Fracture permeability of clays: A review

Information about the impact of faults and fractures on permeability of argillaceous formations has been collected by reviewing data provided by people involved in the excavation of deep tunnels. It appears that the fracture response and the secondary permeability of clay masses are characterized by a wide variability, due to the many factors at play. The Italian blue clays of plio-pleistocenic age can be intersected by water-bearing fractures. Other argillaceous formations present in Italy should also be considered for the disposal of radioactive waste. In particular, the widespread formation known as 'argille scagliose', despite the often chaotic structure and the presence of exotic materials, is homogeneous, from the viewpoint of hydraulic conductivity, and is rather promising as host rock of a radioactive waste repository. Work has been performed under contract with ENEA in the framework of the European Atomic Energy Communities cost-sharing research programme on 'Radioactive Waste Management and Disposal'. (Auth.)