Anisotropy in ultrasonic pulse velocity and dynamic elastic constants of laminated sandstone

Abstract

Some rocks of the crust, such as sandstones, contain fabric elements including lamination. In general, these rocks show anisotropic behaviour. In this study, anisotropic behaviour of ultrasonic pulse velocities (Vp and Vs) and dynamic elastic constants (elastic modulus (E) and Poisson's ratio (ν)) were investigated for a laminated sandstone. For this purpose, some cylindrical specimens of the sandstone were prepared at angles (β) of 0°, 30°, 45°, 60° and 90° to lamination direction. The Vp, Vs, E and ν were measured for the specimens for the different β values. The study confirms that anisotropy is one of the most important factors affecting V­, Vs, E and ν. The obtained results reveal that Vp, Vs and E show a decreasing trend with an increase in β from 0° to 90°; whereas ν shows an increasing trend. According to the values of maximum and minimum Vp, Vs, E and ν for different β values, anisotropy ratios for sandstone samples are 1.16, 1.26, 1.52 and 1.15, respectively. Finally, it can be concluded that calculated Vp, Vs, E and ν corresponding to different β values are useful for the analysis and design of geotechnical projects in the absence of borehole explorations.