Method and system for health monitoring and early warning in operation period of tunnel passing through active fault

Abstract

The invention provides an active fault crossing tunnel operation period health monitoring and early warning method and system, and relates to the technical field of tunnel monitoring, and the method comprises the steps: measuring the fault dislocation amount and dislocation displacement mode of an active fault crossing tunnel, and carrying out the finite element numerical simulation, and obtaining a finite element numerical simulation result; monitoring data of the active fault crossing tunnel are collected through the determined control indexes, engineering verification is carried out on a finite element numerical simulation result, and parameters of the finite element numerical simulation result are adjusted; basic physical and mechanical parameters of a tunnel are obtained, a reinforced concrete bearing capacity characteristic curve is obtained in combination with a tunnel structure evaluation method, and an early warning threshold value of the tunnel structure is determined; and in combination with the collected monitoring data, the adjusted finite element numerical simulation result and an early warning threshold value, obtaining an early warning result of the active fault crossing tunnel structure. According to the technical scheme, the accuracy of an early warning result can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of tunnel monitoring, and particularly to a method and system for health monitoring and early warning during the operation period of a tunnel crossing an active fault zone. Background Art

[0002] Many highway, railway tunnels, and water diversion tunnels inevitably cross active fault zones. The continuous creep and displacement of active fault zones can cause serious damage to the safety of tunnel linings during the operation period and pose a serious threat to personnel safety. The displacement of fault fracture zones is often irregular, and the changes at different positions are completely different.

[0003] Therefore, it is very necessary to master the displacement of active faults and their impact on tunnels. This is an important scientific problem that cannot be avoided in engineering research, design, and operation, and it is also an important technical problem that urgently needs to be solved in the construction of transportation tunnels crossing active faults in the western region.

[0004] Accurately identifying the displacement amount and distribution pattern of active faults is crucial for the selection of engineering measures and the operation of tunnel structures. For fault displacement, laser rangefinders, observation stations, GNSS, or deep hole displacement monitoring methods are mostly used. However, at present, during the operation stage of tunnel structures, there is no good method for identifying the displacement amount and distribution pattern along the thickness direction of active faults.

[0005] The corresponding tunnel structure safety assessment and early warning methods still need to be further improved. Therefore, there is an urgent need for a tunnel monitoring and early warning method with high sensitivity, simplicity, speed, and good stability. In addition, the application of the method combining numerical simulation - monitoring feedback - model correction, theoretical derivation, and engineering verification in tunnel structure monitoring and early warning needs to be further enhanced. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and system for health monitoring and early warning during the operation period of a tunnel crossing an active fault zone in order to solve the problem that the existing tunnel monitoring and early warning methods cannot accurately monitor and early warn the tunnel structure.

[0007] The above object of the present application is achieved through the following technical solutions: S1: Measure the fault displacement amount and displacement pattern of a tunnel crossing an active fault zone; S2: Input the fault displacement amount and displacement pattern as boundary conditions, and combine with the concrete damage plasticity model to perform three-dimensional stratum - structure method finite element numerical simulation to obtain the finite element numerical simulation results; S3: Collect monitoring data according to the control indicators of the tunnel crossing the active fault zone; the control indicators include: bending moment, axial force, and the convergence deformation of the tunnel structure; S4: Engineering verification of the finite element numerical simulation results is carried out through the collected monitoring data, and the parameters of the finite element numerical simulation results are adjusted; S5: Obtain the basic physical and mechanical parameters of the tunnel, and combine with the tunnel structure evaluation method to obtain the bearing capacity characteristic curve of reinforced concrete and determine the warning threshold of the tunnel structure; S6: Combine the collected monitoring data, the adjusted finite element numerical simulation results and the warning threshold to obtain the warning result of the tunnel structure crossing the active fault.

[0008] Optionally, step S5 includes: Discriminate the stress mode of the rectangular cross-section of reinforced concrete; the stress modes include: the first stress mode, the second stress mode and the third stress mode; Through the stress mode and the basic physical and mechanical parameters, combined with the strength calculation formula of the reinforced concrete flexural member, the cross-section strength calculation formula of the large eccentric compression member and the cross-section strength calculation formula of the small eccentric compression member, obtain the bearing capacity characteristic curve of reinforced concrete under different stress modes; Determine the warning threshold of the tunnel structure through the bearing capacity characteristic curve of reinforced concrete; The warning thresholds include: the first warning threshold, the second warning threshold and the third warning threshold.

[0009] Optionally, the calculation formula for the strength of the reinforced concrete flexural member is as follows:

[0010] Wherein, represents the safety factor; represents the bending moment; represents the ultimate flexural compressive strength of concrete; represents the width of the rectangular cross-section; represents the height of the concrete compression zone; represents the standard value of the tensile or compressive strength of the steel bar; represents the cross-sectional area of the compression zone steel bar; represents the effective height of the cross-section; represents the distance from the centroid of the tensile or compressive steel bar to the nearest edge of the cross-section respectively; The calculation formula for the cross-section strength of the large eccentric compression member is as follows:

[0011] Wherein, represents the axial force; represents the cross-sectional area of the tensile zone steel bar; The calculation formula for the cross-section strength of the small eccentric compression member is as follows:

[0012] Among them It represents the distance from the centroid of the tensile reinforcement or compressive reinforcement to the action point of the axial force.

[0013] Optionally, the first stress mode of the reinforced concrete rectangular section is as follows: When ; Let the safety factor K of the calculation formula for the strength of the reinforced concrete flexural member and the calculation formula for the section strength of the large eccentric compression member be 1; From the section strength of the large eccentric compression member,

[0014] Substitute Equation (1) into the calculation formula for the strength of the reinforced concrete flexural member, and in the tunnel structure Get

[0015] At the same time, M should satisfy the following conditions:

[0016] Input the basic physical and mechanical parameters into Equation (2) and Equation (3) to obtain the characteristic curve of the bearing capacity of the reinforced concrete under the first stress mode, and determine the first warning threshold.

[0017] Optionally, the second stress mode of the reinforced concrete rectangular section is as follows: When ; mainly consider that the tension zone of the member is damaged by tension; It is known that , Among them It represents the distance from the neutral axis to the action point of the axial force; It represents the section height; Let the safety factor K in the calculation formula for the section strength of the small eccentric compression member be 1, and we can get

[0018] At the same time, M and N should satisfy the following conditions:

[0019] Input the basic physical and mechanical parameters into Equation (4) and Equation (5) to obtain the characteristic curve of the bearing capacity of the reinforced concrete under the second stress mode, and determine the second warning threshold.

[0020] Optionally, the third stress mode of the reinforced concrete rectangular section is as follows: When ; mainly consider that the compression zone of the member is damaged by compression; Let the cross-section strength calculation formula for a small eccentric compression member with a rectangular cross-section of reinforced concrete In the formula, the safety factor K is 1, and it is known that , ; From this, we can obtain

[0021] where represents the compressive strength of concrete; Input the basic physical and mechanical parameters into Equation (6) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the third stress mode, and determine the third warning threshold.

[0022] A health monitoring and warning system for a tunnel during the operation period passing through an active fault. The system includes: an axial array displacement meter, an axial array displacement meter, a steel bar stress meter, a concrete strain meter, and a processing module; The axial array displacement meter is used to measure the fault displacement and displacement mode of the fault of the tunnel passing through the active fault; The circumferential array displacement meter is used to measure the convergence deformation of the tunnel structure; The steel bar stress meter is used to monitor stress; the concrete strain meter is used to monitor strain; The monitoring data includes: stress, strain, and the convergence deformation of the tunnel structure; The processing module is used to input the fault displacement and displacement mode as boundary conditions, and combine with the concrete damage plasticity model to perform three-dimensional finite element numerical simulation of the stratum-structure method to obtain the finite element numerical simulation results; The processing module is also used to calculate the bending moment and axial force of the tunnel structure through stress and strain; The processing module is also used to perform engineering verification on the finite element numerical simulation results through the bending moment, axial force, and convergence deformation, and adjust the parameters of the finite element numerical simulation results; The processing module is also used to obtain the basic physical and mechanical parameters of the tunnel, combine with the tunnel structure evaluation method to obtain the characteristic curve of the bearing capacity of reinforced concrete, and determine the warning threshold of the tunnel structure; The processing module is also used to combine the collected monitoring data, the adjusted finite element numerical simulation results, and the warning threshold to obtain the warning result of the tunnel structure passing through the active fault.

[0023] Optionally, the axial array displacement meters are arranged at the left and right arch waists of the tunnel; the axial array displacement meters are arranged between the primary support and the surrounding rock, and both ends of the axial array displacement meters pass through a preset distance of the active fault; Select 2 tunnel sections at the preset positions of the active fault, and symmetrically arrange the circumferential array displacement gauges along the circumferential direction from the left springing of the tunnel section to the right springing of the same tunnel section. Arrange steel bar strain gauges and concrete strain gauges on the inner and outer sides of the secondary lining steel bar mesh of the selected 2 tunnel sections, specifically including: setting steel bar strain gauges and concrete strain gauges at the left and right spring waists, left and right shoulders and crown of the secondary lining of each tunnel section.

[0024] The beneficial effects brought by the technical solution provided by this application are: 1. The circumferential and axial array displacement gauges can accurately measure the displacement magnitude and mode of the active fault around the tunnel, providing a basis for the influence of the dislocation of the active fault zone on the tunnel structure. The finite element numerical simulation of the tunnel crossing the active fault can correct the parameters according to the monitoring data of the tunnel deformation and the stress of the secondary lining on site, making the numerical simulation results more in line with the engineering reality. At the same time, the finite element numerical simulation of the tunnel crossing the active fault overcomes the limitation that the tunnel site monitoring can only carry out typical sections. Derive the theoretical limits of the bending moment and axial force that the tunnel structure can bear under the bending and compression loads, form a structural evaluation method - the characteristic curve of the bearing capacity of reinforced concrete, and accordingly conduct targeted and effective early warning on the health status of the tunnel structure. The judgment method is simple and reasonable. The combination of numerical simulation - monitoring feedback - model correction, theoretical derivation, and engineering verification makes the early warning results of the tunnel structure more reasonable. The above methods complement each other and work together to ensure the safety and quality of the tunnel project.

[0025] 2. Propose a method for health monitoring and early warning during the operation period of the tunnel crossing the active fault, realize accurate measurement of the displacement magnitude and mode of the fault around the tunnel, propose a structural evaluation method for mountain tunnels - the characteristic curve of the bearing capacity of reinforced concrete, and verify the accuracy and feasibility of the numerical simulation results under the fault displacement mode through the monitoring of the stress and strain of the reinforced concrete of the typical section. Description of the Drawings

[0026] The following will further illustrate the present application in conjunction with the drawings. In the drawings: Figure 1 is the flowchart in the embodiment of the present application; Figure 2 is the schematic diagram of the layout of the monitoring array displacement gauges in the embodiment of the present application; Figure 3 is the top view of the layout of the monitoring array displacement gauges in the embodiment of the present application; Figure 4 is the layout diagram of the circumferential array displacement gauges, concrete strain gauges and steel bar strain gauges in the embodiment of the present application; Figure 5 is the structural schematic diagram of the finite element model in the embodiment of the present application; Figure 6 It is the flow chart for calculating the bearing capacity of reinforced concrete under bending load in the embodiments of the present application; Figure 7 It is the diagram of the stress condition of reinforced concrete under bending load in the first stress mode in the embodiments of the present application; Figure 8 It is the diagram of the stress condition of reinforced concrete under bending load in the third stress mode in the embodiments of the present application; Figure 9 It is the characteristic curve diagram of the bearing capacity of reinforced concrete in the first stress mode in the embodiments of the present application; Figure 10 It is the characteristic curve diagram of the bearing capacity of reinforced concrete in the second stress mode in the embodiments of the present application; Figure 11 It is the schematic diagram of the characteristic curve of the bearing capacity of reinforced concrete in the third stress mode in the embodiments of the present application. Detailed implementation manners

[0027] For a clearer understanding of the technical features, objectives, and effects of the present application, the detailed implementation manners of the present application will now be described in detail with reference to the accompanying drawings.

[0028] The embodiments of the present application provide a method for health monitoring and early warning during the operation period of a tunnel crossing an active fault.

[0029] Please refer to Figure 1 , Figure 1 It is the flow chart of a method for health monitoring and early warning during the operation period of a tunnel crossing an active fault in the embodiments of the present application, including: S1: Measuring the fault offset amount and the fault displacement mode of the tunnel crossing the active fault; S2: Taking the fault offset amount and the fault displacement mode as boundary conditions and inputting them, and combining with the concrete damage plasticity model to perform three-dimensional stratum-structure method finite element numerical simulation to obtain the finite element numerical simulation results; In some embodiments, the concrete damage plasticity model (CDP) in the ABAQUS finite element analysis software is a constitutive model based on plasticity mechanics and damage mechanics, which can simulate the nonlinear behavior of concrete under complex loads, including characteristics such as tensile cracking, compressive crushing, stiffness degradation, and irreversible plastic deformation.

[0030] In some embodiments, the fault offset amount measured by the array displacement meter is very small, but the fault displacement mode is clear. When used as boundary conditions, the fault displacement mode applies the monitoring data, while the fault offset amount is increased in a certain proportion and graded, and multiple working conditions of different fault offset amounts of the fault are set and applied to the boundary, which has a certain predictability.

[0031] In some embodiments, the finite element numerical simulation can obtain the stress and deformation conditions of the tunnel in all dimensions, and can extract the bending moments, axial forces, etc. of multiple cross-sections and multiple working conditions, so as to conduct multi-site and multi-state early warnings for the tunnel.

[0032] S3: Collect monitoring data according to the control indexes of the tunnel passing through the active fault; the control indexes include: bending moment, axial force, and the convergence deformation of the tunnel structure; S4: Conduct engineering verification on the finite element numerical simulation results through the collected monitoring data, and adjust the parameters of the finite element numerical simulation results; S5: Obtain the basic physical and mechanical parameters of the tunnel, and combine with the tunnel structure evaluation method to obtain the characteristic curve of the bearing capacity of reinforced concrete, and determine the early warning threshold of the tunnel structure; S6: Combine the collected monitoring data, the adjusted finite element numerical simulation results, and the early warning threshold to obtain the early warning result of the tunnel structure passing through the active fault.

[0033] Step S5 includes: Discriminate the stress modes of the reinforced concrete rectangular cross-section; the stress modes include: the first stress mode, the second stress mode, and the third stress mode; Through the stress mode and the basic physical and mechanical parameters, combined with the strength calculation formula of the reinforced concrete flexural member, the section strength calculation formula of the large eccentric compression member, and the section strength calculation formula of the small eccentric compression member, obtain the characteristic curve of the bearing capacity of reinforced concrete under different stress modes; Determine the early warning threshold of the tunnel structure through the characteristic curve of the bearing capacity of reinforced concrete; The early warning threshold includes: the first early warning threshold, the second early warning threshold, and the third early warning threshold.

[0034] As an embodiment, Figure 6 shows the calculation process of the bearing capacity of reinforced concrete under the combined compression and bending load. From formulas (1) to (6), input the basic physical and mechanical parameters (the ultimate flexural compressive strength of concrete , the width of the rectangular cross-section , etc.), combined with Figure 7 and Figure 8 the stress conditions of reinforced concrete under different combined compression and bending load conditions, the characteristic curve of the bearing capacity of reinforced concrete under specific tunnel examples can be obtained. Figures 10 to 11

[0035] As an embodiment, the present invention provides a method for health monitoring during the operation period of a tunnel passing through an active fault, which measures the circumferential steel bar stress and concrete strain of the secondary lining, the tunnel convergence deformation, the magnitude of the fault offset, and the fault displacement mode.

[0036] The calculation formula for the strength of the reinforced concrete flexural member is as follows:

[0037] Among them, represents the safety factor; represents the bending moment; represents the ultimate flexural compressive strength of concrete; represents the width of the rectangular section; represents the height of the concrete compression zone; represents the standard value of the tensile or compressive strength of the steel bar; represents the cross-sectional area of the compression steel bar; represents the effective height of the section; represents the distance from the centroid of the tensile steel bar or the compression steel bar to the nearest edge of the section respectively; The calculation formula for the cross-sectional strength of a large eccentric compression member is as follows:

[0038] Among them, represents the axial force; represents the cross-sectional area of the tensile steel bar; The calculation formula for the cross-sectional strength of a small eccentric compression member is as follows:

[0039] Among them represents the distance from the centroid of the tensile steel bar or the compression steel bar to the action point of the axial force.

[0040] As an example, the basic physical and mechanical parameters of the tunnel structure are shown in Table 1.

[0041] Table 1

[0042] The first stress mode of the reinforced concrete rectangular section is as follows: When ; Let the safety factor K of the calculation formula for the strength of the reinforced concrete flexural member and the calculation formula for the cross-sectional strength of the large eccentric compression member be 1; From the cross-sectional strength of the large eccentric compression member,

[0043] Substitute Equation (1) into the calculation formula for the strength of the reinforced concrete flexural member, and in the tunnel structure we get

[0044] At the same time, M should satisfy the following conditions:

[0045] Among them represents the unit of the physical quantity bending moment M.

[0046] Input the basic physical and mechanical parameters into Equations (2) and (3) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the first stress mode, and determine the first warning threshold.

[0047] The second stress mode of the reinforced concrete rectangular section is as follows: When it is mainly considered that the tension zone of the component is damaged by tension; It is known that , Among them represents the distance from the neutral axis to the action point of the axial force; represents the section height; Let the safety factor K in the cross-section strength calculation formula of the small eccentric compression member be 1, and we can get

[0048] At the same time, M and N should satisfy the following conditions:

[0049] Input the basic physical and mechanical parameters into Equations (4) and (5) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the second stress mode, and determine the second warning threshold.

[0050] The third stress mode of the reinforced concrete rectangular section is as follows: When it is mainly considered that the compression zone of the component is damaged by compression; Let the safety factor K in the cross-section strength calculation formula of the small eccentric compression member of the reinforced concrete rectangular section be 1. It is known that , ; From this, we can get

[0051] Among them represents the concrete compressive strength; Input the basic physical and mechanical parameters into Equation (6) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the third stress mode, and determine the third warning threshold.

[0052] A health monitoring and warning system for tunnels during the operation period crossing active faults. The system includes: axial array displacement gauges, axial array displacement gauges, steel bar stress gauges, concrete strain gauges, and a processing module; As an example, the array displacement meter is composed of multiple test units, and each test unit is composed of multiple standard segments. The standard segments are connected by flexible links and can measure displacements in three dimensions (X, Y, and Z directions), with a measurement accuracy of 0.1% FS. In some embodiments, the standard segments of the test unit of the array displacement meter can be selected as 0.5 m / section or 1 m / section, and the total length of the instrument can be customized according to the fault width.

[0053] The axial array displacement meter is used to measure the fault displacement and displacement pattern of the fault passing through the tunnel across the active fault. The circumferential array displacement meter is used to measure the convergence deformation of the tunnel structure. The steel bar stress meter is used to monitor stress; the concrete strain meter is used to monitor strain. The monitoring data includes: stress, strain, and the convergence deformation of the tunnel structure. The processing module is used to input the fault displacement and displacement pattern as boundary conditions, and combine with the concrete damage plasticity model to perform three-dimensional finite element numerical simulation of the stratum-structure method to obtain the finite element numerical simulation results. The processing module is also used to calculate the bending moment and axial force of the tunnel structure through stress and strain. The processing module is also used to perform engineering verification on the finite element numerical simulation results through the bending moment, axial force, and convergence deformation, and adjust the parameters of the finite element numerical simulation results. The processing module is also used to obtain the basic physical and mechanical parameters of the tunnel, combine with the tunnel structure evaluation method to obtain the characteristic curve of the bearing capacity of reinforced concrete, and determine the warning threshold of the tunnel structure. The processing module is also used to combine the collected monitoring data, the adjusted finite element numerical simulation results, and the warning threshold to obtain the warning result of the tunnel structure crossing the active fault.

[0054] The axial array displacement meter is arranged at the left and right arch waists of the tunnel; the axial array displacement meter is arranged between the primary support and the surrounding rock, and both ends of the axial array displacement meter pass through the active fault for a preset distance. As an example, the axial array displacement meter (the array displacement meter along the axis) is arranged at the left and right arch waists of the tunnel; the axial array displacement meter is arranged between the primary support and the surrounding rock, and both ends of the axial array displacement meter pass through the active fault for a preset distance, so as to accurately measure the magnitude of the fault displacement around the tunnel and the displacement pattern.

[0055] Select two tunnel sections at the preset positions of the active fault, and symmetrically arrange the circumferential array displacement meters along the circumferential direction from the left arch foot of the tunnel section to the right arch foot of the same tunnel section. As an example, for the circumferential array displacement gauges, two typical tunnel sections crossing the active fault are selected and symmetrically arranged circumferentially from the left springing to the right springing to monitor the convergence deformation of the tunnel structure caused by the fault dislocation.

[0056] In some embodiments, referring to Figure 2 and Figure 3 , in this embodiment, the test unit of the array displacement gauge uses a standard section of 1 meter per section, and the standard sections are connected by flexible joints. Each standard section requires 2 fixing points. The axial array displacement gauge is arranged at the positions of the left and right waist of the tunnel between the primary support and the surrounding rock through the fixing points composed of expansion bolts and pedestals, and both ends of the displacement gauge pass through a certain distance of the active fault to accurately measure the magnitude and mode of the fault dislocation amount around the tunnel. Two typical tunnel sections at the interface between the fault and the general surrounding rock are selected, and the circumferential array displacement gauge is installed section by section using the pedestal, expansion bolt and saddle clip, symmetrically arranged circumferentially from the left springing to the right springing to monitor the convergence deformation of the tunnel structure caused by the fault dislocation. After the axial and circumferential array displacement gauges are installed and run stably for a period of time (recommended 48h), the initial readings can be collected according to the requirements of the monitoring items.

[0057] Reinforcement stress gauges and concrete strain gauges are arranged on the inner and outer sides of the secondary lining reinforcement mesh of the 2 selected tunnel sections, specifically including: at the positions of the left and right waist, left and right shoulders and the crown of the secondary lining of each tunnel section, reinforcement stress gauges and concrete strain gauges are set.

[0058] In some embodiments, referring to Figure 4 , reinforcement stress gauges and concrete strain gauges are arranged on the inner and outer sides of the secondary lining reinforcement mesh, and the positions are the same as the two sections of the circumferential array displacement gauge. Each section is arranged at the positions of the left and right waist, left and right shoulders and the crown of the secondary lining. The main purpose is to monitor the change of the internal force of the secondary lining.

[0059] Figure 5 is the structural schematic diagram of the finite element model in the embodiment of the present application; Figure 9 is the characteristic curve of the bearing capacity of reinforced concrete under the first stress mode in the embodiment of the present application.

[0060] The above are only exemplary embodiments of the present disclosure, and the scope of the present disclosure cannot be limited thereby. That is, any equivalent changes and modifications made according to the teachings of the present disclosure still fall within the scope covered by the present disclosure.

[0061] This application is intended to cover any variations, uses, or adaptations of the present disclosure, which follow the general principles of the present disclosure and include well-known knowledge or conventional technical means in the technical field not recorded in the present disclosure. The description and examples are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A health monitoring and early warning method for a tunnel during its operation period passing through an active fault, characterized in that, The method includes the following steps: S1: Measure the fault displacement and displacement pattern of the tunnel crossing the active fault. S2: Input the fault displacement and displacement pattern as boundary conditions, and combine with the concrete damage plasticity model to conduct 3D finite element numerical simulation of the stratum-structure method to obtain the finite element numerical simulation results. S3: Collect monitoring data according to the control indexes of the tunnel crossing the active fault; the control indexes include: bending moment, axial force, and the convergent deformation of the tunnel structure. S4: Conduct engineering verification on the finite element numerical simulation results through the collected monitoring data, and adjust the parameters of the finite element numerical simulation results. S5: Obtain the basic physical and mechanical parameters of the tunnel, and combine with the tunnel structure evaluation method to obtain the characteristic curve of the bearing capacity of reinforced concrete, and determine the warning threshold of the tunnel structure. S6: Combine the collected monitoring data, the adjusted finite element numerical simulation results, and the warning threshold to obtain the warning result of the tunnel structure crossing the active fault.

2. The health monitoring and early warning method for a tunnel during the operation period passing through an active fault as claimed in claim 1, characterized in that, Step S5 includes: Discriminate the stress mode of the reinforced concrete rectangular section; the stress modes include: the first stress mode, the second stress mode, and the third stress mode. Through the stress mode and the basic physical and mechanical parameters, combine with the strength calculation formula of the reinforced concrete flexural member, the section strength calculation formula of the large eccentric compression member, and the section strength calculation formula of the small eccentric compression member to obtain the characteristic curve of the bearing capacity of reinforced concrete under different stress modes. Determine the warning threshold of the tunnel structure through the characteristic curve of the bearing capacity of reinforced concrete. The warning thresholds include: the first warning threshold, the second warning threshold, and the third warning threshold.

3. The health monitoring and early warning method during the operation period of a tunnel crossing an active fault according to claim 2, characterized in that, The calculation formula for the strength of the reinforced concrete flexural member is as follows: Among them, represents the safety factor; represents the bending moment; represents the ultimate flexural compressive strength of concrete; represents the width of the rectangular section; represents the effective height of the section; represents the height of the concrete compression zone; represents the standard value of the tensile or compressive strength of the steel bar; represents the cross-sectional area of the compression zone steel bar; represents the distance from the centroid of the tensile or compressive steel bar to the nearest edge of the section respectively; The calculation formula for the section strength of the large eccentric compression member is as follows: Among them, represents the axial force; represents the cross-sectional area of the tension reinforcement; The calculation formula for the section strength of the small eccentric compression member is as follows: Among them It represents the distance from the centroid of the tension or compression reinforcement to the action point of the axial force.

4. A method for health monitoring and early warning during the operation period of a tunnel crossing an active fault, as described in claim 3, characterized in that, The first stress mode of the reinforced concrete rectangular section is as follows: When ; Let the safety factor K of the strength calculation formula of the reinforced concrete flexural member and the section strength calculation formula of the large eccentric compression member be 1. From the section strength of the large eccentric compression member, Substitute Equation (1) into the strength calculation formula of reinforced concrete flexural members, and in the tunnel structure to obtain At the same time, M should satisfy the following conditions: Input the basic physical and mechanical parameters into formulas (2) and (3) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the first stress mode, and determine the first warning threshold.

5. The health monitoring and early warning method during the operation period of a tunnel crossing an active fault as claimed in claim 4, wherein The second stress mode of the reinforced concrete rectangular section is as follows: When it is considered that the tension zone of the component is damaged by tension; Known , , where represents the distance from the neutral axis to the acting point of the axial force; represents the section height; Let the safety factor K in the cross-sectional strength calculation formula of small eccentric compression members be 1, then we can get At the same time, M and N should satisfy the following conditions: Input the basic physical and mechanical parameters into formulas (4) and (5) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the second stress mode, and determine the second warning threshold.

6. The health monitoring and early warning method for the operation period of a tunnel crossing an active fault as described in claim 5, characterized in that, The third stress mode of the reinforced concrete rectangular section is as follows: When occurs, the main consideration is that the compression zone of the component is crushed; Let the cross-section strength calculation formula for a small eccentric compression member with a rectangular cross-section of reinforced concrete in which the safety factor K is 1, and it is known that , ; From this, it can be obtained that wherein represents the compressive strength of concrete; Input the basic physical and mechanical parameters into formula (6) to obtain the characteristic curve of the bearing capacity of reinforced concrete under the third stress mode, and determine the third warning threshold.

7. A health monitoring and early warning system for a tunnel during its operation period crossing an active fault, which is used to implement a health monitoring and early warning method for a tunnel during its operation period crossing an active fault as described in any one of claims 1-6, characterized in that, The system includes: axial array displacement meters, circumferential array displacement meters, steel bar stress gauges, concrete strain gauges, and a processing module. The axial array displacement meter is used to measure the fault displacement and displacement pattern of the tunnel crossing the active fault. The circumferential array displacement meter is used to measure the convergent deformation of the tunnel structure. The steel bar stress gauge is used to monitor stress; the concrete strain gauge is used to monitor strain. The monitoring data includes: stress, strain, and the convergence deformation of the tunnel structure; The processing module is used to input the fault displacement amount and displacement mode as boundary conditions, and combine with the concrete damage plasticity model to perform three-dimensional stratum-structure method finite element numerical simulation to obtain the finite element numerical simulation results; The processing module is also used to calculate the bending moment and axial force of the tunnel structure through stress and strain; The processing module is also used to conduct engineering verification on the finite element numerical simulation results through the bending moment, axial force, and convergence deformation, and adjust the parameters of the finite element numerical simulation results; The processing module is also used to obtain the basic physical and mechanical parameters of the tunnel, combine with the tunnel structure evaluation method to obtain the characteristic curve of the bearing capacity of reinforced concrete, and determine the warning threshold of the tunnel structure; The processing module is also used to combine the collected monitoring data, the adjusted finite element numerical simulation results, and the warning threshold to obtain the warning result of the tunnel structure passing through the active fault; 8. The health monitoring and early warning system for a tunnel during the operation period passing through an active fault as claimed in claim 7, wherein, The axial array displacement meters are arranged at the left and right arch waists of the tunnel; the axial array displacement meters are arranged between the primary support and the surrounding rock, and both ends of the axial array displacement meters pass through the active fault for a preset distance; Select 2 tunnel sections at the preset positions of the active fault, and symmetrically arrange the circumferential array displacement meters along the circumferential direction from the left arch foot of the tunnel section to the right arch foot of the same tunnel section; Reinforcement stress gauges and concrete strain gauges are arranged on the inner and outer sides of the secondary lining steel mesh of the selected 2 tunnel sections, specifically including: setting reinforcement stress gauges and concrete strain gauges at the left and right arch waists, left and right arch shoulders, and arch top positions of the secondary lining of each tunnel section.

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