Strength criterion for rocks under compressive-tensile stresses and its application

Mingqing, You

doi:10.1016/j.jrmge.2015.05.002

Cited by 37 publications

(11 citation statements)

References 28 publications

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“…The variational trend of the strength can be represented by a bilinear model with slope K equal to 5.302 and 2.725 at lower and higher confining pressures, respectively. That is, the sensitivity of strength to confining pressure with lower P c is stronger than that with higher P c , which is consistent with the results of other researchers [56,57], because the low confining pressure does not induce the closure of all microcracks before triaxial loading and the remaining microcracks cause a decrease in the strength of the specimen. If the σ f -P c relationship is piecewise fitted by the Mohr-Coulomb criterion, the friction angles ϕ of the low-and high-P c zones are approximately 43°a nd 28°, respectively, and the corresponding shear failure angles oblique to the σ 3 direction are 66.5°and 59°.…”

Section: Deviatoricsupporting

confidence: 91%

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

et al. 2019

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Injecting CO 2 into a reservoir disturbs the geostress field, which leads to variations in the permeability of caprock and affects its sealing performance. In this paper, the evolution characteristics of the permeability of Yingcheng mudstone were experimentally studied during deviatoric compression under different confining pressures. As the confining pressure increased, the strength of the mudstone increased bilinearly, the angle between the fault and the maximum principle stress increased, and the fault became flatter. During compression, the permeability of mudstone first decreased and then increased and the turning point of the permeability was between the onset of dilatancy and the turning point of volumetric strain; when the fault formed, the permeability increased sharply and the fault-induced increment was reduced exponentially with increasing confining pressure. In addition, the mudstone transformed to the ductile failure mode when the effective confining pressure was greater than 35 MPa, which means that the permeability did not jump within a small strain. Finally, a practical strain-based model of permeability evolution that separately considers compaction and dilatancy was proposed, and the predicted permeability values were in good agreement with the experimental results. This study revealed the effect of confining pressure on permeability evolution during compression and can help evaluate the sealing ability of mudstone caprock.

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Section: Deviatoricsupporting

confidence: 91%

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

et al. 2019

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“…Compressive strength values of rock materials are generally 8 or more times higher than their tensile strength values [28][29][30]. The compressive stresses at the contact of the hole and the loading apparatus steel were found to be not enough high to cause an invalid failure in case of the contact angle of 50°.…”

Section: Discussionmentioning

confidence: 91%

“…Because the intermediate and minor stresses are respectively tensile and compressive stresses and have low values at the sidewalls, stress distribution can be practically considered as uniaxial for the location of the maximum tension. It is advantageous to have low level minor and intermediate principal stresses that can make the major principal stress values to be quite close to the uniaxial tensile strength value [31,32].…”

Section: Discussionmentioning

confidence: 99%

Determination of Direct Tensile Strength Values of Rock Materials by a New Test Method of Drilled Disc Tension

Komurlu

Demir

2019

Period. Polytech. Civil Eng.

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Use of drilled disc specimens was investigated with both numerical and experimental studies to determine direct tensile strengths of rock materials. A new loading apparatus with rods to insert into the drill holes of discs has been designed and manufactured to supply tension by using the compression test presses. In addition to the use of popular compressive presses for direct tension, elimination of the gluing in the standard direct tensile strength test method is a significant advantage to make possible both hard and soft rocks to be tested. The Brazilian test discs with the diameter of NX size and length to diameter ratio of 0.5 were used in tests. Different loading apparatus designs were analyzed and ideal angle of contact between rock and the loading rods was assessed to be 50° within various choices investigated in this study. The drilled discs were determined to fail due to the crack initiation under the condition of uniaxial tensile stress distribution at sidewalls of the hole. In addition to the drilled disc tension test, standard direct tensile strength tests were also carried out to take as reference and compare the results obtained from different methods. According to the results of both numerical and experimental studies, an equation was suggested to determine uniaxial tensile strengths of drilled disc specimens with 20 mm hole diameter and the contact angle of 50°.

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“…Additionally, two horizontal stresses which are parallel and perpendicular to drill-hole direction are intermediate and minor principal stresses at sidewalls, the location of the maximum tension. It is advantageous to have low level minor and intermediate principal stresses that can make the major principal stress values to be quite close to the uniaxial tensile strength value [21][22][23].…”

Section: Discussionmentioning

confidence: 99%

Drilled Core Specimen Testing Method for Determination of Tensile Strength Values of Rock Materials

Komurlu¹,

Demir

2018

Period. Polytech. Civil Eng.

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In this study, a new direct tensile strength determination method of drilled core specimen testing was investigated with numerical and experimental studies. Effect of different drill diameters of holes of the rock specimens was analysed to assess the ideal drill-hole design. The aim of drilling process is decreasing the failure load and stress concentration at the adhesive part to prevent invalid failures. Drilled specimens were determined to fail due to the start of cracking under the condition of uniaxial tensile stress distribution at sidewalls of holes. It was found that drill bits with the diameter of 11 mm is usable for a practical specimen drilling process to make a significant decrease in the failure load of the core specimens with the NX size (@54 mm) diameter. According to the results obtained from numerical and experimental analyses, an equation was suggested to determine uniaxial tensile strength values of drilled core specimens with the hole diameter of 11 mm.

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Strength criterion for rocks under compressive-tensile stresses and its application

Cited by 37 publications

References 28 publications

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Determination of Direct Tensile Strength Values of Rock Materials by a New Test Method of Drilled Disc Tension

Drilled Core Specimen Testing Method for Determination of Tensile Strength Values of Rock Materials

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