Acoustic emission measurements as a contribution for the evaluation of stability in salt rock

The mechanical stability of underground cavities can only be assessed if a variety of geotechnical investigations can be carried out. Especially in salt mining such investigations should include the observation of acoustic emission (AE), as the deformation of salt rock is associated with AE activity even in case of stresses far below the strength of the rock. So regions of high geomechanical loading can be inferred in which the dilatancy boundary in the stress space has been crossed and a possible increase of the load can be monitored. In this paper results will be presented obtained by operation of a 2-channel equipment performing counting of AE and by operation of a 24-channel equipment capable of locating AE in the salt rock. The analysis of signal amplitudes and magnitudes of AE and the characterization of temporal and spatial variations to be observed in the data will be emphasized. Further available results of geotechnical investigations at the operational sites will be discussed in comparison to the results of AE measurements.