The impact of porosity and crack density on the elasticity, strength and friction of cohesive granular materials : insights from DEM modelling

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Title: The impact of porosity and crack density on the elasticity, strength and friction of cohesive granular materials : insights from DEM modelling
Authors: Schöpfer, Martin P. J.
Abe, Steffen
Childs, Conrad
Walsh, John J.
Permanent link: http://hdl.handle.net/10197/3027
Date: Feb-2009
Abstract: Empirical rock properties and continuum mechanics provide a basis for defining relationships between a variety of mechanical properties, such as strength, friction angle, Young’s modulus, Poisson’s ratio, on the one hand and both porosity and crack density, on the other. This study uses the Discrete Element Method (DEM), in which rock is represented by bonded, spherical particles, to investigate the dependence of elasticity, strength and friction angle on porosity and crack density. A series of confined triaxial extension and compression tests was performed on samples that were generated with different particle packing methods, characterised by differing particle size distributions and porosities, and with different proportions of pre-existing cracks, or uncemented grain contacts, modelled as non-bonded contacts. The 3D DEM model results demonstrate that the friction angle decreases (almost) linearly with increasing porosity and is independent of particle size distribution. Young’s modulus, strength and the ratio of unconfined compressive strength to tensile strength (UCS/T) also decrease with increasing porosity, whereas Poisson’s ratio is (almost) porosity independent. The pre-eminent control on UCS/T is however the proportion of bonded contacts, suggesting that UCS/T increases with increasing crack density. Young’s modulus and strength decrease, while Poisson’s ratio increases with increasing crack density. The modelling results replicate a wide range of empirical relationships observed in rocks and underpin improved methods for the calibration of DEM model materials.
Funding Details: Science Foundation Ireland
Type of material: Journal Article
Publisher: Elsevier
Copyright (published version): 2008 ElsevierLtd.
Keywords: Discrete element method;Porosity;Crack density;Friction;Failure envelope
Subject LCSH: Porosity
Rocks--Cracking
Friction
Fracture mechanics
DOI: 10.1016/j.ijrmms.2008.03.009
Language: en
Status of Item: Peer reviewed
Appears in Collections:Earth Sciences Research Collection

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