Experimental, numerical and analytical studies on tensile strength of rocks

Erarslan, N.; Williams, David J.

doi:10.1016/j.ijrmms.2011.11.007

Cited by 138 publications

(41 citation statements)

References 14 publications

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“…Figure shows the stress distributions using horizontal and shear components obtained from each numerical element. Note that since the global coordinates are horizontal ( x ) and vertical ( y ) axes [e.g., Erarslan and Williams , ; Li and Wong , ; Dan and Konietzky , ; Tan et al ., ], the maximum tensile stress is not exactly aligned to the horizontal direction. The phase field values of 0.0 to 0.1 are used to reflect the damaged zone (white spaces) that includes both crack and severely broken parts.…”

Section: Resultsmentioning

confidence: 99%

Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Sun

Ingraham

et al. 2017

JGR Solid Earth

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For assessing energy‐related activities in the subsurface, it is important to investigate the impact of the spatial variability and anisotropy on the geomechanical behavior of shale. The Brazilian test, an indirect tensile‐splitting method, is performed in this work, and the evolution of strain field is obtained using digital image correlation. Experimental results show the significant impact of local heterogeneity and lamination on the crack pattern characteristics. For numerical simulations, a phase field method is used to simulate the brittle fracture behavior under various Brazilian test conditions. In this study, shale is assumed to consist of two constituents including the stiff and soft layers to which the same toughness but different elastic moduli are assigned. Microstructural heterogeneity is simplified to represent mesoscale (e.g., millimeter scale) features such as layer orientation, thickness, volume fraction, and defects. The effect of these structural attributes on the onset, propagation, and coalescence of cracks is explored. The simulation results show that spatial heterogeneity and material anisotropy highly affect crack patterns and effective fracture toughness, and the elastic contrast of two constituents significantly alters the effective toughness. However, the complex crack patterns observed in the experiments cannot completely be accounted for by either an isotropic or transversely isotropic effective medium approach. This implies that cracks developed in the layered system may coalesce in complicated ways depending on the local heterogeneity, and the interaction mechanisms between the cracks using two‐constituent systems may explain the wide range of effective toughness of shale reported in the literature.

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Section: Resultsmentioning

confidence: 99%

Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Sun

Ingraham

et al. 2017

JGR Solid Earth

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“…Based on the assessment of the influence of strength anisotropy on the measured peak strength for four different types of rock samples in the Brazilian test, Dan et al (2013) deemed that: 1) the degree of anisotropy has a strong influence on the measured peak strength; 2) the orientation of the sample in relation to the loading direction is not important for nearly-isotropic materials; and 3) strongly anisotropic materials show a strong dependence of the peak strength on the sample orientation relative to the loading direction. Erarslan & Williams (2012) pointed out that there is substantially higher tensile stress concentration at the center of a disk with a pre-existing crack than in a disk without a pre-existing crack.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

Wang¹

2015

Archives of Mining Sciences

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For coal mine ground control issues, it is necessary to propose a failure criteria accounting for the transversely isotropic behaviors of rocks. Hence, it is very helpful to provide experimental data for the validation of the failure criteria. In this paper, the method for preparing transversely isotropic specimens and the scheme of the Brazilian tensile strength test are presented. Results obtained from Brazilian split tests under dry and water-saturated conditions reflect the effect of the development direction β of the structural plane, such as the bedding fissure, on the tensile strength, ultimate displacement, failure mode, and the whole splitting process. The results show that the tensile strength decreases linearly with increasing β. The softening coefficient of the tensile strength shows a sinusoidal function. The values of the slope and inflection point for the curve vary at the different stages of the Brazilian test. The failure mode of the rock specimen presented in this paper generally coincides with the standard Brazilian splitting failure mode. Based on the test results, the major influencing factors for the Brazilian splitting strength are analyzed and a mathematical model for solving the Brazilian splitting strength is proposed. The findings in this paper would greatly benefit the coal mine ground control studies when the surrounding rocks of interest show severe transversely isotropic behaviors.Keywords: Brazilian split test; Dry and water saturation; Bedding fissure; Strength coefficient; Coal mine ground control W związku z zagadnieniami ochrony powierzchni w kopalniach węgla, konieczne jest opracowanie odpowiednich kryteriów klasyfikacji uszkodzeń skał uwzględniających ich poprzeczną izotropowość. Pomocnym jest także dostarczenie danych eksperymentalnych niezbędnych do walidacji kryteriów uszkodzeń. W pracy tej zaproponowano metodę przygotowywania próbek wykazujących izotropowość poprzeczną, omówiono także sposób przeprowadzania testu na rozciąganie metodą brazylijską. Wyniki testu uzyskane na sucho oraz w warunkach nasycenia próbki wodą wskazują wpływ kierunku rozwoju β płaszczyzny strukturalnej (np. płaszczyzn spękań) na wytrzymałość próbki na rozciąganie, maksymalne przemieszczenia, rodzaj uszkodzenia oraz przebieg procesu pękania. Wyniki testu wskazują, że wytrzymałość na rozciąganie maleje liniowo wraz ze wzrostem wartości β. Współczynnik mięknienia próbki w trakcie próby wytrzymałościowej na rozciąganie ma przebieg krzywej sinusoidalnej. Wartości kąta nachylenia oraz punkt przegięcia krzywej różnią się dla poszczególnych etapów próby wytrzymałościowej. Tryb uszkodzeń próbek skalnych przedstawiony w artykule zasadniczo pozostaje w zgodzie z typowymi odkształceniami rejestrowanymi w trakcie testu metodą brazylijską. W oparciu o wyniki eksperymentu, przeanalizowano główne czynniki wpływające na wytrzymałość próbek na rozciąganie i zaproponowano odpowiedni model matematyczny do obliczania wytrzymałości. Wyniki przedstawione w artykule stanowią poważny przyczynek do badań stabilności gruntu...

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“…They obtained a well‐correlated solution between their model and experimental results. Erarslan and Williams analyzed experimentally and numerically the loading contact problem associated with the BT of Brisbane tuff. It was concluded that BTS is strongly dependent on the type of diametrical loading.…”

Section: Introductionmentioning

confidence: 99%

Fracture behavior of transversely isotropic rocks with discrete weak interfaces

Celleri

Sánchez²,

Otegui

2018

Num Anal Meth Geomechanics

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Summary Anisotropic rocks have gained increasing attention due to the development of unconventional oil and gas reservoirs. This type of reservoir requires complex engineering procedures from drilling to completion, and the mechanical properties of the rocks play a significant role. One of the most important characteristics of unconventional formations is the presence of well‐defined layers, which greatly modify both elastic and fracture properties of the rocks. Rock elastic response is direction dependent, commonly described as vertically transversely isotropic (VTI), meaning that there is an isotropic plane of symmetry with respect to the vertical direction. Between layers, calcitic veins or ash beds alter the rock's properties substantially. These interfaces, which can have low or no cohesion at all, act as preferential planes for fracture nucleation and propagation, affecting the rocks strength. In this work, the fracture behavior of VTI rocks with weak interfaces is studied using numerical simulations of brazilian tests. A hybrid discontinuous Galerkin–cohesive zone model was used to simulate fracture initiation and propagation on discs in the presence of weak planes. With this approach, we determined the effective brazilian test strength of the rocks under different conditions, namely, relative angles between layers and the loading direction, densities, and cohesion of weak interfaces. Shear reactivation of the interfaces is analyzed using the Mohr‐Coulomb failure criterion and Mohr circles.

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Experimental, numerical and analytical studies on tensile strength of rocks

Cited by 138 publications

References 14 publications

Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Effects of spatial heterogeneity and material anisotropy on the fracture pattern and macroscopic effective toughness of Mancos Shale in Brazilian tests

Experimental Study On The Effect Of Micro-Cracks On Brazilian Tensile Strength

Fracture behavior of transversely isotropic rocks with discrete weak interfaces

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