Experimental study of elastic properties of coals of various degrees of tectonic disturbance by laser-ultrasonic spectroscopy

The paper discusses the examination of coal specimens obtained from the Boldarevsky Bed (S. М. Kirov coal mine, Kuznetsk Basin). Elastic wave velocities in the coal specimens were measured by means of laser ultrasonic testing in pulse-echo and through-transmission modes. Generated acoustic pulses travelled in two directions, parallel and perpendicular to visual layering. We used the well-known empirical Markote-Rios and Greenberg-Castagna equations to verify the relationship of the measured velocities Vl(Vt). The local values of the dynamic modulus of elasticity were determined from the experimental elastic wave velocities. It is found that the most informative parameter for assessing the anisotropy of black coals is the P-wave velocity. It is found that shear wave velocities and dynamic modulus of elasticity do not exhibit significant changes depending on direction, which is due to the high heterogeneity of coal and elastic waves attenuation. Images of the internal structure of the specimens were produced in three planes, based on which the geometric characteristics and orientation of heterogeneities and bedding were determined. Coal specimens from the overlying coal seam, which is less affected by stress and temperatures, were similarly examined. It is revealed that its structure is more anisotropic with orthotropic elastic characteristics. It is concluded that the elastic characteristics of coals become more isotropic due to an increasing level of disturbances caused by various tectonic processes.

Ivanov P. N., Bezrukov V. I. Experimental study of elastic properties of coals of various degrees of tectonic disturbance by laser-ultrasonic spectroscopy. MIAB. Mining Inf. Anal. Bull. 2021;(4-1):26—40. [In Russ]. DOI: 10.25018/0236_1493_2021_41_0_26.

Ivanov P. N.¹, PhD-student, pavelnivanov@mail.ru;
Bezrukov V. I.¹, student;
¹ National Research Technological University “MISiS” Mining Institute, Moscow, Russia.

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