Publications
224 results found
Guo L, Latham J-P, Xiang J, 2014, Numerical simulation of breakages of concrete armour units using a three-dimensional fracture model in the context of the combined finite-discrete element method, Computers and Structures, Vol: 146, Pages: 117-142, ISSN: 0045-7949
Lei Q, Latham J-P, Xiang J, et al., 2014, Effects of geomechanical changes on the validity of a discrete fracture network representation of a realistic two-dimensional fractured rock, International Journal of Rock Mechanics and Mining Sciences, Vol: 70, Pages: 507-523, ISSN: 0020-7624
This paper aims to examine the validity of the discrete fracture network (DFN) method in representing a realistic two-dimensional fractured rock in terms of their geomechanical response to in-situ stresses and hydraulic behaviour in a steady state fluid field. First, a real fracture network is extracted from the geological map of an actual rock outcrop, which is termed the analogue fracture network (AFN). Multiple DFN realisations are created using the statistics of the analogue pattern. A conductivity parameter that was found to have a linear relationship with the conductivity of 2D fracture networks is included to further enhance network similarity. A series of numerical experiments are designed with far-field stresses applied at a range of angles to the rock domains and their geomechanical response is modelled using the combined finite-discrete element method (FEMDEM). A geomechanical comparison between the AFN and its DFN equivalents is made based on phenomena such as heterogeneity of fracture-dependent stress contours, sliding between pre-existing fracture walls, coalescence of propagating fractures and variability of aperture distribution. Furthermore, an indirect hydro-mechanical (HM) coupling is applied and the hydraulic behaviour of the porous rock models is investigated using the hybrid finite element-finite volume method (FEFVM). A further comparison is conducted focusing on the hydraulic behaviour of the AFN and DFNs under the effects of geomechanical changes. The results show that although DFNs may represent an AFN quite well for fixed mechanical conditions, such a representation may not be dependable if mechanical changes occur.
Lei Q, Latham J-P, Xiang J, et al., 2014, Representation of large scale network geometry with realisticapertures determined by mesoscale geomechanical modelling of a natural fracture system, 48th US Rock Mechanics/Geomechanics Symposium
Latham JP, Xiang J, Anastasaki E, et al., 2014, Numerical modelling of forces, stresses and breakages of concrete armour units, ISSN: 0161-3782
Numerical modelling has the potential to probe the complexity of the interacting physics of rubble mound armour systems. Through forward modelling of armour unit packs, stochastic variables such as unit displacement and maximum contact force per unit during an external oscillatory disturbance can be predicted. The combined finite-discrete element method (FEMDEM) is a multi-body method ideally suited to model the behaviour of the armour layer system and the stresses generated within complex shape units. In this paper we highlight the latest developments made with the application of FEMDEM technology to breakwater modelling including realistic rock underlayer and concrete unit layer topologies, maximum contact force distributions, internal unit stresses, fracture and unit breakages. Finally, fully coupled wave and multi-body armour unit motion with internal dynamic stress generation is illustrated.
Lei Q, Latham JP, Xiang J, et al., 2014, Representation of large scale network geometry with realistic apertures determined by mesoscale geomechanical modelling of a natural fracture system, 48th US Rock Mechanics / Geomechanics Symposium
Lei Q, Latham JP, Xiang J, et al., 2014, Coupled FEMDEM-DFN model for characterising thestress-dependent permeability of an anisotropic fracture system, 1st International Conference on Discrete Fracture Network Engineering
Anastasaki E, Xiang J, Latham JP, 2014, BUILDING CONCRETE UNIT ARMOURED BREAKWATERS IN A NUMERICAL MODEL ENVIRONMENT - A NEW PLACEMENT TECHNIQUE, Coasts, Marine Structures and Breakwaters 2013: From Sea to Shore - Meeting the Challenges of the Sea
Vire A, Jiang J, Piggott MD, et al., 2014, Towards the Numerical Modelling of Floating Offshore Renewables, Fluid-Structure-Sound Interactions and Control, Editors: Zhou, Yang, Huang, Hodges, Publisher: Springer Berlin Heidelberg, Pages: 413-417, ISBN: 978-3-642-40370-5
Vire A, Xiang J, Piggott MD, et al., 2014, Towards the Numerical Modelling of Floating Offshore Renewables., Fluid-Structure-Sound Interactions and Control, Publisher: Springer Berlin Heidelberg, Pages: 413-417
Guo L, Latham J-P, Xiang J, et al., 2013, A numerical investigation of fracture pattern and fracture aperturedevelopment in multi-layered rock using a combined finite-discrete element method, 47th US Rock Mechanics/Geomechanics Symposium
Lei Q, Latham J-P, Xiang J, et al., 2013, A geomechanical comparison between a naturally fractured rockmass and its DFN equivalent based on FEMDEM simulation, 3rd ISRM SINOROCK Symposium, Pages: 397-402
Lei Q, Latham JP, Xiang J, et al., 2013, A geomechanical comparison between a naturally fractured rock mass and its DFN equivalent based on FEMDEM simulation, Rock Characterisation, Modelling and Engineering Design Methods, Pages: 397-402, ISBN: 9781138000575
This paper presents a comparison between natural and stochastic fracture systems in terms of their geomechanical response to in-situ stresses. An analogue fracture network (AFN) is extracted from the geological map of a limestone outcrop. A corresponding discrete fracture network (DFN) is generated using the statistics obtained from the analogue pattern, to ensure the two networks share the same statistical characteristics. The geomechanical response is modelled using the combined finite-discrete element method (FEMDEM). A series of numerical experiments is designed with far-field stresses applied at a range of angles to the rock domain. A comparison between the natural fracture system and its DFN equivalent is made based on phenomena such as fracture-dependent stress heterogeneity, re-activation of pre-existing fractures, new crack propagation and variability of aperture distribution. This study addressed the validity of using the DFN approach for geomechanical modelling of fractured rock masses and also has implications for flow simulations.
Latham J-P, Anastasaki E, Xiang J, 2013, New modelling and analysis methods for concrete armour unit systems using FEMDEM, Coastal Engineering, Vol: 77, Pages: 151-166
Rubble mound breakwaters armoured with concrete units rely on collective behaviour between adjacent concrete armour units but existing largely empirical approaches have been unable to provide a detailed understanding of how these gigantic granular systems work. The problem has been that current methods cannot investigate the interdependence of hydraulic and structural stability at the scale of individual units. Numerical methods have the potential to provide such answers but there are many challenges to overcome. We present a solution to the first major bottleneck concerning the solids modelling: the numerical creation of a breakwater trunk section of single layer concrete units with geometrical and mechanical properties that conform to realistic prototype structure placements. Positioning of units is achieved with a new versatile software tool, POSITIT, which incorporates user-defined deposition variables and the initial positioning grid necessary to achieve the required design packing densities. The code Y3D, based on the combined finite-discrete element method, FEMDEM, solves the multi-body mechanics of the problem. First, we show numerically constructed breakwater sections with armour layers of 8 m3 CORE-LOC™ units placed on rock underlayers. The numerically-generated packs are deemed acceptable when examined according to a range of criteria indicative of acceptably placed armour layers, as set by concrete unit designers. Breakwater sections with packing densities ranging from 0.59 to 0.63 are then created. Using a set of analysis tools, local variation in packing density as an indicator of heterogeneity, centroid spacing, unit contacts and orientation of unit axes are presented, together with mechanical information showing the variation in contact forces. For these five packs examined, an increasingly tighter pack was associated with a steady increase in coordination number and a more steeply and accelerating increase in average maximum contact force per
Guo L, Latham JP, Xiang J, et al., 2013, A Numerical Investigation of Fracture Pattern and Fracture Aperture Development in Multi-layered Rock using a Combined Finite-Discrete Element Method, 47th US Rock Mechanics/Geomechanics Symposium, Publisher: American Rock Mechanics Association
Karantzoulis N, Xiang J, Izzuddin B, et al., 2013, NUMERICAL IMPLEMENTATION OF PLASTICITY MATERIAL MODELS IN THE COMBINED FINITE-DISCRETE ELEMENT METHOD AND VERIFICATION TESTS, DEM6 - International Conference on DEMs, Pages: 319-323
Until recently the combined finite-discrete element method (FEMDEM) has been usedonly with elastic constitutive models. In this paper the implementation of plasticity in thefully three-dimensional FEMDEM code (Y3D) is discussed. After setting up the adoptedgeneral governing equations of the problem, two different numerical verification tests arepresented. Favourable results show the successful implementation and demonstrate thepotential of the developed approach.
Xiang J, Latham JP, Vire A, et al., 2013, NUMERICAL MODELLING OF WAVE – RUBBLE MOUNDBREAKWATER INTERACTION, DEM6 - International Conference on DEMs, Pages: 426-431
Two new approaches for Fluid-Structure Interaction (FSI) are presented. One approach is the socalled the immersed body method in which the combined Finite-Discrete Element Method (FEMDEM) that deals with solids interactions is coupled to other modelling technologies e.g. CFD, interface tracking, wave models, porous media etc. Another approach is to couple FEMDEM with a new wave proxy which treats wave motion as cyclic loading. This approach is capable of simulating a representative part of a breakwater trunk at full scale.
Latham JP, Xiang J, Anastasaki E, et al., 2013, HOW DO RUBBLE BREAKWATERS SURVIVE WAVE ATTACK? CHALLENGES FOR A FEMDEM/CFD MODEL SOLUTION, Colorado School of Mines, 6th International Conference on Discrete Element Methods (DEM6), Pages: 42-48, ISSN: 0010-1745
Rubble-mound breakwaters are mainly designed using empirical equations, scaled hydraulics laboratory test models and precedent practice. Detailed understanding of the hydraulic and contact forces and stresses governing whether they survive or fail under wave action remains elusive. Numerical modeling has the potential to probe the complexity of the interacting physics of this problem. The combined finite-discrete element method is found to give remarkable insights into the behavior of the deformable granular solid skeleton and stress generation within units. Fluid-structure interaction (FSI) models are also required. Multi-body dynamics with free surface capture and numerical wave tanks (NWT) to drive and reproduce storm-wave conditions are needed. This paper discusses some of these numerical modeling challenges for coastal and ocean engineers in the context of concrete unit armoured breakwaters and highlights an approach that focusses on achieving meaningful solids representation with FEMDEM prior to coupling with an adaptive mesh CFD code, Fluidity.
VirĂ© A, Xiang J, Milthaler F, et al., 2012, Modelling of fluid–solid interactions using an adaptive mesh fluid model coupled with a combined finite–discrete element model, Ocean Dynamics
Sakai M, Takahashi H, Pain CC, et al., 2012, Study on a large-scale discrete element model for fine particles in a fluidized bed, ADVANCED POWDER TECHNOLOGY, Vol: 23, Pages: 673-681, ISSN: 0921-8831
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- Citations: 106
Latham JP, Xiang J, Belayneh M, et al., 2012, Modelling stress-dependent permeability in fractured rock including effects of propagating and bending fractures, International Journal of Rock Mechanics and Mining Sciences, Vol: 57, Pages: 100-112
Latham JP, Anastasaki E, Xiang J, 2012, A FEMDEM NUMERICAL MODEL STUDY OF RUBBLE-MOUND STRUCTURES ARMOURED WITH CONCRETE ARMOUR UNITS
Viré A, Xiang J, Milthaler F, et al., 2012, Modelling of fluid-solid interactions using an adaptive-mesh fluid model coupled with a combined finite-discrete element model, Ocean Dynamics, Vol: 62, Pages: 1487-1501
Latham J, Xiang J, Latham JP, et al., 2012, COUPLED FLUIDITY/Y3D TECHNOLOGY AND SIMULATION TOOLS FOR NUMERICAL BREAKWATER MODELLING., 33rd International Conference on Coastal Engineering
Latham JP, Guo L, Wang X, et al., 2011, Modelling the evolution of fractures using a combined FEM-DEM numerical method, Harmonising Rock Engineering and the Environment, Pages: 250-251, ISBN: 9780415804448
xiang J, Latham J-P, Harrison JP, 2011, A Numeric Simulation of Rock Avalanches Using the Combined Finite-Discrete Element Method,FEMDEM, 44th US Rock Mechanics Symposium and 5th U.S.-Canada Rock Mechanics Symposium, Pages: 921-927
Harrison JP, Xiang J, Latham JP, 2011, Stress Heterogeneity in a Fractured Rock Mass Modelled with the Combined Finite-DiscreteElement Method, 44th US Rock Mechanics Symposium and 5th U.S.-Canada Rock Mechanics Symposium, Pages: 1051-1056
Xiang J, Latham J-P, Zimmer D, et al., 2011, Modelling breakwater armour layers and the dynamic response of armour units., 6th International Conference on Coastal Structures
Milthaler F, Xiang J, Pavlidis D, et al., 2011, The immersed body method combined with mesh adaptivity for solid-fluid coupling, 6th International Conference on Coastal Structures
Latham J-P, Guo L, Wang X, 2011, Modelling the Evolution of Fractures using a Combined FEMDEM Numerical Method, 12th International Congress on Rock Mechanics, Harmonising Rock Engineering and the Environment, Publisher: ISRM Digital Library, One Petro
Latham J-P, Xiang J, Harrison JP, et al., 2011, Development of Virtual Geoscience Simulation Tools, VGeST for irregular blocky rock applications in rock engineering using the combined finite discrete element method, FEMDEM, 44th US Rock Mechanics Symposium and 5th U.S.-Canada Rock Mechanics Symposium, Publisher: Curran Associates, Pages: 965-976
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