In the design of Swedish infrastructure projects today, the prognosis of grouting measures is generally presented as a distribution of grouting classes. Each grouting class describes the number of grouting rounds, grouting fan geometry, grout properties, the extent of controls, etc. The distribution of grouting classes is used as input to the bill-of-quantities, as well as information for the contractors overall planning. This means that the design of grouting classes and their distribution is an important basis for the project. However, the methodology of determining the grouting class distribution varies between different project. Reasons for the differences can for instance be the available information or the determined strategy of the project. The difference in methodology can hence result in spatial uncertainties of the distribution. Inherent uncertainties of the distribution are usually not described in the design.
In the article, examples of methodologies to describe the prognosis of grouting classes applied in infrastructure projects in Sweden are presented. For the access tunnels in the extension of the metro project in Stockholm, the determination of grouting classes is described. The determination is based on the environmental permit, the sealing demand and the groutability of the rock mass.