Nottingham Centre for Geomechanics (NCG)

Last week we had the pleasure of welcoming back our former researcher Thejesh Kumar Garala to Nottingham Centre for Geomechanics (NCG), to present some of his work at Fugro regarding the development of guidelines for site-specific geotechnical analyses of off-shore jack-ups. In this excellent presentation, Thejesh detailed some of the practical and theoretical challenges that are not currently covered by existing standards. New procedures were demonstrated for gaining a better understanding of ground conditions, accounting for cyclic loading, soil anisotropy, and partial drainage behaviour under various loading conditions. Any opportunity to reconnect with former colleagues is valuable, especially when they can give academic institutions an insight into the progress and interests of industry! We also would like to wish Thejesh all the best in his new role as Assistant Professor at Indian Institute of Technology, Madras. Congratulations!

📣 Congratulations to NCG's Dr Kunkun Cheng who successfully defended his PhD thesis "Centrifuge tests of monopile foundations under cyclic lateral loading" at University of Nottingham this week. The aim of this project is to achieve a better understanding of the long-term behaviour of offshore wind turbine monopile foundations, and focusses on the response of monopiles subjected to a large number of load cycles in sand. The long-term effects of cyclic loading characteristics on pile-soil stiffness and pile head displacement are assessed. Kunkun was supervised by Prof Alec Marshall, Dr Charles Heron, and Dr Luke J. Prendergast at Nottingham Centre for Geomechanics (NCG). Thanks to internal assessor Dr Angus Pettey and external examiner Dr Paul Shepley for examining the work! #monopiles #centrifuge #modelling #geotechnics #geomechanics

Congratulations to current PhD student Chuanjin Tang and recently graduated PhD student Yalin Yu for presenting their work on tunnel-building interaction analysis at the 11th International Symposium of Geotechnical Aspects of Underground Construction in Soft Ground (IS-Macau 2024). They are joined in the image by our good friends and collaborators, Daniela Boldini and Andrea Franza. Well done to both of you! You are great ambassadors for the Nottingham Centre for Geomechanics (NCG)!

NCG's Professor Glenn McDowell was presented with the British Geotechnical Association Medal 2023 on 12 June 2024 at the Institution of Civil Engineers (ICE), Westminster, London. The prestigious medal was awarded for his paper entitled “Particle-scale simulations of the compression and shearing of kaolin clay” published in Géotechnique and co-authored with Dr John de Bono (formerly NCG). The medal was presented at the Annual British Geotechnical Association Conference in front of an audience of hundreds of delegates, including many eminent geotechnical engineers, attending in-person and online around the World. The paper is available here: https://lnkd.in/eM3DNDET

#JustPublished "A two-stage method to estimate the embedded length of foundation piles using FRF-based model updating" in Mechanical Systems and Signal Processing 219 2024 Paper by Andreas Ioakim, PhD Researcher; and Dr Luke J. Prendergast, Associate Professor, at Nottingham Centre for Geomechanics (NCG) - In this paper, a Frequency Response Function (FRF)-based model updating method is developed that can estimate the embedded length of foundation piles, in addition to the mobilized soil mass and stiffness, when a lateral impact load is applied. Knowledge of the embedded length may not be readily available and is very important for accurately creating damage models or digital twins of structures with piled foundations. - The method uses information from the 1st mode of vibration to estimate the mobilised soil mass and stiffness, and subsequently uses information from the 2nd mode of vibration to estimate the embedded length, from a single lateral impact load. - To appraise the approach, impact tests are numerically simulated on a number of ‘piles’ (numerical spring-beam systems) with varying length/diameter (L/D) ratios to derive FRFs, whereby the models have known length and dynamic properties. These FRFs are then used as targets in the model updating approach, which iteratively varies the properties of a numerical model of a pile to obtain a match in the FRF data, and subsequently estimates the mobilised stiffness, mass, and embedded length. - The results of the analyses illustrate that by minimising the difference in the first and second FRF peaks between the target and estimated FRFs, the method can accurately estimate the mass, stiffness and embedded length properties of the test ‘piles’ simulated in this paper. Paper available #OpenAccess: https://lnkd.in/etQ6Husv #SoilStiffness #ModelUpdating #Dynamics #Winkler #SoilStructureInteraction #ParameterEstimation #DigitalTwins

#JustPublished "A method to quantify the beneficial effect of scour protection on lateral behaviour of monopiles for offshore wind turbines" in Ocean Engineering 307 2024 Paper by Dr Qiang Li, Prof Kenneth Gavin, and Dr Amin Askarinejad of Delft University of Technology, Prof Xinquan Wang of Hangzhou City University, and Dr Luke J. Prendergast of Nottingham Centre for Geomechanics (NCG) - The contribution of scour protection to lateral resistance of monopiles in sand is investigated in this paper using centrifuge tests and finite element analyses. - Multiple scour protection widths and thicknesses are modelled around a monopile, to identify the most effective scour protection properties at mitigating lateral displacements. - Two methods for modelling scour protection effects (one using material, the other using direct overburden pressure) are compared. The lateral response of monopiles with different slenderness ratios under various scour protection widths and overburden pressures are simulated. - Results suggest that pile lateral displacements reduce by up to 41% when scour protection with width 2D (D, pile diameter) and applied overburden pressure of 30 kPa is used, compared to no scour protection, for a given test case. - A method to modify design approaches to consider the beneficial contribution of scour protection on pile lateral behaviour using an envelope diagram is proposed, which provides relationships for scour protection properties and various monopile slenderness ratios. Paper available: https://lnkd.in/eSvNNzXt #Monopiles #Scour #OffshoreWind #LateralLoading #CentrifugeTests #FEM 

We are pleased to announce that NCG’s Prof. Glenn McDowell has been awarded the British Geotechnical Association Medal for 2023 for his paper entitled “Particle-scale simulations of the compression and shearing of kaolin clay” published in Géotechnique with co-author Dr John de Bono. More Info: https://lnkd.in/eh5aUAG Professor Glenn McDowell says: “This is a huge honour. We won the BGA Medal back in 2018 for work which explained much of the observed mechanical behaviour of sands with models based on particle crushing. However, explaining the micro mechanical origins of macro clay behaviour has been much more difficult. Basically the observed behaviour of sand and clay are very similar, albeit at different stress levels and it has been a mystery for many decades as to why this is so, when the materials could not be more different. Clays form platelets which are very small (typically about a micron in diameter) and very thin. These platelets are charged and can stick together in different ways. So by looking at the formation and 'breakage' of clay 'stacks' or macro particles, we have been able to explain much of what we observe and call the 'critical state framework' for clay. Explaining why clay behaves in many ways like crushable sand has been one of the holy grails of soil mechanics so it’s been a privilege to make a contribution in this area and I’m delighted that the British Geotechnical Association has recognised the importance of this work with the BGA Medal for 2023.” The medal will be presented at the Institution of Civil Engineers (ICE) in London on 12th June. The images show isotropic normal compression results and a virtual sample after compression to 1MPa. The two colours of the sample indicate the different faces of kaolinite particles. 

📣 PhD Opportunity at Nottingham Centre for Geomechanics (NCG)📣 Project description: Construction of large and deep shafts in urban areas is necessary for various construction activities, such as tunnel construction where shafts serve as integral components of the tunnel construction and often operational phases. As tunnels are constructed ever deeper due to the congestion of underground space, so must the shafts be sunk to deeper levels. Shafts may suffer stability issues as a result of various factors, which can, in the worst case, result in catastrophic failures, or more typically in ground movements. These ground movements, which can have serious and detrimental effects on nearby existing structures and infrastructure in urban areas, are the topic of this PhD project. This PhD project aims to: - Study experimentally using reduced scale physical models in the Nottingham Centre for Geomechanics 2m diameter geotechnical centrifuge, the processes involved with deep shaft construction and how aspects of shaft construction and/or stability affect resulting ground displacements. - Using a novel hybrid physical-numerical modelling approach pioneered in Nottingham for tunnel-structure interaction, experimentally quantify the effects that ground displacements have on nearby buildings. - Integrate project outcomes into accessible design methods/charts for immediate use by industry. The PhD student will work with Professor Alec Marshall and Dr Charles Heron of the Nottingham Centre for Geomechanics (NCG) alongside Dr Benoit Jones from INBYE Engineering. The PhD studentship will be partly funded by the British Tunnelling Society. The successful candidate will benefit from the direct involvement from industry through Dr Jones and representatives of the BTS – ensuring that this PhD project is directly relevant to today's industry needs and ensure that project outcomes have an immediate impact on industry practices.  How to apply: Please contact Prof Alec Marshall (alec.marshall@nottingham.ac.uk ) before submitting an online application. Please send a cover letter and a copy of your CV with your up to date relevant experience. Apply here: https://lnkd.in/eUA6w4CF Due to funding restrictions this position is only available for Home candidates. International students may be considered but should contact Prof Alec Marshall to discuss. #phd #opportunity #project #design #infrastructure

#JustPublished "Performance and limits of a geotechnical centrifuge: DEM‑LBM simulations of saturated granular column collapse" in Granular Matter 26(32) 2024 Paper by William Webb and Dr Barbara Turnbull at University of Nottingham, with Dr Alessandro Leonardi at The University of Sheffield - This study examines the influence of centrifugal and Coriolis accelerations on the dynamics of experimental particle-laden flows inside a geotechnical centrifuge. - The Discrete Element Method (DEM) and the Lattice-Boltzmann Method (LBM) are coupled to simulate the collapse behaviour of a just-saturated granular column within a rotating reference frame, initially validating the model with data from physical experiments. - The analysis uncovers how centrifugal and Coriolis accelerations impact flow structure and mobility, offering actionable insights to mitigate their effects on flow dynamics. - By introducing an interstitial pore fluid and considering multiple variables that influence flow behaviour across a wide parameter space, this work enhances the understanding of granular flow dynamics in geotechnical centrifuge models. Paper available: https://lnkd.in/ePpp4Xte #DEM #LBM #GranularCollapse #JustSaturated #CentrifugeModelling

#JustPublished "A data-driven approach for scour detection around monopile-supported offshore wind turbines using Naive Bayes classification" in Marine Structures 95 2024 Paper by Dr Satish J, Dr Ramin Ghiasi, and Dr Abdollah Malekjafarian at University College Dublin, Dr Soroosh Jalilvand, PhD. at Gavin & Doherty Geosolutions (GDG), and Dr Luke J. Prendergast at University of Nottingham - This paper proposes a novel data-driven framework for scour detection around offshore wind turbines (OWTs), where damage features are derived from wind and wave-induced acceleration signals collected along the tower - A numerical model of the NREL 5 MW wind turbine, which considers aerodynamic and hydrodynamic loading with soil-structure interaction (SSI) and servodynamics, is developed - A data segmentation process is initially performed on the collected data, which is followed by a feature selection scheme based on the analysis-of-variance (ANOVA) algorithm, to eliminate irrelevant characteristics from the time domain feature set of responses - In the real-time classification, a prediction of the scour depth affecting the structure is performed using a new dataset simulated from unseen load cases and scour conditions of the OWT - The results show that the model trained in the offline stage can predict the scour depth in the real-time monitoring stage with performance measures over approximately 94% Paper available: https://lnkd.in/eQhmQJbk #OffshoreWindTurbines #Monopile #Scour #FeatureExtraction