Experimental and Numerical Investigation of One-Dimensional Infiltration into Unsaturated Soil

Abstract

Infiltration characteristics of an unsaturated soil are of interest in both seepage and stability analyses and should be evaluated carefully. In this study, a new large-scale one-dimensional infiltration column test setup was developed, with an inner diameter of 0.24 m and a length of 1.3 m. In the tests conducted, 1.0 m of the column height was filled with soil and 0.3 m remained above for constant water head. The column was instrumented with five pairs of in-situ volumetric water content sensors and suction sensors. This paper explains the methodology used in the construction of the test setup and how the unsaturated properties were calculated for the tested soil, namely the soil water characteristic curve (SWCC) and soil permeability function (SPF). Infiltration tests were performed on a fabricated homogeneous clayey sandy silt similar to naturally available materials representative for Norwegian conditions. Soil specific SWCCs were established under steady state boundary conditions using the sensor outputs, and the results are presented. The instantaneous profile and wetting front advance methods, and relationships based on the SWCC were utilized to establish SPFs, and the results are discussed. A sensitivity analysis was run on the SWCC curve fitting parameters and effects of the parameters on infiltration time are presented. The results from the combined experimental and numerical analysis show that it may be possible to use the new test setup to develop unsaturated soil relationships, but accuracy and measurement range of the sensors are crucial to obtaining consistent results.