Cataclastic Effects in Rock Salt Laboratory and in Situ Measurements: Fid-Bau Portal

Cataclastic Effects in Rock Salt Laboratory and in Situ Measurements

J. Gramberg / J. P. A. Roest

The aim of the research is the determination of eventual cataclastic effects in environmental rock salt of a heated part of a vertical deep test bore hole, a model for HLW disposal. Known cataclastic systems from hard rock mining and rock salt mines will form the starting point for the explanation of convergence of underground cavity walls. In rock salt, however, different elements seem to prevail: crystal plasticity and micro-cataclasis. The environmental measurements at the deep bore hole have to be carried out from a distance. To this end the acoustic micro-seismic method will be a suitable one. The appropriate equipment for micro-seismic cross hole measurement is designed, constructed and tested in the laboratory as well as underground. Acoustic velocity data form a crucial point. A micro-seismic acoustic P-wave model, adapted to the process of structural changes, is developed. P-wave velocity measurements in rock salt cubes in the laboratory are described. An underground cross hole measurement in the wall of a gallery with semi-circular section is treated and analysed. A conclusion was that, in this case, no macro-cataclasis (systematic large fractures) will be involved in the process of gallery convergence, but that the mechanism proved to be a combination of crystal plasticity and micro-cataclasis. The same mechanism might be expected to be present in the environmental rock salt of the HLW-disposal deep bore hole. As a result this environmental rock salt might be expected to be impermeable. A plan for the application of the developed equipment during the heating test on the ECN-deep-bore-hole is shown. A theory on ''disking'' or ''rim cracks'' is presented in an annex. (Atomindex citation 16:031657)