Current status of technology for hydrogeological investigation; Part:2 Giophysical logging

Takeda, Seietsu; Ogata, Nobuhisa ; Osawa, Hideaki  

In order to establish a hydrogeological model for a rock mass, data are required on its hydrogeological properties. A development for geophysical logging technique which is considered to be available for obtaining data on physical properties of rock mass is being carried out, aiming at examination of its applicability to a hydrogeological evaluation of the rock mass with an assumption of correspondances between the hydrogeological and the physical properties of the rock mass. In the development of the technique, a borehole was drilled in a granitic rock, followed by measurements of physical parameters by geophysical loggings and laboratory tests on the drill cores. A consideration was made on the relationship between the physical properties and the features of fractures and alterations in the rock mass deeper than 500m.The results are as follows : (1)A close correlation is recognized between the features of fracture and alterations and the peophysical properties such as apparent resistivity, P velocity, density and porosity. (2)The rock mass (from 500m to 1010m deep) can be divided into five zones by geophysical logging data.