A Review on Soil-Water Retention Scaling in Centrifuge Modeling of Unsaturated Sands

摘要

Centrifuge testing has been increasingly implemented to characterize the mechanical and hydraulic behavior of partially saturated soils. Common procedures include unsaturated flow and capillary ascending from an identified water table. The employment of these methods involves experimental challenges, including ways to generate, control, and measure water content and suction in soil as well as mapping the model results to their prototype values. This article summarizes and reviews the state-of-the-art in centrifuge testing of unsaturated soils and presents the results of a set of centrifuge experiments on unsaturated fine sand layers. The unsaturated condition was developed following two procedures, i.e., steady state infiltration and capillary rise from a saturated zone, and the results were presented in terms of volumetric water content and matric suction. Discharge velocity and centrifuge gravitational field were varied to obtain different uniform degrees of saturation profiles during the steady state flow. The capillary ascending was investigated at different g-levels where the specimen underwent a drying path from a fully saturated condition by consecutively lowering the water table. The results demonstrated a negligible influence of the g-level on the Soil Water Retention Curves. Significant hysteresis was observed during the tests involving steady state infiltration. Although, because of the capillary finger phenomenon, capillary ascending did not occur uniformly along the soil layers, the length scaling factor of 1/N was successfully employed to project prototype capillary height to its model value.