This paper experimentally evaluates and quantitatively compares stress-induced damage progression and acoustic emission (AE) in granite and sandstone based on continuous acousto-optic-mechanical (AOM) observations. Experimental results reveal that the step-rise characteristics of the AE event rate preceding the entire macrofracturing process and the apparent white patching phenomena are the most significant acousto-optical evidences for process zone nucleation in granite but not in sandstone. During the unstable crack growth stage in granite, the robustly high AE event rate level has been mechanically correlated with the reactivation and intensification of fracture process zones (FPZs) by the stress build-up, and the relatively low AE event rate level has been revealed as a result of the progression of FPZs into macrocracks. It is the first time that the process zone nucleation in granite has been mechanistically related to the clustering of three types of grain-scale microcracks, i.e., grain boundary cracks, intragranular cracks and transgranular cracks, due to the grain interlocking effect. Comparatively, the clustering of microcracks is insignificant in the brittle failure of sandstone. Mechanistic correlations among the AOM characteristics in the two rock types are also investigated in detail.

本文基于连续的声光力学（AOM）观测，对花岗岩和砂岩中应力引起的损伤进展和声发射（AE）进行了实验评估和定量比较。实验结果表明，在整个宏观压裂过程之前，AE事件发生率的阶跃上升特征和明显的白色斑块现象是花岗岩（而不是砂岩）中过程区成核的最重要的声光证据。在不稳定的裂纹扩展期间在花岗岩阶段，强烈的高AE事件发生率水平与应力积累在机械上相关，与断裂过程带（FPZs）的活化和强化相关，并且由于较低的AE事件发生率水平而被揭示。 FPZ进入宏观裂纹的过程。由于晶格互锁的作用，花岗岩中的加工区成核机制首次与三种类型的晶粒微裂纹的聚集机制相关，即晶粒边界裂纹，晶内裂纹和跨晶裂纹。相比之下，微裂纹的聚集在砂岩的脆性破坏中微不足道。还详细研究了两种岩石类型的AOM特征之间的力学相关性。