Publications
74 results found
Paluszny A, Tang XH, Zimmerman RW, 2012, A Multi-modal Approach to 3D Fracture And Fragmentation of Rock Using Impulse-Based Dynamics And the Finite Element Method, Publisher: American Rock Mechanics Association
ABSTRACT:A numerical method combining the finite element method (FEM) and impulse-based dynamics is proposed for the simulation of 3D fracture and fragmentation. As opposed to existing methods, fragments are not represented as a conglomeration of primitive shapes; instead, their geometry is represented using solid modeling techniques. This allows for continuum-mechanics-based fracture propagation analysis to be carried out within each fragment, with fragment interaction and movement simulated using impulse-based dynamics. This approach models multi-body interaction of non-convex 3D objects which fall, collide, and fragment using impulse-based dynamics, as opposed to a penalty-based method. Instead, object trajectories are used to estimate time-of-impact, and contact between bodies is modeled by collisions at contact locations. This approach allows material properties to be explicitly defined at the macro-scale. A 3D fracture engine models fracture propagation in the individual 3D continua based on local stress intensity factor measurements using the reduced virtual integration technique, as well as decoupled geometry and mesh representation, and on the evaluation of local failure and propagation criteria. Fractures that reach free boundaries lead to further fragmentation. The framework, presented as a multi-modal toolkit, is suitable for meso-scale simulations, and is demonstrated by a mining-specific block caving application. 1. INTRODUCTIONFragmentation simulation involves capturing two main processes: damage and cracking of single bodies, and dynamics/collision between fragments. The analysis of damage and cracking in single bodies includes challenges such as defining initial material properties and rock heterogeneities, crack nucleation, and propagation of multiple cracks. Modeling collisions between fragments includes capturing processes such as collision detection, force transfer due to impact and compression, and energy loss during collision. Challenges inclu
Zimmerman RW, Paluszny A, 2012, Some New Developments in Modelling the Failure, Fracture and Fragmentation of Rocks, Publisher: International Society for Rock Mechanics
ABSTRACTIn this paper, several new developments regarding the failure, fracture and fragmentation of rocks will be discussed. The first topic discussed is the development of true-triaxial failure criteria that involve all three principal stresses. The next topic is a new approach to modelling the propagation of cracks and fractures using accurate local calculations of the stress intensity factor. Lastly, a method for fracture-driven rock fragmentation with a velocity-dependent propagation law is discussed.
Iglauer S, Paluszny A, Pentland C, et al., 2011, Residual CO2 imaged with x-ray micro-tomography, Geophysical Research Letters, Vol: 38, ISSN: 1944-8007
Carbon capture and storage (CCS), where CO2 is injectedinto geological formations, has been identified as an importantway to reduce CO2 emissions to the atmosphere. While thereare several aquifers worldwide into which CO2 has beeninjected, there is still uncertainty in terms of the long‐termfate of the CO2. Simulation studies have proposed capillarytrapping – where the CO2 is stranded as pore‐space dropletssurrounded by water – as a rapid way to secure safe storage.However, there has been no direct evidence of pore‐scaletrapping. We imaged trapped super‐critical CO2 clusters ina sandstone at elevated temperatures and pressures,representative of storage conditions using computed micro‐tomography (m‐CT) and measured the distribution oftrapped cluster size. The clusters occupy 25% of the porespace. This work suggests that locally capillary trapping isan effective, safe storage mechanism in quartz‐richsandstones
Paluszny A, Zimmerman RW, 2011, Numerical simulation of multiple 3D fracture propagation using arbitrary meshes, Computer Methods in Applied Mechanics and Engineering, Vol: 200, Pages: 953-966
Nick H, Paluszny A, Matthai SK, 2011, Role of geomechanically grown fractures on dispersive transport in heterogeneous geological formations, Physical Review E (Statistical, Nonlinear, and Soft Matter Physics)
Paluszny A, Matthai SK, 2010, Impact of fracture development on the effective permeability of porous rocks as determined by 2D discrete fracture growth modeling., Journal of Geophysical Research, Vol: 115
Coumou D, Driesner T, Geiger S, et al., 2009, High-resolution three-dimensional simulations of mid-ocean ridge hydrothermal systems, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 114, ISSN: 2169-9313
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Paluszny A, 2009, Numerical modelling of fracture propagation and its implications for fluid flow, PhD Thesis
Paluszny A, Matthai SK, 2009, Numerical modeling of discrete multi-crack growth applied to pattern formation in geological brittle media., International Journal of Solids and Structures, Vol: 46, Pages: 3383-3397
Nick HM, Paluszny A, Matthai SK, et al., 2009, Influence of fracture aperture on solute transport in porous media, Geo Halifax
Paluszny A, Matthai SK, 2008, Impact of Fracture Development on Effective Permeability as determined by Geomechanical Modeling, American Rock Mechanics Association Symposium
Paluszny A, Matthai SK, 2008, Numerical simulation of geomechanic fracture networks: application to measuring effective permeability variability, Publisher: American Rock Mechanics Association
ABSTRACT: Fracture networks exert a strong influence on flow patterns in the subsurface. We develop a geomechanics-based finite-element models and generate fracture patterns incrementally while studying their impact on fluid flow at each development stage below and above the fracture percolation threshold for a given observation area. Our model - for the first time - also takes into account flow in the porous rock matrix so that its results are applicable to fractured porous media as opposed to crystalline rocks only. The algorithmic approach is iterative and simulates sub-critical quasi-static crack propagation. Initially, a finite set of randomly oriented flaws with varying size populate the matrix. We assume the matrix to be homogeneous, isotropic, and linear elastic. Fracture propagation is based on a combination of failure criteria including the stress intensity factors at the crack tip and a fracture growth index. The propagation angle is determined by the maximum circumferential stress method. Straight and curved fracture geometries are generated by keeping track of the fracture-matrix interfaces on a progressively refined and coarsened mesh. Fracture aperture is an emergent property of the model. Fracture arrest, closure, coalescence, and intersection are handled geometrically by disallowing displacement over fracture boundaries, and merging of polygonal fracture representations. For selected stages of fracture development we compute the effective permeability of the model taking into account the aperture variations. The parallel plate model is used to compute fracture permeability from aperture. The results we obtain depend on the number of initial flaws and the fracture growth rate exponent which determines the length distribution of the evolving fracture set. For a small number of fractures we observe a gradual increase in the model permeability up to the percolation threshold followed by a one-order of magnitude increase as the model begins to percolate.
Matthai SK, Geiger S, Roberts SG, et al., 2007, Numerical simulation of multi-phase fluid flow in structurally complex reservoirs, Structurally Complex Reservoirs, Editors: Jolley J, Barr D, walsh J, Knipe J, London, Publisher: Geological Society, London, Pages: 405-429
Paluszny A, Matthai SK, Hohmeyer M, 2007, Hybrid finite element-finite volume discretization of complex geologic structures and a new simulation workflow demonstrated on fractured rocks, Geofluids, Vol: 7, Pages: 186-208
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