The response mechanism of acoustic and thermal effect when stress causes rock damage

Abstract

During the process of damage and fracture of rock when loaded, its internal energy will be released in the form of acoustic energy and thermal energy. In this paper, the combined monitoring systems of Infrared Radiation (IR) and Acoustic Emission (AE) are used to analyze the acoustic and thermal effect during rock damage under uniaxial compression. The results reveal that before the peak stress, both Variance of Successive Minus Infrared Image Temperature (VSMIT) and Correlation Dimension of AE ringing count (Dm) will mutate with the first stress drop. There is a time corresponding relationship between the two mutations, which can be used as a precursor to the rock failure. In addition, the time of VSMIT mutation in 71.1% of rock samples was before the time of Dm mutation, and there was temporal effect of acoustic and thermal in the process of damage and fracture of the rock. The locations of the temperature anomaly area in thermal infrared images and events (cracks) in the AE three-dimensional map are almost the same. They are consistent with the final failure mode of the rock. In the process of damage and fracture of the rock, the spatial characteristic of acoustic and thermal exists, which indicated the homologous anomalies relationship between AE and IR. Further study on the response mechanism of acoustic and thermal effect shows, that the formation of fracture surface (causing stress drop) at the unstable crack growth stage is the root cause of correspondence between VSMIT mutation and Dm mutation. The research results can provide a future reference for monitoring engineering disasters caused by rock failures, such as coal bursts, mine water inrush and other natural disasters such as earthquakes before they occur.