A method, system, device and application for detecting defects in tunnel lining structure

Abstract

The present invention belongs to the technical field of tunnel lining or concrete detection, and discloses a method, system, device, and application for detecting defects in tunnel lining structures. The method arranges several detection areas at equal intervals in sequence on the tunnel lining structure to be tested, and bonds an elastic sheet to each detection area; by using a laser Doppler vibrometer, the laser direction is changed, the laser Doppler vibrometer is moved, and the laser is sequentially projected onto the elastic sheet to detect the tunnel lining structure and collect vibration time domain signals; the spectrum characteristics of the tunnel lining structure are obtained by spectrum analysis of the vibration time domain signal; a spectrum vibration damage index is established based on damage mechanics and vibration mechanics, and finally rapid quantitative detection of defects in the tunnel lining structure is achieved. The use of the sheet of the present invention can make the laser focus better and achieve a better focusing effect. It has high practicality and is applicable to many situations, and is suitable for the fitting of complex concrete structures and tunnel lining structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel lining or concrete detection, and in particular relates to a method, system, device and application for detecting defects in a tunnel lining structure. Background Art

[0002] In today's society where tunnel engineering construction is developing rapidly, a series of tunnel lining defect problems have also emerged. Tunnel linings can be damaged due to various reasons, so different methods should be adopted for the detection of damage according to different types of damage. For surface damage caused by tunnel linings, traditional detection techniques use visual inspection and hammer sound testing methods, which have the disadvantages of low detection efficiency, high subjectivity, poor accuracy, etc. For internal damage caused by tunnel linings, existing technical detection methods include contact measurement and non-contact measurement. The acoustic wave detection method analyzes internal defects by observing acoustic parameters such as the propagation speed and frequency of sound waves inside the lining. Geological radar detection methods, core drilling detection methods, and drilling sound wave methods all act directly on the surface of the object being measured, which may destroy the integrity of the lining structure and have certain limitations, resulting in distortion of the measurement effect or errors, making the experimental results inaccurate.

[0003] With the advancement of science and technology, non-destructive testing technology has developed rapidly, but the existing technology has not disclosed how to use lightweight elastic thin film technology to significantly enhance the focusing effect of the laser Doppler vibrometer during measurement, resulting in a long focusing time and detection time for the existing technology, and is easily affected by the surface roughness of the object being measured, resulting in low accuracy of the measurement results and low detection efficiency. Summary of the invention

[0004] In order to overcome the problems existing in the related art, the embodiments disclosed in the present invention provide a method, system, device and application for detecting defects in a tunnel lining structure.

[0005] The technical solution is as follows: A method for detecting defects in a tunnel lining structure comprises:

[0006] S1, arranging several detection areas at equal intervals on the tunnel lining structure to be tested, and gluing elastic sheets to each detection area;

[0007] S2, by moving the laser Doppler vibrometer to change the direction of the laser, the laser is sequentially projected onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are obtained by spectrum analysis of the vibration time domain signal;

[0008] S3, based on damage mechanics and vibration dynamics, establishes a spectrum vibration damage index to achieve rapid quantitative detection of tunnel lining structure defects.

[0009] In step S1, the tunnel lining structure to be tested is selected, including sequentially pasting elastic sheets on the detection area positions according to the detection order of the arch bottom, arch waist, arch crown, arch waist and arch crown of the tunnel lining according to the length characteristics of the tunnel lining structure.

[0010] In step S2, the processing of the vibration time domain signal includes: obtaining a vibration time history curve by connecting a laser Doppler vibrometer and a data acquisition instrument to a control computer; then performing a fast Fourier transform on the vibration time history curve to obtain a corresponding vibration spectrum curve;

[0011] The external excitation force g(t) is an external excitation force with a period T tending to infinity, and the interval between adjacent frequencies is is an infinitesimal quantity, and the frequency is close to continuous distribution in the interval (-∞,∞); when Δω→0, the discrete variable ω n Transformed into a continuously changing frequency variable ω, the expression of the spectrum function is:

[0012]

[0013] In the formula, G(ω) is the continuous spectrum function of the external excitation force g(t), g(t) is the external excitation force, t is the time variable, i is the imaginary unit in the complex function, ω is the angular frequency variable, e iωt It is an exponential function with the natural constant e as its base.

[0014] In step S3, the spectrum vibration damage index is established based on damage mechanics and vibration mechanics, including: obtaining the natural vibration frequency of the lining structure under inspection through the spectrum characteristics of the vibration curve, comparing the frequency characteristics of the structure in the healthy and damaged states, and using the damage index to evaluate the lining damage degree in combination with vibration mechanics and damage mechanics. The material damage degree D ω The relationship between and its vibration frequency ω is:

[0015]

[0016] Where D ω is the degree of material damage, λ is the wavelength of vibration when the structure is in a healthy state, is the wavelength of vibration when the structure is damaged, ω1 is the natural vibration frequency when the material is healthy, is the natural vibration frequency of the structure in a damaged state, and the material damage degree D ω The value of is between 0 and 1. ω = 0, indicating that the lining structure is in the optimal state. ω =1, indicating that the tunnel lining structure is in the most unfavorable damage state; ρ is the density of the sound structure, is the density of the damaged structure.

[0017] Another object of the present invention is to provide a tunnel lining structure defect detection system, which is implemented by the tunnel lining structure defect detection method, and the system comprises:

[0018] A vibration time domain signal detection module is used to arrange several detection areas at equal intervals on the tunnel lining structure to be tested, and to bond elastic sheets to each detection area;

[0019] The module for acquiring the spectrum characteristics of the tunnel lining structure is used to change the direction of the laser by moving the laser Doppler vibrometer, and sequentially project the laser onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are acquired by analyzing the spectrum of the vibration time domain signal;

[0020] The tunnel lining structure defect detection module is used to establish spectrum vibration damage indicators based on damage mechanics and vibration mechanics, and realize rapid quantitative detection of tunnel lining structure defects.

[0021] Another object of the present invention is to provide a device for detecting defects in a tunnel lining structure, which is implemented by the above-mentioned method for detecting defects in a tunnel lining structure, and comprises:

[0022] The laser Doppler nondestructive vibrometer is mounted on a tripod and connected to the data acquisition instrument and the power adapter through a digital audio cable;

[0023] The laser Doppler nondestructive vibrometer projects laser light onto the elastic sheet to detect the vibration time domain signal of the tunnel lining structure;

[0024] The elastic sheet is bonded to the tunnel lining structure and arranged in sequence on a plurality of detection areas at equal intervals.

[0025] Furthermore, the power adapter is also connected to an integrated lithium battery power source.

[0026] Furthermore, the structure of the elastic sheet is designed as an L-shaped structure, which is divided into an adhesive end and a laser measuring end; the adhesive end is bonded to the detection area, and the laser measuring end is used to receive the laser emitted by the laser Doppler nondestructive vibrometer to detect the vibration time domain signal of the tunnel lining structure.

[0027] Furthermore, the sticking end is bonded to the detection area by one of silica gel, epoxy resin material and pressure-sensitive adhesive.

[0028] Another object of the present invention is to provide an application of the tunnel lining structure defect detection method for measuring micro-vibrations in a limited space of a tunnel project.

[0029] Combined with all the above technical solutions, the beneficial effects of the present invention are as follows: the present invention can achieve good micro-vibration conduction with the help of a light elastic sheet during the detection process, and the sheet is designed into an L-shaped structure for easy pasting and easy focusing and reflection of the laser beam, thereby clearly reflecting the vibration characteristics of the bonded concrete structure and the tunnel lining structure. The laser Doppler non-destructive vibrometer is connected to the Vib20 data acquisition instrument and the power adapter through a digital audio cable, and the laser Doppler non-destructive vibrometer is assembled on a specific platform for point detection. During the detection, several areas are arranged at equal intervals on the tunnel lining (concrete) in sequence, and the elastic sheet is bonded to each area. Through the laser Doppler vibrometer, the laser direction is changed, the laser Doppler vibrometer is moved, and the laser is hit on the sheet in sequence to detect the tunnel lining (concrete) vibration time domain signal, and the spectrum characteristics of the tunnel lining structure are obtained by spectrum analysis of the time domain signal, and the spectrum vibration damage index is established based on damage mechanics and vibration mechanics, and finally the rapid quantitative detection of tunnel lining (concrete) structural defects is realized.

[0030] Compared with the traditional measurement of vibration frequency of concrete structures and tunnel lining structures, the use of thin sheets can make the laser focus faster and achieve better focusing effect. When using thin sheets, the original direction of the laser is not changed, the curve of the vibration result is not affected, and the size of the result is not changed. The thin sheet material fits the concrete structure and the tunnel lining structure without damaging the concrete structure and the tunnel lining structure. The present invention has high practicality and is applicable to many situations, and is suitable for the fitting of complex concrete structures and tunnel lining structures. Rapid detection work can be carried out, and the operability is strong. The thin sheet is easy to carry and the material is light. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0032] Figure 1 1 is a diagram of a method for detecting defects in a tunnel lining structure based on laser Doppler vibration measurement technology provided by an embodiment of the present invention;

[0033] Figure 2 is a diagram of a detection system for tunnel lining structure defects based on laser Doppler vibrometer technology provided by an embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of a detection device for tunnel lining structure defects based on laser Doppler vibrometer technology provided by an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of an elastic sheet provided by an embodiment of the present invention;

[0036] Figure 5is a vibration time history curve diagram provided by an embodiment of the present invention;

[0037] Figure 6 is a vibration spectrum curve diagram provided by an embodiment of the present invention;

[0038] Figure 7 is a fundamental frequency damage degree curve diagram provided by an embodiment of the present invention;

[0039] In the figure: 1. Laser Doppler nondestructive vibrometer; 2. Tripod; 3. Data acquisition instrument; 4. Power adapter; 5. Detection area; 6. Elastic sheet; 7. Adhesive end; 8. Laser measurement end. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0041] The innovative point of the method for detecting defects in tunnel lining structures based on laser Doppler vibrometer technology provided by the embodiment of the present invention is that compared with the traditional measurement of vibration frequencies of concrete structures and tunnel lining structures, the focusing efficiency of the laser beam can be greatly improved and the focusing effect can be significantly enhanced by using elastic sheets, and the L-shaped structure design can make the sheet easy to install and remove.

[0042] Embodiment 1, as Figure 1 As shown, the method for detecting defects in a tunnel lining structure provided by an embodiment of the present invention comprises the following steps:

[0043] S1, arranging several detection areas at equal intervals on the tunnel lining structure to be tested, and gluing elastic sheets to each detection area;

[0044] S2, by moving the laser Doppler vibrometer to change the direction of the laser, the laser is sequentially projected onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are obtained by spectrum analysis of the vibration time domain signal;

[0045] S3, based on damage mechanics and vibration dynamics, establishes a spectrum vibration damage index to achieve rapid quantitative detection of tunnel lining structure defects.

[0046] Exemplarily, a tunnel lining structure to be tested is selected, and based on the length characteristics of the tunnel lining structure, in the detection order of the arch bottom, arch waist, arch top, arch waist and arch top of the tunnel lining, the L-shaped elastic sheet is sequentially pasted on the detection area, the position of the laser Doppler nondestructive vibrometer is adjusted to achieve focusing of the laser beam on the L-shaped elastic sheet, and at least 3 point measurements are performed, with each point measurement time controlled at about 20 seconds. Rapid movement measurement is performed in the above-mentioned detection order to detect the vibration of the tunnel lining structure.

[0047] Exemplarily, the tunnel lining structure may be concrete.

[0048] In step S2, the method for processing the vibration time domain signal includes:

[0049] The laser Doppler vibrometer and data acquisition instrument are connected to the control computer to obtain the vibration time history curve, and then the vibration time history curve is subjected to fast Fourier transform to obtain the corresponding vibration spectrum curve; the transformation includes: the external excitation force g(t) is an external excitation force with a period T tending to infinity, and the interval between adjacent frequencies is is an infinitesimal quantity, and the frequency is close to continuous distribution in the interval (-∞,∞); when Δω→0, the discrete variable ω n Transformed into a continuously changing frequency variable ω, the expression of the spectrum function is:

[0050]

[0051] In the formula, G(ω) is the continuous spectrum function of the external excitation force g(t), g(t) is the external excitation force, t is the time variable, i is the imaginary unit in the complex function, ω is the angular frequency variable, e iωt It is an exponential function with the natural constant e as its base.

[0052] In step S3, the spectrum vibration damage index is established based on damage mechanics and vibration mechanics, including: obtaining the natural vibration frequency of the lining structure under inspection through the spectrum characteristics of the vibration curve, comparing the frequency characteristics of the structure in the healthy and damaged states, and using the damage index to evaluate the lining damage degree in combination with vibration mechanics and damage mechanics. The material damage degree D ω The relationship between and its vibration frequency ω is:

[0053]

[0054] Where D ω is the degree of material damage, λ is the wavelength of vibration when the structure is in a healthy state, is the wavelength of vibration when the structure is damaged, ω1 is the natural vibration frequency when the material is healthy, is the natural vibration frequency of the structure in a damaged state, and the material damage degree Dω The value of is between 0 and 1. ω = 0, indicating that the lining structure is in the optimal state. ω =1, indicating that the tunnel lining structure is in the most unfavorable damage state; ρ is the density of the sound structure, is the density of the damaged structure.

[0055] It can be seen from the above embodiments that the present invention has demonstrated its application value in the field of tunnel lining defect detection, bringing a more efficient, more convenient and faster solution, which can meet the market demand for laser Doppler nondestructive testing and create more business opportunities in various industries.

[0056] The present invention fills the technological gap at home and abroad. In the field of non-destructive testing of tunnel lining structures, the present invention will lead the development direction of the industry, make outstanding contributions to the technological progress in related fields, provide technical support for related industries, and promote innovation and development in related fields.

[0057] Compared with previous technical means, the method of the present invention is faster and more efficient, and uses less time and manpower to complete the rapid detection of tunnel lining defects.

[0058] Embodiment 2, as Figure 2 As shown, the tunnel lining structure defect detection system provided by the embodiment of the present invention includes:

[0059] A vibration time domain signal detection module is used to arrange several detection areas at equal intervals on the tunnel lining structure to be tested, and to bond elastic sheets to each detection area;

[0060] The module for acquiring the spectrum characteristics of the tunnel lining structure is used to change the direction of the laser by moving the laser Doppler vibrometer, and sequentially project the laser onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are acquired by analyzing the spectrum of the vibration time domain signal;

[0061] The tunnel lining structure defect detection module is used to establish spectrum vibration damage indicators based on damage mechanics and vibration mechanics, and realize rapid quantitative detection of tunnel lining structure defects.

[0062] Embodiment 3, as Figure 3 to Figure 4 As shown, the detection device for tunnel lining structure defects based on laser Doppler vibration measurement technology provided by the embodiment of the present invention includes:

[0063] The laser Doppler nondestructive vibrometer 1 is equipped with a Vib20 data acquisition device 3, a digital audio cable, an integrated lithium battery power supply, a power adapter 4, etc. It is used to measure different concrete structures and tunnel lining structures, compare and analyze the inherent vibration characteristics of different concrete structures and tunnel lining structures, and detect and determine the damage in the tunnel lining structure.

[0064] The laser Doppler nondestructive vibrometer 1 is installed on the assembly platform; the laser Doppler nondestructive vibrometer 1 is connected to the data acquisition device 3 and the power adapter 4 of Vib20 respectively through a digital audio cable, and the power adapter 4 is also connected to an integrated lithium battery power supply. The laser Doppler vibrometer 1 is mounted on the tripod 2 of VIB-A-T01;

[0065] The laser Doppler nondestructive vibrometer 1 projects laser light onto the elastic sheet 6 to detect the vibration time domain signal of the tunnel lining structure;

[0066] The elastic sheet 6 is bonded to the tunnel lining structure and arranged in sequence on a plurality of detection areas 5 at equal intervals;

[0067] In the embodiment of the present invention, the structure of the elastic sheet 6 is designed as an L-shaped structure, which is divided into a bonding end 7 and a laser measuring end 8; the bonding end 7 is bonded to the detection area 5, and the laser measuring end 8 is used to receive the laser emitted by the laser Doppler nondestructive vibrometer 1 to detect the vibration time domain signal of the tunnel lining structure.

[0068] In the embodiment of the present invention, the L-shaped elastic sheet 6 has the following characteristics: the material of the elastic sheet has strong focusing property, and is made of polymer materials such as polyester film or polyimide film. The material is not easy to wear and age, so that the laser can be better focused on it and has good reflection performance. It can effectively reflect light at different angles, reduce reflection loss, and reflect the laser beam back to the receiver of the laser Doppler vibrometer. At the same time, it can improve the stability of the measured structure, reduce resonance, and thus improve the measurement accuracy during vibration measurement. It does not interfere with the laser emission and reflection path, can cope with measurements in various complex environments, and ensure the vibration measurement effect. The elastic sheet has excellent durability and can maintain its reflective performance for a long time. It has good resistance to changes in environmental conditions, sunlight, rain, and mechanical stress.

[0069] The elastic sheet 6 is small and convenient, lightweight, and can be carried at any time during experiments without taking up space. Its small size also makes it suitable for applications with limited space or requiring small vibration measurements.

[0070] The L-shaped elastic sheet pasting method has the following characteristics: the elastic sheet can be perfectly bonded to various complex concrete structures and tunnel lining structures, the softness of the adhesive is similar to that of silicone, epoxy resin materials and pressure-sensitive adhesives, etc., it has excellent bonding strength and chemical resistance, provides good bonding effect, can be adhered and peeled off multiple times without significantly reducing its pasting performance, has good reusability, and has high mechanical strength and stability after curing. It can greatly reduce the interference with the vibration measurement of the sheet. The adhesion is strong and not easy to fall off. After the experiment, you only need to easily turn the sheet to remove it. After use, the bonded concrete structure and tunnel lining structure will not stick, will not damage the concrete and tunnel lining structures, and will not leave any traces of the experiment.

[0071] In the experiment, the method for detecting defects in tunnel lining structure based on laser Doppler vibration measurement technology provided by the present invention was experimentally tested. Figure 5 Vibration time history graph, Figure 6 Vibration spectrum graph. Figure 7 Fundamental frequency damage curve; Experiments show that:

[0072] The invention proposes a method for quickly detecting structural defects of tunnel lining (concrete) based on laser Doppler vibrometer technology. The method uses an advanced laser Doppler vibrometer. The device has the advantages of simple and convenient use, variable measurement range, high-precision measurement, real-time monitoring, non-contact measurement, etc. The invention uses a light elastic sheet to significantly enhance the focusing effect of the laser Doppler vibrometer during measurement, shorten the focusing time, reduce the detection time, and will not be affected by the roughness of the surface of the measured object and will not cause any damage to the surface of the measured object, so that the accuracy of the measurement result is improved, the damaged structural defects can be quickly detected, and the detection efficiency is greatly improved. Therefore, the invention has strong practicality.

[0073] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated in one processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment.

[0074] An embodiment of the present invention further provides a computer device, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, wherein the processor implements the steps in any of the above-mentioned method embodiments when executing the computer program.

[0075] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the above-mentioned method embodiments can be implemented.

[0076] An embodiment of the present invention further provides an information data processing terminal, which, when executed on an electronic device, provides a user input interface to implement the steps in the above method embodiments. The information data processing terminal is not limited to mobile phones, computers, and switches.

[0077] An embodiment of the present invention further provides a server, which is used to provide a user input interface to implement the steps in the above method embodiments when executed on an electronic device.

[0078] An embodiment of the present invention provides a computer program product. When the computer program product runs on an electronic device, the electronic device can implement the steps in the above-mentioned method embodiments when executing the computer program product.

[0079] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the processes in the above-mentioned embodiment method, which can be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may at least include: any entity or device that can carry the computer program code to the camera / terminal device, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. For example, a USB flash drive, a mobile hard disk, a disk or an optical disk.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for detecting defects in tunnel lining structure, characterized in that: The method includes: S1, arranging several detection areas at equal intervals on the tunnel lining structure to be tested, and gluing elastic sheets to each detection area; S2, by moving the laser Doppler vibrometer to change the direction of the laser, the laser is sequentially projected onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are obtained by spectrum analysis of the vibration time domain signal; S3, based on damage mechanics and vibration mechanics, establish spectrum vibration damage index to achieve rapid quantitative detection of tunnel lining structure defects; In step S1, selecting the tunnel lining structure to be tested includes: according to the length characteristics of the tunnel lining structure, in accordance with the detection order of the arch bottom, arch waist, arch crown, arch waist, and arch crown of the tunnel lining, sequentially pasting the L-shaped elastic sheet on the detection area position; In step S2, the processing of the vibration time domain signal includes: obtaining a vibration time history curve by connecting a laser Doppler vibrometer and a data acquisition instrument to a control computer; performing a fast Fourier transform on the vibration time history curve to obtain a corresponding vibration spectrum curve; The external excitation force g(t) is an external excitation force with a period T tending to infinity, and the interval between adjacent frequencies is is an infinitesimal quantity, and the frequency is close to continuous distribution in the interval (-∞,∞); when Δω→0, the discrete variable ω n Transformed into a continuously changing frequency variable ω, the expression of the spectrum function is: Where G(ω) is the continuous spectrum function of the external excitation force g(t), g(t) is the external excitation force, t is the time variable, i is the imaginary unit in the complex function, ω is the angular frequency variable, e iωt is an exponential function with the natural constant e as base; In step S3, the spectrum vibration damage index is established based on damage mechanics and vibration mechanics, including: obtaining the natural vibration frequency of the lining structure under inspection through the spectrum characteristics of the vibration curve, comparing the frequency characteristics of the structure in the healthy and damaged states, and using the damage index to evaluate the lining damage degree in combination with vibration mechanics and damage mechanics. The material damage degree D ω The relationship between and its vibration frequency ω is: Where D ω is the degree of material damage, λ is the wavelength of vibration when the structure is in a healthy state, is the wavelength of vibration when the structure is damaged, ω1 is the natural vibration frequency when the material is healthy, is the natural vibration frequency of the structure in a damaged state, and the material damage degree D ω The value of is between 0 and 1. ω = 0, indicating that the lining structure is in the optimal state. ω =1, indicating that the tunnel lining structure is in the most unfavorable damage state; ρ is the density of the sound structure, is the density of the damaged structure; The L-shaped elastic sheet has a strong focusing property. It is made of polyester film or polyimide film polymer material. The material is not easy to wear and age, so that the laser can be focused and reflected on it. It reflects light at different angles, reduces reflection loss, and reflects the laser beam back to the receiver of the laser Doppler vibrometer. It does not interfere with the laser emission and reflection path, and can cope with measurements in various complex environments to ensure the vibration measurement effect. The elastic sheet is durable and maintains its reflective performance for a long time. It has good resistance to changes in environmental conditions, sunlight, rain and mechanical stress. The structure of the elastic sheet is designed to be an L-shaped structure, which is divided into a sticking end and a laser measuring end; the sticking end is bonded to the detection area, and the laser measuring end is used to receive the laser emitted by the laser Doppler non-destructive vibrometer to detect the vibration time domain signal of the tunnel lining structure; the sticking end is bonded to the detection area by one of silica gel, epoxy resin material and pressure-sensitive adhesive.

2. A tunnel lining structure defect detection system, characterized in that: The system is implemented by the method for detecting defects in tunnel lining structures according to claim 1, and the system comprises: A vibration time domain signal detection module is used to arrange several detection areas at equal intervals on the tunnel lining structure to be tested, and to bond elastic sheets to each detection area; The module for acquiring the spectrum characteristics of the tunnel lining structure is used to change the direction of the laser by moving the laser Doppler vibrometer, and sequentially project the laser onto the elastic sheet to detect the tunnel lining structure and collect the vibration time domain signal; the spectrum characteristics of the tunnel lining structure are acquired by analyzing the spectrum of the vibration time domain signal; The tunnel lining structure defect detection module is used to establish spectrum vibration damage indicators based on damage mechanics and vibration mechanics, and realize rapid quantitative detection of tunnel lining structure defects.

3. A device for detecting defects in tunnel lining structures, characterized in that: The device is implemented by the method for detecting defects in tunnel lining structures according to claim 1, and comprises: A laser Doppler nondestructive vibrometer (1) is mounted on a tripod (2) and is connected to a data acquisition device (3) and a power adapter (4) via a digital audio cable; The laser Doppler nondestructive vibrometer (1) projects laser light onto the elastic sheet (6) to detect the vibration time domain signal of the tunnel lining structure; The elastic sheet (6) is bonded to a plurality of detection areas (5) arranged at equal intervals in sequence on the tunnel lining structure; the structure of the elastic sheet (6) is designed to be an L-shaped structure, and is divided into a bonding end (7) and a laser measurement end (8); the bonding end (7) is bonded to the detection area (5), and the laser measurement end (8) is used to receive the laser emitted by the laser Doppler nondestructive vibrometer (1) to detect the vibration time domain signal of the tunnel lining structure; The sticking end (7) is bonded to the detection area (5) by means of one of silica gel, epoxy resin material and pressure-sensitive adhesive.

4. The device for detecting defects in tunnel lining structure according to claim 3, characterized in that: The power adapter (4) is also connected to an integrated lithium battery power source.

5. An application of the method for detecting defects in tunnel lining structures according to claim 1 to measure micro-vibrations in a limited space of a tunnel project.

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