A Sensing Mechanism and the Application of a Surface-Bonded FBG Dynamometry Bolt

In the present paper, a new type of surface-bonded fiber Bragg grating (FBG) dynamometry bolt is designed. It is assumed that the adhesive layer is a linear viscoelastic material and its creep mechanical behavior is expressed by the standard linear solid model. The shear strain transfer model of the surface-bonded FBG sensor is established. Additionally, the instantaneous and quasistatic strain transfer functions of the surface-bonded FBG sensor are obtained. The functions are validated by a uniaxial tensile test and a long-term constant-load tensile test. The test results show that the strain measured by the FBG sensor has a proportional relationship with the strain measured by the resistance strain gauge. Furthermore, under the fixed load for a long period of time, the strain of the FBG sensor has a tendency to drift and the strain reduction rate is about 40.5%. Finally, the field application is carried out in a mining area. It has been proved that the ground pressure online monitoring system based on the FBG sensing technology can successfully monitor the stress of the rock bolt.