The Stability Of Rock Acoustic Emission Monitoring Studies

In this paper, both compressive and Brazilian tests were performed with rock samples from Dahongshan copper mine, and investigation was conducted on the characteristics of acoustic emission (AE) during the loading process. In situ AE monitoring was also performed at some panels of the mine to explore both the failure mechanism of rock mass and the way of failure prediction.The results showed from the uniaxial compressive and Brazilian tests that AE activities occur at the beginning of loading in most samples. As the load increases, the rate of AE events of the rock samples declined. Later AE activities appear frequently when the loading stress reaches 80% to 90% of the failure stress. At the moment of failure, the AE parameters reach maximum values.AE activities from in situ monitoring data were relatively quiet at the first four months at panel 5011, level 660, while AE activities turned abrupt starts from 6th March and continued until beginning of April. Meanwhile, roof falling happened at the end of March at west part of the panel. It could be concluded from both the in situ monitoring data and the observation results that the rock mass stability is closely related with the AE activities. The stope roof without obvious changes of AE rate and energy rate is relatively stable. The increase of AE energy rate which reaches decade times even hundreds times sudently to that in before and holds a long time is less stable.The spectrum analysis of AE signals obtained from in situ monitoring results was also investigated. With the conducting of the in situ monitoring, there is a rule that the main frequency of the AE signals increases at first, then decreases, increases again and decreases eventually. The second decrease of the main frequency shows that rock mass was damaged possibly and plenty of overflowing signals were received during failing of rock mass.AE monitoring is a feasible way to predict failure of rock mass. The changes of AE activity from quiet state to long-term abrupt one, appearance of overflowing signals over a long period of time, and the second reduction of the main frequency of AE signals could be regarded as the forewarning for the failure of rock mass.