Abstract Acoustic emission(AE) is an important means to study rock internal micro-deformation and failure mechanism,the Kaiser effect is one of the common used methods of geostress measurement which is not standardized now. In many cases the Kaiser effect points are not obvious. In order to improve the ability of identifying Kaiser effect point,uniaxial compressive AE experiments of 21 rock samples are carried out. The samples derived from Ordos basin and consist of conglomerate,sandstone and mudstone. Comparison of the influence of lithology,loading mode and AE parameters on Kaiser effect point recognition are made. The results show that conglomerate is better than sandstone and mudstone;cyclic loading is better than step cyclic loading and monotonic loading;accumulated energy is better than AE and counts for identifying Kaiser effect point. The analysis of counts,power and frequency of AE events and the deformation and cracking micromechanism of rock samples under different load levels and cycles,suggesting that there are two types of AE events:one is frictional AE caused by the closure of original cracks and friction between the particles of rock;the other is cracking AE produced by the new failure extension or dislocation. Suppressing frictional AE and highlighting cracking AE can make Kaiser effect point more clear. It is recommended that the cyclic loading should be used to eliminate the frictional AE,and accumulated energy should be used to indentify Kaiser effect point,and the pre-loading stress level should exceed the estimated geostress.
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Received: 09 October 2010
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