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.
This paper describes the use of quantitative mineralogy and specific surface area in interpreting the index properties of clayey soils from nine sites in Eastern Canada. Samples representative of the Tyrrell, Laflamme, Champlain, and Goldthwait marine seas and Lac Barlow–Ojibway have been studied.Quantitative X-ray diffraction analyses may be satisfactorily obtained using potassium metaperiodate (Foscal-Mella 1976) as an internal standard in these soils. Determination of contained amorphous matter requires extraction procedures less brutal than those employed in the Ségalen method.Correlations between Atterberg limits and specific surface area are believed to be more useful than those between specific surface area and the grain size or clay fraction. Increases in plasticity and specific surface area are related to increases in the amount of contained phyllosilicates and amorphous matter.The mineralogical composition of the soils studied is dominated, even in the clay fraction, by felsic minerals (plagioclase, quartz, microcline, and hornblende). Samples close to the Canadian Shield contain relatively more felsic minerals than those away from it. Key words: mineralogy, index properties, sensitive clays, physicochemistry.
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