A large scale flow and tracer experiment in granite

This paper describes the Stripa 3D experiment where water and tracer flow have been monitored in a specially excavated drift in the Stripa mine. New experimental techniques and equipment were developed and used. The experiment was performed in a 100 m long, for this purpose, excavated drift at the 360 m level in granite. The whole ceiling and upper part of the walls were covered with 375 individual plastic sheets where the water flow into the drift could be collected. 11 different tracers were injected from 9 different points at distances between 11 and 55 m from the ceiling of the drift. The flowrate and tracer monitoring was kept up for more than two years. The tracer breakthrough curves and flowrate distributions were used to study the flow paths, velocities, hydraulic conductivities, dispersivities and channeling effects in the rock. The tracer movement as measured by the more than 160 individual tracer curves has been analyzed with the traditional advection-dispersion model, but also with more recent models which include the effects of channeling and the diffusion of tracers into stagnant waters in the rock matrix and into stagnant waters in the fractures themselves. The tracer experiments have also permitted the flow porosity and dispersion to be calculated