Estimation of the highest potential transmissivity of discrete shear fractures using the ductility index

Ishii, Eiichi   

The highest transmissivity of fractures in a rock mass is crucial for conservative assessment of a site for radioactive waste disposal. However, it is not realistic to measure that of all possible fractures in a site. Previous studies indicated that the highest potential transmissivities of fractures in fault zones can be predicted by a rock mechanical indicator, ductility index (DI). Noting that the mechanism of formation and preservation of pore structures in fault-zone fractures may be the same as that of pore structures in discrete shear fractures. This study investigated whether or not the DI model is applicable to discrete shear fracture systems, using geological and hydrological data of discrete shear fractures in a Neogene diatomaceous mudstone (Koetoi Formation). As a result, the data set obtained by this study well fits the existing data sets of the DI model, suggesting that the DI mode is applicable to discrete shear fracture systems as well as fault zones.