Risk assessment of slope stability

The world has become more vulnerable to disasters caused by hazards such as landslides and earthquakes. In geotechnical engineering, slope stability is perhaps the subject most dominated by uncertainty. The main deficiency with deterministic analysis is that it cannot explicitly consider parameter uncertainties, and a significant ambiguity lies in the relation between the factor of safety and the corresponding level of risk. The concept of reliability index beta introduces a better approach to assessing risk. Two cases are considered. First, the effects of the presence and the fluctuation of a phreatic surface on slope stability are discussed. The reliability index is analyzed as a function of correlation coefficients rho involving friction angle phi, cohesion c and pore water pressure u. The most probable failure point (limit state) seems to be affected more by p(cphi) than by p(cu) or p(phiu). In the second case, additional risk due to earthquakes is estimated for slopes with simple failure modes.