A single-point underground structure health monitoring system and method

Abstract

The present invention relates to the field of underground engineering safety technology, and is a single-point underground structure health monitoring system and method, including: a sensor group is installed on the underground structure to obtain monitoring data of the underground structure; a data acquisition and transmission system transmits the monitoring data of the sensor group to a data analysis and trend prediction system through optical fiber; the data analysis and trend prediction system receives the signal data of the sensor group for analysis and trend prediction processing to obtain processing results; a state evaluation and alarm system receives the processing results of the data analysis and trend prediction system to perform state evaluation, and determines whether to issue an early warning based on the state evaluation results; and, internally regulates the underground structure based on the level of the early warning. This solution effectively reduces the operation and maintenance costs of the underground structure throughout its life cycle, and maximizes the service life of the structure; at the same time, through long-term monitoring of the underground structure and the external environment, it provides protection for the safety of structural operation and maintenance.

Description

Technical Field

[0001] The present invention relates to the field of underground engineering safety technology, and in particular to a single-point underground structure health monitoring system and method. Background Art

[0002] In recent years, subway construction has developed rapidly, and there are countless underground stations under construction and already built. At present, construction monitoring or third-party monitoring is mainly adopted for the construction period of underground stations to feedback the structural safety status during the construction period and ensure the safety of the structure and surrounding buildings during the construction process. However, there is no mature health monitoring and early warning system for the completed underground stations. It is impossible to provide reasonable and accurate feedback on the safety status of underground structures during the operation period after completion, especially under accidental conditions (such as earthquakes, accidental overloads, etc.), and it is impossible to provide first-hand support data for the maintenance of subway station structures during the operation period, making it difficult to fundamentally solve some problems exposed during the operation period.

[0003] The structural system of subway stations is complex, and the requirements for structural safety control are high. The geological conditions and surrounding environment are complex, especially the engineering activities around the stations (loading, piling, tunnel crossing) are difficult to predict, which can easily induce structural diseases. The long-term operation of train loads can easily cause the main structure of the station to be subjected to varying degrees of loading and unloading cycle effects, and the structural fatigue damage characteristics are obvious, which is extremely unfavorable to its deformation and long-term stability. In addition, accidental effects such as earthquakes may occur, and the safety status of the structure also needs to be reasonably evaluated.

[0004] At present, structural monitoring is mainly carried out in the form of construction monitoring or third-party monitoring during the construction period of underground stations, providing feedback on the safety of the structure and surrounding buildings during the construction process. However, there is no mature health monitoring system for completed underground stations, and it is impossible to provide reasonable and accurate feedback on the safety status of underground structures during the operation period after completion, especially under accidental conditions (such as earthquakes, accidental overloading, piling, tunnel crossing, karst, etc.) or structural diseases induced by fatigue damage caused by train operation loading and unloading cycles. It is also impossible to provide first-hand support data for the structural maintenance of subway stations during the operation period, making it difficult to fundamentally solve some problems exposed during the operation period.

[0005] In addition, the few existing structural monitoring systems also have the following shortcomings: they rely unilaterally on structural monitoring data for analysis and cannot be compared with the design results of structural numerical analysis calculations. Summary of the invention

[0006] The present invention provides a single-point underground structure health monitoring system and method, which solves the above-mentioned technical problem of imperfect structural health monitoring and early warning in underground stations.

[0007] In order to solve the above technical problems, the present invention provides a single-point underground structure health monitoring system, comprising: a site structure, a sensor group installed on the site structure, a data acquisition and transmission system, a data analysis and trend prediction system, and a status assessment and alarm system;

[0008] The sensor group is installed on the underground structure to obtain monitoring data of the underground structure;

[0009] The data acquisition and transmission system is used to transmit the monitoring data of the sensor group to the data analysis and trend prediction system through optical fiber;

[0010] The data analysis and trend prediction system is used to receive the signal data of the sensor group for analysis and trend prediction processing to obtain processing results;

[0011] The status assessment and alarm system is used to receive the processing results of the data analysis and trend prediction system to perform status assessment, and determine whether to issue an early warning based on the status assessment results; and to perform internal regulation of the underground structure based on the level of the early warning.

[0012] Optionally, the warning levels include level I warning situation, level II warning situation and level III warning situation;

[0013] When the actual monitoring value is not greater than 50% of the alarm index of each monitoring item, the output is level I warning and normal operation;

[0014] When the actual monitoring value is between 50% and 70% of the alarm index of each monitoring item, a Level II warning situation is output;

[0015] When the actual monitoring value is greater than 70% of the alarm index of each monitoring item, a Level III warning situation is output and it is determined to be a critical alarm area.

[0016] Optionally, the status assessment and alarm system is used to notify the staff corresponding to the area of ​​the underground structure that does not require manual maintenance according to preset rules, and to carry out collaborative maintenance in the area that requires manual maintenance.

[0017] Optionally, the sensor group is installed at each monitoring section of the site structure;

[0018] The sensor group includes a fiber grating thermometer, a fiber grating soil pressure box for monitoring the external soil pressure of the structure, a fiber grating piezometer for monitoring the external water pressure of the structure, a fiber grating embedded strain gauge for monitoring the concrete stress of the structure, a fiber grating accelerometer for monitoring the vibration of the structure, and a fiber grating surface pull rod type crack meter for monitoring the settlement of the structure.

[0019] Optionally, the monitoring section includes areas with complex structural systems, areas with weak structural strength and sections with complex surrounding environments.

[0020] Optionally, the complex areas of the structural system include areas of sudden stiffness changes and areas of structural discontinuity, the areas of weak structural strength include areas of peak force and areas of minimum bearing capacity, and the complex sections of the surrounding environment include areas of poor geology and areas where geological conditions have changed.

[0021] Optionally, the earth pressure box is a rigid earth pressure box, and the rigidity of the rigid earth pressure box matches the rigidity of the concrete of the underground structure.

[0022] The present invention also provides a single-point underground structure health monitoring method, comprising:

[0023] The sensor groups are respectively installed on the underground structure to obtain monitoring data of the underground structure;

[0024] The data analysis and trend prediction system receives the signal data of the sensor group to perform analysis and trend prediction processing to obtain processing results;

[0025] The status assessment and alarm system receives the processing results of the data analysis and trend prediction system to conduct status assessment, and determines whether to issue an early warning based on the status assessment results; and internally regulates the underground structure based on the level of the early warning.

[0026] Optionally, wavelength division multiplexing technology can be used to connect multiple fiber grating sensors in series on one optical fiber, and combined with the construction technology and procedures of the enclosure structure and the main structure, the optical cable routing and equipment integration design can be carried out in accordance with the principle of considering the feasibility of construction without affecting the bearing performance of the main structure.

[0027] Optionally, the optical cable routing is protected by a stainless steel cable trough and fixed to the side wall of the structure by expansion bolts. When passing through the main structure, a PVC wire conduit is pre-buried at the corresponding position for the optical cable routing.

[0028] Beneficial effects:

[0029] The present invention provides a single-point underground structure health monitoring system and method, which uses an advanced fiber grating sensor group to collect monitoring information, and through relevant data collection, transmission, analysis and prediction, evaluates and warns the structural health information, so as to facilitate timely maintenance and treatment measures. It can achieve: (1) dynamically monitor the working status of the underground structure and reasonably evaluate the health status of the underground structure; (2) assist in operation and maintenance decision-making, and extend the service life of the underground structure; (3) accumulate structural design, construction and maintenance experience of the underground structure.

[0030] This solution is applicable to projects such as urban rail transit underground structures and prefabricated underground structures. It has certain creativity and practicality and has good prospects for promotion and application.

[0031] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. The specific implementation of the present invention is given in detail by the following embodiments and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 It is a schematic diagram of the architecture of the single-point underground structure health monitoring system and method of the present invention;

[0034] Figure 2 A schematic diagram of the monitoring standard section and measurement point layout of the single-point underground structure health monitoring system and method of the present invention;

[0035] Figure 3 It is a plan view of the monitoring optical cable routing of the single-point underground structure health monitoring system and method of the present invention;

[0036] Figure 4 It is a schematic cross-sectional diagram of an optical cable routing for monitoring the external earth pressure and water pressure of a structure in the single-point underground structure health monitoring system and method of the present invention;

[0037] Figure 5 It is a schematic cross-sectional view of an optical cable routing for monitoring structural concrete stress in the single-point underground structure health monitoring system and method of the present invention;

[0038] Figure 6 It is a schematic cross-sectional view of the optical cable routing for monitoring structural vibration of the single-point underground structure health monitoring system and method of the present invention;

[0039] Figure 7 This is a schematic cross-sectional diagram of the optical cable routing for structural settlement monitoring of the single-point underground structure health monitoring system and method of the present invention.

[0040] Explanation of the reference numerals: borehole 1, monitoring section 2, structural wall 3, structural beam 4, structural column 5, temporary collection box 6, status assessment and alarm system 7, main transmission optical cable 8, tunnel 9, fiber Bragg grating soil pressure box 10, fiber Bragg grating piezometer 11, fiber Bragg grating embedded strain gauge 12, fiber Bragg grating accelerometer 13, fiber Bragg grating surface pull rod crack meter 14. DETAILED DESCRIPTION

[0041] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0042] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0044] like Figures 1 to 7 As shown, the present invention provides a single-point underground structure health monitoring system, including: a site structure, a sensor group installed on the site structure, a data acquisition and transmission system, a data analysis and trend prediction system, and a status assessment and alarm system;

[0045] The sensor group is installed on the underground structure to obtain monitoring data of the underground structure;

[0046] The data acquisition and transmission system is used to transmit the monitoring data of the sensor group to the data analysis and trend prediction system through optical fiber;

[0047] The data analysis and trend prediction system is used to receive the signal data of the sensor group for analysis and trend prediction processing to obtain processing results;

[0048] The status assessment and alarm system is used to receive the processing results of the data analysis and trend prediction system to perform status assessment, and determine whether to issue an early warning based on the status assessment results; and to perform internal regulation of the underground structure based on the level of the early warning.

[0049] The specific scheme of the single-point underground structure health monitoring system is as follows:

[0050] (1) Determination of monitoring items

[0051] The monitoring items should be able to directly or indirectly reflect the actual stress and deformation state of the structure and serve the structural safety evaluation and early warning. The monitoring items include deformation, stress-strain, leakage, groundwater level, temperature, fatigue, etc.

[0052] (2) Monitoring sections and measurement point layout

[0053] The monitoring sections should focus on areas with weak soil layers, differential distribution, obvious adverse geological effects such as karst, complex structural systems, and complex surrounding environments. The layout of section measurement points should be combined with the stress-deformation performance of the structure, and the internal forces and deformations of the structure should be large or representative parts should be selected for monitoring. Based on numerical analysis and calculation, the internal force, displacement control value and control point are obtained, and then the sensor group is arranged at the corresponding point. Specifically, sensor group 1 to sensor group n should be mainly replaceable components, supplemented by embedded, non-replaceable components. The instrument selection should determine the range, accuracy and long-term stability requirements according to the monitoring purpose, while taking into account the convenience of installation and maintenance.

[0054] (3) Monitoring methods and instrument requirements

[0055] Structural health monitoring should choose automated monitoring to reduce the impact of manual interference on accuracy and labor costs, and manual monitoring can be used as a supplement during the construction period.

[0056] (4) Data collection and transmission

[0057] During the operation period, automatic real-time data collection is adopted. All fiber grating sensors are introduced into the monitoring station using multi-core main transmission optical cables, so that all optical path signals can collect data in the monitoring station and realize centralized monitoring of the system. The remote real-time transmission of monitoring data is realized by setting up a network system, and dynamic management of monitoring data is realized.

[0058] (5) Data analysis and prediction

[0059] Based on the monitoring data, the site structure health status is intelligently analyzed to predict possible trends in structural health status changes.

[0060] (6) Status assessment and alarm

[0061] According to the data analysis and prediction of the monitoring system, the structural health status is evaluated and early warning is issued in time. After the site health monitoring system issues an early warning, it is fed back to the site maintenance personnel for processing. The monitoring system provides data support for the decision-making of response measures, and internally regulates the underground structure according to the level of early warning, fully, reasonably and efficiently deploys all maintenance personnel inside the underground structure, so as to eliminate safety hazards in a timely manner.

[0062] For optional solutions, the warning levels include level I warning, level II warning and level III warning; when the actual monitoring value is not greater than 50% of the alarm index of each monitoring item, the output is level I warning, and normal operation; when the actual monitoring value is between 50% and 70% of the alarm index of each monitoring item, the output is level II warning; when the actual monitoring value is greater than 70% of the alarm index of each monitoring item, the output is level III warning, and it is determined to be a critical alarm area. According to the specific situation of the warning, a structural health status assessment is carried out and a timely warning is issued. In combination with the requirements of hierarchical management, for level I, II and III warning situations, after the status assessment and alarm system prompts the warning, it is fed back to the site maintenance personnel for processing.

[0063] An optional solution is to notify the corresponding staff in the area of ​​the underground structure that does not require manual maintenance according to the preset rules, and go to the area that requires manual maintenance for collaborative maintenance. The preset rules include the principle of geographical proximity and the principle of similar technical trades. When an early warning is generated, the nearby maintenance personnel closest to the area of ​​the underground structure where the early warning occurs can collaborate with the maintenance personnel in the corresponding area of ​​the underground structure for maintenance. This is the principle of proximity. Early warnings of different sensor types can notify maintenance personnel of similar or identical sensors to perform collaborative manual maintenance. This is the principle of similar technical trades.

[0064] An optional solution is that the sensor group is installed at each monitoring section 2 of the underground structure, and the state assessment and alarm system is connected to the sensor group via optical fiber communication;

[0065] The sensor group includes a fiber Bragg grating thermometer, a fiber Bragg grating earth pressure box 10 for monitoring the external earth pressure of the structure, a fiber Bragg grating piezometer 11 for monitoring the external water pressure of the structure, a fiber Bragg grating embedded strain gauge 12 for monitoring the concrete pressure of the structure, a fiber Bragg grating accelerometer 13 for monitoring the vibration of the structure, and a fiber Bragg grating surface rod type joint meter 14 for monitoring the settlement of the structure. The sensor group includes not only those listed above, but also can be selected according to the actual engineering monitoring needs.

[0066] An optional solution, the data analysis and trend prediction system is used to perform abnormal data identification, data smoothing, reliability analysis and trend prediction on the signal data of the monitoring instrument; the state assessment and alarm system is used to formulate control standards and indicator warning standards for structural deformation and cracking in combination with the analysis of the evolution process of the structural stress performance, propose a monitoring classification and early warning management level, and implement a three-level alarm system.

[0067] In this embodiment, it is very necessary to establish a health monitoring function to ensure safety for station structures such as subway stations, especially those in karst geology. The data collected by each sensor group in the subway station is transmitted to the status evaluation and alarm system through optical fiber. The status evaluation and alarm system analyzes the data to obtain trend prediction, and then evaluates the status of each monitoring section 2. If there is an abnormality, a corresponding alarm is issued, and reverse feedback control or manual maintenance is performed.

[0068] Beneficial effects:

[0069] (1) Dynamically monitor the working status of underground structures and rationally evaluate the health status of underground structures.

[0070] Conduct full-process monitoring of underground structures, dynamically and in real time grasp the working environment, stress-deformation state, and development and evolution trends of underground structures, reveal the evolution of structural stress-deformation and bearing performance during operation, verify the monitoring data with theoretical analysis and numerical calculations, promptly diagnose various abnormal conditions that occur during the operation of underground structures, comprehensively evaluate the health status of underground structures, and provide reliable data support for related data analysis.

[0071] (2) Assist in operation and maintenance decision-making and extend the service life of underground structures.

[0072] Provide data support for the formulation of reasonable, proactive and preventive maintenance measures, thereby effectively reducing the operation and maintenance costs of underground structures throughout their life cycle and maximizing the service life of underground structures.

[0073] (3) Accumulate experience in underground structure design, construction and maintenance.

[0074] The underground structure projects pass through complex geology, hydrology and surrounding environment, which poses a huge challenge to the long-term service performance of underground structures. Through long-term monitoring of underground structures and external environment, we can accumulate engineering experience and provide guarantee for the safety of underground structure operation and maintenance.

[0075] For optional solutions, the items monitored by the sensor group should be able to directly or indirectly reflect the actual internal force state and deformation (displacement) state of the structure, and serve the structural safety evaluation and early warning. The monitoring items include the external load, internal force and deformation of the structure. The monitoring section 2 and the arrangement of the measuring points should be implemented based on the main principle of striving to achieve "complete monitoring, stable performance and optimal cost performance". The monitoring section 2 should focus on the following:

[0076] 1) Complex areas of the structural system, such as areas with sudden stiffness changes and areas of structural discontinuity;

[0077] 2) Weak structural strength areas, such as peak stress areas, areas with minimum bearing capacity, etc.;

[0078] 3) Areas with complex surrounding environments, such as areas with poor geological conditions and areas where geological conditions have changed.

[0079] An optional solution, the data acquisition and transmission system is used to collect data from the sensor group and transmit it to the data analysis and trend analysis system through optical fiber, specifically including:

[0080] 1) It should be possible to collect data in real time, regularly or irregularly according to needs;

[0081] 2) When different or similar types of data need to be analyzed, the relevant data should be collected simultaneously;

[0082] 3) When collecting data, it is advisable to pre-process the signal. For different signals with large differences in signal strength magnitude, signal isolation should be strictly performed before collection.

[0083] The data of the sensor group is finally transmitted to the status evaluation and alarm system through optical fiber. Sensors are arranged on the structural plates, structural walls 3, structural beams 4 and structural columns 5 corresponding to the monitoring section 2. The sensors first transmit the signals to the nearest temporary collection box 6, and then transmit them to the status evaluation and alarm system 7 through the main transmission optical cable 8 for analysis.

[0084] As an optional solution, the complex areas of the structural system include areas of sudden stiffness changes and areas of structural discontinuity; the areas of weak structural strength include areas of peak stress and areas of minimum bearing capacity; and the complex sections of the surrounding environment include areas of poor geology and areas where geological conditions have changed.

[0085] (1) Selection of standard sections: Based on previous engineering experience and relevant research results, the vulnerable parts of shallow buried standard section subway stations are the top and bottom of the center column, the junction between the middle plate and the side wall, and the junction between the middle plate and the center column. Structural stress is monitored at the top and bottom of the column and other structurally weak parts.

[0086] (2) Selection of complex sections of structural systems: Based on common sense of mechanics and previous engineering experience, there is generally a large stress concentration at the location of the variable section of the structure. According to the simulation numerical calculation results, the compressive stress of the main concrete and the stress of the steel bars of the subway station structure are within the design value range of the material strength, while the tensile stress of the concrete at the location of the variable section of the station is large and close to the tensile strength of the material. The dominant control factor of the structure under the standard load combination is the tensile cracking of the concrete. Therefore, the variable section is selected as the structural durability monitoring section, and the measuring point is selected at the location where the tensile stress is large in the numerical calculation results.

[0087] (3) Weak structural strength area: Due to the great difference in structural form between the station and the tunnel line section, and the different foundation treatment methods, the tunnel-structure connection is prone to large differential settlement during the later daily operation period. The connection is subjected to large tensile force, which causes concrete cracking at the joint and other defects. Therefore, the junction of the station and the subway line is selected as the differential settlement observation section, and joint meters are arranged to observe the tunnel-junction differential settlement.

[0088] (4) Selection of sections with complex geological environments: The soil above the bottom of the station foundation pit is used as the judgment range, and water and soil pressure sensors are arranged on the periphery of the retaining structure, bottom plate, and side wall.

[0089] Among them, the external soil pressure and water pressure of the structure are the direct factors that lead to deformation and damage of the main structure. By monitoring the external soil pressure and water pressure of the main structure of the station, the stress state of the structure can be directly grasped, providing basic data for structural bearing capacity and deformation analysis. At the same time, the impact of nearby construction projects on the structure can be directly understood, and early warning can be given.

[0090] Therefore, monitoring section 2 should focus on selecting sections with weak soil layers, differential distribution, obvious adverse geological effects such as karst, complex structural systems, and complex surrounding environments. The layout of section measurement points should be combined with the stress and deformation performance of the structure, and select the parts with large internal forces and deformation or representative parts for monitoring. The following is an explanation of the layout of monitoring points in different parts:

[0091] (1) External water and soil pressure of the structure

[0092] The water and soil pressure outside the structure directly determines the internal force level of the structure. The measuring points are mainly arranged at the corresponding representative positions outside the enclosure structure, top plate and bottom plate. The equipment outside the enclosure structure is placed by drilling 1. The distance between drilling 1 and the enclosure structure L is generally 1000mm. The size of drilling 1 can be The equipment outside the enclosure structure is fixed on a steel structure made of angle steel, protected by PVC pipes and fixed with cable ties. It is led into the main structure through a protective sleeve on the ground, and the equipment is fixed in place according to the designed dimensions.

[0093] (2) Structural concrete stress

[0094] Concrete stress monitoring section 2 should be as consistent as possible with the external pressure monitoring of the structure to facilitate mutual correlation and verification. It is mainly arranged on key beams, columns, walls, and plates, with a pair of measuring points (one inside and one outside) arranged at each location.

[0095] (3) Structural vibration response

[0096] The vibration of long-term train operation may have different degrees of influence on the stress and deformation of the main structure (beams, columns, walls, and plates). Accelerometers should be installed on the structures on both sides of the train to monitor the vibration load. The measurement points are mainly arranged on key columns and walls that are greatly affected by the train vibration load to study the transmission law of the vibration load from the roadbed to the walls, columns, and plates. This element can also be used to monitor earthquake vibration.

[0097] (4) Structural settlement

[0098] Focus on the changes in the form of the superstructure, uneven distribution of the longitudinal soil layer, sudden changes in the local load of the station caused by potential engineering activities in the external environment, etc., which may cause differential settlement of the station structure. The spacing and position of the settlement observation points are determined comprehensively based on geological conditions and the causes of settlement.

[0099] Beneficial effects: The advanced fiber grating sensor group is used to collect monitoring information, and through relevant data collection, transmission, analysis and prediction, the structural health information is evaluated and warned, which facilitates timely maintenance and treatment measures. Through the construction of this intelligent monitoring and early warning system, it can achieve: (1) Dynamic monitoring of the working status of subway stations and reasonable evaluation of the health status of the main structure of the station; (2) Assisting in operation and maintenance decision-making to extend the service life of the main structure of the station; (3) Accumulating experience in the design, construction and maintenance of the main structure of the station.

[0100] Through comparison (whether the location can be determined, sensitivity, measurement difficulty, etc.), the recommended indicators for damage evaluation of health monitoring are proposed. Combined with the analysis of the evolution process of structural stress performance, the control standards and indicator warning standards for structural deformation and crack damage are formulated, and the monitoring classification and warning management level is proposed, and a three-level alarm system is implemented. The first level is the green zone, the second level is the orange zone, and the third level is the red zone, as shown in the table below.

[0101] Monitoring data classification management table

[0102]

[0103] Note: Un——alarm index of each monitoring item; U0——actual monitoring value.

[0104] Taking a typical monitoring project as an example, various fiber Bragg grating sensors are used to form a sensor group, and the strain sensing characteristics of the fiber Bragg grating are used or used as a test carrier to generate data information of various test projects. The sensor statistics are shown in the following table. Replaceable devices are used as much as possible during the setting process.

[0105] Sensor Group Statistics

[0106]

[0107] The following explains the installation methods of different sensor groups one by one:

[0108] (1) External earth pressure of the structure:

[0109] The installation sequence of the fiber grating earth pressure box 10 is: determine the installation location → install the embedded steel plate base → install the earth pressure box → lay the optical cable → fusion splice the optical fiber and connect the sensors in series → lead out the optical cable and check the passage.

[0110] (2) External water pressure of the structure

[0111] The installation sequence of the fiber Bragg grating osmometer 11 is: determine the installation location → protect and fix the osmometer → lay the optical cable → fusion splice the optical fiber and connect the sensors in series → lead out the optical cable and check the passage.

[0112] (3) Structural concrete stress

[0113] The installation sequence of the fiber Bragg grating embedded strain gauge 12 is: determine the installation location → strain gauge installation → optical cable laying → optical fiber fusion splicing, sensor series connection → optical cable lead-out, path inspection.

[0114] (4) Structural vibration

[0115] The fiber grating accelerometer 13 is installed on the wedge-shaped pad. After the cables are arranged, expansion screws are driven into the surrounding concrete to fix the cables. Finally, the sensor cables are connected to the data collector.

[0116] (5) Structural settlement

[0117] A fiber grating surface pull-rod joint meter 14 is used to monitor differential settlement. The device mainly includes a joint meter and a connecting angle steel. The joint meter is installed parallel to the direction of the joint to be measured, and the angle steel is installed perpendicular to the direction of the joint to be measured. One end of the angle steel is fixed to the structure by bolts, and the other end is fixed to the joint meter by bolts. When differential settlement occurs in the structures on both sides of the joint, the connecting angle steel drives the joint meter to expand and contract, thereby obtaining the differential settlement of the structures on both sides of the joint.

[0118] As an optional solution, wavelength division multiplexing technology can be used to connect multiple fiber grating sensors in series on one optical fiber. To avoid cross-overlapping of the working wavelengths of each sensor, there is a limit on the number of instruments connected in series. In view of the additional loss of optical signals caused by optical fiber bending, welding, etc., a certain wavelength redundancy should be set. At the same time, considering the convenience of construction, in principle, the number of single-channel series sensors should not exceed 8. The specific optical cable routing design should be combined with the construction technology and procedures of the enclosure structure and the main structure, and the optical cable routing and equipment integration design should be carried out in accordance with the principle of considering the feasibility of construction and not affecting the bearing performance of the main structure.

[0119] Since the core structure of the optical cable is a SiO2 fiber core, in order to avoid the monitoring system failure caused by the breakage of the optical cable, special attention should be paid during the laying and welding of the optical cable. It is strictly forbidden to pull it hard, bend it excessively, or use violent construction, and the optical cable should be well protected. The main precautions are as follows:

[0120] (1) Optical cables inside concrete: When the structure is poured, the optical cables are laid along the steel cage. The leads should be in order. Small angle bends are strictly prohibited, and the bending radius should not be less than 5 cm. To avoid the formation of water seepage channels, multiple water-swelling rubber water stop rings are installed along the optical cables, especially at the connection points between the sensor and the optical cable, the optical cable corners, and the connection points between the optical cable and the terminal box. The optical cables should not be led out at right angles.

[0121] (2) Fiber fusion splicing: After the fiber fusion splicing is completed, a metal tube needs to be added outside the heat shrink tube to protect the fusion section of the optical cable, and the two ends need to be fixed with rubber sleeves.

[0122] (3) Optical cable in the terminal box: The pre-buried sensor leads to the terminal box. To facilitate rapid data collection during the construction period, FC / APC connectors are installed at the ends of the optical cables and waterproof protection is provided. The redundant optical cables in the terminal box are coiled inside and sealed with expanded foam filling and waterproof tape wrapped around the outside.

[0123] (4) Protection of optical cables outside the structure: Optical cables leading outside the structure should be protected by stainless steel cable troughs and fixed to the side walls of the structure with expansion bolts. When passing through the main structure, PVC wire conduits should be pre-buried at the corresponding locations for optical cable routing.

[0124] (5) Protection of the main transmission optical cable 8: The main transmission optical cable 8 is laid on the side wall of the station structure and tied and fixed.

[0125] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A single-point underground structure health monitoring system, characterized in that: include: Site structure, sensor cluster installed on said site structure, data acquisition and transmission system, data analysis and trend prediction system, status assessment and alarm system; The sensor group is installed on the underground structure to obtain monitoring data of the underground structure; the sensor group is installed at each monitoring section of the site structure; the sensor group includes a fiber Bragg grating thermometer, a fiber Bragg grating soil pressure box for monitoring the external soil pressure of the structure, a fiber Bragg grating piezometer for monitoring the external water pressure of the structure, a fiber Bragg grating embedded strain gauge for monitoring the concrete stress of the structure, a fiber Bragg grating accelerometer for monitoring the vibration of the structure, and a fiber Bragg grating surface pull rod type joint meter for monitoring the settlement of the structure; the monitoring section includes a complex structural system area, a weak structural strength area, and a complex surrounding environment section; The data acquisition and transmission system is used to transmit the monitoring data of the sensor group to the data analysis and trend prediction system through optical fiber; The data analysis and trend prediction system is used to receive the signal data of the sensor group for analysis and trend prediction processing to obtain processing results; The state assessment and alarm system is used to receive the processing results of the data analysis and trend prediction system to perform state assessment and determine whether to issue an early warning based on the state assessment results; and, internal regulation of underground structures according to the level of warning; The selection process of the monitoring section includes: Selecting a standard section for monitoring structural stress; the standard section at least includes the top and bottom of the middle column, the junction between the middle plate and the side wall, the junction between the middle plate and the middle column, and one of the top and bottom of the column; Select a complex section of the structural system for monitoring stress; the complex section of the structural system includes at least a variable section; the measuring point of the complex section of the structural system is selected at a position where the tensile stress is greater than a preset threshold in the numerical calculation result; Selecting a structurally weak area for monitoring differential settlement; the structurally weak area at least includes a junction between a station and a subway line; A section with a complex geological environment is selected for monitoring water and soil pressure; the section with a complex geological environment at least includes a retaining structure, a bottom plate, and the periphery of the side walls.

2. The single-point underground structure health monitoring system according to claim 1, characterized in that: The warning levels include level I warning situation, level II warning situation and level III warning situation; When the actual monitoring value is not greater than 50% of the alarm index of each monitoring item, the output is level I warning and normal operation; When the actual monitoring value is between 50% and 70% of the alarm index of each monitoring item, a Level II warning situation is output; When the actual monitoring value is greater than 70% of the alarm index of each monitoring item, a Level III warning situation is output and it is determined to be a critical alarm area.

3. The single-point underground structure health monitoring system according to claim 1, characterized in that: The status assessment and alarm system is used to notify the staff corresponding to the area of ​​the underground structure that does not require manual maintenance according to preset rules, and to carry out collaborative maintenance in the area that requires manual maintenance.

4. The single-point underground structure health monitoring system according to claim 1, characterized in that: The complex areas of the structural system include areas of sudden stiffness changes and areas of structural discontinuity; the areas of weak structural strength include areas of peak stress and areas of minimum bearing capacity; and the complex surrounding environment sections include areas of poor geology and areas where geological conditions have changed.

5. The single-point underground structure health monitoring system according to claim 1, characterized in that: The earth pressure box is a rigid earth pressure box, and the rigidity of the rigid earth pressure box matches the rigidity of the concrete of the underground structure.

6. A monitoring method for a single-point underground structure health monitoring system as claimed in any one of claims 1 to 5, characterized in that: include: The sensor groups are respectively installed on the underground structure to obtain monitoring data of the underground structure; The sensor group is installed at each monitoring section of the site structure; the sensor group includes a fiber Bragg grating thermometer, a fiber Bragg grating soil pressure box for monitoring the external soil pressure of the structure, a fiber Bragg grating piezometer for monitoring the external water pressure of the structure, a fiber Bragg grating embedded strain gauge for monitoring the stress of the structural concrete, a fiber Bragg grating accelerometer for monitoring the vibration of the structure, and a fiber Bragg grating surface rod type joint meter for monitoring the settlement of the structure; the monitoring section includes a complex structural system area, a weak structural strength area, and a complex surrounding environment section; The data analysis and trend prediction system receives the signal data of the sensor group to perform analysis and trend prediction processing to obtain processing results; Receive the processing results of the data analysis and trend prediction system through the status assessment and alarm system to conduct status assessment and determine whether to issue an early warning based on the status assessment results; and, internal regulation of underground structures according to the level of warning; The selection process of the monitoring section includes: Selecting a standard section for monitoring structural stress; the standard section at least includes the top and bottom of the middle column, the junction between the middle plate and the side wall, the junction between the middle plate and the middle column, and one of the top and bottom of the column; Select a complex section of the structural system for monitoring stress; the complex section of the structural system includes at least a variable section; the measuring point of the complex section of the structural system is selected at a position where the tensile stress is greater than a preset threshold in the numerical calculation result; Selecting a structurally weak area for monitoring differential settlement; the structurally weak area at least includes a junction between a station and a subway line; A section with a complex geological environment is selected for monitoring water and soil pressure; the section with a complex geological environment at least includes a retaining structure, a bottom plate, and the periphery of the side walls.

7. The intelligent monitoring and early warning method of a single-point underground structure health monitoring system according to claim 6 is characterized in that: Wavelength division multiplexing technology is used to connect multiple fiber grating sensors in series on one optical fiber. Combined with the construction technology and procedures of the enclosure structure and the main structure, the optical cable routing and equipment integration design are carried out in accordance with the principle of considering the feasibility of construction without affecting the bearing performance of the main structure.

8. The intelligent monitoring and early warning method of a single-point underground structure health monitoring system according to claim 7 is characterized in that: The optical cable routing is protected by a stainless steel cable duct and fixed to the side wall of the structure by expansion bolts. When passing through the main structure, a PVC threading pipe is pre-buried at the corresponding position for the optical cable routing.

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