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生产的岩石和煤样进行实验室实验，并对沿线开采过程中观测到的声发射进行分析，以建立煤矿盘区围岩裂隙分布的三维分形模型。对17块煤岩、砂岩、粉岩岩样进行了单轴和三轴压缩试验，验证了模型的可靠性。实验结果表明：1)随着围压的增加，声发射事件的次数减少；2)加载过程中的声发射活动与岩石的种类有关；3)试验中检测到的声发射波形被估计为加速度波形的差值。4)用矩张量分析建立了试件中裂纹分布的三维分形模型。5)用VRML实现了模型的可视化。6)裂纹分布模型表明，煤和砂岩试件以剪切型裂纹为主。对于1999年8-10月在该矿记录的20万个声发射波形，对声发射源位置和力矩张量进行了分析，分析结果为：1)爆炸试验波形不能确定由20个三轴速度计组成的三轴声发射传感器的每一轴；2)常规声发射源定位分析确定了大部分声发射源，利用力矩张量分析建立了岩体三维裂隙分布模型；3)声发射活动和三维裂隙分布模型反映了采动活动和工作面发生的小范围崩落等事件，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.