岩体破裂震源机制解类型判据的改进及应用研究

Improvement and application of focal mechanism solution type criterion for rock mass fracture

为开展工程岩体微震震源机制解的研究,以矩张量理论为基础进行分析。针对Ohtsu分解方法与岩体破裂类型判据仅适用于受拉情况的局限性,引入岩体受压状态下的矩张量分解模型,通过讨论补偿线性矢量偶极(compensated linear vector dipole,简称CLVD)分量的正负,扩展其分量计算表达式,并加入各向同性(isotropic,简称ISO)分量来修正岩体破裂类型判据;同时利用CLVD-ISO钻石震源类型图来形象说明各种岩体破裂类型的分量所呈现的特征;针对利用纯双力偶(double-couple,简称DC)分量MDC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。在此基础上,结合香炉山钨矿一起典型的工程案例开展震源机制的反演分析、震源的力学机制分析以及震源破裂面的空间分布特征分析,利用修正后的判据得到此次案例中岩体破裂类型主要是张拉破裂与压缩破裂,进一步采用张拉型震源模型得到了各个震源破裂面的空间分布参数。分析结果与实际情况基本一致,这也表明采用改进方法可以很好地应用于基于矩张量理论的工程微震震源机制解的分析。

In order to carry out the research on the focal mechanism solution of rock mass microseisms,the analysis is based on the moment tensor theory.In view of the limitations that the Ohtsu’s decomposition method and the rock mass fracture type criterion are only suitable for the rock mass under tension conditions,the moment tensor decomposition model of the rock mass under compression is adopted.By discussing the positive and negative of the compensated linear vector dipole(CLVD)component,the component calculation expression is improved and the isotropic(ISO)component is introduced to modify the rock fracture type criterion;meanwhile,the CLVD-ISO diamond source type map is adopted to illustrate the characteristics of various rock mass fracture types.Besides,the tension source model is adopted for characterizing the fracture surface occurrence with the deficiencies of the double-couple(DC)component(MDC)taken into considered.On this basis,the analyses of focal,including the source mechanism,the mechanical mechanism and the spatial distribution characteristics of the source fracture surface are carried out combined with a typical engineering case of Xianglushan Tungsten Mine.Based on the modified criterion,the results indicate that the main types of rock mass fracture in this case are tension fracture and compression fracture.Furthermore,the special distribution of source fracture surface parameters are obtained with the tension source model adopted.The analysis results are basically consistent with that in actual situations,which also verify the application of the improved model in the focal mechanism solution analysis of engineering microseisms based on the moment tensor theory.