Publications
140 results found
Morimoto T, O'Sullivan C, Taborda D, 2024, Applying network modelling to determine seepage-induced forces on soil particles, Journal of Geotechnical and Geoenvironmental Engineering, Vol: 150, ISSN: 0733-9410
A pore network model (PNM) idealises the pore space in a soil as voids (network nodes) connected by pore-throats (network edges). Along each edge the fluid flow rate is linearly related to the pressure drop by a hydraulic conductance. This study demonstrates the benefit of using a pore network model (PNM) with an appropriate conductance model in coupled particle-fluid simulations that use the discrete element method (DEM) to simulate the particle phase. PNM simulations and fully-resolved finite volume method Computational Fluid Dynamics (CFD) simulations are used to obtain the fluid-particle interaction force vectors on particles in virtual samples of sand created using DEM simulations. Linearly graded and bidisperse samples are considered. The study assesses the predictive capabilities of existing conductance models considering local flow rates, global permeability and particle-fluid interaction force magnitude for the packings. A new, refined conductance model that is developed upon models available in the literature is also proposed. Taking the fully-resolved CFD data as a benchmark, the PNM-approach is shown to better capture the heterogeneity in the magnitude of the particle-fluid interaction force acting on particles with a similar size than the coarse-grid CFD-DEM approach for all the samples considered. The orientation of particle-fluid interaction force vectors obtained from the fully-resolved CFD is compared with the direction of the force vector predicted by a coarse-grid CFD-DEM and a PNM with the novel conductance model, where the PNM demonstrates a better accuracy. This work enables more realistic and more accurate coupled simulations of phenomena including liquefaction andinternal erosion than has hitherto been possible.
Pedro AMG, Taborda DMG, 2024, Dataset on the behaviour of the Areolas da Estefania formation in Lisbon and its modelling using a state-dependent soil model, Data in Brief, ISSN: 2352-3409
Liu R, Taborda DMG, 2024, The effects of thermal interference on the thermal performance of thermo-active pile groups, Renewable Energy, ISSN: 0960-1481
Möller JK, Taborda DMG, Kontoe S, et al., 2024, A shear history model for capturing the liquefaction resistance of sands at various cyclic stress ratios, Computers and Geotechnics, Vol: 166, Pages: 105940-105940, ISSN: 0266-352X
Various constitutive formulations have been developed over the years to reproduce the cyclic resistance of sands.A common challenge for existing models is the accurate simulation of the cyclic strength of sands for a widerange of initial conditions and different cyclic stress levels when adopting a single calibration. Many liquefactionmodels tend to overpredict the resistance of the soil under large-amplitude loading, while underestimating thestrength at low-amplitude cyclic shearing. This manifests itself in slopes of simulated cyclic resistance ratiocurves (CRR-curves) which are steeper than experimental studies indicate. This paper provides a discussion onthe effects of large-amplitude and low-amplitude cyclic shearing on a granular material based on micromechanical and experimental investigations presented in the literature. A constitutive model with a shear-historythreshold is proposed, which accounts for a shift of the apparent angle of phase transformation under cyclicloading. In addition, a novel expression for a deviatoric fabric tensor is introduced to describe the evolution ofshear-induced fabric anisotropy while a soil is dilating and contracting. Combining these two features in oneformulation within the bounding surface plasticity framework enables an accurate prediction of cyclic strength ofsands under a wide range of cyclic stress ratios.
Morimoto T, O'Sullivan C, Taborda DMG, 2023, Capturing particle-fluid heat transfer in thermo-hydro-mechanical analyses using DEM coupled with a pore network model, Powder Technology, Vol: 429, ISSN: 0032-5910
Numerical simulation of fluid-saturated granular materials subject to temporal or spatial variations in temperature is important for a range of industrial applications and to understand a number of natural processes. Amongst the available fluid-coupling options for Discrete Element Method (DEM), pore network models (PNMs) are attractive as the local heterogeneities in the flow field can be captured with a relatively low computational cost. Any coupled DEM-PNM framework that considers thermal behaviour must account for heat transfer between the solid particles and the fluid phase. This contribution develops a novel expression for the Nusselt number for use in coupled DEM-PNM formulations. Previous studies considering Nusselt number formulations for flow in pipes formed the basis for the proposed model. Finite volume simulations of laminar fluid flow through assemblies of spheres were used to assess the model's efficacy and to calibrate the empirical parameters.
Moller JK, Kontoe S, Taborda D, 2023, Combination of kinematic and inertial loads acting on monopile foundations for offshore wind turbines, Symposium on Energy Geotechnics 2023
Liu R, Taborda D, 2023, An assessment of a simplified methodology for determining the thermal performance of thermo-active piles, Environmental Geotechnics, ISSN: 2051-803X
Ground source energy systems provide low-carbon heating and cooling to buildings, but their efficient deployment requires a reliable estimate of their thermal performance. A simplified methodology is presented to determine the thermal performance of thermo-active piles when heating or cooling loads are specified with either inlet pipe temperatures or imposed heat fluxes. The proposed methodology avoids computationally expensive 3D analyses and the explicit simulation of heat exchanger pipes, relying instead on 2D thermal analyses. When the heating or cooling of a thermo-active pile is assessed by imposing inlet pipe temperatures, the proposed methodology allows the determination of the power of pile per unit length. Conversely, when heating or cooling loads are specified via extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at pile wall, are determined. The proposed methodology has been shown to reproduce accurately the thermal performance of thermo-active piles modelled using 3D analyses where heat exchanger pipes are explicitly simulated, considering different patterns of heating and cooling cycles. The application of the proposed methodology to the case of a real thermo-active pile is demonstrated by comparing its predicted thermal performance with the results of a well-documented field thermal response test.
Ghalandari T, Kia A, Taborda DMG, et al., 2023, Thermal performance optimisation of Pavement Solar Collectors using response surface methodology, Renewable Energy, Vol: 210, Pages: 656-670, ISSN: 0960-1481
Recent studies have highlighted the factors influencing the thermal performance of Pavement Solar Collectors (PSC), such as thermophysical properties of materials, geometrical specifications, and operational conditions. The present study introduces a new approach to investigating the impact of various parameters on the long-term performance of PSCs.The Response Surface Methodology (RSM) is used to optimise the experimental design by reducing the number of simulations resulting from the combination of several design parameters and ample design space. Hence, the proposed PSC system design aims to: i) assess the heat extraction capacity; ii) investigate the ability to diminish the asphalt surface temperature (STR); and iii) determine the reduction in asphalt layers’ rutting potential (RTR), through a coupled RSM and Finite Element (FE) simulation framework.The proposed statistical prediction regression models for heat harvesting capacity, STR, and RTR, adequately represent the experimental data with predicted R2 values above 0.95. The pipe spacing, flow rate, and inlet supply temperature show a high sensitivity to the objective functions, while other parameters display a less sensitive response. Finally, a multi-objective optimisation framework using the NSGA-II is proposed to seek a Pareto front solution in the design space, considering different (or equal) weights for the objective functions.
Ma S, Kontoe S, Taborda D, 2023, On the impact of soil permeability in the numerical simulation of seismically induced liquefaction, 10th European Conference on Numerical Methods in Geotechnical Engineering, Publisher: International Society for Soil Mechanics and Geotechnical Engineering
Moller JK, Kontoe S, Taborda D, et al., 2023, Resonance in offshore wind turbine systems due to seismic loading and extensive soil liquefaction, 10th European Conference on Numerical Methods in Geotechnical Engineering, Publisher: International Society for Soil Mechanics and Geotechnical Engineering
Liu R, Taborda D, 2023, Thermal performance of thermo-active pile groups, 10th European Conference on Numerical Methods in Geotechnical Engineering
Taborda D, Schnaider Bortolotto M, Liu R, 2023, Influence of pipe arrangement and improved thermal conductivity on the response of thermo-active piles, 10th European Conference on Numerical Methods in Geotechnical Engineering
Ferrero J, Ruiz Lopez A, Taborda D, et al., 2023, Applying the observational method to a deep braced excavation using an artificial neural network, 10th European Conference on Numerical Methods in Geotechnical Engineering
Moller JK, Kontoe S, Taborda D, 2023, Numerical investigation of energy dissipation in liquefiable soil deposits, SECED 2023 Conference
Schnaider Bortolotto M, Taborda D, O'Sullivan C, 2023, A systematic approach for conducting and interpreting hydraulic conductivity tests on granular soils under non-isothermal conditions, 8th International Symposium on Deformation Characteristics of Geomaterials
Liu RYW, Taborda DMG, 2023, A simplified methodology for determining the thermal performance of thermo-active piles, Environmental Geotechnics
Ground source energy systems provide low carbon dioxide heating and cooling to buildings, but their efficient deployment requires a reliable estimate of their thermal performance. A simplified methodology is presented to determine the thermal performance of thermo-active piles when heating or cooling loads are specified with either inlet pipe temperatures or imposed heat fluxes. The proposed methodology avoids computationally expensive three-dimensional (3D) analyses and the explicit simulation of heat exchanger pipes, relying instead on two-dimensional thermal analyses. When the heating or cooling of a thermo-active pile is assessed by imposing inlet pipe temperatures, the proposed methodology allows the determination of the power of the pile per unit length. Conversely, when heating or cooling loads are specified through extracted or injected heat fluxes, the inlet and outlet fluid temperatures, as well as average temperatures at the pile wall, are determined. The proposed methodology has been shown to reproduce accurately the thermal performance of thermo-active piles modelled using 3D analyses where heat exchanger pipes are explicitly simulated, considering different patterns of heating and cooling cycles. The application of the proposed methodology to the case of a real thermo-active pile is demonstrated by comparing its predicted thermal performance with the results of a well-documented field thermal response test.
Morimoto T, Zhao B, Taborda D, et al., 2022, Critical appraisal of pore network models to simulate fluid flow through assemblies of spherical particles, Computers and Geotechnics, Vol: 150, Pages: 1-20, ISSN: 0266-352X
Coupled numerical models considering fluid flow and particle movement enable fundamental analyses of a variety of phenomena in geomechanics including seepage-induced instabilities. Amongst the various CFD (Computational Fluid Dynamics)-DEM (Discrete Element Method) coupled frameworks which have been proposed, Pore Network Models (PNMs) have the potential to simulate fluid flow in granular materials accurately with a low computational cost to enable simulations on Representative Volume Elements (RVEs). However, the current models of the local conductance between the connected pores are very simple, limiting the accuracy of PNMs. This study develops novel local conductance models by detailed analysisof existing analytical studies of fluid flow through different 3D lattice packings of uniform spheres. The performance of these new models relative to existing, simpler models is demonstrated using CFD simulations in which the flow in the pore space of random assemblies of polydisperse spheres is accurately resolved. The analyses show that the new models proposed here can more accurately predict the local and global permeabilities of specimens with a wide range of void ratios and polydispersities. These models do not require any optimisation via merging pores so that they can efficiently simulate systems with an evolving pore space topology.
Sailer E, Taborda D, Zdravkovic L, et al., 2022, A novel method for designing thermo-active retaining walls using two dimensional analyses, Proceedings of the Institution of Civil Engineers: Geotechnical Engineering, Vol: 175, Pages: 289-310, ISSN: 1353-2618
Thermo-active retaining walls are geotechnical structures employed as heat exchangers to provide low carbon dioxide heating and cooling to buildings. To assess the thermo-mechanical response of such structures, finite-element (FE) analyses are typically carried out. Due to the presence of heat exchanger pipes, the temperature distribution along the width of the wall is not uniform, implying that these problems are three-dimensional (3D) in nature. However, performing 3D FE analyses including elements to model the heat exchanger pipes to simulate the advective conductive heat transfer as well as thermo-hydro-mechanical coupling to reproduce the non-isothermal soil response accurately requires considerable computational effort. In this work, a novel approach to simulate thermo-active walls in 2D analyses was developed, which requires the sole use of thermal boundary conditions. This approach was found to reproduce average wall behaviour computed in 3D to a high degree of accuracy for numerous wall geometries, a wide range of thermal properties of soil and concrete, and different thermal boundary conditions along the exposed face of the wall. In addition, out-of-plane effects recorded in 3D analyses were assessed and an accurate simplified procedure to account for these when performing 2D analyses was developed.
Loveridge F, Schellart A, Rees S, et al., 2022, The potential for heat recovery and thermal energy storage in the UK using buried infrastructure, Proceedings of the Institution of Civil Engineers - Smart Infrastructure and Construction, Vol: 175, Pages: 10-26
Dispersed space heating alone accounts for 40% of UK energy use and 20% of CO2 emissions. Tackling heating and building cooling demands is therefore critical to achieve net zero ambitions in the UK. The most energy efficient way to decarbonise heating and cooling is through the use of ground source heat pumps and district heating technology. However, capital costs are often high, sometimes prohibitively so. To reduce investment costs, it is proposed to use buried infrastructure as sources and stores of thermal energy. Barriers to this innovative approach include lack of knowledge about the actual net amount of recoverable energy, and impacts on the primary function of any buried infrastructure, as well as the need for new investment and governance strategies integrated across the energy and infrastructure sectors. Additional opportunities from thermal utilisation in buried infrastructure include the potential mitigation of damaging biological and/or chemical processes that may occur. This paper presents a first assessment of the scale of the opportunity for thermal energy recovery and storage linked to new and existing buried infrastructure, along with strategic measures to help reduce barriers and start the UK on the journey to achieving of its infrastructure energy potential.
Taborda D, Goncalves Pedro A, Pirrone A, 2022, A state parameter-dependent constitutive model for sands based on the Mohr-Coulomb failure criterion, Computers and Geotechnics, Vol: 148, ISSN: 0266-352X
Experimental data have demonstrated that a strong relationship exists between the state parameter and the peak strength and dilatancy characteristics of sands. This paper proposes a way of reproducing this behaviour using a modified Mohr-Coulomb failure criterion, which retains its simplicity while improving substantially its modelling capabilities. The formulated constitutive model is calibrated for Nevada sand following a well-defined procedure and used in the prediction of four centrifuge tests investigating the behaviour of axially loaded footings. It is shown that the proposed model reproduces well both the element tests and the morecomplex footing problems, demonstrating its usefulness for engineering practice. Moreover, a simplified version which does not require the definition of the Critical State Line is proposed for situations when this aspect of soil behaviour cannot be determined with confidence. It is shown that such simplification results in only slightly less accurate predictions than the full version of the model, while simulating aspects of soil response that cannot be reproduced using constant values for strength and dilatancy parameters.
Liu R, Taborda D, Fisher A, et al., 2021, Development of a practical heat of hydration model for concrete curing for geotechnical applications, Geotechnical Research, Vol: 9, ISSN: 2052-6156
Thermal integrity profiling (TIP) is a common non-destructive technique to evaluate the quality of construction of piles by analysing the temperature fields due to heat of hydration from freshly cast concrete piles. For this process to be accurate, a reliable concrete heat of hydration model is required. This paper proposes a practical and simple to calibrate four parameter model for the prediction of concrete heat of hydration. This model has been shown to be able to reproduce the evolution of heat of hydration measured in laboratory tests, as well as field measurements of temperature within curing concrete piles, as part of a thermal integrity profiling (TIP) operation performed at a site in London. With the simplicity of the model and the small number of model parameters involved, this model can be easily and quickly calibrated, enabling quick predictions of expected temperatures for subsequent casts using the same concrete mix.
Morimoto T, O'Sullivan C, Taborda D, 2021, Exploiting DEM to Link Thermal Conduction and Elastic Stiffness in Granular Materials, Journal of Engineering Mechanics, Vol: 148, ISSN: 0733-9399
Estimating the effective thermal conductivity (ETC) of granular materials is important in various engineering disciplines. The ETC of a granular material is not unique, rather it depends upon the material's packing characteristics, i.e. porosity and coordination number. Directly measuring the ETC of granular materials with a particular packing density and subjected to specific stress conditions is experimentally challenging. There is a need to develop reliable, indirect experimental methods to measure the ETC of granular materials. Here we explore the possibility of linking the ETC of granular materials to their elastic moduli.This study used a thermal pipe network model implemented in a Discrete Element Method (DEM) code to generate ETC data for ideal, virtual two-phase granular samples with stagnant pore fluid. Parametric studies considered the sensitivity of the ETC to the sample packing. Data from small deformation probes were used to explore links between the samples' elastic moduli and their ETCs. The results provide a theoretical background for the development of an indirect experimental method to predict the ETC or trends in the variation in the ETC by considering stiffness data which are relatively straightforward to acquire. The study shows how DEM can be used as a sophisticated thought experiment to explore novel ideas for developing experimental procedures.
Zdravković L, Potts DM, Taborda DMG, 2021, Integrating laboratory and field testing into advanced geotechnical design, Geomechanics for Energy and the Environment, Vol: 27, Pages: 1-21, ISSN: 2352-3808
Contemporary geotechnical design often requires the use of advanced numerical analysis, if it is to take account of the complex nature of many geotechnical problems. One crucial aspect of such analyses is the realistic representation of the facets of soil behaviour that are dominant in any given problem, which in turn requires a careful selection of an appropriate constitutive model and derivation of model parameters from the available, and often disparate, experimental data. This paper uses the authors’ experience of advanced numerical analysis and constitutive modelling to emphasise the importance of close integration of the process involved with interpreting experimental data with the process of selecting and calibrating advanced constitutive models, in successfully predicting the response of geotechnical structures.
Schnaider Bortolotto M, Taborda DMG, O'Sullivan C, 2021, Thermal effects on the hydraulic conductivity of a granular geomaterial, 20th International Conference on Soil Mechanics and Geotechnical Engineering 2022, Publisher: 2022 Australian Geomechanics Society, Pages: 5017-5022
Geotechnical challenges arising from thermal loading are associated with many engineering applications such as ground source energy systems (5℃-40℃) and nuclear waste disposal (in excess of 100℃). The effects of temperature on soils have been the subject of limited research, particularly in terms of the fundamental characterisation of the non-isothermal behaviour of granular geomaterials. This study describes challenges associated with determining the hydraulic conductivity (k_ℎ) of such materials at different temperatures using a bespoke temperature-controlled triaxial apparatus. A methodology is proposed for interpreting thermo-hydro-mechanical (THM) tests on isotropically consolidated specimens and is applied to data obtained for a uniform sand. It is shown that the intrinsic head losses of the system need to be minimised in order to obtain reliable measurements; this requires a detailed calibration procedure. The developed approach is used to determine the hydraulic conductivity at ambient temperature and at 40℃, showing that the increase in k_ℎ with temperature is mostly due to the reduction in the viscosity of water. A detailed analysis of the volumetric response of the sample during heating is also carried out.
Gawecka K, Cui W, Taborda D, et al., 2021, Predictive modelling of thermo-active tunnels in London Clay, Geotechnique: international journal of soil mechanics, Vol: 71, Pages: 735-748, ISSN: 0016-8505
Thermo-active structures are underground facilities which enable the exchange of thermal energy between the ground and the overlying buildings, thus providing renewable means of space heating and cooling. Although this technology is becoming increasingly popular, the behaviour of geotechnical structures under additional thermal loading is still not fully understood. This paper focuses on the use of underground tunnels as thermo-active structures and explains their behaviour through a series of finite element analyses based on an existing case study of isothermal tunnels in London Clay. The bespoke finite element codeI CFEP is adopted which is capable of simulating the fully coupled thermo-hydro-mechanical behaviour of porous materials. The complex coupled interactions between the tunnel and the surrounding soil are explored bycomparing results from selected types of coupledand uncoupled simulations. It is demonstratedthat: (1) the thermally-induceddeformation of the tunnel and the ground are more critical design aspects than the thermally-induced forces in the tunnel lining, and (2) the modelling approach in terms of the type of analysis, as well as the assumed permeability of the tunnel lining, have a significant effect on the computed tunnel response and,hence, must be chosen carefully
Sailer E, Taborda DMG, Zdravkovic L, et al., 2021, Thermo-hydro-mechanical interactions in porous media: implications on thermo-active retaining walls, Computers and Geotechnics, Vol: 135, Pages: 1-16, ISSN: 0266-352X
Thermo-active structures exchange heat with the ground to provide thermal energy to buildings. Consequently, the ground is subjected to changes in temperature, inducing thermo-hydro-mechanical (THM) interactions within the soil. To provide insights into the origin and manifestations of the main mechanisms taking place in complex fully THM-coupled finite element (FE) analyses, simple, one-dimensional problems are firstly analysed in this paper and compared to analytical expressions developed for determining thermally-induced excess pore water pressures in undrained problems with different displacement restraints. Subsequently, various dimensionless parameters are established to evaluate the impact of varying ground properties on the observed THM interactions and their evolution with time. Finally, the findings from simple one-dimensional problems are verified in the context of THM modelling of thermo-active retaining walls, where the structural response of walls is shown to be highly transient and influenced by different phenomena prevailing over different periods involving thermal expansion of soils, volumetric deformations due to pore water generation and dissipation, and interactions with mechanical boundary conditions. The results also highlight the importance of performing fully coupled THM analyses and of a correct estimation of the hydraulic and thermal properties to guarantee a safe design of thermo-active structures.
Morimoto T, O'Sullivan C, Taborda D, 2021, Analytical and DEM studies of thermal stress in granular materials, Powders and Grains 2021, Publisher: EDP Sciences, Pages: 1-4, ISSN: 2100-014X
The ability to predict thermal-induced stresses in granular materials is of practical importance across a range of disciplines ranging from process engineering to geotechnical engineering. This study presents an analytical formula to predict thermal-induced stress increments in mono-disperse granular materials subject to an initial isotropic stress state. A complementary series of DEM simulations were carried out to explore the applicability of the proposed analytical formula. The comparative analysis showed that the proposed expression can accurately predict stress changes in packings where there are negligible particle displacements as a consequence of the thermal loading (e.g. regular packings and medium/dense random packings); however large errors were observed in loose samples with a random packing.
Zdravkovic L, Cui W, Gawecka K, et al., 2021, Numerical Modelling of Thermo-Active Piles, PIling 2020
Lopez AR, Tsiampousi A, Taborda DMG, et al., 2021, Numerical investigation into time-dependent effects on short-term tunnelling-induced ground response in London Clay, 10th International Symposium on Geotechnical Aspects of Underground Construction in Soft Ground (IS-Cambridge), Publisher: ROUTLEDGE, Pages: 597-604
- Author Web Link
- Cite
- Citations: 1
Moller JK, Kontoe S, Taborda D, et al., 2020, Maximum depth of liquefaction based on fully-coupled time domain site response analysis, 4th International Symposium on Frontiers in Offshore Geotechnics
Soil susceptibility to liquefaction is most commonly assessed in engineering practice using empirical correlations of in-situ tests with observed surface manifestations of liquefaction in case histories. This simplified design method further incorporates a correction factor for varying overburden pressure, derived from laboratory data, and provides expressions for earthquake induced shear stresses based on simplified one-dimensional equivalent linear site response analysis. The resulting factor of safety against liquefaction is only valid for the depths represented in the laboratory test data, case history data and the site response analyses, i.e. a maximum depth of 20 m. In order to evaluate the susceptibility of soils at larger depths, one-dimensional time-domain site response analyses are carried out, showing the extent of the liquefied zone for sand deposits of different depths. This study evaluates the performance of a bounding surface plasticity model in comparison with a nonlinear elastic cyclic model regarding the amplification and damping of certain frequency contents of shear waves propagating through deep soil deposits. These findings are of particular relevance for applications in offshore geotechnical engineering, where liquefaction in large depths can have severe effects on the load-carrying capacity of deep pile foundations.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.