Infiltration analysis to evaluate the surficial stability of two-layered slopes considering rainfall characteristics

Shallow slope failures in residual soil during periods of prolonged infiltration are common throughout the world. Using a one-dimensional infiltration model and an infinite slope analysis, this study examines an approximate method of determining how infiltration influences the surficial stability of two-layered slopes. The method extends Moore's infiltration model, which is based on the Green–Ampt model, to cover more general situations, including those where water moves upward from a perched water table in decreasingly permeable soil. The method has also been used to evaluate the likelihood of a shallow slope failure being induced by a particular rainfall event. In making this evaluation, the method takes into accounts the rainfall intensity and duration of various return periods in a two-layered soil profile. A comparison of the results of the infiltration model with the results of numerical analyses shows that, with the use of properly estimated input parameters, the proposed model compares reasonably well with other model that rely on more rigorous finite element method.