Effects of Spatial Variability on Slope Reliability: A Hypothetical Case Study

E. Muñoz, M.P. Cordão Neto, A. Ochoa

Case Study

Soils and Rocks, São Paulo, 41(3): 381-390, September-December, 2018 | PDF


Abstract

Due to the complexity and uncertainty involved in mass movements, it is not possible to predict their occurrence with accuracy. This uncertainty is due to the space-time variability of physical soil parameters and processes, which determine the boundary conditions of the problem. In this study, we analyzed the influence of spatial variability of the parameters that determine soil resistance, the water retention curve and the unsaturated hydraulic conductivity function on the Factor of Safety of a hypothetical slope. To determinate the parameters to which the slope is more sensitive, we carried out a sensitivity analysis using the First-Order Second-Moment Method. We assumed that spatial variability follows normal and lognormal distribution, by using a methodology based on Monte Carlo Simulations and a Kriging process. The water flow equation is solved using numerical methods and the Factor of Safety was found with the Limit Equilibrium Method. According to the sensitivity analysis, the parameters that most affect the stability of the slope analyzed are cohesion, friction angle, air-entry value, and saturated hydraulic conductivity. When varying the air-entry value and cohesion, the probability distributions have very low dispersion, and mode has values similar to the deterministic values of Factor of Safety. The hydraulic conductivity variation results in that the values of mode move further away from the deterministic Factor of Safety as time progresses, increasing at the same time the dispersion. When all parameters are varied simultaneously, the behavior of the Factor of Safety is highly influenced by the hydraulic conductivity.


Submitted on September 8, 2017; Final Acceptance on September 18, 2018; Discussion open until April 30, 2019. DOI: 10.28927/SR.413381