Tunnel longitudinal deformation self-sensing system and method based on intelligent bolts

Abstract

The invention discloses a tunnel longitudinal deformation self-sensing system and method based on an intelligent bolt, the system comprises the intelligent bolt and a computer terminal, the intelligent bolt comprises a bolt main body connected to a tunnel segment; the fiber bragg grating sensor is installed in the bolt body and used for generating corresponding wavelength change based on deformation of the tunnel segment and outputting a wavelength change optical signal; the integrated circuit board is used for receiving the wavelength change optical signal, calculating the bolt axial force of the bolt body based on the wavelength change, and further calculating the longitudinal curvature of the tunnel; and the threshold indicator lamp is used for controlling the light emitting color of the threshold indicator lamp according to the range value of the longitudinal curvature of the tunnel. Compared with the prior art, the method has the following beneficial effects that the stress deformation of the bolt is monitored in real time, the relationship between the stress deformation of the bolt and the longitudinal deformation of the tunnel is established, and finally the tunnel deformation condition is visually reflected through the intelligent bolt with the threshold indicator lamp, so that the problem of poor deformation perceptibility in current tunnel monitoring can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of shield tunnel deformation monitoring, and in particular to a tunnel longitudinal deformation self-sensing system and method based on intelligent bolts. Background Art

[0002] In recent years, subways have gradually become popular in cities. However, due to the influence of the surrounding geological environment, adjacent construction, and vehicle dynamics, the tunnel segment structure and its connection will be deformed and damaged to varying degrees. When the longitudinal deformation of the tunnel is too large, it will not only cause the segment concrete to crack, but also cause the tunnel annular joint to open and misalign, resulting in water leakage and other defects. Therefore, monitoring the longitudinal deformation of the tunnel can avoid major accidents and provide a decision-making basis for the maintenance and management of the tunnel. Existing monitoring methods, whether traditional monitoring methods or automated non-contact monitoring technologies developed in recent years, mostly require processing and analysis of the monitoring data of tunnel deformation, and cannot intuitively perceive the deformation of the tunnel.

[0003] Based on the above situation, it is necessary to design a tunnel longitudinal deformation self-sensing system to solve the above technical problems. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a self-sensing system and method for tunnel longitudinal deformation based on smart bolts, which monitors the stress deformation of the bolts in real time, establishes the relationship between the stress deformation of the bolts and the longitudinal deformation of the tunnel, and finally intuitively reflects the deformation of the tunnel through smart bolts with threshold indicator lights. This can solve the problem of poor deformation perception in current tunnel monitoring, thereby solving at least one technical problem involved in the background technology.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] The embodiment of the present application provides a tunnel longitudinal deformation self-sensing system based on smart bolts, including smart bolts and a computer terminal connected to the smart bolts for communication, wherein the smart bolts include:

[0007] A bolt body connected to the tunnel segment;

[0008] A fiber grating sensor installed in the bolt body, used to generate a corresponding wavelength change based on the deformation of the tunnel segment and output a wavelength change optical signal;

[0009] An integrated circuit board, which is used to receive the wavelength change optical signal, and calculate the bolt axial force of the bolt body based on the wavelength change, and then calculate the longitudinal curvature of the tunnel;

[0010] A threshold indicator light is used to control the luminous color of the threshold indicator light according to the range value of the longitudinal curvature of the tunnel.

[0011] As a preferred improvement of the present application, the fiber grating sensor includes a fiber strain sensor for detecting the strain of the bolt body and a fiber temperature sensor for detecting the temperature of the bolt body.

[0012] As a preferred improvement of the present application, the integrated circuit board includes a photoelectric converter for converting the wavelength-changing optical signal transmitted by the fiber grating sensor into an electrical signal, an analog-to-digital converter for converting the electrical signal into a digital signal, a storage device for storing and recording the initial preload data of the bolt body, a data processing module for calculating the longitudinal curvature of the tunnel based on the digital signal, a data wireless transmission module for transmitting various data to a remote computer terminal, and a power supply module for power supply.

[0013] As a preferred improvement of the present application, the integrated circuit board further comprises a microcontroller for controlling the lighting of the threshold indicator light according to the calculation result transmitted by the data processing module.

[0014] The embodiment of the present application also provides a method for self-sensing longitudinal deformation of a tunnel based on smart bolts according to the system, comprising the following steps:

[0015] Step 1: collecting wavelength-changing optical signals generated by deformation of tunnel segments;

[0016] Step 2, receiving the wavelength change optical signal, and calculating the bolt axial force according to the wavelength change of the optical fiber sensor;

[0017] Step 3, calculating the annular gap opening amount according to the bolt axial force;

[0018] Step 4, calculating the joint angle according to the annular seam opening;

[0019] Step 5, calculating the longitudinal curvature radius of the tunnel according to the joint angle;

[0020] Step six, dividing the range value of the longitudinal curvature radius of the tunnel according to the critical state of the tunnel, and determining the color of the corresponding threshold indicator light.

[0021] As a preferred improvement of the present application, in step 1, before collecting the wavelength-changed optical signal, the method further includes:

[0022] It is necessary to conduct calibration tests on the optical fiber strain sensor and optical fiber temperature sensor to obtain the strain and temperature sensitivity coefficients. The calculation formula is as follows:

[0023] Δλ1=α ε ε+α1ΔT

[0024] Δλ2=α2ΔT

[0025]

[0026] Where ε is the bolt strain; α and α1 are the strain and temperature sensitivity coefficients of the optical fiber strain sensor, respectively; α2 is the sensitivity coefficient of the optical fiber temperature sensor; Δλ1 and Δλ2 are the optical fiber wavelength change values ​​in the optical fiber strain sensor and the optical fiber temperature sensor, respectively; ΔT is the temperature change; P is the axial tension on the bolt; E b is the elastic modulus of the bolt; A b is the effective area of ​​the bolt.

[0027] As a preferred improvement of the present application, in step three, the calculating of the annular gap opening amount according to the bolt axial force includes:

[0028] Assuming that the maximum opening between the rings is the tensile deformation of the outermost bolt, the calculation formula is as follows:

[0029]

[0030] In the formula, δ max is the maximum opening between the rings; k j1 is the linear stiffness coefficient of a single bolt.

[0031] As a preferred improvement of the present application, in step 4, the calculating of the joint angle according to the annular gap opening amount includes:

[0032] Assuming that the lateral deformation of the tunnel and the action range of the bolts are ignored, the relationship between the annular gap opening and the joint angle is obtained based on the deformation coordination equation and the force balance equation. The calculation formula is as follows:

[0033] Deformation coordination equation:

[0034]

[0035] The force balance equation is:

[0036] E c ε t t=k j δ max

[0037] Bolt equivalent stiffness coefficient:

[0038]

[0039] Neutral axis position:

[0040]

[0041] The relationship between the annular gap opening and the joint angle:

[0042]

[0043] In the formula, ε t l is the tensile strain at the edge of the tensile zone of the segment annular joint concrete; s Segment ring width; r is segment radius; is the angle of the neutral axis; θ is the joint rotation angle; E c is the elastic modulus of concrete; t is the thickness of the pipe segment; k j is the equivalent stiffness coefficient of the bolt; n is the number of annular bolts; l b A is the bolt action length; c is the cross-sectional area of ​​the tunnel.

[0044] As a preferred improvement of the present application, in step 5, the calculating of the longitudinal curvature radius of the tunnel according to the joint angle includes:

[0045] The longitudinal curvature radius of the tunnel is calculated using the following formula:

[0046]

[0047] Where ρ is the longitudinal curvature radius of the tunnel.

[0048] As a preferred improvement of the present application, step six specifically includes:

[0049] The critical state of the tunnel is divided into the following ways: critical curvature radius ρ0, the minimum curvature radius of the subway tunnel caused by external factors as specified in the specification; curvature radius ρ1 corresponding to the outermost bolt reaching the elastic limit state; curvature radius ρ2 when the ring gap opening reaches 3mm when the segment resists 0.3MPa water pressure; curvature radius ρ3 when the ring gap sealing gasket is watertight and the ring gap opening is 6mm; curvature radius ρ4 corresponding to the outermost bolt reaching the failure stress state;

[0050] When the longitudinal curvature radius ρ≥ρ0 of the tunnel, the indicator light emits blue light, and the tunnel is in a safe state; when the longitudinal curvature radius ρ1≤ρ<ρ0 of the tunnel, the indicator light emits cyan light, and there are certain safety hazards in the tunnel; when the longitudinal curvature radius ρ2≤ρ<ρ1 of the tunnel, the indicator light emits green light, and the bolts reach the elastic limit state; when the longitudinal curvature radius ρ3≤ρ<ρ2 of the tunnel, the indicator light emits yellow light, and there is a high probability of leakage at the annular joint of the tunnel, and the corresponding section needs to be inspected; when the longitudinal curvature radius ρ4≤ρ<ρ3 of the tunnel, the indicator light emits purple light, the annular joint sealing and water-stopping measures fail, and the tunnel will have serious water seepage, and remedial measures need to be taken for the corresponding section; when the longitudinal curvature radius ρ<ρ4 of the tunnel, the indicator light emits red light, and the bolts reach the destructive stress state, and there is a risk of breaking and damage at any time.

[0051] The beneficial effects of this application are as follows:

[0052] (1) Based on the remote real-time monitoring of bolt stress and tunnel deformation, it realizes the intuitive perception of tunnel longitudinal deformation monitoring;

[0053] (2) By using smart bolts with threshold indicator lights, the indicator lights can be used to intuitively reflect the longitudinal deformation of the tunnel;

[0054] (3) A method for calculating the curvature radius of the tunnel using the bolt axial force and a method for judging the internal conditions of the tunnel by dividing the critical state of the tunnel are proposed. The judgment and calculation results are reasonable and effective and can be used for deformation monitoring in the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0056] Figure 1 A schematic diagram of the structure of the smart bolt provided in the embodiment of the present application;

[0057] Figure 2 A block diagram of the integrated circuit structure provided in the embodiment of the present application;

[0058] Figure 3 A schematic diagram of the structure of an embedded optical fiber sensor provided in an embodiment of the present application;

[0059] Figure 4 A schematic diagram of the joint angle calculation provided in the embodiment of the present application;

[0060] Figure 5 A schematic diagram of the installation of the smart bolt provided in an embodiment of the present application.

[0061] In the figure, 1. bolt body; 2. optical fiber strain sensor; 3. optical fiber temperature sensor; 4. integrated circuit board; 41. photoelectric converter; 42. analog-to-digital converter; 43. storage; 44. data processing module; 45. wireless data transmission module; 46. power module; 47. microcontroller; 5. threshold indicator light; 6. fixed connection point; 7. steel sleeve; 8. optical fiber; 100. smart bolt. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0063] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0064] See also Figure 1 As shown, an embodiment of the present application provides a tunnel longitudinal deformation self-sensing system based on smart bolts, including a smart bolt 100 and a computer terminal connected to the smart bolt 100 for communication. The smart bolt 100 includes a bolt body 1, a fiber grating sensor, an integrated circuit board 4 and a threshold indicator light 5.

[0065] The bolt body 1 is connected to the tunnel segment and can reflect the longitudinal deformation of the tunnel through its own stress deformation.

[0066] The fiber grating sensor is installed in the bolt body 1, and is used to generate corresponding wavelength changes based on the deformation of the tunnel segment and output wavelength change optical signals.

[0067] Specifically, the fiber grating sensor includes a fiber strain sensor 2 for detecting the strain of the bolt body 1 and a fiber temperature sensor 3 for detecting the temperature of the bolt body. That is, the fiber strain sensor 2 can generate a wavelength optical signal reflecting the strain of the bolt body 1, and the fiber temperature sensor 3 can generate a wavelength optical signal reflecting the temperature of the bolt body 1.

[0068] The integrated circuit board 4 is used to receive the wavelength change optical signal, and calculate the bolt axial force of the bolt body 1 based on the wavelength change, and further calculate the longitudinal curvature of the tunnel.

[0069] Recombination Figure 2As shown, the integrated circuit board 4 includes a photoelectric converter 41 for converting the wavelength-changing optical signal transmitted by the fiber grating sensor into an electrical signal, an analog-to-digital converter 42 for converting the electrical signal into a digital signal, a storage 43 for storing and recording the initial preload data of the bolt body, a data processing module 44 for calculating the longitudinal curvature of the tunnel according to the digital signal, a data wireless transmission module 45 for transmitting each data to a remote computer terminal, a power supply module 46 for powering, and a microcontroller 47 for controlling the threshold indicator light 5 to emit light according to the calculation result transmitted by the data processing module 44.

[0070] The threshold indicator light 5 is used to control the light color of the threshold indicator light 5 according to the range value of the longitudinal curvature of the tunnel.

[0071] The threshold indicator light 5 adopts an RGB LED lamp, and adopts a specific dimming method to make it emit red, green, blue, yellow (red and green), purple (red and blue), and cyan (blue and green).

[0072] The specific arrangement of the fiber grating sensor, the integrated circuit board 4 and the threshold indicator light 5 in the smart bolt is as follows:

[0073] First, a drilling machine or other equipment is used to form a center hole of a certain depth at the center of the bolt body 1. The center hole extends from the head of the bolt body 1 to the non-threaded part of the screw. The optical fiber strain sensor 2 and the optical fiber temperature sensor 3 are packaged with a steel sleeve and buried at a certain interval at the bottom of the center hole, and fixed to the side of the center hole with epoxy resin; then the shielded wires of the two sensors are connected to the integrated circuit board 4, and the integrated circuit board 4 is connected to the threshold indicator light 5; finally, the integrated circuit board 4 and the threshold indicator light 5 are fixed with epoxy resin.

[0074] Further, combined with Figure 3 As shown, since a fiber grating sensor is used, in order to protect the optical fiber 8, it is encapsulated in a steel sleeve 7, and its two ends are connected to the fixed points 6, and the fixed points 6 are connected to the steel sleeve 7 so that their deformation is consistent with that of the steel sleeve 7.

[0075] The embodiment of the present application also provides a method for self-sensing longitudinal deformation of a tunnel based on smart bolts according to the system, comprising the following steps:

[0076] Step 1: collecting wavelength-changing optical signals generated by deformation of tunnel segments;

[0077] Step 2, receiving the wavelength change optical signal, and calculating the bolt axial force according to the wavelength change of the optical fiber sensor;

[0078] Step 3, calculating the annular gap opening amount according to the bolt axial force;

[0079] Step 4, calculating the joint angle according to the annular seam opening;

[0080] Step 5, calculating the longitudinal curvature radius of the tunnel according to the joint angle;

[0081] Step six, dividing the range value of the longitudinal curvature radius of the tunnel according to the critical state of the tunnel, and determining the color of the corresponding threshold indicator light.

[0082] In step 1, before collecting the wavelength-changed optical signal, the method further includes:

[0083] It is necessary to conduct calibration tests on the optical fiber strain sensor and optical fiber temperature sensor to obtain the strain and temperature sensitivity coefficients. The calculation formula is as follows:

[0084] Δλ1=α ε ε+α1ΔT

[0085] Δλ2=α2ΔT

[0086]

[0087] Where ε is the bolt strain; α and α1 are the strain and temperature sensitivity coefficients of the optical fiber strain sensor, respectively; α2 is the sensitivity coefficient of the optical fiber temperature sensor; Δλ1 and Δλ2 are the optical fiber wavelength change values ​​in the optical fiber strain sensor and the optical fiber temperature sensor, respectively; ΔT is the temperature change; P is the axial tension on the bolt; E b is the elastic modulus of the bolt; A b is the effective area of ​​the bolt.

[0088] In step three, combine Figure 4 As shown, the calculation of the annular gap opening amount according to the bolt axial force includes:

[0089] Assuming that the maximum opening between the rings is the tensile deformation of the outermost bolt, the calculation formula is as follows:

[0090]

[0091] In the formula, δ max is the maximum opening between the rings; k j1 is the linear stiffness coefficient of a single bolt.

[0092] In step 4, the calculation of the joint angle according to the annular gap opening includes:

[0093] Assuming that the lateral deformation of the tunnel and the action range of the bolts are ignored, the relationship between the annular gap opening and the joint angle is obtained based on the deformation coordination equation and the force balance equation. The calculation formula is as follows:

[0094] Deformation coordination equation:

[0095]

[0096] The force balance equation is:

[0097] E c ε t t=k j δ max

[0098] Bolt equivalent stiffness coefficient:

[0099]

[0100] Neutral axis position:

[0101]

[0102] The relationship between the annular gap opening and the joint angle:

[0103]

[0104] In the formula, ε t l is the tensile strain at the edge of the tensile zone of the segment annular joint concrete; s Segment ring width; r is segment radius; is the angle of the neutral axis; θ is the joint rotation angle; E c is the elastic modulus of concrete; t is the thickness of the pipe segment; k j is the equivalent stiffness coefficient of the bolt; n is the number of annular bolts; l b A is the bolt action length; c is the cross-sectional area of ​​the tunnel.

[0105] In step 5, the calculating of the longitudinal curvature radius of the tunnel according to the joint angle includes:

[0106] The longitudinal curvature radius of the tunnel is calculated using the following formula:

[0107]

[0108] Where ρ is the longitudinal curvature radius of the tunnel.

[0109] Step 6 specifically includes:

[0110] The critical state of the tunnel is divided into the following ways: critical curvature radius ρ0, the minimum curvature radius of the subway tunnel caused by external factors as specified in the specification; curvature radius ρ1 corresponding to the outermost bolt reaching the elastic limit state; curvature radius ρ2 when the ring gap opening reaches 3mm when the segment resists 0.3MPa water pressure; curvature radius ρ3 when the ring gap sealing gasket is watertight and the ring gap opening is 6mm; curvature radius ρ4 corresponding to the outermost bolt reaching the failure stress state;

[0111] When the longitudinal curvature radius of the tunnel ρ≥ρ0, the indicator light emits blue light, and the tunnel is in a safe state; when the longitudinal curvature radius of the tunnel ρ1≤ρ<ρ0, the indicator light emits cyan light, and there are certain safety hazards in the tunnel; when the longitudinal curvature radius of the tunnel ρ2≤ρ<ρ1, the indicator light emits green light, and the bolts reach the elastic limit state; when the longitudinal curvature radius of the tunnel ρ3≤ρ<ρ2, the indicator light emits yellow light, and there is a high probability of leakage at the annular joint of the tunnel, and the corresponding section needs to be inspected; when the longitudinal curvature radius of the tunnel ρ4≤ρ<ρ3, the indicator light emits purple light, the annular joint sealing and water-stopping measures fail, and the tunnel will have serious water seepage, and remedial measures need to be taken for the corresponding section; when the longitudinal curvature radius of the tunnel ρ<ρ4, the indicator light emits red light, and the bolts reach the destructive stress state, and there is a risk of breaking and damage at any time.

[0112] like Figure 5 As shown in the installation diagram of the smart bolt 100, after installation, the threshold indicator light 5 is exposed to the outside, and the on-site management personnel can judge the deformation and leakage of the tunnel and the stress condition of the bolt according to the color of the indicator light. When observing, it is necessary to focus on the smart bolt 100 on the outermost side of the section.

[0113] The beneficial effects of this application are as follows:

[0114] (1) Based on the remote real-time monitoring of bolt stress and tunnel deformation, it realizes the intuitive perception of tunnel longitudinal deformation monitoring;

[0115] (2) By using smart bolts with threshold indicator lights, the indicator lights can be used to intuitively reflect the longitudinal deformation of the tunnel;

[0116] (3) A method for calculating the curvature radius of the tunnel using the bolt axial force and a method for judging the internal conditions of the tunnel by dividing the critical state of the tunnel are proposed. The judgment and calculation results are reasonable and effective and can be used for deformation monitoring in the tunnel.

[0117] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0118] In addition, it should be noted that the scope of the methods and systems in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. In addition, features described with reference to certain examples may be combined in other examples.

[0119] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A tunnel longitudinal deformation self-sensing system based on smart bolts, characterized in that: It includes a smart bolt and a computer terminal connected to the smart bolt for communication, and the smart bolt includes: A bolt body connected to the tunnel segment; A fiber grating sensor installed in the bolt body, used to generate a corresponding wavelength change based on the deformation of the tunnel segment and output a wavelength change optical signal; An integrated circuit board, which is used to receive the wavelength change optical signal, and calculate the bolt axial force of the bolt body based on the wavelength change, and then calculate the longitudinal curvature of the tunnel; A threshold indicator light is used to control the luminous color of the threshold indicator light according to the range value of the longitudinal curvature of the tunnel.

2. The system according to claim 1, characterized in that The fiber grating sensor comprises a fiber strain sensor for detecting the bolt body strain and a fiber temperature sensor for detecting the bolt body temperature.

3. The system according to claim 1 or 2, characterized in that: The integrated circuit board includes a photoelectric converter for converting the wavelength-changing optical signal transmitted by the fiber grating sensor into an electrical signal, an analog-to-digital converter for converting the electrical signal into a digital signal, a storage device for storing and recording the initial preload data of the bolt body, a data processing module for calculating the longitudinal curvature of the tunnel according to the digital signal, a data wireless transmission module for transmitting various data to a remote computer terminal, and a power supply module for power supply.

4. The system according to claim 3, characterized in that The integrated circuit board also includes a microcontroller for controlling the threshold indicator light to emit light according to the calculation result transmitted by the data processing module.

5. A method for self-sensing longitudinal deformation of a tunnel based on smart bolts according to the system of any one of claims 1 to 4, characterized in that: The steps include: Step 1: collecting wavelength-changing optical signals generated by deformation of tunnel segments; Step 2, receiving the wavelength change optical signal, and calculating the bolt axial force according to the wavelength change of the optical fiber sensor; Step 3, calculating the annular gap opening amount according to the bolt axial force; Step 4, calculating the joint angle according to the annular seam opening; Step 5, calculating the longitudinal curvature radius of the tunnel according to the joint angle; Step six, dividing the range value of the longitudinal curvature radius of the tunnel according to the critical state of the tunnel, and determining the color of the corresponding threshold indicator light.

6. The method according to claim 5, characterized in that In step 1, before collecting the wavelength-changed optical signal, the method further includes: It is necessary to conduct calibration tests on the optical fiber strain sensor and optical fiber temperature sensor to obtain the strain and temperature sensitivity coefficients. The calculation formula is as follows: Δλ1=a ε e+a1ΔT Δλ2=α2ΔT Where ε is the bolt strain; α ε , α1 are the strain and temperature sensitivity coefficients of the optical fiber strain sensor respectively; α2 is the sensitivity coefficient of the optical fiber temperature sensor; Δλ1 and Δλ2 are the optical fiber wavelength change values ​​in the optical fiber strain sensor and the optical fiber temperature sensor respectively; ΔT is the temperature change; P is the axial tension on the bolt; E b is the elastic modulus of the bolt; A b is the effective area of ​​the bolt.

7. The method according to claim 6, characterized in that In step three, the annular gap opening amount is calculated according to the bolt axial force, including: Assuming that the maximum opening between the rings is the tensile deformation of the outermost bolt, the calculation formula is as follows: In the formula, δ max is the maximum opening between the rings; k j1 is the linear stiffness coefficient of a single bolt.

8. The method according to claim 7, characterized in that In step 4, the calculation of the joint angle according to the annular gap opening includes: Assuming that the lateral deformation of the tunnel and the action range of the bolts are ignored, the relationship between the annular gap opening and the joint angle is obtained based on the deformation coordination equation and the force balance equation. The calculation formula is as follows: Deformation coordination equation: The force balance equation is: E c e t t=k j d max Bolt equivalent stiffness coefficient: Neutral axis position: The relationship between the annular gap opening and the joint angle: In the formula, ε t l is the tensile strain at the edge of the tensile zone of the segment annular joint concrete; s Segment ring width; r is segment radius; is the angle of the neutral axis; θ is the joint rotation angle; E c is the elastic modulus of concrete; t is the thickness of the pipe segment; k j is the equivalent stiffness coefficient of the bolt; n is the number of annular bolts; l b A is the bolt action length; c is the cross-sectional area of ​​the tunnel.

9. The method according to claim 8, characterized in that In step 5, the calculating of the longitudinal curvature radius of the tunnel according to the joint angle includes: The longitudinal curvature radius of the tunnel is calculated using the following formula: Where ρ is the longitudinal curvature radius of the tunnel.

10. The method according to claim 9, characterized in that Step 6 specifically includes: The critical state of the tunnel is divided into the following ways: critical curvature radius ρ0, the minimum curvature radius of the subway tunnel caused by external factors as specified in the specification; curvature radius ρ1 corresponding to the outermost bolt reaching the elastic limit state; curvature radius ρ2 when the ring gap opening reaches 3mm when the segment resists 0.3MPa water pressure; curvature radius ρ3 when the ring gap sealing gasket is watertight and the ring gap opening is 6mm; curvature radius ρ4 corresponding to the outermost bolt reaching the failure stress state; When the longitudinal curvature radius ρ≥ρ0 of the tunnel, the indicator light emits blue light, and the tunnel is in a safe state; when the longitudinal curvature radius ρ1≤ρ<ρ0 of the tunnel, the indicator light emits cyan light, and there are certain safety hazards in the tunnel; when the longitudinal curvature radius ρ2≤ρ<ρ1 of the tunnel, the indicator light emits green light, and the bolts reach the elastic limit state; when the longitudinal curvature radius ρ3≤ρ<ρ2 of the tunnel, the indicator light emits yellow light, and there is a high probability of leakage at the annular joint of the tunnel, and the corresponding section needs to be inspected; when the longitudinal curvature radius ρ4≤ρ<ρ3 of the tunnel, the indicator light emits purple light, the annular joint sealing and water-stopping measures fail, and the tunnel will have serious water seepage, and remedial measures need to be taken for the corresponding section; when the longitudinal curvature radius ρ<ρ4 of the tunnel, the indicator light emits red light, and the bolts reach the destructive stress state, and there is a risk of breaking and damage at any time.

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