ABSTRACT
When designing underground excavations in rock, the engineer must inevitably consider the uncertainties related to the properties of the rock in one way or another. A common approach is to be conservative in the design, but this is not always economically sound or possible in practice. For situations when it is difficult to predict the geotechnical behaviour, Eurocode 7 (CEN 2004) suggests applying the observational method. This method was first outlined by Terzaghi and later defined by Peck (1969).
