基于FEM研究含孔隙介质中裂纹矩张量反演精度

基于矩张量理论的动态裂纹扩展监测方法，利用裂纹开裂产生的声发射信号获取裂纹开裂信息，而介质中的孔隙结构会影响监测结果的准确性。使用二维平面应变有限单元方法（FEM）建立孔隙分布数值模型，给出特定裂纹在不同孔隙率介质下的反演结果，并分析其成因。数值结果表明，双力偶成分对孔隙率的敏感度最高。对于纯剪切裂纹，反演结果中双力偶成分的占比随孔隙率的增大而减小；对于面内各向同性和拉伸裂纹，双力偶成分的占比随孔隙率的增大而增大。原因是孔隙结构对弹性波的散射导致弹性波幅值的空间分布发生变化，效果体现在两方面:一方面，能量转移作用导致不同传播方向弹性波的幅值趋于接近；另一方面，孔隙分布的差异导致临近传播方向的弹性波幅值差异增大。两种影响因素的权重差异导致不同裂纹的反演结果受孔隙的影响不同。 

Precision of crack moment-tensor inversion in porous media using finite element method

The monitoring method for the dynamic growth of cracks, which is based on the moment-tensor theory, utilizes the acoustic-emission signal of crack opening to obtain the information of cracks. The pore in media has an effect on the accuracy of monitoring results. The two-dimensional plane strain finite element method (FEM) was applied to build the numerical model with pore involved. The inversion results for specific cracks in media with different poriness were provided and the mechanism was analyzed. The numerical results show that the double-couple component is more sensitive to poriness than the other two components. For pure shear cracks, the proportion of double-couple component decreases with the increase of the poriness. For isotropic and pure tensile cracks, the proportion of double-couple component increases with the increase of the poriness. The reason is the wave scattering of pore changes the spatial distribution of elastic-wave amplitude and the effect contains the two aspects. The energy transfer results in the fact that the wave amplitudes of different directions become closer to each other. Meanwhile, the difference of pore distribution increases the difference between the wave amplitudes of different directions. The effect of pore on inversion results varies for different cracks, because the weight of the two aspects is different.