A method of tunnel monitoring

Abstract

The application relates to a tunnel monitoring method, which comprises the following steps: determining a monitoring section of a tunnel, acquiring external force distribution information of the monitoring section, and determining a maximum external force position of a segment in the monitoring section; performing finite element static simulation analysis on the whole monitoring section of the tunnel to obtain internal force distribution information of the monitoring section under external static load; performing finite element dynamic simulation analysis on the whole monitoring section of the tunnel to obtain acceleration distribution information of the segment at different positions under external dynamic load; obtaining a maximum stress position and a maximum segment acceleration position of the monitoring section based on the internal force distribution information and the acceleration distribution information; and setting monitoring sensors at the maximum external force position, the maximum stress position and the maximum segment acceleration position respectively to obtain monitoring data of the monitoring sensors. The application effectively monitors the stress and vibration conditions of weak links of the tunnel, and simultaneously provides long-term monitoring of the health of the underground tunnel and early warning of dangers such as external malicious excavation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tunnel construction, in particular to a tunnel monitoring method. BACKGROUND

[0002] With the development of economy, the acceleration of urbanization and modernization, the subway has become an important part of people's life and city, and its safety problem has inevitably become a major topic. Since the subway tunnel is mostly underground, the space is closed, the crowd is dense, and the service life is generally several decades, when encountering disasters such as collapse, benching caused by non-standard construction or tunnel structure instability, if it cannot be discovered in time or even early warning, it will cause great harm to the safety of society and people's life and property. Therefore, it is very meaningful to monitor the changes of stress and strain and external excavation vibration interference of tunnel structure in real time.

[0003] In related technologies, an optical fiber grating sensor is arranged on the tunnel, and strain or dynamic impact information under static state is collected by the optical fiber grating sensor and transmitted to a control platform. When the value monitored by the control platform exceeds the limit, an alarm signal is output to inform relevant maintenance personnel to repair in time or take preventive measures in advance to reduce the probability of tunnel collapse and other accidents.

[0004] However, the actual stress of each tunnel and each segment of segment will be different due to different environments, and the quality difference caused by the process of each segment itself, so that the weak points of each segment also differ. Therefore, the stress condition of the whole tunnel is very complex in the actual use process of the tunnel.

[0005] The sensors used in the prior art are often arranged randomly by construction personnel according to their past experience, without any further accurate basis, and cannot be adjusted specifically for each tunnel. Therefore, there is a large deviation between the monitoring result and the actual result, which cannot represent the actual stress condition of the tunnel, and even some weak parts have cracks and cracks, but the monitoring result cannot be reflected in time. SUMMARY

[0006] The embodiment of the present application provides a tunnel monitoring method to solve the problem that the sensor in related technologies only monitors one parameter of the stress distribution of the tunnel segment or the external vibration of the segment, and the arrangement position of the sensor is not specified, and the sensor is often arranged according to experience, so that the sensor only monitors part of the segments of the tunnel structure, and the whole tunnel cannot be reflected by part of the segments, so the tunnel cannot be accurately monitored.

[0007] The present application provides a tunnel monitoring method, the method comprising:

[0008] determining a monitoring section of the tunnel, obtaining external force distribution information of the monitoring section, and determining a maximum external force position of the segment in the monitoring section;

[0009] performing finite element static simulation analysis on the whole monitoring section of the tunnel to obtain internal force distribution information of the monitoring section under external static load;

[0010] performing finite element dynamic simulation analysis on the whole monitoring section of the tunnel to obtain acceleration distribution information of the segment at different positions under external dynamic load;

[0011] obtaining a maximum stress position and a maximum acceleration position of the segment based on the internal force distribution information and the acceleration distribution information;

[0012] setting monitoring sensors at the maximum external force position, the maximum stress position and the maximum acceleration position of the segment respectively to obtain monitoring data of the monitoring sensors.

[0013] Preferably, before the finite element static simulation analysis and the finite element dynamic analysis, the method further comprises preprocessing, and the preprocessing comprises:

[0014] modeling and finite element meshing of the tunnel and the soil layer, setting density, elastic modulus and damping coefficient of the tunnel and the soil layer, and then performing finite element static analysis and finite element dynamic analysis on the monitoring section of the tunnel.

[0015] Preferably, the obtaining of the maximum stress position and the maximum acceleration position of the segment comprises:

[0016] determining the maximum stress position of the monitoring section based on the internal force distribution information by a fourth strength criterion;

[0017] obtaining acceleration variation of multiple points of the tunnel according to the acceleration distribution information, and determining the maximum acceleration position of the segment after comparison.

[0018] Preferably, the setting of the monitoring sensors at the maximum external force position, the maximum stress position and the maximum acceleration position of the segment respectively comprises:

[0019] setting a pull rod type stress / strain sensor at the maximum external force position of the segment;

[0020] setting a patch stress / strain sensor at the maximum stress position of the monitoring section;

[0021] setting a vibration sensor at the maximum acceleration position of the segment.

[0022] Preferably, the obtaining of the monitoring data of the monitoring sensors comprises:

[0023] obtaining monitoring data of the patch stress / strain sensor and the pull rod stress / strain sensor and obtaining the vibration sensor data.

[0024] Preferably, the obtaining monitoring data of the patch stress / strain sensor and the pull rod stress / strain sensor, in particular:

[0025] connecting the patch stress / strain sensor and the pull rod stress / strain sensor in series and connecting them to a fiber grating demodulation host for demodulation; the monitoring platform receives data of the fiber grating demodulation host through a demodulation channel.

[0026] Preferably, the obtaining the vibration sensor data, comprises:

[0027] connecting the vibration sensor to a vibration demodulation host; the monitoring platform receives data of the vibration demodulation host.

[0028] Preferably, after the obtaining monitoring data of the monitoring sensor, further comprising:

[0029] the monitoring platform graphically displays the data based on the data of the fiber grating demodulation host and the vibration demodulation host.

[0030] Preferably, after the obtaining monitoring data of the monitoring sensor, further comprising:

[0031] the monitoring platform sets a data warning value, when abnormal data exceeds the warning value, based on optical time domain reflectometry, through receiving the time passed by the abnormal data, gives the position of the abnormal point.

[0032] Preferably, when the monitoring section of the tunnel as a whole is subjected to finite element dynamic simulation analysis, the finite element dynamic simulation analysis is specifically: using the mode superposition method, first performing modal analysis on the monitoring section of the tunnel as a whole to determine the fixed mode shape of the tunnel and the soil layer at different frequencies, and then superimposing the mode shapes of the models at different frequencies.

[0033] The technical scheme provided by the application has the beneficial effects of:

[0034] (1) The tunnel monitoring method provided by the application first gives the cross section interval of tunnel stress monitoring based on finite element simulation, monitors the most fragile cross section and interval of the tunnel, and arranges stress / strain sensors and vibration sensors in the most fragile cross section and interval of the tunnel, so as to monitor the overall condition of the tunnel by monitoring the condition of the most fragile cross section and interval.

[0035] (2) The application provides a tunnel monitoring method based on finite element simulation, and gives the maximum vibration acceleration position of a tunnel structure caused by illegal construction above the tunnel, so that the vibration monitoring system can more sensitively perceive the construction behavior above the tunnel.

[0036] (3) The application provides a tunnel monitoring method, in which a stress and strain sensor adopts an optical fiber sensing technology, and can excellently complete real-time and accurate monitoring of parameters of a tunnel structure; a distributed vibration optical cable is designed as a spiral steel pipe armored vibration optical cable, which is very sensitive to external micro-vibration and is suitable for harsh use environments, and the universality of the monitoring system is improved.

[0037] (4) The application provides a tunnel monitoring method, which can form a tunnel structure parameter monitoring network, and the monitoring of the tunnel includes vibration, crack, opening, displacement and other data, and the monitoring level of the monitoring system is improved.

[0038] (5) The application provides a tunnel monitoring method, which can utilize the advantages of the optical fiber sensing technology, realizes real-time monitoring of the tunnel health, realizes early warning, and in combination with the optical fiber sensing technology, can effectively monitor the stress and strain of a weak link of a tunnel structure and external vibration interference, and can simultaneously provide long-term monitoring of the health of an underground tunnel and early warning of external malicious excavation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0040] Figure 1 The technical roadmap of the tunnel monitoring method provided by the embodiments of the present application is shown in the figure.

[0041] Figure 2 The tunnel 3D model provided by the embodiments of the present application is shown in the figure.

[0042] Figure 3 The tunnel overall 3D model provided by the embodiments of the present application is shown in the figure.

[0043] Figure 4 The tunnel structure stress distribution nephogram provided by the embodiments of the present application is shown in the figure.

[0044] Figure 5 The tunnel acceleration distribution nephogram provided by the embodiments of the present application is shown in the figure.

[0045] Figure 6 The tunnel eight-point acceleration change curve provided by the embodiments of the present application is shown in the figure.

[0046] Figure 7 A modal analysis result diagram provided by the embodiment of the present application;

[0047] Figure 8 A surface-mounted strain gauge installation schematic diagram provided by the embodiment of the present application;

[0048] Figure 9 A structure diagram of the surface-mounted strain gauge provided by the embodiment of the present application;

[0049] Figure 10 A tunnel vibration optical cable laying position schematic diagram provided by the embodiment of the present application;

[0050] Figure 11 A vibration optical cable structure and fixing fixture schematic diagram provided by the embodiment of the present application;

[0051] Figure 12 A strain / stress sensor installation schematic diagram in the segment axial position provided by the embodiment of the present application.

[0052] In the figure: 1, a capping block; 2, a first abutting block; 3, a second abutting block; 4, a first standard block; 5, a second standard block; 6, a third standard block; 7, a fire pipe; 8, a special leakage cable; 9, a distributed vibration sensing optical cable; 10, an outer sheath; 11, a woven mesh; 12, Kevlar; 13, a sensing optical fiber; 14, a spiral pipe; 15, a fiber Bragg strain / stress gauge; 16, a fiber Bragg surface-mounted strain gauge. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0054] The embodiment of the present application provides a tunnel monitoring method, which can solve the problem in the related art that a sensor only monitors one parameter in stress distribution of a tunnel segment or external vibration of the segment, and the sensor laying position is not specified, and the sensor is often laid according to experience, so that the sensor only monitors part of the segments of the tunnel structure, and part of the segments cannot reflect the overall situation of the tunnel, and thus the tunnel cannot be accurately monitored. Through finite element simulation analysis, the weak link of the underground tunnel is found, and the stress and strain of the weak link of the tunnel structure and the external vibration interference can be effectively monitored in real time by combining the optical fiber sensing technology, and the health long-term monitoring of the underground tunnel and the dangerous early warning of external malicious excavation can be provided at the same time.

[0055] The tunnel structure is a structure with weak links not obvious, that is, each part of the tunnel structure is a potential monitoring area, so in actual monitoring, it is obviously impossible to implement comprehensive monitoring on all sections and the entire length interval, and therefore, the weak links of the tunnel structure are analyzed by using finite element simulation, and based on this, the optical fiber sensing monitoring system is designed, so that the monitoring system can truly and effectively protect the safe operation of the structure.

[0056] As shown in Figure 1 , the embodiment of the present application provides a tunnel monitoring method, and the specific steps include:

[0057] Step one: determining the monitoring section of the tunnel, obtaining the external force distribution information of the monitoring section, and determining the maximum external force position of the segment in the monitoring section.

[0058] The external force distribution information refers to the stress distribution of the whole tunnel segment, and the most effective monitoring area of the tunnel circumferential stress / strain is the joint of the lining block, that is, the maximum external force position of the segment is the joint of the lining block.

[0059] Step two: performing finite element static simulation analysis on the whole monitoring section of the tunnel to obtain the internal force distribution information of the monitoring section under external static load. Specifically:

[0060] S21: using the finite element analysis software abaqus and the 3D modeling software, first, 3D modeling and finite element meshing are performed on the tunnel and the soil layer, the tunnel 3D model is as shown in Figure 2 , and the whole finite element model is as shown in Figure 3 , the tie contact mode is used between the lining and the segment, and the tracking unit is used between the soil layer and the tunnel to realize the common node of the soil layer and the tunnel interface mesh, and realize the continuous transmission of the force, displacement and other parameters between the soil layer and the segment;

[0061] When defining the contact boundary conditions of the soil and the tunnel in abaqus, the tracking unit method is used to copy the excavated soil by using the keyword *elcopy and renaming, then the properties of the concrete segment are defined, and finally the model change function is used to cancel the excavated soil unit model, so that the segment and the soil layer share the node.

[0062] S22: setting the related parameters such as the density, elastic modulus and damping coefficient of the soil and the tunnel structure according to the experimental and specification data;

[0063] S23: performing finite element static simulation analysis.

[0064] Wherein the internal force refers to the stress of a single lining block of a single ring segment constituting the tunnel; the static force analysis uses a softening modulus method to simulate the actual excavation process, wherein the softening modulus method is to first reduce the modulus of the excavated soil to realize the gradual release of ground stress, and then replace the excavated soil with a tunnel model, which is more in line with the actual excavation process to realize the gradual release of ground stress and is also more in line with the actual stress environment of the tunnel.

[0065] Step three: performing finite element dynamic simulation analysis on the whole monitoring section of the tunnel to obtain acceleration distribution information of the segments at different positions under external dynamic load. Specifically:

[0066] S31: using finite element analysis software abaqus and 3D modeling software, first performing 3D modeling and finite element meshing on the tunnel and the soil layer, the tunnel 3D model is as shown in Figure 2 , the overall finite element model is as shown in Figure 3 , the contact mode between the linings and between the segments is “tie”, and the tracking unit is used to realize the co-node of the soil layer and the tunnel interface mesh, so as to realize the continuous transmission of force, displacement and other parameters between the soil layer and the segments;

[0067] S32: setting the relevant parameters such as the density, elastic modulus and damping coefficient of the soil and the tunnel structure according to the experimental and specification data;

[0068] S33: performing finite element dynamic simulation analysis.

[0069] Wherein, in the dynamic analysis, the external disturbance source is an impact force of 1000N and the action time is 1s, so that the stress distribution cloud map of the tunnel structure under the action of external forces such as soil layer and the acceleration distribution cloud map of the tunnel under ground disturbance can be obtained, the Mises stress (σ) distribution cloud map and the axial force distribution cloud map obtained by simulation are as shown in Figure 4 , wherein the stress refers to the mises stress in the mises stress criterion, the axial force refers to the force along the length direction of the tunnel, i.e. s33, acting on the plane perpendicular to the z axis and along the z axis. The Mises stress criterion is the fourth strength criterion for judging material failure and damage, which is expressed in the following formula:

[0070]

[0071] In the above formula, σ1 is the first principal stress, σ2 is the second principal stress, σ3 is the third principal stress, and stress is a second order tensor. By appropriately rotating the coordinate system, it is found that under a certain angle, the stress only exists in three principal stresses, and there is no shear stress. At this time, the cross section in which the shear stress in the unit body is equal to zero is called the principal plane, and the normal stress on the principal plane is the extreme value of the normal stress on each cross section in the unit body, which is called the principal stress. Among the three principal stresses, they are called the first, second and third principal stresses in order of magnitude, i.e. the first principal stress, the second principal stress and the third principal stress.

[0072] The obtained tunnel acceleration distribution cloud diagram is as shown in Figure 5

[0073] The modal analysis is performed by using the mode superposition method in the abaqus, and the fixed mode of the tunnel and the soil at different frequencies is determined, as shown in Figure 7 In some embodiments, the mode of the model at different frequencies is superimposed to obtain the mode under external interference during actual analysis.

[0074] Step four: based on the internal force distribution information and the acceleration distribution information, the stress maximum of the monitoring section and the segment acceleration maximum are obtained. Specifically:

[0075] S41, according to the finite element analysis results of Figure 4 , the mises stress and the axial force maximum are obtained at the middle lower part, according to the mises stress criterion, i.e. the fourth strength criterion, the monitoring should be focused on, i.e. the stress maximum of the monitoring section, which is most prone to structural failure, so the patch type fiber grating sensor is arranged here.

[0076] S42, according to the tunnel acceleration distribution cloud diagram as shown in Figure 5 , and based on this, the acceleration changes of the upper, lower, left, right, upper left, lower left, upper right and lower right eight points of the tunnel are taken as shown in Figure 6 , which is disturbed by external disturbance, and the acceleration change amplitude is the largest at the beginning, which is most easily perceived by the Rayleigh scattering vibration sensor, which is the basis for setting the vibration sensor. Of course, the disturbance source is small here, and the difference is not big, when the disturbance source is large, the difference between each point will be shown, and the acceleration change curve of the eight points shows that the upper right part changes most sharply at the beginning, and the vibration fiber is most sensitive to external disturbance.

[0077] Based on the finite element static simulation and dynamic simulation, the internal force, external force distribution cloud diagram and acceleration distribution cloud diagram of the tunnel structure are calculated, the segment external force maximum, the stress maximum of the monitoring section and the segment acceleration maximum are the most dangerous areas of the segment, and the most dangerous areas are selected as the monitoring areas, which can realize the monitoring and layout of the most fragile section and interval and the part most sensitive to external disturbance, and more effectively ensure the safety of the tunnel structure.

[0078] The stress maximum and the segment acceleration maximum of the lining block subjected to external disturbance are determined by Figure 5 and Figure 6 , so the middle lower part of the tunnel is the weak link of the tunnel by the finite element static analysis, and the response to external disturbance is larger at the middle upper part of the tunnel by the finite element dynamic analysis.

[0079] ​Step five: setting the monitoring sensors at the maximum external force position of the segment, the maximum stress position of the monitoring segment and the maximum acceleration position of the segment. Specifically:

[0080] S51, setting the pull rod type stress / strain sensor at the maximum external force position of the segment, i.e. the joint between the same segment lining and the lining;

[0081] S52, setting the patch stress / strain sensor at the maximum stress position of the monitoring segment;

[0082] S53, setting the vibration sensor at the maximum acceleration position of the segment.

[0083] In this embodiment, the pull rod type stress / strain sensor is a fiber grating stress gauge (or fiber grating strain gauge) 15; the patch stress / strain sensor is a fiber grating surface patch type strain gauge 16; and the vibration sensor is a distributed vibration sensing optical cable 9.

[0084] In this embodiment, the stress / strain sensor includes a fiber grating surface patch type strain gauge 17 and a fiber grating strain / stress gauge 15. The fiber sensing technology has incomparable advantages over traditional sensing technology, such as good real-time performance, high resolution, high accuracy, strong applicability and easy reuse into a network, etc., which enables it to perform real-time and accurate monitoring of tunnel structure parameters. At present, it has gradually replaced traditional sensors and become a new technology for monitoring structural parameters in engineering. The selection of fiber grating fiber stress, strain and distributed vibration sensors as sensing elements can realize long-term real-time and accurate monitoring.

[0085] Step six: obtaining the monitoring data of the monitoring sensors. Specifically:

[0086] S61, connecting the fiber grating surface patch type strain gauge 16 and the fiber grating strain / stress gauge 15 in series and then connecting them to the fiber grating demodulation host for demodulation;

[0087] S62, connecting the vibration sensor to the vibration demodulation host;

[0088] S63, the monitoring platform receives the data of the fiber grating demodulation host and the vibration demodulation host;

[0089] S64, the monitoring platform graphs the data of the fiber grating demodulation host and the vibration demodulation host;

[0090] S65, setting a data warning value for the monitoring platform, when the abnormal data exceeds the warning value, based on the optical time domain reflection technology, the position of the abnormal point is given by receiving the time of the abnormal data.

[0091] The fiber grating surface patch strain gauge 16 and the fiber grating strain / stress gauge 15 are connected in series and connected to a fiber grating demodulation host for demodulation, the vibration sensor is connected to a vibration demodulation host, and the monitoring platform receives data of the fiber grating demodulation host and the vibration demodulation host.

[0092] The monitoring platform includes a monitoring host including a processor for analyzing monitored data, after the monitoring platform receives data of each demodulation host, the data can be displayed in a graphical manner through an Ethernet connection, facilitating real-time monitoring and management by monitoring personnel. An early warning value is set in the monitoring platform, and when the monitored value exceeds the early warning value, an alarm is immediately issued. Based on optical time domain reflection technology, that is, using backscattered light of an optical fiber, a light time domain reflectometer is used to measure several properties of the optical fiber. The position of the abnormal point can be given by the time taken by the received abnormal signal.

[0093] In the embodiment,

[0094] (1) Arrangement of fiber grating lining block stress and strain monitoring:

[0095] As Figure 8 shown, finite element static analysis shows that the middle and lower parts of the tunnel are weak links, and the fiber grating surface patch strain gauge 17 is used to monitor the stress and strain changes of the lining itself. The tunnel segments clockwise include a capping block 1, a second adjacent block 3, a third standard block 6, a second standard block 5, a first standard block 4, and a first adjacent block 2. In the embodiment, the fiber grating surface patch strain gauge 17 is fixedly installed on the second adjacent block 3 and the third standard block 6 by expansion screws. In some embodiments, the fiber grating surface patch strain gauge 17 is attached to the original segment using cement. The structure of the fiber grating surface patch strain gauge 17 is shown in Figure 9 Meanwhile, the sensors between the segments are connected in series through armored cables, the sensors are connected to a core of the armored communication cable through fusion, and are connected to a fiber grating demodulation host. The monitoring platform can set appropriate alarm thresholds. The total strain of the measured object or structure caused by factors such as changes in environmental temperature and load is calculated by the wavelength change value of the fiber sensor.

[0096] The corresponding strain calculation formula is:

[0097] ΔE=(λ-λ0-Δλ t ) / K

[0098] In the above formula: ΔE: relative strain, unit με; K: strain coefficient, unit pm / με; λ: current wavelength value of the fiber grating sensor, unit pm; λ0: initial wavelength value of the fiber grating sensor, unit pm; Δλ t : wavelength change of the fiber grating temperature sensor, unit pm.

[0099] (2) The arrangement of the circumferential stress and strain monitoring of the segment:

[0100] As shown in Figure 10 , the fiber grating strain / stress gauge 15 is installed at the joint of the same ring lining block and the lining block to monitor the circumferential strain parameter in real time. The two supports of the fiber grating strain / stress gauge 15 are fixed on the adjacent segments of the same ring respectively. The fiber sensor transmission line is connected to the fiber grating demodulation host through the FC / APC joint, and the corresponding wavelength value can be read out by scanning the sensor on the fiber grating demodulator monitoring software. The corresponding parameter setting can be performed in the sensor setting column of the software interface, and the change of the wavelength can be converted into the corresponding physical quantity change value. The strain calculation equation is:

[0101]

[0102] In the above formula: λ: strain measurement grating measurement wavelength, unit nm; λ0: strain measurement grating initial wavelength, unit nm; λ t : temperature compensation grating measurement wavelength, unit nm; λ t : temperature compensation grating initial wavelength, unit nm; a: temperature compensation grating temperature sensitivity coefficient, unit nm / ℃; b: strain measurement grating temperature sensitivity coefficient, unit nm / ℃; K: strain measurement grating displacement sensitivity coefficient, unit nm / ℃.

[0103] (3) The arrangement of the distributed vibration monitoring:

[0104] As shown in Figure 11 , the finite element dynamic analysis shows that the response to external interference is greater in the upper part of the tunnel, and the acceleration amplitude is greater. The tunnel segments clockwise include the capping block 1, the second adjacent block 3, the third standard block 6, the second standard block 5, the first standard block 4 and the first adjacent block 2. In this embodiment, the distributed vibration sensing optical cable 9 is installed on the second adjacent block 3 and the second standard block 5 by using the φ5mm fixed-point clamp in the manner of every 1.5m, and is connected to the distributed vibration demodulation host and displays the vibration abnormal information in real time on the monitoring software platform.

[0105] In this embodiment, the fire pipe 7 and the special leak cable 8 are also arranged on the tunnel segment to adapt to the actual application.

[0106] As shown in Figure 12As shown, the distributed vibration sensing optical cable 9 is designed to adopt a spiral steel pipe armored vibration optical cable, which is composed of an outer sheath 10, a stainless steel woven mesh 11, Kevlar 12, a stainless steel spiral pipe 14 and a sensing optical fiber 13 from outside to inside. The spiral steel pipe armored vibration optical cable is a sensing optical cable specially designed for a micro-vibration optical fiber sensing system, which is protected by a double-layer stainless steel armored sheath and has high-performance tensile, compression, anti-twist, rat bite, knife cutting, waterproof and moisture-proof, soft and tough characteristics, and is suitable for various harsh environments. The optical cable structure is clear, the optical fiber is protected inside a steel pipe, and is in a free state, which is very sensitive to external micro-vibration, and is an ideal detection unit for distributed vibration sensing.

[0107] In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise expressly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be a fixed connection, or a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0108] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the sentence "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0109] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A method of tunnel monitoring, characterized by, The method comprises: determining a monitoring section of the tunnel, obtaining external force distribution information of the monitoring section, and determining a maximum external force position of the segment in the monitoring section; performing finite element static simulation analysis on the whole monitoring section of the tunnel to obtain internal force distribution information of the monitoring section under external static load, wherein the finite element static simulation analysis adopts a softening modulus method to simulate the tunnel excavation process; performing finite element dynamic simulation analysis on the whole monitoring section of the tunnel to obtain acceleration distribution information of the segment at different positions under external dynamic load, wherein the finite element dynamic simulation analysis adopts a mode superposition method, and first modal analysis is performed on the whole monitoring section of the tunnel to determine fixed modes of the tunnel and the soil layer at different frequencies, and then the modes of the model at different frequencies are superimposed; based on the internal force distribution information and the acceleration distribution information, obtaining a maximum stress position of the monitoring section and a maximum acceleration position of the segment, based on the internal force distribution information, determining the maximum stress position of the monitoring section by a fourth strength criterion, and according to the acceleration distribution information, obtaining acceleration changes of multiple points of the tunnel, and determining the maximum acceleration position of the segment after comparison; respectively setting monitoring sensors at the maximum external force position, the maximum stress position and the maximum acceleration position of the segment to obtain monitoring data of the monitoring sensors; the setting of the monitoring sensors at the maximum external force position, the maximum stress position and the maximum acceleration position of the segment specifically comprises: setting a pull rod type stress / strain sensor at the maximum external force position of the segment; setting a patch stress / strain sensor at the maximum stress position of the monitoring section; and setting a vibration sensor at the maximum acceleration position of the segment.

2. The tunnel monitoring method of claim 1, wherein, Before the finite element static simulation analysis and the finite element dynamic analysis on the whole monitoring section of the tunnel, preprocessing is further included, and the preprocessing comprises: modeling and finite element mesh division of the tunnel and the soil layer, setting density, elastic modulus and damping coefficient of the tunnel and the soil layer, and then performing finite element static analysis and finite element dynamic analysis on the tunnel monitoring section.

3. The tunnel monitoring method of claim 2, wherein, the obtaining of the monitoring data of the monitoring sensors specifically comprises: obtaining monitoring data of the patch stress / strain sensor and the pull rod type stress / strain sensor and obtaining vibration sensor data.

4. The tunnel monitoring method of claim 3, wherein, the obtaining of the monitoring data of the patch stress / strain sensor and the pull rod type stress / strain sensor specifically comprises: connecting the patch stress / strain sensor and the pull rod type stress / strain sensor in series and then connecting them to a fiber grating demodulation host for demodulation; and a monitoring platform receives data of the fiber grating demodulation host through a demodulation channel.

5. The tunnel monitoring method of claim 4, wherein, the obtaining of the vibration sensor data comprises: connecting the vibration sensor to a vibration demodulation host; and a monitoring platform receives data of the vibration demodulation host.

6. The tunnel monitoring method of claim 5, wherein, after the obtaining of the monitoring data of the monitoring sensors, further comprising: the monitoring platform graphically displays data of the fiber grating demodulation host and the vibration demodulation host.

7. The tunnel monitoring method of claim 6, wherein, after the obtaining of the monitoring data of the monitoring sensors, further comprising: The monitoring platform sets a data early warning value, when the abnormal data exceeds the early warning value, based on optical time domain reflection technology, through the time when the abnormal data passes, the position of the abnormal point is given.

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