Application of the Kaiser effect of acoustic emission to measure vertical stress in an underground mine

To estimate vertical stresses, a number of test specimens were obtained from different levels in an underground mine. The Kaiser effect of acoustic emission (AE) was employed to estimate the vertical orientation stresses on rock cores. However, sometimes the take-off point for the AE event rate was not clear in the loading process. A pivot point method was developed and applied to determine the take-off point for the Kaiser effect of acoustic emission. Usually, vertical stresses at different levels are tested in the laboratory under uniaxial loading conditions. The results obtained for the Kaiser effect of AE method compare well with other in-situ measurement methods, making this technique a viable alternative to conventional techniques.