Method and system for detecting voids in heterogeneous space under steel plates based on joint detection model

Abstract

The present invention relates to a method and system for detecting hollowing of heterogeneous space under steel plates based on a joint detection model. The method comprises the following steps: arranging a survey line on a steel-lined concrete structure, dividing the survey points at equal intervals along the survey line to form a grid, using an echo method to perform full-domain detection on each survey line, and collecting full-domain echo signals; obtaining a spectrum curve using fast Fourier transform according to the echo signal result, and screening the potential concrete hollowing defect area and hollowing area under the detection surface according to the spectrum curve; detecting the concrete hollowing defect area using a neutron scattering method, and collecting the thermal neutron count rate of each survey point on the survey line where the hollowing defect area is located; calculating the equivalent hollowing height value of each survey point according to the thermal neutron count rate result; and calculating the average hollowing height value by combining the hollowing area measured by the echo method and the equivalent hollowing height value measured by the neutron scattering method. The present invention can solve the problem that the accuracy and efficiency of hollowing detection of multi-layer heterogeneous space under steel plates in engineering cannot be taken into account at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of steel-lined concrete interface void detection, and in particular to a method and system for detecting voids in heterogeneous spaces under steel plates based on a joint detection model. Background Art

[0002] The deep-buried shield water tunnel adopts a composite lining structure, specifically a three-layer lining joint force type of "outer lining segment-self-compacting concrete filling layer-inner lining steel pipe". The steel lining is combined with the segment, and self-compacting concrete is poured between the steel lining and the segment to form a joint force integral lining structure to improve the overall bearing capacity of the lining structure. Due to the large cross-section, large water flow and high internal water pressure of the water tunnel, high requirements are placed on the quality of the structure, especially the quality of the self-compacting concrete pouring. The self-compacting concrete fills the gap between the external concrete segment and the steel plate lining. Due to the influence of the internal shear steel structure, the fluidity of the concrete will deteriorate, and it is easy to form a gap between the steel plate and the concrete. It cannot be directly observed, nor can it be detected from the surrounding rock segment side. The quality can only be inspected from the steel lining side.

[0003] The voids between the steel plate and the concrete are often filled with air or water, or both. In order to obtain void information from the multi-layer heterogeneous space formed by the void layer (air or water or air and water) under the steel plate and the concrete layer, the detection technology must be able to penetrate the steel plate and interact with the air, water, concrete and other media to produce differentiated measurable physical field quantities. At present, the main methods for detecting voids in steel-lined concrete include two categories: elastic wave method and ray method. The elastic wave method mainly includes ultrasonic method, impact echo method and impact imaging method; the ray method mainly includes infrared method, gamma ray method and neutron scattering method. Among them, conventional detection methods such as ultrasonic method, impact echo method, impact imaging method, infrared method, etc. have low accuracy and can only achieve qualitative detection or semi-quantitative detection; gamma ray method and neutron scattering method have high accuracy and can achieve quantitative detection, but gamma ray external irradiation damage is large, protection requirements are extremely high, and it is difficult to implement in engineering, while neutrons are easy to penetrate steel plates, have low energy, and are safer. Therefore, neutron scattering method is more suitable for use in engineering, but neutron scattering method takes more time than other conventional detection methods in quantitative detection. Therefore, it is urgent to provide a method for detecting the voidage of heterogeneous space under steel plates based on a joint detection model to overcome the above-mentioned defects of the prior art. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the technical defects existing in the prior art, and to propose a method and system for detecting voids in heterogeneous spaces under steel plates based on a joint detection model, which can solve the problem of the inability to balance accuracy and efficiency in detecting voids in multi-layer heterogeneous spaces formed by void layers (air or water or air and water) and concrete layers under steel plates in engineering.

[0005] In order to solve the above technical problems, the present invention utilizes the different propagation characteristics of elastic waves in steel plates, water, air, and concrete media, as well as the different slowing-down characteristics of fast neutrons in steel plates, water, air, and concrete media, and creatively provides a method for detecting voids in heterogeneous space under steel plates based on a joint detection model, comprising the following steps:

[0006] S1: Arrange the measuring lines in a circular manner on the steel-lined concrete structure to be inspected, and divide the measuring points at equal intervals along the measuring lines to form a grid. Use the echo method to perform full-area detection on each measuring line and collect the echo signals in the entire area.

[0007] S2: according to the echo signal result, a frequency spectrum curve is obtained by using fast Fourier transform, and the potential concrete void defect area and its void area under the detection surface are screened according to the frequency spectrum curve;

[0008] S3: Using neutron scattering method to detect the potential concrete void defect area obtained by screening, and collecting the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located;

[0009] S4: Calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result;

[0010] S5: Calculate the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method.

[0011] In one embodiment of the present invention, in S1, using the echo method to perform full-area detection on each survey line includes using a scanning impact echo instrument to perform full-area detection on each survey line in sequence.

[0012] In one embodiment of the present invention, in S2, the method of obtaining a spectrum curve by using fast Fourier transform according to the echo signal result includes:

[0013] The fast Fourier transform formula is:

[0014] ;

[0015] In the formula, F(ω) represents the frequency domain signal, f(t) represents the time domain signal, ω Indicates frequency, i Represents an imaginary unit.

[0016] In one embodiment of the present invention, in S2, the method for screening and obtaining the potential concrete void defect area under the detection surface according to the frequency spectrum curve includes:

[0017] The thickness D of the steel-lined concrete structure to be tested is calculated based on the peak frequency in the spectrum curve:

[0018] ;

[0019] In the formula, d represents the thickness of the steel lining, v s and v c denote the propagation speed of P wave in steel lining and concrete respectively, f denotes the dominant frequency, and β denotes the empirical correction parameter;

[0020] According to the thickness D, the potential concrete void defect area under the detection surface is screened.

[0021] In one embodiment of the present invention, in S3, detecting the potential concrete void defect areas obtained by screening using a neutron scattering method includes detecting the potential void defect areas obtained by screening using a void detector.

[0022] In one embodiment of the present invention, in S4, the method for calculating the equivalent void height value of each measuring point in the void defect area according to the thermal neutron count rate result includes:

[0023] Normalize the thermal neutron count rate results:

[0024] ;

[0025] In the formula, Indicates the reference value of thermal neutron count rate when calibrated under the same working conditions. Indicates i Line j The measured thermal neutron count rate values ​​are listed below. Indicates i Line j The normalized thermal neutron count rate values ​​are shown in the table;

[0026] Substitute the normalized thermal neutron count rate value into the calibration curve under the same working condition for calculation, and obtain the equivalent void height value of each measuring point in the void defect area:

[0027] ;

[0028] In the formula, h ij Indicates the equivalent void height value of each measuring point in the void defect area, a m is a constant, Indicates i Line j The normalized thermal neutron count rate values ​​are listed below: Indicates n ij The mth power, where m can be 0, 1, or 2.

[0029] In one embodiment of the present invention, in S5, the method for calculating the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method includes:

[0030] The calculation formula for the average clearance height is:

[0031] ;

[0032] In the formula, Indicates the average void height value, s n represents the area of ​​a single measurement point in the neutron scattering method, h ij Indicates the equivalent void height value of each measuring point in the void defect area. s i Represents the area of ​​a single measuring point using the echo method. i Indicates the number of echo measurement points in the hollow defect area. V Indicates the total concrete void volume in the void defect area. S It is the area of ​​the independent region screened by the echo method.

[0033] In addition, the present invention also provides a heterogeneous space under steel plate void detection system based on a joint detection model, comprising:

[0034] The echo detection module is used to arrange the measuring lines in a circular manner on the steel-lined concrete structure to be detected, and divide the measuring points along the measuring lines into a grid at equal intervals, and use the echo method to perform full-area detection on each measuring line to collect the echo signals in the whole area;

[0035] A void area screening module is used to obtain a frequency spectrum curve using fast Fourier transform according to the echo signal result, and to screen and obtain potential concrete void defect areas and void areas under the detection surface according to the frequency spectrum curve;

[0036] A neutron scattering detection module, which is used to detect the potential concrete void defect area obtained by screening using the neutron scattering method, and collect the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located;

[0037] An equivalent void height calculation module is used to calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result;

[0038] The joint calculation module is used to calculate the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method.

[0039] Furthermore, the present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method when executing the program.

[0040] Furthermore, the present invention further provides a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, the steps of the above-mentioned method are implemented.

[0041] The above technical solution of the present invention has the following advantages compared with the prior art:

[0042] The present invention provides a method and system for detecting voiding in heterogeneous spaces under steel plates based on a joint detection model, which can be applicable to water conveyance tunnels with a composite lining structure, and can perform rapid and accurate screening and quantitative and accurate detection of voiding at the steel lining concrete interface therein, thereby effectively evaluating the quality of self-compacting concrete pouring between the steel lining and the pipe segment in the water conveyance tunnel with a composite lining structure, and can solve the problem of the inability to balance accuracy and efficiency in detecting voiding in multi-layer heterogeneous spaces formed by voiding layers (air or water or air and water) and concrete layers under steel plates in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of a method for detecting voids in heterogeneous spaces under steel plates based on a joint detection model proposed by the present invention.

[0044] Figure 2 It is a schematic diagram of the survey line arrangement in step S1 of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0046] Reference Figure 1 As shown, an embodiment of the present invention provides a method for detecting voids in heterogeneous space under a steel plate based on a joint detection model, comprising the following steps:

[0047] S1: Arrange the measuring lines in a circular manner on the steel-lined concrete structure to be inspected, and divide the measuring points at equal intervals along the measuring lines to form a grid. Use the echo method to perform full-area detection on each measuring line and collect the echo signals in the entire area.

[0048] S2: according to the echo signal result, a frequency spectrum curve is obtained by using fast Fourier transform, and the potential concrete void defect area and its void area under the detection surface are screened according to the frequency spectrum curve;

[0049] S3: Using neutron scattering method to detect the potential concrete void defect area obtained by screening, and collecting the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located;

[0050] S4: Calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result;

[0051] S5: Calculate the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method.

[0052] The present invention provides a method for detecting voiding in heterogeneous spaces under steel plates based on a joint detection model, which can be applicable to water conveyance tunnels with a composite lining structure, and can perform rapid and accurate screening and quantitative and accurate detection of voiding at the steel lining concrete interface therein, thereby effectively evaluating the quality of self-compacting concrete pouring between the steel lining and the pipe segment in the water conveyance tunnel with a composite lining structure, and can solve the problem of the inability to balance accuracy and efficiency in detecting voiding in multi-layer heterogeneous spaces formed by voiding layers (air or water or air and water) and concrete layers under steel plates in engineering.

[0053] In step S1, the measuring line B can be arranged circumferentially according to the structural form (refer to the tunnel drawings), and the measuring points can be divided into grids at equal intervals along the measuring line B. For example, the inner lining steel pipe structure of the water supply tunnel in a large-scale water supply project is composed of 3m long steel pipes welded circumferentially, in which the reinforcement ring A is arranged at intervals of 1.2m for structural safety considerations. According to the steel pipe structure, two adjacent sections of 6m long steel pipes are selected as a detection unit, and the arrangement of the measuring line B is as follows: Figure 2 As shown, they are arranged at intervals of 20 cm. After the survey line B is arranged, a scanning impact echo instrument can be used to quickly perform a full-area detection on each survey line B. The working principle of the scanning impact echo instrument is a prior art, and the present invention will not be elaborated here.

[0054] In step S2, the frequency spectrum curve is obtained by using fast Fourier transform according to the echo signal result, wherein the fast Fourier transform formula is: (1), where F(ω) represents the frequency domain signal, f(t) represents the time domain signal, ω Indicates frequency, i Represents an imaginary unit. Then the thickness D of the steel-lined concrete structure to be tested is calculated based on the peak frequency in the spectrum curve: (2), where d represents the thickness of the steel lining, v s and v c represents the propagation speed of P wave in steel lining and concrete, f represents the dominant frequency, and β represents the empirical correction parameter; finally, the potential concrete void defect area under the detection surface is screened according to the thickness D, the plane position of the void defect area is given, and the void height range of the void defect area is preliminarily determined (0~5mm, 5~10mm, 10~15mm..., marked with the maximum void). For example, the scanning impact echo fine screening results can be shown in Table 1.

[0055] Table 1

[0056]

[0057] Among them, in step S3, the result information such as the compaction and void position, void area and preliminary void height range can be fed back to the neutron scattering method, and the screened potential void area can be detected using the steel-lined concrete void detector to collect the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located.

[0058] In step S4, the thermal neutron count rate result is specifically normalized:

[0059] ; (3)

[0060] In the formula, Indicates the reference value of thermal neutron count rate when calibrated under the same working conditions. Indicates i Line j The measured thermal neutron count rate values ​​are listed below. Indicates i Line j The normalized thermal neutron count rate values ​​are shown in the table;

[0061] Substitute the normalized thermal neutron count rate value into the calibration curve under the same working condition for calculation, and obtain the equivalent void height value of the measuring point:

[0062] ; (4)

[0063] In the formula, h ij Indicates the equivalent void height value of each measuring point in the void defect area, a m is a constant, Indicates i Line j The normalized thermal neutron count rate values ​​are listed below: Indicates n ij The mth power, m takes the value of 0, 1, 2. For example, the precise measurement results of the neutron scattering method can be shown in Table 2.

[0064] Table 2

[0065]

[0066] In step S5, the void area measured by the combined echo method and the equivalent void height value measured by the neutron scattering method are specifically used to calculate the average void height value of the independent region. The void shape is often irregular, and may be within a neutron scattering method measurement point (20cm×20cm), or may span multiple 20cm×20cm areas. Here, the independent region refers to the projection shape of an independent void on the steel lining. The calculation formula for the average void height value is:

[0067] ; (5)

[0068] In the formula, Indicates the average void height value, s n represents the area of ​​a single measurement point in the neutron scattering method, h ij Indicates the equivalent void height value of each measuring point in the void defect area, s i It represents the area of ​​a single measuring point of the echo method, i represents the number of measuring points of the echo method in the void defect area, V represents the total concrete void volume in the void defect area, V is measured by neutron scattering method, the area of ​​a single point of the echo method can be as small as 5cm×10cm, or even 5cm×5cm, which is more accurate in describing the projection shape of the void on the steel lining, the area of ​​a single point of the neutron scattering method is 20cm×20cm, the detected void height is the average void height under the area of ​​20cm×20cm, but it is more accurate in detecting the concrete void volume. S is the area of ​​the independent area screened by the echo method, S can be measured by the echo method to multiply the number of points with voids by the area of ​​a single point, the echo method has more advantages here, the size of the measuring point of the neutron scattering method is fixed for each measurement and is several times larger than the area of ​​the echo method.

[0069] The single point area of ​​the echo method can be as small as 5cm×10cm, or even 5cm×5cm, which can more accurately depict the projection shape of the void on the steel lining surface. The single point area of ​​the neutron scattering method is 20cm×20cm, and the detected void height is the average void height under the 20cm×20cm area, but it is more accurate in detecting the amount of concrete voids. The two methods are combined through parameter mutual feedback to make the height of concrete voids closer to the actual voids, that is, the void amount of the neutron scattering method is divided by the void area detected by the echo method as the average void height of the steel-lined concrete.

[0070] The method of the present invention uses the average void height value result to evaluate the pouring quality of self-compacting concrete between the steel lining and the pipe segment in the water conveyance tunnel of the composite lining structure, and guides the construction unit to strengthen the structure.

[0071] Corresponding to the embodiment of the above method, the embodiment of the present invention also provides a heterogeneous space void detection system under the steel plate based on a joint detection model. The heterogeneous space void detection system under the steel plate based on a joint detection model described below and the heterogeneous space void detection method under the steel plate based on a joint detection model described above can be referenced to each other.

[0072] The present invention also provides a heterogeneous space under steel plate void detection system based on a joint detection model, comprising:

[0073] The echo detection module is used to arrange the measuring lines in a circular manner on the steel-lined concrete structure to be detected, and divide the measuring points along the measuring lines into a grid at equal intervals, and use the echo method to perform full-area detection on each measuring line to collect the echo signals in the whole area;

[0074] A void area screening module is used to obtain a frequency spectrum curve using fast Fourier transform according to the echo signal result, and to screen and obtain potential concrete void defect areas and void areas under the detection surface according to the frequency spectrum curve;

[0075] A neutron scattering detection module, which is used to detect the potential concrete void defect area obtained by screening using the neutron scattering method, and collect the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located;

[0076] An equivalent void height calculation module is used to calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result;

[0077] The joint calculation module is used to calculate the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method.

[0078] The present invention provides a system for detecting voiding in heterogeneous spaces under steel plates based on a joint detection model, which can be applicable to water conveyance tunnels with a composite lining structure, and can perform rapid and accurate screening and quantitative and accurate detection of voiding at the steel lining concrete interface therein, thereby effectively evaluating the quality of self-compacting concrete pouring between the steel lining and the pipe segment in the water conveyance tunnel with a composite lining structure, and can solve the problem of the inability to balance accuracy and efficiency in detecting voiding in multi-layer heterogeneous spaces formed by voiding layers (air or water or air and water) and concrete layers under steel plates in engineering.

[0079] Corresponding to the above method embodiment, an embodiment of the present invention further provides a computer device, including:

[0080] A memory for storing computer programs;

[0081] A processor is used to implement the steps of the above-mentioned method for detecting voids in heterogeneous space under a steel plate based on a joint detection model when executing a computer program.

[0082] In the embodiment of the present invention, the processor may be a central processing unit (CPU), an application specific integrated circuit, a digital signal processor, a field programmable gate array or other programmable logic devices.

[0083] The processor can call the program stored in the memory. Specifically, the processor can execute the operations in the embodiment of the above-mentioned method for detecting voids in heterogeneous space under steel plates based on the joint detection model.

[0084] The memory is used to store one or more programs, which may include program codes, and the program codes include computer operating instructions.

[0085] In addition, the memory may include a high-speed random access memory and may also include a non-volatile memory, such as at least one disk storage device or other volatile solid-state storage device.

[0086] Corresponding to the above method embodiments, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned method for detecting voids in heterogeneous spaces under steel plates based on a joint detection model are implemented.

[0087] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0088] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0089] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0090] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0091] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for detecting voids in heterogeneous spaces under steel plates based on a joint detection model, characterized in that: The following steps are involved: S1: Arrange the measuring lines in a circular manner on the steel-lined concrete structure to be inspected, and divide the measuring points at equal intervals along the measuring lines to form a grid. Use the echo method to perform full-area detection on each measuring line and collect the echo signals in the entire area. S2: according to the echo signal result, a frequency spectrum curve is obtained by using fast Fourier transform, and the potential concrete void defect area and its void area under the detection surface are screened according to the frequency spectrum curve; S3: Using neutron scattering method to detect the potential concrete void defect area obtained by screening, and collecting the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located; S4: Calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result; S5: Calculate the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method; In S2, the method for screening and obtaining the potential concrete void defect area under the detection surface according to the frequency spectrum curve includes: calculating and obtaining the thickness D of the steel-lined concrete structure to be detected according to the peak frequency in the frequency spectrum curve: D=[2d+(1 / f-2d / v s )v c ]β / 2; In the formula, d represents the thickness of the steel lining, v s and v c denote the propagation speed of P wave in steel lining and concrete respectively, f denotes the dominant frequency, and β denotes the empirical correction parameter; The potential concrete void defect area under the detection surface is screened according to the thickness D; In S4, a method for calculating the equivalent void height value of each measuring point in the void defect area according to the thermal neutron count rate result includes: Normalize the thermal neutron count rate results: Where n0 represents the reference value of thermal neutron count rate when calibrated under the same working condition, n′ ij represents the thermal neutron count rate value measured in the i-th row and j-th column, n′ ij represents the normalized thermal neutron count rate value of the i-th row and j-th column; Substitute the normalized thermal neutron count rate value into the calibration curve under the same working condition for calculation, and obtain the equivalent void height value of each measuring point in the void defect area: In the formula, h ij Indicates the equivalent void height value of each measuring point in the void defect area, a m is a constant, n′ ij represents the normalized thermal neutron count rate value of the i-th row and j-th column, Indicates n ij The mth power, where m can be 0, 1, or 2.

2. According to claim 1, a method for detecting voids in heterogeneous space under a steel plate based on a joint detection model is characterized in that: In S1, performing full-area detection on each survey line using the echo method includes performing full-area detection on each survey line in sequence using a scanning impact echo instrument.

3. The method for detecting voids in heterogeneous space under a steel plate based on a joint detection model according to claim 1 or 2, characterized in that: In S2, according to the echo signal result, a method of obtaining a spectrum curve by using fast Fourier transform includes: the fast Fourier transform formula is: Where F(ω) represents the frequency domain signal, f(t) represents the time domain signal, ω represents the frequency, and i represents the imaginary unit.

4. The method for detecting voids in heterogeneous spaces under steel plates based on a joint detection model according to claim 3 is characterized in that: In S3, using a neutron scattering method to detect the potential concrete void defect areas obtained by screening includes using a void detector to detect the potential void areas obtained by screening.

5. The method for detecting voids in heterogeneous spaces under steel plates based on a joint detection model according to claim 3 is characterized in that: In S5, the method for calculating the average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method includes: The calculation formula for the average clearance height is: In the formula, Indicates the average void height value, s n Represents the area of ​​a single measurement point in the neutron scattering method, h ij Indicates the equivalent void height value of each measuring point in the void defect area, s i It represents the area of ​​a single measuring point of the echo method, i represents the number of measuring points of the echo method in the void defect area, V represents the total amount of concrete voids in the void defect area, and S is the area of ​​the independent area screened out by the echo method.

6. A heterogeneous space under steel plate void detection system based on a joint detection model, characterized in that: include: The echo detection module is used to arrange the measuring lines in a circular manner on the steel-lined concrete structure to be detected, and divide the measuring points along the measuring lines into a grid at equal intervals, and use the echo method to perform full-area detection on each measuring line to collect the echo signals in the whole area; A void area screening module is used to obtain a frequency spectrum curve using fast Fourier transform according to the echo signal result, and to screen and obtain potential concrete void defect areas and void areas under the detection surface according to the frequency spectrum curve; A neutron scattering detection module, which is used to detect the potential concrete void defect area obtained by screening using the neutron scattering method, and collect the thermal neutron count rate of each measuring point on the measuring line where the void defect area is located; An equivalent void height calculation module is used to calculate the equivalent void height value of each measuring point in the void defect area according to the thermal neutron counting rate result; A joint calculation module, which is used to calculate an average void height value by combining the void area measured by the echo method and the equivalent void height value measured by the neutron scattering method; In the void area screening module, a method for screening and obtaining a potential concrete void defect area under the detection surface according to the frequency spectrum curve includes: The thickness D of the steel-lined concrete structure to be tested is calculated based on the peak frequency in the spectrum curve: D=[2d+(1 / f-2 d / v s ]β / 2; In the formula, d represents the thickness of the steel lining, v s and v c denote the propagation speed of P wave in steel lining and concrete respectively, f denotes the dominant frequency, and β denotes the empirical correction parameter; The potential concrete void defect area under the detection surface is screened according to the thickness D; In the equivalent void height calculation module, a method for calculating the equivalent void height value of each measuring point in the void defect area according to the thermal neutron count rate result includes: Normalize the thermal neutron count rate results: Where n0 represents the reference value of thermal neutron count rate when calibrated under the same working condition, n ij represents the thermal neutron count rate value measured in the i-th row and j-th column, n′ ij represents the normalized thermal neutron count rate value of the i-th row and j-th column; Substitute the normalized thermal neutron count rate value into the calibration curve under the same working condition for calculation, and obtain the equivalent void height value of each measuring point in the void defect area: In the formula, h ij Indicates the equivalent void height value of each measuring point in the void defect area, a m is a constant, n′ ij represents the normalized thermal neutron count rate value of the i-th row and j-th column, Indicates n ij The mth power, where m can be 0, 1, or 2.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps of the method according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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