Technical Report NTB 88-37
Grimsel Test SiteEngineering geological investigations for the interpretation of rock stress measurements and fracture flow tests
This report describes the basic geological work carried out within the BGR projects "Rock Stress Measurements" (GS – Gebirgsspannungen) and "Fracture System Flow Test" (BK – Bohrlochkranzversuch) at the Grimsel Rock Laboratory/Switzerland. A short introduction into the geology of the Grimsel area is followed by the description of the engineering geological investigations and the evaluation methods applied. The structural geological data resulting formed the basis of the subsequent overall engineering geological evaluation and the tectonic analysis. The relationships between the stress field and the joint system (GS area) on the one hand and the results of the flow tests (BK area) on the other are particularly important.
Evaluation of the geological data shows structural tectonic and hence rock mechanical and rock hydraulic differences between closely neighbouring rock sections. For this reason this report includes descriptions of the joint system within the area investigated as well as the rock mechanical and rock hydraulic aspects.
The engineering geological analysis of both test areas then enables a prognosis to be made of rock stresses and rock hydraulic properties in the full rock area investigated by the BGR. In this manner transferability to other areas is justified.
