Many embankments of the Dutch railroad network are over a hundred years old and were constructed on very soft clay and peat layers. The weight of the trains and the use of the railway infrastructure have increased over time. A recent assessment of the stability of existing infrastructure revealed that the railway embankment is demonstrably not in compliance with the required standards in several locations. However, although considerable deformations exist in some cases, most of these embankments have remained stable under current use. This may indicate that several aspects of the train loading characteristics in relation to the foundation soil strength are not fully understood in the context of railway embankment stability. To better understand the effect of train loading and increased use of railroads on the soil strength, a geocentrifuge test program was executed through the GEOLAB initiative. During this study a series of centrifuge tests were performed of a railroad system composed of a sandy embankment underlain by a soft clay foundation, aiming to provide a better understanding of the potential effects of train loading characteristics and the increased use of railroads on the foundation soil strength. The models were tested in a geotechnical centrifuge at a gravitational acceleration field of 20g and included reference static monotonic tests to failure and tests modelling different train loading conditions, including different loading frequencies and amplitudes. This paper presents the design of the experimental setup, a description of the behavior’s observed during the execution of the tests and preliminary results and observations of the project SURE performed as part of the transnational access initiative by GEOLAB. Further presentation and analysis of the results will be presented in a future companion article. ... Read more

The installation method of offshore monopiles can significantly influence their lateral capacity and stiffness, which are critical parameters in foundation design for offshore wind turbines. Vibratory driving has emerged as a promising alternative to traditional impact driving, offering potential reductions in noise emissions and installation time. However, its effect on the lateral response of the driven pile remains insufficiently understood. This work presents the development and first use of a combined in-flight vibratory installation and cyclic lateral loading apparatus within TU Delft’s geotechnical centrifuge. The system enables the vibratory installation of model piles at prototype stress levels, followed by monotonic or cyclic lateral loading without sample repositioning. Two initial cyclic tests are reported: one with a pile manually inserted at 1g, and one vibro-driven in-flight. The results provide preliminary insight into the influence of the installation method on the lateral response of the pile: the vibratory driven pile displays a stiffer response as well as more capacity than the wished-in place pile. The apparatus offers a unique platform for future studies, including the planned addition of impact-driven tests and extended cyclic loading tests. This work lays the foundation for more comprehensive investigations into the link between offshore pile installation technique and in-service lateral performance. ... Read more

Critical Infrastructure (CI) plays a fundamental role in supporting economic activity, enhancing quality of life, and safeguarding communities. However, infrastructure systems, whether they are roads, bridges, utilities, or communication networks, are increasingly being confronted with numerous challenges. These challenges compel CI owners and policymakers to adopt new strategies and solutions to reach desired levels of reliability. From ageing and climate-induced hazards to the necessity for sustainability and accessibility, infrastructure must evolve to meet societal needs while balancing economic, environmental, and technological pressures. GEOLAB emerged in 2021 from the European Large Geotechnical Institutes Platform (ELGIP) under the lead of Deltares to integrate top European research facilities into a one-stop-shop for performing excellent physical modelling research and innovation in the area of CI. The GEOLAB Research Infrastructure (RI) comprises 12 unique facilities in Europe for studying ground response and its interaction with structural components and the environment. It includes six Geo-Centrifuges of different sizes and capabilities, a Geo-Model Container, a Static Liquefaction Tank, a Geotechnical Test Pit, a Large-scale Triaxial Apparatus, a Railway Track Simulator and a set of five Field Test Sites. They represent the leading geotechnical experimental facilities available in Europe today. The GEOLAB RI realized 44 projects supporting research and innovation that address CI challenges. New technologies were implemented in these projects to increase the set-up and observation of the experiments. Beyond its overarching aim, GEOLAB’s essential goal is to assess whether the experimental and numerical tools available will be able to address societal needs and demands of CI resilience in the future. The need of new or alternative methodologies, knowledge and development of the RI is explored. By doing so, GEOLAB evolved into an advanced community with an impact in critical areas such as sustainable development, digital transformation and scientific excellence. ... Read more

Monopiles, commonly adopted as substructures in wind farms, are typically installed via impact driving. The heavy selfweight of the monopile and the impact hammer required for installation increase the risk of pile runs. Pile runs have been reported in cases of stronger soils overlying weaker layers, as well as in heterogeneous soil deposits (e.g., chalk). However, recent experience from the field showed that none of the reasons above could satisfactorily explain the observed pile run in the presence of silty or fine sandy soils, typically referred to as transitional soils. Conversely, back analysis of the driving data revealed a high dependency of the Soil Resistance to Driving (SRD) on the pile penetration rate. This behaviour is believed to be linked to the drainage response of the transitional soils and pile driving parameters, including impact energy and blow rate. The latter may combine so that Excess Pore Water Pressures (EPWP), without dissipating sufficiently, accumulate to the extent a pile run can be triggered, due to the reduction of the available shear strength of the soil. To investigate this hypothesis, an experimental testing program was conducted using the geotechnical centrifuge. The tests, involving a model monopile driven in a natural silt sample, aimed at demonstrating that the soil conditions believed to contribute to a pile run can be replicated in the centrifuge. Preliminary results of a testing sequence of single blows suggest that the EPWP accumulated around the pile between consecutive blows is responsible for a reduction of the unit shaft resistance. ... Read more

This article presents results of an experimental campaign on a scaled vibro-driver in sand conducted in TU Delft’s geo-centrifuge as part of the GEOLAB funded project FoundEx. The aim of this experimental campaign is to explore the different parameters governing the vibro-driveability of a monopile within sand to improve the understanding of the phenomena at play, quantify the influence of driving parameters, and refine their selection to open new perspectives for the industry. After explaining the governing principles of vibro-drivers and the design of the miniature vibro-driver, the results of vibro-driving in dry dense sand under 50g for different vibrating frequencies are presented. These results are then analysed to quantify the relation between the vibratory frequency and the pile penetration, as well as its penetration rate. ... Read more