Fracture initiation and propagation in intact rock – A review

Hoek, E.; Martin, C. Derek

doi:10.1016/j.jrmge.2014.06.001

Cited by 518 publications

(180 citation statements)

References 24 publications

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“…Firstly, the true cohesive strength (essentially synonymous with tensile strength) is exceeded as the solid ruptures, and secondly, there must be adequate energy available to allow the continued development of two distinct joint surfaces and to allow the fracture to extend and propagate. This brittle fracturing process comprising fracture initiation and propagation is predominately controlled by the tensile strength of intact rock including its component grains (Hoek and Martin 2014). Joint surface morphology is normally decorated by textures such as hackles and rib marks that reflect the joint initiation, orientation and propagation processes (Pollard and Aydin 1988;Ameen 1995).…”

Section: Discussionmentioning

confidence: 99%

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

et al. 2017

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True persistence of rock discontinuities (areas with insignificant tensile strength) is an important factor controlling the engineering behaviour of fractured rock masses, but is extremely difficult to quantify using current geological survey methodologies, even where there is good rock exposure. Trace length as measured in the field or using remote measurement devices is actually only broadly indicative of persistence for rock engineering practice and numerical modelling. Visible traces of discontinuities are treated as if they were open fractures within rock mass classifications, despite many such traces being non-persistent and actually retaining considerable strength. The common assumption of 100% persistence, based on trace length, is generally extremely conservative in terms of strength and stiffness, but not always so and may lead to a wrong prediction of failure mechanism or of excavatability. Assuming full persistence would give hopelessly incorrect predictions of hydraulic conductivity. A new technique termed forensic excavation of rock masses is introduced, as a procedure for directly investigating discontinuity persistence. This technique involves non-explosive excavation of rock masses by injecting an expansive chemical splitter along incipient discontinuities. On expansion, the splitter causes the incipient traces to open as true joints. Experiments are described in which near-planar rock discontinuities, through siltstone and sandstone, were opened up by injecting the splitter into holes drilled along the lines of visible traces of the discontinuities in the laboratory and in the field. Once exposed the surfaces were examined to investigate the pre-existing persistence characteristics of the incipient discontinuities. One conclusion from this study is that visible trace length of a discontinuity can be a poor indicator of true persistence (defined for a fracture area with negligible tensile strength). An observation from this series of experiments was that freshly failed surfaces through pre-existing rock bridges were relatively rough compared to sections of pre-existing weaker areas of geologically developed (though still incipient) discontinuities. Fractographic features such as hackle and rib marks were typical of the freshly broken rock bridges, whereas opened-up areas of incipient discontinuity were smoother. Schmidt hammer rebound values were generally higher for the rock bridge areas, probably reflecting their lower degree of chemical and physical weathering.

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Section: Discussionmentioning

confidence: 99%

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

et al. 2017

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“…On this topic, some preliminary results have been achieved under isotropic simplification for both the damage and inelastic strain (Zhu 2016). Moreover, according to experimental results, the ratio of compressive strength to tensile strength may vary within a large range (Hoek and Martin 2014). For some rocks, prediction by Eq.…”

Section: Discussionmentioning

confidence: 99%

“…Later, the Griffith failure theory was extended to various aspects; for example, the extension to pennyshaped cracks (Keer 1966;Margolin 1984), the contributions for brittle fracture under compressive or shear stresses (McClintock and Walsh 1962;Hoek and Bieniawski 1965;Wang and Shrive 1993), the works for Griffith failure in three dimensions (Sack 1946;Kassir and Sih 1967;Hatzitrifon and Gdoutos 1988), the work by Brace (1960) to take into account pore pressure effect, just mention the representative ones. Comparisons of the Griffith theory with other well-known failure criteria have also been performed (Clausing 1959;Brace and Bombolakis 1963;Hoek and Martin 2014). It is worth noticing that in view of the importance of the Griffith theory, Patersson and Wong (2010) included in their book a whole chapter on this topic.…”

Section: Introductionmentioning

confidence: 99%

A New Rock Strength Criterion from Microcracking Mechanisms Which Provides Theoretical Evidence of Hybrid Failure

Zhu

2016

Rock Mech Rock Eng

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A proper criterion describing when material fails is essential for deep understanding and constitutive modeling of rock damage and failure by microcracking. Physically, such a criterion should be the global effect of local mechanical response and microstructure evolution inside the material. This paper aims at deriving a new mechanisms-based failure criterion for brittle rocks, based on micromechanical unilateral damage-friction coupling analyses rather than on the basic results from the classical linear elastic fracture mechanics. The failure functions respectively describing three failure modes (purely tensile mode, tensile-shear mode as well as compressive-shear mode) are achieved in a unified upscaling framework and illustrated in the Mohr plane and also in the plane of principal stresses. The strength envelope is proved to be continuous and smooth with a compressive to tensile strength ratio dependent on material properties. Comparisons with experimental data are finally carried out. By this work, we also provide a theoretical evidence on the hybrid failure and the smooth transition from tensile failure to compressive-shear failure.

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“…Hoek and Martin (2014) recently compared our theoretical criterion with Mohr-Coulomb and Griffith's criterion in Fig. 3 of their paper.…”

Section: Introductionmentioning

confidence: 99%

A theoretical derivation of the Hoek–Brown failure criterion for rock materials

Zuo

Liu

2015

Journal of Rock Mechanics and Geotechnical Engineering

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This study uses a three-dimensional crack model to theoretically derive the Hoek-Brown rock failure criterion based on the linear elastic fracture theory.Specifically, we argue that a failure characteristic factor needs to exceed a critical value when macro-failure occurs. This factor is a product of the micro-failure orientation angle (characterizing the density and orientation of damaged micro-cracks) and the changing rate of the angle with respect to the major principal stress (characterizing the microscopic stability of damaged cracks). We further demonstrate that the factor mathematically leads to the empirical Hoek-Brown rock failure criterion. Thus, the proposed factor is able to successfully relate the evolution of microscopic damaged crack characteristics to macro-failure. Based on this theoretical development, we also propose a quantitative relationship between the brittle-ductile transition point and confining pressure, which is consistent with experimental observations.

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Fracture initiation and propagation in intact rock – A review

Cited by 518 publications

References 24 publications

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

Forensic Excavation of Rock Masses: A Technique to Investigate Discontinuity Persistence

A New Rock Strength Criterion from Microcracking Mechanisms Which Provides Theoretical Evidence of Hybrid Failure

A theoretical derivation of the Hoek–Brown failure criterion for rock materials

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