Publications
225 results found
Climent N, Arroyo M, O'Sullivan C, et al., 2013, Sensitivity to Damping in Sand Production DEM-CFD Coupled Simulations, 7th International Conference on Micromechanics of Granular Media (Powders and Grains), Publisher: AMER INST PHYSICS, Pages: 1170-1173, ISSN: 0094-243X
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- Citations: 9
Hanley KJ, Huang X, O'Sullivan C, et al., 2013, Challenges of Simulating Undrained Tests Using the Constant Volume Method in DEM, 7th International Conference on Micromechanics of Granular Media (Powders and Grains), Publisher: AMER INST PHYSICS, Pages: 277-280, ISSN: 0094-243X
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- Citations: 15
O'Sullivan C, Wadee MA, Hanley KJ, et al., 2013, Use of DEM and elastic stability analysis to explain the influence of the intermediate principal stress on shear strength, Geotechnique, Vol: 63, Pages: 1298-1309, ISSN: 0016-8505
One interesting aspect of soil response is the sensitivity of the mechanical behaviour to the intermediate principal stress. In this study, a fundamental mechanism that explains the influence of the intermediate stress ratio (b) on soil shear strength is proposed. Prior experimental, numerical and analytical studies have indicated that soil failure occurs when the strong force chains that transmit stress through the material buckle. These strong force chains are networks of contacting particles that are relatively highly stressed and aligned in the direction of the major principal stress. The buckling resistance is thought to be determined by “weaker” lateral networks of less-stressed contacting particles that are orthogonal to the strong force chain orientation. Discrete Element Method (DEM) simulations of true triaxial tests show that as b is varied, so too is the relative support provided by the force chains orientated in the directions of the intermediate and minor principal stresses. At a macro-scale, the effective axial stiffnesses along these directions vary. The DEM dataset is complex and so a conceptually simple model is used to assess the influence of lateral support on the buckling resistance of a single column of connected nodes, analogous to a single force chain. The lateral support is modelled using linear springs. When the stiffnesses of these springs are selected to reflect the variation in axial stiffness with b observed in the DEM simulations, the reduction in axial buckling load with b is found to be similar to the reduction in major principal stress with b. When combined, the DEM data and simple analytical model support a hypothesis that failure under three-dimensional stress conditions is determined by buckling of the strong force chains. It is the variation in lateral support provided by the force network aligned along the minor and intermediate stress directions that determines, in part at least, the relation between soil shear str
Bym T, Marketos G, Burland JB, et al., 2013, Use of a two-dimensional discrete-element line-sink model to gain insight into tunnelling-induced deformations, Geotechnique
Marketos G, O'Sullivan C, 2013, A micromechanics-based analytical method for wave propagation through a granular material, Soil Dynamics and Earthquake Engineering, Vol: 45, Pages: 25-34
Bernhardt ML, O'sullivan C, Biscontin G, 2012, Macro- and micro-scale effects of pluviation based sample preparation in DEM, Pages: 2392-2401, ISSN: 0895-0563
Previous laboratory studies and Distinct Element Method (DEM) simulations have shown that the preparation method used to create samples for testing can affect the sample fabric and hence the mechanical response observed. The specimen preparation methods traditionally used in the laboratory were developed to recreate a given depositional pattern or in-situ soil fabric. Differences in soil response have been attributed to variations in the initial fabric of the sample even when the samples are created at the same densities. If DEM simulations are to provide meaningful insight into soil response observed in element tests, it is important for the initial state (packing density and stress level) and fabric anisotropy of the computer generated sample to closely match the physical reality. This is particularly true where element tests are used to validate DEM models. A key challenge is the lack of quantitative data on the fabric of real physical test specimens. Several approaches have been documented in the literature for generating the initial configuration of specimens for DEM simulations, i.e. artificially creating a percolating (stress transmitting) granular material. Approaches that are commonly used include radius expansion, compression using rigid boundaries, and pluviation under gravity loading. This paper examines the influence of the method chosen on the macro- and micro-scale properties of the material generated. The methods considered involved generating particles as a diffuse cloud at their target size, followed by pluviation under gravity loading with and without a mesh that modeled a sieve. The study fits within a broader research project in which multidirectional simple shear tests on steel spheres will be replicated in DEM simulations. © 2012 American Society of Civil Engineers.
O'Donovan J, O'Sullivan C, Marketos G, 2012, Two-dimensional discrete element modelling of bender element tests on an idealised granular material, GRANULAR MATTER, Vol: 14, Pages: 733-747, ISSN: 1434-5021
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- Citations: 31
Hanley KJ, O'Sullivan C, Byrne EP, et al., 2012, Discrete element modelling of the quasi-static uniaxial compression of individual infant formula agglomerates, PARTICUOLOGY, Vol: 10, Pages: 523-531, ISSN: 1674-2001
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- Citations: 11
Fonseca J, O'Sullivan C, Coop MR, et al., 2012, Non-invasive characterization of particle morphology of natural sands, SOILS AND FOUNDATIONS, Vol: 52, Pages: 712-722, ISSN: 0038-0806
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- Citations: 179
Cavarretta I, O'Sullivan C, 2012, The mechanics of rigid irregular particles subject to uniaxial compression, GEOTECHNIQUE, Vol: 62, Pages: 681-692, ISSN: 0016-8505
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- Citations: 39
Barreto D, O'Sullivan C, 2012, The influence of inter-particle friction and the intermediate stress ratio on soil response under generalised stress conditions, GRANULAR MATTER, Vol: 14, Pages: 505-521, ISSN: 1434-5021
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- Citations: 124
Cavarretta I, O'Sullivan C, Ibraim E, et al., 2012, Characterization of artificial spherical particles for DEM validation studies, PARTICUOLOGY, Vol: 10, Pages: 209-220, ISSN: 1674-2001
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- Citations: 44
Ghedia R, O'Sullivan C, 2012, Quantifying void fabric using a scan-line approach, COMPUTERS AND GEOTECHNICS, Vol: 41, Pages: 1-12, ISSN: 0266-352X
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- Citations: 26
Bhreasail AN, Lee PD, O'Sullivan C, et al., 2012, In-Situ Observation of Cracks in Frozen Soil using Synchrotron Tomography, PERMAFROST AND PERIGLACIAL PROCESSES, Vol: 23, Pages: 170-176, ISSN: 1045-6740
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- Citations: 29
Yuan L, O'Sullivan C, Gourlay CM, 2012, Exploring dendrite coherency with the discrete element method, ACTA MATERIALIA, Vol: 60, Pages: 1334-1345, ISSN: 1359-6454
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- Citations: 37
Shire T, O'Sullivan C, 2012, Micromechanical assessment of an internal stability criterion, Acta Geotechnica
Yuan L, O'Sullivan C, Gourlay CM, 2012, Numerical study of dendrite coherency during equiaxed solidification by the Discrete Element Method, 13th International Conference on Modeling of Casting, Welding and Advanced Solidification Processes (MCWASP), Publisher: IOP PUBLISHING LTD, ISSN: 1757-8981
Fonseca J, O'Sullivan C, Coop MR, et al., 2012, Quantifying the Evolution of Soil Fabric during Shearing using Directional Parameters, Geotechnique
O'Sullivan C, 2011, Particle-Based Discrete Element Modeling: Geomechanics Perspective, INTERNATIONAL JOURNAL OF GEOMECHANICS, Vol: 11, Pages: 449-464, ISSN: 1532-3641
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- Citations: 154
Hanley KJ, Cronin K, O'Sullivan C, et al., 2011, Effect of composition on the mechanical response of agglomerates of infant formulae, JOURNAL OF FOOD ENGINEERING, Vol: 107, Pages: 71-79, ISSN: 0260-8774
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- Citations: 23
Hanley KJ, O'Sullivan C, Oliveira JC, et al., 2011, Application of Taguchi methods to DEM calibration of bonded agglomerates, Powder Technology, Vol: 210, Pages: 230-240
O'Sullivan C, 2011, Particulate Discrete Element Modelling, Publisher: CRC Press, ISBN: 9780415490368
This is the first single work on Discrete Element Modelling (DEM) providing the information to get started with this powerful numerical modelling approach.
Butlanska J, O'Sullivan C, Arroyo M, et al., 2011, Mapping deformation during CPT in a virtual calibration chamber, International Symposium on Geomechanics and Geotechnics - From Micro to Macro, Publisher: CRC PRESS-TAYLOR & FRANCIS GROUP, Pages: 559-564
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- Citations: 6
O'Donovan J, O'Sullivan C, Marketos G, 2011, Discrete element modelling of a two-dimensional stress-controlled cubical cell apparatus, 5th International Symposium on Deformation Characteristics of Geomaterials (IS), Publisher: IOS PRESS, Pages: 439-446
Shen C-K, O'Sullivan C, Jardine RJ, 2011, A Micromechanical Investigation of Drained Simple Shear Tests, 5th International Symposium on Deformation Characteristics of Geomaterials (IS), Publisher: IOS PRESS, Pages: 314-321
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- Citations: 10
Summersgill F, O'Sullivan C, 2010, Developing an insight into the particle-scale mechanisms that underlie suffusion in granular filters, Pages: 134-145
Suffusion is a potential mechanism for internal erosion in the filters of dams and embankments. The mechanisms that drive the initiation and subsequent propagation of suffusion operate at the scale of the individual particles. Consequently it is difficult to analyze these mechanisms in detail using conventional experimental or numerical techniques. Discrete element modelling (DEM) is a method of numerical simulation that explicitly considers individual particles, their motions and the forces that are generated between them. This paper discusses the use of a 2D DEM model to analyze the influence of the particle size distribution on the material microstructure. Specifically the variation in contact forces, particle stresses, void ratios, pore size distribution and the connectivity of the particles are considered. While the results of these 2D simulations cannot be directly applied to real 3D soils, insight to inform our understanding of the mechanisms is gained.
Soga K, O'Sullivan C, 2010, Modeling of Geomaterials Behavior, Soils and Foundations, Vol: 50, Pages: 861-875
Hu M, O'Sullivan C, Jardine RR, et al., 2010, Stress-induced anisotropy in sand under cyclic loading, Granular Matter, Vol: 10, Pages: 469-476
hu M, O'Sullivan C, Jardine RR, et al., 2010, Stress-induced anisotropy in sand under cyclic loading, International Symposium on Geomechanics and Geotechnics - From Micro to Macro, Publisher: SPRINGER, Pages: 469-476, ISSN: 1434-5021
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- Citations: 32
Hu M, O'Sullivan C, Jardine RR, et al., 2010, Study on the deformation of loose sand under cyclic loading by DEM simulation, Pages: 212-219, ISSN: 0895-0563
The extensive use of granular materials as roadbeds accelerates the study of sand behavior under cyclic loading. While several studies have been done on sand deformation under cyclic loading, little information is available on the explanations for this behavior. By discrete element method (DEM) simulation, this paper offered a preliminary insight into particles interaction of loose sand which controls the material's stress-strain behavior. A 2-D 'sample' of 896 'quartz' disks, with diameters of 0.20, 0.25 and 0.30mm, was produced by self-gravity sediment. Then it was K0 loaded to t' = 127 kPa, at which point, the sample started to be cyclically loaded for 5000 cycles when t' kept constant. Cyclic amplitudes varied from 0.02 to0.04 t'. Increasing strain accumulation with increased number of cycles was observed. For smaller cyclic amplitude, strain accumulation increased smoothly, but for larger one, strain accumulation increased erratically after a large number of cycles. The coordination number variation during cycling load was considered to be responsible for this phenomenon. Induced anisotropy was observed, and it could be explained by deviatoric fabric analysis. © 2010 ASCE.
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