Probability of failure of slopes. Application to slopes of a granitic residual soil

It is studied the stability of slopes of a granitic residual soil from the city of Braga in the north region of Portugal. This stability is based on probabilities. The confiability index of the factor of safety and the probability of failure are computed. The confiability index is computed as a function of the mean and standard deviation values of the factor of safety. The mean value of the factor of safety is considered the minimum value of this factor obtained using the Bishop method with the average values of the geotechnical parameters (phi, c and gamma). The probability of failure is the probability of the factor of safety be less than or equal 1 and is obtained assuming a normal probability distribution. It is analyzed the relative weight of the geotechnical parameters in the factor of safety. A parametric study varying the height and the inclination of the slope is also performed.