Assessment of rock geomechanical quality by quantitative rock fabric coefficients: Limitations and possible source of misinterpretations

• Published in: Engineering geology 2006-11, Vol.87 (3), p.149-162
• Main Author: PRIKRYL, Richard
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; Correlation; Exact sciences and technology; Geotechnics; Grain size; Mechanical properties; Petrographic image analysis; Quantitative analysis; Rock fabric; Soil mechanics. Rocks mechanics
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2006.05.011

Rock microfabrics were quantified by image measurement system (petrographic image analysis) of thin sections. Along with common measured parameters (grain area and size, length of major and minor axes and their orientation), some quantitative parameters (aspect ratio, grain boundary smoothness) and fabric coefficients (micropetrographic quality index ( K), “texture” coefficient (TC), indexes of interlocking ( t) and grain size homogeneity ( g)) were determined. The reliability of these parameters for the evaluation of geomechanical properties was tested on the set of granitic rocks showing pronounced variability in rock mechanical properties. None of the tested rock fabric coefficients or parameters proved a close correlation to rock mechanical properties except grain size. Based on experimental findings, the grain size is, along with porosity, the controlling factor of rock mechanical properties of genetically and mineralogically similar rocks. Obliteration of the real effects of rock fabric parameters on the mechanical properties of rocks by application of complex fabric coefficients disables their practical use in petrography applied to geomechanics.