100 results on '"Tsiampousi, Aikaterini"'
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2. The influence of tunnel joints on the present-day condition of a grey cast iron tunnel
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Ruiz López, Agustín, Tsiampousi, Aikaterini, Standing, Jamie R., and Potts, David M.
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- 2023
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3. Numerical characterisation of the rotational behaviour of grey cast iron tunnel joints
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Ruiz López, Agustín, Tsiampousi, Aikaterini, Standing, Jamie R., and Potts, David M.
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- 2023
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4. Numerical investigation of the performance of engineered barriers in controlling stormwater runoff
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Petalas, Alexandros L., Tsiampousi, Aikaterini, Zdravkovic, Lidija, and Potts, David M.
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- 2022
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5. Coupled hydro-mechanical modelling of soil-vegetation-atmosphere interaction in natural clay slopes
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Pedone, Giuseppe, Tsiampousi, Aikaterini, Cotecchia, Federica, and Zdravkovic, Lidija
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Slopes (Physical geography) -- Environmental aspects ,Soils -- Environmental aspects ,Landslides -- Models ,Clay -- Environmental aspects ,Earth sciences - Abstract
Soil-vegetation-atmosphere interaction has long been known to induce significant pore pressure variations at shallow depths and associated superficial slope movements. Recent findings suggest that the effect of this interaction may also extend to large depths in natural clay slopes. Multiple examples of weather-induced deep landslide mechanisms can be found in the Southern Apennines (Italy), where slopes are often formed of fissured clays. The relationship between the activity of these landslides and the hydro-mechanical processes due to soil-vegetation- atmosphere interaction was investigated herein by means of a two-dimensional coupled hydro-mechanical finite element analysis. A constitutive model capable of simulating the behaviour of highly overconsolidated clays, in both saturated and unsaturated states, was adopted in the analysis, in conjunction with a boundary condition capable of reproducing the combined effects of rainfall infiltration, evapo-transpiration, and run-off. The results of the analysis corroborate the connection between weather conditions, pore pressure variations, and slope movements in natural clay slopes. The importance of adequately reproducing the geological history of a natural slope to define its current state is also demonstrated. Key words: numerical modelling, finite element analysis, soil-vegetation- atmosphere interaction, natural slopes, landslides, fissured clays. L'interaction sol-vegetation-atmosphere est connue depuis longtemps pour induire d'importantes variations de pression interstitielle a faible profondeur et des mouvements de pente superficiels associes. Des resultats recents suggerent que l'effet de cette interaction peut egalement s'etendre a de grandes profondeurs dans les pentes argileuses naturelles. De multiples exemples de mecanismes de glissement de terrain profond induits par les conditions meteorologiques peuvent etre trouves dans les Apennins meridionaux (Italie), ou les pentes sont souvent formees d'argiles fissurees. La relation entre l'activite de ces glissements de terrain et les processus hydromecaniques dus a l'interaction sol-vegetation-atmosphere a ete etudiee ici au moyen d'une analyse bidimensionnelle couplee hydro-mecanique par elements finis. Un modele constitutif capable de simuler le comportement des argiles fortement surconsolidees, a la fois dans les etats satures et non satures, a ete adopte dans l'analyse, en conjonction avec une condition limite capable de reproduire les effets combines de l'infiltration des pluies, de l'evapotranspiration et du ruissellement. Les resultats de l'analyse corroborent le lien entre les conditions meteorologiques, les variations de pression interstitielle et les mouvements de pente dans les pentes argileuses naturelles. L'importance de reproduire adequatement l'histoire geologique d'un versant naturel afin de definir son etat actuel est egalement demontree. [Traduit par la Redaction] Mots-cles : modelisation numerique, analyse par elements finis, interaction sol- vegetation-atmosphere, pentes naturelles, glissements de terrain, argiles fissurees., Introduction Soil-atmosphere interaction has been extensively investigated in the laboratory and in the field (e.g., Blight 1997; Toll et al. 2011; Smethurst et al. 2012; Pirone et al. 2015; Askarinejad [...]
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- 2022
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6. Numerical investigation of a segmental grey cast iron tunnel ring: validation with laboratory data and application to field conditions
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Ruiz López, Agustín, Tsiampousi, Aikaterini, Standing, Jamie R., and Potts, David M.
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- 2022
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7. Destabilisation of seawall ground by ocean waves.
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Takahashi, Hidenori, Zdravković, Lidija, Tsiampousi, Aikaterini, and Mori, Nobuhito
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OCEAN waves ,FAILURE mode & effects analysis ,CONCRETE blocks ,WATER pressure ,THEORY of wave motion - Abstract
Seawalls are constructed by covering and protecting the sloping seashore ground with concrete plates or blocks. Their purpose is to sustain high waves induced by strong winds and prevent ground erosion, but they often collapse, mobilising different modes of failure, including that of the ground. Nevertheless, limited research has been conducted on ground failure caused by high waves. In this study, a series of novel centrifuge model tests was first conducted to investigate the failure mechanisms of seawalls due to wave propagation, focusing on the failure of the ground. Finite-element analyses were subsequently conducted to explore the failures observed in the model tests and to provide further insight as to the state of the ground leading to failure. Two failure modes were demonstrated to prevail: floating of the covering panel and sliding failure of the ground. In addition, of the possible causes of failure, the following three were identified in the current study: increased unit weight and reduced suction from wetting; enhanced seepage force under the panel and around the toe block during backwash; water pressure on the back of the panel and the landward side of the toe block during backwash. [ABSTRACT FROM AUTHOR]
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- 2024
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8. The importance of permeability in modelling soil-atmosphere interaction
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Tsiampousi Aikaterini
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Environmental sciences ,GE1-350 - Abstract
Soil-atmosphere interaction has been attracting increasing interest as the seasonal variation of pore water pressures (pwp) has been linked to a variety of geotechnical problems (e.g. slope stability and serviceability, foundation subsidence or swelling, desiccation cracking etc.) or has been identified as part of the solution of geotechnical problems (e.g. in sustainable urban drainage systems). Prediction of how the pwp will change within soils of low permeability under the combined effect of evapotranspiration and precipitation requires adequate knowledge of the soil permeability and how it varies spatially (e.g with depth) and temporally (e.g. with suction or degree of saturation, void ratio or due to the opening and closing of desiccation cracks). Nonetheless, in-situ measurements of permeability that satisfy both the spatial and temporal variation are difficult. In order to clarify the importance of variable permeability in predicting pwp variations under atmospheric loads, a series of one- and two-dimensional finite element analyses was performed, where the permeability model and the variation of permeability were parametrically studied. The results demonstrated that the variation of permeability, as well as the model employed in the analysis, e.g. allowing or not for desiccation cracking, influenced the values of suction calculated as well as the pwp profile with depth, highlighting the importance of estimating the spatial and temporal variation of permeability with some level of confidence.
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- 2023
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9. Numerical modelling of unsaturated MX-80 bentonite subjected to two different hydration paths and subsequent loading to high-pressures
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Pedone Giuseppe, Zdravkovi Lidija, Potts David, and Tsiampousi Aikaterini
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Environmental sciences ,GE1-350 - Abstract
MX-80 bentonite has been considered as a suitable material for the construction of engineered barriers employed in deep geological radioactive waste repositories. These barriers are generally formed of compacted unsaturated bentonite, the latter experiencing a slow saturation due to its low permeability whileinteracting with the surrounding groundwater. In order to verify the long-term safety requirements of engineered barriers, their response to hydration has to be carefully assessed. As part of the recent European project BEACON (Bentonite Mechanical Evolution), the behaviour of MX-80 bentonite subjected to different hydration paths was investigated in a number of laboratory and field experiments and numerical studies. This paper is concerned with numerical simulations of two laboratory experiments performed during the project, with the objective of examining the predictive capabilities of the proposed numerical modelling approach. The experiments were selected due to the granular state of bentonite at its placement in the testingapparatus, which differed from the large number of previous experiments conducted on specimens of compacted bentonite blocks. The paper provides a brief introduction to the adopted modelling framework, a summary of calibrated parameters for the hydro-mechanical constitutive modelling and the results of numerical simulations, concluding that a satisfactory numerical simulation of the experiments was achieved.
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- 2023
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10. 3D effects of soil-atmosphere interaction on infrastructure slope stability
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Tsiampousi Aikaterini
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Environmental sciences ,GE1-350 - Abstract
It has long been established that pore water pressure (pwp) variations affect the stability and serviceability of slopes. Pwp variations may be due to consolidation/swelling processes within soils of low permeability or may be due to seasonal evapotranspiration and precipitation processes. The simultaneous study of such phenomena and of hydro-mechanical coupling in sloping ground requires use of advancednumerical methods. Often, infrastructure slopes are considered in plane strain (two-dimensional) conditions for simplicity and to date this is the case for most numerical analyses considering soil-atmosphere interaction. However, this approach makes it impossible to study the longitudinal extent of a possible slip surface forming following vegetation removal. Three-dimensional, fully-coupled numerical analyses of acut slope were performed herein to study the effect of vegetation clearance on stability and explore numerically ways of implementing effective vegetation management.
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- 2023
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11. Thermo-mechanical behaviour of a kaolin-based clay soil
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Kirkham, Andrew, primary, Tsiampousi, Aikaterini, additional, and Potts, David M., additional
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- 2023
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12. Formulation and application of 3D THM-coupled zero-thickness interface elements
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Cui, Wenjie, Potts, David M., Zdravković, Lidija, Gawecka, Klementyna A., and Tsiampousi, Aikaterini
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- 2019
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13. A coupled thermo-hydro-mechanical finite element formulation for curved beams in two-dimensions
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Cui, Wenjie, Potts, David M., Zdravković, Lidija, Gawecka, Klementyna A., Taborda, David M.G., and Tsiampousi, Aikaterini
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- 2018
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14. Numerical analysis of slopes in unsaturated soils
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Tsiampousi, Aikaterini, Zdravkovic, Lidija, and Potts, David
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624.15 - Abstract
Conventional constitutive models developed for saturated soils are inadequate when analysing problems involving unsaturated conditions. Although unsaturated constitutive models are available in the Imperial College Finite Element Program (ICFEP), there are aspects of unsaturated soil response that are not adequately simulated. The aim of the present thesis is to develop and implement numerical expressions describing the most relevant of these features and to apply them in combination with the existing ICFEP capabilities to boundary value problems involving unsaturated soils. The over-prediction of the peak shear stress exhibited by overconsolidated soils and the simplicity of the soil-water retention relationship employed, constitute the focal points of the improvements suggested. A new surface is introduced to substitute for the yield and plastic potential functions on the dry side of critical state, in order to prevent the available constitutive models from overestimating the peak deviatoric stress. The development, implementation and calibration of this surface are presented, followed by analyses of laboratory experiments demonstrating the improved simulation of soil behaviour. Novel formulations are proposed for the soil-water retention curve, which defines the relationship between the degree of saturation or the water content and the applied suction, modelling its hysteretic nature and incorporating the effect of specific volume. Ultimately, a three-dimensional hysteretic surface, defined in terms of degree of saturation, suction and specific volume, is presented. The new developments are subsequently applied to the numerical analysis of boundary value problems involving (a) the stability of slopes in overconsolidated unsaturated soils and (b) the behaviour of unsaturated soil slopes under seasonal changes of suction, highlighting the importance of adopting appropriate constitutive models.
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- 2011
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15. Behaviour of bolted cast iron joints
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Tsiampousi, Aikaterini, Yu, Jessica, Standing, Jamie, Vollum, Robert, and Potts, David
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- 2017
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16. Coupled consolidation in unsaturated soils: From a conceptual model to applications in boundary value problems
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Tsiampousi, Aikaterini, Smith, Philip G.C., and Potts, David M.
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- 2017
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17. Coupled consolidation in unsaturated soils: An alternative approach to deriving the Governing Equations
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Tsiampousi, Aikaterini, Smith, Philip G.C., and Potts, David M.
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- 2017
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18. IC MAGE Flow Model 02 – Stress-dependent anisotropic permeability
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Taborda, David M G, Tsiampousi, Aikaterini, and Kontoe, Stavroula
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Finite Element Analysis ,Geotechnical Analysis ,Coupled Analysis ,Geotechnical Engineering ,Hydraulic Behaviour - Abstract
IC MAGE FM02 is a user-defined flow model for PLAXIS that allows the simulation of mean effective stress-dependent anisotropic permeability., {"references":["Gawecka, K.A., Taborda, D.M.G., Potts, D.M., Cui, W., Zdravkovic, L., Haji Kasri, M.S. (2017) Numerical modelling of thermo-active piles in London Clay. Proceedings of the ICE: Geotechnical Engineering, 170(3): 201-219."]}
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- 2023
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19. IC MAGE Model 04 – Mohr-Coulomb failure criterion with isotropic small strain stiffness and enhanced hysteresis control
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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Computer Science::Hardware Architecture ,Finite Element Analysis ,Geotechnical Analysis ,Cyclic loading ,Geotechnical Engineering ,Constitutive Modelling ,Small-strain Stiffness - Abstract
IC MAGE M04 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines a Mohr-Coulomb failure criterion with the IC.G3S isotropic small strain stiffness model and the nonlinear scaling factor proposed by Taborda & Zdravkovic (2012). It allows for the generation of hysteresis (and energy dissipation) by adopting a cyclic nonlinear elastic framework., {"references":["Darendeli, M. B. (2001) Development of a new family of normalized modulus reduction and material damping curves. PhD Thesis. University of Texas, Austin.","Korma, E. (2014) The Influence of Advanced Features of Cyclic Soil Response on Wave Propagation Problems. M.Sc. thesis. Imperial College London, London, UK.","Rollins, K. M., Evans, M. D., Daily, W. D., III & Diehl, N. B. (1998) Shear modulus and damping relationships for gravels. Journal of geotechnical and geoenvironmental engineering, 124 (5), 396-405. https://doi.org/10.1061/(ASCE)1090-0241(1998)124:5(396)","Taborda, D.M.G., Potts, D.M. and Zdravković, L. (2016). On the assessment of energy dissipated through hysteresis in finite element analysis. Computers and Geotechnics, 71, 180–194. https://doi.org/10.1016/j.compgeo.2015.09.001","Taborda, D.M.G and Zdravković, L. (2012). Application of a Hill-Climbing technique to the formulation of a new cyclic nonlinear elastic constitutive model. Computers and Geotechnics, 43, 80-91. https://doi.org/10.1016/j.compgeo.2012.02.001","Taborda, D.M.G., Kontoe, S. & Tsiampousi, A. (2021, June 23). IC MAGE UMIP - universal model interface for PLAXIS (Version 2.0). Zenodo. http://doi.org/10.5281/zenodo.5018865","Vucetic, M. & Dobry, R. (1991) Effect of soil plasticity on cyclic response. Journal of Geotechnical Engineering, ASCE, 117 (1), 89-107. https://doi.org/10.1061/(ASCE)0733-9410(1991)117:1(89)"]}
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- 2023
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20. IC MAGE Flow Model 01 – Nonlinearly varying anisotropic permeability
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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Finite Element Analysis ,Geotechnical Analysis ,Coupled Analysis ,Geotechnical Engineering ,Hydraulic Behaviour - Abstract
IC MAGE FM01 is a user-defined flow model for PLAXIS that allows the simulation of spatially-varying anisotropic permeability., {"references":["Avgerinos, V. (2014) Numerical investigation of tunnelling beneath existing tunnels. PhD Thesis, Imperial College London, UK.","Hight, D.W., Gasparre, A., Nishimura, S., Minh, N.A., Jardine, R.J., Coop, M.R. (2007) Characteristics of the London Clay from the terminal 5 site at Heathrow airport. Géotechnique, Vol.57, No.1, pp.: 3–18."]}
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- 2023
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21. IC MAGE Model 02 – Simple state-parameter dependent model with isotropic small strain stiffness
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Taborda, David M G, Pedro, Antonio M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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Computer Science::Hardware Architecture ,Sand ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling - Abstract
IC MAGE M02 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines the state-parameter framework by Been & Jefferies (1985) with a Mohr-Coulomb failure criterion. The elastic response is given by the isotropic small strain stiffness model IC.G3S by Taborda et al. (2016). A reversal detection algorithm within a cyclic nonlinear elastic framework allows for the generation of hysteresis (and energy dissipation)., {"references":["Been, K. and Jefferies, M.G. (1985) A state parameter for sands. Geotechnique, 35(2), 99-112. https://doi.org/10.1680/geot.1985.35.2.99","Taborda, D.M.G., Potts, D.M. and Zdravković, L. (2016). On the assessment of energy dissipated through hysteresis in finite element analysis. Computers and Geotechnics, 71, 180–194. https://doi.org/10.1016/j.compgeo.2015.09.001","Taborda, D.M.G., Potts, D.M., Zdravković, L. and Pedro, A.M.G. (2018) Incorporating the state parameter into a simple constitutive model for sand. Numerical Methods in Geotechnical Engineering IX. https://doi.org/10.1201/9780429446931","Taborda, D.M.G and Zdravković, L. (2012). Application of a Hill-Climbing technique to the formulation of a new cyclic nonlinear elastic constitutive model. Computers and Geotechnics, 43, 80-91. https://doi.org/10.1016/j.compgeo.2012.02.001","Taborda, David M G, Kontoe, Stavroula, & Tsiampousi, Aikaterini. (2021, June 23). IC MAGE UMIP - universal model interface for PLAXIS (Version 2.0). Zenodo. http://doi.org/10.5281/zenodo.5018865"]}
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- 2023
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22. IC MAGE Model 03 – strain-hardening/softening Mohr-Coulomb failure criterion with transversely isotropic small strain stiffness
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Taborda, David M G, Kontoe, Stavroula, Tsiampousi, Aikaterini, and Ruiz Lopez, Agustin
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Transverse isotropy ,Computer Science::Hardware Architecture ,Condensed Matter::Materials Science ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling ,Small-strain Stiffness - Abstract
IC MAGE M03 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines a strain-hardening/softening Mohr-Coulomb failure criterion based on the deviatoric plastic strain with the IC.G3S transversely isotropic small strain stiffness model. It allows for the generation of hysteresis (and energy dissipation) by adopting a cyclic nonlinear elastic framework., {"references":["Taborda, David M G, Kontoe, Stavroula, & Tsiampousi, Aikaterini. (2021, June 23). IC MAGE UMIP - universal model interface for PLAXIS (Version 2.0). Zenodo. http://doi.org/10.5281/zenodo.5018865"]}
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- 2023
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23. IC MAGE Model 01 – strain-hardening/softening Mohr-Coulomb failure criterion with isotropic small strain stiffness
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
- Subjects
Computer Science::Hardware Architecture ,Condensed Matter::Materials Science ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling ,Safety analysis ,Small-strain stiffness - Abstract
IC MAGE M01 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines a strain-hardening/softening Mohr-Coulomb failure criterion based on the deviatoric plastic strain with the IC.G3S (Taborda et al., 2016) isotropic small strain stiffness model. It allows for the generation of hysteresis (and energy dissipation) by adopting a cyclic nonlinear elastic framework. Safety analyses are also allowed using this model.
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- 2023
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24. Numerical investigation of the performance of engineered barriers in reducing flood risk
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Petalas Alexandros L., Tsiampousi Aikaterini, Zdravkovic Lidija, and Potts David M.
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Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
In this paper, 2-dimensional, hydro-mechanically coupled finite element analyses are performed to assess the performance of an engineered barrier aimed at reducing flood risk in urban environments. The barrier consists of an unsaturated compacted soil layer and a drainage layer of a coarse granular material, constructed on top of the natural soil, in this case London clay. The barrier is vegetated so that its water storage capacity is renewed after each rainfall event. Sophisticated boundary conditions are used to simulate the effect of precipitation and evapotranspiration. The rainfall water infiltration and the initiation of water run-off during intense precipitation events are simulated. The effect of the hydraulic properties of the unsaturated soil layer on the performance of the system is investigated by means of parametric analyses. The effect of precipitation rate and geometry of the barrier is also discussed. Design recommendations for the properties of the compacted layer and the dimensions of the system are given at the end of the paper.
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- 2021
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25. Destabilisation of seawall ground by ocean waves
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Takahashi, Hidenori, primary, Zdravković, Lidija, additional, Tsiampousi, Aikaterini, additional, and Mori, Nobuhito, additional
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- 2022
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26. IC MAGE Model 09 – Non-local simple state-parameter dependent model with isotropic small strain stiffness
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Taborda, David M G, Pedro, Antonio M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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Computer Science::Hardware Architecture ,Sand ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling - Abstract
IC MAGE M09 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines the state-parameter framework by Been & Jefferies (1985) with a Mohr-Coulomb failure criterion. The elastic response is given by the isotropic small strain stiffness model IC.G3S by Taborda et al. (2016). A reversal detection algorithm within a cyclic nonlinear elastic framework allows for the generation of hysteresis (and energy dissipation). This model is the nonlocal version of IC MAGE M02., {"references":["Been, K. and Jefferies, M.G. (1985) A state parameter for sands. Geotechnique, 35(2), 99-112. https://doi.org/10.1680/geot.1985.35.2.99","Taborda, D.M.G., Potts, D.M. and Zdravković, L. (2016). On the assessment of energy dissipated through hysteresis in finite element analysis. Computers and Geotechnics, 71, 180–194. https://doi.org/10.1016/j.compgeo.2015.09.001","Taborda, D.M.G., Potts, D.M., Zdravković, L. and Pedro, A.M.G. (2018) Incorporating the state parameter into a simple constitutive model for sand. Numerical Methods in Geotechnical Engineering IX. https://doi.org/10.1201/9780429446931","Taborda, D.M.G and Zdravković, L. (2012). Application of a Hill-Climbing technique to the formulation of a new cyclic nonlinear elastic constitutive model. Computers and Geotechnics, 43, 80-91. https://doi.org/10.1016/j.compgeo.2012.02.001"]}
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- 2022
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27. IC MAGE Model 13 – Mohr-Coulomb failure criterion with stress-dependent elastic stiffness and cross-correlated random parameter distributions
- Author
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Taborda, David M G, Galtier, Lucinda, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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endocrine system ,Random Fields ,Soil Variability ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling ,neoplasms - Abstract
IC MAGE M13 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework in which a stress-dependent elastic response is combined with a Mohr-Coulomb failure criterion. Both the stiffness parameters and the strength parameters are determined following cross-correlated random distributions (either normal or log-normal).
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- 2022
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28. IC MAGE Model 07 – Simple non-linear time-dependent stiffness model for concrete
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
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Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling ,Concrete - Abstract
IC MAGE M07 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which provides a simple way of modelling the stiffness increase observed in concrete during concrete, following the expression by the CEB-FIP (1990)., {"references":["Taborda, DMG, Kontoe, S, Tsiampousi, A (2021, July 23) \"IC MAGE UMIP – universal model interface for PLAXIS (Version 2.1)\". Zenodo. doi: 10.5281/zenodo.5123555"]}
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- 2022
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29. IC MAGE Model 06 – Modified Cam-clay model with a non-linear Hvorslev surface and isotropic small strain shear stiffness
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Tsiampousi, Aikaterini, Kontoe, Stavroula, and Taborda, David MG
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Finite Element Analysis ,Geotechnical Analysis ,Clay ,Geotechnical Engineering ,Constitutive Modelling ,Small-strain stiffness - Abstract
IC MAGE M06 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines a Modified Cam-clay (MCC) model on the wet side of Critical State and a non-linear Hvorslev (HV) surface on the dry side with the IC.G3S isotropic small strain shear stiffness model. It allows for the generation of hysteresis (and energy dissipation) by adopting a cyclic nonlinear elastic framework. The bulk stiffness is defined by the elastic behaviour within MCC.
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- 2022
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30. Effect of hydraulic parameters on the computed serviceability of infrastructure slopes
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Tsiampousi Aikaterini, Zdravkovic Lidija, and Potts David M.
- Subjects
Environmental sciences ,GE1-350 - Abstract
Atmospheric phenomena such as rainfall and evapotranspiration contribute to slope movements in unsaturated soils, the study of which requires fully coupled numerical methods, combined with realistic boundary conditions and appropriate mechanical and hydraulic soil properties. This paper focuses on the effect of the hydraulic behaviour, and in particular of the modelling of the soil-water retention curve and the permeability on slope movements, with the aim of identifying which model parameters are critical and, therefore, require careful experimental identification.
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- 2020
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31. Overview and conceptual constitutive framework for pellet-based buffer materials
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Ghiadistri Giulia M., Zdravkovic Lidija, Potts David M., and Tsiampousi Aikaterini
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Environmental sciences ,GE1-350 - Abstract
Buffer materials for nuclear waste disposal applications generally consist of blocks made of highly expansive compacted clay. However, high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. The material response of pellet-based buffers may be quite different from that of compacted buffers, because of the peculiar discontinuous porosity presented. An overview of the literature available on pellet-based buffers is presented and, in particular, two main topics are discussed: firstly, the characteristics of the fabric of the pellets that can be observed through techniques of micro-structural investigation, secondly, the most important behavioural features that can be seen during material testing. Additionally, the constitutive frameworks that have already been developed specifically for pellets are also reviewed. The overall objective of the paper is to highlight the differences between compacted and pellet-based bentonite buffers, in order to propose suitable assumptions to start developing a constitutive model for the latter.
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- 2020
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32. Development of a new temperature-controlled oedometer
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Kirkham Andrew, Tsiampousi Aikaterini, and Potts David
- Subjects
Environmental sciences ,GE1-350 - Abstract
A new temperature-controlled oedometer has been designed at Imperial College London and commissioned to investigate the thermo-hydro-mechanical behaviour of soils. Under oedometric conditions, temperature can be varied between 5°C and 70°C, by submerging the specimen in a temperature-controlled water bath. This temperature range is appropriate for the proposed applications of the research: design of ground-source heating/cooling systems, and design of geological disposal facilities for nuclear waste. In this paper, an overview of the new equipment is given: its design, development, and calibration. First, the literature on temperature-controlled oedometer schemes is reviewed. A description of the equipment follows, with further details on the innovations and limitations of this design. As the equipment has been modified and improved over the course of the research, so too has the calibration procedure. These developments are discussed, again with the focus on innovations and limitations. Finally, a test programme and preliminary results are presented, for saturated KSS, an artificial mixture of kaolin clay, silt, and sand. These include isobaric (constant-pressure) heating tests, for a variety of loading histories. Over-consolidation ratio is found to affect the thermally-induced volume change.
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- 2020
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33. Stability of Highly Overconsolidated Soil Slopes
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Tsiampousi, Aikaterini, Zdravkovic, Lidija, Potts, David M., Mancuso, Claudio, editor, Jommi, Cristina, editor, and D’Onza, Francesca, editor
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- 2012
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34. Calibration of a double structure constitutive model for unsaturated compacted soils
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Ghiadistri Giulia, Zdravković Lidija, Potts David M., and Tsiampousi Aikaterini
- Subjects
Environmental sciences ,GE1-350 - Abstract
This paper describes a calibration procedure for the double structure constitutive model ICDSM (Imperial College Double Structure Model), developed for highly expansive clays, when the model is applied to MX-80 bentonite. Firstly, the model calibration process is discussed and organised in a number of hierarchical steps. These steps involve the estimation of the macrostructural parameters that can be derived from oedometer, isotropic and triaxial laboratory data. Estimation of the microstructural parameters is more challenging due to the limited knowledge of an expansive clay’s fabric and of the physico-chemical phenomena that control its evolution upon wetting. Nevertheless, this paper discusses the available sources of data and identifies the appropriate information that is needed to characterise the micro-structural behaviour of the bentonite. Finally, through the simulation of a swelling pressure test on a bentonite plug, the hydration of the material is studied as a hydro-mechanical coupled process. Particular attention is devoted to the evolution of the stress state of the sample, which is compared to the experimental measurements in order to demonstrate that the constitutive model accurately reproduces the expansive behaviour of MX-80 bentonite.
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- 2019
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35. IC MAGE Model 05 - non-local strain-hardening/softening Mohr-Coulomb with isotropic small strain stiffness
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
- Subjects
Computer Science::Hardware Architecture ,Condensed Matter::Materials Science ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling ,Non-local Methods - Abstract
IC MAGE M05 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines a strain-hardening/softening Mohr-Coulomb failure criterion based on the non-local total deviatoric strain calculated by PLAXIS with the IC.G3S isotropic small strain stiffness model. It allows for the generation of hysteresis (and energy dissipation) by adopting a cyclic nonlinear elastic framework., {"references":["Taborda, David M G, Kontoe, Stavroula, & Tsiampousi, Aikaterini. (2021, September 17). IC MAGE UMIP - universal model interface for PLAXIS (Version 2.2). Zenodo. http://doi.org/10.5281/zenodo.5513997"]}
- Published
- 2021
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36. IC MAGE Model 02 – simple state-parameter dependent model with isotropic small strain stiffness
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Taborda, David M G, Kontoe, Stavroula, and Tsiampousi, Aikaterini
- Subjects
Computer Science::Hardware Architecture ,Sand ,Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling - Abstract
IC MAGE M02 is a user-defined model for PLAXIS built using the IC MAGE UMIP framework which combines the state-parameter framework by Been & Jefferies (1985) with a Mohr-Coulomb failure criterion. The elastic response is given by the isotropic small strain stiffness model IC.G3S by Taborda et al. (2016). A reversal detection algorithm within a cyclic nonlinear elastic framework allows for the generation of hysteresis (and energy dissipation).
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- 2021
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37. IC MAGE UMIP - universal model interface for PLAXIS
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Taborda, David M G, Kontoe, Stavroula, Tsiampousi, Aikaterini, Tantivangphaisal, Pishun, Ruiz Lopez, Agustin, and Moller, Julia
- Subjects
Finite Element Analysis ,Geotechnical Analysis ,Geotechnical Engineering ,Constitutive Modelling - Abstract
Documentation for IC MAGE's Universal Model Interface for PLAXIS. The Universal Model Interface for PLAXIS (UMIP) is a platform designed to facilitate the implementation of constitutive models into PLAXIS. Currently, the only integration scheme available for the constitutive relationship is a Modified Euler substepping scheme with automatic error control., {"references":["Azeiteiro, R.J.N. (2021) Numerical simulation of liquefaction-related phenomena. PhD Thesis, University of Coimbra, Portugal.","Dowell, M. and Jarratt, P. (1972). The 'Pegasus' method for computing the root of an equation. BIT Numerical Mathematics, 12 (4), 503–508.","Hong, P.Y., Pereira, J.M., Cui, Y.J. and Tang, A.M. (2012). Explicit integration of a thermo-mechanical model for clays. Computers and Geotechnics, 46, 13–25.","Potts, D.M. and Gens, A. (1985). A critical assessment of methods of correcting for drift from the yield surface in elasto-plastic finite element analysis. International Journal for Numerical and Analytical Methods in Geomechanics, 9 (2), 149–159.","Potts, D.M. and Zdravkovic, L. (1999). Finite element analysis in geotechnical engineering. Theory. London, U.K., Thomas Telford Publishing.","Sloan, S.W. (1987). Substepping schemes for numerical integration of elasto-plastic stress-strain relations. International Journal for Numerical Methods in Engineering, 24 (5), 893–911.","Sloan, S.W., Abbo, A.J. and Sheng, D. (2001). Refined explicit integration of elastoplastic models with automatic error control. Engineering Computations, 18 (1), 121–194.","Taborda, D.M.G., Potts, D.M. and Zdravković, L. (2016). On the assessment of energy dissipated through hysteresis in finite element analysis. Computers and Geotechnics, 71, 180–194.","Taborda, D.M.G and Zdravković, L. (2012). Application of a Hill-Climbing technique to the formulation of a new cyclic nonlinear elastic constitutive model. Computers and Geotechnics, 43, 80-91."]}
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- 2021
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38. Investigating soil water retention characteristics at high suctions using relative humidity control
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Mantikos Vasileios, Ackerley Steven, Kirkham Andrew, Tsiampousi Aikaterini, Taborda David M.G., and Standing Jamie
- Subjects
Environmental sciences ,GE1-350 - Abstract
A technique for controlling relative humidity (RH) is presented, which involves supplying a sealed chamber with a continuous flow of air at a computer-regulated RH. The desired value of RH is achieved by mixing dry and wet air at appropriate volumes and is measured for servo-control at three locations in the chamber with capacitive RH sensors and checked with a sensitive VAISALA sensor. The setup is capable of controlling RH steadily and continuously with a deviation of less than 0.2% RH. The technique was adopted to determine wetting soil-water retention curves (SWRC) of statically compacted London Clay, under both free-swelling and constant volume conditions. The RH within the chamber was increased in a step-wise fashion, with each step maintained until vapour equilibrium between the chamber atmosphere and the soil samples was established. Independent filter paper measurements further validate the method, while the obtained retention curves complement those available in the literature for lower ranges of suction.
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- 2016
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39. Effects of Soil-Vegetation-Atmosphere Interaction on the Stability of a Clay Slope: A Case Study
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Pedone Giuseppe, Tsiampousi Aikaterini, Cotecchia Federica, and Zdravkovic Lidija
- Subjects
Environmental sciences ,GE1-350 - Abstract
Deep and slow landslide processes are frequently observed in clay slopes located along the Southern Apennines (Italy). A case study representative of these processes, named Pisciolo case study, is discussed in the paper. The geo-hydro-mechanical characteristics of the materials involved in the instability phenomena are initially discussed. Pluviometric, piezometric, inclinometric and GPS monitoring data are subsequently presented, suggesting that rainfall infiltration constitutes the main factor inducing slope movements. The connection between formation of landslide bodies and slope-atmosphere interaction has been demonstrated through a hydro-mechanical finite element analysis, whose results are finally reported in the work. This analysis has been conducted employing a constitutive model that is capable of simulating both saturated and unsaturated soil behaviour, as well as a boundary condition able to simulate the effects of the soil-vegetation-atmosphere interaction.
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- 2016
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40. Soil-atmosphere interaction in unsaturated cut slopes
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Tsiampousi Aikaterini, Zdravkovic Lidija, and Potts David M.
- Subjects
Environmental sciences ,GE1-350 - Abstract
Interaction between atmosphere and soil has only recently attracted significant interest. Soil-atmosphere interaction takes place under dynamic climatic conditions, which vary throughout the year and are expected to suffer considerable alterations due to climate change. However, Geotechnical Analysis has traditionally been limited to simplistic approaches, where winter and summer pore water pressure profiles are prescribed. Geotechnical Structures, such as cut slopes, are known to be prone to large irreversible displacements under the combined effect of water uptake by a complex vegetation root system and precipitation. If such processes take place in an unsaturated material the complexity of the problem renders the use of numerical analysis essential. In this paper soil-atmosphere interaction in cut slopes is studied using advanced, fully coupled partially saturated finite element analyses. The effect of rainfall and evapotranspiration is modelled through sophisticated boundary conditions, applying actual meteorological data on a monthly basis. Stages of low and high water demand vegetation are considered for a period of several years, before simulating the effect of vegetation removal. The analysis results are presented with regard to the serviceability and stability of the cut slope.
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- 2016
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41. Numerical investigation of the performance of engineered barriers in reducing flood risk.
- Author
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de Campos, T.M.P., Marinho, F.A.M., Gitirana Jr., G.F.N., Mascarenha, M.M.A., Petalas, Alexandros L., Tsiampousi, Aikaterini, Zdravkovic, Lidija, and Potts, David M.
- Published
- 2021
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42. Numerical Modeling of Time-Dependent Thermally Induced Excess Pore Fluid Pressures in a Saturated Soil
- Author
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Cui, Wenjie, primary, Tsiampousi, Aikaterini, additional, Potts, David M., additional, Gawecka, Klementyna A., additional, and Zdravković, Lidija, additional
- Published
- 2020
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43. Overview and conceptual constitutive framework for pellet-based buffer materials.
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Cardoso, R., Jommi, C., Romero, E., Ghiadistri, Giulia M., Zdravkovic, Lidija, Potts, David M., and Tsiampousi, Aikaterini
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- 2020
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44. Effect of hydraulic parameters on the computed serviceability of infrastructure slopes.
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Cardoso, R., Jommi, C., Romero, E., Tsiampousi, Aikaterini, Zdravkovic, Lidija, and Potts, David M.
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- 2020
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45. Thermo-mechanical Calibration of a Temperature-Controlled Oedometer
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Kirkham, Andrew, Tsiampousi, Aikaterini, and Potts, David M.
- Abstract
In the emerging field of energy geotechnics, many applications involve changes of temperature above and below ambient temperature. This has led to the development of laboratory apparatus to enable the study of soil behavior under various temperature ranges and under well-controlled conditions. To understand the effect of temperature on soil behavior, it is necessary to separate the thermal behavior of the apparatus itself and of the instrumentation used to measure loads and displacements from the soil behavior, i.e., a careful calibration of the equipment is required. The thermal calibration of an oedometer with temperature control in the range of 5°C–70°C is discussed here in detail. As the innovative design of the new oedometer enables isotropic heating of the soil specimen and thermal isolation of the instrumentation, the calibration focuses on the thermally induced deformations of the apparatus and the differential radial thermally induced deformation of the soil and of the stainless steel confining ring. Although the developed methodology has limitations when used to predict the results of one-dimensional tests, as do previously proposed methodologies, it represents improvements on previous schemes, as it allows for Poisson’s ratio effects to be taken into account. An example of how the proposed calibration can be used in practice and how the confining ring correction compares with previous schemes is presented.
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- 2024
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46. Variation with time of the factor of safety of slopes excavated in unsaturated soils
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Tsiampousi, Aikaterini, primary, Zdravković, Lidija, additional, and Potts, David M., additional
- Published
- 2013
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47. A new Hvorslev surface for critical state type unsaturated and saturated constitutive models
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Tsiampousi, Aikaterini, primary, Zdravković, Lidija, additional, and Potts, David M., additional
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- 2013
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48. Reuse and sustainability of flood defences
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Guo, Benjamin Wei Li, Zdravkovic, Lidija, Tsiampousi, Aikaterini, and Onof, Christian
- Abstract
Rainfall has always been an important quantity to measure throughout history due to its importance in predicting floods and droughts. In the present day, such predictions on the severity of flooding events are critical so that appropriate flood defences may be constructed in anticipation of these events to limit any damages. With the increasing concerns of human influenced (anthropogenic) climate change will affect rainfall, there is a growing need to quantify and incorporate these events into the design of flood defences, such as earthfill embankments. As geotechnical modelling techniques are being developed to assist in the design and upgrading of earth embankments, various failure mechanisms and the behaviour of the soil within an embankment are better understood. However, one concern which arises is that there is an uncertainty on how climate change would affect the performance of these embankments. Therefore, the main purpose of this research is to identify the key failure mechanisms that may occur throughout the embankment's life cycle, taking into account climate change effects, and to develop solutions to these issues. A site on the Thames estuary was chosen as the setting for this research. Taking into consideration a changing climate, sub-daily rainfall was produced for this site using a combination of stochastic rainfall generators and projected climate variables at the location. Following calibration and validation analyses for the foundation and embankment soils, a complete lifecycle analysis framework was established, using the previously generated rainfall as inputs to the soil-atmosphere boundary. The lifecycle framework was able to inform on both the general long-term performance of the embankment in a changing climate, and the resilience of the embankment to future extreme events. With the detailed lifecycle analysis, various strategies in reusing the embankment by raising it was also explored, to improve the embankment's adaptability to future climate.
- Published
- 2022
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49. Development of a new temperature-controlled oedometer
- Author
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Kirkham, Andrew, Tsiampousi, Aikaterini, and Potts, David
- Abstract
A new temperature-controlled oedometer has been designed at Imperial College London and commissioned to investigate the thermo-hydro-mechanical (THM) behaviour of soils. The proposed application of the research is the design of underground structures which heat or cool the surrounding soil, such as ground source heating/cooling systems, and geological disposal facilities for nuclear waste. High-quality laboratory test data, which are currently lacking, are required for understanding thermal effects on soil, and for calibrating THM constitutive models, used for modelling soil-structure interactions. In the new equipment, the temperature of the tested specimen is controlled between 5°C and 70°C with a temperature-controlled water bath. For heating above ambient temperature, the water bath is heated directly using three 150W heaters. For cooling below ambient temperature, an external chiller unit is used, in combination with a heat exchanger. Water is continuously circulated through a hollow plate, directly below the specimen, which minimises the temperature gradient across the specimen. A full, thermal and mechanical calibration of the equipment has been carried out. Vertical thermal and mechanical compliance is determined by repeating the full heating/loading path for the proposed test, with no soil specimen in place. The thermal and mechanical corrections are applied separately, not in combination, because of the much larger magnitude of mechanical strains (and associated error). The instrumentation (load cell and displacement transducers) is raised above the lid of the water bath to isolate it from temperature changes. The differential, thermal, lateral expansion of the confining ring and soil has been considered in the calculation of the soil volume, as too has the thermal expansion of the solid phase of the soil in the calculation of the void ratio. The effect of friction, tilting, and compressible components of the equipment (filter papers and porous stones), has been investigated. Based on these tests, the use of filter papers is discouraged for testing in general, and for thermal testing in particular. New methodologies for performing thermal tests using the new equipment have been developed and are presented here. These cover calibration, testing, and data-processing, and make explicit exactly how all measured and calculated values are obtained, including how the calibration is determined and applied. Soil tests have been performed to develop and validate the calibration, testing, and data-processing methodologies, using bentonite clay, Leighton Buzzard sand, and KSS clay (a mixture of kaolin, silt and sand). The results from the final series of thermal tests, on KSS, constitute a high-quality data-set, which could be used to calibrate a constitutive model, such as the IC Thermal model used in the Imperial College Finite Element Program (ICFEP). The effect of repeated thermal cycling on normally-consolidated and over-consolidated soil, and the effect of temperature and temperature history on soil behaviour has been tested. The new temperature-controlled oedometer, together with the new calibration, testing, and data-processing methodologies, can now be used to obtain high-quality data on the one-dimensional thermo-hydro-mechanical properties of other soils.
- Published
- 2021
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50. Development of novel apparatus for establishing swelling and water retention characteristics of bentonite
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Mantikos, Vasileios, Tsiampousi, Aikaterini, and Standing, Jamie R.
- Abstract
Despite the breakthroughs in suction control and measurement for laboratory testing of unsaturated soils at the range of high suctions, existing equipment faces limitations in either the precision, the range, or the practicality. The aim of the present thesis is to develop novel apparatus for establishing the swelling and water retention characteristics of compacted bentonite, which may exhibit very high suctions at its as-compacted state. The development of the equipment is based upon the best elements of existing equipment, combined in a simple and efficient manner and extends the range of existing suction-controlled facilities in the Geotechnics Laboratory of Imperial College London. A new humidity generator is presented, based on the principles of the divided-flow method. The divided-flow humidity generator (dfHG) controls the relative humidity (RH) in a sealed chamber, allowing suction control of soil samples through the Vapour Equilibrium Technique (VET). The control of RH is automated and is obtained by the proportional mixing of dry and wet air based on the feedback given on RH measurements in the chamber with affordable, individually calibrated capacitance hygrometers. Direct comparison with other suction-control methods, and derivation of water retention curves for reference soil materials validate the method. The automated control and the continuous operational range of suction provides the versatility of pressure generators, while the simplicity of the system is comparable to the practicality of the air-regulation method. The humidity generator is subsequently adapted to a newly-developed oedometer, to assist in the investigation of highly expansive clays, such as bentonites. The device allows the application of continuous, automated control of suction in the range between 30 MPa and 300 MPa, while applying complex stress and hydraulic paths for swelling tests. Equilibrium on each suction step is assessed through the combined evaluation of swelling stress, RH of the outflow air and water exchanged with the soil sample. The method is validated through successful investigation of the swelling behaviour of a natural sodium bentonite.
- Published
- 2019
- Full Text
- View/download PDF
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