Non-contact detection system and method for segment grouting layer thickness based on structural vibration spectrum

Abstract

The present invention relates to a non-contact detection system and method for the thickness of a tunnel segment grouting layer based on a structural vibration spectrum. The system comprises a speaker, a laser interferometer optical head, a power amplifier, a signal generator, a laser interferometer control box, a power supply, and a laptop computer integrated with excitation control software. The speaker is connected to the power amplifier, the laser interferometer optical head is connected to the laser interferometer control box, the power amplifier is connected to the signal generator, and both the signal generator and the laser interferometer control box are connected to the laptop computer. The signal generator, power amplifier, and laser interferometer control box are all connected to the power supply. The signal generator generates a swept frequency excitation signal, which is played by the speaker via the power amplifier and acts on the tunneling segment and its grouting layer, inducing vibration. The signal is then synchronously collected by the laser interferometer optical head and the laser interferometer control box and input into the excitation control software in the laptop computer for real-time processing, thereby achieving non-contact detection of the thickness of the tunnel segment grouting layer. Compared with existing technologies, the present invention has the advantages of high efficiency and accurate detection.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering detection, and in particular to a non-contact detection system and method for the thickness of a pipe segment grouting layer based on a structural vibration spectrum. Background Art

[0002] In alluvial plains, the underground soil is soft and contains a high moisture content. These geological conditions are highly conducive to shield tunneling. During operation, the shield machine simultaneously performs multiple processes, including tunnel excavation, tunnel wall laying, and segment backfilling, significantly improving construction efficiency. The primary purpose of the grouting process is to fill the gaps between the segments and the soil, inhibiting loosening and preventing ground deformation around the tunnel. Insufficient grouting or a thin grouting layer will result in inadequate filling of the gaps in the segment wall, causing ground deformation. Excessive grouting or excessive grouting layer thickness will cause slurry to overflow from the shield tail or grouting holes, and even cause segment floating. The thickness of the backfill grouting layer directly affects the settlement of the surrounding ground and the stability of the tunnel structure. Therefore, measuring the thickness of the shield backfill grouting layer is particularly important.

[0003] After grouting of shield segments, inspection of the grouting layer is a concealed process. Related inspection methods include core drilling. This method uses a specialized coring machine to create a window in the shield segment, extract a core sample, and analyze the grouting layer thickness. Coring can cause damage to the shield segment, and the equipment is bulky, inconvenient, and uneconomical. Ultrasonic methods use the acoustic time delay of reflected echoes from layered interfaces to detect structural thickness. However, ultrasonic waves typically have a short wavelength and weak penetration, making them difficult to inspect on large structures like shield segments. Even increasing the wavelength and penetration improves detection accuracy, resulting in low reliability. Ground-penetrating radar (GPR) uses electromagnetic waves for inspection. This method produces a series of radar scan images, requiring extensive experience to accurately identify structural interfaces. Furthermore, the dense steel cages within the shield segments strongly reflect electromagnetic waves from the metal, masking the reflected signals from the grouting layer interfaces. Therefore, it is difficult to detect the thickness of the grouting layer of the shield segment using the ground penetrating radar method, and it requires very high capabilities and on-site experience of the detection personnel.

[0004] In addition to the aforementioned methods, the impact echo method is a relatively common method for inspecting concrete structures. The basic principle of this method is to use a spherical impact hammer to strike the surface of a shield segment, thereby exciting elastic waves. These waves repeatedly reflect back and forth between the bottom and top surfaces of the structure, generating a signal. This time-domain signal is then converted into a frequency spectrum reflecting its frequency domain characteristics using frequency-domain analysis techniques such as fast Fourier transform. The inspection results of this method are affected by the operator's hammering force and direction, which is a significant human factor. Different operators can produce completely different inspection results, resulting in poor consistency. However, the impact echo method can determine the resonant frequency of the shield segment grouting structure. Pan Yongdong's article, "Numerical Simulation and Application of the Impact Echo Method to Tunnel Lining Structures," also points out that this characteristic is closely related to the thickness of the shield segment grouting layer. Therefore, analyzing the resonant frequency characteristics of the inspection structure's vibration spectrum is also an effective method for detecting the thickness of the shield segment grouting layer.

[0005] Based on this, further research is still needed in this field to eliminate the use of artificial hammers to excite structural vibrations and to develop a method to detect the thickness of the grouting layer behind the shield segment wall based on the resonant frequency in the structural vibration spectrum. Summary of the Invention

[0006] The purpose of the present invention is to provide a non-contact detection system and method for the thickness of shield segment grouting layer based on structural vibration spectrum, which can improve the accuracy and reliability of shield segment thickness detection.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A non-contact detection system for the thickness of a pipe segment grouting layer based on a structural vibration spectrum comprises a speaker, a laser interferometer optical head, a power amplifier, a signal generator, a laser interferometer control box, a power supply, and a laptop computer integrated with excitation control software. The speaker is connected to the power amplifier, the laser interferometer optical head is connected to the laser interferometer control box, the power amplifier is connected to the signal generator, the signal generator and the laser interferometer control box are both connected to the laptop computer, the signal generator, the power amplifier, and the laser interferometer control box are all connected to the power supply, the signal generator generates a swept frequency excitation signal, which is played out by the speaker through the power amplifier and acts on a shield pipe segment and its grouting layer, inducing vibration. The signal is then synchronously collected by the laser interferometer optical head and the laser interferometer control box and input into the excitation control software in the laptop computer for real-time processing, thereby realizing non-contact detection of the thickness of the pipe segment grouting layer.

[0009] Furthermore, the detection system is installed on a mobile rail vehicle.

[0010] Furthermore, the signal generator is connected to the power amplifier via a TRS cable.

[0011] Furthermore, a tripod is included, and the tripod is used to support the laser interferometer optical head.

[0012] The present invention further provides a detection method for the segment grouting layer thickness non-contact detection system based on the structural vibration spectrum described above, comprising the following steps:

[0013] 1) Determine n shield segments to be inspected and m inspection points on each shield segment to be inspected;

[0014] 2) adjusting the horn and the laser interferometer optical head to align with the detection point on the shield segment to be detected;

[0015] 3) The sweep frequency excitation signal sweep range and frequency detection points are set on the excitation control software in the laptop computer. The signal generator generates a sweep frequency excitation signal, which is input into the power amplifier. The speaker then emits a sweep frequency acoustic vibration signal, which acts on the shield segment to be tested and its grouting layer, inducing vibration.

[0016] 4) The laser interferometer optical head and the laser interferometer control box synchronously collect the swept frequency acoustic vibration signals acting on the shield segment to be inspected and its grouting layer, and input them into the excitation control software in the laptop computer for real-time processing to obtain the vibration spectrum at the inspection point;

[0017] 5) Repeat steps 2)-4) m-1 times to complete the inspection of m inspection points on the shield segment to be inspected;

[0018] 6) averaging the vibration spectra of the m detection points to obtain an average vibration spectrum, which is used as the vibration spectrum of the grouting layer of the shield segment to be detected;

[0019] 7) Analyzing and calculating based on the average vibration spectrum to obtain the thickness of the grouting layer of the shield segment to be tested;

[0020] 8) Repeat steps 2)-7) n-1 times to complete the inspection of the grouting layer thickness of all shield segments to be inspected.

[0021] Furthermore, the following steps are included between step 2) and step 3):

[0022] Turn on the laser interferometer optical head and the laser interferometer control box to locate the tracing light spot at the detection point, and adjust the focal length and inclination of the laser interferometer optical head to adjust the reflection intensity;

[0023] Turn on the speaker, power amplifier and signal generator, and adjust the intensity of the sweep excitation signal.

[0024] Furthermore, the vibration spectrum at the detection point is obtained by processing the excitation control software using a time-frequency conversion algorithm.

[0025] Furthermore, the vibration spectrum of the shield segment grouting layer to be tested is expressed as:

[0026]

[0027] Where A i is the vibration spectrum of the grouting structure of the i-th shield segment, m is the number of points to be measured on the shield segment, A ij is the vibration spectrum of the jth measured point on the i-th shield segment grouting structure.

[0028] Furthermore, in step 7), the step of obtaining the thickness of the grouting layer of the shield segment to be tested includes:

[0029] Analyze the average vibration spectrum to obtain the resonance frequency of the grouting layer of the shield segment to be tested;

[0030] Calculating the offset of the resonance frequency of the grouting layer of the shield segment to be tested relative to the resonance frequency of the individual shield segment;

[0031] Based on the corresponding relationship between the offset and the thickness of the grouting layer, the thickness of the grouting layer of the shield segment to be inspected is obtained.

[0032] Furthermore, the calculation expression of the offset is:

[0033] Δf i =f i -f0

[0034] Where Δf i is the shield segment resonance frequency f i The shift relative to the resonant frequency f0 of the individual segment structure.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The detection system of the present invention generates a sweep frequency excitation signal through a signal generator, and then plays an output acoustic vibration signal through a power amplifier and a speaker, and acts on the shield segment and the grouting layer to induce their vibration. The vibration is then collected and analyzed by a laser interferometer. The acoustic vibration excitation and laser non-contact detection are innovatively used for the stimulation and perception of structural vibration. The shield segment is not touched during the entire detection process, and manual knocking operations are avoided. This not only eliminates the influence of the subjective factors of the detection personnel on the detection results, but also makes the detection results more accurate and reliable.

[0037] (2) The detection method of the present invention adopts an advanced detection system to collect and process the detection signals, and detects the thickness of the grouting layer by comparing and analyzing the vibration spectrum of each measuring point on each pipe segment. At the same time, it can be integrated into the existing tunnel inspection device, thereby realizing an efficient, stable and easy-to-operate non-destructive detection method.

[0038] (3) The present invention evaluates the structural properties of the shield segment grouting structure by detecting the vibration spectrum thereof, and realizes non-contact excitation and perception of the vibration characteristics of the shield segment structure based on acoustic vibration excitation and laser vibration measurement. The operation is convenient, the execution is efficient, and the results are accurate. In addition, the implementation process adopts a non-contact method, which can realize automated operation and improve the convenience of on-site detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the system structure of the present invention;

[0040] Figure 2 Schematic diagram of the method flow of the present invention;

[0041] Figure 3 is the average vibration spectrum of three shield segment grouting structures in the embodiment of the present invention;

[0042] In the figure: 1. Speaker; 2. Laser interferometer optical head; 3. Tripod; 4. Power amplifier; 5. Signal generator; 6. Laser interferometer control box; 7. Power supply; 8. Laptop computer. DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0044] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0045] The following describes some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0046] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0047] This embodiment provides a non-contact detection system for the thickness of the segment grouting layer based on the structural vibration spectrum. Figure 1As shown, the system includes a speaker 1, a laser interferometer optical head 2, a tripod 3, a power amplifier 4, a signal generator 5, a laser interferometer control box 6, a power supply 7, and a laptop computer 8. The laser interferometer optical head 2 is supported by the tripod 3 and is connected to each detection device in sequence. The signal generator 5 is connected to the power amplifier 4 via a TRS (Tip-Ring-Sleeve) cable. The power amplifier 4 is connected to the speaker 1. The laser interferometer optical head 2 is connected to the laser interferometer control box 6. The signal amplifier 5 and the laser interferometer control box 6 are connected to the laptop computer 8. The signal generator 5, the power amplifier 4, and the laser interferometer control box 6 are connected to the power supply 7.

[0048] The detection system is used to conduct non-contact detection of the thickness of the shield segment grouting layer, such as Figure 2 As shown, the non-contact detection method includes the following steps:

[0049] S1. Determine n shield segments to be inspected, record the numbers of the shield segments to be inspected, select m points on each shield segment to be inspected as inspection points, and record the positions of the inspection points.

[0050] S2. Select appropriate locations in the tunnel to place the detection components. Figure 1 Connect to form the above detection system.

[0051] The detection system can be placed on a mobile rail vehicle and moved by the mobile rail vehicle.

[0052] S3. Adjust the position of the speaker 1 and the laser interferometer optical head 2 so that they are as close to the pipe segment to be inspected as possible.

[0053] S4. Turn on the laser interferometer control box 6 and the laser interferometer optical head 2 so that the tracing light spot is located on the measuring point, and adjust the focal length and inclination angle of the laser interferometer optical head 2 so that the reflection intensity meets the detection requirements.

[0054] S5. Turn on the signal generator 5, the power amplifier 4 and the speaker 1, fix the excitation signal frequency, adjust the excitation signal strength, and measure the sound intensity of the actual output acoustic vibration signal of the speaker 1 propagating to the surface of the shield segment to ensure that the sound intensity meets the detection requirements.

[0055] Specifically, in step S5, the intensity of the excitation signal is adjusted until the intensity of the acoustic vibration signal output by the loudspeaker 1 at the surface of the shield segment is not less than 90 dB.

[0056] S6. Adjust the sweep frequency range and the number of frequency detection points of the excitation signal. The speaker 1 outputs the sweep frequency acoustic vibration signal. The laser interferometer optical head 2 and the laser interferometer control box 6 collect the vibration signal. The supporting software of the laser interferometer in the laptop computer 8 processes the vibration signal into a vibration spectrum A through a time-frequency conversion algorithm. ij , and displayed in real time.

[0057] Specifically, in step S6, the excitation signal frequency sweep range can be set to 1 kHz-8 kHz, and the number of frequency detection points can be set to 300.

[0058] S7. After completing the inspection of one measuring point, inspect the next measuring point and repeat steps S4-S6 until all inspection points of the segment are inspected.

[0059] S8. Average the vibration spectra collected at different detection points on the same shield segment. The average vibration spectrum obtained is the vibration spectrum of the shield segment grouting structure.

[0060] S9. Analyze the average vibration spectrum to obtain the value of its resonant frequency fi, and calculate the offset Δf of its resonant frequency relative to the resonant frequency f0 of the individual segment structure. i =f i -f0, determine the thickness of the shield segment grouting layer t i ;

[0061] Specifically, in step S9 , the shift of the resonance frequency of the vibration spectrum of the structures with different grouting layer thicknesses relative to the resonance frequency of the individual segment structure can be obtained through numerical simulation or standard specimen testing.

[0062] S10. After inspecting one pipe segment, inspect the next pipe segment and repeat steps S3-S9 until all the pipe segments to be inspected have been inspected.

[0063] Specifically, in step S10, if the inspection device is placed on a mobile rail vehicle, the mobile rail vehicle can be directly dragged so that the inspection device faces the next inspection segment.

[0064] S11. Remove the equipment connection, organize the test data, and the test is completed.

[0065] This embodiment also uses the above detection system and method to detect the shield segment grouting structure of a certain underground rail transit construction site in an actual application scenario. The Young's modulus of the concrete segment is 34.5GPa and the density is 2200kg / m 3 The Young's modulus of the grouting layer is 25GPa and the density is 2200kg / m 3 The detection steps are as follows:

[0066] Step 1: Randomly select three shield segments from the site for inspection, label them #1, #2, and #3 respectively. Select three points on each segment as inspection points and record the locations of the inspection points.

[0067] Step 2: Place all equipment on the railcar, with the laser interferometer 2 supported by a tripod 3. Connect each detection device in sequence: the signal generator 5 is connected to the power amplifier 4 via a cable, the power amplifier 4 is connected to the speaker 1, the laser interferometer optical head 2 is connected to the laser interferometer control box 6, the signal amplifier 5 and the laser interferometer control box 6 are connected to the laptop 8, and the signal generator 5, the power amplifier 4, and the laser interferometer control box 6 are connected to the power supply 7.

[0068] Step 3: Adjust the position of speaker 1 and laser interferometer optical head 2 so that they are aligned with the detection point on the #1 segment as much as possible.

[0069] Step 4: Turn on the laser interferometer control box 6 and the laser interferometer optical head 2 so that the tracing light spot is located at the first detection point, and adjust the focal length and inclination angle of the laser interferometer optical head 2 so that its reflection intensity meets the detection requirements.

[0070] Step 5. Turn on the signal generator 5, power amplifier 4 and speaker 1, adjust the excitation signal frequency to 2kHz, adjust the intensity adjustment knob on the power amplifier 4 to adjust the excitation signal intensity, place the sound pressure meter close to the first detection point on the surface of the shield segment, and measure the sound intensity of the actual output acoustic vibration signal of the speaker 1 propagated to the detection point. While turning the intensity adjustment knob, observe the sound pressure meter reading until the sound pressure meter reading reaches 90dB. At this time, the excitation acoustic vibration signal intensity meets the detection requirements.

[0071] Step 6: Set the excitation signal sweep frequency range to 1kHz-8kHz and the frequency detection points to 300 in the excitation control software in the laptop computer 8, turn on the signal generator 5, and the speaker 1 outputs the sweep frequency acoustic vibration signal. The laser interferometer optical head 2 and the control box 6 synchronously collect the vibration signal. The supporting software of the laser interferometer in the laptop computer 8 processes and displays the vibration spectrum A at the detection point in real time. 11 .

[0072] Step 7: After the vibration spectrum of the first detection point is collected, detect the next detection point and repeat steps 4 to 6 until the vibration spectrum of the three detection points on the segment A is obtained. 11 、A 12 、A 13 Collection completed.

[0073] Step 8: average the vibration spectra collected at all detection points on the first shield segment, and obtain the average vibration spectrum of the first segment A1 = (A 11 +A 12 +A 13 ) / 3, such as Figure 3 shown.

[0074] Step 9: Numerical simulation was used to determine the offset of the resonance frequencies of the vibration spectra for structures with varying grouting layer thicknesses relative to the resonance frequencies of the individual segments, as shown in Table 1. Analysis of the average vibration spectrum A1 of the first segment revealed a resonance peak f1 of 6.27 kHz, a resonance peak f0 of 6.60 kHz for the individual shield segment structure, and a resonance frequency offset Δf1 of -0.33 kHz. Based on the relationship between the resonance frequency offset and grouting layer thickness shown in Table 1, linear interpolation determined that the grouting layer thickness t1 of segment #1 was 16.5 mm.

[0075] Table 1 Standard correspondence between structural resonance frequency and shield segment grouting layer thickness

[0076] Thickness of grouting layer / mm 0 10 20 30 40 50 60 Resonance frequency shift / kHz 0 -0.2 -0.4 -0.6 -0.7 -0.9 -1.0 Thickness of grouting layer / mm 70 80 90 100 110 120 130 Resonance frequency shift / kHz -1.2 -1.3 -1.5 -1.6 -1.7 -1.9 -2.0

[0077] Step 10: Move the rail car so that the detection device faces the #2 segment, repeat steps 3 to 9, and obtain the average vibration spectrum A2 of the #2 segment, as shown in Figure 3 As shown, the resonance frequency f2 of the #2 segment is 6.27kHz, and the resonance frequency offset Δf2 is -0.33kHz. According to Table 1, the thickness of the grouting layer of the #2 segment can be calculated by interpolation to be 16.5mm. Move the railcar again so that the detection device is facing the #3 segment, and repeat steps 3 to 9 to obtain the average vibration spectrum A3 of the #3 segment, as shown in Figure 3 As shown, the resonance peak f3 of the #3 segment is 3.45kHz, and the resonance frequency offset Δf3 = -3.15kHz, which is beyond the range that can be represented by Table 1. It can be considered that the grouting layer structure of the #3 segment is abnormal and its thickness cannot be determined.

[0078] At this point, the inspection of the grouting structures of the three shield segments has been completed.

[0079] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0080] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A non-contact detection system for the thickness of the segment grouting layer based on structural vibration spectrum, characterized in that: The invention comprises a speaker (1), a laser interferometer optical head (2), a power amplifier (4), a signal generator (5), a laser interferometer control box (6), a power supply (7) and a laptop computer (8) integrated with excitation control software. The speaker (1) is connected to the power amplifier (4), the laser interferometer optical head (2) is connected to the laser interferometer control box (6), the power amplifier (4) is connected to the signal generator (5), the signal generator (5) and the laser interferometer control box (6) are all connected to the laptop computer (8), the signal generator (5), the power amplifier (4) and the laser interferometer control box (6) are all connected to the power supply (7), the signal generator (5) generates a sweep frequency excitation signal, the sweep frequency excitation signal is played out by the speaker (1) through the power amplifier (4), and acts on the shield segment and its grouting layer, causing vibration, and then synchronously collected by the laser interferometer optical head (2) and the laser interferometer control box (6) and input into the excitation control software in the laptop computer (8) for real-time processing, thereby realizing non-contact detection of the thickness of the segment grouting layer.

2. The non-contact detection system for the thickness of the segment grouting layer based on the structural vibration spectrum according to claim 1 is characterized in that: The detection system is installed on a mobile rail vehicle.

3. The non-contact detection system for the thickness of the segment grouting layer based on the structural vibration spectrum according to claim 1 is characterized in that: The signal generator (5) is connected to the power amplifier (4) via a TRS cable.

4. The non-contact detection system for the thickness of the segment grouting layer based on the structural vibration spectrum according to claim 1 is characterized in that: It also includes a tripod (3), and the tripod (3) is used to support the laser interferometer optical head (2).

5. A detection method for a non-contact detection system of segment grouting layer thickness based on structural vibration spectrum according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Determine n shield segments to be inspected and m inspection points on each shield segment to be inspected; 2) adjusting the speaker (1) and the laser interferometer optical head (2) to align with the detection point on the shield segment to be detected; 3) The sweep frequency range and frequency detection points of the sweep frequency excitation signal are set on the excitation control software in the laptop computer (8), and the signal generator (5) generates a sweep frequency excitation signal, which is input into the power amplifier (4), and then the speaker (1) emits a sweep frequency acoustic vibration signal, which acts on the shield segment to be detected and its grouting layer, thereby inducing vibration; 4) The laser interferometer optical head (2) and the laser interferometer control box (6) synchronously collect the sweep frequency acoustic vibration signal acting on the shield segment to be inspected and its grouting layer, and input the signal into the excitation control software in the laptop computer (8) for real-time processing to obtain the vibration spectrum at the inspection point; 5) Repeat steps 2)-4) m-1 times to complete the inspection of m inspection points on the shield segment to be inspected; 6) averaging the vibration spectra of the m detection points to obtain an average vibration spectrum, which is used as the vibration spectrum of the grouting layer of the shield segment to be detected; 7) Analyzing and calculating based on the average vibration spectrum to obtain the thickness of the grouting layer of the shield segment to be tested; 8) Repeat steps 2)-7) n-1 times to complete the inspection of the grouting layer thickness of all shield segments to be inspected.

6. The detection method according to claim 5, characterized in that The following steps are also included between step 2) and step 3): Turning on the laser interferometer optical head (2) and the laser interferometer control box (6) to locate the tracer light spot at the detection point, and adjusting the focal length and inclination angle of the laser interferometer optical head (2) to adjust the reflection intensity; The speaker (1), the power amplifier (4) and the signal generator (5) are turned on, and the intensity of the sweep frequency excitation signal is adjusted.

7. The detection method according to claim 5, characterized in that The vibration spectrum at the detection point is obtained by processing the excitation control software using a time-frequency conversion algorithm.

8. The detection method according to claim 5, characterized in that The vibration spectrum of the shield segment grouting layer to be tested is expressed as: Where A i is the vibration spectrum of the grouting structure of the i-th shield segment, m is the number of points to be measured on the shield segment, A ij is the vibration spectrum of the jth measured point on the i-th shield segment grouting structure.

9. The detection method according to claim 5, characterized in that In step 7), the step of obtaining the thickness of the grouting layer of the shield segment to be tested includes: Analyze the average vibration spectrum to obtain the resonance frequency of the grouting layer of the shield segment to be tested; Calculating the offset of the resonance frequency of the grouting layer of the shield segment to be tested relative to the resonance frequency of the individual shield segment; Based on the corresponding relationship between the offset and the thickness of the grouting layer, the thickness of the grouting layer of the shield segment to be inspected is obtained.

10. The detection method according to claim 9, characterized in that: The calculation expression of the offset is: Δf i =f i -f0 Where Δf i is the shield segment resonance frequency f i The shift relative to the resonant frequency f0 of the individual segment structure.

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