Non-sorbing tracer migration experiments in fractured rock at the Kamaishi Mine, Northeast Japan

This paper describes the design, implementation, and analysis of in situ tracer migration experiments in fractured granite. The research highlights the importance of geo-hydraulic investigations prior to performing tracer migration experiments. The authors conducted a detailed but simple investigation in order to understand the spatial distribution of conductive fractures and the pressure field. Seven boreholes were drilled in the test area, revealing hydraulic compartmentalization and a heterogeneous distribution of conductive features. After identifying several suitable conductive fractures, three sets of dipole tracer migration experiments were conducted with various combinations of injection and withdrawal hole and dipole ratios. The tracer breakthrough curves were analyzed using a streamline, analytical solution and numerical analysis of mass transport. Best-fit calculations of the experimental breakthrough curves were obtained by assigning apertures within the range of one to ten times the square root of transmissivity and a dispersion coefficient equal to one-tenth of the migration length.