Numerical investigation of the direct tensile behaviour of laminated and transversely isotropic rocks containing incipient bedding planes with different strengths

Shang, Junlong; Kang, Di; Gui, Yilin; Handley, Kirk; Zhao, Zhiye

doi:10.1016/j.compgeo.2017.11.007

Cited by 63 publications

(30 citation statements)

References 28 publications

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“…For the parallel-bonded particle model (in PFC 3D), a force and a moment are developed within bond materials, and the force and moment can be related to maximum normal and shear stresses acting on contacting particles (PFC 3D manual, 2008). The cohesive bond will break and vanish once either of the maximum stresses exceeds its corresponding bond strength, and the fracture propagation can be achieved by the coalescence of multiple bond breakages (Lisjak & Grasselli, 2014;Shang, Duan, et al, 2018). The shear force between particles after the bond breakage arises from the coefficient of friction at their contacts, and its magnitude also depends on the normal force between the particles.…”

Section: Particulate Demmentioning

confidence: 99%

“…However, clear discrepancies between numerical and empirical results were observed for the tests under somewhat higher confinement (30 MPa). This phenomenon is mainly due to the intrinsic limitation of the parallel bond contact model, which cannot provide enough interlocking such as occurring with natural mineral grains, especially under high confinement (Shang, Duan, et al, 2018;Zhang et al, 2019). Despite the limitation of this approach, it is still attractive because it can reproduce many significant physical features and mechanical mechanisms that occur in rocks, such as fracturing process, dilation, time-dependent behavior, and strength increase with confinement (Lee & Jeon, 2011;LongJohn et al, 2018;Potyondy & Cundall, 2004;Potyondy, 2007;Virgo et al, 2013;Zhang et al, 2019).…”

Section: 1029/2019jb019052mentioning

confidence: 99%

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Rupture Of Veined Granite In Polyaxial Compression: Insights From Three‐Dimensional Discrete Element Method Modeling

Shang

2020

JGR Solid Earth

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Granite formations have been frequently involved in subsurface energy‐related activities such as radioactive waste disposal, oil, and gas storage. This is principally because of their mechanical stability, low permeability, and high corrosion resistance. These favorable properties, however, can be compromised by the addition of mineral veins, which tend to occur ubiquitously in upper crustal rock formations. Evaluation of the impact of veins on the integrity and rupture characteristics of granite, especially under true triaxial stresses, is therefore important yet currently underemphasized. This study examines the rupture of veined granite in polyaxial compression via a discrete element method model. In the model with soft veins, the rupture is localized along the fabricated inclined veins (45° relative to the horizontal with strike running in the σ2 direction) under low confining stresses (σ2 < 67 MPa); in contrast, a combined rupture of veins and granite matrix is observed when σ2 is increased to 141.6 MPa. Shear sliding along the inclined veins is revealed by examining the displacement field. Shear‐induced volumetric dilation is suspected in the soft‐veined models in relatively low confining stresses (σ2 < 67 MPa) with sliding and dilation behavior apparently suppressed at σ2 = 141.6 MPa. Hard veins impede local rupture, resulting in conjugate shear bands. The well‐recognized σ2 effect is observed for the hard‐veined models, while no pronounced σ2 effect is noticed for the soft‐veined models. This study also reveals that vein thickness has a negligible impact on rupture characteristics, which is however profoundly affected by vein orientation.

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Section: Particulate Demmentioning

confidence: 99%

Section: 1029/2019jb019052mentioning

confidence: 99%

Rupture Of Veined Granite In Polyaxial Compression: Insights From Three‐Dimensional Discrete Element Method Modeling

Shang

2020

JGR Solid Earth

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“…The area of rock bridge can only be viewed after collapse (see for example in Fig. 6) when strength of revealed bridges can be back analysed (Paronuzzi and Serafini, 2009 Shang et al 2017b, in which the incipiency of bedding planes (relative tensile strength to that of parent rock) was considered.…”

Section: Mechanical Properties Of Individual Discontinuitiesmentioning

confidence: 99%

Geological discontinuity persistence: Implications and quantification

Shang

West

Hencher

et al. 2018

Engineering Geology

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106

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Persistence of geological discontinuities is of great importance for many rock-related applications in earth sciences, both in terms of mechanical and hydraulic properties of individual discontinuities and fractured rock masses. Although the importance of persistence has been identified by academics and practitioners over the past decades, quantification of areal persistence remains extremely difficult; in practice, trace length from finite outcrop is still often used as an approximation for persistence. This paper reviews the mechanical behaviour of individual discontinuities that are not fully persistent, and the implications of persistence on the strength and stability of rock masses. Current techniques to quantify discontinuity persistence are then examined. This review will facilitate application of the most applicable methods to measure or predict persistence in rock engineering projects, and recommended approaches for the quantification of discontinuity persistence. Furthermore, it demonstrates that further research should focus on the development of persistence quantification standards to promote our understanding of rock mass behaviours including strength, stability and permeability.

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“…Classic rock mass classification schemes such as Q system, RMR and RQD are defined on the basis of this engineering assumption which means that they all fail to resolve the issue of incipiency of discontinuities as well as varying degrees of tensile strength [34]. It would be beneficial if incipient discontinuities can be differentiated in terms of relative tensile strength in the rock mass classifications [32].…”

Section: Implications For Rock Mass Classificationmentioning

confidence: 99%

Tensile strength of large-scale incipient rock joints: a laboratory investigation

et al. 2017

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In this paper, a testing methodology was developed in the laboratory to measure the tensile strength of large-scale incipient rock joints. In the test, an expansive grout was used to develop the tensile force. Each test comprises two phases: Phase i test and Phase ii test. The Phase i test identified sample failure time, while the Phase ii test measured the corresponding tensile force arising from the expansive grout. Ostensibly homogeneous rock samples without incipient joints were firstly tested to establish the methodology. Tensile strength of block samples containing incipient rock joints was then measured using the established testing scheme. The test results have been compared with those obtained from conventional Brazilian and uniaxial tension tests as suggested by ISRM. The proposed approach is capable of giving a measure of tensile strength of large-scale incipient rock joints, although somewhat smaller strength than that from the standard approaches was occasionally measured in the preliminary tests on ostensibly homogeneous samples. Effects of stress concentration, sample scale, loading rate and expansive tensile force on the testing results were discussed. Furthermore, this simple and practical testing scheme is proposed for the measurement of the in situ tensile strength of rock and incipient discontinuities in the field, which if successful will provide a more scientific guidance on the rock mass classification and engineering design.

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Numerical investigation of the direct tensile behaviour of laminated and transversely isotropic rocks containing incipient bedding planes with different strengths

Abstract: Numerical investigation of the direct tensile behaviour of laminated and transversely isotropic rocks containing incipient bedding planes with different strengths.

Cited by 63 publications

References 28 publications

Rupture Of Veined Granite In Polyaxial Compression: Insights From Three‐Dimensional Discrete Element Method Modeling

Rupture Of Veined Granite In Polyaxial Compression: Insights From Three‐Dimensional Discrete Element Method Modeling

Geological discontinuity persistence: Implications and quantification

Tensile strength of large-scale incipient rock joints: a laboratory investigation

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