Experimental investigation of fracture process zone in rocks damaged under cyclic loadings

Ghamgosar, M., Erarslan, N. and Williams, D. J. (2016) Experimental investigation of fracture process zone in rocks damaged under cyclic loadings. Experimental Mechanics, 57 1: 1-17. doi:10.1007/s11340-016-0216-4

Author Ghamgosar, M.
Erarslan, N.
Williams, D. J.
Title Experimental investigation of fracture process zone in rocks damaged under cyclic loadings
Journal name Experimental Mechanics   Check publisher's open access policy
ISSN 1741-2765
Publication date 2016-10-03
Sub-type Article (original research)
DOI 10.1007/s11340-016-0216-4
Open Access Status Not yet assessed
Volume 57
Issue 1
Start page 1
End page 17
Total pages 17
Place of publication New York, NY, United States
Publisher Springer New York LLC
Language eng
Subject 2202 Aerospace Engineering
2211 Mechanics of Materials
2210 Mechanical Engineering
Abstract Compared with other materials, most rocks generally fail in a brittle fashion rather than exhibiting yielding or purely plastic deformation. However, the initiation and coalescence of micro-cracks in the nonlinear region, known as the ‘fracture process zone’ (FPZ), are the primary reason for fracture propagation in rocks. Different elasticity-related models proposed for determining the features of the FPZ have not achieved an adequate understanding of its various fracture patterns. Based on previous experiments and numerical models, micro-crack density has been shown to be a function of loading history and to vary depending on whether the loading is monotonic or cyclic. The aim of the study reported here was to examine the different patterns of the FPZ under various types of cyclic loading and to quantitatively define damage and fracture patterns through the grains or rock matrix. Considerable laboratory testing was conducted, and fractured samples were investigated by computerised tomography scanning, supported by thin-section analysis. In the study, two different types of cyclic loading were tested: stepped and continuous. A diametral compressive loading was applied at predetermined amplitude and frequency with the continuous cyclic loading. The applied cyclic diametral compressive load was returned to the original level after each step, and at the next step, the amplitude started from zero, with stepped cyclic loading (SCL). An average 30 % strength reduction was found due to the SCL and emergence of high micro-fracture density in the FPZ. We presume that hard rock breakage techniques will be improved, especially for rock-cutting technologies, such as drag bits and oscillating disc cutting, by understanding the effects of cyclic loading on rock strength.
Keyword Computerised tomography (CT) scans
Cyclic loading
Dynamic rock cutting
Fracture process zone (FPZ)
Rock fracture mechanics
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
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