Fiber Bragg Grating Monitoring of Full-bolt Axial Force of the Bolt in the Deep Strong Mining Roadway

Abstract

With the increase of mining depth and strength, the evolution of bolt axial force is increasingly becoming important for ensuring the reliability and safety of support. To improve the problem of the existing coal mine roadway pressure-monitoring method, whereby it is difficult to continuously monitor the axial force of the bolt over a long period of time, a full rod fiber bragg grating (FBG) force-measuring bolt and system were designed based on the principle of fiber grating sensing. It was found that a trapezoidal groove is a relatively better groove. The linearity between the center wavelength offset of the fiber grating and the axial force was more than 0.99, and the conversion formula between the axial force of the bolt rod and the wavelength change of the fiber grating were obtained. The real-time monitoring revealed that the axial force of the bolt obviously changed before and after compression. The axial force distribution curve can be divided into the stable zone, growth zone, and peak zone. The influence of the roadway abutment pressure was approximately 130 m ahead of the working face, and the peak area was within the 25–35 m range of the advance working face. The axial force of the bolt rod at the end of the anchorage linearly increased with the tail end of the bolt, the axial force of the free segment was the largest, and the overall stress was essentially the same. The application results demonstrate the feasibility and effectiveness of the FBG full-length force bolt.

Research on Three-Dimensional Stress Monitoring Method of Surrounding Rock Based on FBG Sensing Technology

“…Zhi Zhou developed a fiber-grating-based 3D strain sensor for highway and civil structure health monitoring [ 19 ]. In the mining field, Liang Minfu proposed an FBG inclination sensor to monitor the attitude of hydraulic support [ 20 ]; Tao Zhigang monitors coal and rock movement in real time based on a quasi-distributed FBG sensor, which provides a basis for pillar-free mining [ 21 ]; Wang Peng designed an FBG force measuring bolt to continuously monitor the roof pressure of the coal roadway [ 22 ]; Chai Jing uses an FBG sensor to monitor the structural deformation of key layers at different stages and finally realizes the inversion of overburden state in goaf [ 23 ]; Wan Xiaorong developed an FBG stress sensor to predict the stability after coal roadway excavation [ 24 ]. However, the application of FBG three-dimensional stress sensors in coal mine engineering has not been reported, so it is significance to study the application of three-dimensional stress sensors in the surrounding rocks.…”

Monitoring the safety status of service bolts in mining roadways

“…They analyzed the critical value of roof separation for various roadways [ 11 ]. Peng Wang (2020) et al used the principle of fiber grating sensing to develop and apply force-measuring bolts and systems to verify the feasibility of force-measuring bolts, which are used to monitor the pressure of coal mine roadways [ 12 ]. Hao Jian (2021) et al analyzed the influence of active and passive supports on roadway stability.…”

Structural Design and Application of Desensitized FBG Force-Measuring Bolt

“…Zhao Yiming et al [ 21 ] studied the influence of groove shape on the strength of FBG-FMB, and provided practical suggestions for pasting glue in engineering practice. Wang Peng et al [ 22 ] designed a full-length anchored FBG-FMB and monitoring system after deriving the conversion equation between the axial force of the bolt and the FBG wavelength variation. However, most of the existing FBG-FMB have the problem that the strain of the bolt and the FBG strain are uncoordinated, so the FBG is very easy to break in the field application, which greatly reduces the reliability of the FBG-FMB.…”