Study on characteristics of fractures with groundwater inflow in deep underground environment, their long term stability and investigation method

Ishibashi, Masayuki

Fractures in crystalline rock, such as granite, function as pathways for groundwater flow and mass transport. Understanding characteristics and long term behavior of fracture with groundwater inflow is important for evaluation of transfer the dissolved matter in groundwater. Therefor this paper describes the features of WCFs (water conducting fractures), the long-term behavior and the investigations. Result of detailed gallery wall mapping and borehole investigations at the ground level -300 m and -500m galleries in the Mizunami Underground Research Laboratory clarify that WCFs are is characterized by its occupy approximate 10 percent of all observed fractures, the size is relatively large and the fillings have layer structure including calcite.