Self-sensing anchor rod and manufacturing method thereof

Abstract

The invention relates to the technical field of mine supporting and intelligent monitoring, in particular to a self-sensing anchor rod and a manufacturing method thereof.The self-sensing anchor rod comprises a core body and an FRP layer wrapping the surface of the core body; the surface of the core body is provided with a plurality of mounting grooves for fixing a grating sensor at intervals, and the FRP layer is internally provided with an optical fiber channel through which a transmission optical fiber of the grating sensor passes; a guide pipe is fixed between the mounting groove and the optical fiber channel, and a transmission optical fiber of the grating sensor is guided into the optical fiber channel through the guide pipe, so that the transmission optical fiber extends along the optical fiber channel and is connected with a signal system on a nut at the top end of the core body. The problem that a traditional technology depends on an external sensor can be solved, meanwhile, the requirements for high-strength supporting and surrounding rock displacement monitoring are met, and the device is suitable for coal mine tunnels, tunnel engineering and slope reinforcement scenes and has the structural stability and the real-time monitoring function.

Description

Technical Field

[0001] The present invention relates to the technical field of mine support and intelligent monitoring, and particularly relates to a self-sensing bolt and a manufacturing method thereof. Background Art

[0002] Fiber Reinforced Polymer (FRP) bolts are widely used in the reinforcement and support operations of geotechnical engineering such as coal mine roadways, slopes, foundation pits, and tunnels due to their characteristics of light weight, high strength, corrosion resistance, simple construction, and excellent mechanical properties. As the core main load-bearing component of the reinforcement structure, the performance status of FRP bolts is directly related to the safety stability and operation effectiveness of the entire geotechnical anchoring project. Therefore, it is extremely crucial to monitor the stress state of the bolt throughout the service period.

[0003] Traditional bolt support technologies mostly use external sensors such as optical fibers, resistance strain gauges, or mechanical displacement gauges to achieve the monitoring of surrounding rock deformation. However, such technologies have a series of drawbacks, including complex structures, high costs, difficult maintenance, relatively single functions, and have never been able to overcome the inherent limitations of external sensors. Summary of the Invention

[0004] The purpose of the present invention is to provide a self-sensing bolt and a manufacturing method thereof, which can solve the problem of traditional technologies relying on external sensors, while meeting the requirements of high-strength support and surrounding rock displacement monitoring, being applicable to coal mine roadways, tunnel projects, and slope reinforcement scenarios, and having both structural stability and real-time monitoring functions.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: In the first aspect, the present invention discloses a self-sensing bolt, which includes a core body and an FRP layer wrapped on the surface of the core body; a plurality of mounting grooves for fixing grating sensors are arranged at intervals on the surface of the core body, and an optical fiber channel for the transmission optical fiber of the grating sensor to pass through is arranged in the FRP layer; a guiding tube is fixed between the mounting groove and the optical fiber channel, and the transmission optical fiber of the grating sensor is guided into the optical fiber channel through the guiding tube, so that the transmission optical fiber extends along the optical fiber channel and is connected to the signal system on the nut at the top end of the core body.

[0006] Further, the core body includes a functional section, a transition section, and a main body section arranged in sequence from the bottom end to the top end. The outer diameter of the functional section is greater than that of the main body section, and the outer diameter of the transition section gradually changes from the outer diameter of the functional section to the outer diameter of the main body section; The length of the functional section is 80 - 120 mm; The length of the transition section is 30 - 50 mm, and the taper angle is less than 5°.

[0007] Furthermore, the optical fiber channels corresponding to the transition section and the main body section are arranged in a straight line, and the optical fiber channel corresponding to the functional section is arranged in a spiral shape.

[0008] Furthermore, after the surface of the functional section is subjected to laser micro-texturing treatment, nano-SiO 2 modified epoxy resin is sprayed; after the surfaces of the transition section and the main body section are subjected to sandblasting treatment, epoxy resin is coated. This improves the interfacial bonding strength.

[0009] Furthermore, at least one temperature compensation FBG is fixed in the FRP layer corresponding to the top end of the core body.

[0010] Furthermore, the grating sensor is adhesively fixed in the installation groove.

[0011] Furthermore, the FRP layer is sequentially provided with a main load-bearing layer, a shear-resistant layer, and a chopped fiber layer from outside to inside. The laying angle of the main load-bearing layer is 0°, the laying angle of the shear-resistant layer is ±45°, and the optical fiber channel is located between the main load-bearing layer and the shear-resistant layer.

[0012] In a second aspect, the present invention discloses a manufacturing method of a self-sensing bolt, which includes: Providing a core body blank; Mechanically processing a plurality of installation grooves for fixing the grating sensor on the core body blank; Fixing the grating sensor in the installation groove; Forming an FRP layer through a prepreg process. A guiding tube is embedded at a position corresponding to the installation groove in the prepreg layer, and a lining channel is embedded at the optical fiber channel position. The transmission optical fiber of the grating sensor is led out along the guiding tube to the inside of the lining channel through a yarn guide; Putting the core body wrapped with the prepreg layer in a mold for curing to obtain a self-sensing bolt.

[0013] Furthermore, the temperature during curing is set to 120~180°C, the pressure is set to 10~20 MPa, and the curing time is set to 30~60 min.

[0014] Furthermore, fixing the grating sensor in the installation groove specifically includes: coating an adhesive in the installation groove, using a vacuum fixture to fix the grating sensor to a preset position in the installation groove, and curing the adhesive to achieve the fixation of the grating sensor.

[0015] The present invention has the following unexpected beneficial effects: 1. The present invention fixes the grating sensor by arranging an installation groove on the surface of the core body, and cooperates with the optical fiber channel and the guiding pipe in the FRP layer to guide and connect the transmission optical fiber to the signal system, enabling the FRP anchor rod itself to have a sensing ability, capable of real-time monitoring of the stress state of the anchor rod, without relying on traditional external sensors, effectively overcoming the limitations of traditional technologies, and improving the convenience and reliability of monitoring. Compared with the problems of large environmental interference and easy change of installation position of traditional external sensors, the grating sensor of this self-sensing anchor rod is directly installed on the core body, closely combined with the anchor rod, can more accurately sense the change of the stress of the anchor rod itself, and then improve the accuracy of monitoring the state of geotechnical anchoring projects, providing more reliable data support for the safe operation of the project.

[0016] 2. The core body and the FRP layer achieve complementary mechanical properties. The core body has both structural support and self-sensing functions, and the FRP layer serves as both a signal channel and an anti-corrosion protection shell, completely abandoning external sensors. Furthermore, a large amount of investment in sensor equipment and maintenance work is reduced. The self-sensing anchor rod integrates the sensing function into the anchor rod body, with a relatively simple structure, reducing the equipment cost, and at the same time reducing the maintenance workload caused by sensor failures or line problems, improving the economy and stability of the project.

[0017] 3. The collaborative design of the installation groove, the optical fiber channel and the guiding pipe in the present invention not only ensures the stability of the installation of the grating sensor, but also provides a reasonable wiring layout for the transmission optical fiber, making the entire self-sensing anchor rod structure compact and orderly, and will not affect the mechanical properties and use effects of the anchor rod itself due to problems with the arrangement of sensors and optical fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The structural schematic diagram of the self-sensing anchor rod described in the embodiment of the present invention is shown.

[0019] Figure 2 Shown is Figure 1 The A-A sectional view of

[0020] Figure 3 The partial enlarged schematic diagram of the transition section described in the embodiment of the present invention is shown.

[0021] In the figure, 1 - core body, 11 - functional section, 12 - transition section, 13 - main body section, 2 - FRP layer, 3 - grating sensor, 31 - transmission optical fiber, 4 - installation groove, 5 - optical fiber channel, 6 - guiding pipe, 7 - signal system, 8 - temperature compensation FBG. DETAILED DESCRIPTION OF THE INVENTION

[0022] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0023] It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Therefore, only the components related to the present invention are shown in the diagrams, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the layout type of its components may also be more complex.

[0024] In one embodiment, as shown in Figures 1 to 3 the present invention discloses a self-sensing bolt, which includes a core body 1 and an FRP layer 2 wrapped on the surface of the core body 1; a plurality of installation grooves 4 for fixing a grating sensor 3 are arranged at intervals on the surface of the core body 1, and an optical fiber channel 5 through which the transmission optical fiber 31 of the grating sensor 3 passes is arranged in the FRP layer 2; a guiding tube 6 is fixed between the installation groove 4 and the optical fiber channel 5, and the transmission optical fiber 31 of the grating sensor 3 is guided into the optical fiber channel 5 through the guiding tube 6, so that the transmission optical fiber 31 extends along the optical fiber channel 5 and is connected to a signal system 7 on the nut at the top end of the core body 1.

[0025] Exemplarily, the core body 1 is a stainless steel core body, and the grating sensor 3 is an FBG grating.

[0026] In the present invention, the installation groove 4 is arranged on the surface of the core body 1 to fix the grating sensor 3, and the optical fiber channel 5 is reserved in the FRP layer 2. The installation groove 4 and the optical fiber channel 5 are connected by a guiding tube 6, and the layout is compact and reasonable. It not only ensures the stable installation of the grating sensor 3, but also provides a safe and stable routing space for the transmission optical fiber 31, avoiding damage to the optical fiber under complex working conditions, and at the same time not affecting the overall mechanical performance of the bolt. For example, in environments such as coal mine roadways, the bolt needs to bear large pressure and friction, and this structure can ensure the stable transmission of signals by the optical fiber and guarantee the continuous progress of the monitoring work.

[0027] Through the collaborative work of the grating sensor 3, the optical fiber channel 5 and the signal system 7, the present invention enables the bolt to have self-sensing ability and can monitor its own stress and strain state in real time. Compared with the traditional bolt relying on external sensors, this design overcomes the disadvantages of complex structure and susceptibility to interference of external sensors, can directly obtain the strain information of the bolt body, provides reliable data support for the safety monitoring of geotechnical engineering, and timely discovers potential safety hazards. And because the grating sensor 3 is directly installed on the core body 1, it can more accurately sense the force change of the bolt, reducing the monitoring error caused by the installation position deviation of the external sensor or environmental interference. The settings of the optical fiber channel 5 and the guiding tube 6 ensure the stability of signal transmission, effectively reduce signal attenuation and interference, improve the accuracy and reliability of monitoring data, and enhance the effectiveness of the monitoring of geotechnical anchoring engineering.

[0028] The FRP layer 2 of the present invention not only provides structural protection, but also can effectively shield external electromagnetic interference, creating a good environment for optical fiber transmission signals. In engineering scenarios such as mines and tunnels with strong electromagnetic interference, this bolt can work stably, ensuring the authenticity and timeliness of monitoring data and guaranteeing the safe and stable operation of the project.

[0029] The overall structural design of the present invention is convenient for installation and maintenance. The modular design of the sensor installation groove and the optical fiber channel reduces the installation difficulty and improves the construction efficiency. If the sensor or the optical fiber fails, it can be repaired or replaced specifically, reducing the maintenance cost and time, and improving the economy and stability of project operation.

[0030] The self-sensing bolt of the present invention has a wide range of application scenarios. This self-sensing bolt is applicable to various geotechnical engineering, such as coal mine roadways, tunnel projects, slope reinforcement, etc. Its self-sensing function and good performance can meet the requirements of different projects for bolt support and real-time monitoring, provide a strong guarantee for the safety and stability of various geotechnical engineering, and have a broad market application prospect.

[0031] As a preferred implementation manner of the present invention, an electronic chamber is processed inside the nut at the top end of the core body 1, and the signal system is integrated in the electronic chamber. With such a setting, the space is effectively saved and the overall structure of the bolt is more compact. This compact design is not only convenient for installation in various engineering scenarios, but also can reduce the structural complexity caused by additional equipment, reduce the impact on the mechanical properties of the bolt, and improve the practicability and stability of the bolt.

[0032] The signal system 7 includes an optical fiber demodulation unit (tunable laser + photodetector) and a wireless transmission module (LoRa / NB-IoT), is docked with the end of the bolt through an MTP optical fiber connector, and the power supply uses a miniature lithium manganese battery (such as CR1220). The outside of the signal system is connected to the pigtail at the top end of the bolt through a spring pogo pin to activate the signal system.

[0033] The integrated optical fiber demodulation unit (tunable laser + photodetector) can convert the optical signal collected by the grating sensor 3 into an electrical signal, achieving accurate demodulation of the bolt strain information. Cooperating with the wireless transmission module (LoRa / NB-IoT), it can remotely transmit the processed monitoring data to the monitoring center without on-site wiring and manual regular data collection, greatly improving the convenience and real-time performance of monitoring.

[0034] The MTP fiber optic connector is used to dock with the end of the bolt. This connector has the characteristics of high precision and high reliability, which can ensure the stable transmission of the fiber optic signal, reducing signal loss and interference. The signal system 7 is externally connected to the pigtail at the top of the bolt through a spring pin to activate the signal system. This contactless connection method is not only simple and convenient to operate, but also avoids interface damage caused by frequent plugging and unplugging, improving the stability and service life of the system.

[0035] The miniature lithium manganese battery (such as CR1220) is selected as the power supply. This battery has the advantages of small size, high energy density, low self-discharge rate, etc., which can provide stable power support for the signal system and meet the needs of long-term monitoring. In practical applications, there is no need to frequently replace the battery, reducing the maintenance cost and workload, and ensuring the continuous operation of the bolt self-sensing monitoring function.

[0036] The signal system configuration in this preferred embodiment makes it applicable to a variety of complex engineering environments. Whether it is in an environment with flammable and explosive gases such as gas in underground coal mines or in areas with weak network signal coverage such as mountainous areas, the LoRa / NB-IoT wireless transmission module can select a suitable transmission method according to the actual situation to ensure the stable transmission of data, so that the bolt can play a good monitoring role in various scenarios such as mine support, tunnel engineering, and slope reinforcement, broadening the application scope of the product.

[0037] As a preferred embodiment of the present invention, refer to Figure 3 As shown, the core body 1 includes a functional section 11, a transition section 12, and a main body section 13 arranged in sequence from the bottom end to the top end. The outer diameter of the functional section 11 is greater than the outer diameter of the main body section 13, and the outer diameter of the transition section 12 gradually changes from the outer diameter of the functional section 11 to the outer diameter of the main body section 13; the length of the functional section 11 is 80 - 120 mm; the length of the transition section 12 is 30 - 50 mm, and the taper angle is less than 5°.

[0038] The outer diameter of the functional section 11 of the present invention is larger than that of the main body section 13, and the outer diameter of the transition section 12 gradually changes, which can effectively optimize the stress distribution. The increase in the outer diameter of the functional section 11 increases the local stiffness. When subjected to external forces, the stress can be concentrated in the functional section, improving the signal-to-noise ratio and protecting the main body section from excessive stress damage. The small taper angle gradual change design of the transition section 12 avoids sudden stress changes and reduces stress concentration. In the support of coal mine roadways, the stress of the surrounding rock of the roadway is complex. This design enables the bolt to bear pressure more reasonably, prevents the bolt from breaking due to stress concentration, and improves the bearing capacity and service life of the bolt.

[0039] The different designs of the functional section 11, the transition section 12, and the main body section 13, combined with the arrangement of the grating sensors 3 on the surface, can achieve more accurate strain monitoring. Due to stress concentration in the functional section 11, the strain changes significantly, which can provide key data for monitoring the deformation of the surrounding rock. The gradually changing structure of the transition section 12 makes its stress gradient change unique. By arranging the grating sensors 3 at different positions, information on the stress change trend can be obtained. The main body section 13 can reflect the overall force and deformation of the bolt. In tunnel engineering, this segmented monitoring method can comprehensively understand the working state of the bolt at different positions, timely detect abnormal deformation of the surrounding rock, and provide strong support for engineering safety early warning.

[0040] Furthermore, the optical fiber channels 5 corresponding to the transition section 12 and the main body section 13 are arranged in a straight line, and the optical fiber channel 5 corresponding to the functional section 1 is arranged in a spiral.

[0041] The outer diameter of the functional section 11 is relatively large and it is in direct contact with the surrounding rock, and the stress it receives is complex. Arranging the optical fiber channel 5 in a spiral can enable the grating sensor 3 to capture the changes in the main strain field of the surrounding rock in all directions and at multiple angles. Because the spiral layout can cover different orientations of the functional section, compared with the straight-line arrangement, it can perceive strains from all directions more comprehensively, thus providing richer and more accurate data for monitoring the deformation of the surrounding rock. For example, in the support of coal mine roadways, the functional section 11 is subjected to extrusion from different directions of the surrounding rock. The spirally arranged optical fiber channel 5 can timely monitor the subtle changes in strains in all directions and accurately reflect the deformation trend of the surrounding rock.

[0042] The transition section 12 is mainly used to reduce stress concentration. Arranging the optical fiber channel 5 in a straight line can enable the grating sensor 3 to accurately monitor the stress gradient change along the stress change direction and accurately obtain the stress change in the transition area. The main body section 13 bears the main support load. Arranging the optical fiber channel 5 in a straight line is convenient for tracking the overall deformation trend, enabling the monitoring data to intuitively reflect the force and deformation state of the main body section and providing a reliable basis for judging the overall working state of the bolt.

[0043] In addition, different areas use different fiber channel layouts to adapt to the functions and stress characteristics of each area, which helps to ensure the integrity of the optical fiber and the stability of signal transmission. In the functional section 11, the spiral layout can better adapt to the complex stress environment of the functional section and reduce the fiber breakage or signal interference caused by stress concentration; the transition section 12 and the main section 13 are arranged in a straight line. The optical fiber channel 5 has a simple and direct path, which can reduce the loss and attenuation of the signal during the transmission process and ensure that the monitoring data is accurately transmitted to the signal system.

[0044] As a preferred embodiment of the present invention, the surface of the functional segment 11 is subjected to laser microtexturing treatment and sprayed with nano-SiO 2 Modified epoxy resin: The surfaces of the transition section 12 and the main section 13 are sandblasted and coated with epoxy resin to improve the interface bonding strength.

[0045] The functional section 11 is in direct contact with the surrounding rock and is subjected to complex and harsh forces, requiring a higher interface shear strength to ensure the anchoring effect and force transmission efficiency. Therefore, a more sophisticated processing technology and high-performance nano-SiO 2 The laser microtexturing treatment on the surface of the functional segment 11 increases the surface roughness and surface area by changing the surface morphology at the microscopic level. 2 The modified epoxy resin can better adhere and penetrate, forming a stronger mechanical bite. Spraying nano-SiO 2 After the epoxy resin is modified, the interface shear strength is improved, which greatly enhances the bonding force between the stainless steel core 1 and the FRP layer 2 of the functional section 11. In geotechnical engineering, the functional section 11 is in direct contact with the surrounding rock and is subjected to large shear force and friction. The high interface shear strength can effectively prevent relative slippage between the stainless steel core and the FRP layer, ensure effective force transmission, and improve the anchoring effect of the anchor rod.

[0046] The surface of the stainless steel core of the transition section 12 and the main section 13 is sandblasted, which also increases the surface roughness and improves the adhesion conditions of the epoxy resin. After coating with epoxy resin, the interface bonding strength is improved, ensuring that the two sections of the stainless steel core and the FRP layer 2 have reliable bonding strength. When the anchor rod is under load, this good combination can enable the stainless steel core and the FRP layer 2 to work together to bear external forces and improve the overall mechanical properties of the anchor rod. The transition section 12 and the main section 13 mainly bear the support load and transfer stress. Compared with the functional section 11, the interface bonding strength requirements are slightly lower. The use of sandblasting and ordinary epoxy resin coating can not only meet its performance requirements, but also control costs, and realize the reasonable optimization of the treatment methods of different parts, so that the anchor rod has good economy while improving the overall performance.

[0047] Nano-SiO sprayed on functional segment 2The modified epoxy resin not only enhances the interfacial bonding force but also has excellent corrosion resistance. The addition of nano-SiO 2 can improve the microstructure of the epoxy resin, making it more dense, effectively blocking the intrusion of external corrosive media, and protecting the stainless steel core from corrosion. In the humid and corrosive substance-rich environment of the coal mine underground, this protection can significantly extend the service life of the stainless steel core of the functional section and ensure the long-term stable operation of the bolt.

[0048] The ordinary epoxy resin coated on the transition section 12 and the main body section 13 can also play a certain anti-corrosion role, preventing the stainless steel core from rusting to a certain extent, maintaining its mechanical properties, and thus ensuring that the bolt can normally perform the support and monitoring functions throughout the service period and reducing the risk of bolt failure caused by corrosion.

[0049] As a preferred embodiment of the present invention, as shown in Figure 1 at least one temperature compensation FBG 8 is fixed in the FRP layer 2 corresponding to the top end of the core body 1.

[0050] In practical engineering applications, temperature changes will have a significant impact on the measurement results of the FBG grating sensor 3. When the environmental temperature changes, the central wavelength of the FBG will drift, resulting in errors in the measured strain data. By setting the temperature compensation FBG 8 in the FRP layer 2 at the top end of the core body 1, the environmental temperature changes can be monitored in real time. By analyzing the wavelength change of the temperature compensation FBG, the temperature change amount can be accurately obtained, and then the data of other FBG sensors used to measure strain can be corrected, effectively eliminating the interference caused by temperature factors and improving the accuracy of bolt strain monitoring. For example, in an environment with large temperature changes such as deep mines, this temperature compensation FBG can ensure that the bolt monitoring system provides accurate strain data and provides a reliable basis for engineering safety assessment.

[0051] As a preferred embodiment of the present invention, the grating sensor 3 is adhesively fixed in the installation groove 4.

[0052] After the glue is cured, a firm bond can be formed between the grating sensor 3 and the installation groove 4, so that the grating sensor 3 is stably fixed in the installation groove 4. During the service of the bolt, whether it is affected by vibration, impact or other external forces, the adhesive fixation can effectively prevent the grating sensor 3 from shifting or falling off, ensuring that it always remains in the correct measurement position and accurately sensing the strain information of the bolt. For example, in a coal mine roadway, the bolt will be affected by external forces such as blasting vibration, and the adhesively fixed grating sensor 3 can remain stable and continuously provide reliable monitoring data.

[0053] Bonding fixation can also avoid problems such as loosening and friction that may occur due to mechanical fixation, which may lead to signal loss or interference in optical fiber transmission. Bonding fixation can make the grating sensor 3 fit tightly with the installation groove 4, reduce the influence of external factors on optical fiber signal transmission, and ensure the stability and accuracy of signal transmission. Stable signal transmission is crucial for the self-sensing monitoring function of the anchor bolt, which helps to obtain the stress state information of the anchor bolt in a timely and accurate manner and provides strong support for the safety monitoring of geotechnical engineering.

[0054] As a preferred embodiment of the present invention, the FRP layer 2 is provided with a main bearing layer, a shear-resistant layer, and a chopped fiber layer from outside to inside in sequence. The laying angle of the main bearing layer is 0°, the laying angle of the shear-resistant layer is ±45°, and the optical fiber channel 5 is located between the main bearing layer and the shear-resistant layer.

[0055] The laying angle of the main bearing layer is 0°, enabling it to effectively bear the load along the axial direction of the anchor bolt. In geotechnical engineering, the anchor bolt mainly bears axial tension and pressure. The main bearing layer laid at 0° can give full play to the high-strength characteristics of the FRP material, maximize the bearing of axial force, and ensure the support capacity of the anchor bolt. For example, in tunnel engineering, when the surrounding rock deforms and generates axial pressure on the anchor bolt, the main bearing layer can directly resist the pressure and maintain the stability of the tunnel.

[0056] The shear-resistant layer is laid at ±45°, which can effectively resist shear forces. Under actual working conditions, the anchor bolt will be subjected to shear forces from different directions. The fibers laid at ±45° can provide shear resistance in all directions. For example, in slope reinforcement engineering, the sliding of the soil mass will generate complex shear forces on the anchor bolt, and the shear-resistant layer can effectively disperse and resist these forces to prevent the anchor bolt from failing due to shear failure.

[0057] The main bearing layer and the shear-resistant layer cooperate with each other, respectively bearing axial force and shear force, realizing the optimization of mechanical properties, enabling the anchor bolt to better adapt to complex stress environments, and improving the overall bearing capacity and stability.

[0058] The optical fiber channel 5 is located between the main bearing layer and the shear-resistant layer and is well protected. The main bearing layer and the shear-resistant layer can buffer the impact and extrusion of the outside world on the optical fiber channel, reducing the risk of optical fiber damage caused by external forces. In coal mine roadways, the anchor bolt may be impacted by falling rocks. At this time, these two layers of the FRP layer can effectively protect the optical fiber channel and ensure stable signal transmission. This structural design can also prevent the surrounding medium from eroding the optical fiber. For example, in a humid geotechnical environment, the main bearing layer and the shear-resistant layer can block moisture and corrosive substances from contacting the optical fiber, extend the service life of the optical fiber, and ensure the long-term stable operation of the monitoring system.

[0059] The chopped fiber layer is located in the innermost layer of the FRP layer 2 and is in close contact with the core body, which can enhance the bonding force between the FRP layer 2 and the core body 1, enable the FRP layer 2 and the core body 1 to work better together, and improve the integrity of the overall structure of the bolt.

[0060] The combination of the three-layer structure optimizes the structural performance of the FRP layer 2, and improves the fatigue resistance and durability of the FRP layer 2. Under long-term loading, this structural design can reduce the accumulation of damage to the FRP layer 2, extend the service life of the bolt, and reduce the engineering maintenance cost.

[0061] In another embodiment, the present invention discloses a manufacturing method of a self-sensing bolt, which includes: Providing a core body blank; the core body blank includes a functional section 11, a transition section 12, and a main body section 13 arranged in sequence from the bottom end to the top end. The outer diameter of the functional section 11 is 18.4 mm, the outer diameter of the main body section 13 is 16 mm, and the outer diameter of the transition section 12 is gradually changed.

[0062] Mechanically process a plurality of installation grooves for fixing the grating sensor on the core body blank. Specifically, use a laser marking machine to mark the installation points of the FBG grating sensor 3 on the surface of the stainless steel core body blank, laser etch the installation grooves 4 on the core body blank corresponding to the installation points, use a masking technique (such as a high-temperature resistant polyimide tape) to cover the installation grooves 4 and the surrounding areas, perform surface treatment on the stainless steel core body blank, wherein the surface of the functional section 11 is subjected to laser micro-texturing treatment, the surfaces of the main body section 13 and the transition section 12 are subjected to sandblasting treatment, use ultrasonic cleaning, remove the mask, and dry with nitrogen.

[0063] Fix the grating sensor 3 in the installation groove 4. Specifically, apply a high-temperature resistant adhesive in the installation groove 4, use a vacuum fixture to fix the grating sensor 3 to the preset position in the installation groove 4, apply a pressure of 0.5 MPa, cure for 30 minutes at a temperature of 150 °C, the thickness of the adhesive layer ≤ 10 μm, and cover the surface area of the core body corresponding to the grating sensor 3 with a peelable polyether ether ketone (PEEK) protective film to prevent subsequent FRP resin from infiltrating.

[0064] The FRP layer is formed by a prepreg process, and the prepreg layer pre-buries a guide tube at a position corresponding to the installation groove, and pre-buries an inner lining channel at the position of the optical fiber channel. The transmission optical fiber of the grating sensor is guided into the inner lining channel along the guide tube through the yarn guide. Specifically, a phased progressive layering process is adopted, and all FBG grating sensors are pre-engraved on the entire optical fiber. The transmission optical fiber 31 is introduced from the surface of the core 1 into the pre-buried channel of the FRP through the guide tube, and the optical fiber is kept continuous throughout the process. After the middle layer is paved and before the outer layer is laid, the yarn guide is started to lay the transmission optical fiber. Exemplarily, the optical fiber channel 5 is located between the 0° main bearing layer and the ±45° anti-shear layer of the FRP layer 2, and a rectangular channel (axial distribution) with a size of 0.3mm×0.3mm is reserved between the FRP prepreg layers to ensure free space for the optical fiber to move, and polyetheretherketone (PEEK) film is used as the channel lining material for temporary fixation. The optical fiber channel at the top of the anchor rod extends inwardly between the FRP layers, and a cylindrical cavity matching the diameter of the quartz capillary is reserved. The quartz capillary is inserted into the cavity to embed the FBG for temperature compensation.

[0065] The core body after stacking and wrapping the prepreg layer is placed in a mold for curing to obtain a self-sensing anchor rod. Among them, the temperature during curing is set to 120~180℃, the pressure is set to 10~20MPa, and the curing time is set to 30~60min. It should be noted that since the outer diameter of the functional section 11 and the transition section 12 is different from the outer diameter of the main section 13, the thickness of the FRP layer corresponding to the functional section 11 and the transition section 12 needs to be adjusted during co-curing molding to maintain the same total outer diameter of different areas of the anchor rod.

[0066] During specific use, drilling and cleaning are carried out in the target area, anchor rods are implanted and grouting is performed, trays are installed and preload force is applied, and the signal system is connected to the pigtail at the top of the anchor rod through a spring ejector pin to activate the signal system.

[0067] The above embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitution or change made by a person skilled in the art based on the present invention is within the protection scope of the present invention.

Claims

1. A self-sensing anchor rod, characterized in that: It comprises a core body (1) and an FRP layer (2) wrapped around the surface of the core body (1); the surface of the core body (1) is provided with a plurality of mounting grooves (4) for fixing a grating sensor (3) at intervals, and the FRP layer (2) is provided with an optical fiber channel (5) through which a transmission optical fiber (31) of the grating sensor (3) passes; A guide tube (6) is fixed between the installation groove (4) and the optical fiber channel (5), and the transmission optical fiber (31) is guided into the optical fiber channel (5) through the guide tube (6), so that the transmission optical fiber (31) extends along the optical fiber channel (5) and is connected to the signal system (7) on the top nut of the core body (1).

2. The self-sensing anchor rod according to claim 1, characterized in that: The core (1) comprises a functional section (11), a transition section (12) and a main section (13) which are arranged in sequence from the bottom end to the top end, the outer diameter of the functional section (11) is greater than the outer diameter of the main section (13), and the outer diameter of the transition section (12) gradually changes from the outer diameter of the functional section (11) to the outer diameter of the main section (13); The length of the functional section (11) is 80-120 mm; The transition section (12) has a length of 30-50 mm and a taper angle of less than 5°.

3. The self-sensing anchor rod according to claim 2, characterized in that: The optical fiber channels (5) corresponding to the transition section (12) and the main section (13) are arranged in a straight line, and the optical fiber channels (5) corresponding to the functional section (11) are arranged in a spiral.

4. The self-sensing anchor rod according to claim 2, characterized in that: The surface of the functional section (11) is subjected to laser microtexturing treatment and then sprayed with nano-SiO2 modified epoxy resin; The surfaces of the transition section (12) and the main section (13) are sandblasted and then coated with epoxy resin.

5. The self-sensing anchor rod according to claim 1, characterized in that: At least one temperature compensation FBG (8) is fixed in the FRP layer (2) corresponding to the top end of the core (1).

6. The self-sensing anchor rod according to claim 1, characterized in that: The grating sensor (3) is glued and fixed in the installation groove (4).

7. The self-sensing anchor rod according to claim 1, characterized in that: The FRP layer (2) comprises a main bearing layer, an anti-shear layer, and a chopped fiber layer arranged in sequence from the outside to the inside, the main bearing layer is laid at an angle of 0°, the anti-shear layer is laid at an angle of ±45°, and the optical fiber channel (5) is located between the main bearing layer and the anti-shear layer.

8. A method for manufacturing a self-sensing anchor rod, characterized in that: include: Providing a core blank; Mechanically processing the core blank to form a plurality of mounting grooves (4) for fixing the grating sensor (3); Fixing the grating sensor (3) in the mounting groove (4); The FRP layer is formed by a prepreg process, a guide tube (6) is pre-buried in the prepreg layer at a position corresponding to the installation groove (4), an optical fiber channel (5) is pre-buried at the position of the optical fiber channel, and a transmission optical fiber (31) of the grating sensor (3) is guided along the guide tube (6) into the optical fiber channel (5) by a yarn guide; The core body after being laminated and wrapped with prepreg layers is placed in a mold for curing to obtain a self-sensing anchor rod.

9. The method for manufacturing a self-sensing anchor rod according to claim 8, characterized in that: The temperature during curing is set to 120~180℃, the pressure is set to 10~20MPa, and the curing time is set to 30~60min.

10. The method for manufacturing a self-sensing anchor rod according to claim 8, characterized in that: The grating sensor (3) is fixed in the installation groove (4) by applying adhesive glue in the installation groove (4), fixing the grating sensor (3) to a preset position in the installation groove (4) using a vacuum clamp, and curing the adhesive glue to achieve the fixing of the grating sensor (3).

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