## 1 Introduction
[25] carried out a triaxial compression mechanical experiment of tight sandstone heated from 0 \({}^{\circ}\)C to 1000 \({}^{\circ}\)C and combined the thermal weight loss, XRD, and SEM to analyze the micro-fabrics characteristics at different temperatures. This further revealed the influence of temperature on the mechanical properties of tight sandstone. Furthermore, [PERSON] et al. [26] studied the mechanical properties of siliceous sandstone after varying temperature treatment and concluded that high temperature remarkably affects the rock composition, strength, and failure characteristics. In recent years, the digital image correlation (DIC), as a contactless and high-precision optical measurement technique, has been gradually applied in rock mechanics. The DIC technology has made some achievements in rock mechanics for the past few years. [PERSON] et al. [27] investigated the effect of joint density on the strength characteristics and failure mechanism of rock; DIC technology was applied to calculate the strain field of rocks under compression loading. Results showed that the failure mechanism of the specimens was strongly associated with the joint density. Similarly, [PERSON] et al. [28] used the DIC technology to measure the deformation and strain by performing a static test on sandstone and obtained the strain field on the sandstone surface. Furthermore, [PERSON] [29] used the DIC technology and numerical simulation method to study the nucleation and propagation of a single crack and double cracks of rock-like materials during the uniaxial compression test and obtained the crack development law. For studying the crack extending and damage deformation characteristics of rock subjected to static loading, some scholars have carried out comprehensive detection and analysis by the DIC technology [30; 31]. In the study of rock dynamics, [PERSON] et al. [32] performed a Brazilian disk test of granite by SHPB technique; combined with the DIC technology, they obtained the displacement and strain field of specimen surface. However, [PERSON] et al. [33; 34] used the DIC technology to measure cracks in rock notched semi-circular bending test and analyzed the dynamic rock fracture process. They determined the displacement and strain field with crack propagation. Different from the above analysis, [PERSON] et al. [35] conducted a dynamic test of composite rock under dynamic loading at varying impact velocities by SHPB. They also combined with DIC technology to capture the failure process. The test results revealed its dynamic characteristics and failure characteristics. It can be seen from the above research that most scholars mainly focus on the crack development or damage detection of rock under static or dynamic loading by DIC technology. Unfortunately, few studies can be found on the mechanical properties of rock after high-temperature treatment under impact loading. In coal fire areas, rocks here may be affected by multiple or cyclic dynamic loading. Therefore, it is necessary to discuss the dynamic behavior of rocks in the coal fire areas under cyclic loading. Under cyclic impact loading, the mechanical characteristics of rocks after high temperatures are studied via a 75-milimeter SHPB equipment in this paper, and the DIC method is adopted to analyze the deformation of sandstone specimens treated at different temperatures during the first impact. The deformation field evolution and crack generation process of sandstone under external forces are obtained, which offer a theoretical support for the safety and post-disaster evaluation of rock engineering.