Theoretical and experimental investigations on temperature variations in granodiorite with a hole during biaxial loading and its potential implications for monitoring changes in the crustal stress

摘要

The question of how to obtain information on the dynamic, spatiotemporal characteristics of crustal stress is of significant concern, especially to elucidate plate tectonics and earthquakes. In this paper, we develop a new method to measure the magnitude and direction of stress changes via temperature distribution. We derive the theoretical relationship between the temperature in the vicinity of a hole and the outer stress according to the principles of rock mechanics and thermodynamics. To verify the theoretical result, we conduct an experiment on the temperature variations in a rock sample with a hole during biaxial loading under dry conditions. The rock sample was a 300 mm × 300 mm × 50 mm block of granodiorite, in which a borehole with a radius of 50 mm was drilled. Platinum resistance thermometers were used to measure the temperatures along the hole during biaxial loading. The loading modes included monotonic loading/unloading and sine wave loading. The experimental results indicate that the temperature around a hole responds sensitively to changes in the stress, following the theoretical expectations. The average temperature response to changes in the stress on the granodiorite was 1.17 mK MPa^{−1 at room temperature. Therefore, the stress change at the surface of a hole can be determined by detecting the temperature, after which the changes in the outer stress can be deduced based on the relationship between the interior stress in the hole and the outer stress loading on the object. Thus, the temperature distribution could be applied to monitor dynamic changes in the crustal stress, including its magnitude and orientation. This method could be largely helpful for exploring changes in the states of stress along seismogenic faults.}