Technical Report NTB 89-23
Stripa ProjectSite characterization and validation Stage 2Preliminary predictions
The Site Characterization and Validation (SCV) Project is designed to assess how well we can characterize a volume of rock prior to using it as a repository. The programme of work focuses on the validation of the techniques used in site characterization. The SCV Project contains 5 stages of work arranged in two "cycles" of data-gathering, prediction, and validation. The first stage of work has included drilling of 6 boreholes (N2, N3, N4, W1, W2, and V3) and measurements of geology, fracture characteristics, stress, single borehole geophysical logging, radar, seismics, and hydrogeology.
The rock at the SCV site is granite with small lithological variations. Based essentially on radar and seismic results 5 "fracture zones" have been identified, named GA, GB, GC, GH, and GI. They all extend across the entire SCV site. They are basically in two groups (GA, GB, GC and GH, GI). The first group is aligned N40°E with a dip of 350 to the south. The second group is aligned approximately N10°W dipping 60°E.
From the stochastic analysis of the joint data it was possible to identify three main fracture orientation clusters. The orientation of two of these clusters agrees roughly with the orientation of the main features. Cluster B has roughly the same orientation as GH and GI, while features GA, GB, and GC have an orientation similar to the more loosely defined cluster C. The orientation of the third cluster (A) is northwest with a dip to northeast.
It is found that 94 % of all measured hydraulic transmissivity is accounted for by 4 % of the tested rock, not all of this "concentrated" transmissivity is within the major features defined by geophysics. When the hydraulic connections across the site are, examined they show that there are several well-defined zones which permit rapid transmission of hydraulic signals. These are essentially from the northeast to the southwest.