AMPLITUDE-DEPENDENT EFFECTS IN A TRANSMITTED WAVE IN CEMENTED SANDSTONE UNDER PRESSURE
This paper presents the results of experiments on the effect of variable amplitude and pressure on the <i>P</i>-wave velocity and attenuation in cemented sandstone sample. The measurements were performed in transmitted waves at a predominant pulse frequency of 6.8 kHz in the range of strain amplitudes <i>A</i><sup><i></i>ε</sup> = (0.2-2.4)·10<sup>-6</sup> at an axial static pressure of 0.25 MPa to 1.0 MPa. The wave velocity depends weakly on the amplitude and decreases only slightly with its increase. With increasing pressure the velocity <i>v</i><sub><i>e</i></sub><i></i> nonlinearly increases (to 6%) at all amplitudes. The attenuation <i>Q</i><sub><i>e</i></sub><i></i> increases linearly (to 2.5%) with increasing amplitude and decreases nonlinearly with increasing pressure. There is an anomalous change in the attenuation in the pressure range (0.5-0.75) MPa, where it decreases to 30 % at all amplitudes. These results may be useful for improving acoustic and seismic methods of diagnostics.