Distributed optical fiber monitoring system for tunnels and construction method thereof

Abstract

A distributed fiber optic monitoring system for tunnels and a construction method thereof include a host computer and a first sensing fiber connected to the host computer. The first sensing fiber is disposed in the initial support of the tunnel and includes alternating circuitous segments and straight segments. The circuitous segments are used to form a first monitoring section perpendicular to the extension direction of the tunnel. The straight segments are provided with a calibration member located between the two first monitoring sections. The calibration member includes a housing, the housing at least partially located outside the initial support, and a wiring trough provided on the housing. The first sensing fiber passes through the wiring trough and abuts against the wiring trough. The present invention implements monitoring of the initial support during the tunnel construction phase by implanting sensing fibers in the initial support. At the same time, the calibration member is used to assist the host computer in accurate calibration, effectively reducing measurement errors and improving monitoring accuracy, thereby resolving the problem of the prior art lacking monitoring of the tunnel construction phase.

Description

Technical Field

[0001] The present invention relates to the field of distributed optical fiber sensing technology, and in particular to a distributed optical fiber monitoring system for tunnels and a construction method thereof. Background Art

[0002] As one of the key facilities connecting various regions, tunnels play a vital role in building a highway network in complex terrain. With the rapid advancement of road construction in mountainous areas in China, the number of tunnels has increased rapidly, and their safety issues have also attracted widespread attention.

[0003] In recent years, distributed fiber optic sensing technology has garnered significant attention. Distributed fiber optic sensing utilizes ordinary communication optical fibers, implanted within buildings in a manner similar to the nervous system. Based on the laser light emitted by the light source, it receives each echo along the optical path and measures the spatial distribution and temporal variation of information along the fiber transmission path, acquiring comprehensive information such as strain and temperature. As a passive sensor, fiber optics, when implanted within tunnel structures, effectively enables long-distance, blind-spot-free, all-encompassing monitoring from point to line / surface. It offers advantages such as low maintenance costs, strong environmental adaptability, long service life, low labor intensity, high sampling frequency, multi-parameter measurement, intrinsic safety, and 24 / 7 real-time online data collection.

[0004] Traditional distributed fiber optic tunnel monitoring systems are primarily used during tunnel maintenance. Patent CN112796781A discloses a tunnel lining health monitoring system. This system uses a combination of circumferentially and longitudinally arranged full-size ribbon-shaped distributed fiber optic sensors to monitor the tunnel lining surface and transmit data such as stress and temperature to a remote monitoring terminal. Patent CN113465636A discloses an automated distributed fiber optic laying device for tunnel secondary linings, designed to achieve circumferential fiber optic deployment along the secondary lining of a tunnel.

[0005] However, due to the complex construction environment of primary support, the sensor optical fiber is more susceptible to damage, and there is a lack of repair measures for the sensor optical fiber. Therefore, the traditional tunnel distributed optical fiber monitoring system does not deploy sensor optical fibers in the primary support, resulting in a lack of monitoring during the tunnel construction phase, which is not conducive to continuous safety monitoring and early warning throughout the tunnel life cycle. Summary of the Invention

[0006] One object of the present invention is to provide a distributed fiber optic monitoring system for tunnels. By implanting sensor fibers in the initial support to monitor the initial support during the tunnel construction phase, and using calibration components to assist the host computer in precise calibration, the system can effectively reduce measurement errors and improve monitoring accuracy, thereby solving the problem of lack of monitoring of the tunnel construction phase in the prior art.

[0007] The present invention is achieved through the following technical solutions:

[0008] A distributed fiber optic monitoring system for a tunnel includes a host computer and a first sensing fiber connected to the host computer. The first sensing fiber is arranged in the initial support of the tunnel. The first sensing fiber includes alternating circuitous segments and straight segments, wherein the circuitous segments are used to form a first monitoring section perpendicular to the extension direction of the tunnel. A calibration component located between two first monitoring sections is provided on the straight segment. The calibration component includes a shell, the shell is at least partially located outside the initial support, and a wiring groove is provided on the shell. The first sensing fiber passes through the wiring groove and abuts against the wiring groove.

[0009] In this technical solution, the distributed fiber-optic monitoring system includes a host computer located in a monitoring room. A multi-core fiber optic cable is used from the host computer to the tunnel entrance, connecting multiple sensing fibers within the same tunnel through a junction box. These sensing fibers can be installed only in the primary support for monitoring during tunnel construction, or they can be installed in both the primary support and secondary lining to enable full-cycle monitoring during tunnel construction and maintenance.

[0010] After blasting, slag removal, risk elimination, and scaffolding, the first sensing fiber is deployed in the primary branch. It extends along the tunnel's extension from one tunnel opening to the other, forming a straight segment. During this extension, the first sensing fiber enters and returns from the arch line toward the arch crown, forming a single-layer, U-shaped, circuitous section. This circuitous section, perpendicular to the extension direction of the straight segment, serves as the first monitoring section for collecting strain, temperature, and other data from the primary branch.

[0011] The first sensing optical fiber can be tied to the steel arch frame of the primary support using cable ties, steel wires, etc. The layout of the first sensing optical fiber in the primary support can be flexibly adjusted according to the different types of guide tunnels opened in the tunnel. In one or more embodiments, for the double side walls, the detour sections of the first sensing optical fiber in the left guide tunnel and the right guide tunnel extend from the arch line to the corresponding side wall and detour near the side wall, and the detour section of the first sensing optical fiber in the middle guide tunnel extends from one side wall to the other side wall and detours, and the detour sections in the left guide tunnel, the right guide tunnel, and the middle guide tunnel correspond one to one, forming multiple first monitoring sections in the tunnel. In one or more embodiments, for the middle partition wall, the detour sections of the first sensing optical fiber in the left and right guide tunnels both extend from the arch line to the corresponding side wall and detour, and the detour sections in the guide tunnels on both sides correspond one to one to form multiple first monitoring sections. The first monitoring sections may be distributed at equal or unequal intervals. In some embodiments, the first monitoring sections are distributed at equal intervals, and the distance between two adjacent first monitoring sections is 4 to 10 meters. Preferably, the distance between two adjacent first monitoring sections is 5 to 6 meters.

[0012] The resolution accuracy of distributed optical fiber for long-distance monitoring is generally around 1 meter. Due to the accumulation of various errors such as Fresnel reflection, the range on the host computer may be inconsistent with the actual range of the optical cable. In this technical solution, a calibration component is provided on the straight section. The calibration component can be located between two adjacent first monitoring sections, or a calibration component can be provided at intervals of more than two first monitoring sections. The calibration component includes a shell, which can be detachably bundled on the steel arch. The shell faces the outside of the initial support, that is, the surface of the second lining is a closed surface, which is used to ensure that the components or the first sensing optical fiber in the shell will not be solidified by the grouting during grouting. At the same time, after grouting, the height of the shell should be higher than the thickness of the initial support grouting of the tunnel, that is, the closed surface of the shell is located on the outside of the initial support, which can ensure that the position of the calibration component is clear after the initial grouting, which is convenient for the calibration process after the initial support is completed. The shell is also provided with a wiring groove, which is used for the first sensing optical fiber to enter and exit the shell. The inner diameter of the wiring groove matches the outer diameter of the first sensing optical fiber, and can fit the first sensing optical fiber tightly. Therefore, when the shell is knocked, obvious vibration can be felt on the host computer.

[0013] During the installation of the first sensing fiber, the calibration components can be tapped after installation to assist the host computer in precise calibration. This determines the circumferential implantation length of the first sensing fiber along the tunnel surrounding rock and the corresponding first monitoring section stake number, achieving controllable cumulative errors and improving the accuracy of the first sensing fiber monitoring. After the first sensing fiber is deployed, grouting is performed to complete the first sensing fiber deployment in the primary support. During the subsequent secondary lining construction phase, the calibration components can be used again to confirm whether the first sensing fiber has been damaged during construction. The range of each calibration component can be reviewed, significantly improving the accuracy of the first sensing fiber monitoring during the tunnel construction phase and ensuring safety during the tunnel construction phase.

[0014] As a preferred configuration for the calibration component of the present invention, a hanging rod is provided within the housing, and the first sensing fiber is wound around the hanging rod to form a coiled cable. In this technical solution, the calibration component not only assists the host computer in calibration and verification during the construction phase, thereby improving monitoring accuracy during the construction phase, but also enables rapid reconnection of the first sensing fiber if damage is detected to the first sensing fiber or the first monitoring section.

[0015] Specifically, one or more hanging rods are provided inside the shell. After the first sensing optical fiber enters the shell from a wiring trough, it is wound on the hanging rod to form a cable coil, and finally leaves the shell through another wiring trough. The hanging rod can be fixedly installed inside the shell, or it can be movably arranged inside the shell. The closed surface of the shell can ensure that the cable coil does not come into contact with the slurry and solidify during the spraying process. During construction, when the first sensing optical fiber breaks, the range is observed and the breakpoint is identified through the upper computer interface, and two adjacent calibration pieces corresponding to the range are found in the tunnel. Subsequently, the two calibration pieces are cut open, the cable coil wound on the hanging rod is pulled out and connected externally, and then the entire cable is sealed into the tunnel wall during the second spraying.

[0016] In this technical solution, by adding a hanging rod for winding the cable in the shell, when the first sensing optical fiber is damaged during the initial support process in a complex construction environment, the breakpoint can be quickly located and the first sensing optical fiber can be quickly repaired without opening the initial support surface and re-implanting the first sensing optical fiber, which greatly reduces the tunnel construction cost and improves the overall tunnel construction efficiency.

[0017] There are various ways to arrange the hanging rod. In some embodiments, only one hanging rod is provided. In one or more embodiments, there may be at least two hanging rods, and the at least two hanging rods may be arranged in a variety of shapes, such as a straight line, a triangle, or a polygon. The coiled cable is wound around the at least two hanging rods to form a straight line, a triangle, a polygon, or the like.

[0018] Furthermore, the coiled cable is in the shape of a quadrilateral, and is further formed with a middle section connecting diagonal corners of the quadrilateral, and the midpoint of the middle section is the midpoint of the first sensing optical fiber located in the housing.

[0019] In this technical solution, the cable is wound around four hanging rods located at the vertices of a quadrilateral, and the cable is formed into a quadrilateral as a whole. A construction method is used to set the middle section of the cable to be collinear with the diagonal of the quadrilateral, and the midpoint of the middle section is the midpoint of the total length of the first sensing optical fiber in the shell that enters the shell from one wiring trough and leaves the shell from another wiring trough. By setting the middle section to coincide with the diagonal of the quadrilateral, when repairing the first sensing optical fiber, the cable can be disconnected from the middle by cutting the middle section after cutting the shell of the calibration component. This not only effectively improves the splicing efficiency, but also, because the cable is disconnected from the middle section, two first sensing optical fibers of substantially equal length can be quickly pulled out. When splicing the cables in two adjacent calibration components, the first sensing optical fibers of equal length in the two calibration components are conducive to the splicing work.

[0020] Furthermore, a slide groove is provided in the shell, and the hanging rod can move along the slide groove, and the central axes of two adjacent slide grooves are perpendicular to each other.

[0021] In the present technical solution, the hanging rod in the shell is movably installed on the inner side of the closed surface of the shell. Specifically, a slide groove for the movement of the hanging rod is provided in the shell. The slide groove corresponds to the hanging rod one by one. For example, when the four hanging rods are located at the four vertices of a rectangle, a total of four slide grooves are provided in the shell. The central axes of two adjacent slide grooves are perpendicular to each other, and the central axes of the two slide grooves on the diagonals are parallel to each other. Therefore, when the four hanging rods are moved by the force of the cable, they will move from the initial quadrilateral, such as a rectangle, to other regular or irregular quadrilaterals. During the movement, the circumference of the cable coiled around the four hanging rods remains basically unchanged, and the hanging rods are easier to move. Through this setting method, when the first sensing optical fiber is laid out or connected, or when the first sensing optical fiber exerts a force on the hanging rod due to other processes, the hanging rod can produce a certain degree of displacement to reduce the reaction force exerted by the hanging rod on the first sensing optical fiber. This not only strengthens the protection of the first sensing optical fiber during the construction phase, but also the bending point of the first sensing optical fiber affected by the hanging rod can change with the movement of the hanging rod, avoiding some points on the first sensing optical fiber being in the bending position for a long time, thereby improving the accuracy of the first sensing optical fiber monitoring to a certain extent.

[0022] Furthermore, two elastic members are provided in the slide groove and are symmetrically arranged with respect to the hanging rod. One end of the elastic member is connected to the end of the slide groove, and the other end of the elastic member is connected to the hanging rod.

[0023] In this technical solution, two elastic members are installed in the chute, symmetrically arranged about the hanging rod. For example, one end of the first elastic member is connected to the first end of the chute and the other end is connected to the hanging rod; one end of the second elastic member is connected to the second end of the chute and the other end is connected to the hanging rod. In the initial state, under the combined action of the two elastic members, the hanging rod is located in the middle of the chute. After the cable exerts a force on the hanging rod, after the force is adjusted, or after the force is eliminated, the hanging rod can adaptively adjust its position in the chute under the action of the elastic members, further enhancing the protection of the cable and increasing the frequency of changes in the bending point.

[0024] Furthermore, a spring connected to the hanging rod and an elastic sleeve filled with a water-retaining agent are provided in the slide groove, and a limit plate located above the elastic sleeve is provided on the slide groove; when the water-retaining agent has not expanded, the hanging rod abuts against the limit plate under the action of the spring; when the water-retaining agent absorbs water and expands, the hanging rod moves toward the spring.

[0025] In the present technical solution, of the two elastic parts provided in the slide, one is a spring and the other is an elastic sleeve filled with a water-retaining agent. The elastic sleeve has a certain deformation ability and can be made of materials such as silicone and rubber. A mesh is provided on the elastic sleeve to facilitate the entry and exit of water vapor in the shell into the elastic sleeve. A water-retaining agent is provided in the elastic sleeve, and the filled water-retaining agent can be a chemical water-retaining agent such as polyacrylamide, a mineral water-retaining agent, or a combination of a chemical water-retaining agent and a mineral water-retaining agent. A limiting plate is also provided on the slide. On the one hand, the limiting plate is used to limit the expansion direction of the elastic sleeve so that the elastic sleeve that expands due to water absorption by the water-retaining agent can expand toward the hanging rod. On the other hand, the limiting plate is used to limit the initial position of the hanging rod in the slide, allowing the spring to always be in a compressed state.

[0026] Tunnel construction environments are complex, and during the maintenance phase, the air humidity inside the tunnel varies with the day and night, and with the seasons. Therefore, taking advantage of these humidity differences within the tunnel, the water-retaining agent expands after absorbing water and compresses the hanging rod, causing it to move despite the spring force. As the humidity drops, the agent releases some moisture into the dry air and contracts, causing the hanging rod to abut against the stop plate under the elastic force, returning it to its initial position.

[0027] In this technical solution, the position of the hanging rod is actively adjusted by using the ambient humidity, which can not only further enhance the protection of the cable coil and increase the frequency of change of the bending point, but more importantly, the water-retaining agent can balance the ambient humidity inside the shell, so that the humidity inside and outside the shell remains relatively stable, and it is not easy to generate water vapor and ice on the shell, which effectively improves the vibration conduction effect of the shell, thereby improving the monitoring accuracy and precision of the first sensing optical fiber.

[0028] Furthermore, the retaining plate is provided with a plurality of second through-holes that connect the chute to the interior of the housing. The housing is also provided with a third through-hole that connects the elastic sleeve to the exterior of the housing. The second and third through-holes are positioned oppositely on the upper and lower sides of the elastic sleeve to enhance air flow inside and outside the housing, increasing the contact time and area between the water-retaining agent and the air, further enhancing the water absorption and release efficiency of the water-retaining agent.

[0029] As another preferred arrangement of the calibration member in the present invention, an anchor rod is connected to the shell, and the anchor rod is at least partially located outside the secondary lining of the tunnel.

[0030] In this technical solution, calibration or verification is still required during the maintenance phase for long-term tunnels to ensure the long-term reliability of the optical cable monitoring data. The housing is also equipped with anchor rods, which are detachably or non-detachably mounted on the closed surface of the housing and at least partially located outside the tunnel secondary lining. During the maintenance phase, amplitude fluctuations can be detected on the host computer by tapping the anchor rods, leveraging the excellent metal conductivity.

[0031] Furthermore, it also includes a second sensing optical fiber connected to the host computer, and the second sensing optical fiber is arranged in the secondary lining of the tunnel. The second sensing optical fiber includes a number of second monitoring sections perpendicular to the extension direction of the tunnel. In order to realize the optical cable monitoring in the maintenance stage, a second sensing optical fiber is also implanted in the secondary lining. The second sensing optical fiber is implanted in the secondary lining after the reinforcement is tied and before the trolley is in place. The second sensing optical fiber also includes a straight section and a circuitous section, and the circuitous section is used to form a second monitoring section. After the tunnel surface is sprayed and solidified, the optical cable used for detection is integrated with the entire steel arch frame, leaving no room for free movement, and the strain of this optical cable replaces the strain of the corresponding implanted structural part.

[0032] Another object of the present invention is to provide a construction method for a distributed optical fiber monitoring system for tunnels, which sets a number of calibration parts on the sensing optical fiber implanted in the primary branch. Calibration can be achieved by knocking the calibration parts, thereby making the accumulated error of the sensing optical fiber in the primary branch controllable.

[0033] Specifically, the construction method includes the following steps:

[0034] The first sensing optical fiber connected to the host computer is tied to the steel arch frame of the initial support to form alternating circuitous segments and straight segments;

[0035] A calibration member is provided on the straight segment and is located between the two first monitoring sections, wherein the wiring groove of the calibration member abuts against the straight segment;

[0036] After completing the initial support, knock each calibration piece to carry out calibration processing.

[0037] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0038] 1. The present invention implements monitoring of the initial support during the tunnel construction phase by implanting sensing fibers in the initial support. Calibration components are used to assist the host computer in precise calibration, making cumulative errors controllable and improving the accuracy of the first sensing fiber monitoring. After the first sensing fiber is deployed, the calibration components can be used again during the subsequent secondary lining construction phase to confirm whether the first sensing fiber is damaged during construction. The range of each calibration component is reviewed, thereby significantly improving the accuracy of the first sensing fiber monitoring during the tunnel construction phase and ensuring safety during the tunnel construction phase.

[0039] 2. By adding a hanging rod for winding the cable in the housing, the present invention enables rapid location and repair of the first sensing fiber if it is damaged during the initial support process in a complex construction environment. This eliminates the need to open the initial support surface and re-implant the first sensing fiber, significantly reducing tunnel construction costs and improving overall tunnel construction efficiency.

[0040] 3. The present invention provides anchor rods on the closed surface of the shell, so that during the maintenance phase, the amplitude fluctuation can be detected on the host computer by knocking on the anchor rods and utilizing the excellent metal conductivity of metal;

[0041] 4. The present invention arranges the middle section of the coiled cable to coincide with the diagonal of the quadrilateral. When repairing the first sensing optical fiber, the coiled cable can be disconnected from the middle by cutting open the housing of the calibration component and then severing the middle section. This not only effectively improves the splicing efficiency, but also, because the coiled cable is disconnected from the middle section, two first sensing optical fibers of substantially equal length can be quickly pulled out. When splicing the coiled cables of two adjacent calibration components, the first sensing optical fibers of equal length in the two calibration components facilitate the splicing operation.

[0042] 5. The present invention movably arranges the hanging rod in the housing so that when the first sensing optical fiber is laid out or connected, or when the first sensing optical fiber exerts a force on the hanging rod due to other processes, the hanging rod can produce a certain range of displacement to reduce the reaction force exerted by the hanging rod on the first sensing optical fiber. This not only strengthens the protection of the first sensing optical fiber during the construction phase, but also the bending point of the first sensing optical fiber affected by the hanging rod can change with the movement of the hanging rod, avoiding some points on the first sensing optical fiber being at a bend for a long time, thereby improving the accuracy of the first sensing optical fiber monitoring to a certain extent.

[0043] 6. The calibration component of the present invention can actively adjust the position of the hanging rod by utilizing the ambient humidity, which can not only further enhance the protection of the cable coil and increase the frequency of change of the bending point, but more importantly, the water-retaining agent can balance the ambient humidity inside the shell, so that the humidity inside and outside the shell remains relatively stable, and thus it is not easy to generate water vapor and ice on the shell, effectively improving the vibration conduction effect of the shell, thereby improving the monitoring accuracy and precision of the first sensing optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0045] Figure 1 Schematic diagram of the layout of the first sensing optical fiber installed in the primary branch of the double-side wall guide hole in a specific embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the layout of the first sensing optical fiber installed in the primary branch of the middle partition wall guide hole in a specific embodiment of the present invention;

[0047] Figure 3 This is a structural diagram of a calibration component in a specific embodiment of the present invention;

[0048] Figure 4 This is a schematic diagram of the internal structure of a calibration component in a specific embodiment of the present invention;

[0049] Figure 5 This is the vibration curve displayed on the host computer after the calibration component is struck in a specific embodiment of the present invention.

[0050] Figure 6 This is a schematic structural diagram of another calibration component in a specific embodiment of the present invention;

[0051] Figure 7 This is a schematic diagram of another calibration member in a specific embodiment of the present invention when the water-retaining agent has not expanded / has not pushed the hanging rod to move;

[0052] Figure 8 This is a schematic diagram of another calibration member in a specific embodiment of the present invention when the water-retaining agent expands and pushes the hanging rod to move;

[0053] Figure 9 This is a schematic diagram of the structure inside the chute in a specific embodiment of the present invention;

[0054] Figure 10 Schematic diagram of the layout of the second sensing optical fiber installed in the second lining in a specific embodiment of the present invention;

[0055] Figure 11 This is a construction method of a distributed optical fiber monitoring system in a specific embodiment of the present invention.

[0056] Markings and corresponding parts names in the accompanying drawings:

[0057] 1- host computer, 2- first sensing fiber, 21- straight segment, 22- circuitous segment, 3- calibration component, 31- housing, 32- mounting plate, 33- first through hole, 34- wiring trough, 35- hanging rod, 36- cable, 37- middle segment, 38- anchor rod, 39- screw hole, 310- slide groove, 311- spring, 312- limit plate, 313- second through hole, 314- water retaining agent, 315- elastic sleeve, 316- third through hole, 4- second sensing fiber;

[0058] 101-first left guide hole, 102-middle guide hole, 103-first right guide hole, 201-second left guide hole, 202-second right guide hole. DETAILED DESCRIPTION

[0059] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0060] In the description of the present invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present invention.

[0061] Example 1:

[0062] like Figures 1 to 4 The distributed fiber optic monitoring system for a tunnel shown includes a host computer 1 and a first sensing fiber 2 connected to the host computer 1. The first sensing fiber 2 is arranged in the initial support of the tunnel. The first sensing fiber 2 includes alternating detour sections 22 and straight sections 21, wherein the detour sections 22 are used to form a first monitoring section perpendicular to the extension direction of the tunnel. The straight section 21 is provided with a calibration component 3 located between the two first monitoring sections. The calibration component 3 includes a shell 31, and the shell 31 is at least partially located on the outside of the initial support. A wiring groove 34 is provided on the shell 31, and the first sensing fiber 2 passes through the wiring groove 34 and abuts against the wiring groove 34.

[0063] like Figure 1 As shown, for the laying method of the first sensing optical fiber on both side walls, the detour sections of the first sensing optical fiber in the first left guide tunnel 101 and the first right guide tunnel 103 extend from the arch line to the corresponding side wall and detour near the side wall, and the detour section of the first sensing optical fiber in the middle guide tunnel 102 extends from one side wall to the other side wall and detours, and the detour sections in the left guide tunnel, the right guide tunnel and the middle guide tunnel correspond to each other one by one, forming multiple first monitoring sections in the tunnel.

[0064] like Figure 2 As shown, for the laying method of the first sensing optical fiber in the middle partition wall, the detour sections of the first sensing optical fiber in the left and right guide holes extend from the arch line to the corresponding side walls and detour, and the detour sections in the guide holes on both sides correspond to each other to form multiple first monitoring sections.

[0065] In some preferred embodiments, the first monitoring sections are distributed at equal intervals, and the distance between two adjacent first monitoring sections is 5 to 6 meters.

[0066] In one or more embodiments, in order to reduce background noise interference caused by environmental noise such as precipitation, vehicle traffic, mechanical construction, etc., the first sensing optical fiber is buried at a depth of 10 to 15 cm, preferably, at a depth of 12 cm.

[0067] In some preferred embodiments, Figure 3 As shown, a mounting plate 32 is provided on the housing 31 , and a first through hole 33 on the mounting plate is used for a steel wire or a cable tie to pass through so as to fix the calibration piece on the steel arch.

[0068] Since metal conducts vibration better than nonlinear materials such as concrete mortar, when the calibration piece is struck with a tool, there will be an obvious bulge on the upper computer, such as Figure 5 As shown in the figure, this value is also called the maximum value point. When another adjacent calibration component is struck, another maximum value point will be generated on the host computer several dozen meters away. Therefore, each calibration component can be struck separately to calibrate and verify the range of each calibration component, ultimately achieving controllable monitoring cumulative error.

[0069] In some preferred embodiments, a second sensing optical fiber 4 connected to the host computer 1 is also included. Figure 10 As shown, the second sensing optical fiber 4 is arranged in the secondary lining of the tunnel, and the second sensing optical fiber 4 includes a plurality of second monitoring sections perpendicular to the extending direction of the tunnel.

[0070] In one or more embodiments, the second monitoring sections are distributed at equal intervals, and the distance between two adjacent second monitoring sections is 25 to 30 meters.

[0071] In one or more embodiments, the second sensing optical fiber is embedded at a depth of 10 to 15 cm, preferably, at a depth of 12 cm.

[0072] In some embodiments, reserved sections are provided at both ends of the sensing fiber entering and exiting the tunnel. These reserved sections are coiled for 10 to 30 meters and then cemented with concrete to blend into the tunnel wall. Simultaneously, the signals collected by these reserved sections are shielded from the host computer. This means that these reserved sections of sensing fiber are used only for signal transmission and not for vibration detection. This is because, due to their high sensitivity, when the sensing fiber is outside the solidified tunnel wall and deformed by vibration, the host computer's amplitude interface is extremely sensitive, primarily manifesting in a high noise floor amplitude. Because the fiber's inherent vibration transmission is extremely strong, approximately ten meters, to avoid vibration transmission due to non-wall deformation and to provide greater redundancy in end-to-end data measurement, this technical solution employs a method of coiling the ends of the sensing fiber and shielding the signals of some sections of the fiber at both ends.

[0073] Example 2:

[0074] In this embodiment, the calibration component can not only assist the host computer in calibration and review during the construction phase to improve the monitoring accuracy during the construction phase, but also realize the rapid connection of the first sensing optical fiber after detecting partial damage to the first sensing optical fiber or the first monitoring section. Figure 4 The figure only schematically shows the winding method of the cable, but does not show the first sensing optical fiber entering and exiting the housing through the wiring groove. Figure 3 and Figure 4 As shown, based on Example 1, a hanging rod 35 is provided in the housing 31 , and the first sensing optical fiber 2 is wound around the hanging rod 35 to form a coiled cable 36 .

[0075] During construction, if the first sensing fiber breaks, the host computer interface monitors the measuring range, identifies the breakpoint, and locates two adjacent calibration components within the tunnel that correspond to the measuring range. The components are then cut, the coiled cable wrapped around the rod is pulled out, and connected externally. The entire component is then sealed into the tunnel wall during the secondary grouting process.

[0076] In some preferred embodiments, the coiled cable 36 is quadrilateral and further includes a middle section 37 connecting the diagonal corners of the quadrilateral. The midpoint of the middle section 37 corresponds to the midpoint of the first sensing optical fiber 2 located within the housing 31. When repairing the first sensing optical fiber, the coiled cable can be disconnected from the middle by cutting open the housing of the calibration component and then severing the middle section. This not only effectively improves splicing efficiency, but also, because the coiled cable is disconnected from the middle section, two first sensing optical fibers of substantially equal length can be quickly pulled out. When splicing the coiled cables of two adjacent calibration components, the equal lengths of the first sensing optical fibers in both components facilitate the splicing operation.

[0077] In one or more embodiments, the coiled cable is rectangular, square, or diamond-shaped.

[0078] Example 3:

[0079] Based on the above embodiments, Figure 6 As shown, the shell 31 is connected to an anchor rod 38, and the anchor rod 38 is at least partially located outside the secondary lining of the tunnel.

[0080] Tunnels in long-term use still require calibration or review during the maintenance phase to ensure the long-term reliability of the optical cable monitoring data. The housing is also equipped with anchor rods, which are detachably or permanently attached to the closed surface of the housing and at least partially located outside the tunnel secondary lining. During the maintenance phase, amplitude fluctuations can be detected on the host computer by tapping the anchor rods, leveraging the excellent metal conductivity.

[0081] In one or more embodiments, a calibration member with an anchor rod is used every 5 to 10 calibration members.

[0082] Example 4:

[0083] Based on the above embodiments, Figures 7 and 8 As shown, a slide groove 310 is provided in the shell 31, and the hanging rod 35 can move along the slide groove 310. The central axes of two adjacent slide grooves 310 are perpendicular to each other. Two elastic members symmetrically arranged about the hanging rod 35 are provided in the slide groove 310, and one end of the elastic member is connected to the end of the slide groove 310, and the other end of the elastic member is connected to the hanging rod 35.

[0084] In the initial state, under the joint action of the two elastic parts, the hanging rod is located in the middle of the slide groove. After the cable generates a force on the hanging rod, the force is adjusted, or the force is eliminated, the hanging rod can adaptively adjust its position in the slide groove under the action of the elastic parts, further enhancing the protection of the cable and increasing the frequency of changes in the bending point.

[0085] In one or more embodiments, the elastic member is a spring, rubber, or other elastic mechanism or component with reset capability.

[0086] In some preferred embodiments, in order to improve the stability of the hanging rod movement, a card slot and a card block matching the card slot can be set at the bottom of the slide. For example, if the card slot is a T-shaped card slot, the card block is a T-shaped card block that can move along the card slot.

[0087] Example 5:

[0088] Based on the above embodiments, Figures 7 to 9 As shown, a spring 311 connected to the hanging rod 35 and an elastic sleeve 315 filled with a water-retaining agent 314 are provided in the slide groove 310, and a limit plate 312 located above the elastic sleeve 315 is provided on the slide groove 310; when the water-retaining agent 314 is not expanded, the hanging rod 35 abuts against the limit plate 312 under the action of the spring 311; when the water-retaining agent 314 absorbs water and expands, the hanging rod 35 moves toward the spring 311.

[0089] The tunnel construction environment is complex, and during the maintenance phase, the air humidity in the tunnel will also vary with the time of day and season. Therefore, taking advantage of the difference in humidity in the tunnel, such as Figure 8 As shown in the figure, the water retaining agent can expand and squeeze the hanging rod after absorbing water, so that the hanging rod overcomes the force of the spring and moves. As the humidity drops, the water retaining agent releases a certain amount of water into the dry air and shrinks. Figure 7 As shown, the hanging rod abuts against the limit plate under the action of elastic force, and the hanging rod returns to its initial position.

[0090] like Figure 9As shown, the limiting plate 312 is provided with a plurality of second through-holes 313, which connect the chute 310 with the interior of the housing 31. The housing 31 is also provided with third through-holes 316, which connect the elastic sleeve 315 with the exterior of the housing 31. The second and third through-holes are arranged on opposite sides of the elastic sleeve to enhance the flow of air inside and outside the housing, increase the contact time and area between the water-retaining agent and the air, and further improve the water absorption and release efficiency of the water-retaining agent.

[0091] Example 6:

[0092] like Figure 11 As shown, a construction method for constructing the distributed optical fiber monitoring system for a tunnel in any of the aforementioned embodiments specifically comprises the following steps:

[0093] The first sensing optical fiber 2 connected to the host computer 1 is tied to the steel arch frame of the initial support to form alternating circuitous sections 22 and straight sections 21;

[0094] A calibration member 3 is provided on the straight section 21 and is located between the two first monitoring sections. The wiring groove 34 of the calibration member 3 abuts against the straight section 21.

[0095] After completing the initial support, knock each calibration piece 3 to perform calibration processing.

[0096] In some embodiments, a multi-core optical cable is used from the monitoring room to the tunnel entrance to connect multiple sensing optical fibers in the same tunnel through a junction box. The sensing optical fiber reels are placed on cable racks, away from the tunnel face for easy retraction. The sensing optical fibers, including the incoming and outgoing lines, are fixed with expansion hooks, and visual signs are hung. The sensing optical fibers are protected with calibration parts and fixed with expansion bolts and steel wires. The outgoing line of the sensing optical fiber is protected with a hydraulic pipe, and the protection length is adjusted according to the actual situation of the tunnel and should not be less than 20 meters. The sensing optical fibers of the incoming and outgoing lines are directly laid on the inner steel mesh of the primary support steel arch frame by tying with nylon ties, and are circulated in sequence. After the first sensing optical fiber is implanted and installed, a vibration tool is used to calibrate the length of the optical cable implanted along the circumference of the tunnel surrounding rock and the corresponding section pile number.

[0097] The terms "first," "second," etc. (e.g., first left guide hole, second left guide hole, etc.) used herein are merely used to distinguish corresponding components for clarity of description and are not intended to limit any order or emphasize importance. Furthermore, the term "connected" used herein, unless otherwise specified, may refer to a direct connection or an indirect connection via other components.

[0098] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A distributed optical fiber monitoring system for a tunnel, comprising a host computer (1) and a first sensing optical fiber (2) connected to the host computer (1), characterized in that: The first sensing optical fiber (2) is arranged in the initial support of the tunnel. The first sensing optical fiber (2) includes a circuitous section (22) and a straight section (21) that are alternately arranged. The circuitous section (22) is used to form a first monitoring section perpendicular to the extension direction of the tunnel. The straight section (21) is provided with a calibration member (3) located between the two first monitoring sections. The calibration member (3) includes a housing (31). The housing (31) is at least partially located outside the initial support. A wiring groove (34) is provided on the housing (31). The first sensing optical fiber (2) passes through the wiring groove (34) and abuts against the wiring groove (34). In the process of laying out the first sensing optical fiber (2), the calibration components (3) can be knocked after each calibration component (3) is installed to assist the host computer (1) in accurate calibration, thereby determining the length of the first sensing optical fiber (2) implanted along the circumference of the tunnel surrounding rock and the corresponding stake number of the first monitoring section; During the second lining construction phase, the calibration piece (3) is used to confirm whether the first sensing optical fiber (2) is damaged during the construction process, and the measuring range of each calibration piece (3) is reviewed.

2. The distributed optical fiber monitoring system for tunnels according to claim 1, characterized in that: A hanging rod (35) is provided in the housing (31), and the first sensing optical fiber (2) is wound around the hanging rod (35) to form a coiled cable (36).

3. The distributed optical fiber monitoring system for tunnels according to claim 2, characterized in that: The coiled cable (36) is a quadrilateral, and is further formed with a middle section (37) connecting the diagonal corners of the quadrilateral. The midpoint of the middle section (37) is the midpoint of the first sensing optical fiber (2) located in the housing (31).

4. The distributed optical fiber monitoring system for tunnels according to claim 3, characterized in that: A sliding groove (310) is provided in the housing (31), and the hanging rod (35) can move along the sliding groove (310), and the central axes of two adjacent sliding grooves (310) are perpendicular to each other.

5. The distributed optical fiber monitoring system for tunnels according to claim 4, characterized in that: Two elastic members are arranged in the slide groove (310) and are symmetrically arranged with respect to the hanging rod (35). One end of the elastic member is connected to the end of the slide groove (310), and the other end of the elastic member is connected to the hanging rod (35).

6. The distributed optical fiber monitoring system for tunnels according to claim 4, characterized in that: The chute (310) is provided with a spring (311) connected to the hanging rod (35) and an elastic sleeve (315) filled with a water-retaining agent (314); the chute (310) is provided with a limiting plate (312) located above the elastic sleeve (315); When the water-retaining agent (314) is not expanded, the hanging rod (35) abuts against the limiting plate (312) under the action of the spring (311); When the water-retaining agent (314) absorbs water and expands, the hanging rod (35) moves toward the spring (311).

7. The distributed optical fiber monitoring system for tunnels according to claim 6, characterized in that: The limiting plate (312) is provided with a plurality of second through holes (313), the second through holes (313) communicating with the slide groove (310) and the interior of the housing (31). The housing (31) is also provided with a third through hole (316), the third through hole (316) communicating with the elastic sleeve (315) and the exterior of the housing (31).

8. The distributed optical fiber monitoring system for tunnels according to claim 2, characterized in that: An anchor rod (38) is connected to the shell (31), and the anchor rod (38) is at least partially located outside the secondary lining of the tunnel.

9. The distributed optical fiber monitoring system for tunnels according to claim 1, characterized in that: It also includes a second sensing optical fiber (4) connected to the host computer (1), the second sensing optical fiber (4) is arranged in the secondary lining of the tunnel, and the second sensing optical fiber (4) includes a plurality of second monitoring sections perpendicular to the extension direction of the tunnel.

10. A construction method for constructing a distributed optical fiber monitoring system for a tunnel according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: The first sensing optical fiber (2) connected to the host computer (1) is tied to the steel arch frame of the initial support to form a circuitous section (22) and a straight section (21) arranged alternately; A calibration member (3) is provided on the straight section (21) and is located between the two first monitoring sections, and a wiring groove (34) of the calibration member (3) abuts against the straight section (21); After the initial support is completed, each calibration piece (3) is struck to perform calibration processing.

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