Jordan Journal of Civil Engineering

Comparative Deterministic and Probabilistic Analysis of Two Unsaturated Soil Slope Models after Rainfall Infiltration


Manoj Kr. Sahis; Partha Pratim Biswas;


The prime aim of this paper is to develop a computational scheme for the reliability analysis of two unsaturated natural slope models after rainfall infiltration, considering the uncertain system parameters as random variables. Analysis has been conducted within the framework of the well known ‘infinite slope’ limit equilibrium model, suitably modified to take into account the shear strength for a partially saturated soil. The pore pressures in the shear strength equation may be positive or negative, depending on the position of the potential failure plane in relation to the water table or phreatic surface, and, more importantly, in relation to the wetting front at any given time. Analysis of the time dependent process of infiltration and the progression of the wetting front is based on the widely known Green-Ampt model. The developed model is based on an approximate, yet simple method; namely Mean Value First Order Second Moment (MVFOSM) method of reliability analysis, treating the basic geotechnical parameters as random variables, where the random variables are assumed to be normally distributed and uncorrelated. The analysis clearly brings out the importance of carrying out a reliability analysis under the probabilistic framework.


Reliability analysis, Unsaturated slope models, Rainfall infiltration, Green-Ampt model.