Investigations of excavation effects at the Asse salt mine.

The Asse mine, initially a potash mine later converted into a rock salt mine, was operated between the years 1906 and 1964. After production terminated the mine was selected as an underground laboratory for the disposal of low- and intermediate-level radioactive waste. Since most of the old mine workings in the halite formations had not been backfilled, extensive rock mechanical investigations were carried out right from the beginning of the waste disposal operations. The results have shown large rock stress alternations and rock mass deformations which have taken place due to the creeping behaviour of rock salt. FE-calculations confirmed distinct spatial as well as temporal changes of the natural stressfield. Greatest deformations correlate with the central area of the mine excavations. -Author