Uncertainties in characterising soil properties

The paper presents a review of the uncertainties in characterising soil properties, including spatial variability and measurement methods. It stresses the importance of characterising these uncertainties for design. The usefulness of determining and, where possible reducing, the uncertainties is illustrated with examples from actual case studies. To characterise the uncertainties in a soil property, the engineer needs to combine, in addition to the actual data, knowledge about the quality of the data, knowledge on the geology, and most importantly engineering judgement. When sufficient data are available, site description strategy, with the identification of correlation structure and stochastic interpolation to estimate a soil property is recommended. The geotechnical parameters for analysis are then more clearly defined. The added knowledge obtained from systematic uncertainty assessments should lead to safer and more economical designs. Accounting for uncertainties in soil properties and the calculation model is a necessary complement to more conventional deterministic analyses. A documentation that all possible aspects have been considered and dealt with is essential today, as quality assurance requirements grow. One challenge is to balance technology with complexity, given the budget and the consequences of the project. Accounting for uncertainties in an analysis and their effects on the response contributes to an improved understanding of the complexity of the problem to model.