Stability Analysis of Infinite Unsaturated Soil Slope Based on Analytical Probabilistic Approach

Abstract

Most infinite slopes in tropical climates are frequently unsaturated in the beginning, and along with many soil properties like cohesion and friction, stability of these slopes is largely dependent on matric suction. These parameters are highly variable in the evaluation of slope stability for unsaturated soil. Hence, deterministic analysis is not enough to draw conclusions regarding stability of unsaturated slopes. This paper presents an analytical probabilistic method based on the theory of multivariate probability distribution to determine the stability of infinite unsaturated slopes. The stochastic soil parameters used in the study are cohesion, friction angle, unit weight, and matric suction. All the stochastic parameters were treated as uncertain variables which were defined by the normal distribution. The geometry-related parameters such as slope angle, slope height, and few stress variables such as net normal stress were regarded as deterministic parameters. The stability of the slope was determined by calculating the reliability index. Furthermore, the calculation formula for the probability density of slope safety factors was established. To inspect the correctness of the present methodology, the probability density of safety factors was determined by considering a conceptual infinite slope with arbitrary parameter values. Results showed that for the assumed set of parameters, the slope fails to meet the reliability index criteria of stability. A comparison between the outputs determined by the proposed technique and the Monte Carlo method indicates that the proposed methodology is efficient in order to calculate the stability of unsaturated slopes while taking the variability of various soil characteristics into account.