Abstract

Understanding of the relationship between volumetric water content (q) and soil capillary pressure (ψ), and between unsaturated hydraulic conductivity K and ψ is important in the analysis of rainwater infiltration into soil and its effect to slope stability. These relationships are known as the water retention curve and the hydraulic conductivity function, respectively. Much soil water retention-hydraulic conductivity models have been proposed such as Brooks-Corey (BC), van Genuchten (VG) that were derived based on empirical fitting curve, and Lognormal (LN) distribution model derived based on soil pore radius distribution. In this study, numerical simulations were performed using the three models to estimate the extent of rainwater infiltration into an unsaturated slope; the formation of a saturated zone, and the change in slope stability. Comparisons were made in terms of soil moisture, water movement phenomena in a soil slope, and the slope stability characteristic. The results of the numerical simulation shows that although BC, VG and LN models have different value of initial condition, the outcome of soil moisture content, water movement and slope stability characteristic are very similar during rainstorm event.

Key words: Soil hydraulic properties, water retention-hydraulic conductivity mode, slope stability analysis.