4TH International Congress on Technology - Engineering & SCIENCE - Kuala Lumpur - Malaysia (2017-08-05)

Hydraulic Characteristics Of Porous Beds Consisting Of Randomly Packed Polymer Beads
Transparent water-based polymer named Aquabeads is recently applied to model natural soil due to its high transparency facilitates study geotechnical problem by visual technique. Before modeling the flow, it is necessary to precisely determine its permeability. The previous geotechnical testing for Aquabeads permeability determination always takes Darcy law as a benchmark. However, a large amount of previous literature approved its failure for gravel size porous media. Because previous studies all overlook this issue, the porosity, grain size distribution, and hydraulic conductivity are retested. Although the hydraulic conductivities (K) given by Darcy’s law highly agree with previous studies, the experimental results show nonlinearity between hydraulic gradient and Reynolds numbers (Re>1). Also, an initial gradient raised concern about sample deformation and particle crushing after the setting up different strata. Experimental results demonstrate the existence of multilayers in this study. Hydraulic conductivities are individually determined for each layer. The granular Aquabeads only located in the most upper layer, in which flow regime follow Forchheimer’s law. For the layers below, the granular form cannot be maintained so Darcy’s law is still applicable. The hydraulic conductivity for the entire specimen is mainly dependent on the low permeability of bottom layers. Simply applying Darcy’s law to determine hydraulic conductivity of Aquabeads is not suggested. Instead, it should be characterized by each layer with correct flow motion equations.
Guanxi Yan, Tilman Bittner, Ye Ma, Alexander Scheuermann