Method and device for monitoring settlement and convergence of tunnel surrounding rock

Abstract

The invention discloses a method and device for monitoring settlement and convergence of tunnel surrounding rock. The method comprises the following steps that optical fiber sensing chains are installed in the circumferential direction of a tunnel; the tunable laser emits frequency sweeping light with continuous wavelength and then the frequency sweeping light is divided into two parts through the coupler A; after one part of light enters a coupler D, signals are transmitted to a first photoelectric detector; the other part of the light enters a coupler B, and after the light is split by the coupler B, one part of the light enters a polarization controller of the reference light path, and the other part of the light enters a measuring light path of the optical fiber sensing chain; optical signals in the reference optical path and the measurement optical path are subjected to beat frequency interference and are received by a balanced photoelectric detector; data of the first photodetector and the balanced photodetector are acquired. The optical fiber sensing chain is installed along the tunnel in the circumferential direction, tunnel deformation is monitored through an OFDR distributed optical fiber sensing system, overall deformation of a protection material is reconstructed through obtained distributed strain data, and an effective means is provided for large-range measurement of deformation fields such as a tunnel face.

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 surrounding rock in a tunnel. Background Art

[0002] At present, the commonly used tunnel settlement and convergence measurement methods in engineering projects include total station measurement method, convergence meter method, level measurement method, microwave radar and ultrasonic detection technology. Among them, the total station method uses a total station to perform three-dimensional coordinate measurement to obtain tunnel settlement and convergence data, and has good 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, and has good measurement accuracy; microwave radar can penetrate the tunnel surrounding rock and detect deformation in the deep; ultrasonic detection technology can detect subtle changes such as cracks inside the rock.

[0003] However, in tunnel settlement convergence monitoring, different methods have their own advantages and disadvantages. Although the total station measurement method is highly efficient, it is easily affected by external factors such as wind and vibration of objects passing through the tunnel, resulting in poor data stability; the convergence meter method is simple to operate but may cause damage to the tunnel and has poor data stability; in addition, this method can only measure the convergence around the tunnel and cannot fully reflect the overall deformation of the tunnel; the level measurement method is highly accurate but 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 detection technology has limited application in the deep part of complex structures and requires a clear sound wave propagation path. Therefore, when choosing a monitoring method, it is necessary to make comprehensive considerations based on specific engineering conditions and needs.

[0004] In this regard, 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 purpose of this application is to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a method for monitoring the settlement and convergence of tunnel surrounding rock, which reconstructs the overall deformation of the protective material by obtaining distributed strain data, and provides an effective means for large-scale measurement of deformation fields such as tunnel faces.

[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 aspect of the present application, the method for monitoring tunnel surrounding rock settlement and convergence comprises the following steps:

[0009] The optical fiber sensor chain is installed on the inner side of the tunnel section along the tunnel ring and fits closely 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 frequency interference, generates an external clock signal, and transmits the signal 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, one part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, and the other part of the light enters the measurement optical path of the optical fiber sensor chain through the three-port circulator.

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

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

[0015] The method for monitoring the settlement and convergence of tunnel surrounding rock according to the first aspect of the embodiment of the present application has at least the following beneficial effects: by installing the optical fiber sensor 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 sensor chain can easily sense the strain along the length of the optical fiber, and the overall deformation of the protective material can be reconstructed through the obtained distributed strain data, which provides 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 first aspect of the embodiment of the present application, inclination sensors are installed on the top of the inner surface of the tunnel, on the arch shoulders on both sides, and on the arch waist areas on both sides to capture the inclination data at a 45-degree angle on the top of the tunnel, and the cumulative error generated by the optical fiber sensor chain is corrected accordingly.

[0017] According to the method for monitoring tunnel surrounding rock settlement and convergence described in 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] Firstly, the real-time inclination angle θ1 is obtained from the above-mentioned inclination sensor, and the product of the strain data obtained from the sensor chain and θ1 is used as the reconstructed inclination 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 is located at (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] In the formula, m and n are the serial numbers of the tilt angle sensors;

[0023] The objective function is:

[0024]

[0025] After the cumulative error correction, in order to measure the correction effect, the error between the reconstructed deformation of the sensor chain and the actual deformation is expressed by the average 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 first aspect of the present application, the step of installing a fiber optic sensor chain in the tunnel profile includes:

[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 first aspect of the embodiment of the present application, the method for arranging the optical fiber sensor chain includes: fixing the optical fiber sensor chain on a fixed bracket or a mounting frame using a fixing clamp and / or an adhesive.

[0033] According to the method for monitoring tunnel surrounding rock settlement and convergence described in 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 a preliminary fixing process is performed;

[0035] Mix epoxy resin and curing agent in a one-to-one ratio to ensure that the optical fiber and the protective material are tightly coupled, and lead out the optical fiber at both ends of the protective material.

[0036] According to the method for monitoring the settlement and convergence of tunnel surrounding rock 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 aspect 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 closely with the inner surface of the tunnel;

[0039] Tunable laser for emitting a continuously swept light;

[0040] A coupler A, used for receiving the frequency-sweeping light of the tunable laser and dividing it into two parts;

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

[0042] A coupler B receives another part of the light emitted from the coupler A and divides it into two parts;

[0043] A polarization controller receives 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 part of the light emitted by the coupler B, and entering the other part of the light into the measurement optical path of the optical fiber sensor chain through the three ports of the circulator;

[0045] A balanced photodetector, used for receiving light signals after beat frequency interference in the reference light path and the measurement light path respectively;

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

[0047] The device for monitoring the settlement and convergence of tunnel surrounding rock according to the second aspect embodiment of the present application 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 on the annular deformation field of the optical fiber sensor chain.

[0048] According to 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 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 described above, and therefore will not be elaborated upon.

[0050] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the 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 sensor chain according to an embodiment of the present application;

[0053] Figure 2 This is a schematic diagram of the composition of the OFDR optical fiber sensing system in the embodiment of the present application;

[0054] Figure 3 A 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. Optical fiber sensing chain; 110. Sensing optical fiber; 120. Carbon fiber plate;

[0058] 200. Tilt sensor. DETAILED DESCRIPTION

[0059] The embodiments of the present application are described in detail below, and 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 cannot be understood as limiting the present application.

[0060] In the description of the present application, it should be understood that descriptions involving orientation, 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, and are only for the convenience of describing the present 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, and therefore should not be understood as a limitation on the present application.

[0061] In the description of this application, "several" means one or more, "more" means at least two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0062] In the description of this application, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians 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 tunnel surrounding rock settlement and convergence 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 tunnel surrounding rock settlement and convergence 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 paste 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 through the acquired distributed strain data, which provides an effective means for large-scale measurement of deformation fields such as tunnel faces.

[0064] It is understandable that, considering that most existing tunnel monitoring and measurement methods can only obtain the deformation of local points in the tunnel, it is difficult to monitor the deformation of the entire tunnel. Therefore, based on the optical frequency domain reflection technology, a fiber optic sensor chain 100 with carbon fiber composite material as the protective material is studied and prepared, focusing on the settlement and convergence problems of the tunnel face.

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

[0066] The optical fiber sensor chain 100 is installed on the inner side of the tunnel section along the tunnel ring direction and fits closely 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 frequency interference, generates an external clock signal, and transmits the signal to the first photodetector for photoelectric conversion;

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

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

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

[0072] It is understandable that the optical fiber sensing chain 100 achieves accurate capture of strain data through advanced optical frequency domain reflection distributed optical fiber sensing technology. This technology not only has high measurement accuracy and a wide measurement range, but also has excellent anti-interference ability, and is particularly suitable for accurate measurement of strain and temperature changes.

[0073] In some embodiments, the optical fiber sensor chain 100 is mainly used for tunnel deformation monitoring. The optical fiber deformation sensor is carefully installed on the longitudinal bottom plate of the tunnel, responsible for real-time monitoring of the deformation of the tunnel, and providing key data support for subsequent deformation field analysis, reconstruction and adjustment.

[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 pulse laser can be selected. The photoelectric conversion efficiency is a very important parameter of the photoelectric detector. 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 laser frequency scanning control program, data capture program, and signal analysis program.

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

[0076] In some embodiments, reference Figure 1 A part of the light enters the auxiliary interferometer connected to the coupler D and the beat frequency interference is realized by the delay fiber and the coupler E. The beat frequency interference of the optical signal in the reference optical path and the measurement optical path is realized by the 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 the settlement and convergence of tunnel surrounding rock in the first aspect of the embodiment of the present application can obtain more complete and comprehensive measurement data by installing the optical fiber sensor chain 100 along the tunnel ring, and using the OFDR distributed optical fiber sensing system to monitor the tunnel deformation. It 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, which provides 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 and waist areas of the inner surface of the tunnel to capture the inclination data at a 45-degree angle on the top of the tunnel, and to correct the accumulated error generated by the optical fiber sensor chain 100 accordingly.

[0079] It is understandable that since the deformation of the tunnel in the circumferential direction is mostly caused by the stress change of the surrounding rock at the top, the most significant deformation locations are often concentrated in the top, spandrel and waist areas. Therefore, we installed 5 inclination sensors 200 at these key locations of the sensor chain to capture the inclination data at the 45-degree position of the top of the tunnel, and correct the cumulative errors that may be generated by the optical fiber sensor chain 100 accordingly. When applying the deformation algorithm based on the optical fiber sensor 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 complete the correction. The specific method is:

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

[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 is located at (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] In the formula, m and n are the serial numbers of the tilt angle sensors;

[0086] The objective function is:

[0087]

[0088] After the cumulative error correction, in order to measure the correction effect, the error between the reconstructed deformation of the sensor chain and the actual deformation is expressed by the average 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 inclination 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 annular deformation field of the fiber optic sensor chain 100, thereby reducing the measurement cumulative error of the tunnel annular deformation field and significantly improving the measurement accuracy.

[0092] In some embodiments of the present application, the steps of installing the optical fiber sensing chain 100 in the 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 profile or path.

[0096] It can be understood that the optical fiber sensor chain 100 is installed on the inner side of the tunnel section along the tunnel circumference, and is fixed by anchoring 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, and a suitable point must be selected according to the monitoring requirements, and collisions with subsequent construction must be avoided as much as possible, and 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 arranging the fiber optic sensor chain 100, it must be laid according to the predetermined contour or path to avoid any unnecessary bending or stretching to ensure the accuracy of the sensor data. The connection stage includes connecting the sensor to the data acquisition system and conducting 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 clamp and / or an adhesive.

[0099] In some embodiments, the step of fixing the optical fiber sensor includes using an appropriate fixing fixture or adhesive to ensure that the device can be firmly fixed in the tunnel environment and resist vibration and temperature changes. Finally, the monitoring effect is optimized by adjusting the sensor position and system calibration, and a regular maintenance plan is established to ensure the long-term stable operation of the device.

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

[0101] Along the central axis of the flexible protective material, the optical fiber and the protective material are bonded together and a preliminary fixing process is performed;

[0102] Mix epoxy resin and curing agent in a one-to-one ratio to ensure that the optical fiber and the protective material are tightly coupled, 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 understandable that during the manufacturing process of the optical fiber sensing chain 100, the strain sensing optical fiber 110 is tightly combined with the protective material. The selected protective material is a carbon fiber plate 120 with excellent corrosion resistance, and its size is customized according to the size of the specific structure to be measured. The specific preparation process is: along the central axis of the flexible protective material, the optical fiber and the protective material are bonded and preliminarily fixed; epoxy resin and curing agent are mixed in a one-to-one ratio to ensure that the optical fiber and the carbon fiber protective material can be tightly coupled; 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 of the second aspect of the present application may be a device for executing the method for monitoring tunnel surrounding rock settlement and convergence of the first aspect of the present application. The device for monitoring tunnel surrounding rock settlement and convergence includes:

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

[0107] Tunable laser for emitting a continuously swept light;

[0108] A coupler A, used for receiving the frequency-sweeping light of the tunable laser and dividing it into two parts;

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

[0110] A coupler B receives another part of the light emitted from the coupler A and divides it into two parts;

[0111] A polarization controller receives 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 receives another part of the light emitted by the coupler B and enters the measuring optical path of the optical fiber sensor chain 100 through the three ports of the circulator;

[0113] A balanced photodetector, used for receiving light signals after beat frequency interference in the reference light path and the measurement light path respectively;

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

[0115] It is understandable that the present application takes into account that most existing tunnel monitoring and measurement methods can only obtain the deformation of local points in the tunnel, and it is difficult to monitor the deformation of the entire tunnel. Therefore, based on the optical frequency domain reflection technology, the optical fiber sensor chain 100 with carbon fiber composite material as the protective material is studied and prepared, focusing on the settlement and convergence problems of the tunnel face.

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

[0117] After the tunable laser emits a continuous wavelength swept light, it is divided into two parts through coupler A: one part of the light enters the auxiliary interferometer connected to coupler D and performs beat frequency interference, generates an external clock signal and transmits the signal to the photodetector for photoelectric conversion; the other part enters the main interferometer connected to coupler B. After being split by coupler B, a small part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, and most of the light enters the measurement optical path through the three-port circulator. The optical signals in the reference optical path and the measurement optical path perform beat frequency interference and are received by two photodetectors respectively, and then collected by two channels of the acquisition card. The collected data is transmitted to the data processing platform for demodulation algorithm processing. Finally, it is displayed through the above-mentioned LABVIEW software.

[0118] In some embodiments of the present application, the tilt sensors 200 are also provided at the top of the inner surface of the tunnel, the spandrels on both sides, and the waist areas on both sides. The data of the tilt sensors 200 are transmitted to the data processing platform and used to make in-situ corrections to the annular deformation field of the optical fiber sensor chain 100. The information of key points is obtained by the high-precision tilt sensors 200 additionally installed on the optical fiber sensor chain 100, and the annular deformation field of the optical fiber sensor chain 100 is corrected in-situ by using the particle swarm optimization algorithm, thereby reducing the measurement cumulative error of the annular deformation field of the tunnel and significantly improving the 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-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present application.

Claims

1. A method for monitoring the settlement and convergence of surrounding rock in a tunnel, characterized in that: The following steps are involved: The optical fiber sensor chain is installed on the inner side of the tunnel section along the tunnel ring and fits closely 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 frequency interference, generates an external clock signal, and transmits the signal to the first photodetector for photoelectric conversion; The other part enters the main interferometer connected to coupler B. After being split by coupler B, one part of the light enters the polarization controller of the reference optical path and exists as local oscillator light, and the other part of the light enters the measurement optical path of the optical fiber sensor chain through the three-port circulator. The optical signals in the reference optical path and the measurement optical path are subjected to beat frequency interference and are processed by a balanced photodetector composed of two photodetectors respectively; The data of the first photoelectric detector and the balanced photoelectric detector are collected by the data acquisition card, and the collected data are transmitted to the data processing platform for demodulation algorithm processing and display.

2. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 1, characterized in that: Inclination sensors are installed on the top of the tunnel inner surface, on the spandrels on both sides, and on the waist areas on both sides to capture the inclination data at a 45-degree angle on the top of the tunnel, and to correct the accumulated errors generated by the optical fiber sensing chain accordingly.

3. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 2, characterized in that: Set the value measured by the inclination sensor as the initial value, and then use the correction coefficient k to complete the correction. The specific method is: Firstly, the real-time inclination angle θ1 is obtained from the above-mentioned inclination sensor, and the product of the strain data obtained from the sensor chain and θ1 is used as the reconstructed inclination angle θ2. The objective function and the global optimal solution are determined based on the particle swarm algorithm to determine the k value; 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. 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 is located at (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: In the formula, m and n are the serial numbers of the tilt angle sensors; The objective function is: After the cumulative error correction, in order to measure the correction effect, the error between the reconstructed deformation of the sensor chain and the actual deformation is expressed by the average absolute error of the X coordinate and the Y coordinate: 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.

4. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 1, characterized in that: The steps to install a fiber optic sensor 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.

5. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 4, 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 fixture and / or an adhesive.

6. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 1, characterized in that: The preparation process of the optical fiber sensor chain includes: Along the central axis of the flexible protective material, the optical fiber and the protective material are bonded together and a preliminary fixing process is performed; Mix epoxy resin and curing agent in a one-to-one ratio to ensure that the optical fiber and the protective material are tightly coupled, and lead out the optical fiber at both ends of the protective material.

7. The method for monitoring tunnel surrounding rock settlement and convergence according to claim 6, characterized in that: The protective material is carbon fiber protective material.

8. A device for monitoring the settlement and convergence of surrounding rock in a tunnel, 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 closely with the inner surface of the tunnel; Tunable laser for emitting a continuously swept light; A coupler A, used for receiving the frequency-sweeping light of the tunable laser and dividing it into two parts; A coupler D receives a portion of the light emitted from the coupler A, and after the coupler D generates an external clock signal through beat frequency interference, transmits the signal to a first photodetector for photoelectric conversion; A coupler B receives another part of the light emitted from the coupler A and divides it into two parts; A polarization controller receives 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 part of the light emitted by the coupler B, and entering the other part of the light into the measurement optical path of the optical fiber sensor chain through the three ports of the circulator; A balanced photodetector, used for receiving light signals after beat frequency interference in the reference light path and the measurement light path respectively; The data acquisition card is used to receive the information of each photoelectric detector and transmit it to the data processing platform.

9. The device for monitoring the settlement and convergence of surrounding rock in a tunnel according to claim 8, characterized in that: 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 on the annular deformation field of the optical fiber sensor chain.

10. 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 as described in any one of claims 1 to 7.

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