## 3 The Distribution Law of the Thermal Circle in the Surrounding Rock of Deep Roadway
### Testing of Thermal Properties of Granite under Deep Strata Conditions  
The specimens required for thermophysical property testing were prepared from granite samples extracted from a depth of 700 to 1200 m at the Sanshandao Gold Mine. According to the standards recommended by the International Society for Rock Mechanics (ISRM), the rock samples were processed into cylindrical specimens with a diameter of 50 mm and a height of 25 mm. Each group consisted of two specimens, with both specimens in the same group taken from the same depth of the rock core. The deep granite in Sanshandao is predominantly composed of monzogranite, with certain depths containing potassic granite and sericitized granite. The mineral compositions of these deep rock samples are highly similar, with little variation in their proportions, primarily comprising plagioclase, orthoclase, quartz, biotite, and chlorite. The porosity of the rock samples ranges from 1.87% to 2.55%, indicating that they are typical dense granites. Thermophysical property testing was conducted using a Hot Disk thermal constants analyzer (Figure 2). The probe of this instrument comprises upper and lower insulating layers, conductive double-bolt structure windings, and metal foil (nickel wire) windings. During the test, the probe is clamped between two samples, and an electric current is applied through the probe, which simultaneously records the temperature. This setup allows the determination of the relationship between the sample's electrical resistance and time as the temperature changes. The thermophysical property testing of deep granite samples includes thermophysical property testing at room temperature, testing of pressurized water-saturated rock samples, testing under cyclic thermal loads, and testing under stepwise temperature increases. The thermophysical property testing at room temperature involves fixing the probe on the sample holder, adjusting the height and position for subsequent fixation of the rock sample, placing a rock sample above and below the probe, and compressing them to ensure no gaps between the sample and the probe, maximizing heat transfer. After completing the  
Figure 1: The curve of strata temperature versus depth. basic installation and fixation, the instrument is started for testing. For pressurized water-saturated rock samples, after conducting the room temperature testing, the samples are placed into a vacuum pressurization saturation device, subjected to pressure, and treated for 24 h before being taken out for testing. For thermophysical property testing under cyclic thermal loads, the rock samples are first tested for their thermophysical properties before heating. Then, the samples are placed into a muffle furnace, with the automatic heating program set to heat at a rate of 2 \({}^{\circ}\)C per minute, increasing the temperature to 60 \({}^{\circ}\)C and maintaining it for 2 h. After completing the heating process, the furnace door is opened, and the samples are allowed to cool naturally to room temperature before conducting another thermophysical property test. This heating and testing process is repeated. For stepwise temperature increase testing, the rock samples and the Hot Disk probe are placed into an oven, controlling the temperature increase gradient at 10 \({}^{\circ}\)C intervals. The thermophysical properties of the samples are measured at 30 \({}^{\circ}\)C, 40 \({}^{\circ}\)C, 50 \({}^{\circ}\)C, and 60 \({}^{\circ}\)C. Once the oven reaches the predetermined temperature, the heating power is adjusted, and the samples are continuously heated. When the sample temperature remains within 1 \({}^{\circ}\)C of the oven temperature for one hour, the thermophysical property testing begins. Temperature has a significant impact on the thermal properties of rocks, affecting heat transfer within rocks and heat exchange between rocks and underground roadway air, ultimately influencing the temperature distribution of underground roadway surrounding rocks and the thermal environment inside the underground roadway.