RSC-Programme - Interim Report. Approach and Basis for - Posiva

13with respect to geological parameters such as rock types, fracture/deformation zoneintersections, fault properties and kinematics, foliation, lineation, folding, weathering,etc. This data serves geological modelling, detailed geological characterisation anddecisions on final rock support.Hydrogeological tunnel observationsThe significance of mapped and modelled geological and/or hydrogeological zones tothe HRC is to a great extent determined by the hydrogeological properties of the zonesobserved in pilot holes. Therefore, hydrogeological investigations performed in thetunnel pilot holes were checked against water leakage observations in the correspondingsection of excavated tunnel. The HRC suggests the usage of Lugeon tests (water lossmeasurement from the probe holes) and water leakage mappings for testing of pilot holedata in the tunnel. The applicability of the Lugeon tests was, however, poor.Furthermore, water leakage observations at the time of testing are affected by theextensive grouting in the tunnel sections used for testing.2.2.3 ResultsFor a detailed description of the testing results, see Lampinen (2008). An example of theclassification results is given in Figure 2-1.Results from the pilot holesFor all tested pilot holes, a rock suitability classification map was constructed (for anexample, see Figure 2-1), based on the core loggings and hydrogeological data, in orderto test the implementation of the HRC procedure (Lampinen 2008). The suitability mapdivides each pilot hole into suitability classes suggested in the HRC (see Section 2.2.2).Site models 2003/1 (hydrogeological model, Vaittinen et al. 2003) and 2006 v.0(geological model, Paulamäki et al. 2006) were used in the characterisation of brittledeformation zones in order to compare the applicability of the two site models for HRC.According to pilot hole data from ONK-PH2…ONK-PH5, c. 42–83% of the rock masscould be classified as suitable for spent fuel disposal according to the HRC. Theclassification results based on the two site models gave similar results. In pilot holeONK-PH5, the difference was largest as the proportion of rock mass suitable fordeposition varied from c. 42% (model 2006 v.0) to 49% (model 2003/1). Thedifferences between the two models are mainly due to differences in the definition ofthe deformation zones in the pilot holes. According to current views, the use of both(hydrogeological and geological models) is suggested for the purposes of the RSC, anapproach now occupied in the development of new criteria.Suitability of the rock mass for spent nuclear fuel disposal was primarily reduced by thepresence of brittle deformation zones with high hydraulic conductivities. However, Q'-value appear to be an inadequate parameter for detecting zones significant from thelong-term safety point of view. Good rock constructability does not cover all rockproperties affecting the suitability of the rock for disposal of spent fuel. In other words,pilot hole sections may, despite giving a high Q'-value, contain geological orhydrogeological intersections that within the repository would be considered significantfor long-term safety of the repository. In addition, Q'-values obtained from the pilotholes did not always correspond to Q'-values observed in the corresponding tunnelsection. The suitability classification according to HRC procedure was therefore mainly