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

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 andwaviness along with roughness, appropriate filters were applied to remove form andwaviness 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

Shear Strength Behavior of Different Geosynthetic Reinforced Soil Structure from Direct Shear Test

This paper presents the results of direct shear test on soil samples reinforced with geosynthetics, conducted with the aim of characterize the shear strength of reinforced soil composite. Two types of granular soil (well graded sand and silty sand) and four types of geosynthetic (woven and nonwoven geotextile—uniaxial and biaxial geogrid) were selected. Laboratory testing program were performed in two shear boxes, circular box with 63 mm in diameter and square box with 100 mm in length; the samples were made with loose and dense sand; the reinforcement layer was placed perpendicular to the failure surface; tests are conducted with three vertical confining pressures: 15.7, 31.4 and 62.8 kPa. The effect of different factors that influence the results of the shear tests is analyzed, such as: the particle size of soils, density of soils, shear box size and type of geosynthetics. The test results reveal that the maximum value of shear strength improvement was achieved for dense silty sand samples reinforced with biaxial geogrid. In general, the improvement was more favorable for samples reinforced with geogrid compared to samples reinforced with geotextile.Fil: Useche Infante, Danny Jose. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Civil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Aiassa Martinez, Gonzalo Martin. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Civil; ArgentinaFil: Arrua, Pedro Ariel. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Civil; ArgentinaFil: Eberhardt, Marcelo Gabriel. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Departamento de Ingeniería Civil; Argentin