Evidence for a Long-Term Strength Threshold in Crystalline Rock

Damjanac, Branko; Fairhurst, C.

doi:10.1007/s00603-010-0090-9

Cited by 169 publications

(85 citation statements)

References 31 publications

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“…Damjanac and Fairhurst (2010) suggested that crack initiation may also be used as a lower bound estimate for the long-term strength threshold of crystalline rocks. Other researchers suggest that crack initiation related to the Kaiser effect (will be discussed later) can be used to establish the in-situ state of stress (Seto et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

2015

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Determination of the cracking levels during the crack propagation is one of the key challenges in the field of fracture mechanics of rocks. Acoustic emission (AE) is a technique that has been used to detect cracks as they occur across the specimen. Parametric analysis of AE signals and correlating these parameters (e.g. hits and energy) to stress-strain plots of rocks let us detect cracking levels, properly. The number of AE hits is related to the number of cracks, and the AE energy is related to magnitude of the cracking event. For a full understanding of the fracture process in brittle rocks, prismatic specimens of granite containing pre-existing flaws have been tested in uniaxial compression tests, and their cracking process was monitored with both AE and high-speed video imaging. In this paper the characteristics of the AE parameters and the evolution of cracking sequences are analyzed for every cracking level. Based on micro-and macro-crack damage, a classification of cracking levels is introduced. This classification contains eight stages 1) crack closure, 2) linear elastic deformation, 3) micro-crack initiation (white patch initiation), 4) micro-crack growth (stable crack growth), 5) micro-crack coalescence (macro-crack initiation), 6) macro-crack growth (unstable crack growth), 7) macro-crack coalescence and 8) failure.

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Section: Introductionmentioning

confidence: 99%

Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

2015

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“…The driving stress-ratio has been defined as the axially applied stress level, at a particular stage in the test, normalized to the average UCS (so-called instantaneous response measured according to ISRM, 1979 standards) and has been used by many other researchers (Schmidtke and Lajtai, 1985;Lajtai et al 1991;Lau and Chandler, 2004;Potyondy, 2007;Damjanac and Fairhurst, 2010) to present long-term (time-dependent) testing results acquired from creep tests.…”

Section: Defining Strain Thresholdsmentioning

confidence: 99%

“…In a second phase of testing the time-dependent behaviour of the Cobourg limestone, which is the potential host rock for a proposed Low and Intermediate Nuclear Waste Repository in Canada, was examined. According to Damjanac and Fairhurst (2010), a better understanding of the longterm rock deformability in the design and construction of nuclear waste repositories is a key behavioural aspect for predicting the ability of the rock to isolate the waste from the biosphere.…”

Section: Introduction (Was Simplified Some Parts Were Removed Accordmentioning

confidence: 99%

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

Paraskevopoulou

Perras

Diederichs

et al. 2017

Engineering Geology

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“…This method considers the static stress level, where the rock sample's creep rate is about 0 as the rock's long-term strength [24]. As shown in Figure 7, according to the analysis of fitting to rock's creep curve, the creep rates of both samples tend to be 0 at the first two static stress levels.…”

Section: Confirmation Of Long-termmentioning

confidence: 99%

Experimental Study on Sedimentary Rock’s Dynamic Characteristics under Creep State Using a New Type of Testing Equipment

Huang

Chen

et al. 2017

Advances in Materials Science and Engineering

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Under high stress, rock in the creep state is vulnerable to external impact load, causing the irreversible perturbation deformation of rock or even sudden failure. To explore the dynamic characteristics of sedimentary rock in the creep state, a siltstone specimen was experimentally studied using a new type of experimental system for rock creep perturbation. Compared to the currently available equipment for studying rock dynamics, this new type of experimental system provides a long-term and stable high static stress to maintain the creep state of rock specimen. This is independent of power supply because it provides static stress by gravity load. Moreover, the equipment provides a dynamic impact load through the free fall of impact weights. This study shows that the perturbation deformation of sedimentary rock increased in two stages: decay phase and sustained development phase. When the static stress reached up to ∼85% of the rock's ultimate strength and the axial strain reached up to 80% of the ultimate failure strain, the rock became sensitive to impact load. This static stress level is basically the same as its long-term strength. With increasing impact strength, the increment curve of the rock creep perturbation deformation was transformed from the decay phase to the sustained development phase in advance, making the rock sensitive to external perturbation at a low static loading stress level.

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Evidence for a Long-Term Strength Threshold in Crystalline Rock

Cited by 169 publications

References 31 publications

Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

Detection of Cracking Levels in Brittle Rocks by Parametric Analysis of the Acoustic Emission Signals

The three stages of stress relaxation - Observations for the time-dependent behaviour of brittle rocks based on laboratory testing

Experimental Study on Sedimentary Rock’s Dynamic Characteristics under Creep State Using a New Type of Testing Equipment

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