This paper describes the results from a number of laboratory testing experiments conducted under uniaxial and triaxial conditions. A high speed AE monitoring system was used to record the maximum amplitude and waveform for the AE signals with no major loss of events, even for AE event rates of the order of several thousands of events per second, such as they are normally observed before a catastrophic full scale rock mass failure event. The detailed damaging process as stress was increased was determined by monitoring the complete spacio-temporal distribution of microcracking events. The results showed that for samples of similar orientation and collected immediately adjacent to each other, the magnitude of the stress field determined using a triaxial testing set-up is similar to the stress level determined using uniaxial samples.
The determination of the in-situ stress field during the early stages of a project (such as mine feasibility studies), even in areas where development access is not yet available (such as below current open pits) is a key step in a rock mass characterization process. Consequently, over the last decade or so, a number of experimental investigations of compressive loading of intact rock specimens have been undertaken to monitor the general increase of AE activity under conditions of constant rate loading. The study of micro structure mobilization with a subsequent characterization of the in-situ stress measurements has been a key objective of the experimental studies to date (Villaescusa et al., 2002; 2003). This paper presents the results for a number of intact rock samples tested under uniaxial and tri-axial compression. The uniaxial testing was undertaken at the Western Australian School of Mines (WASM) and the triaxial tests were performed in Japan National Institute of Advanced Industrial Science and Technology (AIST).