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Managing uncertainties in geotechnical parameters

Time: Thu 2019-09-19 13.00

Location: Kollegiesalen, Brinellvägen 8, Stockholm (English)

Subject area: Civil and Architectural Engineering

Doctoral student: Anders Prästings , Jord- och bergmekanik

Opponent: Professor Kok-Kwang Phoon, National University of Singapore

Supervisor: Professor Stefan Larsson, Jord- och bergmekanik; Docent Johan Spross, Jord- och bergmekanik; Ph.D. Rasmus Müller, Tyréns AB

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Geotechnical engineering is strongly associated with large uncertainties. Geotechnical site investigations are made only at discrete points and most of a soil volume is never tested. A major issue is therefore how to cost effectively reduce geotechnical uncertainties with respect to structural performance. Managing the geotechnical uncertainties is thus an important aspect of the design process. Guidance on this subject is given in the European design code for geotechnical design, Eurocode 7 (EN 1997), which advocates the use of the partial-factor method, with the added possibility to use the observational method if the uncertainties are large and difficult to assess.This thesis aims to highlight, develop and improve methods to assess the quality and value of geotechnical site investigations through reliability-based design. The thesis also discusses the limitations of the deterministic partial-factor method, according to its EN 1997 definition, and how to better harmonise this design methodology with the risk-based approach of reliability-based design. The main research contributions are: (1) a presented case study showing the importance of and potential gains with a robust framework for statistical evaluation of geotechnical parameters, (2) the discussion on the limitations of the partial-factor method in EN 1997, and (3) the discussion on how to harmonise the EN 1997 definition of the partial-factor method with the risk-based approach of reliability-based design.