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TitleFormalized approaches to defining damage thresholds in brittle rock: Granite and limestone
AuthorGhazvinian, E; Perras, M; Diederichs, M; Labrie, D
Source46th US Rock Mechanics / Geomechanics Symposium 2012; vol. 2, 2012 p. 966-974
Released2012 01 01
Brittle spalling is the failure mechanism that is commonly observed in the walls of underground excavations in rocks with high ratio of compressive to tensile strength (brittle rock). Extensile crack damage that is controlling spalling in brittle rock is rarely capable of leading the failure mechanism of the rock in laboratory strength tests due to geometric constraints within the test. The onset of crack damage thresholds in brittle rock can be identified by acoustic emission monitoring or rigorous strain measurements during a laboratory compressive test. Crack initiation (CI) and crack propagation (CD) stresses correspond to long-term and yielding (short-term) in situ strength of the rock. The repeatability and subjectivity of interpretation of the existing algorithms for calculation of crack damage thresholds is evaluated through inter-laboratory comparisons for Smaland granite and since initially these algorithms were all developed for granitic rocks, their accuracy and robustness is determined for Lindsay Cobourg limestone as a sedimentary rock. This paper presents the latest guidelines that are to be included in the ISRM "Suggested Method" for defining damage thresholds in brittle rocks.

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