On the Issue of Typical Grain Size Assessment by the Methods of Broadband Laser Opto-Acoustics

Abstract

It is shown that one of the express-methods for studying the internal structure and phase composition of geomaterial samples is broadband acoustic spectroscopy with laser sources of ultrasound. Theoretical assessment of time profiles and spectrums of opto-acoustic signals are presented. Numerical modelling of the spectrums and time profiles of ultrasound signals generated in opto-acoustic generators made of a different material is performed. The influence of diffraction and damping in rocks on the above characteristics is studied. The amplitude spectrum and time profiles of ultrasonic pulses transmitted through samples of marble of various thicknesses in which the most part of the characteristic grain sizes lies in the range of 500 μm - 1 mm are constructed. It has been established that, according to the amplitude spectrum of the original signal and the transmitted through the sample signal, it is possible to restore the characteristic dimensions of the grains.