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利用自主研发的煤岩双面剪切细观开裂演化过程试验装置,通过开展不同法向应力条件下的剪切试验,借助声发射技术及图像处理技术,对细观开裂扩展过程、细观开裂扩展空间分布进行深入探究。研究结果表明:对于压剪应力条件下的双面剪切试验,加载过程中的大部分阶段,试件表面损伤不明显,表面裂纹出现在峰值剪应力之前;当剪应力达到峰值前,Hit率有一个急剧增加的过程,说明砂岩内部已有裂纹产生,而试件表面并无明显变化,一段时间后才在表面观测到细小裂纹,推测裂纹由内向外扩展;试件发生宏观破坏后,左右两侧裂纹呈八字形或梯形分布,由于竖向剪切力引起的岩体内部剪切破坏占主导作用且砂岩内部晶粒间存在一定的几何物理性质差异,主裂纹基本沿预定剪切面扩展的同时表现出开裂扩展的不规则性;裂纹多在石英、长石等矿物颗粒的边缘即砂岩中相对薄弱的环节产生,随着应力水平的增加,裂纹也会穿过矿物颗粒形成穿晶破裂,这种现象多在石英颗粒中出现,这与其特有的微结构特征有关。
Using self-developed test device for the double-sided shear evolution of coal and metamorphic rocks, by means of shear tests under different normal stress conditions, with the help of acoustic emission and image processing techniques, the mesoscopic crack propagation process, meso-cracking Expand the spatial distribution for further exploration. The results show that for the two-sided shear tests under compressive-shear stress, the surface damage is not obvious during most of the loading process, and the surface cracks appear before the peak shear stress. Before the peak shear stress, the Hit rate There is a sharp increase in the process, indicating that sand cracks have occurred within the existing, and the specimen surface did not change significantly after a period of time before the surface cracks were observed on the surface, it is speculated that the crack from the inside to the outside; Due to the vertical shearing force, the internal shear failure of the rock mass dominates and there are some geometric and physical differences among the grains in the sandstone. The main crack propagates along the predetermined shear plane While the crack growth shows irregularities. Cracks mostly occur at the edges of mineral grains such as quartz and feldspar, which are relatively weak in the sandstone. As the stress level increases, the cracks also cross the mineral grains to form a transgranular fracture , This phenomenon mostly occurs in quartz grains, which is related to its unique microstructure characteristics.