical model plot. Different bearing capacities scale the dataset into the origin. Because of the uncertainty of the exact bearing capacity of the rock cover research on this subject is recommended. With the bearing capacity known the location of the acquired dataset on the theoretical normal plot can be determined.
It is also recommended to do new physical model tests in which the forces on both sides of the rock berm can be directly measured eliminating the effect of friction in guiding wheels.

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6 

Inversion of multitransient EM data from anisotropic media
Forward modelling demonstrates that resistivity anisotropy has a huge effect on MultiTransient ElectroMagnetic step and impulse responses. The earth is never isotropic – even a stack of isotropic layers behaves anisotropically – and there is a great need to ccount for resistivity anisotropy in order to delineate the true target depth and target transverse resistance in ElectroMagnetic surveying. I account for resistivity anisotropy by (a) deriving apparent anisotropy formulae and using them together with apparent resistivities for a fast iterative inversion scheme, and (b) by including anisotropy into a 1D full waveform inversion scheme. Full anisotropic inversions result in much smoother models than isotropic inversions. Sharp resistivity boundaries result in anisotropy anomalies, as horizontal and vertical resistivities are not affected in the same way. Anisotropic inversion results yield a good indication of the present background anisotropy. Carrying out inversions with fixed anisotropies, e.g. determined in a free anisotropic inversion, can improve the result significantly compared with an isotropic inversion.

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7 

Numerical Simulation of Chemical Reaction of InSitu Combustion Using SARA Fraction

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8 

Shear strength of Bremanger sandstone rockf ill at low stress
The Bremanger Sandstone rock fill is used to form a cobble beach, to build an underwater foundation layer of a sea water breaker and to construct a run way for a large crane in construction of Maasvlakte 2 (MV2), the extension of Rotterdam harbor.
The main purpose of this work is to determine in the laboratory the strength of Bremanger rock fills under low stress. Tests are conducted on rock fills with a finer particle size distribution than that used at MV2. Results obtained cannot be directly used in the design of MV2 project. The influence of the testing equipment, for a given ratio of the equipment size to the particle size, of the degree of compaction and of the particle strength on the strength of the Bremanger rock fill are investigated. The effect of the test boundary conditions is researched by conducting tests with a triaxial cell apparatus, medium and small scale shear boxes and a tilt apparatus. The movement of particles was also studied during medium scale shear box testing to get a better insight into this effect.
Emphasis is put on determining the contribution of dilatancy to the shear resistance of the Bremanger sandstone rock fills with respect to the contribution to resistance to rolling of particles. For this purpose, dilatancy is measured during testing and the basic friction angle of the Bremanger rock fill is determined on sandblasted rock discontinuities with a Golder shear box. The basic friction angle controls the resistance to rotation of smooth particles. Test results are fitted using empirical models. The performance of these models at predicting the strength of the tested materials is assessed.

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9 

Geologic origin of arsenic groundwater contamination in Maner block, Bihar, India
Arsenic contamination of the groundwater and as a consequence, of the drinking water, has developed to a major problem for many regions globally during the last decades (Chile, China, United States, Argentina, and Mexico). The issue of Arsenic contamination has already been studied extensively in West Bengal, India and Bangladesh, which are some of the affected areas. The importance of studying arsenic groundwater contamination lies in the fact that it has impacts on human health, which indicate that proper measures need to be taken towards a safe drinking water solution.
Despite the fact that many researchers around the world have tried to determine arsenic release and mobilization mechanisms, it appears that this is a procedure that is controlled by rather regional parameters and therefore, there is no standard mechanism that can be taken for granted. Each region has different geological and stratigraphic characteristics and since arsenic is naturally formed and released in groundwater for most of the contaminated cases, each region needs to be carefully studied separately.
The state of Bihar in India and more specifically the region close to the conjunction of the Ganga and Sone Rivers was chosen as a research location, because, contrary to other affected regions, no geologically related research regarding Arsenic has been carried out there until now.
The initial target of this research project was to build a 3D sedimentary architecture model of the area using PETREL software. This model could later be used in flow modeling. The study was then focused on determining the various depositional environments of fluvial sediments and in finally correlating them with the presence or absence of Arsenic in the groundwater. In addition, this study aims to provide a suggestion regarding the possible source of Arsenic in the groundwater for the region of Maner in Bihar.
There are two basic hypotheses that will be investigated during this research. One is that Arsenic is confined within the Newer Alluvium of the Ganga River (Holocene sediments) and especially within the point bar alluvial depositions. The second is that Arsenic is already present within the sediments and released in the groundwater due to the presence of Iron oxides in Iron rich minerals (biotite and micas in general) or Iron coatings on Quartz and clay grains.
The following methodologies were applied in order to achieve the research purpose. First, literature study of existing research in the area and other Arsenic affected regions was carried out. Then the study area was visited and fieldwork was carried out, which included drilling three approximately 50 m deep boreholes by hand sludging and logging the sediment cores that were obtained as accurately as possible. Hand sludging was used as the drilling technique, even if it is suboptimal for the initial research purpose, because of financial and time constraints. Therefore, it was not possible to obtain undisturbed soil samples while drilling. As a result, core logging, which is an important input for a 3D model, was not always successful.
Then, Ultra Violet Spectrophotometry testing was carried out in order to measure the Arsenic content in soil and Scanning Electron Microscopy and Xray Diffraction in order to determine the mineralogy and chemical composition of the soil samples. In addition, existing measurements of Arsenic levels in drinking water were registered and the coordinates of the handpumps were recorded, using a Global Positioning System device (GARMIN).
The purpose of this research is to combine existing knowledge regarding the source of arsenic and specific sedimentary settings in order to correlate local geological characteristics with the presence or absence of arsenic in the groundwater and to suggest a possible source of arsenic for the region of Maner.
The results support the hypothesis that it is essential to consider the origin of the sediments to localize regions of high arsenic content.

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10 

Borehole Images and Logs: Tools to Constrain the Architecture of a Channelized Slope System, Karoo Basin, South Africa
The SLOPE3 project investigates the depositional architecture of a Permian age, deep water / complex channelized slope system which is of interest to the oil industry as a potential analogue for real oil / gas reservoirs. This study forms a part of the SLOPE3
project and is focused on an integration of cores and wireline logs from six research boreholes, each forming a 1D datasets showing a hierarchy of genetic depositional elements: channels, complexes, complex sets and equivalent hierarchy channel sands, channel margin, levee and overbank deposits. These elements were previously characterized in outcrop by the University of Liverpool in an earlier phase of the SLOPE project. The University
of Liverpool presented their data as a high resolution outcrop map / correlation panel some five kilometre long showing a unit truncated by a 120 m deep slope valley (see Figure frontpage). For SLOPE3 a set of six boreholes were drilled along a line subparallel and about 300 metres behind that outcrop section. The borehole positions had been picked on the basis of the outcrop correlation panel. All six boreholes were fully cored and five
boreholes were logged with GR / Sonic / FMS. The ultimate objective of the project is to provide a set of analoguebased input data for 3D reservoir modelling.
The wireline data of GR, Sonic, and FMS borehole images formed the basis for this MSc thesis and was processed and presented as graphics/logs by making use of GeoFrame software. With this software manually dippicking of planar sedimentary structures was done. With the focus on constraining the 3D architecture of the channelized slope system, bed boundaries as well as the following other dip classes were picked: erosion surfaces, climbing ripples, lowangle crossbedding, synsedimentary faults, and slump folds. By making use of the FMS images and the GR / Sonic log results the following lithofacies associations / genetic sedimentary units were identified in the five logged boreholes: massive sandstone, channel margin, external levee, internal levee, all in a background of shale. All measured sedimentary dip picks were corrected to palaeocurrent / palaeoslope indicators by subtraction of the measured and averaged structural dips. Sedimentary dips were plotted on stereonets for statistical analysis and interpretation in terms of palaeocurrent flow direction / palaeoslope orientation.
This combination of a detailed outcrop data set with a suite of boreholes located on the basis of the outcrop data is a near ideal test set for the quality of geological predictions of a 3D reservoir architecture. The different type of architectural reservoir elements each with their specific lithofacies associations, can be characterized by FMS, Sonic, and GR logs when run in boreholes. However in this thesis it is shown that by doing a prediction
(‘prognosis’) of the distribution of the lithofacies associations and their thicknessencountered by the boreholes based on an extrapolation from the nearby outcrop, it is rather difficult to predict the ‘actual’ geology away from well control. Moreover the value of palaeocurrent and palaeoslope indicators as identified from the FMS images for the prediction the distribution (orientation and the position) of the different genetic bodies, proved to be surprisingly minor. This is a reflection of the large spread / variation in measured palaeocurrent directions (local variation), and the additional scatter of those indicators away from the boreholes (areal variation). This latter aspect is characteristic
for a meandering submarine slope channel complexes. The CD Ridge complex channelized slope system is hence interpreted to be a ‘jigsaw’ to even a ‘labyrinth’ reservoir type. The shaleprone external levee deposits are laterally extensive, thinly bedded sequences have a more layercake architecture. Therefore it is suggested to use deterministic modelling for these layercake parts, where the ‘jigsaw’ parts require a probabilistic modelling approach.
The analysis of borehole images and logs resulted in:
A complete input dataset including:
• Zonations of the genetic bodies for every well.
• A whole bunch of stereonets for 3D analysis.
Both could not be achieved without BHI.
Value of the use of borehole images is the 3D aspect and to distinguish between different thinbedded lithofacies associations.

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11 

Lateral behavior of large diameter offshore monopile foundations for wind turbines
Offshore wind parks promise to become an important source of energy in the near future. To make economic use of offshore wind energy possible, foundation structures with minimum costs, but sufficient stiffness have to be designed. The horizontal loads from wind, waves and currents must be in equilibrium with the reaction of the soil. One foundation concept that has often been realized recently is the monopile. The traditional monopile is an open ended large diameter steel cylindrical pile driven into the soil.
In the offshore energy industry the soil in horizontal pilesoil interaction problems is normally modeled by means of multilinear soil springs, the so called py curves developed by the American Petroleum Institute (API). The py curves of the API are verified for piles with a diameter of up to 2.0 m.
It was expected that for the design of the large diameter monopile foundations the API method would overestimate the horizontal pile displacements:
• For large diameter piles the shearing resistance in the pile tip may play an important role. This effect is not included in the API method.
• Large diameter piles have more shear stresses around and along the pile shaft due to the larger pile surface. This effect is also not included in the API method.
However, the API does not take the interaction between the soil springs into account for the large diameter monopile foundation.
To study on these effects the results of the API method are compared with the results of 3D Finite Element (FE) calculations for both a small diameter foundation pile (D = 1.0 m) and a large diameter monopile foundation (D = 4.3 m). Both piles are embedded 25 m in a homogeneous layer of sand. A representative static horizontal load and bending moment are applied to the pile. For the small diameter foundation pile the results of the 3D FEM should be comparable with the results of the py method.

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12 

Failure of Peat Dikes due to Drought
This research investigates the Wilnis dike failure that occurred in the dry summer of 2003. It is believed that drought played an important role in decreasing the stability of the dike, finally leading to failure. In the reported MSc project the situation during drought is simulated with the help of finite element method programs Plaxis and PlaxFlow in order to get more insight into the conditions that caused the dike to fail.
First a forensic analysis based on pictures taken directly after the breach is presented, followed by information about relevant failure cases. The interpretation of the soil investigation performed by GeoDelft after the failure is reviewed subsequently. The field data (Borings and Cone Penetration Tests) are used to define the stratification of the soil. The laboratory data (Triaxial, Simple Shear and KoCRS tests) are utilised to determine the soil parameters. With this information a finite element model is constructed in Plaxis. The material model used to simulate the different soil types is the Hardening Soil model. In Plaxis and PlaxFlow 3 different calculation phases are defined. The first 2 have as a purpose to simulate the soil history until the start of drought since this is an important aspect in the further behaviour of soil during drought itself. The third one is the simulated drought period. All the groundwater flow related aspects (groundwater head, excess pore pressures etc.) are calculated by PlaxFlow while the related deformation and stability analyses are done by Plaxis.
A parametric study of the groundwater flow by PlaxFlow is performed leading to the conclusion that the upper layer of the soil consisting of Holland peat has to be separated into 2 parts along the middle of the slope of the dike in order to take the different degrees of saturation of the unsaturated soil above the groundwater table, that affect the unsaturated soil weight, into account.
Finally 9 different models are composed with varying strengths and permeabilities in order to take into consideration the effect of these parameters. The groundwater flow results are realistic. However the deformation results show irregular unexplainable patterns which are inconsistent with some of the observed data of the actual failure.
Furthermore the safety factors are calculated for the end of phase 2 (before drought) and phase 3 (after drought). These results are also very inconsistent and should be discarded.

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13 

The Effect of Nonlinear Soil Behavior under Vibrating Loads
Seismic vibrators are used to investigate the structure of the subsurface in the framework of soil and gas exploration, also to locate faults and rupture zones in earthquake investigations. Vibrators introduce seismic waves that propagate through the ground and are received by seismic sensors at some distance from the source. This enables interpretation of the subsoil structure by inverse analysis. To analyze the behavior of the soil below a seismic vibrator, analytical models were developed in the past in which the behavior of the soil is simplified by linear elasticity. This assumption of linear elastic soil model does not describe real soil behaviors. In this research, a seismic vibrator standing on a homogeneous soil is simulated by means of an axisymmetric finite element model with an advanced soil model, i.e. Hardening Soil model with smallstrain stiffness, called HSsmall model in which the nonlinear, irreversible soil behaviors as well as smallstrain stiffness effects below a seismic vibrator are taken into account. The sign and amplitude of displacements of the ground surface in the near field and the far field are observed for a homogeneous sand and homogeneous clay. A comparison between the linear elastic model and the HSsmall model in simulation the soil response is made. The response of the sand and clay under deltapulse load, minimumphasewavelet load, chirp load, and harmonic load with different frequencies (5Hz and 50Hz) and amplitudes (10kN/m2 and 20kN/m2) is simulated and evaluated. The influence of stressstrain dependent soil stiffness and porewater on seismic wave velocities is evaluated by means of seismograms.

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14 

Verification and numerical implementation of a 3D liquefaction model
With the advancement of solution techniques and solving computers, 3D analysis of civil engineering problems has increasingly become more interesting. The multiple spring model is one of the tools to give good solutions to 3D liquefaction analyses. In this model, the deviatoric stress is determined in a finite number of springs distributed over virtual planes in the soil element for which liquefaction analysis is to be undergone. Among the several options for the distribution of the virtual planes in the soil element, it was previously found that an icosahedral distribution results in an isotropic model. For the displacement based analysis which is going to be discussed in this report, the global strains will be decomposed into onedimensional strains in each spring through transformation matrices. Then the Masing rule after several modifications will be used to obtain stress ratio from those transformed strains. The product of the stress ratio and the mean effective stress gives the shear stress in each spring. The global shear stress of the soil mass is calculated from the shear stress in each spring through transformation matrices. The model also uses stressdilatancy relationships to calculate volumetric strain due to dilatancy which enables to calculate the volumetric strain due to consolidation. Expressions for a curve of isotropic compression or swelling help to calculate the mean effective stress. Along with the stress ratio, it is this mean effective stress that will be used to calculate the shear stress in each spring. In this report, it is discovered that the icosahedral distribution of planes results in an isotropic behavior. However, the way the springs are oriented on those plane as described in the original model by Nishimura (2002) will not result in an isotropic behavior. At the end of the report, suggestions will be given to overcome this anisotropy. It will also be seen that the volumetric strain due to dilatancy is overestimated in the model. The source for the overestimation is discovered and will be forwarded for further improvement. Suggestions for the modification of the hysteresis loop when the stress ratio in the past is exceeded will also be given.

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15 

Hypoplasticity Investigated: Parameter Determination and Numerical Simulation
Due to the weak soil deposits in the Netherlands, pile foundations consisting of driven displacement piles are often used to support the superstructure. The influence of pile installation process on the stresses and the soil properties is large. In geotechnical practise the effect of the pile installation and the interaction with neighbouring structures is of special interest. These type of geotechnical problems are commonly investigated with the aid of numerical methods, i.e. the finite element method (FEM). Numerical simulation of the pile installation process requires a constitutive model which is able to describe the soil behaviour, taking into account the continuously changing soil properties.
In the current study the use of the hypoplasticity constitutive model in an Eulerian frame work, offered by the commercial package FEAT, is adopted. Hypoplasticity has emerged in the recent years and is gaining popularity due to its numerous successfull applications. It is an inelastic (dissipative) and incrementally nonlinear constitutive model, which requires neither a yield surface nor a decomposition of strain rate into elastic and plastic portions. It presents a single tensorial equation holding equally for loading and unloading. This research is formulated to gain more knowledge into the experimental determination of the hypoplasticity model parameters, leading to the derivation of a consistent parameter set for Baskarp sand. The hypoplasticity parameters for Baskarp sand are of special interest such that the numerical simulation of the soil behaviour can be compared with the measurements obtained from two model tests of displacement piles installed in a geotechnical centrifuge. The outcome of this thesis will provide an unambiguous procedure to determine the hypoplasticity model parameters. The parameter set derived for Baskarp sand can be used to validate and improve the numerical simulation of the model pile tests performed by Dijkstra et al. (2006). The experimental work starts with the characterisation tests, i.e. grain size distribution, mass density, maximum and minimum void ratios. Next, a series of oedometric and drained triaxial compression tests were carried out on loose and dense samples. In addition image processing techniques are introduced for the determination of the angle of repose.

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16 

Experimental modelling of lateral loads on large diameter monopile foundations in sand
The last years several offshore wind farms have been completed. Such farms typically consist of a few dozen wind turbines. The majority of these wind turbines is founded on monopiles with a diameter of 4–5 m and is designed according to standards that use the py method for lateral loading conditions. However, this py method is not validated for such diameter piles. Fullscale field tests and model pile tests with properly scaled stress conditions subjected to lateral loads are scarce. This Thesis investigates the effect of a diameter increase on the lateral bearing capacity of 2.2 m and 4.4 m diameter monopiles in dry sand. Static displacement controlled and oneway cyclic force controlled model pile load tests were performed using the Delft University of Technology geotechnical centrifuge.
Results show that the smaller 2.2 m diameter pile has a lower secant and tangent soil pile stiffness when compared to the 4.4 m diameter pile. In all cases the tangent stiffness is about 50% higher than the secant stiffness. Also, a force acting higher above soil surface yields a lower initial system stiffness. Results furthermore show that an increase in pile diameter with a constant slenderness or L/Dratio, relative density Id and load excentricity e, leads to a significant increase in static lateral capacity. The secant and tangent stiffness also significantly increase with increasing diameter.
The accumulation of lateral pile displacements as function of the number of applied oneway cyclic lateral loads has been investigated using 500 force controlled cycles. For an increasing number of load cycles the pile head displacements increase whilst the rate of accumulation decreases. However, additional loading cycles, up to e.g. 100000, are recommended.
For static loading conditions experimental results have been compared to the default API formulation for laterally loaded piles. This default formulation shows a significant overestimation of the initial stiffness. However, after incorporating a stress dependent secant stiffness E50, which has been derived from triaxial compression tests on model sand, good agreement is found between the experimental results and the modified API formulation for pile displacements <0.1D. For displacements of about 0.05D the modified py method underestimates the lateral bearing capacity of the 4.4 m diameter pile by up to 25.
Further research with loading conditions that mimic field loading conditions and a sample with a higher initial density are recommended. It is also recommended to im prove the current setup using better load control and a larger strongbox and to perform additional model pile tests on saturated samples.

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17 

Validation of PLAXIS Embedded Piles For Lateral Loading
In recent years, the embedded pile model has been successfully implemented in PLAXIS 3D. The embedded pile consists of beam elements connecting to the surrounding soil by means of special interfaces (skin interface and foot interface). Although the embedded pile doesn’t take into account volume, a particular elastic region around the pile whose dimension is equivalent to the pile diameter is assumed in which plastic behavior is neglected. This makes the embedded pile almost behave like the volume pile. Therefore, it may be said that the embedded pile model is considered as a ‘simplified’ model of the volume pile.
Although the embedded pile is a relatively new feature, it has been validated by comparisons with the volume pile as well as with measurements from real tests. The finding shows that the embedded pile is not only in good agreement with the volume pile, but also able to resemble the real pile behavior. However these validations are only considered in terms of axial loading (compression loading and tension loading). Therefore it’s questionable whether the embedded pile also shows a good performance in the situation of being subjected to lateral loading. In order to answer this question, this thesis is aimed to give a validation of the embedded pile for lateral loading caused by external forces as well as soil movements in embankment applications. This validation is firstly made in PLAXIS imaginary models (a ‘simplified’ model as considered in Chapter 3 and ‘advanced’ models as considered in Chapter 4) and then in a PLAXIS model of a real case study as considered in Chapter 5.

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18 

Stroming van beton in diepwanden
During the construction of a station of the north south line in Amsterdam a leak in the diaphragm wall lead to severe damage to adjacent buildings. The leak consisted of a clay deposit caught near the joint.
Until the excavation reached the level of the deposit, the deposit acted as a seal. After the excavation it started to leak and eventually failed. The following investigation let to no clear explanation of the presence of the deposit. Yet it revealed a lack of a clear understanding of the mechanisms. This prompted an investigation in to these mechanisms. This report deals with the aspect of the flow patterns of the concrete.
To investigate the flow pattern of concrete a numerical model has been used. A two dimensional model was created. In the model a constant stream of concrete was introduced in a layer of concrete submerged in a bentonite suspension. With this model a series of simulations are made. The first series is made with a varying yield stress of the bentonite suspension and the concrete. A second series is made with varying yield stress and the density of the bentonite suspension. Finally two simulations were made with varying spacing of the reinforcement bars.

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19 

Grondvervormingen ten gevolge van het maken van bouwputten
Dit afstudeeronderzoek richt zich op het grondvervormingsgedrag naast aan te leggen bouwputten.
Vooral bij diepe bouwputten in stedelijke omgeving is het onduidelijk hoe en waar het vervormingsgedrag, afhangt van de Nederlandse specifieke omstandigheden zoals de grondopbouw, belendingen en funderingen, tot stand komt.

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20 

Investigation into soil displacement near a jackedin pile in sand
When a pile is driven into soil, the soil is pushed away which results in significant changes in both stress state and strain state. Using Finite Element Code to simulate the pile installation process has been not yet completely successful partly due to the limited knowledge of the governing behavior of the soil around a displacement pile. An investigation into the soil behavior during a static installation of a jackedin pile in dry sand is conducted in this research.
The mechanism of pile installation is studied under a plane strain condition. A measurement method based on (1) digital photography and (2) digital image correlation was applied to observe the soil deformation around the pile during installation. Series of simple tests were performed and proved that the method offers sufficient accuracy concurrent with large number of measurement points within the observation area.
A series of four pile installation tests, with stress controlled on the top boundary, is conducted. The influence of initial void ratio and an additional surcharge on soil deformation was examined. The resulting displacement field was used to deduce the strain field around the pile and strain paths during pile installation process. The rigid/nearlyrigid cone of soil is found under the pile tip. Zone of high high volumetric strain and high shear strain locates below the cone and radially extends with respect to the cone. That a zone of high volumetric strain and considerable shear strain occurs along the pile shaft during continued penetration suggests an existence of the shear band. The inwards relaxation of soil elements near the pile shaft is confirmed by the tail at the end of the displacement trajectories and the peak of rotation paths in loose condition. The steady state deformation is also observed in loose assembly only.

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