An Experimental Investigation of the Brazilian Tensile Strength and Failure Patterns of Laminated Sandstones

Khanlari, Gholamreza; Rafiei, Behrouz; Abdilor, Yasin

doi:10.1007/s00603-014-0576-y

Cited by 78 publications

(33 citation statements)

References 11 publications

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“…A number of researchers have carried out studies on the effect of anisotropic properties on the Brazilian tensile strength (Khanlari et al 2014a(Khanlari et al & 2014bTan et al 2014). 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.…”

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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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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“…Their results showed that the degree of anisotropy played an important role in the tensile strength, while anisotropic gneiss and slate revealed a strong dependence of the tensile strength on the specimen orientation related to the loading direction. Furthermore, Khanlari et al [12] carried out a series of Brazilian test for three types of sandstones with different average number of lamination boundaries per cm. Based on the test results, two major modes of failure were observed in the laminated sandstone specimens.…”

Section: Introductionmentioning

confidence: 99%

Particle flow study on strength and meso-mechanism of Brazilian splitting test for jointed rock mass

Yang

Huang

2014

Acta Mech Sin

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A discrete element method (DEM) called particle flow code (PFC 2D ) was used to construct a model for Brazilian disc splitting test in the present study. Based on the experimental results of intact Brazilian disc of rock-like material, a set of micro-parameters in PFC 2D that reflected the macro-mechanical behavior of rock-like materials were obtained. And then PFC 2D was used to simulate Brazilian splitting test for jointed rock mass specimens and specimen containing a central straight notch. The effect of joint angle and notch angle on the tensile strength and failure mode of jointed rock specimens was detailed analyzed. In order to reveal the meso-mechanical mechanism of crack coalescence, displacement trend lines were applied to analyze the displacement evolution during the crack initiation and propagation. The investigated conclusions can be described as follows.(1) The tensile strength of jointed rock mass disc specimen is dependent to the joint angle. As the joint angle increases, the tensile strength of jointed rock specimen takes on a nonlinear variance. (2) The tensile strength of jointed rock mass disc specimen containing a central straight notch distributes as a function of both joint angle and notch angle. (3) Three major failure modes, i.e., pure tensile failure, shear failure and mixed tension and shear failure mode are observed in jointed rock mass disc specimens under Brazilian test. (4) The notch angle and joint angle play important roles on crack initiation and propagation characteristics of jointed rock mass disc specimen containing a central straight notch under Brazilian test.

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“…This type of diagram helps to identify failure mode zones, depending on either the rock's properties or the load‐weak plane's orientation angle. Khanlari et al used the isotropic ISRM BT expression to obtain the brazilian tensile strength (BTS) on laminated sandstones. Varying the load angle, they analyzed the percentage of fracture on the weak direction or in the matrix.…”

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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An Experimental Investigation of the Brazilian Tensile Strength and Failure Patterns of Laminated Sandstones

Cited by 78 publications

References 11 publications

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

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

Particle flow study on strength and meso-mechanism of Brazilian splitting test for jointed rock mass

Fracture behavior of transversely isotropic rocks with discrete weak interfaces

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