Reliability analysis of earth dams using direct coupling
Adrian Torrico Siacara, Gian Franco Napa-García, André T. Beck, Marcos Massao Futai
Abstract
Numerical methods are helpful for understanding the behaviors of geotechnical installations. However, the computational cost sometimes may become prohibitive when structural reliability analysis is performed, due to repetitive calls to the deterministic solver. In this paper, we show how accurate and efficient reliability analyses of geotechnical installations can be performed by directly coupling geotechnical software with a reliability solver. An earth dam is used as the study object under different operating conditions. The limit equilibrium method of Morgenstern-Price is used to calculate factors of safety and find the critical slip surface. The commercial software packages Seep/W and Slope/W are coupled with StRAnD structural reliability software. Reliability indices of critical probabilistic surfaces are evaluated by the first- and second-order structural reliability methods (FORM and SORM), as well as by importance sampling Monte Carlo (ISMC) simulation. By means of sensitivity analysis, the effective friction angle (ϕ′) is found to be the most relevant uncertain geotechnical parameter for dam equilibrium. The correlations between different geotechnical properties are shown to be relevant in terms of equilibrium reliability indices. Finally, it is shown herein that a critical slip surface, identified in terms of the minimum factor of safety (FS), is not the critical surface in terms of the reliability index. Keywords: Earth dam, Geotechnical parameters, Reliability analysis, Water level