3D Analysis of Surface Topography of Sand Particles Using Spectral Methods

The surface roughness of the particles in a granular material plays a significant role in its engineering behavior. Because the microsurface features that contribute to the roughness are highly complex and irregular in nature, precise topographical measurements and a mathematically rigorous computational approach are needed for the accurate quantification of surface roughness. In this study, surface roughness of particles from three different sands that represent different sizes and shapes was quantified using spectral methods. A 3D noncontact optical profilometer was used to obtain a high-resolution representative scan area of sand particles. Higher-order moments of the power spectral density (PSD) were used to compute surface roughness parameters such as asperity slope and curvature. The surface roughness values were found to increase with the slope and curvature of the asperities. The value of asperity density, which has a physical significance in contact mechanics, was estimated to be about eight for all type of sands studied. Fractal analysis was carried out on the data obtained from profilometer and microcomputed tomography (mu CT) scans to compute the fractal dimensions of sand particles using these two different instruments and compare them. Further, the angle of repose of different sands was correlated to their surface roughness.