Framework for value of information analysis in rock mass characterization for grouting purposes

The observational method involves recurrent updating, and according to European standards, it is an optional method when geotechnical conditions are difficult to predict. A method for the application of value of information analysis in rock mass characterization for tunnels is demonstrated in a generic case of a feasibility study of a tunnel in hard rock. Two alternative grouting designs are analyzed to find the most suitable design for the geological conditions on site and whether information from investigations is of value in the decision-making process. The uncertainty in the grouting result is described by means of a beta distribution for each alternative design. The probabilities of different geological states are based on 200 stochastic simulations of the rock mass. It was found that value of information analysis contributes to good structure in geological surveys when the geology is difficult to predict and when repeated updating is necessary. The prescribed method is a tool to design well-motivated investigation programs where geotechnical value is weighed up against execution costs.