Fiber bragg grating coupling anchor rod and anchor rod early warning system

Abstract

The invention relates to the technical field of tunnel supporting and monitoring, in particular to a fiber bragg grating (FBG) coupling anchor rod and an anchor rod early warning system.The anchor rod comprises FBG sensors and an anchor rod body, the surface of the anchor rod body is provided with a spirally-rising V-shaped groove in the axial direction, and the FBG sensors are installed in the V-shaped groove; a V-shaped groove is formed in the anchor rod body, a plurality of FBG sensors are arranged in the V-shaped groove at the axial interval of 70-90 cm, the FBG sensors are connected in series through optical fibers, a nano cement encapsulating layer is encapsulated in the V-shaped groove, an anti-explosion connector is installed at the tail end of the anchor rod body, an armored optical cable is connected in the anti-explosion connector, and the armored optical cable is connected with the optical fibers. The application of the technology can improve the strain transmission efficiency and enhance the survival rate and coupling of the optical fiber, and the monitoring range covers the whole length of the anchor rod; data acquisition, processing, analysis and visualization can be integrated, multi-parameter and multi-level early warning is realized, the response speed is high, and the reliability is high.

Description

Technical Field

[0001] This invention relates to the technical field of tunnel support monitoring, specifically to a fiber optic grating coupled anchor bolt and an anchor bolt early warning system. Background Technology

[0002] In tunnel and underground engineering construction, rock bolts are the most common support material due to their high reliability and superior economy. Since rock bolts are mainly installed inside the surrounding rock, their deformation and stress state are difficult to determine, making accurate predictions before danger occurs. As a critical support structure, real-time monitoring of the stress state of rock bolts is crucial. In the sensing and detection process, sensitivity and stability are the main technical influencing factors, while manufacturing processes and costs are also significant factors affecting large-scale production.

[0003] Fiber Bragg grating (FBG) sensing technology is a novel sensing technology that has emerged with the development of FBG fabrication technology. Its sensors possess advantages such as resistance to electromagnetic interference, corrosion resistance, electrical insulation, and high sensitivity. Furthermore, they are resistant to high temperatures and pressures, ensuring safety and reliability, and have broad application prospects. Compared to conventional electromagnetic sensors, FBG anchor bolt anchoring effect sensors have significant advantages in sensitivity, large dynamic range, and reliability. They can be applied to anchor bolt anchoring monitoring, surrounding rock reinforcement, and other fields, becoming an important direction in the development of high-performance anchoring effect sensors. Published literature also reports on some FBG anchor bolts, such as: 1. Chinese Patent: Fiber Bragg Grating Force Measuring Anchor and Method of Use, Application No.: 201210224224.1, Application Date: June 29, 2012, Abstract: This invention relates to a fiber Bragg grating force measuring anchor and method of use. The fiber Bragg grating force measuring anchor includes an anchor, a fiber Bragg grating strain sensor, an optical fiber, a test interface, a protective shell, an end cap, and a fiber Bragg grating data acquisition system. The fiber Bragg grating strain sensor is installed in longitudinal grooves on both sides of the anchor. The test interface is installed inside the protective shell. The protective shell is welded to the top of the anchor. The fiber Bragg grating strain sensor is connected to the test interface and the fiber Bragg grating data acquisition system sequentially via the optical fiber. The end cap covers the protective shell. This invention is easy to install and operate, and has the advantages of strong anti-interference ability and high measurement accuracy. It can be widely used in underground engineering fields such as water conservancy, transportation, and mining.

[0004] 2. Chinese Patent: A Fiber Bragg Grating Force Measuring Anchor Device, Application No.: 201210015934.3, Application Date: 2012.01.17, Abstract: This invention relates to a fiber Bragg grating force measuring anchor device, comprising an optical fiber, a pole beam, and a hollow anchor. The optical fiber is provided with at least one grating, which is attached to the pole beam. The pole beam passes through the hollow anchor. One end of the pole beam is provided with a limiting block, which is locked onto one side of the hollow anchor. The other side of the hollow anchor is provided with a fastening nut and an end nut, both of which are threadedly connected to the pole beam. The hollow anchor is connected to an optical fiber seat by welding. The optical fiber seat is connected to an optical fiber seat cover by threads. The optical fiber seat cover is provided with an optical fiber connection flange. The optical fiber seat cover is connected to a protective cover by threads. The protective cover is provided with an optical fiber outlet. This invention uses a fiber Bragg grating to collect deformation data of the anchor device. Due to the inherent advantages of optical fiber, such as good lightning resistance, strong electromagnetic interference resistance, and long-distance measurement capability, the reliability, measurement accuracy, and data transmission distance of the fiber Bragg grating force measuring anchor device are increased.

[0005] 3. Chinese Patent: An anchor bolt system based on fiber optic grating anchoring monitoring, Application No.: 202410456669.5, Application Date: April 16, 2024, Abstract: This invention discloses an anchor bolt system based on fiber optic grating anchoring monitoring, relating to the field of mine roadway construction technology. It includes a sleeve, an anchor bolt body, a base, a support rod assembly, a fiber optic grating sensor assembly, a cam braking device, a locking mechanism, and a signal detection unit. The anchor bolt body is inserted inside the sleeve, and the base is movably connected to the sleeve via the support rod assembly. The fiber optic grating sensor assembly includes a Bragg grating, a magnetic block, and an optical fiber. The Bragg grating is embedded in the side wall of the anchor bolt body, and the magnetic block is located on the support rod assembly, facing the Bragg grating. The Bragg grating has a magnetic coating. Multiple cam braking devices are provided on the outer wall of the sleeve. Each cam braking device includes a braking cam, a gear, and a rack. The braking cam is connected to the base via a transmission mechanism. This invention utilizes the interaction force between magnetic poles to monitor the anchoring status of anchor bolts, avoiding damage to optical fibers due to high tensile forces. In the event of sudden high stress, it can spontaneously improve the anchoring effect.

[0006] Application research has revealed that the aforementioned fiber optic anchor bolts use adhesive or welded fiber optic grating (FBG) sensors, which suffer from problems such as low strain transfer efficiency, interface slippage, stress hysteresis, and early warning delay. They are unable to effectively capture minute deformations of the surrounding rock, making it difficult to prevent sudden disasters. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by providing a fiber optic grating coupled anchor bolt and anchor bolt early warning system. This system can improve strain transfer efficiency, enhance fiber survival rate and coupling, and cover the entire length of the anchor bolt. It can integrate data acquisition, processing, analysis and visualization to achieve multi-parameter and multi-level early warning, with fast response speed and high reliability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A fiber Bragg grating coupled anchor bolt includes an FBG sensor and an anchor bolt body. The FBG sensor is a high-precision physical quantity monitoring device based on fiber Bragg grating technology, which can be purchased and used commercially. The anchor bolt body has a spirally rising V-shaped groove on its surface along the axial direction. Multiple FBG sensors are installed in the V-shaped groove, arranged at an axial spacing of 70-90 cm, covering both the free and anchored sections of the anchor bolt. When the FBG sensors are embedded in the V-shaped groove, a pre-tension of 0.5 N is applied to eliminate excess length. The multiple FBG sensors are connected in series via optical fibers. A nano-cement encapsulation layer is formed by injecting nano-modified cement-based composite material. Immediately after encapsulation, a flexible silicone pad (0.5 mm thick) is applied, pressure is applied to expel air, and curing is performed for 24 hours. The nano-cement encapsulation layer encapsulates the V-shaped groove, protecting the optical fiber and maintaining the anchor bolt strength. An explosion-proof connector with an IP68 protection rating and a tensile strength ≥120 N is installed at the tail end of the anchor bolt body. An armored optical cable is connected inside the explosion-proof connector, and the armored optical cable is connected to the optical fiber. After the anchor bolt is installed in the anchor bolt hole, pressure grouting is performed in sections. The anchoring section uses fast-setting nano cement grout to form a protective layer for the sensor, while the free section uses ordinary cement grout to reduce the pressure on the optical fiber. The sealing section uses expanding mortar to prevent grout backflow. After the anchor bolt is grouted and fixed, an anchor bolt pressure plate and pressure plate nut are installed on the anchor bolt body at the top of the anchor bolt hole for tensioning and fixing.

[0009] A further preferred embodiment: the V-shaped groove is provided with multiple groove wall protrusions.

[0010] Further preferred configuration: The groove wall protrusions are arranged in an array at equal intervals on the groove wall, particularly within the groove segment corresponding to each FBG sensor grating area, where they are arranged in a focused or continuous manner to ensure that the fiber optic grating area achieves efficient and uniform strain coupling with the anchor rod through multiple rigid protrusions. The V-groove, sandblasting roughening, and groove wall protrusions together constitute a multi-layered, synergistically enhanced coupling system that ranges from "macroscopic groove protection" and "interface reinforcement and anti-slip" to "microscopic contact force transmission".

[0011] A further preferred embodiment: the groove wall protrusions are formed by laser cladding of nano-zirconia ceramic, used to improve strain transfer efficiency and monitoring sensitivity. The mechanism by which these protrusions improve strain transfer efficiency and monitoring sensitivity is based on a strain amplification model that has been theoretically analyzed and experimentally calibrated: S f =1+h / t×E c / E m This formula describes the amplification factor S between the strain εf sensed by the fiber grating (FBG) sensor and the actual strain εm of the anchor bolt base. fWhere h is the height of the micro-protrusion, t is the effective transfer thickness of the encapsulation layer at the top of the protrusion, and Ec and Em are the elastic moduli of the encapsulation material and the anchor matrix, respectively. The groove wall protrusions, acting as rigid contacts, establish a low-loss force transmission path between the anchor and the optical fiber, bypassing the strain loss caused by shear deformation and creep in traditional adhesive layers. The presence of the groove wall protrusions alters the local stress field of the encapsulation layer. When the anchor deforms, the encapsulation layer undergoes controlled shear deformation around the micro-protrusions, and this shear strain is efficiently converted into the axial tensile strain of the optical fiber. The formula shows that by optimizing h / t (geometric design) and Ec / Em, S can be actively improved. f This amplifies the sensing signal. After the nano-cement is encapsulated, the micro-protrusions and the encapsulating material form a three-dimensional interlock, which greatly suppresses the micro-slippage of the interface and ensures the immediacy and fidelity of signal transmission.

[0012] Further preferred embodiment: The V-shaped groove is subjected to sandblasting roughening treatment with Ra=12.5μm. The purpose is to significantly increase the surface roughness of the metal groove wall, thereby greatly improving the interfacial adhesion and mechanical interlocking force between the nano-cement grout and the anchor rod substrate, and preventing overall interfacial slippage under long-term stress.

[0013] A further preferred embodiment: the explosion-proof connector is filled with ceramicized silicone rubber.

[0014] A fiber Bragg grating coupled anchor bolt early warning system includes a fiber demodulator, a power supply, a data comparison and analysis processing platform, a wireless data transmitter, and the aforementioned fiber Bragg grating coupled anchor bolt. The fiber Bragg grating coupled anchor bolt is communicatively connected to the signal port of the fiber demodulator via an armored optical cable. The fiber demodulator is connected to the wireless data transmitter via a data cable. The wireless data transmitter is communicatively connected to the data comparison and analysis processing platform. The power supply is connected to both the fiber demodulator and the wireless data transmitter via power cables, providing power to both. The data comparison and analysis processing platform is an intelligent early warning software developed based on MATLAB, possessing data acquisition, processing, analysis, and visualization functions; supporting real-time monitoring and historical data querying of multiple parameters such as stress, displacement, tilt angle, and environment; built-in calculation models for stress change rate and displacement time slope; supporting multi-level early warning threshold settings; and featuring functions such as curve graphs, scatter plots, early warning alarms, screen capture, and data clearing; supporting multiple communication methods such as LoRa, NB-IoT, and 4G / 5G to achieve remote monitoring and early warning push. After the anchor bolts are installed, allow them to stand for the grout to fully solidify. Collect the initial wavelength λ0 of each FBG sensor (accuracy ±0.1 pm) and set two-level warning threshold baselines. Apply a stepped load to the anchor bolts (0 → Level 1 threshold → Level 2 threshold) to verify the system response. Upon reaching the Level 1 threshold, the system platform pushes a warning message; upon reaching the Level 2 threshold, an audible and visual alarm is activated.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The anchor bolt body adopts a spiral V-groove design and nano-cement grouting to provide a protected laying channel for optical fibers and maintain the strength of the anchor bolt. The spiral design avoids stress concentration in straight laying and ensures continuous coupling between optical fibers and anchor bolt after grouting, enhancing the coupling between anchor bolt and optical fiber, improving construction survival rate and monitoring reliability, and the monitoring range covers the entire length of the anchor bolt.

[0016] 2. A micro-protrusion strain amplification structure is set in the spiral V-groove. By laser cladding of nano-ceramic protrusions, the strain transmission efficiency and monitoring sensitivity are improved, enabling the monitoring of minute displacements at the 0.05mm level.

[0017] 3. Multi-sensor cascading and multi-level early warning mechanism: The early warning system integrates data acquisition, processing, analysis and visualization, supports remote monitoring and multi-level alarms, and realizes full-length monitoring and real-time response intelligent early warning. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the connection structure of the fiber optic grating coupled anchor bolt early warning system; Figure 2 This is a schematic diagram of the structure of the fiber optic grating coupled anchor. Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of the middle anchor bolt; The names corresponding to the serial numbers in the figure are: 1. Anchor bolt hole; 2. FBG sensor; 3. Quick-setting nano-cement grout; 4. V-groove; 5. Anchor bolt body; 6. Ordinary cement grout; 7. Expansive mortar; 8. Anchor bolt pressure plate; 9. Pressure plate nut; 10. Explosion-proof connector; 11. Armored optical cable; 12. Fiber optic demodulator; 13. Power supply; 14. Data comparison and analysis processing platform; 15. Wireless data transmitter; 16. Nano-cement grouting layer; 17. Optical fiber; 18. Groove wall protrusion. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0020] Example 1

[0021] like Figure 2 and 3As shown, a fiber optic grating coupled anchor bolt includes an FBG sensor 2 and an anchor bolt body 5. The surface of the anchor bolt body 5 has a spirally rising V-groove 4 along its axial direction. Multiple FBG sensors 2 are installed within the V-groove 4, arranged at an axial spacing of 80 cm, covering both the free and anchored sections of the anchor bolt. When the FBG sensors are embedded into the V-groove, a pre-tension of 0.5 N is applied to eliminate excess length. The multiple FBG sensors 2 are connected in series via optical fibers 17. High-temperature resistant epoxy resin (temperature resistance 260℃) is applied to both sides of the optical fibers at 10 mm intervals using micro-dispensing technology to temporarily fix the optical fibers. The V-groove 4 is filled with a nano-cement filling layer 16, which means that multiple FBG sensors with different center wavelengths (e.g., 1528 nm, 1545 nm, 1568 nm) are fabricated on a continuous optical fiber to form a fiber optic grating string. This fiber optic string is embedded into the spiral V-groove at once, allowing each sensor grating area to be precisely positioned at a preset monitoring section (e.g., the free section or the anchored section). After the fiber optic cable is implanted, the entire V-groove is encapsulated using a nano-cement-based composite material. After the encapsulation material cures, it bonds the fiber optic cable, micro-protrusions, and anchor bolt into a single unit, providing stress coupling, physical protection, and corrosion prevention. Armored optical cables and explosion-proof connectors are used at the ends to ensure overall reliability. The nano-cement encapsulation layer 16 is made by injecting nano-modified cement-based composite material. Immediately after encapsulation, a flexible silicone pad (0.5mm thick) is applied, pressure is applied to expel air, and curing is performed for 24 hours. The nano-cement encapsulation layer 16 encapsulates the V-groove, protecting the fiber optic cable and maintaining the anchor bolt strength. An explosion-proof connector 10 with an IP68 protection rating and a tensile strength ≥120N is installed at the tail end of the anchor bolt body 5. An armored optical cable 11 is connected inside the explosion-proof connector 10, which is connected to the fiber optic cable 17. The explosion-proof connector 10 is filled with ceramicized silicone rubber. After the anchor bolt is installed in the anchor bolt hole 1, pressure grouting is performed in sections. The anchoring section uses fast-setting nano cement grout 3 to form a protective layer for the sensor, while the free section uses ordinary cement grout 6 to reduce the pressure on the optical fiber. The sealing section uses expanding mortar 7 to prevent grout backflow. After the anchor bolt is grouted and fixed, the anchor bolt pressure plate 8 and pressure plate nut 9 are installed on the anchor bolt body 5 at the top of the anchor bolt hole 1 for tensioning and fixing.

[0022] The V-groove 4 is provided with multiple groove wall protrusions 18. The anchor body 5 is made of threaded steel anchor with a diameter of 22mm. A spiral V-groove is opened on the surface using laser precision grooving technology. The groove is 1.8mm deep and 2mm wide at the top. The groove extends with a spiral helix angle of 15° to avoid stress concentration in the straight laying of optical fibers. The groove wall protrusions 18 are provided with hemispherical micro-protrusions (0.2mm high and 0.4mm radius of curvature). The rigidity is enhanced by laser cladding of nano-zirconia ceramic.

[0023] The aforementioned groove wall protrusions 18 are arranged in an array at equal intervals on the groove wall, especially in the groove segment corresponding to each FBG sensor grid area, where they are arranged in a focused or continuous manner to ensure that the fiber optic grid area achieves efficient and uniform strain coupling with the anchor rod through multiple rigid protrusions. The V-groove, sandblasting roughening, and groove wall protrusions together constitute a multi-level, synergistically enhanced coupling system from "macro-channel protection" and "interface reinforcement and anti-slip" to "micro-contact force transmission".

[0024] The groove wall protrusions 18 are formed by laser cladding of nano-zirconia ceramics, which is used to improve strain transfer efficiency and monitoring sensitivity.

[0025] The V-groove 4 is roughened by sandblasting with Ra=12.5μm. The purpose is to significantly increase the surface roughness of the metal groove wall, thereby greatly improving the interfacial adhesion and mechanical interlocking force between the nano-cement grout and the anchor rod substrate, and preventing overall interfacial slippage under long-term stress.

[0026] like Figure 1 As shown, a fiber Bragg grating coupled anchor bolt early warning system includes a fiber demodulator 12, a power supply 13, a data comparison and analysis processing platform 14, a wireless data transmitter 15, and the aforementioned fiber Bragg grating coupled anchor bolt. The fiber Bragg grating coupled anchor bolt is communicatively connected to the signal port of the fiber demodulator 12 via an armored optical cable 11. The fiber demodulator 12 is connected to the wireless data transmitter 15 via a data line. The wireless data transmitter 15 is communicatively connected to the data comparison and analysis processing platform 14. The power supply 13 is connected to both the fiber demodulator 12 and the wireless data transmitter 15 via power lines to supply power to both. The data comparison and analysis processing platform 14 is an intelligent early warning software developed based on MATLAB. It possesses data acquisition, processing, analysis, and visualization functions; supports real-time monitoring and historical data querying of multiple parameters such as stress, displacement, tilt angle, and environment; has built-in calculation models for stress change rate and displacement time slope; supports multi-level early warning threshold settings; and features functions such as curve graphs, scatter plots, early warning alarms, screen capture, and data clearing. It supports multiple communication methods such as LoRa, NB-IoT, and 4G / 5G to achieve remote monitoring and early warning push notifications. After the anchor bolts are installed, they are left to stand for the grout to fully solidify. The initial wavelength λ0 of each FBG sensor is collected (accuracy ±0.1 pm), and two-level early warning threshold benchmark values ​​are set. A stepped load (0 → first-level threshold → second-level threshold) is applied to the anchor bolts to verify the system response. Upon reaching the first-level threshold, the system platform pushes an early warning information; upon reaching the second-level threshold, the audible and visual alarm is activated.

[0027] At the engineering site, the following equivalent, controllable, and non-destructive methods can be used to verify the system response: Level 1 early warning function verification (strain rate threshold): Torque-tension conversion method: Using anchor tensioning equipment, a small, step-increasing additional tension is applied. The loading interval is controlled so that the strain rate calculated by the monitoring software artificially exceeds the threshold of 0.05 nm / h to test the platform's early warning push function.

[0028] Functional simulation method: Using a portable fiber optic demodulation simulator, a pre-programmed data stream simulating the strain rate exceeding the threshold is injected into the monitoring host to verify the software alarm logic.

[0029] Level 2 alarm function verification (stress threshold): Local disturbance method: At the exposed end of the anchor bolt, use a portable loader to apply a large instantaneous lateral force, so that the local stress of the anchor bolt exceeds 0.8ƒy for a short time, and check whether the on-site audible and visual alarm is activated.

[0030] Software threshold test method: Temporarily modify the sensor reference value in the background of the monitoring software to simulate the stress over-limit state and verify the alarm triggering process.

[0031] We recommend conducting on-site system acceptance testing using the following steps: Initial calibration: After installation, allow the sensor to stand for 24 hours and record the initial wavelength of each sensor.

[0032] Level 1 warning test: Use any of the above methods to trigger a Level 1 warning once and confirm that the information push was successful.

[0033] Level 2 alarm test: Trigger a level 2 alarm once to confirm that the audible and visual alarm is activated.

[0034] System Reset: After the test is completed, the test data is cleared and the normal monitoring mode is restored.

[0035] The actual effect of the micro-protrusion structure on improving strain transfer efficiency was verified, and the quantitative comparison of strain transfer efficiency is recorded in Table 1.

[0036] Verification method: Under the same load, the strain of the anchor body (reference value) and the strain measured by the FBG sensor are measured simultaneously, and the actual strain transfer coefficient η = εFBG / εreference is calculated.

[0037] Table 1

[0038] Conclusion: The average strain transfer efficiency of the present invention is as high as 96%-97%, which is significantly improved compared with the traditional solution (≈75%), and effectively solves the problems of strain loss and distortion.

[0039] Minimum monitoring displacement and sensitivity verification Validation and mechanism analysis of monitoring sensitivity (0.05 mm micro-displacement) Experimental Objective: To directly verify the device's ability to monitor axial displacement at the 0.05mm level and to explain, in principle, how the micro-protrusion structure enhances sensitivity. A precise axial micro-displacement ΔL is applied to the end of the free section of the anchor bolt using a precision displacement stage, and the change in the center wavelength Δλ of the FBG is measured.

[0040] The experimental data for micro-displacement monitoring are shown in Table 2 (taking a 1545nm sensor as an example).

[0041] Table 2

[0042] Calculation instructions: Theoretical strain: εm = ΔL / L = 0.05 / 2400 = 2.08 × 10⁻⁶ −5 =20.8 με (anchor length L=2.4 mL=2.4m). Using the FBG strain sensitivity coefficient Kε=1.2 pm / με, the measured strain εf=Δλ / Kε=24.8 / 1.2=20.7 με. The data shows that the system has a high signal-to-noise ratio for a displacement of 0.05mm, and the measured value is in high agreement with the theoretical value.

[0043] Mechanism analysis of sensitivity enhancement: The micro-protrusion structure not only improves the strain transfer efficiency (η), but also further enhances the effective sensitivity of the system through the strain amplification effect.

[0044] Traditional solution for sensing strain: εftraditional = ηtraditional·εm (ηtraditional ≈ 0.75).

[0045] The strain sensed by this invention is: εf_invention = Sf·η_invention·εm (η_invention ≈ 0.97, Sf_invention ≈ 0.97, εm ... f (This is the magnification factor).

[0046] By combining the amplification factor model Sf=1+h / t×Ec / Em, the strain sensed by the FBG in this invention is significantly amplified.

[0047] For the same anchor base strain εm, the wavelength change Δλ of the FBG in this invention will be larger, thus making it more sensitive to small εm (i.e. small displacement ΔL).

[0048] Quantitative manifestation of sensitivity improvement: Define the system's displacement-wavelength sensitivity Sd = Δλ / ΔL.

[0049] Theoretical calculation: For the traditional scheme, Sdtraditional = Kε·ηtraditional / L ≈ 1.2 × 0.75 / 2400 = 0.000375 pm / μm.

[0050] The actual measurement of this invention: From the data in Table 2, when ΔL=0.05 mm, Δλ=24.8 pm, then Sd of this invention=24.8 / 50=0.496 pm / μm.

[0051] The wavelength change caused by a unit displacement in the present invention is much greater than that in the traditional scheme, resulting in an order-of-magnitude improvement in effective sensitivity.

[0052] The above description is not intended to limit the present invention, nor is the present invention limited to the above examples. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A fiber optic grating coupled anchor bolt, comprising an FBG sensor (2) and an anchor bolt body (5), characterized in that: The surface of the anchor body (5) is provided with a spiral V-shaped groove (4) along the axial direction. Multiple FBG sensors (2) are installed in the V-shaped groove (4). The multiple FBG sensors (2) are arranged in the V-shaped groove (4) with an axial spacing of 70-90 cm. The multiple FBG sensors (2) are connected in series through optical fiber (17). The V-shaped groove (4) is filled with a nano cement filling layer (16). An explosion-proof connector (10) is installed at the tail end of the anchor body (5). An armored optical cable (11) is connected in the explosion-proof connector (10). The armored optical cable (11) is connected to the optical fiber (17).

2. The fiber optic grating coupled anchor bolt according to claim 1, characterized in that, The V-groove (4) is provided with multiple groove wall protrusions (18).

3. The fiber optic grating coupled anchor bolt according to claim 2, characterized in that, The groove wall protrusions (18) are arranged in an array at equal intervals on the groove wall.

4. The fiber optic grating coupled anchor bolt according to claim 2 or 3, characterized in that, The groove wall protrusions (18) are formed by laser cladding of nano-zirconia ceramics.

5. The fiber optic grating coupled anchor bolt according to claim 2 or 3, characterized in that, The V-groove (4) is subjected to sandblasting roughening treatment.

6. The fiber optic grating coupled anchor bolt according to claim 1, characterized in that, The explosion-proof connector (10) is filled with ceramicized silicone rubber.

7. A fiber optic grating coupled anchor bolt early warning system, characterized in that, The system includes a fiber optic demodulator (12), a power supply (13), a data comparison and analysis processing platform (14), a wireless data transmitter (15), and a fiber optic grating coupling anchor as described in claim 1. The fiber optic grating coupling anchor is connected to the signal port of the fiber optic demodulator (12) via an armored optical cable (11). The fiber optic demodulator (12) is connected to the wireless data transmitter (15) via a data line. The wireless data transmitter (15) is connected to the data comparison and analysis processing platform (14). The power supply (13) is connected to the fiber optic demodulator (12) and the wireless data transmitter (15) via a power line to supply power to the fiber optic demodulator (12) and the wireless data transmitter (15).

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