Input of advanced geotechnical modelling to the design of offshore wind turbine foundations (Apport de la modélisation géotechnique avancée au dimensionnement de fondations d’éoliennes offshore)

The offshore wind sector is skyrocketing worldwide, with a clear trend towards wind farms installed in increasingly deep waters and harsh marine environments. This is posing significant engineering challenges, including those regarding the design of support structures and foundations for offshore wind turbines (OWTs). Substantial research efforts are being devoted to the geotehnical design of monopile foundations, currently supporting about 80% of OWTs in Europe. This paper overviews recent work carried out at TU Delft on the numerical integrated modelling of soil-monopile-OWT systems, and its input to the improvement of geotechnical design approaches. The benefits of incorporating advanced soil constitutive modelling in three-dimensional finite element simulations are highlighted, with emphasis on the interplay of cyclic soil behaviour and dynamic OWT performance. Ongoing research on high-cyclic soil plasticity modelling is also presented, and related to the analysis of monopile tilt under irregular environmental loading

Understanding the natural consolidation of slurries using colloid science

Many projects (Marker Wadden, Kleirijperij) have recently been initiated in the Netherlands that involve the reuse of dredged material from silted channels. This dredged material is deposited in large ponds, and left to consolidate. When its dewatering and strength development is found to be adequate, the consolidate slurry is used as building or filling material for dikes, roads and artificial islands. The consolidation of slurries is a complex process that depends on many physico-chemical aspects. Sediment particles in suspension are interacting and this interaction can lead to time-dependent flocculation and settling rates. Settled flocs will create a very open and fluffy bed that will consolidate over time, exhibiting large strains during the primary consolidation regime. At the same time, a substantial amount of fine particles can remain (unflocculated) in suspension due to Brownian motion. The aim of our research is to link the suspension phase to the consolidating phase in a single model. This model combines a traditional 1D large-strain consolidation model with 1D advection-diffusion model as derived in colloid science in the suspension phase. The model is subsequently tested on various samples from the aforementioned projects.</p

Performance Prediction Models for Flexible Pavements: A State-of-the-art Report

En av aktivitetene for forprosjektet til NordFoU prosjektet - "Pavement Performance Models" var gjennomgang og ekspertvurdering av eksisterende tilstandsutviklingsmodeller. Målet med å gjennomgå modellene var å finne ut styrkene og svakhetene av eksisterende modeller for å danne et grunnlag for en mer grundig vurdering, valg og forbedring av modellene. Undersøkelsen omfattet modeller som er i bruk i de nordiske landene samt noen relevante modeller fra de andre landene (europeiske land og USA). Denne statusrapporten viser resultatet fra gjennomgangen av modellene

Eemdijk full-scale field test programme: sheet pile pullover tests (TProgramme d’essai terrain à taille réelle Eemdijk: essais de déformation et de rupture de murs palplanches)

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

Impact of the Eemdijk full-scale test programme (Impact du programme d'essais à grande échelle Eemdijk)

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

Eemdijk full-scale field test programme: ground dike and sheet pile dike failure test (Programme d’essai terrain à taille réelle Eemdijk: essais de déformation et de rupture pour une digue standard en terre et une digue renforcée avec palplanchesitre)

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

Comparison of new memory surface hardening models for prediction of high cyclic loading (Comparaison de nouveaux modèles de surface de mémoire à durcissement pour la prévision de fortes charges cycliques)

This paper presents an objective comparison between two recent constitutive models employing the concept of the hardening memory surface to predict the high cyclic loading behaviour of granular soils. The hardening memory surface is applied to the well-known Severn-Trent sand and the SANINSAND04 constitutive models. While the addition of the new model surface (the memory surface) leads to enhanced model capabilities, slight differences in the implementation can lead to different model performances and simulations. This paper describes the differences between the two implementations and highlights the most relevant modelling ingredi-ents to predict particular features of the cyclic soil behaviour. This paper will help the reader in selecting the most suitable model and related ingredients for a particular geotechnical application

Developing correlations between the soil fines content and CPT results using neural networks

Knowledge of the fines content is necessary for all soil classification systems and an important factor in the evaluation of soil strength in liquefaction and seismic settlement analysis. This paper presents the application of cone penetration test, CPT data for estimating the soil fines content. The correlation can be used either as a first estimate of fines content (for example in the offshore environment) or to provide statistical information on the variation of fines content within a given area of interest (e.g. for a regional liquefaction study). The paper shows how field and laboratory test data were used with a neural network to correlate the CPT results and the fines content. Data from five site investigation locations across Northern Croatia were utilised. Verification of the approach is performed using field and lab test data from the Veliki vrh landslide.</p