Self-healing of excavation-disturbed rocks in the near field of underground cavities - exemplary measurements in rock salt and interpretation of preliminary results

Excavation disturbed zones develop in all kinds of rock as a consequence of the opening of cavities. Such zones are characterized by a change in hydraulic behaviour which can form a problem with regard to the sealing of waste disposal areas. Rocks showing a plastic behaviour, like rock salt, have the potential of healing when the stress state which was disturbed by excavation returns to an advantageous state. If healing can reliably be predicted, the excavation disturbed zone may not form a long-term safety issue in rock salt. Investigations of permeability and stress state around lined and open excavations have been performed in order to relate hydraulic behaviour to stress state. First results which are presented here are promising. (authors)