A method and device for monitoring tunnel surrounding rock settlement and convergence

Abstract

This application discloses a method and device for monitoring tunnel surrounding rock settlement and convergence. The method includes the following steps: a fiber optic sensor chain is installed circumferentially along the tunnel; a tunable laser emits a continuously swept-frequency light beam, which is then split into two parts by coupler A; one part of the light enters coupler D, where the signal is transmitted to a first photodetector; the other part enters coupler B, where, after being split by coupler B, one part enters the polarization controller of the reference optical path, while the other part enters the measurement optical path of the fiber optic sensor chain; the optical signals in the reference optical path and the measurement optical path undergo beat frequency interference and are received by a balanced photodetector; and data from the first photodetector and the balanced photodetector are collected. The fiber optic sensor chain is installed circumferentially along the tunnel, and tunnel deformation is monitored using an OFDR distributed fiber optic sensing system. The acquired distributed strain data is used to reconstruct the overall deformation of the protective material, providing an effective means for large-scale measurement of deformation fields such as tunnel faces.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel engineering, and in particular to a method and device for monitoring the settlement and convergence of tunnel surrounding rock. Background Art

[0002] Currently, commonly used tunnel settlement and convergence measurement methods include total station measurement, convergence meter method, level measurement method, microwave radar, and ultrasonic detection technology. The total station method uses a total station to perform three-dimensional coordinate measurements to obtain tunnel settlement and convergence data, offering high measurement efficiency. The convergence meter method uses a convergence meter to measure the convergence of the surrounding rock around the tunnel, which is simple to operate. The level measurement method uses a precision level and level rod to observe settlement, offering high measurement accuracy. Microwave radar can penetrate the tunnel surrounding rock and detect deformation at depth. Ultrasonic detection technology can detect subtle changes such as cracks within the rock.

[0003] However, different methods for monitoring tunnel settlement convergence have their own advantages and disadvantages. While highly efficient, total station measurement is susceptible to external factors such as wind and vibration from objects passing through the tunnel, resulting in poor data stability. The convergence meter method is simple to operate but can damage the tunnel and produces poor data stability. Furthermore, this method can only measure convergence around the tunnel perimeter and cannot fully reflect the overall deformation of the tunnel. The leveling method offers high accuracy but is complex to operate and has a limited monitoring range. Microwave radar imaging has relatively low resolution, limited ability to interpret complex structures, and is affected by geological media. Ultrasonic testing technology has limited application in deep complex structures and requires a clear sound wave propagation path. Therefore, the selection of a monitoring method requires comprehensive consideration based on the specific project conditions and requirements.

[0004] To this end, the present application provides a solution based on optical frequency domain reflectometry (OFDR technology), thereby providing an effective means for large-scale measurement of deformation fields such as tunnel faces, so as to solve the defect that most tunnel monitoring and measurement methods in related technologies can only obtain the deformation of local points in the tunnel and are difficult to monitor the deformation of the entire tunnel. Summary of the Invention

[0005] The present application aims to address at least one of the technical problems existing in the prior art. To this end, the present application proposes a method for monitoring the settlement and convergence of tunnel surrounding rock. By acquiring distributed strain data, the overall deformation of the protective material can be reconstructed, providing an effective means for large-scale measurement of deformation fields, such as at the tunnel face.

[0006] The present application also proposes a device for monitoring the settlement and convergence of tunnel surrounding rock.

[0007] The present application also proposes a storage medium, in which at least one instruction is stored. The instruction is loaded and executed by a processor to implement the operations performed by the above-mentioned method for monitoring tunnel surrounding rock settlement and convergence.

[0008] According to the first embodiment of the present application, the method for monitoring tunnel surrounding rock settlement and convergence includes the following steps:

[0009] The optical fiber sensing chain is installed on the inner side of the tunnel section along the tunnel ring and fits tightly with the inner surface of the tunnel;

[0010] The tunable laser emits a continuous wavelength swept light which is then divided into two parts by coupler A;

[0011] A portion of the light enters the auxiliary interferometer connected to the coupler D and performs beat frequency interference, generating an external clock signal which is then transmitted to the first photodetector for photoelectric conversion.

[0012] The other part enters the main interferometer connected to coupler B. After being split by coupler B, part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, while the other part of the light enters the measurement optical path of the fiber optic sensor chain through the three-port circulator.

[0013] The optical signals in the reference optical path and the measurement optical path undergo beat frequency interference and are processed by a balanced photodetector consisting of two photodetectors respectively;

[0014] The data from the first photodetector and the balanced photodetector are collected by a data acquisition card, and the collected data are transmitted to a data processing platform for demodulation algorithm processing and display.

[0015] According to the method for monitoring the settlement and convergence of tunnel surrounding rock according to the first aspect of the embodiment of the present application, there are at least the following beneficial effects: by installing the optical fiber sensing chain along the tunnel ring, more complete and comprehensive measurement data can be obtained, and the OFDR distributed optical fiber sensing system is used to monitor the deformation of the tunnel, which not only has high measurement accuracy and a wide measurement range, but also has excellent anti-interference ability. The optical fiber sensing chain can easily sense the strain along the length of the optical fiber. The overall deformation of the protective material can be reconstructed through the obtained distributed strain data, providing an effective means for large-scale measurement of deformation fields such as tunnel faces.

[0016] According to the method for monitoring the settlement and convergence of tunnel surrounding rock as described in the embodiment of the first aspect of the present application, inclination sensors are installed on the top of the inner surface of the tunnel, the arch shoulders on both sides, and the arch waist areas on both sides to capture the inclination data at a 45-degree position on the top of the tunnel, and accordingly correct the cumulative error generated by the optical fiber sensing chain.

[0017] According to the method for monitoring tunnel surrounding rock settlement and convergence described in the embodiment of the first aspect of the present application, the value measured by the inclination sensor is set to an initial value, and then the correction coefficient k is used to complete the correction. The specific method is:

[0018] First, the real-time tilt angle θ1 is obtained from the above-mentioned tilt sensor. The product of the strain data obtained from the sensor chain and θ1 is used as the reconstructed tilt angle θ2. The objective function and the global optimal solution are determined based on the particle swarm algorithm to determine the k value.

[0019] Assign velocity and position attributes to several particles, and each particle determines the optimal solution within the set k value range. Finally, the optimal solutions of all particles are shared to determine the global optimal solution k.

[0020] Take the inclination angle of the two sensors at the spandrel as θ 11 and θ 12 , the reconstructed tilt angle is θ 21 and θ 22 , and the sensor’s position at this time is (x i ,y i ), let (x i-1 ,y i-1 ) and (x i+1 ,y i+1 ) are the coordinates of two adjacent points, then θ 21 and θ 22 for:

[0021]

[0022] Where m and n are the serial numbers of the tilt sensor;

[0023] The objective function is:

[0024]

[0025] After the cumulative error correction is performed, in order to measure the correction effect, the error between the reconstructed deformation of the sensing chain and the actual deformation is expressed as the mean absolute error of the X coordinate and the Y coordinate:

[0026]

[0027] Where X1 and X2 are the actual coordinates of the measuring points, Y1 and Y2 are the reconstructed coordinates, and n is the number of measured points.

[0028] According to the method for monitoring tunnel surrounding rock settlement and convergence described in the embodiment of the first aspect of the present application, the steps of installing a fiber optic sensor chain in the tunnel profile include:

[0029] Before starting work, the installation location must be determined and the appropriate point must be selected according to monitoring requirements;

[0030] Install fixed brackets or erect frames according to the points to support the installation of the fiber optic sensor chain;

[0031] Lay and arrange the fiber optic sensing chain according to a predetermined outline or path.

[0032] According to the method for monitoring tunnel surrounding rock settlement and convergence described in the embodiment of the first aspect of the present application, the method for arranging the optical fiber sensing chain includes: using a fixing clamp and / or adhesive to fix the optical fiber sensing chain on a fixed bracket or an erection frame.

[0033] According to the method for monitoring tunnel surrounding rock settlement and convergence described in the embodiment of the first aspect of the present application, the preparation process of the optical fiber sensor chain includes:

[0034] Along the central axis of the flexible protective material, the optical fiber and the protective material are bonded together and initially fixed;

[0035] Mix epoxy resin and curing agent in a 1:1 ratio to ensure tight coupling between the optical fiber and the protective material, and lead out the optical fiber at both ends of the protective material.

[0036] According to the method for monitoring tunnel surrounding rock settlement and convergence described in the embodiment of the first aspect of the present application, the protective material is a carbon fiber protective material.

[0037] According to the second embodiment of the present application, a device for monitoring tunnel surrounding rock settlement and convergence includes:

[0038] The optical fiber sensor chain is installed on the inner side of the tunnel section along the tunnel ring and fits tightly with the inner surface of the tunnel;

[0039] Tunable laser, used to emit continuously swept light of wavelength;

[0040] A coupler A, configured to receive the frequency-sweep light of the tunable laser and split it into two parts;

[0041] A coupler D receives a portion of the light emitted from the coupler A, generates an external clock signal through beat frequency interference, and transmits the signal to a first photodetector for photoelectric conversion;

[0042] a coupler B, receiving another portion of light emitted from the coupler A and dividing the light into two portions;

[0043] a polarization controller, receiving a portion of the light emitted by the coupler B, wherein the polarization controller is used to form a reference light path and exists as a local oscillator light;

[0044] a circulator, receiving another portion of the light emitted by the coupler B and transmitting the light to the measurement optical path of the optical fiber sensing chain through the three ports of the circulator;

[0045] A balanced photodetector, used to receive the optical signals after beat frequency interference in the reference optical path and the measurement optical path respectively;

[0046] The data acquisition card is used to receive information from each of the photoelectric detectors and transmit it to the data processing platform.

[0047] According to the device for monitoring the settlement and convergence of tunnel surrounding rock as described in the embodiment of the second aspect of the present application, it also includes inclination sensors arranged on the top of the inner surface of the tunnel, the arch shoulders on both sides, and the arch waist areas on both sides. The data of the inclination sensors are transmitted to the data processing platform and used to perform in-situ correction of the annular deformation field of the optical fiber sensor chain.

[0048] The storage medium according to the third aspect embodiment of the present application includes: at least one instruction is stored in the storage medium, and the instruction is loaded and executed by the processor to implement the operations performed by the method for monitoring tunnel surrounding rock settlement and convergence as described in the first aspect embodiment of the present application.

[0049] It is not difficult to understand that the device for monitoring tunnel surrounding rock settlement and convergence in the second aspect embodiment of the present application and the storage medium in the third aspect embodiment of the present application both have the technical effects of the method for monitoring tunnel surrounding rock settlement and convergence in the first aspect embodiment, and therefore will not be repeated.

[0050] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present application is further described below with reference to the accompanying drawings and embodiments;

[0052] Figure 1 This is a schematic diagram of the installation of the optical fiber sensing chain according to an embodiment of the present application;

[0053] Figure 2 Schematic diagram of the composition of the OFDR optical fiber sensing system in an embodiment of the present application;

[0054] Figure 3 Schematic diagram of the optical fiber sensing chain structure in an embodiment of the present application;

[0055] Figure 4 This is a data collection flow chart in the embodiment of this application.

[0056] Reference numerals:

[0057] 100. Fiber optic sensing chain; 110. Sensing optical fiber; 120. Carbon fiber plate;

[0058] 200. Tilt sensor. DETAILED DESCRIPTION

[0059] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0060] In the description of this application, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application.

[0061] In the description of this application, "several" means one or more, "more" means at least two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The terms "first" and "second" are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or as implicitly specifying the number or order of the technical features.

[0062] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense. Technical personnel in the relevant technical field can reasonably determine the specific meanings of the above terms in this application after combining the specific content of the technical solution.

[0063] The method for monitoring the settlement and convergence of tunnel surrounding rock in the embodiment of the present application is applied to the monitoring and evaluation of the safe and stable state of tunnel engineering. The specific technology for monitoring the settlement and convergence of tunnel surrounding rock belongs to the field of safety monitoring and detection technology. Among them, the present application is based on optical frequency domain reflectometry (OFDR technology). This fiber optic sensing technology has the characteristics of high spatial resolution, high sensitivity and low optical power requirements, and is particularly suitable for fields such as large-scale structural health monitoring. The fiber optic sensing chain 100 technology is easy to stick or build into protective materials, and it is easy to sense the strain along the length of the optical fiber. The overall deformation of the protective material can be reconstructed by the acquired distributed strain data, which provides an effective means for large-scale measurement of deformation fields such as tunnel faces.

[0064] Understandably, existing tunnel monitoring and measurement methods can only detect deformation at local points in the tunnel, making it difficult to monitor deformation across the entire tunnel. Therefore, a fiber optic sensor chain 100, constructed using optical frequency domain reflectometry and protected by carbon fiber composite materials, was developed and fabricated, specifically targeting tunnel face settlement and convergence.

[0065] Reference Figures 1 to 4 The method for monitoring tunnel surrounding rock settlement and convergence according to the first embodiment of the present application comprises the following steps:

[0066] The optical fiber sensing chain 100 is installed on the inner side of the tunnel section along the tunnel ring and fits tightly with the inner surface of the tunnel;

[0067] The tunable laser emits a continuous wavelength swept light which is then divided into two parts by coupler A;

[0068] A portion of the light enters the auxiliary interferometer connected to the coupler D and performs beat frequency interference, generating an external clock signal which is then transmitted to the first photodetector for photoelectric conversion.

[0069] The other part enters the main interferometer connected to coupler B. After being split by coupler B, part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, while the other part of the light enters the measurement optical path of the fiber optic sensor chain 100 through the three-port circulator.

[0070] The optical signals in the reference optical path and the measurement optical path undergo beat frequency interference and are processed by a balanced photodetector consisting of two photodetectors respectively;

[0071] The data from the first photodetector and the balanced photodetector are collected by a data acquisition card, and the collected data are transmitted to a data processing platform for demodulation algorithm processing and display.

[0072] As can be understood, the fiber optic sensing chain 100 accurately captures strain data through advanced optical frequency domain reflectometry distributed fiber optic sensing technology. This technology not only offers high measurement accuracy and a wide measurement range, but also possesses excellent anti-interference capabilities, making it particularly suitable for the precise measurement of strain and temperature changes.

[0073] In some embodiments, the fiber optic sensing chain 100 is primarily used for tunnel deformation monitoring. Fiber optic deformation sensors are meticulously installed on the tunnel's longitudinal floor, monitoring tunnel deformation in real time and providing critical data support for subsequent deformation field analysis, reconstruction, and adjustments.

[0074] In some embodiments, the OFDR distributed fiber optic sensing system is composed of a hardware system and a software system, wherein the hardware system includes a light source, a detector, a data acquisition card, etc. The laser is the key to achieving the high spatial resolution of the OFDR system, and the SpitLight 7000 pulsed laser can be selected. The photoelectric conversion efficiency is a very important parameter of the photodetector. The higher the photoelectric conversion efficiency, the better the detector performance. The APD210 series avalanche photodetector can be selected. The data acquisition card is a bridge connecting the analog signal and the computer, and the USB-6351 data acquisition card is selected. Under the LABVIEW platform, a software system was designed and constructed, and its core components include the laser frequency scanning control program, the data capture program, and the signal analysis program.

[0075] In some embodiments, the laser frequency scanning control program is responsible for setting and adjusting the laser scanning frequency range; the data capture program is responsible for triggering the data acquisition card to perform sample acquisition at uniform frequency intervals; and the signal analysis program is focused on analyzing the strain and temperature distribution along the optical fiber path from the collected data.

[0076] In some embodiments, referring to Figure 1 A portion of the light enters the auxiliary interferometer connected to the coupler D and the beat frequency interference is achieved through the delay fiber and coupler E. The beat frequency interference of the light signals in the reference optical path and the measurement optical path is achieved through coupler C. The data acquisition process can be referred to Figure 4 , which will not be described in detail here.

[0077] Reference Figures 1 to 4 The method for monitoring tunnel surrounding rock settlement and convergence in the first embodiment of the present application obtains more complete and comprehensive measurement data by installing the optical fiber sensor chain 100 along the tunnel circumference. The OFDR distributed optical fiber sensing system is used to monitor tunnel deformation. The method not only has high measurement accuracy and a wide measurement range, but also has excellent anti-interference ability. The optical fiber sensor chain 100 can easily sense the strain along the length of the optical fiber. The overall deformation of the protective material can be reconstructed through the obtained distributed strain data, providing an effective means for large-scale measurement of deformation fields such as tunnel faces.

[0078] In some embodiments of the present application, inclination sensors 200 are installed on the top, spandrels on both sides, and waist areas on both sides of the inner surface of the tunnel to capture inclination data at a 45-degree angle on the top of the tunnel, and to correct the accumulated error generated by the fiber optic sensing chain 100 accordingly.

[0079] It is understandable that since the deformation of the tunnel in the circumferential direction is mostly due to the stress changes in the surrounding rock at the top, the locations where the deformation is most significant are often concentrated in areas such as the top, spandrels and waists. Therefore, we installed five tilt sensors 200 at these key locations in the sensing chain to capture the tilt data at a 45-degree angle at the top of the tunnel, and use this to correct the cumulative errors that may be generated by the optical fiber sensing chain 100. When applying the deformation algorithm based on the optical fiber sensing chain 100, it is necessary to ensure that the starting point of the curve obtained by the sensor coincides with the original curve. In order to meet the specific requirements of circumferential monitoring of the tunnel, appropriate calibration is required at both ends. By adjusting the curve to match the intuitive needs of circumferential monitoring, we can more accurately reflect the actual deformation of the tunnel.

[0080] In some embodiments of the present application, the value measured by the tilt sensor 200 is set as an initial value, and then the correction coefficient k is used to perform correction. The specific method is:

[0081] First, the real-time tilt angle θ1 is obtained from the tilt sensor 200. The product of the strain data obtained from the sensor chain and θ1 is used as the reconstructed tilt angle θ2. The objective function and the global optimal solution are determined based on the particle swarm algorithm to determine the k value.

[0082] Assign velocity and position attributes to several particles, and each particle determines the optimal solution within the set k value range. Finally, the optimal solutions of all particles are shared to determine the global optimal solution k.

[0083] Take the inclination angle of the two sensors at the spandrel as θ 11 and θ 12 , the reconstructed tilt angle is θ 21 and θ 22 , and the sensor’s position at this time is (x i ,y i ), let (x i-1 ,y i-1 ) and (x i+1 ,y i+1 ) are the coordinates of two adjacent points, then θ 21 and θ 22 for:

[0084]

[0085] Where m and n are the serial numbers of the tilt sensor;

[0086] The objective function is:

[0087]

[0088] After the cumulative error correction is performed, in order to measure the correction effect, the error between the reconstructed deformation of the sensing chain and the actual deformation is expressed as the mean absolute error of the X coordinate and the Y coordinate:

[0089]

[0090] Where X1 and X2 are the actual coordinates of the measuring points, Y1 and Y2 are the reconstructed coordinates, and n is the number of measured points.

[0091] It can be understood that compared with traditional local point measurements, the fiber optic sensor chain 100 can obtain more complete and comprehensive measurement data; by obtaining information on key points through the high-precision tilt sensor 200 additionally installed in the fiber optic sensor chain 100, the particle swarm optimization algorithm is used to perform in-situ correction on the circumferential deformation field of the fiber optic sensor chain 100, thereby reducing the measurement cumulative error of the tunnel circumferential deformation field and significantly improving the measurement accuracy.

[0092] In some embodiments of the present application, the steps of installing the fiber optic sensing chain 100 in a tunnel profile include:

[0093] Before starting work, the installation location must be determined and the appropriate point must be selected according to monitoring requirements;

[0094] Install a fixed bracket or erect a frame according to the point to support the installation of the optical fiber sensor chain 100;

[0095] The optical fiber sensing chain 100 is laid and arranged according to a predetermined outline or path.

[0096] It can be understood that the optical fiber sensing chain 100 is installed on the inner side of the tunnel section along the tunnel circumference, and is fixed by an anchoring method so that it fits tightly with the inner surface of the tunnel.

[0097] In some embodiments, the steps for installing the fiber optic sensor chain 100 in the tunnel profile are as follows: First, the installation location must be determined before work begins. The appropriate point is selected based on the monitoring requirements, and collisions with subsequent construction are avoided as much as possible. The surface must be clean and flat to ensure the accuracy and reliability of the sensor. Next, a fixed bracket or erection frame is installed to provide support for the safe installation of the fiber optic sensor chain 100. When laying out the fiber optic sensor chain 100, it must be laid according to the predetermined contour or path, avoiding any unnecessary bending or stretching to ensure the accuracy of the sensor data. The connection phase includes connecting the sensor to the data acquisition system and performing rigorous functional testing to verify its normal operation and ability to accurately collect data.

[0098] In some embodiments of the present application, the method of arranging the optical fiber sensing chain 100 includes: fixing the optical fiber sensing chain 100 on a fixed bracket or a mounting frame using a fixing fixture and / or adhesive.

[0099] In some embodiments, securing the fiber optic sensor includes using an appropriate fixture or adhesive to ensure the device is securely fixed in the tunnel environment and withstands vibration and temperature fluctuations. Finally, sensor position and system calibration are adjusted to optimize monitoring results, and a regular maintenance plan is established to ensure long-term stable operation of the device.

[0100] In some embodiments of the present application, the preparation process of the optical fiber sensing chain 100 includes:

[0101] Along the central axis of the flexible protective material, the optical fiber and the protective material are bonded together and initially fixed;

[0102] Mix epoxy resin and curing agent in a 1:1 ratio to ensure tight coupling between the optical fiber and the protective material, and lead out the optical fiber at both ends of the protective material.

[0103] In some embodiments, the protective material is a carbon fiber protective material.

[0104] It is understood that during the manufacturing process of the fiber optic sensor chain 100, the strain sensing optical fiber 110 is tightly bonded to the protective material. The protective material selected is a corrosion-resistant carbon fiber sheet 120, the dimensions of which are customized according to the specific structure being measured. The specific preparation process is as follows: the optical fiber and the protective material are bonded along the central axis of the flexible protective material and initially fixed; epoxy resin and curing agent are mixed in a 1:1 ratio to ensure a tight coupling between the optical fiber and the carbon fiber protective material; and the optical fiber is led out at both ends of the protective material.

[0105] Reference Figures 1 to 4 The device for monitoring tunnel surrounding rock settlement and convergence according to the second embodiment of the present application may be a device for performing the method for monitoring tunnel surrounding rock settlement and convergence according to the first embodiment of the present application. The device for monitoring tunnel surrounding rock settlement and convergence includes:

[0106] The optical fiber sensing chain 100 is installed on the inner side of the tunnel section along the tunnel annular direction and fits tightly with the inner surface of the tunnel;

[0107] Tunable laser, used to emit continuously swept light of wavelength;

[0108] A coupler A, configured to receive the frequency-sweep light of the tunable laser and split it into two parts;

[0109] A coupler D receives a portion of the light emitted from the coupler A, generates an external clock signal through beat frequency interference, and transmits the signal to a first photodetector for photoelectric conversion;

[0110] a coupler B, receiving another portion of light emitted from the coupler A and dividing the light into two portions;

[0111] a polarization controller, receiving a portion of the light emitted by the coupler B, wherein the polarization controller is used to form a reference light path and exists as a local oscillator light;

[0112] a circulator, receiving another portion of the light emitted by the coupler B, and transmitting the light to the measurement optical path of the optical fiber sensor chain 100 through the three ports of the circulator;

[0113] A balanced photodetector, used to receive the optical signals after beat frequency interference in the reference optical path and the measurement optical path respectively;

[0114] The data acquisition card is used to receive information from each of the photoelectric detectors and transmit it to the data processing platform.

[0115] Understandably, this application considers that existing tunnel monitoring and measurement methods can only detect deformation at local points in the tunnel, making it difficult to monitor deformation throughout the entire tunnel. Therefore, based on optical frequency domain reflectometry, this application researches and fabricates a fiber optic sensor chain 100 using carbon fiber composite material as a protective material, specifically addressing tunnel face settlement and convergence issues.

[0116] In some embodiments, the specific monitoring process is as follows:

[0117] The tunable laser emits a continuously swept wavelength of light, which is then split into two parts by coupler A. One part enters the auxiliary interferometer connected to coupler D and undergoes beat frequency interference, generating an external clock signal that is then transmitted to a photodetector for photoelectric conversion. The other part enters the main interferometer connected to coupler B. After being split by coupler B, a small portion of the light enters the polarization controller of the reference optical path and exists as local oscillator light, while the majority of the light enters the measurement optical path through a three-port circulator. The optical signals in the reference and measurement optical paths undergo beat frequency interference and are received by two photodetectors, respectively. They are then collected by two channels of an acquisition card. This collected data is then transmitted to the data processing platform for demodulation algorithm processing. Finally, it is displayed using the aforementioned LABVIEW software.

[0118] In some embodiments of the present application, tilt sensors 200 are also installed at the top, spandrels, and haunches of the tunnel's inner surface. Data from these tilt sensors 200 is transmitted to a data processing platform and used to perform in-situ corrections to the circumferential deformation field of the fiber optic sensor chain 100. By acquiring information from key points through the high-precision tilt sensors 200 additionally installed in the fiber optic sensor chain 100, in-situ corrections to the circumferential deformation field of the fiber optic sensor chain 100 are performed using a particle swarm optimization algorithm, thereby reducing the cumulative measurement error of the tunnel's circumferential deformation field and significantly improving measurement accuracy.

[0119] The storage medium of the third aspect embodiment of the present application includes: at least one instruction is stored in the storage medium, and the instruction is loaded and executed by the processor to implement the operations performed by the method for monitoring tunnel surrounding rock settlement and convergence as in the first aspect embodiment of the present application.

[0120] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] The embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A method for monitoring tunnel surrounding rock settlement and convergence, characterized in that: The following steps are involved: The optical fiber sensing chain is installed on the inner side of the tunnel section along the tunnel ring and fits tightly with the inner surface of the tunnel; The tunable laser emits a continuous wavelength swept light which is then divided into two parts by coupler A; A portion of the light enters the auxiliary interferometer connected to the coupler D and performs beat frequency interference, generating an external clock signal which is then transmitted to the first photodetector for photoelectric conversion. The other part enters the main interferometer connected to coupler B. After being split by coupler B, part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, while the other part of the light enters the measurement optical path of the fiber optic sensor chain through the three-port circulator. The optical signals in the reference optical path and the measurement optical path undergo beat frequency interference and are processed by a balanced photodetector consisting of two photodetectors respectively; The data from the first photodetector and the balanced photodetector are collected by the data acquisition card, and the collected data are transmitted to the data processing platform for demodulation algorithm processing and display; Install inclination sensors on the top, spandrels, and waist areas of the tunnel's inner surface to capture inclination data at a 45-degree angle from the tunnel top, and use this data to correct the accumulated errors generated by the fiber optic sensing chain. Set the value measured by the inclination sensor to the initial value, and then use the correction coefficient k Complete the correction as follows: First, obtain the real-time tilt angle from the above tilt sensor θ 1. The strain data obtained from the sensing chain and θ The product of 1 is used as the reconstruction inclination θ 2. Determine the objective function and global optimal solution based on the particle swarm algorithm k value; Assign several particles speed and position attributes, each particle in the set k The optimal solution is determined within the value range, and finally the optimal solutions of all particles are shared to determine the global optimal solution k； The inclination angles of the two sensors at the spandrel are θ 11 and θ 12 , the reconstructed caster angle is θ 21 and θ 22 , and the sensor’s position at this time is (x i ,y i ), let (x i-1 ,y i-1 ) and (x i+1 ,y i+1 ) are the coordinates of two adjacent points, then θ 21 and θ 22 for: Where, m and n It is the serial number of the tilt sensor; The objective function is: After the cumulative error correction is performed, in order to measure the correction effect, the error between the reconstructed deformation of the sensing chain and the actual deformation is expressed as X Coordinates and Y The mean absolute error of the coordinates is expressed as: Where, X 1. X 2 is the actual coordinate of the measuring point, Y 1. Y 2 is the reconstruction coordinate, n is the number of measured points.

2. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 1, characterized in that: The steps for installing a fiber optic sensing chain in a tunnel profile include: Before starting work, the installation location must be determined and the appropriate point must be selected according to monitoring requirements; Install fixed brackets or erect frames according to the points to support the installation of the fiber optic sensor chain; Lay and arrange the fiber optic sensing chain according to a predetermined outline or path.

3. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 2, characterized in that: The method for arranging the optical fiber sensing chain includes: fixing the optical fiber sensing chain on a fixed bracket or a mounting frame using a fixing clamp and / or an adhesive.

4. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 1, characterized in that: The preparation process of the optical fiber sensing chain includes: Along the central axis of the flexible protective material, the optical fiber and the protective material are bonded together and initially fixed; Mix epoxy resin and curing agent in a 1:1 ratio to ensure tight coupling between the optical fiber and the protective material, and lead out the optical fiber at both ends of the protective material.

5. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 4, characterized in that: The protective material is carbon fiber protective material.

6. A device for monitoring the settlement and convergence of tunnel surrounding rocks, to implement the method for monitoring the settlement and convergence of tunnel surrounding rocks as claimed in any one of claims 1 to 5, characterized in that: include: The optical fiber sensor chain is installed on the inner side of the tunnel section along the tunnel ring and fits tightly with the inner surface of the tunnel; Tunable laser, used to emit continuously swept light of wavelength; A coupler A, configured to receive the frequency-sweep light of the tunable laser and split it into two parts; A coupler D receives a portion of the light emitted from the coupler A, generates an external clock signal through beat frequency interference, and transmits the signal to a first photodetector for photoelectric conversion; a coupler B, receiving another portion of light emitted from the coupler A and dividing the light into two portions; a polarization controller, receiving a portion of the light emitted by the coupler B, wherein the polarization controller is used to form a reference light path and exists as a local oscillator light; a circulator, receiving another portion of the light emitted by the coupler B and transmitting the light to the measurement optical path of the optical fiber sensing chain through the three ports of the circulator; A balanced photodetector, used to receive the optical signals after beat frequency interference in the reference optical path and the measurement optical path respectively; The data acquisition card is used to receive information from each of the photoelectric detectors and transmit it to the data processing platform.

7. The device for monitoring tunnel surrounding rock settlement and convergence according to claim 6, characterized in that: It also includes inclination sensors arranged on the top of the tunnel inner surface, the arch shoulders on both sides, and the arch waist areas on both sides. The data of the inclination sensors are transmitted to the data processing platform and used to perform in-situ correction of the annular deformation field of the optical fiber sensor chain.

8. A storage medium, characterized in that: include: The storage medium stores at least one instruction, which is loaded and executed by the processor to implement the operations performed by the method for monitoring tunnel surrounding rock settlement and convergence according to any one of claims 1 to 5.

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