A tunnel detection system based on air-coupled impact echo

Abstract

This invention discloses a tunnel inspection system based on air-coupled impact echo, belonging to the field of tunnel non-destructive testing technology. It includes a mobile carrier, a modular frame, an excitation mechanism, and a control unit. The modular frame includes a vertical support cantilever and a horizontal support cantilever, with the excitation mechanism correspondingly located at the distal end of the vertical and / or horizontal support cantilever. The excitation mechanism includes a mounting base, a lifting drive, a telescopic drive, a mounting seat, an impact rod, and an acoustic sensor. The mounting base is located at the driving end of the lifting drive, and the telescopic drive is located at the other end of the mounting base, with a mounting seat at the front end of the telescopic drive. The impact rod and acoustic sensor are respectively mounted on the mounting seat. The control unit is communicatively connected to the mobile carrier and the excitation mechanism, controlling the lifting, telescopic, and impact actions of the excitation mechanism, and collecting the echo signals from the acoustic sensor. This system improves inspection efficiency, accuracy, and reliability.

Description

Technical Field

[0001] This invention belongs to the field of tunnel non-destructive testing technology, specifically relating to a tunnel testing system based on air-coupled impact echo, which is suitable for structural quality testing in confined spaces such as tunnel lining. Background Technology

[0002] Impact echo method is a widely used non-destructive testing technique for concrete structures. Its basic principle is to generate stress waves by applying mechanical impact to the structural surface. The reflected echo signals generated when these stress waves encounter defects or boundaries during propagation within the structure are then analyzed to determine the structure's thickness and internal defect conditions. Traditional impact echo testing requires direct contact between the sensor and the structural surface, and often necessitates the use of a coupling agent to ensure signal transmission quality. This method suffers from low efficiency, limited coverage, and difficulty in meeting the demands of large-area, rapid testing.

[0003] In recent years, air-coupled impact echo technology has developed rapidly as an emerging non-destructive testing method. This technology uses air as the coupling medium and receives the signal of stress wave leakage on the surface of the structure in a non-contact manner through air-coupled sensors, realizing completely non-contact internal defect detection. When stress wave propagates in the tunnel lining structure and encounters the structure-air interface, some of the energy will be radiated into the air in the form of leakage waves. These leakage waves carry key internal structural information, and the lining thickness and internal defect status can be determined by analyzing their frequency characteristics.

[0004] However, in practical engineering applications of air-coupled impact echo technology for shield tunnel on-site inspection, the research team encountered a series of interconnected and insurmountable problems, severely restricting the applicability and reliability of this method in tunnel environments. First, the limited inspection space is particularly prominent: in shield tunnels with a diameter of approximately 3.5 meters, conventional inspection vehicles cannot enter, forcing inspection work to be confined to the tunnel floor. Top inspection requires manual lifting devices, significantly reducing inspection efficiency and coverage. Second, mechanical interference and equipment safety issues are frequent: the ball-rotating impact mechanism used in the excitation source is prone to collisions with sensors and connecting cables during operation, causing inspection interruptions or even equipment damage. Third, road conditions significantly affect inspection accuracy: the densely distributed handhole structure within the tunnel causes the inspection trolley to vibrate and bounce during movement, making it difficult to maintain the 1-centimeter standard detection distance required for air-coupled inspection, directly affecting signal acquisition quality. Fourth, insufficient adaptability of the mechanism: the lack of vertical displacement redundancy design for the sensors makes the inspection trolley prone to getting stuck when traversing uneven road sections, further limiting the equipment's mobility. Finally, the system's stability defects were fully exposed in the lateral inspection: the inspection vehicle is prone to significant vibration during the side wall inspection, which causes fluctuations in the relative position of the sensor and the surface of the tube segment, failing to meet the stability requirements of high-precision non-destructive testing.

[0005] There is currently no effective solution to the aforementioned technical problems. Summary of the Invention

[0006] Technical problem to be solved: In view of the technical problems existing in the prior art, the present invention provides a tunnel detection system based on air coupling impact echo, which improves detection efficiency, accuracy and reliability, so as to solve the technical problems of space limitation, mechanical interference, road surface disturbance, insufficient displacement redundancy and poor stability in complex environments such as narrow tunnels.

[0007] Technical solution: The tunnel detection system based on air-coupled impact echo of the present invention includes: Mobile carrier; A modular frame is fixedly mounted on a mobile carrier; the modular frame includes a support frame, multiple vertical support cantilever arms evenly spaced along the width direction of the top of the support frame, and horizontal support cantilever arms horizontally arranged along both ends of the support frame; the vertical and horizontal support cantilever arms are adaptive suspension structures. An excitation mechanism is provided at the far end of the vertical support cantilever and / or the horizontal support cantilever. The excitation mechanism includes a mounting base, a lifting drive component, a telescopic drive component, a mounting seat, an impact rod, and an acoustic sensor. One end of the mounting base is provided at the driving end of the lifting drive component, and the telescopic drive component is horizontally provided at the other end of the mounting base. The front end of the telescopic link of the telescopic drive component is provided with a mounting seat. The impact rod and the acoustic sensor are provided with the mounting seat. The control unit is mounted on the mobile carrier and is communicatively connected to both the mobile carrier and the excitation mechanism. The control unit is used to control the lifting, extending, and impact actions of the excitation mechanism and to collect echo signals from the acoustic sensor.

[0008] Preferably, the lengths of the multiple vertical support cantilever arms gradually decrease from the center to both sides along the movable carrier and are adapted to the shape of the tunnel inner wall dome.

[0009] Preferably, both the vertical support cantilever and the horizontal support cantilever are telescopic structures to adapt to the detection needs at different heights and widths of the tunnel.

[0010] Preferably, the lateral support cantilever includes a square tube guide rail and a telescopic arm that is telescopically disposed within the square tube guide rail.

[0011] Preferably, the lateral support cantilever further includes a limiting guide groove and a positioning hole. The limiting guide groove is arranged along the length direction of the telescopic arm, and the positioning hole is arranged at intervals along the length direction of the square tube guide rail. A limiting screw that cooperates with the limiting guide groove is connected in the positioning hole. Tightening or loosening the limiting screw realizes the positioning and locking of the extension length of the telescopic arm in the square tube guide rail.

[0012] Preferably, the lateral support cantilever further includes a limiting plate, a stop screw, and a support spring. The limiting plate is slidably connected to the square tube guide rail by the limiting screw. The stop screw moves through the limiting plate and is fixedly connected to the end of the telescopic arm. The support spring is fitted on the stop screw and abuts against the limiting plate and the end of the telescopic arm.

[0013] Preferably, the lifting drive component is fixedly connected to the front end of the telescopic arm and is connected to one end of the mounting base plate for transmission. The lifting drive component drives the mounting base plate and its structure to achieve vertical height adjustment. The telescopic drive component is horizontally positioned at the far end of the mounting base and is connected to the telescopic linkage via a transmission mechanism. The telescopic drive component drives the telescopic linkage to reciprocate the impact rod against the inner wall of the tunnel. The acoustic sensor simultaneously collects air-coupled echo signals.

[0014] Preferably, the impact rod and the telescopic connecting rod are arranged coaxially, and the acoustic sensor is located on the side of the impact rod.

[0015] Preferably, the mobile carrier is further provided with a counterweight, which is arranged on the side of the mobile carrier away from the direction of extension of the excitation mechanism.

[0016] Preferably, the control unit controls the movement trajectory of the mobile carrier, the lifting stroke of the lifting drive component, the extension stroke of the telescopic drive component, and the striking action of the impact rod.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The present invention achieves flexible adjustment of the excitation mechanism in the vertical and horizontal directions through the design of the vertical support cantilever and the horizontal support cantilever of the modular frame, which can adapt to the needs of different tunnel diameters and detection positions. In particular, it can meet the detection requirements of the top and side walls of small-diameter tunnels of 3.5 meters, significantly expand the detection coverage, and solve the problem of accessibility of detection in narrow spaces. (2) The present invention adopts an impact rod driven by a telescopic linkage and an acoustic sensor integrated on the same mounting base. The excitation and reception move synchronously, which fundamentally avoids the problem of collision between the excitation source and the sensor and cable in the rotational striking method, and improves the operational safety and reliability of the system. (3) The present invention sets a support spring in the horizontal support cantilever / vertical support cantilever. Through the elastic support of the support spring, the excitation mechanism can adaptively conform to the undulation of the detection surface during the detection process, effectively absorb the vibration caused by the hand hole structure at the bottom of the tunnel, thereby maintaining a stable detection distance (about 1 cm air coupling distance) and ensuring the quality of signal acquisition. (4) By setting counterweights on a mobile carrier and optimizing the position of the counterweights, the present invention improves the overall stability of the detection system under the side wall detection condition, effectively suppresses the vibration of the carrier during the detection process, ensures the relative position of the sensor and the surface of the tube segment is stable, and meets the stability requirements of high-precision non-destructive testing. (5) The present invention has a compact overall structure and a high degree of modularity. The mobile carrier can flexibly travel through small-diameter tunnels, which greatly reduces the labor intensity of manual lifting operations and significantly improves the detection efficiency.

[0018] The above improvements work together to enable the air-coupled impact echo detection system of the present invention to be applied stably, efficiently and reliably in complex and confined environments such as shield tunnels. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the detection system based on air-coupled impact echo according to an embodiment of the present invention when it is used for detection in a tunnel. Figure 2 for Figure 1 A schematic diagram of the front view structure of the detection system; Figure 3 for Figure 2 Schematic diagram of the connection structure between the central excitation mechanism and the vertical / horizontal support cantilever; Figure 4 for Figure 3 Cross-sectional view of the transverse support cantilever along its length; Figure 5 for Figure 3 A partial structural diagram of the central excitation mechanism.

[0020] Reference numerals: 100, Detection system; 200, Tunnel inner wall; 1, Mobile carrier; 2, Modular frame; 21, Support frame; 22, Vertical support cantilever; 23, Horizontal support cantilever; 231, Square tube guide rail; 232, Telescopic arm; 233, Limiting guide groove; 234, Positioning hole; 235, Limiting plate; 236, Plug screw; 237, Support spring; 3, Excitation mechanism; 31, Mounting base; 32, Lifting drive component; 33, Telescopic drive component; 34, Telescopic connecting rod; 35, Mounting seat; 36, Impact rod; 37, Acoustic sensor; 4, Control unit; 5, Counterweight. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings. Figures 1-5 The technical solutions of the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0022] like Figures 1-5 As shown, the present invention discloses a tunnel inspection system based on air-coupled impact echo. The inspection system 100 is particularly suitable for non-destructive testing of the tunnel inner wall 200. The system includes a mobile carrier 1, a modular frame 2, an excitation mechanism 3, and a control unit 4.

[0023] (a) Mobile carrier: The mobile carrier 1 carries the entire inspection system 100, enabling it to move freely inside the tunnel. Considering that the diameter of a shield tunnel is typically only about 3.5 meters, conventional inspection vehicles cannot enter. Therefore, the mobile carrier 1 of this invention is preferably a miniaturized self-propelled chassis with an aluminum alloy frame. Its size design allows it to flexibly traverse the bottom area of ​​the tunnel. The mobile carrier 1 can adopt a wheeled or tracked walking mechanism, preferably a tracked walking mechanism to obtain better passability and stability, and to adapt to uneven road surface conditions such as handhole structures that may exist inside the tunnel.

[0024] In a preferred embodiment, a counterweight 5 is also provided on the mobile carrier 1. The counterweight 5 is arranged on the side of the mobile carrier 1 away from the extension direction of the excitation mechanism 3; that is, when the excitation mechanism 3 extends outward from one side of the mobile carrier 1 to perform tunnel sidewall detection, the counterweight 5 is arranged on the opposite side to provide balance, thereby effectively suppressing the vibration of the mobile carrier 1 during the detection process, ensuring the relative position stability between the acoustic sensor and the tunnel segment surface, and meeting the stability requirements of high-precision non-destructive testing. The counterweight 5 can be a detachable modular counterweight block, so that the weight can be flexibly adjusted according to different detection positions and detection heights.

[0025] (II) Modular Framework: The modular frame 2 is fixedly mounted on the mobile carrier 1) to support and install the excitation mechanism 3. The modular frame 2 adopts a combined structure, including a support frame 21, multiple vertical support cantilever arms 22 evenly spaced along the width direction of the top of the support frame 21, and horizontal support cantilever arms 23 horizontally arranged along both ends of the support frame 21. The support frame 21 is the basic structure of the modular frame 2 and is firmly fixed to the platform surface of the mobile carrier 1. The support frame 21 is preferably a frame structure made of welded or bolted steel sections, which has sufficient structural strength and rigidity.

[0026] In a preferred embodiment, the lengths of multiple vertical support cantilever arms 22 are gradually shortened from the center to both sides along the movable carrier 1 and are adapted to the shape of the tunnel inner wall 200 dome, thereby meeting the detection requirements of different positions of the tunnel inner wall dome.

[0027] Both the vertical support cantilever 22 and the horizontal support cantilever 23 can adopt a telescopic structure to adapt to the detection needs of different heights and widths in the tunnel. The vertical support cantilever 22 and the horizontal support cantilever 23 can adjust the vertical height or horizontal position of the excitation mechanism 3 (approximately 1 cm of air coupling distance) according to the height and position of the detection target. Both the vertical support cantilever 22 and the horizontal support cantilever 23 can employ a screw lifting mechanism, a hydraulic lifting mechanism, or a pneumatic lifting mechanism, with an electric screw lifting mechanism being preferred to achieve precise and stable height adjustment. It should be noted that, as... Figure 2 As shown, only the excitation mechanism 3 is provided at the far end of one of the transverse support cantilever 23. In actual testing, each vertical support cantilever 22 and transverse support cantilever 23 can be equipped with an excitation mechanism 3 at its far end to meet the requirements of testing at different side wall positions on one working face of the tunnel inner wall 200, thereby reducing the difficulty of operation and improving the efficiency of testing.

[0028] like Figures 3-4 As shown, the vertical support cantilever 22 and the horizontal support cantilever 23 can adopt the same main structure, both including a square tube guide rail 231 and a telescopic arm 232 that is telescopically installed inside the square tube guide rail 231; one end of the square tube guide rail 231 is fixedly connected to the support frame 21, and the telescopic arm 232 can slide and extend along the length direction inside the square tube guide rail 231, thereby adjusting the horizontal or vertical extension distance of the excitation mechanism 3 to adapt to the needs of different tunnel diameters and different detection positions (bottom detection, side wall detection, or top detection). It should be noted that if the telescopic drive structure adopts an electric screw lifting mechanism, it can be correspondingly installed inside the square tube guide rail 231, and its drive end can be correspondingly connected to the end of the telescopic arm 232 to realize automatic telescopic drive adjustment (the telescopic drive structure is not shown in the figure).

[0029] Furthermore, to achieve precise positioning and locking of the extension length of the telescopic arm 232, the vertical support cantilever 22 and the horizontal support cantilever 23 are also equipped with limiting mechanisms. Specifically, a limiting guide groove 233 is formed along the length direction on the opposite side wall of the telescopic arm 232, and multiple positioning holes 234 are spaced along the length direction on the side wall of the square tube guide rail 231. Limiting screws that cooperate with the limiting guide groove 233 are connected inside the positioning holes 234. When the telescopic arm 232 extends to the required length, the limiting screw passes through the corresponding positioning hole 234 and is pressed into the limiting guide groove 233, thus locking the telescopic arm 232 at the current extension position. The spacing of the positioning holes 234 provides multiple predetermined extension positions, facilitating rapid positioning according to the detection scenario. This structure does not conflict with the automatic telescopic structure and can be freely combined according to requirements. For example, after the telescopic arm 232 is driven to the extended position by an electric screw lifting mechanism, the position of the telescopic arm 232 can be locked using limiting screws.

[0030] Furthermore, in order to achieve vibration damping of the excitation mechanism 3, especially the excitation mechanism 3 connected to the top of the vertical support cantilever 22, when the mobile carrier 1 moves and bumps, the vertical support cantilever 22 and the horizontal support cantilever 23 can adopt an adaptive suspension structure. Specifically, the horizontal support cantilever 23 also includes a limiting plate 235, a locking screw 236, and a support spring 237. The limiting plate 235 is slidably connected to the square tube guide rail 231 by the limiting screw. The locking screw 236 moves through the limiting plate 235 and is fixedly connected to the end of the telescopic arm 232. The support spring 237 is fitted on the locking screw 236 and abuts against the limiting plate 235 and the end of the telescopic arm 232. In this embodiment, the limiting plate 235, the locking screw 236, the support spring 237, and the telescopic arm 232 are connected as an integral structure. The position of the entire structure within the square tube guide rail 231 can be adjusted by changing the position of the limiting plate 235 within the square tube guide rail 231. The adjustment method is to lock or unlock the limiting plate 235 within the square tube guide rail 231 by loosening or tightening the limiting screw. Similarly, the automatic telescopic structure's drive end is connected to the limiting plate 235 to achieve automatic adjustment of the position of the limiting plate 235 within the square tube guide rail 231. The specific connection method is not described in detail here.

[0031] When the excitation mechanism 3 performs the detection operation, the support spring 237 is in a pre-compressed state, applying an outward elastic thrust to the telescopic arm 232. This design allows the excitation mechanism 3 to adaptively conform to the undulations of the detection surface under the elastic support of the support spring 237 when the mobile carrier 1 encounters uneven road surfaces such as handhole structures during its movement, thus effectively absorbing vibration and maintaining a standard detection distance of approximately 1 cm between the impact rod 36 and the detection surface, ensuring signal acquisition quality. This elastic compensation mechanism is one of the key innovations of this invention, significantly improving the problem in the prior art where fluctuations in detection distance due to road surface bumps affect detection accuracy.

[0032] (III) Incentive Institutions: The excitation mechanism 3 is mounted on the modular frame 2, specifically at the far end of the vertical support cantilever 22 and / or the lateral support cantilever 23. Figure 2 Only the embodiment shown is located at the far end of the transverse support cantilever, used to apply mechanical impact to the tunnel inner wall 200 and receive echo signals.

[0033] like Figure 2 , Figure 3 and Figure 5 As shown, the excitation mechanism 3 includes a mounting base 31, a lifting drive component 32, a telescopic drive component 33, a mounting base 35, an impact rod 36, and an acoustic sensor 37. The lifting drive component 32 is fixedly connected to the front end of the telescopic arm 232. The output end of the lifting drive component 32 is connected to one end of the mounting base 31 for transmission. The lifting drive component 32 drives the mounting base 31 and its structure to achieve vertical height adjustment relative to the modular frame 2. The lifting drive component 32 can be any one of a linear motor, a lead screw motor, a cylinder, or a hydraulic cylinder. It is preferred to use a lead screw mechanism driven by a servo linear motor or a stepper motor to achieve precise lifting displacement control.

[0034] One end of the mounting base plate 31 is correspondingly positioned at the drive end of the lifting drive component. The mounting base plate 31 serves as the mounting foundation for the telescopic drive component 33 and the telescopic connecting rod 34. The telescopic drive component 33 is horizontally positioned at the other end of the mounting base plate 31, and the output end of the telescopic drive component 33 is connected to the telescopic connecting rod 34 for transmission. The telescopic drive component 33 can be a cylinder, a hydraulic cylinder, or a linear motor, with a cylinder drive being preferred to obtain rapid response and stable output force.

[0035] The telescopic link 34 is connected to the telescopic drive component 33. The mounting base 35 is correspondingly provided at the front end of the telescopic link 34 (i.e. the end of the telescopic link 34 away from the telescopic drive component 33). The mounting base 35 is used to simultaneously support the impact rod 36 and the acoustic sensor 37, thereby integrating the excitation and reception functions into one.

[0036] Impact rod 36 and acoustic sensor 37 are respectively mounted on mounting base 35. Impact rod 36 is used to impact the surface of tunnel inner wall 200 under the drive of telescopic link 34 to generate stress wave. Impact rod 36 is preferably arranged coaxially with telescopic link 34 to ensure the consistency of the impact force direction and ensure that the stress wave is incident perpendicularly on the detection surface.

[0037] An acoustic wave sensor 37 is also correspondingly mounted on the mounting base 35; specifically, the acoustic wave sensor 37 is positioned beside the impact rod 36. The acoustic wave sensor 37 is an air-coupled sensor, which can receive signals of stress wave leakage on the structural surface without contact with the detection surface. The impact rod 36 and the acoustic wave sensor 37 are integrated on the same mounting base 35, and their relative positions are fixed, thus ensuring that the sensor is in the optimal receiving position after each impact, overcoming the problem of collision between the excitation source and the sensor caused by space limitations and structural design defects in the prior art.

[0038] (iv) Control Unit: The control unit is mounted on the mobile carrier 1 and is communicatively connected to both the mobile carrier 1 and the excitation mechanism 3. The control unit 4 can be an independent controller or integrated into a host computer or embedded control system. Its core functions include: controlling the movement trajectory and speed of the mobile carrier 1; controlling the lifting stroke of the lifting drive component 32 to adjust the vertical height of the excitation mechanism 3; controlling the extension stroke and impact frequency of the telescopic drive component 33 to achieve automated impact excitation; controlling the signal acquisition and data transmission of the acoustic sensor 37; and processing and analyzing the acquired impact echo signals to determine the thickness of the tunnel inner wall 200 and the condition of internal defects. The control unit 4 can automatically complete omnidirectional scanning detection of the tunnel bottom, side walls, and top according to preset detection paths and parameters, significantly improving detection efficiency and automation.

[0039] The working principle or process of the system of the present invention will be explained below in conjunction with specific testing scenarios.

[0040] During tunnel inner wall inspection, the mobile carrier 1 moves along the bottom of the tunnel. The control unit 4 controls the vertical support cantilever 22 to lower the excitation mechanism 3 to a suitable height and controls the telescopic arm 232 of the lateral support cantilever 23 to extend to an appropriate length, positioning the excitation mechanism 3 at a suitable distance from the working surface to be inspected. During tunnel side wall inspection, the mobile carrier 1 moves along the bottom of the tunnel, and the telescopic arm 232 of the lateral support cantilever 23 extends laterally, moving the excitation mechanism 3 laterally to a suitable position on the side wall working surface. The counterweight 5 is positioned on the other side of the mobile carrier 1 to provide a balancing torque and suppress tilting and vibration caused by the shift in the center of gravity of the carrier. Subsequently, the control unit 4 controls the telescopic drive 33 to extend the telescopic connecting rod 34, causing the impact rod 36 to strike the surface of the test point on the tunnel inner wall 200, generating stress waves. The acoustic sensor 37 receives the stress wave signal leaking into the air and transmits the signal to the control unit 4 for analysis and processing. During the inspection process, the control unit 4 can also control the lifting drive 32 to adjust the height of the excitation mechanism 3, sequentially completing the inspection at different heights of the side wall.

[0041] During tunnel top inspection, the mobile carrier 1 travels along the tunnel floor, and the vertical support cantilever 22 lifts the excitation mechanism 3 to its maximum height. The telescopic arm 232 of the horizontal support cantilever 23 extends obliquely upward, bringing the excitation mechanism 3 close to the area to be inspected at the tunnel top; the specific inspection process is the same as above. Because this invention employs a modular telescopic arm structure and lifting mechanism, even in small-diameter tunnels, the top area can be inspected without manual lifting, significantly improving inspection efficiency and coverage. During the inspection process, the support spring 237 continuously applies elastic thrust, maintaining a relatively constant distance between the excitation mechanism 3 and the inspection surface, effectively suppressing fluctuations in detection distance caused by road surface bumps.

[0042] The tunnel detection system based on air-coupled impact echo provided by this invention systematically solves the problems of space constraints, mechanical interference, vibration effects, insufficient adaptability, and poor stability faced by existing air-coupled impact echo technology in shield tunnel field detection through the adjustable cantilever design of the modular frame, the integrated structure of excitation and reception, the adaptive compensation mechanism of elastic support, and the counterweight balance structure. It has outstanding advantages such as wide detection coverage, high operational reliability, good signal acquisition quality, strong equipment passability, and excellent overall stability, and has good prospects for promotion and application.

[0043] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A tunnel detection system based on air-coupled impact echo, characterized in that, include: Mobile carrier (1); A modular frame (2) is fixedly mounted on a mobile carrier (1); the modular frame (2) includes a support frame (21), multiple vertical support cantilever arms (22) evenly spaced along the width direction of the top of the support frame (21), and horizontal support cantilever arms (23) horizontally arranged along both ends of the support frame (21); the vertical support cantilever arms (22) and the horizontal support cantilever arms (23) are adaptive suspension structures; The excitation mechanism (3) is correspondingly disposed at the far end of the vertical support cantilever (22) and / or the horizontal support cantilever (23); the excitation mechanism (3) includes a mounting base (31), a lifting drive (32), a telescopic drive (33), a mounting seat (35), an impact rod (36), and an acoustic sensor (37). One end of the mounting base (31) is correspondingly disposed at the driving end of the lifting drive, and the telescopic drive (33) is correspondingly horizontally disposed at the other end of the mounting base (31). The front end of the telescopic connecting rod (34) of the telescopic drive (33) is correspondingly disposed at the mounting seat (35). The impact rod (36) and the acoustic sensor (37) are correspondingly disposed on the mounting seat (35). Control unit (4) is installed on the mobile carrier (1) and is communicatively connected to the mobile carrier (1) and the excitation mechanism (3) respectively; the control unit is used to control the lifting, stretching and impact actions of the excitation mechanism (3) and to collect the echo signal of the acoustic sensor.

2. The tunnel detection system based on air-coupled impact echo as described in claim 1, characterized in that, The length of the multiple vertical support cantilever (22) is gradually shortened from the center to both sides of the movable carrier (1) and is adapted to the dome shape of the tunnel inner wall (200).

3. The tunnel detection system based on air-coupled impact echo as described in claim 1, characterized in that, Both the vertical support cantilever (22) and the horizontal support cantilever (23) are telescopic structures to adapt to the detection needs of different heights and widths of the tunnel.

4. The tunnel detection system based on air-coupled impact echo according to claim 3, characterized in that, The lateral support cantilever (23) includes a square tube guide rail (231) and a telescopic arm (232) that is telescopically disposed within the square tube guide rail (231).

5. The tunnel detection system based on air-coupled impact echo according to claim 4, characterized in that, The transverse support cantilever (23) also includes a limiting guide groove (233) and a positioning hole (234). The limiting guide groove (233) is arranged along the length direction of the telescopic arm (232), and the positioning hole (234) is arranged at intervals along the length direction of the square tube guide rail (231). A limiting screw that cooperates with the limiting guide groove (233) is connected in the positioning hole (234). Tightening or loosening the limiting screw realizes the positioning and locking of the extension length of the telescopic arm (232) in the square tube guide rail (231).

6. The tunnel detection system based on air-coupled impact echo according to claim 5, characterized in that, The transverse support cantilever (23) also includes a limiting plate (235), a stop screw (236), and a support spring (237). The limiting plate (235) is slidably connected to the square tube guide rail (231) by the limiting screw. The stop screw (236) moves through the limiting plate (235) and is fixedly connected to the end of the telescopic arm (232). The support spring (237) is fitted on the stop screw (236) and abuts against the end of the limiting plate (235) and the end of the telescopic arm (232).

7. The tunnel detection system based on air-coupled impact echo as described in claim 6, characterized in that, The lifting drive component (32) is fixedly connected to the front end of the telescopic arm (232) and is connected to one end of the mounting base plate (31) for transmission. The lifting drive component (32) drives the mounting base plate (31) and its structure to achieve vertical height adjustment. The telescopic drive component (33) is horizontally positioned at the far end of the mounting base plate (31) and is connected to the telescopic connecting rod (34) for transmission. The telescopic drive component (33) drives the telescopic connecting rod (34) to reciprocate the impact rod to impact the inner wall (200) of the tunnel. The acoustic sensor (37) synchronously collects the air coupling echo signal.

8. The tunnel detection system based on air-coupled impact echo according to claim 7, characterized in that, The impact rod (36) is arranged coaxially with the telescopic connecting rod (34), and the acoustic sensor (37) is located on the side of the impact rod (36).

9. The tunnel detection system based on air-coupled impact echo according to claim 1, characterized in that, The mobile carrier (1) is also provided with a counterweight (5), which is arranged on the side of the mobile carrier (1) away from the direction of extension of the excitation mechanism (3).

10. The tunnel detection system based on air-coupled impact echo according to claim 1, characterized in that, The control unit (4) controls the movement trajectory of the mobile carrier (1), the lifting stroke of the lifting drive (32), the extension stroke of the telescopic drive (33), and the striking action of the impact rod (36).

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