Transport of dissolved substances in fissured granite

Several research projects have been under way in the Grimsel rock laboratory (Switzerland) since 1983, In the Fracture System Flow Test project, the development of methods and equipment for studying flow rate in fissured rock is being continued. Ten cored boreholes up to 135 m long were drilled for this purpose. The configuration of these holes, serving as injection boreholes and observation holes in specific rock sections, was designed according to the geological structures in the rock around the tunnels of the rock laboratory. Since 1986, tracers have been added to the injected water so that detailed measurements on injected water volumes, pressure heads, and flow rates could be made. Nonlinear flow rates are used for calculating the size of the fissures, the storage capacity, and the permeability tensor under non-steady-state conditions. The calculations were done with a finite-element program. With this program fissures can be modeled using tubular, discoid, or any other spatial element. Variation of the individual parameters provides an indication of the quality of the in situ experiments and the numerical models. The methods and results of the experiments will be described