Dr. King-St-Onge, Robert

The effects of physical and chemical weathering processes in completely decomposed granitic rocks strongly condition the shear strength parameters commonly used in soil mechanics, where soils have high variability. The technological progress and the joint use of deterministic and probabilistic methods allow for the incorporation of soil variability within the calculations. This paper presents a probabilistic slope stability analysis using a model of random variables to characterize the shear strength parameters. The Monte Carlo simulation is used for generating the values ​​of the random variables, which also allows for the simultaneous evaluation of slope stability in terms of the factor of safety, probability of failure and reliability index. The results of this methodology tend to be more conservative, considering the risk of using average safety factors to evaluate stability when considering the variability of soil properties.

Granitic residual soils are soils formed by the in situ weathering of intrusive granitic rocks and are present in different parts of the world. Due to their large presence, many civil engineering projects are carried out on and within these soils. Therefore, a correct characterization of the slopes is necessary for slope stability studies. This investigation aims to study the influence of the values of geomechanical parameters (specific weight, cohesion, and friction angle) and the geometry of a slope (height and inclination) on slope stability of residual granitic soils in dry and static conditions. To this end, an automatic system was developed for the numerical study of cases using the finite element method with limit analysis. The system allows modeling, through Monte Carlo simulation and different slope configurations. With this system, the safety factors of 5000 cases were obtained. The results of the models were processed through the SAFE toolbox, performing a Regional Sensitivity Analysis (RSA). The results of this research concluded that the order of influence of the factors were: slope angle > slope height > cohesion > friction angle > unit weight (β > H > c > ϕ > γ).