A hydraulic fiber Bragg grating force sensor and its monitoring system for axial bolt load measurement in anchorage engineering

Abstract

The bolt support is one of the most important types of active support in anchorage engineering. The anchorage quality of the bolt is directly linked to the safety and stability of the anchorage engineering. Therefore, it is very important and necessary to monitor the stress state of the bolt. Conventional monitoring instruments are susceptible to electromagnetic interference and can not implement remote long-term monitoring and quasi-distributed measurement. A hydraulic-type FBG sensor for axial bolt load measurement is presented, comprising a pressure ring as a load-carrying structure, hydraulic oil as a transfer medium, an elastic diaphragm and a cantilever as sensitizer, and a FBG as the sensing element. The overall structure and working principle of the sensor are introduced in detail, and the theoretical relationship between the FBG wavelength shift difference and the force is established. Accurate force measurement can be obtained by monitoring the two FBGs’ wavelength shift difference. The experimental results show that the average force sensitivity is 39.61 pm kN−1 in the range of 0–100 kN, and the linear coefficient is above 99.88%. The measurement sensitivity is improved by using the wavelength shift difference as the monitoring data, which avoids the cross-sensitive influence. In addition, WDM and SDM technology is adopted for constructing a FBG quasi-distributed measurement system to realize on-line monitoring of axial bolt load. The sensor proposed in this paper has wide application prospects in the field of health monitoring in anchorage engineering.

Construction and Application of On-Line Roof Separation Monitoring System Based on High-Precision FBG Indicator

“…FBG is a periodic perturbation of the refractive index along the fiber length, which is formed by exposure of the core to an intense optical interference pattern [5,12,15,16]. The structure and reflection characteristics of the fiber grating are shown in Figure 1.…”

“…𝜀 = 6𝐹𝑑 𝐸 𝑏ℎ (18) From the Equations ( 11), (12), and (18), in the L-shape cantilever structure, the displacement-induced fiber grating reflection wavelength drift equation is:…”

“…In recent years, with unique advantages, fiber grating sensing technology has developed rapidly and has been widely used in the fields of civil engineering, mining engineering, and other engineering [9][10][11][12][13][14]. The high-precision Fiber Bragg Grating (FBG) separator, based on the fiber grating sensing principle, is a passive working roof separation sensor with FBG as the core sensitive device.…”

Structural deformation and clamping force monitoring of reconfigurable tooling motivated by strain data in aircraft assembly

“…Guo et al [45] studied a circularly shaped two-dimensional woven fabric material and determined its out-of-plane deflection using in-plane strain. In terms of force measurement based on FBG, Guo et al [46], Tu et al [47], Khomenko et al [48] and Liang et al [49] studied the axial load measurement of bolt under torque. Guo et al [50] and Fernandez et al [51] realized the multi-component force sensing by attaching FBG to elastic transducer.…”

Experimental Study on Overburden Deformation Evolution under Mining Effect Based on Fiber Bragg Grating Sensing Technology

“…Fang e al. combined and integrated the fiber Bragg grating sensing technology with the safety production of coal mining and discussed and applied it in the aspects of roof separation, anchor cable load, goaf temperature, shearer attitude, and so on [29][30][31]. Chai et al conducted a crosscombination study on fiber Bragg grating sensing technology and coal mine production safety issues and tested the mechanical properties of rocks, physical similarity simulation test, and settlement of the huge loose layer by using fiber Bragg grating sensing technology.…”