Influence of specimen shape deviations on uniaxial compressive strength of limestone and similar rocks

Cvitanović, Nataša Štambuk; Nikolić, Mijo; Ibrahimbegović, Adnan

doi:10.1016/j.ijrmms.2015.10.008

Cited by 18 publications

(7 citation statements)

References 20 publications

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“…The 3D lattice model from [9] was used to confirm the experimental findings of unavoidable, but insufficiently investigated influences of the test specimen shape deviations on unconfined compressive strength appearing in testing which can significantly affect the results [79]. It is well known from laboratories that the inaccuracies of the cylindrical specimens resulting with deviations from flatness, perpendicularity and parallelism lead to the reduction of strength and various moduli.…”

Section: Influence Of Specimen Shape Deviationsmentioning

confidence: 99%

“…In the presented research [79], ninety intact rock cylindrical test specimens intentionally constructed with initial shape deviations are included. Some of them are also constructed and tested with the numerical model to provide more insight into experimental results and additionally verify the hypothesis.…”

Section: Influence Of Specimen Shape Deviationsmentioning

confidence: 99%

“…31 Representative numerical rock specimens from the observed groups with initial shape deviation. Taken from [79] 1 3…”

Section: Lattice Element Models For Transport Processesmentioning

confidence: 99%

See 2 more Smart Citations

Lattice Element Models and Their Peculiarities

Nikolić

Karavelić

Ibrahimbegović

et al. 2017

Arch Computat Methods Eng

105

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Section: Influence Of Specimen Shape Deviationsmentioning

confidence: 99%

Section: Influence Of Specimen Shape Deviationsmentioning

confidence: 99%

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Lattice Element Models and Their Peculiarities

Nikolić

Karavelić

Ibrahimbegović

et al. 2017

Arch Computat Methods Eng

105

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“…The full explanation of the 2D and 3D models presented can be found in the literature [11][12]. The presented lattice element model can also be used to solve problems brought about by the failure of fluid-saturated, fractured, poro-plastic materials, using the Biot porous media approach [13], or even to examine the influence of rock specimen shape deviations on uniaxial compressive strength [14]. …”

Section: Embedded Strong Discontinuities In the Lattice Element Modelmentioning

confidence: 99%

Discrete Lattice Element Approach for Rock Failure Modeling

Nikolić

Ibrahimbegović

Miščević

2017

e-GFOS

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This paper presents the 'discrete lattice model', or, simply, the 'lattice model', developed for rock failure modeling. The main difficulties in numerical modeling, namely, those related to complex crack initiations and multiple crack propagations, their coalescence under the influence of natural disorder, and heterogeneities, are overcome using the approach presented in this paper. The lattice model is constructed as an assembly of Timoshenko beams, representing the cohesive links between the grains of the material, which are described by Voronoi polygons. The kinematics of the Timoshenko beams are enhanced by the embedded strong discontinuities in their axial and transversal directions so as to provide failure modes I, II, and III. The model presented is suitable for meso-scale rock simulations. The representative numerical simulations, in both 2D and 3D settings, are provided in order to illustrate the model's capabilities. Keywords: discrete model; lattice model; embedded strong discontinuity DISKRETNI PRISTUP ZA MODELIRANJE SLOMA U STIJENI Sažetak: U ovome radu predstavljen je diskretni rešetkasti model razvijen za simuliranje sloma u stijeni. Poteškoće koje se javljaju u numeričkim modelima kontinuuma, kao što su inicijacija pukotine, propagacija više pukotina, njihovo srastanje i utjecaj heterogenosti stijene na mehanizam sloma, uspješno su implementirane u prezentirani model. Model je baziran na Timoshenkovim gredama koje predstavljaju kohezivne veze između zrna stijene koji su modelirani Voronoi ćelijama. Formulacija Timoshenkovih greda je poboljšana ugradnjom jakih diskontinuiteta u uzdužnom i poprečnom smjeru grede za simulaciju sloma zbog otvaranja u vlaku ili klizanja u posmiku. Predstavljeni model je razvijen za simulacije stijene na mezoskali. Numeričke simulacije 2D i 3D uzoraka prikazane su u prezentiranome radu.Ključne riječi: diskretni model; rešetkasti model; jaki diskontinuitiet

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“…This cumulative research has been published in [Stambuk-Cvitanovic et al, 2015], while the numerical aspects are covered in the next sections of this Chapter. This includes the methodology of how to deal with geometrical micro-deviations of the intact specimens and corresponding numerical results.…”

Section: Research Motivationmentioning

confidence: 99%

Rock Mechanics, Failure Phenomena with Pre-Existing Cracks and Internal Fluid Flow through Cracks

Nikolić¹

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This thesis deals with the problem of localized failure in rocks, which occurs often in civil engineering practice like in dam failure, foundation collapse, stability of excavations, slopes and tunnels, landslides and rock falls. The risk of localized failure should be better understood in order to be prevented. The localized failure in rocks is usually characterized by a sudden and brittle failure without warning in a sense of larger and visible deformations prior to failure. This happens also under the strong influence of material heterogeneities, pre-existing cracks and other defects. The three novel numerical models, incorporating the localized failure mechanisms, heterogeneity of rock and pre-existing cracks and other defects, are presented in this thesis. First model deals with 2D plane strain two-phase rock composite, where stronger phase represents the intact rock and weaker phase initial defects. Second model represents the extension of the previous model towards the 3D space, where full set of 3D failure mechanisms is considered. Heterogeneous properties are taken here through the random distribution and Gauss statistical variation of material properties. The latter model is also used for the analysis of intact rock core specimens geometrical shape deviations influencing the uniaxial compressive strength. Third model is a 2D, dealing with volumetric fluid-structure interaction and localized failure under the influence of fluid flow through the porous rock medium. The discrete beam lattice approach is chosen for general framework for three models, where Voronoi cells represent the rock grains kept together by Timoshenko beams as cohesive links. The enhanced kinematics characterized for embedded discontinuity approach is added upon standard kinematics of cohesive links. This serves for the macrocrack propagation in all failure modes and their combinations, between the rock grains. The fracture process zone formation followed by micro-cracks coalescence, preceding the localized failure, is considered as well. Fluid flow is governed by a Darcy law, while coupling conditions obey Biot’s theory of poroplasticity. The results of the numerical models were verified by the benchmarks available from literature in 2D case. The 3D model was validated against the experimental results conducted on 90 rock specimens, where even slight geometrical deviations of specimens are considered. Presentation of these models, as well as their implementation aspects are given in full detail. Embedded discontinuity concept and the local nature of enhancements required to capture the displacement discontinuities leads to the very efficient approach with static condensation of enhanced degrees of freedom and technique that can be efficiently incorporated into finite element code architecture.

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Influence of specimen shape deviations on uniaxial compressive strength of limestone and similar rocks

Cited by 18 publications

References 20 publications

Lattice Element Models and Their Peculiarities

Lattice Element Models and Their Peculiarities

Discrete Lattice Element Approach for Rock Failure Modeling

Rock Mechanics, Failure Phenomena with Pre-Existing Cracks and Internal Fluid Flow through Cracks

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