工程岩体破裂震源机制解及其应力场反演理论研究

Source mechanism solution and geostress field are of fundamental importance in the application of microseismic monitoring for engineering rockmass. They affect the effects of disaster warning of microseismic monitoring.Based on the amount of in-situ typical microseismic monitoring cases of engineering rockmass, the project will deal with the studies on combining solution method of P-wave grid scanning and amplitude ratio, so that to obtain the characteristics of P-axis,B-axis and T-axis of source mechanism solution, the occurrence of source fracturing nodal surface and the formulae of eigen variables of moment tensor. double-couple point source model is used to inverse the partial tensor characteristics of source mechanism solution through moment tensor inversion method, so as to gain the topological relation of moment tensor decomposition offset; and then the research on rockmass fracturing types of tension, shear or mixed one is carried out. In order to determine the occurrence of the source fracturing surface and establish the relation formulae between principal component surface of source clusters and source fracturing surface, principal component vector analysis of spatial coordinates of source clusters and the ellipse ratio analysis of principal component surface are also carried out. Stress axis spatial vector and mean-value method are used to inverse the stress state exerted on the surrounding region of the sources, and then the calculating formulae can be derived out. And finally, the comprehensive analyzing results of source mechanical solutions, source geometrical features and geostress field states for typical microseismic monitoring cases studies are presented at the same time by using the theoretical methods above. The studies of this project will provide the theoretical basis for the practical disaster warning application of microseismic monitoring technology.

工程岩体的震源机制解和作用应力场在微震监测技术应用中极为重要，直接影响微震监测预警效果。本项目在大量的微震监测典型案例的基础上，研究网格扫描法P波初动和振幅比震源机制联合求解方法，获得震源机制解P轴、B轴和T轴特征、震源微破裂节面产状和矩张量特征变量表达式；采用双力偶点源模型,运用矩张量反演法开展震源机制解的偏张量特征研究，求得矩张量分解偏量的拓扑关系，并开展岩体张拉破坏、剪切破坏或混合破坏类型研究；采用PCA主元分析法开展震源簇群空间坐标主元向量研究和主元面椭圆率分析，确定微震源岩体破裂面产状特征，建立微震事件簇群主元面与中尺度岩体破裂面产状的关系式；采用应力轴空间矢量和平均值法反演震源区域作用力场，并推导出应力场计算式。最后，对典型工程岩体的微震监测案例给出震源机制解、震源几何特征和力场状态的综合分析结果。本研究将为微震监测技术在地压灾害预警中的应用提供理论依据。

本项目研究并提出了采用db4小波基组合rigrsure阈值方法可取得最优去噪效果的新方法，并采用该方法分析了大量微震监测信号，为进一步的研究提供了技术保障。在大量地压微震监测典型案例的基础上，研究了P波初动和振幅比震源机制联合求解方法，获得震源机制解特征、震源微破裂节面产状和矩张量特征变量表达式；采用双力偶点源模型,运用矩张量反演法开展震源机制解的偏张量特征研究，求得矩张量分解偏量的拓扑关系，并开展岩体张拉破坏、剪切破坏或混合破坏类型研究；本研究引入岩体受压状态下的矩张量分解模型，通过讨论CLVD分量的正负，扩展其分量计算表达式，并加入ISO分量来修正岩体破裂类型判据，针对MDC分量求解破裂面产状的缺陷，采用张拉型震源模型求解破裂面产状。采用PCA主元分析法开展震源簇群空间坐标主元向量研究和主元面椭圆率分析，确定微震源岩体破裂面产状特征，建立微震事件簇群主元面与中尺度岩体破裂面产状的关系式，并得到破坏面的演化趋势。本研究提出了在求解震源机制解的前提下采用联合迭代反演方法反演应力场方法，推导出应力场计算式, 分析了加入不同程度噪声对应力反演结果的影响，得出随着噪声水平的增大应力轴的误差增大的特点，本研究为应力场分布的确定提供了一个可行方法。最后，对典型工程岩体的微震监测案例给出了震源机制、震源几何特征和力场状态的综合分析结果。本研究将为微震监测技术在地压灾害预警中的应用提供理论依据。