Unsaturated Permeability and Retention Curve Determination From In-Flight Weight Measurements in a Bench-Scale Centrifuge

Abstract

Centrifuges have been used in many ways to determine permeabilities, as they can significantly shorten testing times in low-permeable soils. Typically equilibrium profiles, inflow-outflow measurements, or direct measurements from inside the sample-like from tensiometers or radioactive decay-are used. Recently, weight measurements of the sample outside the centrifuge were used effectively in an adapted setup. We present the results of the possibilities offered by doing transient weight measurements of a soil-sample during rotation in the centrifuge. We present the setup of such an experiment and how the unsaturated permeability and water retention curve can be recovered from it. This eliminates the overhead of doing measurements inside the sample.

Development and validation of the steady state centrifuge experiment for the moisture retention curve of porous building materials

“…This rotation produces a capillary pressure in a sample which, combined with the measured moisture content of the sample, can be used to compose the material’s moisture retention curve. Two different centrifuge experiments are commonly used for hygric property determination; steady state (Chen and Balcom, 2005; Khanzode et al, 2002; Lozano et al, 2020; Reatto-Braga et al, 2008; Vero et al, 2016) and transient centrifugation (Malengier et al, 2015; Nakajima and Stadler, 2006; Nimmo, 1990; Nimmo et al, 1987; Šimůnek and Nimmo, 2005). In steady state centrifugation, saturated samples are rotated until they reach their equilibrium moisture content.…”

“…Their results show good agreement with steady state centrifuge experiments on the same Oakley sand (Šimůnek and Nimmo, 2005). Further validation of the transient centrifuge technique is provided by studies on different soils and by comparison with results obtained from other more commonly used experimental techniques such as pressure plate tests (Malengier et al, 2015; Nakajima and Stadler, 2006).…”

Combination of Measurement Methods for a Wide-Range Description of Hydraulic Soil Properties

“…Multi-step outflow experiments are also done in centrifuges. A sequence of water heads is applied via rotation and centrifugal force and water content and outflow rates are measured [10,11]. This approach has been continuously developed to eliminate practical issues like consolidation of undisturbed samples [12].…”