The possibilities of laser ultrasonic echoscopy for detection and diagnostics of rock structural imperfections are considered. It is shown, that calculating with the help of fast Fourier transformation spectra of the signals, arrived in a sample and multiple scattered, and carrying out a corresponding frequency filtration, it is possible to obtaine environment reflaction factor and on its basis to construct the sample structure image.The examples of forming images of structural changes under different influences on the rock samples are presented. The ferruginous quartzite samples were influenced by pulse electromagnetic field, the Karelian marble samples – thermal field.
The possibility of creating laser-ultrasonic sources of short power pulses of elastic longitudinal waves on the basis of nonlinear thermal processes in the generator medium is examined theoretically and experimentally. A three-dimensional model of thermal nonlinearity is considered, and the waveforms, spectra, and directional diagrams of signals excited in geomaterials are calculated.
The effect of nonlinearity of rocks caused by the presence of microcracks on the shape of elastic pulses propagating in these rocks is studied by methods of ultrasonic laser spectroscopy.
Experimental device for ultrasonic laser echo sounding of geomaterials is described. The examples of its application to estimate acoustic characteristics, inhomogeneities, and damaged state intrinsic to structure sample of various-age volcanics are considered.
