ArticleName 
Analysis of fractal characteristics of jointing in rocks
as their strength criterion 
ArticleAuthorData 
Author 1: Name & Surname: Latyshev O. G. Company: Ural State Mining University (Ekaterinburg, Russia) Work Position: Professor Scientific Degree: Doctor of Engineering Sciences
Author 2: Name & Surname: Kornilkov M. V. Company: Ural State Mining University (Ekaterinburg, Russia) Work Position: Head of department Scientific Degree: Professor, Doctor of Engineering Contacts: shs.dep@ursmu.ru

Abstract 
The modern theories and hypotheses on strength and failure of solids are based on fracture dynamics. In this context, this article reports the integrated research findings on jointing in rocks as applied to their strength and failure. The geometry of joints estimated by their fractal dimension is determined using the luminescent detection method, and the equation of size distribution of joints is obtained. The implemented series of experimental research involved loading, concurrent measurement of deformation and recording of sporadic defects in specimens of effusive rocks of the Urals. The procedure and its computer implementation are developed for the research of fractal characteristics of jointing in rocks. It is found that the loglinear equation is the most adequate equation for hard rocks. It allows estimating rock strength from the viewpoint of the theory of brittle failure (Griffith crack theory). Taking into account fractal dimensions enables more accurate estimate of energy balance of crack growth and, thus, an adequate estimate of physics of rock failure processes. The most important characteristic of jointing in rocks is the quantitative estimate of dynamics of crack coalescence and clustering of fracture sources. The analysis of initiation, growth and coalescence of clusters shows that the curve of the fractal cluster dimension versus effective stresses has two clearly seen linear regions. The plots of fractal cluster dimensions versus loading of rock specimens define boundaries of two failure stages—slow accumulation of damage and dynamic clustering—resulting in brittle failure of rocks. In accordance with the kinetic concept of strength, survival equation parameters, that are activation energy and structural coefficient, are compared at each stage. The research procedures and findings enable assessment of the dynamic mechanisms of jointing in rocks and prediction of their strength based on the kinetic concept. 
keywords 
Rocks, jointing, fractal characteristics, Griffith theory, crack geometry, luminescence detection, cluster dimension, brittle failure, kinetic concept, strength prediction 
References 
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