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Prediction of Subsurface Crack Propagation by the Acoustic Emission Moment Tensor Analysis

通过声发射矩张量分析预测地下裂纹扩展

基本信息

批准号：
03805040
负责人：
OHTSU Masayasu
金额：
$ 0.96万
依托单位：
Kumamoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

An application of a moment tensor analysis to acoustic emission (AE) is studied to develop a prediction technique of crack propagation. A moment tensor inversion based on P wave amplitude is employed to determine six independent tensor components. A computer code named SiGMA (simplified Green's functions for the moment tensor analysis) is developed for the AE inversion analysis. To classify crack type and to determine crack orientation from moment tensor components, a unified decomposition of eigenvalues is proposed. The aim of the decomposition is to determine the proportion of shear and tensile contribution on AE sources, and to classify cracks into a crack type of the dominant motion. The SiGMA inversion and the unified decomposition are applied to AE waveforms detected during an in-situ hydrofracturing test. AE waveforms detected by eight accelerometers deployed during the hydrofracturing test are analyzed. Crack types and orientations determined are in reasonable agreement with a predicted failure plane from bore-hole TV observation. The results suggest that tensile cracks are generated first at weak seams, and then shear cracks follow on the opened joints.The SiGMA procedure is modified to solve the 2-D problem and is applied to experiments of a 2-D model with an internal slit. Mixed-mode crack propagation from the slit under uniaxial-compression is investigated and AE waveforms are recorded by a four-channel AE system. Crack locations, crack types, and crack orientations are determined from AE waveforms, based on the moment tensor analysis. The results are compared with crack trajectory observed in the model. The results confirm that the SiGMA analysis is applicable to predicting failure process of subsurface materials.

研究了矩张量分析在声发射（AE）中的应用，以发展裂纹扩展的预测技术。基于P波振幅的矩张量反演被用来确定六个独立的张量分量。为进行声发射反演分析，开发了一个计算机程序SiGMA（Simplified绿色函数用于矩张量分析）。为了从矩张量分量中识别裂纹类型和确定裂纹方向，提出了一种统一的特征值分解方法。分解的目的是确定AE源上剪切和拉伸贡献的比例，并将裂纹分类为占主导地位的运动的裂纹类型。将SiGMA反演和统一分解应用于现场水压致裂试验中的声发射波形。分析了水压致裂试验过程中8个加速度计的声发射波形。确定的裂纹类型和方向与钻孔电视观测的预测破坏面合理一致。结果表明，裂纹首先在弱缝处产生拉伸裂纹，然后在张开缝处产生剪切裂纹。将SiGMA方法改进为求解二维问题，并应用于含内缝二维模型的试验。研究了单轴压缩条件下裂纹的扩展，并利用四通道声发射系统记录了声发射波形。裂纹位置，裂纹类型和裂纹方向确定从AE波形，基于矩张量分析。将计算结果与模型中观察到的裂纹轨迹进行了比较。结果表明，SiGMA分析方法适用于亚表层材料的破坏过程预测。