Quay walls are earth-retaining structures that provide berthing for ships, enabling safe loading, unloading, and mooring. As vital port infrastructure, they must withstand increasing depths, heavier loads, and complex conditions. Finite Element Modelling (FEM) is widely used to study their behavior, but accuracy is limited by uncertainties in soil properties, constitutive models, and structural assumptions.

This study develops and validates a FEM of a smart quay wall in the Amaliahaven Project, Port of Rotterdam, using field monitoring data from staged dredging. The quay wall is instrumented with inclinometers that recorded lateral displacements during dredging. Geotechnical parameters were derived from Cone Penetration Tests (CPTs) and empirical correlations, with the Hardening Soil (HS) model adopted as the primary constitutive model. The HSsmall model was also tested to evaluate the influence of small-strain stiffness.


Initial FEM results underestimated displacements. Sensitivity analysis identified friction angles and stiffness moduli of key layers as the most influential parameters. Guided calibration using inverse analysis improved agreement, achieving accuracy within ±30% across dredging phases.

A key discrepancy involved front wall rotation. The assumed hinge connection between front and combi wall produced unrealistic behavior, while modelling it as fixed reduced errors to 13%, suggesting actual site conditions lie between hinge and rigid assumptions. Comparison of HS and HSsmall showed small-strain stiffness had minimal influence due to the high stiffness of sand layers.

A parametric study examined dredging depth, surcharge loading, and soil variability. Dredging beyond −21 m NAP and surcharge loads above 40 kN/m² significantly increased wall displacements, while anchor forces always remained below design capacity, confirming structural safety.

This research demonstrates that combining sensitivity analysis with calibration enhances FEM accuracy and highlights the importance of realistic connection modelling. ... Read more

Deep-sea quay walls in the Port of Rotterdam have been extensively constructed in the last 150 years and have been subjected to cycles of unload and reload of surcharge load along with fluctuating water levels. These cyclic load conditions significantly impact the continuous development of deformations in the quay walls and the forces in the structural elements over a long term. This study presents a detailed analysis of the long-term behavior of the quay wall located in the Hartel Tank Terminal at the Port of Rotterdam. This study also considers the effect of deeply embedded thin clay layers on the bearing capacity of the screw injection
(SI) piles. Previous research by Rica and Van Baars (2018) and Chai et al. (2022), among many others, have shown that the subsurface weaknesses, especially due to presence of deep clay layers, have a significant impact on the end bearing capacity of the closed ended piles loaded under compression. This effect depends on the location of the clay layer with respect to the zone of influence of the pile.
The two major structural responses observed in the behaviour of the quay wall is the accumulation of horizontal wall displacements and continuously increasing anchor forces in the tension piles over long-term application of the cyclic surcharge loads. The progressive increase in the anchor force is a direct result of the continuously increasing horizontal displacements of the wall.
Clay layer present in the deep Pleistocene sand in the vicinity of the tips of the bearing piles was shown to have a negative impact on the mobilised base resistance of the piles. In the case of a quay wall with a relieving platform and a bearing and tension pile trestle with inclined pair of bearing piles, where the complete load bearing capacity is derived only from the deep bearing sand layers, the impact was most significant i.e. at least a 10% reduction, when the clay layer was present from 3D below the pile tip to 1.5D above the pile tip, D being the equivalent diameter of the SI piles. The maximum reduction in the mobilised base resistance
was observed to be 38% when the pile tips were in the middle of the clay layer, with half the clay layer above and half below the pile tips.
This study provided valuable insights into the long-term deformation behaviour of the quay wall under cyclic operational and water loads. It also provided critical reasons to enhance site investigations to look for any subsurface weaknesses in the vicinity of structural elements and to optimise the pile design, such as embedment length, as per the actual subsurface conditions.
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This dissertation presents axial compressive load tests where the pile base and shaft resistances were measured with distributed fibre optic sensors. Two test sites were established: one at Amaliahaven in the port of Rotterdam, and another in Delft. At Amaliahaven, the performance of three different pile types was compared in very dense sand: driven precast, driven cast-in-situ and a screw displacement pile type known as a screw injection pile. The screw injection piles were further investigated in the medium dense sand of Delft, comparing screw injection piles installed with a removable casing to screw injection piles installed with sacrificial casings. With these tests, the influence of installation method on the axial pile capacity was examined, and the results were considered in the context of design methods which use the cone penetration test to predict the axial pile capacity.
The piles at Amaliahaven reached very high base and shaft resistances, up to 30 MPa and 600 kPa respectively. These values are nearly three times greater than limiting resistances in design standards, suggesting that limiting resistances lead to excessive conservatism in dense to very dense silica sands. On the contrary, the screw injection piles at Amaliahaven mobilised much lower base capacities than anticipated. This became the focal point for the tests at Delft, and likewise, the piles at Delft also mobilised much lower base capacities than forecasted.
The influence of different installation methods on the pile base resistance was then examined in a review of other instrumented load tests—a review extending beyond screw injection piles and to screw displacement piles overall. The analysis confirmed that the installation of a screw displacement pile leads to little soil improvement around the pile base. In other words, a screw displacement pile tends to mobilise base resistances comparable to a soil-replacing (bored) pile rather than a soil-displacing (driven) pile.
A larger database of both instrumented and uninstrumented test records was then used to consider the implications of these findings. To do so, the base, shaft, and total capacity of each pile was compared to design methods from Belgium, France, the Netherlands and the USA. These design methods tended to overestimate the pile base contribution yet underestimate the shaft contribution, especially at cone resistances greater than the limiting resistances. A best-fit to the measured base and shaft resistances gave the best agreement on average to the measured total capacity. Nevertheless, there is room for improvement with this new formulation, particularly for the shaft resistance of screw displacement piles with an enlarged displacement body.
From the findings in this dissertation, a series of adjustments have been proposed for the Dutch pile design standard NEN 9997-1. The tests presented in the dissertation are also the first set of pile tests to be incorporated into the Dutch national pile test database, with the findings also being used to refine and optimise quay wall design across the port of Rotterdam. ... Read more

The Global Wind Energy Council (GWEC) forecasts an accelerated increase in wind installations as a result of the aggressive climate change and green energy objectives set by the majority of countries. As a consequence, new regions worldwide that were previously thought to be unsuitable for the construction of offshore wind farms due to the soil characteristics are planned to be explored. This is the case of glauconite sands, which include glauconite pellets that are very susceptible to crushing. The crushing transforms the coarse-grained sand into a fine-grained soil, changing the geotechnical characteristics of the soil. This poses particular geotechnical challenges, since the soil-structure interaction between the pile being driven and the sand changes, the side friction increases with depth and the prediction of blow counts in drivability analyses is underpredicted. In addition to this, the glauconitic sand influences the response in cone penetration tests (CPTs), characterised by high cone tip resistance (qc) and sleeve frictions (fs), leading to high friction ratios (Rf) and resulting in misleading soil classifications. IQIP, as a company specialised in installation and foundation projects internationally that provides innovative and high-quality equipment and solutions for construction projects related to Offshore Wind industry, is interested in better understanding the mechanical behaviour of glauconite sand during pile installation due to the risks posed by this sand, e.g. premature pile installation refusal. In order to understand this soil that poses geotechnical challenges, laboratory test programs should be designed in order to capture the soil behaviour and physical modelling is a cost effective and valuable tool. This research aims to obtain detailed information on the soil response of glauconitic sand in saturated conditions during pile installation with a new sample preparation method for glauconitic sand containing fines. It will investigate the feasibility of cone penetration testing, cyclic loading, pile driving, as well as the analysis of the shear band and grain crushing around the instrumentation penetrated in the sample in a calibration chamber (CC). Based on the results from the three performed tests it could be concluded that the preparation method led to a good procedure to prepare repeatable and homogeneous samples under fully saturated conditions, as well to a representative response to pile penetration. With this, it is possible to perform further research on the sand fraction of glauconitic sands using the same sample preparation method and testing equipment. ... Read more

With the continued growth of the offshore sector and plans for new wind farm developments, shallow marine environments are becoming key areas for the renewable energy projects. As a result, the likelihood of encountering glauconitic sands is growing, posing challenges to the offshore wind infrastructure. Glauconite, or glauconitic sand, also known as ‘greensand’, refers to a soil containing peloidal sand-sized grains primarily comprised of mineral glauconite, an iron- and potassium-rich 2:1 interlayer-deficient mica. The tendency of glauconite to transform from sand to fine-grained soil with shearing creates uncertainties in site characterization and negatively impacts pile drivability to targeted depths. This thesis examines shearing behavior of glauconitic sands at soil-pile interface using two samples of Belgian glauconitic sands. With the final goal being the derivation of reliable interface shear strength parameters, the study aims to develop test procedures capable of capturing the transition of glauconitic sands from their natural uncrushed state to a reworked degraded condition, simulating the effects of shear-induced particle breakage during pile installation. To achieve this, a systematic experimental program was completed in two phases. The first part focused on glauconitic sands in their natural state and the second aimed to assess the degraded soil. Comprehensive material characterization, including geotechnical index tests, mineralogical analyses, and soil-steel interface direct shear tests under various conditions, was carried out to support each phase. The findings link the interface shear behavior and strength of glauconitic sands to their intrinsic properties, identify limitations in current experimental procedures, and offer recommendations for future research. New insights are provided into the behavior of Belgian glauconitic sands with the relatively low glauconite content and varying crushability potential. Interface roughness, shear rate, and normal stress effects are considered. ... Read more

This thesis examines the load distribution on 60 m long piles under gradual static loading, considering the POST Rotterdam high-rise building as the study project. The research employs fibre optic (FO) instrumentation on site to monitor strain changes in the piles over time and assess load transfer mechanisms. This data is integrated into a Plaxis 3D model of the building's foundation to validate existing approaches on soil structure interaction (SSI), optimize SSI modelling, and assess the high-rise building's impact on nearby structures. Results show that at early stages, the resistance contribution comes from the shaft in contact with the Pleistocene sand layer. However, as loading progresses and the Kedichem clay layer consolidates, most of the resistance shifts to the tip and the shaft located in the deeper sands. The FO strain measurements follow a similar trend to the site stratigraphy, but there is high uncertainty about the results at early load stages. The latter requires further investigation to corroborate once the building is finalised. The piles were incorporated into the Plaxis 3D model by means of EBR with a layer-dependent force distribution. The resulting spring stiffness of various pile groups reveals the significance of the group effect. Regarding the impacts of POST loads on the adjacent Old Post Office building, an angular distortion of 1/555 in 50 years was obtained, which indicates a conservative result of slight damage in the structure. For the Timmerhuis building, a resulting angular distortion of 1/1428 indicates no damage. This study addresses gaps in understanding load distribution in 60 m long piles, offering a practical modelling approach and recommendations for future research. It contributes to optimizing design and safety protocols as the use of such piles becomes more common in Rotterdam. By utilizing advanced sensing techniques like FO, this research may lead to more accurate pile design and criteria, potentially reducing construction costs and enhancing safety for high-rise buildings and their surroundings. ... Read more

In the past decade, suction caissons have emerged as a preferred offshore foundation solution for wind turbines due to their silent installation process and potential for recyclability. However, there has been growing speculation regarding the necessity of under base filling, which involves filling the gap between the top plate of the suction caisson and the seabed. Some experts have suggested that under certain conditions, this under base filling may not be required at all. Furthermore, concerns have been raised about the efficacy of under base filling in achieving full contact between the top plate and the seabed, as it has been observed that gaps may persist even after the filling is applied. Consequently, doubts have been cast on the overall need for under base filling. However, there is limited research focused on understanding the behavior of water plugs in the absence of under base filling, at different loading conditions ( Compression , tension , cyclic etc.). This knowledge gap motivates this thesis study, which aims to investigate the behavior of water plugs specifically in dense sand samples, as sand is considered more critical compared to clay in terms of its variability in drainage conditions that can influence the foundation’s performance. To achieve this, a series of centrifuge tests were conducted on suction caissons that were partially installed and some fully installed. The results of the experiments shed light on the role of under base filling in different loading scenarios. Under monotonic compressive loading at higher rates, it was observed that under base filling played no significant role in the load transfer . Both the caissons with and without under base filling exhibited similar load transfer mechanisms, indicating that filling the gap may not be necessary in such loading conditions. Additionally, under tension loading, it was found that under base filling had little to no effect on the development of tensile capacity. By expanding our understanding of the necessity and effectiveness of under base filling, this study contributes to the ongoing discussion surrounding suction caisson design and installation practices for offshore wind turbine foundations. ... Read more

The objective of this thesis is to enhance understanding of the behaviour of a flexible dolphin and its interaction with the surrounding soil in order to determine the optimal embedded depth. A comprehensive field test is conducted to gain deeper insights into the behaviour of the flexible dolphin and the soil surrounding the pile. The test measurements are then analysed to assess the pile's behaviour. Additionally, calculation models are employed to predict the pile's behaviour, and a comparison is made between the measurements and predictions.
Four different calculation models, namely Blum, Brinch Hansen, P-y curves, and Plaxis are utilized to predict the pile's behaviour during the test. The pile behaviour is compared across these models. While most models do not account for repetitive loading, the best available inputs are employed to simulate the test as accurately as possible. The majority of the models exhibit similar top displacements of 0.9 meters, except for the drained Plaxis model, which calculates displacements of 1.05 meter, and Blum's model, which calculates a displacement of only 0.8 meters.
During the test, multiple instruments are employed to measure various parameters of the pile, including load, displacement, water pressures, and strains at different depths and time intervals. The total station measurements indicate a maximum displacement of nearly 0.7 meters, which differs by 0.2 meters from the predictions.
The deviation between the predictions and measurements can largely be attributed to inaccuracies in the hydraulic jack load measurements. The pile load was back-calculated using the strain data obtained from the pile. The loads estimated based on the strain measurements were found to be hundreds of kilonewtons lower than the hydraulic jack load measurements. As the strain measurements were considered more reliable, the actual load during the test differed from the prescribed load scheme. Consequently, the load inputs in the models need to be adjusted to align with the loads derived from the strain data.
The displacement measurements are analysed and compared with each other. The Saaf and optical fibre measurements exhibit similar curvatures, enhancing the reliability of the optical fibre strain measurements during load analysis. However, the total displacement measured by the Saaf and the total station do not match due to the incorrect assumption of zero movement at the pile tip. Determining the exact displacement of the entire pile is impossible due to the inadequate number of boundary conditions available to translate the Saafs curvature measurements into displacement.
The calculation models utilize the loads derived from the strain measurements to make predictions, and their results align comparably with the measurements. Plaxis is the only model capable of simulating different load cycles, which improves the comparability of the Plaxis results with the test.
Load-displacement graphs obtained from the Plaxis results and the optical fibre measurements display hysteresis in load cycles, consistent with findings in existing literature. The initial load exhibits less stiffness compared to the repetitive loads in both datasets. The amount of energy absorption by the soil is determined from the areas of the loadcycles. When considering the most complete load cycles, Plaxis conservatively estimates the absorbed energy.
Reducing the length of a pile results in larger displacements of the pile, while concurrently enhancing its capacity for energy absorption. However, it is crucial to strike a balance between these two parameters, while paying close attention to the permanent soil displacements.
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The energy market is growing and noise regulations for offshore foundation pile installation grow stricter. New initiatives arise to comply with the ongoing developments in the field, such as the BLUE Piling Technology under development by IQIP. Its features are presented as reduced underwater noise levels during installation, which is attibuted to the lower pile wall vibrations caused during driving. In this thesis, the design and execution of a field test is described, identifying the most important differences in geotechnical aspects between a prototype Blue Piling hammer and a conventional impact hammer, the IQIP Hydrohammer S-30. The results show that the Blue Piling hammer creates a response between pile and soil that is very different from a conventional impact hammer. The fundamentally different soil response led to pile plugging during the field test, affecting the stresses around the pile tip. This phenomenon is unlikely to occur during monopile installation, but scaling the test results requires further research. ... Read more

Pile foundations have been utilized for centuries to support large structures in soft soils. Pile installation plays a critical role in foundation engineering, and historically, empirical formulas were employed to predict pile driving outcomes and bearing capacity. However, these formulas exhibited considerable variability in their predictions. In the 1960s, the application of stress wave theory gained popularity, accompanied by the introduction of stress wave measurement equipment and software. This theory provided a better understanding of the dynamic and static behaviour of the hammer-pile-soil system, enabling the development of reliable soil reaction models to estimate the mobilized pile capacity.

Within this context, the aim of this master's thesis is to investigate the accuracy and applicability of cone penetration test (CPT)-based axial pile capacity design methods for the static component of the mechanical system, as described by the TNO soil model. The TNO soil model aims to model the dynamic soil response during a dynamic load test after pile installation. In this mechanical system, the springs at the shaft and base represent the soil stiffness during dynamic loading, while the plastic sliders correspond to the local ultimate shaft friction and ultimate base stress, referred to as yield stresses in the TNO soil model. The objective is to verify whether design methods for static pile capacity can be applied to the static portion of the dynamic soil model through signal matching analysis.

The dynamic component, represented by a dashpot, is associated with theoretical solutions for shaft and base radiation damping. In the TNO model, damping is independent of static resistance, and viscous damping, which is part of the mobilized static friction, is neglected. The design methods utilized in this study are the unified methods for driven piles in sand and clay, which are employed to determine the local ultimate shaft friction and end bearing resistance, incorporating setup factors based on the time elapsed between the end of installation and pile testing.

The calculated local ultimate shaft friction obtained from the design methods serves as the starting point for the signal matching analysis, which is conducted after dynamic load testing to establish the mobilized pile resistance during a hammer impact. The mobilized end bearing resistance is derived through signal matching after a high-quality match on the shaft friction has been established. The obtained base stress is correlated with the ultimate base stress provided by the design methods to determine the degree of stress mobilization at the base in a dynamic load test. The ultimate base stress is typically established at a pile base displacement of 10% of the pile diameter; this amount of base displacement is often not reached after a single hammer blow.

The signal matching analysis aims to align the signals acquired from dynamic measurements (force and velocity) with a simulated signal generated by a user-dependent specific soil model that most likely represents the in-situ soil conditions based on the solution of the one-dimensional wave theory. AllWave-DLT is employed to conduct the signal matching analysis, where force and velocity measurements collected by a Pile Driving Analyzer (PDA) are utilized to derive the deep foundation forces, encompassing displacement-dependent static resistance and velocity-dependent dynamic resistance.

Overall, this thesis explores the application of CPT-based axial pile capacity design methods in the TNO soil model and, at the same time, the obtained radiation damping constants are correlated to geotechnical soil parameters derived from soil investigation. ... Read more

Quay walls are often designed with Finite Element models (FE models) to take into account the complex soil-structure interaction and highly non-linear soil behavior. However, the effect of temperature variations is uncertain if it is taken into account in the design of the quay walls at the Port of Rotterdam.

Nowadays, new quay walls are often equipped with sensors that collect information about their behavior. These quay walls are known as smart quay walls. The measurement data of smart quay walls could be used to validate FE models and reduce parameter uncertainties. This could lead to an optimization of the functionality of the quay walls.

Smart quay walls have been observed to show much higher strain levels in the anchors during summer compared to the winter period. According to strain records, differences of up to 10% and 20% seem to be present, which is quite high. The objective of this thesis is to verify the effect of temperature on anchor force in quay walls using the data of smart quay walls.

The data analysis that took place analyzed data from five different quay walls (HHTT, SIF, EMO, Brammen terminal, Brittanniëhaven). Deformations, strains, anchor forces, groundwater levels and temperatures are some of the measurements that were investigated in order to understand the quay wall reaction to the seasonal temperature fluctuation effect. The most useful measurement data proved to be the deformations of the combi walls and the anchor forces in the MV-piles.

This research will eventually highlight the results of the extensive data analysis from different smart quay walls, while it will further prove that quay walls are affected by the effect of seasonal temperature fluctuation. The gain is that with the available data, it is verified that the wall is moving back and forth depending on the season. However, the deformations are minor compared to the deformations of the dredging period.

After data analysis, a FE model was set up to predict the deformations and anchor forces of the quay wall during seasonal temperature fluctuations. For the parameter determination, CPTs, later research projects, design records and triaxial tests were used. Regarding the FE model, the case that was used is the HES Hartel Tank Terminal (HHTT-quay), which is a smart quay wall in the port of Rotterdam. HHTT quay wall was selected as the most well monitored quay wall regarding the needs of this research. Moreover, the HHTT-quay consists of sections with and without a relieving platform. Both types were considered in this thesis.

Then comes the validation of the FE model with the measurement data. Moreover, having a FE model in PLAXIS 2D which can realistically model the cycle heating effects, could be used both to estimate deformations due to climate change effect, as well as the anchor forces leading to better quay wall design for the future.

As with all of the cycle effects, heating and cooling of the quay wall could cause deformations that after many years of operation of a quay wall could lead to excessive deformations. Additionally, increasing temperature will cause higher temperature fluctuations, which means larger cycles. Therefore, further research with more cycles, better quality data and a FEM that could calculate the cycle heating effects is crucial to a better understanding of the cycle phenomenon. ... Read more

In the field of structural and geotechnical engineering, a uniform approach to predict and model foundation settlements during the design phase of a high-rise building appears to be missing. In the Netherlands, pile foundations of tower structures underlain by compressible soil layers are challenging to model due to different stiffness and load distribution effects. As a result, the Dutch building code currently used for foundation design, the NEN9997-1, does not include realistic soil-structure interaction (SSI) effects. Instead, the NEN defines a simplified approach for high-rise buildings as the sum of two types of foundation settlements: individual pile head settlements (s1) and pile group settlements (s2) due to compressible layers below pile tip level.

Numerical models were used in this thesis to predict the individual contribution of different soil layers to measured subsidence of tower structures. By running several simulations using Tomlinson’s load spread method and the new embedded beam formulation (EB-I) in Plaxis 3D, it was found that approximately 65% of the total (s2) settlements are caused by the compression of clay layers below foundation level. Moreover, the effects of different pile factors (αs, αp) on the load distribution (more pile shaft resistance versus base resistance) from superstructure to subsurface were investigated. This research concluded that updated pile factors - in accordance with recent pile load tests on the Maasvlakte (Gavin, 2020) - influenced the predicted and modelled pile head settlements (s1) slightly for a Fundex 560 pile. Nonetheless, the change in load distribution due to different pile factors did not affect the vertical effective stresses or resulting (s2) settlements at depth.

Further, to accomplish a more uniform modelling approach for high-rise building settlements, this thesis provides insights for an automated soil-structure interaction mattress methodology as illustrated in Figure 1. A model verification is proposed for the mattress model approach using finite element software commonly used by geotechnical (Plaxis 3D) and structural engineers (SCIA Engineer) in daily practice. In essence, it is based on a simplified (s2) settlement analysis from Plaxis 3D (step 1) and mattress fit model in SCIA Engineer (step 2) consisting of multiple springs with linear stiffness (k_bedding) connected by a plate (E_plate) and a simplified surface load on top. The surface load represents the quasi-permanent building loads. An apparent limitation of the Plaxis 3D model (step 1) was the missing building stiffness or load redistribution within the superstructure due to differential settlements over time. However, a modelling discrepancy of only 1% was found for both the peak and differential settlements between SCIA Engineer (step 3) and Plaxis 3D (step 4) for a theoretical, symmetric high-rise building of 69 m in the North of Amsterdam. Thus, a model verification was accomplished by comparing the settlements from Plaxis 3D with the building on top of EB-I embedded beams (step 4) to the deformations of the fitted mattress model (k_bedding + E_plate) representing the compressible soils underneath the structure in SCIA Engineer (step 3). Altogether, this thesis provides a solid foundation towards a more universal design methodology between multiple stakeholders while including SSI effects for settlement predictions of high-rise buildings in daily practice.
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In the next decades, Rijkswaterstaat will renovate many existing immersed tunnels so they can meet their intended lifespan in a good condition. Ongoing settlements could be a threat to the tunnel structural performance, as deformation may cause structural damage. Currently, immersed tunnels are subjected to greater and more uneven settlements than considered in the design. The issue of these ongoing settlements is mainly concentrated in the segment joints, which have typically been executed by a spigot and socket structure to prevent differential settlements. Significant deformation of the tunnel structure could result in concrete cracking, which entails the risks of structural connection loss, tunnel misalignment, and leakages (leading to durability reduction and damage to installations). This could impact the reliability of the structure over time, and consequently affect the availability of the road network. Therefore, the key objective of this research is how to assess the structural reliability and tunnel availability, and to investigate in which way the performance of existing immersed tunnel structures could be optimised given the ongoing settlements. Assessing the residual lifespan is beyond the scope, but optimising the tunnel performance during the remaining operational life is the main motivation for this research project. The research methodology consists of a parametric structural model, which determines the tunnel reliability and availability by using a Monte Carlo approach. The Noordtunnel case is used to demonstrate the research methodology, as this tunnel showed excessive settlements and a major renovation will be performed in the coming years. Additionally, the maintenance and renovation strategy for the segment joints in immersed tunnels are examined, to optimise the performance throughout the residual lifespan. ... Read more

Suction caissons have been used extensively for anchoring and supporting the offshore installations like oil platforms and wind turbines. These foundations are normally subjected to complex combinations of the vertical, horizontal and moment loads (i.e. V, H, M) from the self-weight, wind, wave and currents. In the past decades, extensive studies have been conducted to investigate the combined V-H-M loading behaviour of suction caissons in clay. However, most existing studies are focused on the ultimate bearing capacity, while the deflection response is more critical in foundation design for recent infrastructures like offshore wind turbines. Due to the complex load conditions, predicting the three-dimensional (3D) deflection response of the foundation is still challenging. Machine learning (ML) appears on the research horizon due to its excellent capacity of solving nonlinear problems with desired speed and accuracy. However, conventional machine learning approaches were limited in their capacity to analyze raw natural data without artificial interventions. Meanwhile, the deep learning technique (DL), as a branch of machine learning, allows a machine to be fed with raw data, automatically extract the features, and discover intricate structures in high-dimensional data. The deep learning technique has been used in many fields like language translation, auto-pilot and image recognition. And Deep neural networks, including deep learning algorithms and architectures, are gradually being developed. In light of these backgrounds, this study proposed to develop a deep learning based surrogate model to predict the 3D deflection response of suction caissons under combined V-H-M loading. The advanced three-dimensional nonlinear finite element (FE) simulations under complex V-H-M loading paths were performed on suction caissons of different geometric configurations and in clay soils with different stiffness and strength properties. The 3D FE simulation data was then used to train the deep learning based design model. Three popular neural network structures, i.e., Feed forward Neural Network (FNN), Convolution Neural Network (CNN), Recurrent Neural Network (RNN) have been employed to develop the hybrid surrogate design model. In this study, two different training strategies were proposed for this geotechnical problem. In the first category, the 3D load-deflection behaviour of suction caisson is idealized as a point-to-point mapping problem, i.e. mapping between the deflections (i.e. displacement and rotation) with loads (i..e force and moment). This task was achieved by Fully-Connected Neural Network model (FC-NN) based on FNN, One Dimension Convolution Neural Network model (1D-CNN) based on CNN and Long Short Term Memory model (LSTM) based on RNN. In the second training strategy, the load-deflection response was idealized as a time series process, a line-to-line mapping problem, mapping between the past loading paths (i.e. 10 groups of forces and moments) with future loading paths (i.e. 90 groups of forces and moments). Besides the three neural network models mentioned before, another two complex and advanced models, LSTM Model combined with convolution neural network (1D-CNN+LSTM) and Temporal Convolutional Network model (TCN), are also applied for temporal prediction. The performance and training efficiency of these models were also systematically evaluated by interpolation and extrapolation experiments. Basically, all the models can well capture the 3D deflection response of the foundation with significantly high accuracy (i.e., root mean squared error is smaller than 0.05 and coefficient of determination is near 1.000) than the traditional design approach (such as macro-elements model), and with greater efficiency than the 3D FE simulations. Among all the models, the TCN model has the highest prediction accuracy and robustness. However, the FC-NN model has the simplest model structure and highest computational efficient in learning the non-linear relationship between deflection response and V-H-M load. Besides capturing the relationship between input and output, the deep learning model can also assist to identify the intrinsic failure mechanism. By observing the fluctuation of generalisation ability, the evolution of the failure mechanism of suction caisson with embedment depth was revealed. ... Read more

Inefficient installation of pile foundations may lead to high risks of material damage, inadequate pile capacity, and time delays that can have significant financial implications to any kind of project, both onshore and offshore. Therefore, there is high demand for a comprehensive driveability analysis that considers key aspects of the installation process, such as the soil conditions, the pile-soil interaction and efficiency of the driving equipment used.
The total resistance during pile driving is usually estimated through numerical simulation techniques based on the wave equation, whereby the main inputs are the hammer, pile and soil properties. Commercially available driveability software, such as AllWave PDP, enable the modelling of the hammer-pile-soil system and simulate the stress wave phenomena during the installation process. Moreover, these programs have an integrated database of a variety of hammer models (hydraulic, diesel and more) that are used in practice, and also static and dynamic parameters for a variety of soils.
One of the key aspects in which this Thesis focuses on, is the static component of the driving resistance, referred to as SRD. Over the years, various SRD models have been developed, with the aim of estimating the static soil resistance during driving, while the dynamic components of the total resistance (increasing resistance due to inertial and viscous rate effects) are commonly being quantified in terms of damping factors.
This Thesis investigates the performance of frequently used traditional driveability models, such as the Alm & Hamre (2001), Toolan & Fox (1977) and Stevens et al (1982), in predicting the SRD in dense sand conditions. Furthermore, it examines the application of the Unified Method in SRD estimations. The Unified Method is a recently developed static capacity design approach for driven piles in silica sand. This design method will be included in the forthcoming 2022 edition of the ISO guidelines and will replace the four CPT based design methods (ICP, UWA, NGI, Fugro).
The performance of the aforementioned models has been evaluated through predictions of blow count profiles by utilizing pile driving records from five sites in the Netherlands, namely the Eemshaven (project known as Euripides) and APM, RWG, SIF and HHT terminals in the Port of Rotterdam. The diameter of the open-ended steel tubular piles examined in this study, is 0.762 m for the Euripides project and 1.42 m for the rest of the projects.
This research, will eventually highlight advantages and disadvantages of the commonly used SRD models, while it will further prove that by modifying the Unified Method, overall better driveability predictions can be made for a larger range of pile diameters than the current methods. The gain is that on one hand, with improved driveability predictions it is possible to minimize installation risks, optimize driving acceptance criteria, and select an appropriate hammering equipment. On the other hand, having a set of formulas that can be used both in estimating the SRD, as well as the static axial capacity, can reduce the engineering effort.
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In the low-lying parts of The Netherlands challenging ground conditions are often encountered. Thick layers of soft material such as peat and clay are present and pile foundations into deeper sand layers are required when objects are constructed that have to transfer significant loads to the subsurface without inducing settlement (differences). This also counts for pile foundations of wind turbines which, apart from compression and tension loads also are subjected to horizontal loading. The horizontal translational stiffness is an important and depending on the wind turbine manufacturer governing aspect in the required dimensions of the pile foundation (number and type of piles). In order to improve this horizontal translational stiffness, the foundation designer usually opts for the use of battered (raked) piles. The basic principle is that the axial stiffness of the pile will, in this way, contribute to the horizontal stiffness of the foundation as a whole. The verification of wind turbine requirements usually involve the use of generally accepted analytical 2D methods, simplifying the more complex 3D effect, to model the interaction between soil-pile and the group effect for closely spaced piles. Although the analytical model generally provides good results, investments can reduce significantly when only a small amount of piles can be saved upon. Also the effort in the field is reduced when using vertical piles... ... Read more

In recent years, distributed fiber optic sensing (DFOS) technology has been widely used in monitoring the strains developed in the structures.
The main focus of this report is to identify strains distribution while hammering/jacking pile and analyzing the uncertainties between the theoretical, measured strain through datalogger in concrete and steel piles. This assessment is done to gain confidence over the feasibility of using DFOS technology. Fiber optic cables are embedded all along the length of the concrete and steel piles with ends connected to the datalogger. To confirm the accuracy of the datalogger, other strain measuring devices like load cell and strain gauges are also glued to the piles. For both the piles load with in the yield limit is applied and strains are measured. fTb 2505 datalogger posses high accuracy with lower spatial resolution where as Luna Odisi datalogger has high spatial resolution and less accuracy which can be directly reflected through the strains obtained from both datalogger. Results obtained from steel pile reflects that strains obtained from Luna Odisi datalogger and load cell matches with in the accuracy and with no slippage . But for concrete piles fTb 2505 datalogger shows more fluctuating strains as compared to the strain gauges with uncertainties included in both the devices. ... Read more

Offshore structures are often founded on mud-mat foundations which prevent the structure from settling excessively. Pressure differences are generated under mud-mats during removal from the seabed. These differences lead to a force that resists the uplift. A literature study on breakout resulted in a hypothesized distinction of four mechanisms that occur during the uplift of offshore shallow foundations. An experimental program was designed to study these mechanisms. Small-scale tests on clay and sand were executed. The effectiveness of selected mitigation measures was studied, as well as the influence of the measures on the mechanisms. Existing calculation methods that model suction or quantify the breakout force were evaluated. It is believed that the results from the experimental program led to a comprehensive list of parameters that should be included in a design method to model the total resisting force to uplift, taking the mechanisms into account. ... Read more

The Automated Parameter Determination project aims to provide advanced geotechnical models parameters from in-situ tests in a transparent and flexible process. The framework was initially developed for coarse-grained soils, and it was needed to be expanded to all types of common soils. This report presents the expansion of the APD database to deal with fine-grained soils, claylike soils specifically. The APD variability assessment framework is customised to deal with log-transformed correlations’ uncertainty. Moreover, it is found a large dependency on Atterberg limits for claylike soils parametrisation. Only one set of correlations from CPT database is found in literature to obtain these limits, for which a new set is developed based on critical state soil mechanics and the assumption that the CPT friction sleeve is similar to the remoulded undrained shear strength. The proposed correlation is validated with a published database, showing acceptable results with similar variability when compared to the existing equation. A first validation of the complete model parameters for fine-grained soils using Plaxis Hardening Soil with small strain stiffness model is achieved. The Plaxis Soil Test facility is used and the results are compared with triaxial and oedometer tests, showing good results in compressibility characterisation and low estimation of friction angle, possibly attributed to organic and silt content. The friction angle characterisation is discussed, and it is concluded that a better estimation for fine-grained soils is needed to be studied. Further studies on soils in between claylike and sandlike behaviour is needed, as well for organics. ... Read more

In modern piling technology screw piles are used as a type of deep foundation for engineering structures, with the principal benefit of using said piles is that they offer an installation method that is virtually noise and vibration free. This makes these piles ideal for construction works in urban areas where surrounding structures can be affected by vibrations that would be produced from the installation of a driven pile. Since their initial production in the 1980s in Europe, multiple variations of screw piles are on the market today. This Msc thesis focuses on the Screw-Injection piles (SI-piles) commonly known as Fundex piles. SI-piles are a type of partial ground displacement piles where only a portion of the soil surrounding the pile is being pushed radially outwards during the rotational motion of screwing in the installation process. The other portion is transported back with grout flowing to the surface.

The current Dutch practice already have NEN guidelines on how to predict bearing capacity for SI-piles. These guidelines consist of CPT-based methods with an empirical correlation factor, the $\alpha$ pile class factor, which helps to relate the bearing capacity to the soil surrounding the pile. Nevertheless, one aspect that is not well understood is the effect that different properties of the injected grout have at the soil-pile interface and for bearing capacity. In this thesis two grout properties are being manipulated which are the Water/Binder and W/C ratios of the grout mixture, and the injection flow rate of the grout with the purpose to see whether and/or to what extent a difference exists in the shaft bearing capacity for SI-piles.

A full-scale experiment was conducted on 15 piles in order to evaluate the effect of these varying parameters. This research is composed of four targeted variations of W/B ratio and two injection flow rates, 5 groups of 3 piles each to be more precise. The piles were subjected to a static pile load test in tension, which means that the bearing capacity is composed of mainly the shaft resistance of the pile. The analysis breaks down in four main parts to analyse the indirect relationships between the properties that are accounted for in the empirical parameter $\alpha$. These four parts include the assessment of the load-displacement behaviour of the SI-piles, assessment of radial soil stress (CPT data), assessment of the records during the installation process (torque, RPM), the grout properties during installation and after 28 and 56 days of curing, and lastly, the pile shape (volume) after extraction of pile.

The assessment of the load-displacement behaviour showed that the predictions using the NEN guidelines for bearing capacity were extremely accurate for most pile groups (above 0.970 measured/predicted ratio). But for the pile groups with higher W/B ratio and with the highest flow rate (Groups C and D respectively) the measured shaft capacity would be much lower. A direct relationship between the W/C and W/B ratio is difficult to conclude since for pile B2 and C1 that had the same W/C ratio, the difference in the measured/predicted ratio was about 21\%. In the case of flow rate it is entirely seen that a higher flow rate leads to a significant decrease in measured shaft capacity. The NEN suggests a value of $\alpha_t$ for SI-piles of 0.009, yet the shaft capacity for groups with a higher W/C ratio and flow rate could be better predicted with an $\alpha_t$ $\approx$ 0.00793. Additionally, another important research objective is to try to optimise the $\alpha_t$ parameter by comparing the $q_c$ values for the pre-installation, the average post-installation and minimum value of the post-installation CPTs. This resulted in the $\alpha_t$ derived from the pre-installation CPT to have a much lower Coefficient of Variation, CoV, of approximately 0.08 whereas the average and minimum post-CPT $\alpha_t$ had a CoV of 0.12 and 0.11 respectively.

The assessment of the soil stresses is comprised of an analysis of the changes in cone resistance, $q_c$, throughout the field. The analysed data collected shows that for varying W/B ratios there is no solid relationship that relates the change in $q_c$ after the grout installation. However, a higher flow rate seems to have a significant impact on the cone resistance, leading to a general decrease of $q_c$ after installation, having a decrease as low as -16.53\% for pile D1, whereas for all other pile groups there was an increase in $q_c$ after installation, increases as high as 30\% (pile A3).

The assessment of the records during installation include the analysis of the torque during the installation process. It is seen that in both cases, high W/B ratio and high flow rate, there is a decrease in torque, but the flow rate of 115 [l/min] had a more significant impact than the increase in W/B ratio.\\
% Moreover, the 2D interpolation analysis aimed to see how post-installation CPT data should be considered. Pre-installation CPT data is sufficient to make a prediction on bearing capacity, but in this analysis both situations are being compared. This comparison resulted in that the difference between the two is minimal, the maximum difference found was in the order of $\pm$5 MPa.

The assessment of backflow grout resulted in higher W/C ratios having higher increases in density of the backflow fluid, and that high flow rate leads to a lower backflow density, this was supplemented with the sand transport data which suggests that higher W/B ratios lead to more sand transport out of the soil body. Furthermore, a inversely proportional relationship was found between W/B and W/C ratios and both the axial and bending stresses; the same inverse relationship is found with the flow rate. Additionally, the shear stress of the grout and of the soil were compared in order to determine if the failure is purely geotechnical or also structural.

The pile shape assessment resulted in a higher W/B ratio leading to a higher pile diameter, regardless of the flow rate during injection. There is also a very clear, almost perfectly linear, relationship between the mean diameter of the extracted pile and the measured shaft capacity. However not all piles were extracted and this includes piles installed with the highest W/C ratios (group C) and thus the aforementioned relationship has only been shown for a limited set of piles. ... Read more