Documents published in Scipedia

• Improving the reliability of sand-steel interface friction angle measurements based on the Ring Shear test

  A. Almukashfi*, S. Larsen, N. Katic

  ISC2024.

  
  

  Abstract

  Understanding the shearing behaviour at soil-structure interfaces is crucial for the analysis and design of geotechnical structures. When significant relative displacements between soil and interface are involved during installation or operation, the ring shear interface testing method, which includes large pre-shearing, is considered reliable for assessing interface resistance. These tests are commonly applied in practical design approaches for driven piles. This research aimed to expand the unified database created by Imperial College London (ICL) and Norwegian Geotechnical Institute (NGI) by incorporating soil test data collected by Geo for North Sea sands with varying grain size distributions. We present an extended database that encompasses soil classification tests and Ring Shear (RS) tests conducted on soilsteel interfaces using Advanced Ring Shear apparatus (Bishop-apparatus-like). This paper introduces a database of interface shearing tests conducted on sandy silty soils with a low content of non-plastic fines. These results facilitate a comprehensive examination of the potential impacts of various factors, including physical soil properties (e.g. grain size distribution), interface characteristics (surface roughness), and testing conditions (normal effective stress). Trends identified within the datasets are synthesized with insights from prior studies to propose interface shear strength parameters suitable for preliminary design employing simple index tests for non-plastic sandy soils. Finally, the paper presents a newly advanced Ring Shear apparatus designed by Wille Geotechnik capable of accommodating static friction. This apparatus incorporates two novel test inserts that can rotate independently at varying radial speeds while being guided simultaneously. The two guided rings can be vertically adjusted, thereby mitigating static friction effects, even in cases of dilatancy.

  Abstract
  Understanding the shearing behaviour at soil-structure interfaces is crucial for the analysis and design of geotechnical structures. When significant relative displacements [...]

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• Gassy Soils ofF the Llobregat Delta: Impact on Geomechanical Characterization

  D. Tarragó*, A. Gens, A. Deu

  ISC2024.

  
  

  Abstract

  The presence of biogenic gas in the soft soils of the Delta del Llobregat at the Port of Barcelona has already been reported by various authors based on geophysical investigations and in-situ tests. As the impact of gas presence on soil behaviour remains uncertain, it is of interest to describe the behaviour of these gassy soils as they may affect future expansions of the Port of Barcelona. Recently, in new geotechnical investigations at the Port of Barcelona, gas emissions have been observed, in several locations in the vicinity of the South breakwater, while performing in situ tests (CPTu and SDMT) or during borehole drilling. Samples were extracted from those boreholes that were subsequently used for laboratory tests. Given the potential impact on geotechnical properties, the results of the investigation were utilized to increase the understanding of gassy soils. Essentially, the focus was on detecting anomalies in geotechnical parameters at the points where gas was detected. These anomalies were also correlated with observations of soil structure obtained from microCT scanning X-ray images of undisturbed samples from the zones where gas was present.

  Abstract
  The presence of biogenic gas in the soft soils of the Delta del Llobregat at the Port of Barcelona has already been reported by various authors based on geophysical investigations [...]

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• Application of Physics-Informed Machine Learning to Geotechnical and Geophysical Site Investigation Data To Define Centimetre-Scale Design Parameters for Offshore Wind

  H. Marin Moreno*, S. Gourvenec, J. Charles

  ISC2024.

  
  

  Abstract

  Offshore wind plays a pivotal role in enhancing Europe's energy security and achieving energy decarbonization goals. However, expediting offshore wind deployment necessitates efficient and economical site investigation surveys. To address this challenge, we introduce a novel approach utilising a deep neural network (DNN) to establish correlations between geotechnical cone penetrometer test (CPT) data and shear wave velocity (𝑉) from seismic CPT. Subsequently, porosity and P-wave velocity (𝑉) are derived using a 𝑉 to bulk density correlation and a dynamic poroelastic model. The DNN is trained and tested on a dataset comprising 5284 instances of public-domain geotechnical CPT test data, including depth, tip resistance, sleeve friction, and 𝑉 from seismic CPT. During testing, the DNN model demonstrates a mean absolute error of 55 m s-1 between predicted and measured 𝑉 values. The uncertainty in 𝑉 predictions is attributed to factors such as (i) limited training data for some soil types such as gravelly sands, (ii) intricate relationship between geotechnical CPT features and seismic properties influencing 𝑉, (iii) the presence of CPT features and 𝑉 combinations that lie well outside the region from most combinations (i.e. outliers), and (iv) CPT features and 𝑉 measurements that are averaged over different depth ranges. The derived porosity and 𝑉

  Abstract
  Offshore wind plays a pivotal role in enhancing Europe's energy security and achieving energy decarbonization goals. However, expediting offshore wind deployment necessitates [...]

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• Small Strain Shear Modulus Derived From Offshore Seismic Reflection Data

  M. Murali, J. Peuchen, L. Sybrandy*, M. Vrolijk, V. Vandeweijer, S. Atkins, S. Carpentier, B. Boullenger

  ISC2024.

  
  

  Abstract

  Small strain shear modulus 𝐺 preferred reference method for 𝐺 is an important parameter for design of foundations of fixed offshore structures. The is the seismic velocity test (SVT) performed as part of a seismic cone penetration test (SCPT). SVTs provide in-situ 𝐺 values for discrete depth sections of SCPTs. This paper focusses on added value achieved by (1) generation of 15 million synthetic 𝐺 (2) a 𝐺 profiles to 50 m depth and zonation map for the IJmuiden Ver Wind Farm Sites Alpha and Beta (offshore Netherlands). The synthetic 𝐺 profiles were derived from a data set of 51 SCPT profiles, 250 CPT profiles and 2D UHR seismic reflection traces along survey track lines spaced at about 70 m. The quality of the SCPT data and UHR seismic reflection data was stateof-the-art (as of 2021). The data process included the use of a (1) multi fidelity data fusion statistical framework and (2) machine learning by a convolutional neural network. The synthetic 𝐺 data were the basis for the 𝐺 zonation map used to enhance an integrated ground model for the wind farm sites. Particularly, the map can be used to quickly identify and constrain areas which are favourable and challenging for design of monopiles and other common foundation types typically considered for offshore wind turbines.

  Abstract
  Small strain shear modulus 𝐺 preferred reference method for 𝐺 is an important parameter for design of foundations of fixed offshore structures. The is the seismic [...]

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• Linking multi-sensor core logger data with in-situ and laboratory testing: A North Sea case study

  C. Bilici, S. Quinteros, S. Smith*, P. Gjerde

  ISC2024.

  
  

  Abstract

  Driven by an increase in the scale of laboratory testing programs, the industry is looking for new methods of soil characterisation and ways to extract more benefit from existing data. In this paper, applications of Multi-Sensor Core Logging (MSCL) to site characterisation projects are discussed, highlighting the potential for providing a fast, quantitative assessment of recovered samples. Sensors of the MSCL include bulk density, P-wave velocity, natural gamma, electrical resistivity and magnetic susceptibility. Natural gamma is shown to be related to higher silt and clay content, acting as a useful parameter for soil classification and quantitative assessment of fines content. A comparison between MSCL and in-situ CPTu data reveals correlations between natural gamma and friction ratio, normalised soil behaviour index, Ic, and net pore pressure response. By collecting MSCL data on all samples at the beginning of a lab program, one can obtain a full overview of the material available for testing, leading to more strategic sample selection and a reduced overall volume of testing. Correlations with MSCL parameters and geotechnical properties can be used to predict continuous profiles, and be extended to in-situ measurements from borehole logging and CPT

  Abstract
  Driven by an increase in the scale of laboratory testing programs, the industry is looking for new methods of soil characterisation and ways to extract more benefit from existing [...]

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• "Development and Preliminary Testing of a New Robotic Tool for Direct Determination of ‘P-Y’ Soil Reaction Curves for Offshore Geotechnical Applications"

  A. El Hajjar, J. Creasey, E. Ibraim, A. Conn, G. Martin, A. Diambra, D. Igoe, D. White

  ISC2024.

  
  

  Abstract

  Monopiles are the most widespread foundation option for offshore wind turbine foundations and their design is largely governed by lateral stability and serviceability. The determination of lateral soil reaction ‘p-y’ curves is a crucial element for their design. At present, ‘p-y’ curves are typically determined through indirect methods, such as correlation from fundamental constitutive parameters, CPT data or extracted through numerical procedures. This paper presents the specification requirements, initial mechanical design, sensor calibration and preliminary testing in a small calibration chamber of a new robotic site investigation tool, the ROBOCONE ‘p-y’ module. This new device can be fitted behind a standard CPT cone. It features a cylindrical module that, after insertion in the ground, can move sideways to closely mimic the kinematic mechanism experienced by a laterally loaded pile element and provide direct “in-situ” characterisation of the ‘p-y’ soil reaction curves. The imposed horizontal translation is substantially different from those of the typical pressuremeter and dilatometer, and analogous to that of a small laterally loaded pile. Movements of the module can be programmed to apply simple monotonic lateral loading conditions and complex stress-controlled or deformation-controlled histories (i.e. cyclic loading, consolidation stages, maintained load). These provide data that can be scaled directly to support advanced cyclic and whole-life design procedures for the lateral ‘p-y’ response of piles.

  Abstract
  Monopiles are the most widespread foundation option for offshore wind turbine foundations and their design is largely governed by lateral stability and serviceability. The [...]

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• Pleistocene and early Holocene palaeo-landscapes of the Dogger Bank South Wind Farm Sites

  M. van Cappelle*, L. Arlott, W. van Kesteren

  ISC2024.

  
  

  Abstract

  A preliminary ground model was prepared for the planned Dogger Bank South Wind Farm Sites in the UK sector of the North Sea. This ground model is based on a geological interpretation of 2D Ultra Ultra High Resolution Seismic (UUHRS) data and geotechnical data. The interpretation results include seismostratigraphic horizons which delineate major soil units. Mapping of these soil units is important for the planning and design of wind turbine locations and inter array cables. Additionally, these horizons reveal (1) multiple generations of buried palaeochannels and (2) evidence for shifting coastlines. The buried palaeochannels have tributaries and contain evidence for the local presence of marshlands (peat beds) beyond the channel margins. These landscapes formed during the Pleistocene and were subsequently flooded when sea level rose as a result of meltwater release from rapidly decaying ice sheets. Locally, thick sequences of early Holocene marine sand deposits show evidence of large-scale clinoforms, which indicate that palaeocoastlines prograded seaward over a distance of up to 20 km during the early Holocene. The top of these clinoforms contain erosion surfaces and gravel lags, indicating sub-aerial exposure of the delta top. This shows that while in general ‘Doggerland’ was rapidly flooded during the early Holocene, there were short periods when the land area expanded.

  Abstract
  A preliminary ground model was prepared for the planned Dogger Bank South Wind Farm Sites in the UK sector of the North Sea. This ground model is based on a geological interpretation [...]

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• Preliminary insights from Foundations for Offshore Wind Turbines (FRONTIErS) Doctoral Network

  L. Prendergast*, K. Gavin, M. Arroyo, G. Eiksund

  ISC2024.

  
  

  Abstract

  The European offshore wind sector has grown rapidly, with significant advances in turbine technologies, in creased sizes, and construction locations further from the shore in deeper waters than ever before. A critical challenge has emerged relating to a growing lack of knowledge surrounding how to design foundations to support these new turbines, with the safety, life-span, cost, and environmental implications coming increasingly into question. To maintain Europe’s stance as a World-leader in offshore wind, Foundations for Offshore Wind Turbines (FRONTIErS) Doctoral Network has been designed to bring together research-intensive universities and major industry stakeholders to train the next generation of graduates with the appropriate skills to tackle the emerging issues presenting as a barrier to continued development of the sector. Eleven Doctoral Candidates have been recruited to tackle significant challenges related to foundation design and performance. Projects focus on topics such as: understanding soil variability, effect of cyclic loading on axial capacity, pile aging, dynamic modelling informed from in-situ testing, time and spatial variation in soil properties, driveability modelling, gravity-base scour effects, multi-directional loading effects, centrifuge testing of cyclic loading response, and dynamic features of wind turbine foundations. This paper presents a preliminary overview of the various PhD projects ongoing as part of this network, which are in the early stages, as well as a summary of training conducted to date.

  Abstract
  The European offshore wind sector has grown rapidly, with significant advances in turbine technologies, in creased sizes, and construction locations further from the shore [...]

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• The importance and influence of the interpretation of geological-geotechnical data on safety of earthen dams

  T. Andrade, J. Fernandes, C. Honório, M. Neto, W. Fonseca, D. Eloi*

  ISC2024.

  
  

  Abstract

  The geological-geotechnical investigation campaign plays a fundamental role in dam safety by providing essential information for assessing and managing the risks associated with these structures. It also allows potential problems to be identified, such as the presence of geological faults or unstable soils. This information allows preventive actions to be taken to avoid catastrophic collapses, through additional containment measures or the revision of the dam's design.The aim of this article is therefore to present the interpretation of the geological-geotechnical data (geophysical tests, Vane Test, triaxial tests, CPTu and mixed borehole) obtained from a robust campaign to investigate the structure of a sediment containment earth dam, raised downstream, located in the state of Minas Gerais. The use of these results meant that the structure could be evaluated with the real conditions of the terrain in different situations such as seismic or hydrostatic overloads, guaranteeing the stability of the structure. In addition, it was possible to determine the soil's capacity to withstand the loads exerted by the dammed water and identify possible points of fragility.From the results obtained in the analysis and interpretation of the structure's sections, it was possible to measure the influence of the discretization of the earth dam massif through the structure's stability analysis, which also made it possible to make a comparison with the analysis sections before and after the geological-geotechnical campaign. In addition, it was possible to discuss the importance and demonstrate that it is essential to carry out comprehensive and up-to-date geological-geotechnical investigation campaigns to ensure that dams are built and operated safely.

  Abstract
  The geological-geotechnical investigation campaign plays a fundamental role in dam safety by providing essential information for assessing and managing the risks associated [...]

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• Post-liquefaction analysis and shear wave assessment by means of instrumented DCP: application to Cephalonia island (Greece) and Petrinja region (Croatia)

  D. Moiriat, T. Luong*, P. Reiffsteck, M. Benz Navarrete, B. Mravlja, N. Belić, P. Rischette, N. Theodoulidis, B. Kordic, S. Markušić

  ISC2024.

  
  

  Abstract

  This work presents both a summary of its implementation at two post-seismic sites: the island of Cephalonia (Greece), and the Petrinja (Croatia) along the Kupa river. In the first case, the main objective was to characterize the surface formations of the Koutavos plio-quaternary sedimentary basin to propose a 1D model of the surface soil column and assess the influence of the variability of these surface formations on the amplification of seismic motion. The second experimental campaign in Croatia was aimed at identifying the soil layers that had been liquefied following the events of 2020, as well as highlighting the different soil models obtained by geophysics or constructed from instrumented variableenergy DCP. For each investigated site, additional geophysical and geotechnical tests were carried out. The data collected with this new technology were compared with those obtained previously with other geophysical methods (MASW), in order to assess the shear wave velocity obtained in particular.

  Abstract
  This work presents both a summary of its implementation at two post-seismic sites: the island of Cephalonia (Greece), and the Petrinja (Croatia) along the Kupa river. In the [...]

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