## 1 Introduction  
Deformation and fracturing in the rock engineering may result in serious hazards, which may pose a great threat to the safety of engineering and even the lives of people. Therefore, it is necessary and important to strengthen the study of the mechanical behaviors and mechanisms of rock [1; 2; 3; 4; 5; 6; 7] as well as the early warning of rock failure [8; 9]. The deformation and failure process of rocks is always associated with energy changes; consequently, temperature variations can be observed during the process. This provides us with a method to study the characteristics and mechanism of rock deformation and fracturing by monitoring the temperature variation [10]. These studies can be useful for a better understanding of the mechanisms of deformation and failure in rock engineering, such as rockbursts in tunnels and landslides of rocks. They may also be helpful for supplying some temperature precursor information for guiding prediction on the failure of rock [11; 12; 13]. Actually, the relation between rock failure and temperature variation has been applied to much research on seismic temperature anomalies. Through the study of earthquakes, it is found that rocks within a certain range of the earthquake areas are often accompanied by temperature anomalies during the seismogenic process and after the earthquake [14; 15]. In order to explore the temperature anomalies of rocks, many experts and scholars have done a lot of research and analysis on the temperature anomalies by using different technologies. In the early stage, through the visual interpretation of the infrared radiation image monitored by the satellite [16], it was found that there were obvious infrared radiation anomalies near the earthquake area from days to months before the earthquake [17], and the anomaly area was mainly distributed along the fault near the epicenter [18]. Later, in order to analyze the variation characteristics of infrared radiation anomalies, the wavelet transform method [19], the background field removal method [20], the multi-channel method [21], and the power spectrum method [22] were proposed to further quantitatively analyze the image, which improved the ability of using infrared radiation images to analyze infrared radiation anomalies before and after earthquake events. In addition to the use of satellite data, the temperature observation of bedrock at different depths was also observed by means of borehole temperature measurement [23; 24; 25]. It is recognized that there are not only heating but also cooling areas before the earthquake, and the precursor information has the characteristics of near field, structural correlation, and sensitivity to stress changes. The researchers used different technical means and data processing methods to study the temperature anomalies before and after the earthquake. During the earthquake preparation process, they realized that there were temperature anomalies in the rocks in the earthquake area and summarized the spatial and temporal characteristics of the temperature anomalies. However, because technologies such as satellite monitoring, borehole temperature measurement, and so on are usually affected to varying degrees by factors such as complex terrain, changeable climate, vegetation cover, stress disturbance, and so on, the accuracy of temperature data is also affected. In addition, because of the different geological structures, in-situ stresses, and formation lithology in various regions, it is difficult to systematically study the characteristics and mechanism of temperature changes. Consequently, the relation between temperature variation and the deformation and fracturing of rock during the earthquake process is still not clearly known, especially the mechanism, which still needs to be investigated.