TU Delft Offshore Geotechnics

How can we maximise the efficiency of offshore hammers? IQIP®'s EQ-Piling hammer is a new, innovative solution for reducing noise and pile fatigue during installation. The hammer uses several hundred tonnes of seawater to dampen the impact force on the pile, prolonging the impact time by up to 15–20 times longer than conventional methods and creating a quieter solution to offshore piling that minimises the risk of pile fatigue. However, how this installation method affects the pile’s geotechnical resistance remains an open question. Tristan Quinten's research uses the centrifuge in TU Delft to answer this question, comparing the installation behaviour and lateral response of monopiles installed with EQ-Piling to monopiles installed with conventional techniques. A key focus of Tristan’s work is the dynamic soil response, particularly the partially drained behaviour of saturated soils during pile installation. His research highlights the importance of rate effects like shear thinning, which significantly influence fluid viscosity under dynamic conditions. Combining this knowledge with a specially designed anvil and a wide array of sensors, the hammer performance and the saturated soil response can be accurately modelled and quantified. As his PhD draws to a close, Tristan is finalising publications on shear thinning in viscous fluids and comparing the installation and lateral loading response of monopiles installed using different methods. Sara Banaei Moghadam's PhD is also following up on this work, looking at field test results from EQ-Piling installations as part of the FRONTIErS - Doctoral Network. Stay tuned for further insights!

 Great discussions at last week's General Assembly in Athens for the CLARION Project! 🛳   The CLARION Project is focussed on developing climate resilient port infrastructure through a consortium of twenty partners from eleven different European countries.   As well as working on the overall project coordination, Kenneth Gavin, Luca Flessati and Ozan Alver are focussing on deep-sea quay walls at the Port of Rotterdam, particularly with regards to their long-term resiliency under sustained loading cycles; tidal and temperature fluctuations; and corrosion-induced degradation (to name but a few!). Much of this work is being carried out through finite element modelling, validating the model outputs using both construction and real-time monitoring data from a highly instrumented quay wall at the port. Extensive CPT tests and geophysical surveys are also being used to give detailed insights into the soil variability around the quay wall, as well as providing inputs to the numerical model. Our other work on quay walls also includes reliability analyses and ground modelling by Na Hao, Federico Montali and Kevin Duffy so plenty of updates to come!

Looking forward to next week’s European Conference on Physical Modelling in Geotechnics (ECPMG)! The conference will be hosted in Deltares, just around the corner from TU Delft.   Alba will be presenting her MSc thesis work on pile penetration in glauconite sands and Tristan will present some of his work on modelling innovative pile driving solutions in the centrifuge. And last but not least, Miguel will give you a fantastic welcome as one of the conference hosts 😊   On Wednesday afternoon, there’ll also be a tour of the TU Delft laboratory and centrifuge so well worth joining! The detailed programme can be found on: https://lnkd.in/em5emWhz

Another successful MSc thesis! Big congratulations to Fenna van Aarle who recently defended her thesis on the Pleistocene sands in the Netherlands and will be presenting her work at EUROENGEO 2024 in October.   The thesis looks at a dense to very dense sand layer known as the Kreftenheye Formation. A river-deposited sand, the Kreftenheye is found throughout most of the western Netherlands and Dutch North Sea sector. In many of the big Dutch cities, like Amsterdam, Rotterdam and the Hague, the formation is overlain by very soft clay and peat deposits and so the Kreftenheye is the primary load-bearing layer for many piled foundations across the country. Conversely, the formation’s high density also creates some challenging installation conditions and there are many examples of piles reaching premature refusal in this layer and getting damaged.   Fenna worked on an extensive dataset collected by the TNO, comprising of CPTs, boreholes and laboratory tests. All of this work is part of a unified effort to improve the integration of geotechnical and geological research, and improving how both onshore and offshore ground models are developed.   Big thanks to the supervisory committee and to those at TNO and TU Delft for their support. 

Huge congratulations to Tessa Berg who just defended her MSc thesis on suction caisson installation!   Suction caissons are an efficient and quiet means of installing offshore foundations and anchors. However, while suction caissons have been extensively researched in sand and clay soils, uncertainty arises when dealing with intermediate/transitional soils due to the influence of (partial) drainage on seepage flow. Another layer of complexity is also added when dealing with layered profiles of drained, undrained and partially drained soils.   To reduce the uncertainty in these conditions, Tessa processed and analysed a database of installation records from offshore wind farms around the world. By analysing how accurately suction caissons could be predicted, clear recommendations could be made for design, reducing the uncertainty associated with installation forecasts in intermediate and layered soils.    Big thanks to DEME Group, SPT Offshore and the supervisory committee for their support.

Check out the Geotechnical Engineering Masters track at TU Delft! The programme prepares students for the increasing challenges of today's world by giving a comprehensive education in the latest analytical, numerical and probabilistic methods as well as giving first-hand experience with geotechnical structures and the underground. More information on the programme can be found via this link: https://lnkd.in/eSsQxjJC

Driveability studies have become a key part of research in the group, particularly in the geo-centrifuge. However, both geometrical and temporal scaling effects can create several uncertainties when it comes to translating real-world problems to the lab-scale. Later today at 17:00 CET we'll be giving a presentation on how to efficiently tackle these uncertainties, with a particular focus on viscous fluids. A worthwhile webinar for anyone interested in learning more about centrifuge testing!

Proud to be acting as project coordinator of the CLARION project, as well as leading the technical work on climate resilient deep-sea quay walls. One PhD and one post-doc will be working on the project, investigating the geotechnial aspects that can affect long-term quay wall resiliency. Looking forward to the research and innovations to come!

New journal publication from the group! Dense to very dense sands have been a persistent challenge throughout the Port of Rotterdam and the North Sea. Not only do these sands pose several installation installation risks, such as premature refusal and pile buckling, but the lack of high-quality load test data in very dense sands creates an uncertainty regarding the response of foundation piles in these soils. The full-scale static load tests at Amaliahaven were performed in geological conditions almost identical to that found in the North Sea, providing interesting perspectives regarding the response of the three different pile types tested. For instance, the three driven closed-ended piles, mobilised post-installation residual base stresses of 10 MPa, subsequently reaching a peak of 30 MPa under axial loading. Both the base and shaft resistances of these piles were comparable to that predicted by the Unified pile design method, bringing more certainty to axial pile design in high cone resistance soils.

Big congratulations to Alba Rodríguez Piedrabuena who passed her MSc thesis defence on Friday with flying colours!   Alba’s research focusses on glauconite, a challenging soil which is being encountered more and more in offshore wind development. Notably, glauconite sand is particularly prone to crushing, transforming the soil from a coarse-grained soil to a fine-grained soil. This change in soil properties can significantly complicate how pile installation is forecasted.   The research was performed in a large calibration chamber (D = 850 mm, H = 960 mm) in the geotechnical lab of Deltares. Using a miniature CPT cone and a model pile instrumented with distributed fibre optic sensors and radial stress sensors, several different loading conditions were measured, including jacked installation, driven installation and cyclical loading. All of these loading conditions had measurable influences on the degree of grain crushing around the pile and CPT. For instance, a photo of the excavated CPT cone after cyclical loading shows a bulb of fine-grained soil around the pile tip and in a thin shear zone along the CPT rod.   Further analysis of the data and additional tests are being performed by PhD Mirko Mento as part of a collaboration with IQIP® to improve driveability predictions in glauconite soils.   The results of Alba’s thesis are available on the TU Delft repository (repository.tudelft.nl).