###### Abstract
According to [PERSON]'s research [17], crack propagation in rocks can be divided into three stages, namely, crack-free propagation, stable propagation and unstable propagation in the initial stage. [PERSON] et al. [18] prefabricated cracks with different dip angles in granite and carried out uniaxial compression tests on granite with different prefabricated fracture angles. Combined with the numerical simulation method, it was concluded that the crack dip angle has an effect on crack propagation and development. In most cases, the deformation and failure in the rock is caused by the development of deformation localization in the rock system [19; 20]. Analyzing the deformation and failure processes of rock through the development of deformation localization has become one of the most important methods to study rock mechanics. At present, scholars at home and abroad mostly use optical systems to observe the development of rock deformation localization and the rock failure process. Currently, the main optical systems used to measure stress-strain and displacement are three-dimensional laser Doppler vibration measurement (3D LDV) and Digital Image Correlation technology (DIC). Of these, the 3D laser vibration measurement system is the most advanced sensor; it has the advantage of a wide range of application scenarios and low requirements for the use environment, but because of its high cost, it is especially applied to the inspection of products of the automobile industry and aerospace industry, as well as light and ultra-light structures [21; 22]. Digital Image Correlation technology (DIC) [23] is a non-contact full-field non-destructive optical measurement method, which combines a vision system and Digital Image Correlation technology (DIC) to realize displacement and strain measurement in a three-dimensional space. Through calculation, parameters such as displacement and strain of the calculated point on the surface of the specimen can be obtained. In the process of measurement, there is no need to install any sensor equipment, thus avoiding the human error of the traditional method [24; 25; 26]. Because of its performance to price ratio and wide range of application promotion, it is used by some researchers as a research approach. So far, DIC has been successfully suitable for the analysis of deformation behavior of rocks due to its robustness and utility in characterizing and detecting different types of fractures and failures in rocks. At present, some scholars have used this technology to study the deformation characteristics of rocks. [PERSON] et al. [27] carried out compression tests on three-dimensional printed Brazilian disk specimens with single and double defects under quasi-static load by using Digital Image Correlation technology (DIC). They studied the bearing capacity, crack initiation, propagation and bonding mechanism of prefabricated cracked rock specimens, and systematically studied the aggregation behavior of double defect specimens. [PERSON] et al. [28] carried out uniaxial compression tests of rock-like materials with prefabricated single cracks by using the Digital Image Correlation method, and studied their deformation and failure characteristics from three aspects: meso-quantitative analysis, crack propagation law and deformation damage evolution. [PERSON] et al. [29] measured the basic particle size parameters by digital image processing, established the particle shape parameters and analyzed the variation of shape parameters with particle size, distribution characteristics and sensitivity of shape parameters, by means of mathematical statistics and fractal theory. To summarize, predecessors have studied the rock loading rate, rock particle size and crack angle, but generally, only one factor of rock mechanical properties has been studied.