ABSTRACT
The natural variability of soil properties is dealt with daily by geotechnical engineers, usually in an ad-hoc manner to answer deterministic questions. To answer questions relating to low risk events, the relativity of safety factors or other uncertainties, the variability of the properties must be explicitly taken into account. The soil properties are modelled as a random field and the data statistics associated with this concept are reviewed. The properties governing most geotechnical behaviour are the average properties over some spatial domain and methods of assessing these average values and their uncertainties are presented. The importance of self-correlation of the properties and the importance of the concept of correlation distance is emphasised.
