Proposal of Surveying System to Investigate Hydrogeological Structure of Fracture Developing Rock Mass and its Application

Ground water flow in fracture developing rock mass seems to be more complicate than porous sedimentary rocks due to the geometry of fractures and characteristics of fracture filling minerals. To understand the ground water flow in the fracture developimg rock mass, the ground water surveying system was proposed. The system was established by three points of view, i.e. Where the ground water flows?(geological structures), How the rock permeability is?(rock mass permeability), How the ground water flows?(ground water flow property). The system was constituted by the newly developed methods and the existing ones. The system was applied to the granitic rock site, 100 m×100 m wide and 100 m deep to verify the system.Major conclusion obtained at the application site was as follows;Core-logging, BHTV logging, and geo-tomography were rather instrumental in making a geological model. Single-hole and cross-hole hydraulic test could obtain 2-D distribution of the hydraulic conductivity, showing the close relationship with the geological structures and geophysical parameters. Radon logging and spiner logging is useful to detect the permeable fractures.