Application of Rhizon SMS for the assessment of the hydrodynamic properties of unconsolidated fine grained materials

• We derive hydrodynamic data from pore water sampling using Rhizon SMS devices.
• The test is made in an experimental column with granite fines of known properties.
• The fines are sequentially saturated while being monitored by X-ray absorption scans.
• Hvorslev's and Gil-Gavard's methods are used to assess hydraulic conductivities.
• Results show good agreements with the theoretical Mualem–Van Genuchten model.

A column experiment has been performed in order to derive hydrodynamic data from pore water sampling using Rhizon soil moisture sampler (SMS) devices. The column was filled with dry granite fines (a fine grained material of well-known properties), saturated with tap water and the evolution of saturation was monitored with the aid of X-ray absorption scans. Once saturation was completed, seven equally-spaced Rhizon samplers were introduced in the column and a 4-stage sequential pore water extraction process conducted. For each Rhizon sampler, flow was carefully recorded in each stage and the data obtained has been interpreted considering the sampling device as being analog to a slotted-casing low-diameter piezometer and the extraction a bail-down type hydraulic test. A modified Hvorslev's and the Gilg-Gavard's methods have been used to assess the hydraulic conductivity during extractions. Experimental results, including unsaturated parameters based on the MVG model, show a good agreement with literature reported data for granite fines, at least up to a hydraulic conductivity of ~ 10− 8 m s− 1. Although further tests are needed to check the applicability of the methodology described to materials with different granulometry and/or with concentrated pore solutions the available results show that Rhizon samplers are good candidates for the hydrodynamic assessment of sediments.