College of Mining, National University of Science and Technology – MISIS, Moscow, Russia:

V. A. Vinnikov, Head of a Chair, Doctor of Physico-Mathematical Sciences, vinnikovva@misis.ru
E. B. Cherepetskaya, Professor, Doctor of Engineering Sciences

Institute of Integrated Mineral Development – IPKON, Russian Academy of Sciences, Moscow, Russia:

V. N. Zakharov, Director, Corresponding Member of the Russian Academy of Sciences, Professor, Doctor of Engineering Sciences
O. N. Malinnikova, Head of Laboratory, Doctor of Engineering Sciences

The authors analyze the current nondestructive approaches to obtaining information on internal structure and properties of rock specimens. The operating principle of the advanced equipment of contact broadband ultrasonic structural spectroscopy is considered. The change in the structure of geomaterial specimens under effect of various physical fields was studied using the unique GEOSCAN-02MU plant designed at the College of Mining of the National University of Science and Technology – MISIS. The article presents the data on measured elastic waves in trigonal crystal system of quartz and in samples of bituminous coal from Kusnetsk Basin with the carbon content of 62–68% and average humidity of 1.5%. Based on the measurement results, Young’s modulus and Poisson’s ratio were calculated. The scatter in the physico-mechanical characteristics of coal was explained based on 2D visualization of inner structure of samples using the measured acoustic tracks. The research findings enabled assessment of depth, length and width of joints in the test coal samples, which offered the explanation of the scatter in the values of Young’s modulus (2.6–3.9 GPa) and Poisson’s ratio (0.25–04). During the further testing, quartz crystals were subjected to cyclical uniaxial loading; at each loading stage, using system SDS 1008 equipped with the broadband piezoelectric transducer GT 301 with the passband from 100 kHz to 5 MHz, acoustic emission of growing defects was recorded, and 2D visualization of inner structure of the defects was performed based on the measured acoustic tracts, which allowed sizing and localization of the defects. The research has shown that load making 20% of destructive load initiates fine defects and induces insufficient growth of the existing discontinuities. Under load equaling 30% of destructive load, intense jointing is observed even in almost uniform samples with a slight anisotropy, which tells on inapplicability of the linear elasticity theory to description of the destruction. The research illustrates capability of contact laser–ultrasonic structural spectroscopy in the determination of internal structure of samples in case when the other methods are inapplicable (for example, in strongly absorbing media when densities of a discontinuity and a basic material have close values).

The study has been supported by the Russian Science Foundation, Grant No. 16-17-10181.

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