Subway tunnel structure disease loading model test device and reliability dynamic evaluation method

Abstract

The invention discloses a subway tunnel structure disease loading model test device and a reliability dynamic evaluation method. The device comprises a lining model, a subway operation load simulation system, a foundation soil model, a tunnel confining pressure system, a test reaction frame and a data acquisition and analysis system, and structural cracks are prefabricated in the lining model; the subway operation load simulation system comprises a vibration exciter, a signal generator and a power amplifier; the tunnel confining pressure system comprises a plurality of pressure applying mechanisms distributed on the outer side of the lining model; the data acquisition and analysis system comprises a high-speed camera and a strain gauge; the device can simulate crack diseases, surrounding rock pressure and vibration loads of a subway tunnel structure, and can be effectively suitable for a subway tunnel structure disease loading model test. According to the method, the dynamic reliability evaluation of the tunnel structure is realized by simulating the disease evolution process of the subway tunnel under multiple factors such as operation load, geological condition and environmental change and through random simulation of multi-factor coupling.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel reliability assessment, and in particular to a subway tunnel structural defect loading model test device and a reliability dynamic assessment method. Background Art

[0002] Under the influence of various factors such as subway vehicle operating load, ground construction, seasonal changes in groundwater levels, uneven deformation of the strata, etc., the subway tunnel structure will inevitably experience varying degrees of damage; with the increase in operating years, the tunnel lining will experience cracking, surface shedding, concrete carbonization, water seepage, and longitudinal uneven settlement. These diseases will become an important hidden danger threatening the safe operation of the subway. If not handled in time, it will accelerate the degradation of the tunnel structure performance and significantly shorten the safe service life of the subway tunnel. With the aging of subway systems in major cities and the increase in new lines, subway tunnel diseases will become a major challenge restricting the safe operation and management of urban subways.

[0003] The complexity and concealment of tunnel engineering make it difficult to effectively observe and evaluate phenomena such as tunnel settlement and diseases during operation. Due to the complexity of the causes and development trends of tunnel structural diseases, it is difficult to accurately predict them by theoretical calculations and numerical simulations alone. In contrast, the tunnel model test method has become an effective means of studying tunnel engineering problems due to its advantages of low requirements for test sites, strong controllability, and strong observability; especially the three-dimensional tunnel model test method, which can more realistically simulate complex tunnel environments, accurately reflect the distribution of stress and deformation, and has a stronger visualization effect.

[0004] It should be pointed out that tunnel structures will be affected by a variety of uncertain factors in long-term operation, and there may be complex coupling effects between these factors. Therefore, it is often difficult to fully consider these complex effects and accurately predict the overall behavior of tunnel structures by relying solely on theoretical analysis or numerical simulation. In addition, as the tunnel operation time goes by, the safety and stability of the tunnel structure will change dynamically. Therefore, updating the reliability assessment of the tunnel structure based on real-time monitoring data is crucial for risk prediction and management of subway operations.

[0005] In summary, the defects in the existing technology for the assessment and management of structural defects in operating subway tunnels are summarized as follows:

[0006] 1. Inaccurate damage prediction under the coupling of multiple factors: Traditional subway tunnel structure damage analysis usually relies on theoretical calculation or numerical simulation of a single factor, which makes it difficult to comprehensively consider the coupling of multiple factors such as operating loads, geological conditions, and environmental changes, resulting in inaccurate damage prediction and difficulty in comprehensively evaluating the safety of tunnel structures;

[0007] 2. Unable to dynamically evaluate the safety of tunnel structures: Existing evaluation methods are mostly static analysis, which cannot reflect the state changes of tunnel structures in long-term operation in real time. As the operating life of subway tunnels increases, the structural performance gradually deteriorates, and the safety and reliability are also changing dynamically. Traditional methods are difficult to update in time and accurately predict the failure risk of tunnels;

[0008] 3. Insufficient means of disease observation and assessment: The concealment and complexity of tunnel structures make it difficult to observe and evaluate tunnel settlement, crack expansion and other diseases. Existing means are difficult to provide intuitive and accurate data on the evolution of diseases, thus affecting the accuracy and reliability of structural safety assessment;

[0009] 4. Lack of a systematic disease assessment process: Existing technologies lack a systematic process for subway tunnel disease assessment, and it is difficult to provide a set of standardized disease analysis and risk assessment methods, resulting in insufficient stability and reliability of assessment results in practical applications. Summary of the invention

[0010] The purpose of the present invention is to provide a subway tunnel structure disease loading model test device to address the deficiencies of the prior art. The subway tunnel structure disease loading model test device can simulate crack diseases, surrounding rock pressure, and vibration loads of the subway tunnel structure, and can be effectively applied to the subway tunnel structure disease loading model test.

[0011] Another object of the present invention is to provide a method for dynamic evaluation of subway tunnel structure reliability in response to the deficiencies in the prior art. The method for dynamic evaluation of subway tunnel structure reliability simulates the disease evolution process of the subway tunnel under multiple factors such as operating load, geological conditions and environmental changes, and realizes dynamic reliability evaluation of the tunnel structure through random simulation of multi-factor coupling.

[0012] To achieve the above object, the present invention is implemented through the following technical solutions.

[0013] A subway tunnel structural disease loading model test device, comprising a lining model, a subway operation load simulation system, a foundation soil model, a tunnel confining pressure system, a test reaction frame, and a data acquisition and analysis system;

[0014] The lining model is used to simulate the tunnel lining structure in the subway tunnel, and the lining model is prefabricated with structural cracks for crack diseases in the operating subway tunnel; the lining model is installed on the upper end of the foundation soil model, and the subway operation load simulation system is installed on the lining model;

[0015] The subway operation load simulation system includes an exciter, a signal generator, and a power amplifier. The output end of the signal generator is electrically connected to the input end of the power amplifier, and the output end of the power amplifier is electrically connected to the exciter. When working, the signal generator outputs a subway load simulation waveform signal, and the subway load simulation waveform signal is amplified by the power amplifier and then transmitted to the exciter, and the exciter simulates the subway operation load.

[0016] The test reaction frame is a steel frame structure with the bottom fixed to the ground by bolts, and the tunnel confining pressure system is installed on the test reaction frame;

[0017] The tunnel confining pressure system includes a plurality of pressure applying mechanisms distributed on the outside of the lining model, each of which includes a jack installed on the test reaction frame, a loading pad in contact with the outer surface of the lining model, a pressure sensor connecting the driving end of the jack and the loading pad, and a pressure display connected to the pressure sensor; the plurality of pressure applying mechanisms include a vertical pressure applying mechanism for applying pressure to the lining model vertically downward, a left lateral pressure applying mechanism for applying pressure to the lining model horizontally to the left, and a right lateral pressure applying mechanism for applying pressure to the lining model horizontally to the right;

[0018] The data acquisition and analysis system includes a high-speed camera aimed at the structural crack tip area of ​​the lining model and a number of strain gauges pasted and fixed to the structural crack tip area of ​​the lining model. The strain gauges are connected to the data acquisition system through wires. When working, the images obtained by the high-speed camera are processed through digital image correlation DIC software to obtain the displacement field near the crack tip of the structural crack.

[0019] The foundation soil model comprises a model box and soil filled in the model box, and the lining model is supported by the soil in the foundation soil model.

[0020] Wherein, the loading pad is an arc-shaped recording pad, and the arc-shaped loading pad is in contact with and fits with the outer surface of the lining model.

[0021] Wherein, the inner surface of the loading pad is provided with sponge.

[0022] A method for dynamic evaluation of subway tunnel structure reliability includes the following steps, specifically:

[0023] Step S1, preparing the above subway tunnel structural disease loading model test device;

[0024] Step S2, using the subway tunnel structure disease loading model test device to conduct a test to simulate the development of tunnel structure cracks under the load of an operating subway, and recording and storing data collected by the strain gauge and images taken by the high-speed camera during the test;

[0025] Step S3, in the strain field at the crack tip, the strain is mainly concentrated in the direction perpendicular to the crack surface, and the strain in the area around the crack tip is measured. The strain perpendicular to the crack surface is the normal strain, and the strain parallel to the crack surface is the tangential strain; if the normal strain is significantly greater than the tangential strain, it indicates a type I crack; if the tangential strain is significantly greater than the normal strain, it indicates a type II crack;

[0026] Based on the strain field data recorded by the strain gauge, the stress intensity factor is calculated, specifically:

[0027]

[0028] Among them, σ represents the normal stress at the crack tip, a represents the crack length, π represents the pi constant, τ represents the shear stress at the crack tip, and Y is the geometric correction factor;

[0029] Step S4: based on the displacement field data recorded by the high-speed camera, extract the displacement distribution of the crack tip in the normal direction perpendicular to the crack surface, and calculate the stress intensity factor K at the crack tip according to the displacement distribution. I ; Extract the displacement distribution of the crack tip in the tangential direction parallel to the crack surface and calculate the stress intensity factor K at the crack tip II ;

[0030] The stress intensity factor is calculated as follows:

[0031]

[0032] Where E is the elastic modulus of the tunnel structure, ν is the Poisson's ratio, r is the distance from the crack tip, and u is y represents the normal displacement, u x represents the tangential displacement, and π represents the circumferential constant;

[0033] Step S5, according to the formula:

[0034]

[0035] In formula 1, m and C represent material constants, R represents stress ratio, and K C represents the fracture toughness of the material, N represents the number of times the subway train passes through the tunnel section; K represents the stress intensity factor, which is K according to the crack type. I Still K II ;

[0036] When the subway train load cycles N times, the lining crack increases from the initial depth a to 0 Expand to depth a N , integrating the above formula 1, we can get:

[0037]

[0038] The maximum limit of crack extension is the lining structure size, set as a max , that is, the lining structure cracks extend to a max When the structure fails completely, the probability of lining structure failure is P f ;

[0039] Step S6: Generate a random sample of each input variable using a random number generator, where the sample follows a defined statistical distribution;

[0040] Step S7: Use the generated random samples to calculate the crack extension depth a corresponding to each sample using the integral formula: N ;

[0041] Step S8: Count the crack extension depth exceeding the set threshold a max The number of times;

[0042] Step S9: Calculate the failure probability, the failure probability P f It is calculated as the ratio of the number of failures to the total number of simulations and used as a measure of structural stability.

[0043] The beneficial effects of the present invention are:

[0044] 1. The subway tunnel structure disease loading model test device of the present invention can accurately control the lateral and vertical confining pressures of the tunnel structure in the stratum, and can accurately apply the surrounding rock pressure through the pressure sensor and the pressure display, and is easy to operate and has a high degree of visualization;

[0045] 2. The subway tunnel structural disease loading model test device of the present invention is suitable for observing the disease development of existing structural crack diseases under the combined action of surrounding rock pressure and subway operation load. The observation effect of the test process is better and the test simulation is more precise;

[0046] 3. The subway tunnel structural disease loading model test device of the present invention simulates the vibration load of subway operation by combining an exciter, a signal generator and a power amplifier. It can simulate vibration loads of different types and different passenger flows, and the adjustment is visual and the operation is convenient;

[0047] 4. The dynamic evaluation method of subway tunnel structure reliability of the present invention is innovatively used to estimate the failure probability of tunnel structure under operating load. This method combines the physical process of crack extension with statistical methods, greatly enhancing the reliability and applicability of the model;

[0048] 5. The dynamic evaluation method of subway tunnel structure reliability of the present invention can be combined with refined data acquisition technology (i.e. DIC, strain gauge measurement technology) to obtain structural crack extension data in real time, further improving the accuracy and dynamics of failure probability analysis;

[0049] 6. The dynamic evaluation method of subway tunnel structure reliability of the present invention can be used to evaluate the structural stability of complex structures such as subway tunnels during long-term operation, providing a basis for engineering maintenance and decision-making; compared with traditional methods, this statistically based failure probability estimation method is closer to practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The present invention is further described below with the aid of the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention.

[0051] Figure 1 It is a structural schematic diagram of the subway tunnel structural disease loading model test device of the present invention.

[0052] exist Figure 1 Included are:

[0053] 1- lining model; 11- structural cracks; 2- subway operation load simulation system; 3- foundation soil model; 4- tunnel confining pressure system; 41- pressure applying mechanism; 411- jack; 412- loading pad; 413- sponge; 5- test reaction frame. DETAILED DESCRIPTION

[0054] The present invention is described below in conjunction with specific implementation methods.

[0055] Embodiment 1, as Figure 1 As shown, a subway tunnel structural disease loading model test device includes a lining model 1, a subway operation load simulation system 2, a foundation soil model 3, a tunnel confining pressure system 4, a test reaction frame 5, and a data acquisition and analysis system.

[0056] Among them, Figure 1 As shown, the lining model 1 is used to simulate the tunnel lining structure in the subway tunnel, and the lining model 1 is prefabricated with structural cracks 11 for crack diseases in the operating subway tunnel; the lining model 1 is installed on the upper end of the foundation soil model 3, and the subway operation load simulation system 2 is installed on the lining model 1.

[0057] Furthermore, the subway operation load simulation system 2 includes an exciter, a signal generator, and a power amplifier. The output end of the signal generator is electrically connected to the input end of the power amplifier, and the output end of the power amplifier is electrically connected to the exciter. When working, the signal generator outputs a subway load simulation waveform signal, and the subway load simulation waveform signal is amplified by the power amplifier and then transmitted to the exciter, and the exciter simulates the subway operation load.

[0058] Furthermore, the test reaction frame 5 is a steel frame structure whose bottom is fixed to the ground by bolts, and the tunnel confining pressure system 4 is installed on the test reaction frame 5 .

[0059] In addition, the tunnel confining pressure system 4 is used to simulate the surrounding rock pressure of the lining model 1, and the tunnel confining pressure system 4 includes a plurality of pressure applying mechanisms 41 distributed on the outside of the lining model 1, each of the pressure applying mechanisms 41 includes a jack 411 installed on the test reaction frame 5, a loading pad 412 in contact with the outer surface of the lining model 1, a pressure sensor connecting the driving end of the jack 411 and the loading pad 412, and a pressure display connected to the pressure sensor; the plurality of pressure applying mechanisms 41 include a vertical pressure applying mechanism 41 that applies pressure to the lining model 1 vertically downward, a left-side lateral pressure applying mechanism 41 that applies pressure to the lining model 1 horizontally to the left, and a right-side lateral pressure applying mechanism 41 that applies pressure to the lining model 1 horizontally to the right.

[0060] In addition, the data acquisition and analysis system includes a high-speed camera aimed at the tip area of ​​the structural crack 11 of the lining model 1, and a plurality of strain gauges pasted and fixed to the tip area of ​​the structural crack 11 of the lining model 1, and the strain gauges are connected to the data acquisition system through wires; when working, the image obtained by the high-speed camera is processed through digital image correlation DIC software to obtain the displacement field near the crack tip of the structural crack 11.

[0061] The subway tunnel structural damage loading model test device of the first embodiment has the following advantages, specifically:

[0062] 1. The subway tunnel structure disease loading model test device can accurately control the lateral and vertical confining pressures on the tunnel structure in the stratum. It can accurately apply the surrounding rock pressure through the pressure sensor and pressure display. It is easy to operate and has a high degree of visualization.

[0063] 2. The subway tunnel structural disease loading model test device is suitable for observing the disease development of existing structural cracks 11 under the combined action of surrounding rock pressure and subway operation load. The observation effect of the test process is better and the test simulation is more precise;

[0064] 3. The subway tunnel structural disease loading model test device simulates the vibration load of subway operation by combining an exciter, a signal generator and a power amplifier. It can simulate vibration loads of different types and different passenger flows, and the adjustment is visual and the operation is convenient.

[0065] Therefore, the subway tunnel structure disease loading model test device of the first embodiment can simulate the crack disease, surrounding rock pressure, and vibration load of the subway tunnel structure, and can be effectively applied to the subway tunnel structure disease loading model test.

[0066] Embodiment 2: The difference between Embodiment 2 and Embodiment 1 is that the foundation soil model 3 includes a model box and soil filled in the model box, and the lining model 1 is supported by the soil in the foundation soil model 3.

[0067] Embodiment three, as Figure 1 As shown, the difference between the third embodiment and the first embodiment is that the loading pad 412 is an arc-shaped loading pad 412 , and the arc-shaped loading pad 412 is in contact with and fits with the outer surface of the lining model 1 .

[0068] Specifically, a sponge 413 is installed on the inner surface of the loading pad 412 .

[0069] It should be explained that the arc-shaped loading pad 412 can be in contact with and fit the lining model 1 , that is, the arc-shaped loading pad 412 can make each pressure applying mechanism 41 apply pressure more evenly.

[0070] Embodiment 5, a method for dynamically evaluating the reliability of a subway tunnel structure, comprising the following steps, specifically:

[0071] Step S1, preparing a subway tunnel structural disease loading model test device as described in any one of claims 1 to 4;

[0072] Step S2, using the subway tunnel structure disease loading model test device to conduct a test to simulate the development of tunnel structure cracks 11 under the load of an operating subway, and recording and storing data collected by the strain gauge and images taken by the high-speed camera during the test;

[0073] Step S3, in the strain field at the crack tip, the strain is mainly concentrated in the direction perpendicular to the crack surface, and the strain in the area around the crack tip is measured. The strain perpendicular to the crack surface is the normal strain, and the strain parallel to the crack surface is the tangential strain; if the normal strain is significantly greater than the tangential strain, it indicates a type I crack; if the tangential strain is significantly greater than the normal strain, it indicates a type II crack;

[0074] Based on the strain field data recorded by the strain gauge, the stress intensity factor is calculated, specifically:

[0075]

[0076] Among them, σ represents the normal stress at the crack tip, a represents the crack length, π represents the pi constant, τ represents the shear stress at the crack tip, and Y is the geometric correction factor;

[0077] Step S4: based on the displacement field data recorded by the high-speed camera, extract the displacement distribution of the crack tip in the normal direction perpendicular to the crack surface, and calculate the stress intensity factor K at the crack tip according to the displacement distribution. I ; Extract the displacement distribution of the crack tip in the tangential direction parallel to the crack surface and calculate the stress intensity factor K at the crack tip II ;

[0078] The stress intensity factor is calculated as follows:

[0079]

[0080] Where E is the elastic modulus of the tunnel structure, ν is the Poisson's ratio, r is the distance from the crack tip, and u is y represents the normal displacement, u x represents the tangential displacement, and π represents the circumferential constant;

[0081] Step S5, according to the formula:

[0082]

[0083] In formula 1, m and C represent material constants, R represents stress ratio, and K C represents the fracture toughness of the material, N represents the number of times the subway train passes through the tunnel section; K represents the stress intensity factor, which is K according to the crack type. I Still K II ;

[0084] When the subway train load cycles N times, the lining crack increases from the initial depth a to 0 Expand to depth a N , integrating the above formula 1, we can get:

[0085]

[0086] The maximum limit of crack extension is the lining structure size, set as a max , that is, it is considered that the lining structure crack 11 extends to a max When the structure fails completely, the probability of lining structure failure is P f ;

[0087] Step S6: Generate a random sample of each input variable using a random number generator, where the sample follows a defined statistical distribution;

[0088] Step S7: Use the generated random samples to calculate the crack extension depth a corresponding to each sample using the integral formula: N ;

[0089] Step S8: Count the crack extension depth exceeding the set threshold a max The number of times;

[0090] Step S9: Calculate the failure probability, the failure probability P f It is calculated as the ratio of the number of failures to the total number of simulations and used as a measure of structural stability.

[0091] The subway tunnel structure reliability dynamic assessment method of the fifth embodiment has the following advantages, specifically:

[0092] 1. This subway tunnel structure reliability dynamic assessment method is innovatively used to estimate the failure probability of tunnel structures under operational loads. This method combines the physical process of crack propagation with statistical methods, greatly enhancing the reliability and applicability of the model;

[0093] 2. The dynamic evaluation method of subway tunnel structure reliability can be combined with refined data acquisition technology to obtain real-time structural crack expansion data, further improving the accuracy and dynamics of failure probability analysis;

[0094] 3. The dynamic evaluation method of subway tunnel structural reliability can be used to evaluate the structural stability of complex structures such as subway tunnels during long-term operation, providing a basis for engineering maintenance and decision-making; compared with traditional methods, this statistically based failure probability estimation method is closer to practical application;

[0095] 4. Through multi-factor coupling analysis, the behavior of the tunnel structure under actual operating conditions can be more comprehensively reflected;

[0096] 5. When conducting dynamic reliability assessment, through iterative simulation and data update, the reliability assessment of the tunnel structure can be dynamically updated over time to provide more accurate risk prediction;

[0097] 6. Compared with traditional deterministic analysis, the dynamic reliability evaluation method of the present invention can perform statistical analysis on the failure probability based on a large number of random samples, thereby providing quantitative reliability indicators for the safe operation of subway tunnels.

[0098] Therefore, the subway tunnel structure reliability dynamic assessment method of the fifth embodiment of the fifth embodiment can effectively overcome the limitations of traditional tunnel structure assessment methods in dealing with the complexity and dynamics of multiple factors. The disease prediction is accurate and the safety of the tunnel structure can be comprehensively assessed. This method can not only improve the early warning capability of tunnel diseases, but also provide important technical support for extending the safe operation period of subway tunnels.

[0099] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The content of this specification should not be understood as limiting the present invention.

Claims

1. A subway tunnel structural disease loading model test device, characterized by: It includes a lining model (1), a subway operation load simulation system (2), a foundation soil model (3), a tunnel confining pressure system (4), a test reaction frame (5), and a data acquisition and analysis system; The lining model (1) is used to simulate the tunnel lining structure in a subway tunnel, and the lining model (1) is prefabricated with structural cracks (11) for crack diseases in an operating subway tunnel; the lining model (1) is installed on the upper end of the foundation soil model (3), and the subway operation load simulation system (2) is installed on the lining model (1); The subway operation load simulation system (2) comprises an exciter, a signal generator, and a power amplifier. The output end of the signal generator is electrically connected to the input end of the power amplifier, and the output end of the power amplifier is electrically connected to the exciter. When working, the signal generator outputs a subway load simulation waveform signal, and the subway load simulation waveform signal is amplified by the power amplifier and then transmitted to the exciter, and the exciter simulates the subway operation load. The test reaction frame (5) is a steel frame structure whose bottom is fixed to the ground by bolts, and the tunnel confining pressure system (4) is installed on the test reaction frame (5); The tunnel confining pressure system (4) comprises a plurality of pressure applying mechanisms (41) distributed outside the lining model (1), each of the pressure applying mechanisms (41) respectively comprising a jack (411) mounted on a test reaction frame (5), a loading pad (412) in contact with the outer surface of the lining model (1), a pressure sensor connecting the driving end of the jack (411) and the loading pad (412), and a pressure display connected to the pressure sensor; the plurality of pressure applying mechanisms (41) comprise a vertical pressure applying mechanism (41) for applying pressure to the lining model (1) vertically downward, a left lateral pressure applying mechanism (41) for applying pressure to the lining model (1) horizontally to the left, and a right lateral pressure applying mechanism (41) for applying pressure to the lining model (1) horizontally to the right; The data acquisition and analysis system comprises a high-speed camera aimed at the tip area of ​​a structural crack (11) of a lining model (1), and a plurality of strain gauges pasted and fixed to the tip area of ​​the structural crack (11) of the lining model (1), wherein the strain gauges are connected to the data acquisition system via wires; when working, the image acquired by the high-speed camera is processed by digital image correlation (DIC) software to obtain a displacement field near the crack tip of the structural crack (11).

2. A subway tunnel structural damage loading model test device according to claim 1, characterized in that: The foundation soil model (3) comprises a model box and soil filled in the model box, and the lining model (1) is supported by the soil in the foundation soil model (3).

3. The subway tunnel structural damage loading model test device according to claim 1, characterized in that: The loading pad (412) is an arc-shaped loading pad (412), and the arc-shaped loading pad (412) is in contact with and fits the outer surface of the lining model (1).

4. A subway tunnel structural damage loading model test device according to claim 3, characterized in that: The inner surface of the loading pad (412) is provided with a sponge (413).

5. A method for dynamic evaluation of subway tunnel structure reliability, characterized in that: The following steps are included, specifically: Step S1, preparing a subway tunnel structural disease loading model test device as described in any one of claims 1 to 4; Step S2, using the subway tunnel structure disease loading model test device to conduct a test to simulate the development of tunnel structure cracks (11) under the load of an operating subway, and recording and storing data collected by the strain gauge and images taken by the high-speed camera during the test; Step S3, in the strain field at the crack tip, the strain is mainly concentrated in the direction perpendicular to the crack surface, and the strain in the area around the crack tip is measured. The strain perpendicular to the crack surface is the normal strain, and the strain parallel to the crack surface is the tangential strain; if the normal strain is significantly greater than the tangential strain, it indicates a type I crack; if the tangential strain is significantly greater than the normal strain, it indicates a type II crack; Based on the strain field data recorded by the strain gauge, the stress intensity factor is calculated, specifically: Among them, σ represents the normal stress at the crack tip, a represents the crack length, π represents the pi constant, τ represents the shear stress at the crack tip, and Y is the geometric correction factor; Step S4: based on the displacement field data recorded by the high-speed camera, extract the displacement distribution of the crack tip in the normal direction perpendicular to the crack surface, and calculate the stress intensity factor K at the crack tip according to the displacement distribution. I ; Extract the displacement distribution of the crack tip in the tangential direction parallel to the crack surface and calculate the stress intensity factor K at the crack tip II ; The stress intensity factor is calculated as follows: Where E is the elastic modulus of the tunnel structure, ν is the Poisson's ratio, r is the distance from the crack tip, and u is y represents the normal displacement, u x represents the tangential displacement, and π represents the circumferential constant; Step S5, according to the formula: In formula 1, m and C represent material constants, R represents stress ratio, and K C represents the fracture toughness of the material, N represents the number of times the subway train passes through the tunnel section; K represents the stress intensity factor, which is K according to the crack type. I Still K II ; When the subway train load cycles N times, the lining crack expands from the initial depth a0 to the depth a N , integrating the above formula 1, we can get: The maximum limit of crack extension is the lining structure size, set as a max , that is, it is considered that the lining structure crack (11) extends to a max When the structure fails completely, the probability of lining structure failure is P f ; Step S6: Generate a random sample of each input variable using a random number generator, where the sample follows a defined statistical distribution; Step S7: Use the generated random samples to calculate the crack extension depth a corresponding to each sample using the integral formula: N ; Step S8: Count the crack extension depth exceeding the set threshold a max The number of times; Step S9: Calculate the failure probability, the failure probability P f It is calculated as the ratio of the number of failures to the total number of simulations and used as a measure of structural stability.

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