Analysis of quality factors for Rayleigh channel waves

To facilitate investigation of the effect of imperfect elastic dissipation on the propagation of Rayleigh-type channel waves and use of their quality factors in investigations of the properties of coal seams, a simple method for calculating the quality factor QR is proposed in this paper. Introduction of complex velocities into the dispersion function allows calculation of the dispersion function of Rayleigh-type channel waves in coal seams. By the control variable method, we analyzed changes in QR with changes in coal seam thickness and P-and S-wave Q-factors within the coal seam and adjacent rock layers. The numerical results show that the trend of the QR curve is consistent with the group velocity curve. The minimum QR value occurs at the Airy phase frequency;the Airy phase frequency decreases as coal seam thickness increases. The value of QR increases with increasing QS2 (quality factor for S wave in coal seam). We can compensate for the absorption of Rayleigh-type channel waves using the computed QR curve. Inversion of the QR curve can also be used to predict the thicknesses and lithologies of coal seams.