In the construction of a tunnel, the characterization of the rock mass is performed in three different steps, in the pre-investigations, in the engineering geological forecast and in the tunnel mapping during construction. There has in previous work been observed that discrepancies exist between the results from these different steps, with a tendency to assign poorer rock mass quality in the tunnel mapping than in the pre-investigations and in the engineering geological\ forecast. One example is the work done by Kjellström [1] on the Cityline where the divergence in rock mass quality was analyzed between the different steps. If a divergence exists between the engineering geological forecast and the actual conditions observed in the tunnel mapping, it will influence both planning
and budget. It is therefore important that the engineering geological forecast is as close as possible to the actual rock mass conditions in the field.
The aim of this thesis was, using the case study of the Northern Link, to analyze those discrepancies in the rock mass quality estimated in the characterization and in the classification between the mapping of drill cores, the engineering geological forecast and the tunnel mapping thus complementing the work by Kjellström [1]. The aim was also identifying which parameters included in the Q system that causes these discrepancies.