Justification of shear wave generation using laser ultrasound in the mode of echo pulses in geomaterial

One of the main parameters of geomechanical models is the static elastic modulus. However, sometimes there is no sufficient amount of geological material and the dynamic elastic moduli are determined from elastic wave velocities in rock specimens; then the static moduli are determined using available correlation dependences. Existing ultrasonic techniques that involve generating and recording ultrasound with piezoelectric components are unable to measure velocities with high accuracy. To address this problem, it is proposed to use laser ultrasonic diagnostics. Based on the theory of quantitative seismology, the paper theoretically substantiates the generation of shear waves at the interface between two media as a result of pulse-echo laser ultrasonic propagation. On this basis, we analytically simulated the temporal shape of ultrasonic pulses travelling in a limestone specimen. Also, experimental studies were carried out using a laser ultrasonic flaw detector UDL-2M to obtain the temporal shape of ultrasonic pulse in the limestone specimen. The analytically determined shape of the ultrasonic pulse was compared with the experimental one; the velocities were determined experimentally and analytically. Consequently, a technique is developed for determining elastic wave velocities in rock specimens by waveform matching.

Shibaev I. A., Bychkov A. S. Justification for generating a shear elastic wave using laser ultrasound in the mode of echo pulses in a geomaterial. MIAB. Mining Inf. Anal. Bull. 2021;(4-1):108—117. [In Russ]. DOI: 10.25018/0236_1493_2021_41_0_108.

The reported study was funded by RFBR, project number 19-35-90063.

Shibaev I. A.¹, PhD-student, mrdfyz@mail.ru;
BychkovA. S.¹, Cand. Sci. (Phys. Mathem.), Research Assistant, abychkov@optoacoustic.ru;
¹ National Research Technological University “MISiS” Mining Institute, Moscow, Russia.

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