The Hydraulic Properties of Aquabeads Considering Forchheimer Flow and Local Heterogeneity

A transparent water-based polymer named Aquabeads has been recently applied to model natural soil because its high transparency facilitates studies of the geotechnical problems using the visual technique. Before physically modelling flow in the hydrated Aquabeads, it is necessary to determine its hydraulic properties. According to many previous studies, the noncrushed Aquabeads were gravel-size particles but had the hydraulic conductivity (k) of clean medium sand under unconsolidated conditions. For investigating this inconsistency, the constant head tests are conducted using a rigid wall permeameter in this study. The preliminary results show that the k calculated using Darcy’s law highly agree with prior studies. However, the nonlinearity between the hydraulic gradients and Reynolds numbers (Re > 1) indicates the non-Darcy flow regime. Also, an initial hydraulic gradient was observed, thus raising concerns about local heterogeneity. With multiple manometer readings, the analysis for each layer shows that the k decreases from top to bottom with flow regimes transition. After each test, a layer of crushed samples was found on the porous plate when unloading the specimen. In conclusion, Darcy’s law is only robust to calculate the k of partially crushed Aquabeads for Re < 1. Instead, Forchheimer flow should be considered in future physical modelling work for Re > 1. The inconsistency is due to inevitably sample crushing.