Risk and reliability assessment in geotechnical engineering

In geotechnical engineering practice, risk assessments play a crucial role in accounting for uncertainty and facilitating informed decision-making. Traditionally, the method of assessment is very basic, and many important factors are often overlooked in the early design stages leading to time and/or cost overruns during construction.

This technical paper presents an exploration on the importance of geotechnical risk assessments in the early concept design stages of a project and is organised in two parts. The first part compares two distinct methods of risk assessment, namely GIS-supported analysis vs non-GIS analysis. In this part, the details from selected case histories are used to demonstrate the merits and limitations of each method. The second part spotlights a key element of risk assessment which is the reliability assessment of existing geotechnical data and information. A reliability assessment framework is proposed and discussed in relation to factors such as age of information, geological context, horizontal spatial relevance, and relevance of geotechnical design parameters. It compares the materiality of the different factors and discusses the relevance of several other factors including the objectivity and uniformity in applying the framework.

The value of the framework and methodology is demonstrated through a highway upgrade project in Queensland, Australia, involving multiple interchanges and bridges. In conclusion, this paper affirms the essential role of geotechnical risk assessment, particularly in systematically quantifying ground uncertainty and its consequences to improve project outcomes.