Bolt axial force monitoring based on fiber grating technology

Optical fiber sensors are widely used in long-term monitoring in complex environments due to their advantages of anti-electromagnetic interference, high temperature resistance and corrosion resistance. In view of the challenge of supporting structure stability brought by deep mining, the traditional electric measuring bolt system has the disadvantages of electromagnetic interference and complex installation, and more reliable monitoring technology is urgently needed. In this paper, a mine-used fiber Bragg grating anchor sensor technology is proposed. The Bragg grating chain is connected and embedded into the anchor rod, which solves the problems that the surface-mounted grating anchor rod cannot be reused and is easily affected by the environment, and has the ability to monitor the stress state of the anchor rod in real time and for a long time. Through the monitoring of the axial force of the end anchor and the full anchor bolt in the 12,511 working face of Bulianta Coal Mine, it is found that the average axial force of the end anchor body is 77.24 kN, and the full anchor is 67.90 kN. The axial force of the end anchor bolt is 1.14 times that of the full anchor bolt. For broken coal, the full anchor bolt shows higher reliability, which provides reference value for mine support design.