Development of an Index to Quantify Rock Texture for Qualitative Assessment of Intact Rock Properties

A dimensionless quantitative measure of rock texture, describing grain shape, orientation, degree of grain interlocking, and relative proportions of grains and matrix (packing density) has been developed. Data required for the model are obtained by image analysis of thin sections and concern percentage areas of grains and matrix, length, breadth, perimeter, orientation, and area of each grain in the viewing window. The results of intact mechanical property tests in eleven sedimentary and crystalline rocks are reported and correlated with the developed texture coefficient. The texture coefficient returns highly statistically significant correlations with mechanical property data and is superior to the Schmidt hammer rebound test number in this regard. Observational and correlated data are supportive of the suggestion that the texture coefficient is a qualitative measure of the resistance of the microstructure of a rock to crack propagation, whether it be integranular or intragranular. The texture coefficient can be used as a predictive tool for the assessment of mechanical rock performance. On a fundamental level it provides an insight into texture-crack propagation mechanical performance relationships.