Challenges related to standardized detection of crack initiation thresholds for lower-bound or ultra-long-term strength prediction of rock

E. Ghazvinian, M. Diederichs, J. Archibald

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Mining and Rock Mechanics

ABSTRACT: Brittle spalling is a fracture mechanism that occurs in the walls of excavations in rocks with a low ratio of tensile to compressive strength. This mechanism does not always occur in laboratory strength tests. However, within a standard UCS test, it is possible to detect the onset of extensile damage accumulation and interaction. There are a number of methods to detect these thresholds involving either rigorous strain measurements or micro-acoustic monitoring. The Spall Prediction Commission of the International Society for Rock Mechanics is testing a number of processing algorithms for strain and acoustic data to develop a suggested methodology for crack initiation stress (CI) and crack interaction stress (CD) measurement. This paper examines both methods. A number of challenges with repeatable and reliable measurements of CI and CD are addressed and alternative approaches are proposed.

RÉSUMÉ: Écaillage fragile est un mécanisme de rupture qui se produit dans les murs de fouilles dans les roches avec un faible ratio de traction à la résistance à la compression. Ce mécanisme ne se produit pas toujours dans les tests de résistance en laboratoire. Toutefois, dans un test standard UCS, il est possible de détecter l'apparition de l'accumulation de dommages extensibles et l'interaction. Il ya un certain nombre de méthodes pour détecter ce seuils impliquant soit la souche rigoureuse mesure ou la surveillance micro-acoustique. La prévision Spall Commission de la Société internationale de mécanique des roches à l'essai un certain nombre d'algorithmes de traitement pour la souche et les données acoustiques de développer une méthodologie proposée pour le stress initiation de la fissure (CI) et le crack interaction stress (CD) de mesure. Cet article examine les deux méthodes. Une certain nombre de défis à la mesure reproductible et fiable de CI et de CD sont abordés et des approches alternatives sont proposées.

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Cite this article:
E. Ghazvinian; M. Diederichs; J. Archibald (2011) Challenges related to standardized detection of crack initiation thresholds for lower-bound or ultra-long-term strength prediction of rock in GEO2011. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GEO11Paper521,author = E. Ghazvinian; M. Diederichs; J. Archibald ,title = Challenges related to standardized detection of crack initiation thresholds for lower-bound or ultra-long-term strength prediction of rock,year = 2011}