CATEGORIZATION OF DISCONTINUITIES FOR CONCEPTUAL DESCRIPTION OF ROCK HOSTING REPOSITORIES FOR HAZARDOUS-WASTE

The weaknesses in a rock mass are discontinuities that determine its h ydraulic and strength properties and have a major influence on the dec ision as to whether a proposed site for a repository for highly radioa ctive waste can be accepted or not and on the selection of a suitable repository design. Classification of discontinuities is needed both fo r general conceptual description of the constitution of a rock mass an d for having a basis for defining relevant rock structure models for n umerical calculations. The ultimate goal of the work described is to o utline a classification scheme for the various types of discontinuitie s. The present paper gives a basis for this by proposing a general cat egorization scheme of discontinuities ranging from large fracture zone s (first- and second-order), to minor fracture zones (third-order) and discrete fractures of various persistence. water-bearing capacity and strength (fourth to seventh order). The geometry and general performa nce of the respective category are defined, while specific physical pr operties cannot be ascribed to them because of the variation in origin and nature. (C) 1998 Elsevier Science B.V. All rights reserved.