Full Probabilistic Analysis with FEM for the Retaining Wall of a Deep Excavation

Abstract

Complex probabilistic approaches for the analysis of structures have been increasing in interest and application both in the area of research and in practice in order to provide a more uniform level of reliability. Also, the design codes, such as the Eurocodes, are developing provisions to address reliability-based design methods in more detail. Moreover, FEM is very popular nowadays using advanced constitutive laws and modelling staged construction. This is especially important for geotechnical structures, such as retaining walls for deep excavations, for which soil-structure interaction is a complex mechanism. The paper will present a full probabilistic analysis performed for a real case temporary retaining wall of a deep excavation. The probabilistic analysis was combined with FEM using advanced constitutive models. The objective is to demonstrate the feasibility of a full probabilistic analysis, using the current advanced design methods, and to assess the reliability produced by Eurocode designs. The main uncertainties were modelled as random variables and the limit state verification was expressed in terms of reliability index or, equivalently, the probability of failure for SLS and ULS verification. The procedure of coupling probabilistic analysis using Probabilistic Toolkit reliability software with FEM Plaxis 2D commercial software for geotechnical analysis is given in detail while emphasizing some critical aspects in relation with these types of combined analyses and reliability concepts. At last, some issues related to the provisions of the current design codes are presented and discussed in order to facilitate the implementation of reliability-based design, either through probabilistic methods or by partial factors.