Abstract:

Granite is the major pre-selected rock type for HLW (High Level radioactive Waste) disposal project in China. Joints existed in it are usually the key factors to effect mechanical and hydraulic characteristics of fractured rock-msss; and it will be the major channel for nuclide to escape from the disposal reservoir to the biosphere when these joints connect to a conductive net. So it is an important work to deep understand these joint’s behaviours. When study these joints, their surface configuration characteristics are the most important aspects necessary to be researched, because most behaviors of joints are determined by these surface characteristics. Lots of in-situ studies of joints surface configuration characteristics are carried out in Gansu Beishan area, where is the pre-selected district to dispose HLW in China. Firstly, some in-situ joints surface profile curves with different length at different directions are obtained. Then, Barton’ straight edge method and a kind of statistics method are used to analyse these curves. Through these studies, scale effect is obviously founded and its threshold value is 70 cm, another characteristics such as anisotropy and the distribution rule of statistics parameters are also obtained. These studies are the basic works to carry out further researches on the mechanical and hydraulic characteristics of granite in this area.

Key words: joints, joint roughness coefficient, surface characteristics, scale effect, anisotropy