The Netherlands is inherently challenged by water, as a large part of the country lies below sea level and several major rivers in North-western Europe cross the country. The most prevalent form of protection from coastal and river floods in the Netherlands includes approximately 22,000 km of earthen dikes, of which 3800 km are primary flood defenses (i.e., the first line of defense against high water). Subsidence, sea level rise, and the increase of rain intensity and river discharge due to climate change further challenge existing flood defenses to maintain required levels of safety. To do so, the top elevation of existing earthen dikes is often incrementally raised over time. However, raising a dike requires an extension of its base, which is frequently restricted by the presence of existing buildings and other spatial constraints. These dikes can be reinforced by alternative means such as a sheet pile wall. Another specific challenge regarding dike reinforcement in the Netherlands includes the presence of soft subsoil conditions at many dikes. These soft soils often consist of organic clays and peats. Such soils have a low stiffness and continue to deform over time; their strength is not well understood and often underestimated. Furthermore, organic soils are often not properly identified from Cone Penetration Tests (CPTs) using common interpretation methods, while CPT is the main testing method in the Netherlands. This research focuses on improving two aspects of the global stability assessment of dikes in the Netherlands: the modeling challenges of organic soil and dike reinforcement using sheet piles. Chapter 2 of this dissertation addresses the empirical relations for organic soils. The CPT-based correlation to derive the soil unit weight (Lengkeek et al. 2018) is validated and improved. Furthermore, new CPT-based correlations for organic soils are obtained by relating the soil state parameters to the cone resistance and the unique soil type properties to the friction ratio. An adjustment to Robertson (2010) CPT-based classification is proposed. In the improved SBT classification, organic soils (SBT=2) are redefined and subdivided into peat, organic clay, and mineral clay with organic matter. In chapter 3 the new Critical Stress Ratio (CSR) model is presented, which classifies as ‘Simplified Critical State Soil Mechanics’. The CSR model can be seen as a theoretical version of the SHANSEP equation, providing a link between effective stress parameters, obtained from common laboratory tests, and the undrained shear strength. The model can be implemented in LEM for ultimate limit state stability analysis. The CSR model provides the state dependent undrained shear strength for each stress point. The CSR model does not require to determine the exact yield contour as in a constitutive FEM model, this is taken into account by a variable spacing ratio, called the ‘Critical Stress Ratio’. This parameter of the CSR model can be regarded as the over-consolidation ratio at which no net excess pore pressures occurs, a parameter which can be fitted based on a few CAUC tests. Furthermore, the CSR model contains methods to obtain other model parameters for existing constitutive models used in the finite element method, such as the Poisson’s ratio which determines the horizontal and isotropic stress in unloading. Chapter 4 presents the set-up, results, and evaluation of the full-scale failure test. (In Dutch: ‘Eemdijk damwandproef’), initiated by the Dutch Flood Protection Programme. The Eemdijk full-scale failure tests involves separate tests on (1) sheet pile panels, (2) on a ground dike, as well as a combined test (3) on a ground dike with sheet pile reinforcement. The Eemdijk full-scale failure tests provides valuable insights through a detailed analysis of the deformations of dikes leading up to and beyond failure. Furthermore, the soil investigation is re-examined and parameters are determined for multiple constitutive models applied in FEM back-analyses. Finally, both the CPT-based methods, the CSR model and the SHANSEP-NGI-ADP model are validated at the Eemdijk test site. The back-analysis of the pull-over tests (PO-test) confirmed that the cross-section class 2 sheet piles (AZ26) reached the full plastic bending moment capacity and the cross-section class 3 sheet piles (AZ13-700 and GU8N) reached at least the elastic bending moment capacity. Furthermore, from the analysis of the SAAF measurements it is concluded that the stiffness of only the side sheet piles of panels should be reduced due to edge effects. The ground dike test (GD-test) and sheet pile reinforced dike test (SPD-test) allowed for a unique comparison and provided insight in the critical deformation rate prior to progressive failure. This criterion is useful in the assessment of unstable slopes. The GD-test illustrates the importance of high density of soil investigations and the importance of high quality CPTs (ISO class 1) and proper CPT based classification. The sheet pile reinforced dike test (SDP-test) shows that a continuous sheet pile, with sufficient length and embedment, makes an important contribution to the robustness of the dike after failure. Even after structural failure due to a plastic hinge, all sheet piles remained intact and interlocked. The failed sheet piles functioned as a weir and ultimately prevented breaching. Based on a careful examination of the Triaxial (CAUC) test it is recommended to use the 15% axial strain value as a basis for the ultimate value and to apply additional criteria to prevent unrealistic high or low values for the undrained shear strength, and to re-examine the applied geometrical corrections. Based on the performed variation analysis it is recommended to use average stiffness parameters in a SLS or ULS dike design analysis, when performed with advanced constitutive models in FEM. The alternative approaches to dike assessment presented in this research are expected to result in a more economic and better understood dike design and assessment based on improved field data interpretation (chapter 2,) undrained shear strength and modeling procedures (chapter 3) and takeaways from the full-scale tests and back analyses (chapter 4).@en

Dikes in the Netherlands have traditionally been constructed with soil. Climate change and subsidence requires heightening and or reinforcing these existing dikes. Traditional reinforcements demand additional space, which in some cases conflicts with existing buildings. Applying sheet pile walls in dikes allows for strengthening while minimizing the increase in footprint. However, a validated design approach that complies with relevant regulations lacks. To enable the validation of a proposed design approach, a full-scale field test programme (Eemdijkproef) was performed near the town of Eemdijk, The Netherlands. It consisted of a step wise approach: 1) sheet pile pullover tests, 2) ground dike stability test, 3) sheet pile dike stability test. All tests were loaded until failure occurred. The two similar test dikes were constructed at full scale (5m high, 25m wide, 60m long). In one dike an 18m long sheet pile wall was installed. This paper presents the test setup, monitoring, measurements and first findings. The test program provides better insight in the soil-structure interaction of the reinforced dike, on soft soil, under high water and uplift conditions. Ultimately this will lead to a validated design approach for sheet pile walls in dikes.@en

Parameter determination is the first step in geotechnical engineering. Engineers are often confronted with limited data, large variations and different types of tests, both in-situ and laboratory tests. Within this complex setting, Codes require cautious estimates, so called characteristic values, preferable substantiated with observations and statistical methods. In this study, these statistical methods for populations and trend-functions are elaborated. Most codes and standards only refer to population statistics, whereas the reality is that, with the use of CPTs, trend functions such as correlations or transformation functions are more relevant. The aim of this paper is to provide a method how to use CPT and laboratory tests in practice in order to calculate characteristic values, on the basis of pairwise established CPT-based correlations, typically applicable for line infrastructure projects such as levees. @en

The Afsluitdijk is one of the Dutch Delta programme landmarks. Afsluitdijk is a 32 km long primary flood defense, separating lake IJsselmeer from the Wadden Sea and protecting large areas of the Netherlands against flooding. Over the period spanning 2018 - 2022 the levee will be upgraded by the consortium Levvel (BAM, Van Oord and Rebel). Ice resistance is one of the aspects that is part of the engineering scope of the project. A detailed study on ice actions that apply to the various exposed structural elements is performed, specifically for the hydraulic structures that are integrated in the levee. Dutch regulations with respect to ice actions do specify some levels for ice actions but are not very specific regarding their range of applicability. Ice engineering experience from projects abroad is integrated with Dutch temperate winter conditions, to derive fit-for-purpose ULS and ALS ice actions. The analysis procedure is scenario-based, following the ISO 19906 (2nd ed) limit-stress, limit-force, limit-momentum based approach. This paper describes the study approach and the main results that are obtained. @en

Dikes in the Netherlands have traditionally been constructed with soil. Climate change and sub-sidence requires heightening and or reinforcing of these existing ground dikes. Traditional reinforcements de-mand additional space, which in some cases conflicts with existing buildings. Applying sheet pile walls in dikes allows for strengthening while minimizing the increase in footprint. However, a validated design approach that complies with relevant regulations lacks. To enable the validation of a proposed design approach, a full-scale field test programme (Eemdijkproef) was performed near the town of Eemdijk, The Netherlands. It consisted of a step wise approach: 1) sheet pile pullover tests, 2) ground dike stability test, 3) sheet pile dike stability test. All tests were loaded until failure occurred. The full-scale pullover tests (POT) consisted of 4 sheet pile configura-tions. The length of the sheet piles varies between 13 and 16m and the width of the panel varies between 1.8 and 4.2m. Both Z- and U-profiles have been tested. This paper presents the test setup, monitoring, measurements and first findings. The test program provides better insight in the soil-structure interaction of an embedded sheet pile in soft soil. Ultimately this will lead to a validated design approach for sheet pile walls in dikes.@en

Levees in the Netherlands have traditionally been constructed from soil. Climate change and land subsidence require heightening and/or reinforcing these existing levees. Traditional reinforcements demand additional space, which in some cases conflicts with existing buildings. Applying sheet pile walls in levees allows for strengthening while minimizing needed footprint. However, a validated design approach that complies with relevant regulations lacked. To enable validation, a full-scale field test programme has been performed near the town of Eemdijk (The Netherlands). This has resulted in better insight in the soil-structure interaction of the structurally reinforced levee, on soft soil, loaded by high water and uplift conditions. This paper describes the rationale behind the test setup and operation of the test programme in relation to the current design codes and guidelines. First the set of knowledge questions to be resolved is considered. These questions gave direction to the type of failure tests, the required instrumentation and the impact of conclusions.@en

The derivation of representative values for geotechnical parameters accounts for the various sources of uncertainty which are addressed at different stages of the determination process. A comprehensive flow chart for the determination of constitutive model parameters from site tests is proposed. The authors first consider a straightforward methodology to quantify the inherent uncertainty of variables measured from a CPT. An automated framework is then applied to merge outcomes from several transformation functions into a single combined output. This result can be subsequently updated with expert judgment or with direct measurements from laboratory tests using a Bayesian approach. When applied to the friction angle, a reduction of the posterior updated representative standard deviation is observed.@en

Selecting an appropriate soil constitutive model and determining the corresponding model parameters for numerical analysis are considered most challenging in geotechnical engineering. While many empirical relationships have been proposed to derive soil parameters from in situ test results, there is no clear procedure on how to derive model parameters uniquely. In practice, available data during the early stages of projects is often limited to field test data. Consequently, different engineers provide different numerical solutions for the same problem. As a solution, the authors present a proof of concept for an automated parameter determination (APD) system, using concepts of graph theory to determine constitutive model parameters from in situ tests while keeping the system transparent (verifiable) and adaptable (extendable). The study aims to increase the confidence in parameter determination for numerical analysis by giving the user of the system, the geotechnical engineer, control over the system. Using a spreadsheet of parameters and equations as input, the system generates paths between the parameters and calculates the parameter values for coarsegrained soil, starting from CPT data. Further validation and tweaking of the system, as well as the extension to other types of soils, are part of ongoing research. @en

Selecting an appropriate soil constitutive model and determining the corresponding model parameters for numerical analysis are considered most challenging in geotechnical engineering. While many empirical relationships have been proposed to derive soil parameters from in situ test results, there is no clear procedure on how to derive model parameters uniquely. In practice, available data during the early stages of projects is often limited to field test data. Consequently, different engineers provide different numerical solutions for the same problem. As a solution, the authors present a proof of concept for an automated parameter determination (APD) system, using concepts of graph theory to determine constitutive model parameters from in situ tests while keeping the system transparent (verifiable) and adaptable (extendable). The study aims to increase the confidence in parameter determination for numerical analysis by giving the user of the system, the geotechnical engineer, control over the system. Using a spreadsheet of parameters and equations as input, the system generates paths between the parameters and calculates the parameter values for coarsegrained soil, starting from CPT data. Further validation and tweaking of the system, as well as the extension to other types of soils, are part of ongoing research. @en

Performing numerical analysis successfully depends on several factors. One of the most important factors is determining the constitutive model parameters correctly. It is often the case that these parameters are determined based on limited soil data. Using in-situ tests for determining these parameters has several advantages such as minimal disturbance of the soil and lower cost compared to laboratory tests. However, it is not possible to determine soil parameters directly from in-situ tests results. Thus, empirical correlations are required for interpreting soil parameters. Generally, several correlations exist for the same parameter, which will lead to calculating several values for the same parameter. An ongoing research project focuses on formulating an automated parameter determination (APD) framework that uses a graph-based approach to identify constitutive model parameters based on in-situ tests. This is achieved by using two spreadsheets as an input, one for parameters and the other for equations (correlations used to calculate parameters). Based on these two spreadsheets, the system generates paths between the parameters and calculates the value(s) for each individual parameter. So far, the research project focused on determining the parameters for coarse-grained soil based on cone penetration test (CPT) results. Due to the fact that the system was set up in a modular and adaptable way, it is possible to expand the system to accommodate more soil types and in-situ tests. It is the aim of the research project to increase the reliability of the parameters values (required to perform numerical analysis) determined from in-situ tests. This paper focuses on expanding the current framework to determine parameters for fine-grained soil. By using the two spreadsheets as an input, the system successfully calculates the value(s) for fine-grained parameters. Further validation, dealing with several values for each parameter, determining the accuracy of derived parameters and expanding the system to accommodate other in-situ tests and types of soils are part of ongoing research.@en