3D Crack Distribution Model of Rock Mass using AE induced by Coal Mining

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In this study, laboratory experiments for rock and coal samples produced at Dartbrook Coal Mine, Australia, and analysis of AE observed during mining at the line were conducted in order to construct the 3D fractal model of crack distribution in the rocks around coal mine panel. The reliability of the model was also confirmed comparing with the events occurred during mining.For 17 pieces of rock samples of coal, sandstone, silt stone, uni-and tri-axial compression tests were carried out. The experimental results are :1)It was found that the number of AE event was decrease with increase of the confining pressure.2)AE activity during loading was dependent on the kind of rock.3)It was found that the AE wave forms detected during tests were estimated the differential of acceleration waveform.4)3D fractal models of crack distribution in the specimens were constructed by the moment tensor analysis.5)Visualization for the model was realized by VRML.6)The crack distribution models showed that shear type cracks were dominant for coal and sandstone specimens.For two hundred thousand AE waveforms recorded in the mine from August to October in 1999, AE source location and moment tensor were analyzed The analytical results are :1)It was found that the each axis of tri-axial AE sensor composed 20 tri-axial velocity meters was not determined from blasting test wave forms.2)Therefore, by the conventional AE source location analysis most of AE sources were determined, and the 3D crack distribution model of rock mass was constructed by the moment tensor analysis.3)The AE activity and 3D crack distribution model reflected the mining activity and some events such as small scale rock fall occurred at the working face, and the effectiveness of the model was found.