Permeability of layered glass bead samples

Abstract

Geotechnical projects are successful when there is a lot of knowledge about the soil implemented in safe sustainable solutions. Existing models of hydraulic flow in soils need to be tested and confirmed again and again to make sure it’s trustworthy. With the use of three-layered samples containing 1mm and 3mm glass bead sizes a simplified model of the fining upward (1mm top layer) and coarsening upward (3mm top layer) stratification was made. The top and bottom layers consist of a uniform glass bead size. The middle layer is a binary mixed one with different volumetric percentages to mimic the gradual increase of grain sizes like fining and coarsening upward sediment deposits. A decrease in the permeability was observed as the volume percentage of the smaller glass beads increased. The influence of a possible transition/mixed zone between layers was not clear because of the small ratios of the used glass beads. This is also the case for the effect of the porosity on the permeability. In addition, test samples were prepared to calculate the theoretical harmonic permeability to be able to compare it with the actual measured permeability. This theoretical harmonic permeability seems in the case of the coarsening upward samples smaller than the actual measured permeability as was expected from findings of another research. This study confirms the influence of the relative positioning of the layers with their specific properties on the overall permeability and the deviation from the theoretical harmonic permeability. Future prediction of the permeability’s in layered deposits is a little bit more educated with the findings of this study.