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

本研究通过对澳大利亚达特布鲁克煤矿的岩石和煤样进行室内实验，并对采线处的声发射观测结果进行分析，建立了煤矿底板周围岩石裂缝分布的三维分形模型。并与采矿过程中发生的事件进行了比较，验证了模型的可靠性。对煤、砂岩、粉砂岩等17块岩石试样进行了单轴和三轴压缩试验。实验结果表明：1)声发射事件数随着围压的增大而减小；2)加载过程中的声发射活动与岩石种类有关。3)试验中检测到的声发射波形可以用加速度波形的差值来估计。4)通过矩张量分析，建立了试件裂纹分布的三维分形模型。5)利用vrml实现了模型的可视化。6)裂缝分布模型表明，煤和砂岩试样以剪切型裂缝为主。对该矿1999年8 - 10月记录的20万声发射波形进行了声发射源定位和力矩张量分析，分析结果表明：1)由20台三轴测速仪组成的三轴声发射传感器各轴并非由爆破试验波形确定的；2)因此，通过常规的声发射源定位分析确定了大部分声发射源，并通过矩张量分析构建了岩体三维裂缝分布模型。3)声发射活动和三维裂缝分布模型反映了采矿活动和工作面发生的小尺度岩崩等事件，验证了模型的有效性。

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.