Internal Strain Monitoring of Coal Samples Based on Fiber Bragg Grating Sensing

Abstract The current researches on strain mainly have focused on the surface strain and lacked the monitoring of internal strain, due to the imperfection of real-time monitoring technology for internal strain. In order to obtain the internal strain evolution law in the process of coal sample crack propagation, this paper used a fiber Bragg grating monitoring system to study the internal strain change law of coal samples with different structures during the loading process. The results show that the internal strain is more sensitive than the axial strain when the sample is partially destabilized; in the crack propagation stage, the strain at some measurement points changes abruptly and when the overall instability is approaching, the strains of most measurement points have a sudden change; during the load-holding stage, the axial strain rate of coal samples with holes is greater than that of intact coal samples. This research provides a basis for rock burst strain monitoring based on internal strain field data in the future.