DEM analysis of the crack propagation in brittle clays under uniaxial compression tests

Vesga, L. F.; Vallejo, Luis E.; Lobo-Guerrero, Sebastián

doi:10.1002/nag.665

Cited by 62 publications

(26 citation statements)

References 14 publications

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“…In addition, the discrete element method (DEM) developed by Cundall and Strack (1979) has been applied to simulate growth of cracks in brittle clay specimens (Vesga et al 2008), showing good agreement with experimental results. The particle flow code (PFC) is a type of DEM, which is commercially available and has been applied to solve crack problems (Yoon 2007;Lee and Jeon 2011;Zhang and Wong 2012).…”

Section: Introductionmentioning

confidence: 91%

Numerical Simulation of Crack Growth and Coalescence in Rock-Like Materials Containing Multiple Pre-existing Flaws

Zhou

2014

Rock Mech Rock Eng

306

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A novel meshless numerical method, called general particle dynamics (GPD), is proposed to simulate samples of rock-like brittle heterogeneous material containing four preexisting flaws under uniaxial compressive loads. Numerical simulations are conducted to investigate the initiation, growth, and coalescence of cracks using a GPD code. An elasto-brittle damage model based on an extension of the Hoek-Brown strength criterion is applied to reflect crack initiation, growth, and coalescence and the macrofailure of the rock-like material. The preexisting flaws are simulated by empty particles. The particle is killed when its stresses satisfy the Hoek-Brown strength criterion, and the growth path of cracks is captured through the sequence of such damaged particles. A statistical approach is applied to model the heterogeneity of the rocklike material. It is found from the numerical results that samples containing four preexisting flaws may produce five types of cracks at or near the tips of preexisting flaws including wing, coplanar or quasi-coplanar secondary, oblique secondary, out-of-plane tensile, and out-of-plane shear cracks. Four coalescence modes are observed from the numerical results: tensile (T), compression (C), shear (S), and mixed tension/shear (TS). A higher load is required to induce crack coalescence in the shear mode (S) than the tensile (T) or mixed (TS) mode. It is concluded from the numerical results that crack coalescence occurs following the weakest coalescence path among all possible paths between any two flaws. The numerical results are in good agreement with reported experimental observations.

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Section: Introductionmentioning

confidence: 91%

Numerical Simulation of Crack Growth and Coalescence in Rock-Like Materials Containing Multiple Pre-existing Flaws

Zhou

2014

Rock Mech Rock Eng

306

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“…It successfully modeled the global failure of a rock specimen as well as local cracking at the flaw tips (Li et al, 2005;Tang et al, 2001;Tang and Kou, 1998). In addition, DEM (Discrete Element Method) developed by Cundall and Strack (1979) was used to simulate the cracking process in brittle clay specimens (Vesga et al, 2008) and revealed a good agreement with the experimental results. They used PFC 2D (Particle Flow Code in two Dimensions) which can reproduce the cracks directly by bond breakage between the circular particles instead of using fracture mechanics theories where complex mathematical equations relevant to the stress intensity factor and fracture toughness at the crack tips are implemented.…”

Section: Introductionmentioning

confidence: 94%

An experimental and numerical study of fracture coalescence in pre-cracked specimens under uniaxial compression

Lee

Jeon

2011

International Journal of Solids and Structures

645

221

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a b s t r a c tThis study presents crack initiation, propagation and coalescence at or near pre-existing open cracks or flaws in a specimen under uniaxial compression. The flaw geometry in the specimen was a combination of a horizontal flaw and an inclined flaw underneath. This flaw geometry is different from those reported in the previous studies, where a pair of parallel flaws was used. Three materials were used, PMMA (Poly Methyl MethAcrylate), Diastone (types of molded gypsum), and Hwangdeung granite. Crack initiation and propagation showed similar and different patterns depending on the material. In PMMA, tensile cracks initiated at the flaw tips and propagated to the tip of the other flaw in the bridge area. The cracks then coalesced at a point of the inclined flaw, which is affected by the flaw inclination angle. For Diastone and Hwangdeung granite, tensile cracks were observed followed by the initiation of shear cracks. Coalescence occurred mainly through the tensile cracks or tensile and shear cracks. Crack coalescence was classified according to the crack coalescence types of parallel flaws for overlapping flaw geometry in the past works. In addition, crack initiation and coalescence stresses in the double-flawed specimens were analyzed and compared with those in the single-flawed specimen. Numerical simulations using PFC 2D (Particle Flow Code in two dimensions) based on the DEM (Discrete Element Method) were carried out and showed a good agreement with the experimental results in the coalescence characteristics in Hwangdeung granite. These experimental and numerical results are expected to improve the understanding of the characteristics of cracking and crack coalescence and can be used to analyze the stability of rock and rock structures, such as the excavated underground openings or slopes, tunneling construction, where pre-existing cracks or fractures play a crucial role in the overall integrity of such structures.

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“…The circles represent individual particles, while the lines are gradients of particle motion. 7 Thus, nodes and anti-nodes of vibration modes can well be detected. Characteristic functions ψ 1 , ψ 2 , ψ 4 , ψ 5 , ψ 6 , ψ 8 , ψ 9 and ψ 12 are very similar to linear eigenmodes of transverse beam vibration.…”

Section: Karhunen-loève Decompositionmentioning

confidence: 97%

“…In addition, KL decomposition of the simulated motion of the DEM model also reveils symmetric and asymmetric forms of combined transversal and longitudinal motion, as captured by characteristic functions ψ 3 , ψ 7 , ψ 10 and ψ 11 . 7 The length of the lines represent the displacements qualitatively. …”

Section: Karhunen-loève Decompositionmentioning

confidence: 99%

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Reduction of discrete element models by Karhunen–Loève transform: a hybrid model approach

Glösmann

2009

Comput Mech

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The term "discrete element method" (DEM) in engineering science comprises various approaches to model physical systems by agglomerates of free particles. While shapes, sizes and properties of particles may vary, in most DEM models, particles are not confined by constraints, but subject to applied forces derived from potential fields and/or contact laws. This general approach allows for widespread use of DEM models for physical phenomena including gas dynamics, granular flow, fracture and impact analysis. However, its characteristic feature, combining particle restraints and forces into applied forces, does not only provide for flexible adaption of DEM to different physics, but also creates the most limiting restriction: Evaluation of the applied forces for each particle is computational expensive restraining the time sequence and sample size for numerical analyses. As an ansatz to circumvent this obstacle for a class of DEM models, we propose a model order reduction method based on coherency in the dynamics of particles. While initial flexibility of DEM is conserved, computational effort can be reduced significantly.

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DEM analysis of the crack propagation in brittle clays under uniaxial compression tests

Cited by 62 publications

References 14 publications

Numerical Simulation of Crack Growth and Coalescence in Rock-Like Materials Containing Multiple Pre-existing Flaws

Numerical Simulation of Crack Growth and Coalescence in Rock-Like Materials Containing Multiple Pre-existing Flaws

An experimental and numerical study of fracture coalescence in pre-cracked specimens under uniaxial compression

Reduction of discrete element models by Karhunen–Loève transform: a hybrid model approach

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