Reliability and Statistics in Geotechnical Engineering

Abstract

Applications of probabilistic methods in geotechnical engineering have increased remarkably in recent years. As we have worked on this book, we have encountered uses ranging from practical design and construction problems to advanced research publications. We have also found that many engineers are concerned about what these developments mean and how they can be applied with confidence. Our main goal in preparing this book has been to try to bring to the geotechnical and geological engineering profession a description of probabilistic methods that emphasizes both the underpinnings of the methodologies and their practical applications. There are many books on structural reliability theory and practice, and, of course, there are entire libraries of books on statistics and probability. However, the geotechnical world is different in many ways from the structural and mechanical worlds, and a book is needed that deals with reliability methods from a geotechnical point of view. Geotechnical engineers and geologists deal with materials whose properties and spatial distribution are poorly known and with problems in which loads and resistances are often coupled. Thus, a somewhat different philosophical approach is necessary. Historically, the geotechnical profession has dealt with uncertainty on important projects by using the ‘observational’ approach; this is quite compatible with reliability-based methods. We have tried to steer a middle course between an abstract, mathematical treatment so typical of many graduate texts on statistics and a purely practical presentation that reduces all methods to a set of recipes. We have also had to choose among the wide range of probabilistic material in geotechnical engineering and geology. Inevitably, this means that we go more deeply into some subjects than others. In making such choices, we have been guided by our view of what is important to geotechnical practice. The book is organized in four parts. Part I introduces concepts of uncertainty, probability, reliability, statistics, and risk. It discusses both practical considerations and philosophical issues that have existed as long as probability theory itself. Part II deals with uncertainty in a geologic or geotechnical context. It deals with issues of uncertainty in engineering properties and the spatial variation of soils and rocks. Part III describes how reliability analyses are performed. It surveys important methods and provides detail on various models. Part IV presents applications of reliability and probabilistic methods to practical problems. It also addresses how probabilistic information is obtained and man