Long distance tracer tests in a highly permeable fault zone at the Lindau fractured rock test site

Authors:

• Thomas Himmelsbach,
• Heinz Hoetzl,
• Piotr Małoszewski

Abstract

The Lindau Test Site is located at a planned dam site in the Black Forest, Germany. The major hydrological unit is formed by a hydrothermally mineralized, highly permeable fault zone. In the course of underground exploration numerous boreholes were drilled into the fault zone and an additional tunnel system was excavated parallel to the ore body. This offered ideal conditions for tracer experiments to be performed over varying distances. The experiments were conducted under hydraulic boundary conditions similar to those of natural flow field conditions. The breakthrough curves were analysed with a convective-dispersive fracture flow model incorporating matrix diffusion into the rock matrix. The inverse fitting of the experimental data to the analytical model yielded hydraulic parameters such as the matrix porosities and the average fissure aperture. The main emphasis is laid upon the increase of dispersivity with scale and the role of diffusion processes for migration processes in fractured rock.