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实验研究三维断层的形成和扩展对于理解实际断层作用过程具有重要意义.在双轴压缩条件下开展了断层三维扩展过程的实验研究,利用多通道数字化高密度应变观测和基于可见光图像分析的数字散斑相关测量技术对岩石样品应变场的详细结构进行了动态观测和分析,同时利用多通道声发射全波形三维定位系统对样品内部微破裂的发育过程进行了观测.实验结果表明,断层在三维空间的扩展模式与二维明显不同,表现出更复杂的空间展布形态和变形机制.断层的三维扩展过程可以划分为3个基本阶段:第一裂纹扩展阶段—翼裂纹扩展阶段、转换阶段—花瓣裂纹活动阶段和第二裂纹扩展阶段—贝壳断面形成阶段.不同阶段具有不同的主导裂纹扩展方式,并对应不同的变形场和微破裂分布.其中,花瓣裂纹活动阶段在三维断层的发育过程中至关紧要,它是从表面似二维扩展向三维扩展转换的关键,也是三维断层扩展区别于二维断层的核心所在.
The experimental study on the formation and extension of 3D faults is of great significance for understanding the actual fault process.Experimental studies on the three-dimensional (3D) propagation of faults are carried out under biaxial compression. Using digital multi-channel high-density strain observations and digital image dispersions Speckle correlation measurement technique was used to observe and analyze the detailed structure of the strain field in rock samples. At the same time, the multi-channel acoustic emission full-wave three-dimensional positioning system was used to observe the development of microcracks in the samples.The experimental results show that the fractures in the three-dimensional space Is obviously different from that of 2D and shows a more complex spatial distribution and deformation mechanism.The three-dimensional extension of faults can be divided into three basic stages: the first crack propagation stage, the wing crack propagation stage, the transition stage, the petal The stage of crack activity and the stage of second crack growth-shell section formation, with different dominant crack propagation modes in different stages and corresponding to different deformation fields and micro-fracture distributions, in which the active stage of petal crack during the development of three-dimensional fault Importantly, it looks like a two-dimensional expansion from the surface The key transition to three-dimensional expansion, but also three-dimensional expansion of the core is different from the two-dimensional tomographic fault.