Scale factors for centrifuge modeling have traditionally been defined using dimensional analysis concepts. This is the case, for example, regarding centrifuge modeling of unsaturated water flow. However, scale factors governing suction, discharge velocity, and time that are obtained using dimensional analysis have often differed from those obtained from methodologies not based on dimensionless groups. A consistent framework is initially developed in this study for analytic determination of suction profiles under steady-state unsaturated flow for both natural and increased gravitational fields. This framework allows deduction of the scale factors, which emerge from direct comparison of the analytic solutions related to model and prototype without the need to use dimensionless groups. For centrifuge conditions leading to an approximately uniform acceleration field, the suction profile in the prototype is found to be the same as that in the model, while the discharge velocity is found to be properly scaled by 1/N and time by N2, where N is the average ratio of accelerations between model and prototype. In addition, evaluation of the effect of different experimental conditions allows identification of the suction profiles and test setup best suited for hydraulic conductivity determination using centrifuge techniques. The experimental component of this investigation involved the development of equipment suited to conduct unsaturated steady-state flow tests and to evaluate moisture profiles using time domain reflectometry (TDR). The equipment keeps the applied discharge velocity constant independently of the g-level applied. This new equipment allows studying the effect of increased gravity over the unsaturated flow pattern under constant boundary conditions. The mechanism of centrifugal unsaturated flow was studied using coarse, medium and fine-grained soils under identical boundary conditions. The experimental results indicate that for steady-state conditions with a constant discharge velocity boundary condition, the gravity increase results in a drying process that affects the model. The effect of g-level on the volumetric water content profile is found to be equal to 1/N, with seepage velocity increasing as a consequence of volumetric water content decrease. The moisture profiles observed experimentally were well predicted by the analytical solution, indicating that unsaturated flow can be properly modeled using a geotechnical centrifuge.
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