A flexible crack sensor for tunnel lining

Abstract

This application discloses a flexible crack sensor for tunnel secondary lining, relating to the field of tunnel structure protection. It includes a sensing unit and a processing module. The sensing unit is in contact with the tunnel wall, and the processing module is electrically connected to the sensing unit. The sensing unit detects deformation of the tunnel wall, and the processing module receives signals transmitted by the sensing unit and issues an alarm. This application monitors the deformation of the tunnel secondary lining surface. When deformation is detected in the tunnel wall, it indicates that cracks will occur or have already occurred in that area, prompting an alarm to be issued. This allows relevant personnel to take appropriate measures to address the issue, achieving early prevention and control of cracks in the tunnel secondary lining.

Description

Technical Field

[0001] This application relates to the technical field of tunnel structure protection, and more specifically, to a flexible crack sensor for tunnel secondary lining. Background Technology

[0002] Secondary lining is a secondary support technique used in tunnel construction to reinforce the tunnel structure, and its construction quality directly affects the tunnel's safety and stability. This technique typically consists of reinforced concrete or plain concrete and includes steps such as formwork erection, rebar installation, and concrete pouring. Its main functions include enhancing overall stability, preventing deformation and damage, and ensuring traffic safety.

[0003] If cracks appear in the secondary lining structure of a tunnel, it may indicate serious safety hazards such as abnormal stress, leakage, water damage, and foundation settlement. Once the cracks connect, groundwater and corrosive media can more easily penetrate into the interior of the structure, causing steel corrosion, concrete spalling, and secondary damage.

[0004] The development trend of cracks is directly related to the durability and long-term safety of tunnels. Therefore, how to monitor early cracks, leakage or structural anomalies in the secondary lining of tunnels is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a flexible crack sensor for tunnel secondary lining, which can effectively respond to and generate an alarm signal when cracks occur in the tunnel inner wall, so as to remind timely and necessary protective measures to be taken.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] A flexible crack sensor for tunnel secondary lining includes a sensing unit and a processing module. The sensing unit is in contact with the tunnel wall, and the processing module is electrically connected to the sensing unit. The sensing unit is used to detect the deformation of the tunnel wall, and the processing module is used to receive the signal transmitted by the sensing unit and issue an alarm.

[0008] Preferably, the sensing unit includes a sensing layer, which is a flexible strain sensor with a wire mesh structure, and also includes a power supply battery and two electrode blocks. The power supply battery and the electrode blocks are connected, and the electrode blocks are in contact with the sensing layer.

[0009] Preferably, the sensing unit includes a central portion and a plurality of radiating extension portions, one end of each radiating extension portion being integrally formed with the central portion, and the plurality of radiating extension portions being distributed around the central portion.

[0010] Preferably, the electrode block includes an inner ring electrode and an outer ring electrode, the inner ring electrode is in contact with the center portion, and the outer ring electrode is in contact with the end of the radiating extension portion away from the center portion.

[0011] Preferably, the inner electrode has a mounting slot for the processing module to be placed in. The processing module includes a signal converter and an alarm light. The signal converter is electrically connected to the sensing layer, and the alarm light is electrically connected to the signal converter.

[0012] Preferably, it also includes a protective cover, which is located on the side of the electrode block away from the sensing unit, and the protective cover seals the gap between the inner and outer electrodes.

[0013] Preferably, the sensing unit further includes a strain transmission layer, which is in contact with and fixedly connected to the sensing layer, and the strain transmission layer is made of a tensile material.

[0014] Preferably, the strain transfer layer contains a piezoelectric material, which is used to supply power to the power supply battery.

[0015] Preferably, the sensing unit further includes an adhesive layer, which is fixedly connected to the sensing layer, and the side of the adhesive layer opposite to the sensing layer is adhered to the inner wall of the tunnel.

[0016] Preferably, the sensing unit further includes a protective layer, and the protective layer and the sensing layer are fixedly connected.

[0017] The flexible crack sensor for tunnel lining provided in this application is installed on the inner wall of the tunnel and the sensing unit is in contact with the inner wall of the tunnel. When the sensing unit detects deformation of the inner wall of the tunnel, it indicates that there is a risk of cracking or that crack defects have already occurred in the area it is in contact with. Then, it sends a signal to the processing module, which then issues an alarm. The operator can then deal with the defect in a timely manner based on the feedback information from the sensor and the specific situation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram illustrating the overall structure of a flexible crack sensor used for tunnel lining in an embodiment of this application;

[0020] Figure 2This is a cross-sectional schematic diagram illustrating the structure of a flexible crack sensor used for tunnel secondary lining in an embodiment of this application;

[0021] Figure 3 This is a schematic diagram illustrating the layer structure of the sensing unit in an embodiment of this application;

[0022] Figure 4 This is a schematic diagram illustrating the structure of the strain transfer layer in the embodiments of this application.

[0023] Figures 1-4 In the accompanying drawings, the reference numerals include:

[0024] 1. Sensing unit; 11. Central part; 12. Radiation extension part; 2. Inner ring electrode; 21. Mounting slot; 22. Outer ring electrode; 3. Processing module; 31. Signal converter; 301. Microprocessor; 32. Alarm light; 33. Wireless transmission module; 34. Power supply battery; 4. Protective cover; 5. Sensing layer; 6. Strain transmission layer; 61. Piezoelectric material; 7. Adhesive layer; 8. Protective layer. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar words used in this application do not indicate any order, quantity, or importance. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes. An embodiment of this application discloses a flexible crack sensor for tunnel secondary lining.

[0027] The core of this application is to provide a flexible crack sensor for tunnel secondary lining.

[0028] Please refer to Figure 1 and Figure 2 .

[0029] The flexible crack sensor for tunnel lining provided in this application includes a sensing unit 1 and a processing module 3. The sensing unit 1 and the processing module 3 are fixedly connected to each other, with the processing module 3 located on one side of the sensing unit 1 and electrically connected. During crack monitoring of the tunnel lining surface, the sensing unit 1 will directly contact the tunnel lining surface. When the sensing unit 1 detects deformation on the tunnel lining surface, it indicates that a signal has been generated or there is a clear tendency for cracks to form. The sensing unit 1 will then send an electrical signal to the processing module 3. Upon receiving the electrical signal, the processing module 3 will issue an alarm through optical or acoustic means, so that personnel can promptly obtain the cracking status of the measured area.

[0030] The aforementioned flexible crack sensor for tunnel lining effectively solves the problem of untimely detection of surface cracks and defects in tunnel lining, which can lead to safety hazards.

[0031] The flexible crack sensor for tunnel lining provided in this application will be described in more detail below with reference to the accompanying drawings and specific embodiments.

[0032] In one specific implementation, reference is made to... Figure 1 , Figure 2 and Figure 3 .

[0033] Specifically, it also includes a power supply battery 34 and two electrode blocks. The sensing unit 1 has a layered structure, which includes a sensing layer 5. During monitoring, the surface of the sensing unit 1 and the surface of the tunnel lining are in surface contact and relatively fixed. When the surface of the tunnel lining deforms, the deformation trend is transmitted to the sensing layer 5. The two electrode blocks are simultaneously in contact with the sensing layer 5 and fixed to each other. The electrode blocks are electrically connected to the power supply battery 34, and the power supply battery 34 supplies power to the sensing layer 5 through the electrode blocks. When the sensing layer 5 deforms, its own resistance changes. Therefore, when the processing module 3 senses a change in the resistance of the sensing layer 5, it means that the sensing layer 5 has deformed, that is, the surface of the tunnel lining in the area it detects has deformed.

[0034] The sensing layer 5 adopts a CB / GR / MWCNTs-Ecoflex flexible strain sensor with a wire mesh structure or a similar large deformation tensile structure. It features fast response speed, good recovery, good durability, high sensitivity and a large sensing range. It can achieve stable detection requirements in a wide temperature range of 0-60℃ and in complex underwater environments. Moreover, the raw materials for manufacturing the sensor are readily available, making the sensing layer 5 easy to industrialize.

[0035] Based on the above embodiments, refer to Figure 1 and Figure 2 .

[0036] Specifically, the sensing unit 1 has a planar radial shape, that is, the sensing unit 1 includes a central part 11 and multiple radial extensions 12. The central part 11 is circular, and the radial extensions 12 are elongated. One end of each radial extension 12 is integrally formed on the edge of the central part 11. The multiple radial extensions 12 are arranged in a ring array with the central part 11 as the center. The length direction of the radial extensions 12 is the radial direction of the central part 11. In this embodiment, the number of radial extensions 12 is four.

[0037] The radially shaped sensing unit 1 establishes a polar coordinate system centered on the central part 11. Within the coverage of this coordinate system, when a deformation occurs at a certain point on the surface of the tunnel lining, the sensing layer 5 also undergoes a specific deformation, thereby accurately sensing information such as the location, size, and direction of the deformation.

[0038] Based on the above embodiments, refer to Figure 1 and Figure 2 .

[0039] Specifically, the electrode block includes an inner ring electrode 2 and an outer ring electrode 22, both of which are annular and coaxially nested together without contacting each other. The inner ring electrode 2 is in contact with the center portion 11, and the outer ring electrode 22 is in contact with the end of the radiating extension portion 12 away from the center portion 11. The power supply battery 34 generates a potential difference between the two electrode blocks, causing a current to be generated on the sensing layer 5 for detection. In specific implementation, the gap between the inner ring electrode 2 and the outer ring electrode 22 can be filled with insulating material to improve the stability of their relative state.

[0040] Based on the above embodiments, such as Figure 1 and Figure 2 As shown.

[0041] Specifically, the inner electrode 2 has a mounting slot 21 for the processing module 3 to be inserted. The power supply battery 34 is installed inside the housing, which is also fixedly installed in the mounting slot 21. The processing module 3 includes a signal converter 31, an alarm light 32, and a wireless transmission module 33. The signal converter 31 includes a microprocessor 301 and a signal conversion module. The signal conversion module is electrically connected to the sensing layer 5. The electrical signals generated on the sensing layer 5 are analyzed and converted, and then the alarm light 32 and the wireless transmission module 33 are controlled. When deformation of the tunnel lining surface is detected, the alarm light 32 lights up, and at the same time, the wireless transmission module 33 sends a wireless signal for long-distance notification. This enables wireless mesh networking of multiple sensors and "relay"-style signal transmission, thereby avoiding the need to lay long-distance cables in the tunnel and greatly reducing the cost of equipment deployment.

[0042] Based on the above embodiments, such as Figure 1 As shown.

[0043] Specifically, it also includes a protective cover 4, which is located on the side of the electrode block away from the sensing unit 1. The protective cover 4 is disc-shaped and can be connected and fixed to the two electrode blocks by means of snap-fit ​​or adhesive, thereby reducing the negative impact of external environmental factors on the two electrode blocks and the processing module 3, and further improving the connection stability between the inner ring electrode 2 and the outer ring electrode 22.

[0044] A through hole is provided in the middle of the protective cover 4 so that the alarm light 32 of the processing module 3 can work normally.

[0045] Based on any of the above embodiments, such as Figure 3 As shown.

[0046] Specifically, the sensing unit 1 also includes a strain transfer layer 6, which is in close contact with and fixedly connected to the sensing layer 5. The strain transfer layer is located on the side of the sensing layer 5 facing the tunnel secondary lining surface. The strain transfer layer 6 is made of Auxetic tensile material, i.e., negative wave Sorrento ratio material.

[0047] When the sensor within sensing layer 5 is subjected to tension, the structure of strain transfer layer 6 deforms synchronously with the micro-deformation of the concrete surface (settlement, temperature difference, micro-cracks), preventing breakage or peeling due to excessive rigidity. The sensor within sensing layer 5 effectively maintains its physical dimensions, thus ensuring effective adhesion between the sensor and the concrete surface. Furthermore, the tensile material structure itself has the advantages of dispersing external forces and buffering external impacts. The addition of strain transfer layer 6 gives the sensor new functions of filtering vibration signals and uniformizing strain signals. Upon external impact, the structure expands laterally, dispersing the external force over a larger area and preventing sensor damage caused by human construction damage, mortar dripping, or object impacts.

[0048] Based on the above embodiments, such as Figure 3 and Figure 4 As shown.

[0049] Specifically, the strain transfer layer 6 contains a piezoelectric material 61, which can be a PVDF fiber membrane. The piezoelectric material 61 is electrically connected to the power supply battery 34. By collecting minute mechanical energy (such as minute vibration signals) from the surface of the tunnel lining, it converts this energy into electrical energy and stores it in the power supply battery 34, thus enabling the sensor to operate on its own power. This self-powered capability not only improves the system's independence and reliability but also reduces maintenance costs and wiring complexity, making it particularly suitable for long-term health monitoring in confined spaces such as tunnels.

[0050] Based on any of the above embodiments, such as Figure 3 As shown.

[0051] Specifically, the sensing unit 1 also includes an adhesive layer 7 and a protective layer 8. The adhesive layer 7 is fixedly connected to the sensing layer 5, and the adhesive layer 7 is adhered to the layer of the strain transfer layer 6 opposite to the sensing layer 5. The side of the adhesive layer 7 opposite to the sensing layer 5 is adhered to and bonded to the surface of the tunnel secondary lining. The adhesive layer 7 uses high-performance adhesives such as modified polyurethane, which ensures a firm bond between the sensing unit 1 and the surface of the tunnel secondary lining, guaranteeing that stress and vibration energy can be effectively transferred from the concrete to the strain transfer layer 6 and the sensing layer 5.

[0052] like Figures 1-3 As shown, the protective layer 8 and the sensing layer 5 are fixedly connected, and the protective layer 8 is attached to the side of the sensing layer 5 facing away from the tunnel lining surface. The protective layer 8 is made of Ecoflex flexible material with a thickness of 0.1mm, which protects the sensor for normal use in harsh environments and reduces the impact of dust and moisture in the tunnel on the sensing unit 1.

[0053] In practical implementation, the flexible crack sensor for the tunnel lining has an overall diameter of approximately 10 cm and an overall thickness of less than 1 cm. During use, operators attach the sensor to areas on the tunnel lining surface prone to stress concentration or frequent stress, as needed, for focused monitoring.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0055] The above provides a detailed description of a flexible crack sensor for tunnel secondary lining provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A flexible crack sensor for a tunnel secondary lining, characterized in that The tunnel wall deformation sensor comprises a sensing unit (1) and a processing module (3), the sensing unit (1) is in contact with the tunnel wall, the processing module (3) is electrically connected with the sensing unit (1), the sensing unit (1) is used for detecting the deformation of the tunnel wall, and the processing module (3) is used for receiving the signal transmitted by the sensing unit (1) and alarming. The sensing unit (1) is a layered structure, comprising a sensing layer (5), the sensing layer (5) is a flexible strain sensor adopting a wire mesh grid structure, and further comprising a power supply battery (34) and two electrode blocks, the power supply battery (34) is connected with the electrode blocks, and the electrode blocks are in contact with the sensing layer (5). The sensing unit (1) is in a planar radial shape, comprising a central part (11) and a plurality of radial extension parts (12), one end of the radial extension part (12) is integrally formed with the central part (11), and the plurality of radial extension parts (12) are distributed around the central part (11). The electrode blocks comprise an inner ring electrode (2) and an outer ring electrode (22), the inner ring electrode (2) is in contact with the central part (11), and the outer ring electrode (22) is in contact with one end of the radial extension part (12) away from the central part (11).

2. A flexible crack sensor for a tunnel lining according to claim 1, characterized in that The inner ring electrode (2) is provided with a mounting groove (21) for placing the processing module (3), the processing module (3) comprises a signal converter (31) and an alarm lamp (32), the signal converter (31) is electrically connected with the sensing layer (5), and the alarm lamp (32) is electrically connected with the signal converter (31).

3. Flexible crack sensor for a tunnel second lining according to claim 1 or 2, characterized in that Further comprising a protective shell (4), the protective shell (4) is located on the side of the electrode blocks away from the sensing unit (1), and the protective shell (4) seals the gap between the inner ring electrode (2) and the outer ring electrode (22).

4. A flexible crack sensor for a tunnel lining according to claim 1 or 2, characterized in that The sensing unit (1) further comprises a strain transmission layer (6), the strain transmission layer (6) is in contact with and fixedly connected with the sensing layer (5), and the strain transmission layer (6) is made of a auxetic material.

5. A flexible crack sensor for a tunnel lining according to claim 4, characterized in that The strain transmission layer (6) is provided with a piezoelectric material (61) therein, and the piezoelectric material (61) is used for supplying power to the power supply battery (34).

6. A flexible crack sensor for a tunnel lining according to claim 1 or 2, characterized in that The sensing unit (1) further comprises a bonding layer (7), the bonding layer (7) is fixedly connected with the sensing layer (5), and the side of the bonding layer (7) away from the sensing layer (5) is attached to the inner wall of the tunnel.

7. A flexible crack sensor for a tunnel lining according to claim 1 or 2, characterized in that The sensing unit (1) further comprises a protective layer (8), and the protective layer (8) is fixedly connected with the sensing layer (5).

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