Evaluation of pillar deformation and stability in a salt mine, utilizing acoustic emission, mine survey and rock deformation data

The stability of a rock salt pillar has been studied utilizing deformation and acoustic emission measurements. The pillar is loaded by the pressure of the overburden and exhibits steady state creep. The creep rate of the pillar is in a range of 3.10-6 [d-1] in both directions, in longitudinal compression and transverse extension. Besides measurements of deformation, the acoustic emission of the pillar is monitored by using a one channel system. Analysis has been made of the signal event rate and the frequency distributionof the signal amplitudes. The event rate was found to vary over the period of a year whereas the amplitude distribution remained constant. The results of acoustic emission and deformation measurements are in agreement and lead to the conclusion that the pillar is presently stable. Both types of measurements can be understood as providing complementary information