Surface topographical analysis of geomembranes and sands using a 3D optical profilometer

Abstract

Understanding the stress-displacement response of granular materials and their interfaces with geosynthetics through surface topographical analysis is evolving as a new area of potential interest. Recent developments in optical techniques coupled with digital image recording have enabled the measurement of the surface topographical features of sand particles and geosynthetics, which can be applied to measure the shear-induced surface changes in geomembranes. This paper presents one of the latest, advanced surface measurement techniques based on coherence correlation interferometry using a 3D optical profilometer. An experimental technique was developed to measure the surface topography of sand particles, and the shear-induced surface changes in a smooth geomembrane caused by sand particles of different mean sizes, in interface direct shear tests. As the measured surfaces consisted of form and waviness along with roughness, appropriate filters were applied to remove form and waviness and measure the roughness of the surfaces. The selection of these filters for different cases and the spatial variability of surface roughness measurements are discussed. The results of the surface topographical analysis of sand particles of three different sizes, geomembranes sheared by sands of three different mean sizes, and their repeatability, are presented. The stress-displacement response of the sand–geomembrane interfaces is correlated to the surface changes on sheared geomembranes through visual observations and roughness quantifications.