Probabilistic analysis of unsaturated residual soil slopes

In order to study the effect of infiltration on the stability of an unsaturated residual soil slope, the Soil-Water Characteristic (SWC) curve and the Permeability Function (PF) are needed. Uncertainties about these two relationships are observed to exist due to errors in field or laboratory measurements, assumptions in the modeling process and spatial heterogeneity. In this paper, the SWC curve and PF are modeled using van Genuchten and Mualem relationships, respectively. Two programs, SLOPE/W and SEEP/W, are used to evaluate the change in the factor of safety resulting from rainfall infiltration. The impact of uncertainties associated with the characterization of SWC curve and PF on the factor of safety is studied using Monte Carlo simulation which is implemented by running the programs repetitively using a Windows batch programming software, WinBatch.