Shield tunnel temporary side crack monitoring device

Abstract

The application discloses a shield tunnel temporary side crack monitoring device, which comprises a composite self-induction coating, a wireless acquisition module, a first electrode sheet, a second electrode sheet and a fixed electrode support; the composite self-induction coating comprises a flexible self-induction layer and a friction layer, the flexible self-induction layer is closely laid on the outer arc surface of a segment and generates corresponding opening and closing with the outer arc surface of the segment, the friction layer is closely laid on the flexible self-induction layer and generates a frictional electric signal with the flexible self-induction layer after the flexible self-induction layer cracks with the outer arc surface of the segment; two fixed electrode supports are respectively arranged at two ends of the segment and respectively fix one first electrode sheet and one second electrode sheet; two first electrode sheets are respectively connected to two ends of the flexible self-induction layer, and two second electrode sheets are respectively connected to two ends of the friction layer; and the wireless acquisition module is used for acquiring the frictional electric signal of the first electrode sheet and the second electrode sheet. The application can realize distributed long-term real-time monitoring of the outer arc surface cracking of a shield tunnel segment.

Description

Technical Field

[0001] This invention relates to the field of monitoring structural defects in shield tunnels, and is a device for monitoring cracks on the soil-facing side of shield tunnels. Background Technology

[0002] Segment construction is the load-bearing component of a subway shield tunnel. Influenced by construction techniques, operational loads, and the operating environment, it may develop defects such as cracks, leading to deterioration of the tunnel's structural performance and impacting its overall safety and durability. Based on the ease of detection, shield tunnel defects can be categorized into exposed defects and hidden defects. Exposed defects are those that can be detected by visual observation or specialized equipment, such as cracks on the inner arc surface of the segment. However, there is currently no effective equipment for detecting hidden defects. This type of defect often occurs on the soil-facing side of the shield tunnel. Due to its difficulty in detection and the complexity of influencing factors, its harm is greater, primarily manifesting as cracks on the soil-facing side of the shield tunnel, i.e., cracks on the outer arc surface of the segment.

[0003] Because shield tunnels are buried underground, the soil may contain water, oxygen, chloride ions, etc. When macroscopic cracks appear on the side adjacent to the soil, these components can enter the interior through the cracks, causing steel corrosion. This not only reduces the bonding performance between the steel and concrete, but the expansion pressure of the steel corrosion products can also cause further cracking on the outer arc surface of the tunnel segment, resulting in deterioration of the overall structural performance and seriously threatening operational safety.

[0004] Currently, there are no monitoring measures specifically for cracks on the soil-facing side of shield tunnels; most monitoring focuses on exposed defects such as the arc surface inside the tunnel. Because there is almost no space on the soil-facing side of shield tunnels, and the complex environment prevents the adoption of other monitoring methods, there is no effective way to conduct distributed, long-term, real-time monitoring of cracks on the soil-facing side of shield tunnels. Summary of the Invention

[0005] The purpose of this invention is to provide a crack monitoring device for the soil-adjacent side of a shield tunnel, which is used for distributed long-term real-time monitoring of cracking behavior on the soil-adjacent side to ensure the safety of the overall structure.

[0006] The objective of this invention can be achieved through the following technical solutions: A device for monitoring cracks on the soil-adjacent side of a shield tunnel, the device mainly includes a composite self-sensing coating, a wireless acquisition module, two first electrode plates, two second electrode plates, and two fixed electrode supports; The composite self-sensing coating includes a flexible self-sensing layer and a friction layer. The flexible self-sensing layer is laid close to the outer arc surface of the tube segment and expands and contracts accordingly as the outer arc surface of the tube segment cracks. The friction layer is laid close to the flexible self-sensing layer and generates a relative displacement with the flexible self-sensing layer after the outer arc surface of the tube segment cracks, thus generating a triboelectric signal. Two fixed electrode supports are respectively located at both ends of the tube segment, and each fixed electrode support contains a first electrode plate and a second electrode plate; Two first electrode plates are respectively connected to the two ends of the flexible self-sensing layer, and two second electrode plates are respectively connected to the two ends of the friction layer; The wireless acquisition module is used to acquire the triboelectric signals of the first electrode plate and the second electrode plate.

[0007] Furthermore, the composite self-sensing coating also includes a functional layer, which is laid in close contact with the friction layer to protect the flexible self-sensing layer and the friction layer.

[0008] Furthermore, the functional layer may be one or more layers, including one or more layers such as an anti-chloride ion permeation functional layer and an anti-permeation layer.

[0009] Furthermore, the flexible self-sensing layer and the friction layer are mainly composed of materials capable of generating electricity through friction. The flexible self-sensing layer and the friction layer have different affinities for electrons. The friction layer has a larger elastic modulus than the flexible self-sensing layer. The surface of the friction layer is roughened. When the outer arc surface of the tube segment is not cracked, the flexible self-sensing layer remains relatively stationary with the friction layer and is in a non-charged state. When the outer arc surface of the tube segment cracks, the flexible self-sensing layer maintains a high degree of tension with the crack. The friction layer remains in its original state and rubs against the flexible self-sensing layer in the tension state when the crack is cracked, generating an electrical signal at the crack.

[0010] Furthermore, the fixed electrode support includes a vertical plate, which is fixed to the tube segment. The vertical plate has two electrode slots on the side facing the tube segment to respectively install a first electrode plate and a second electrode plate. The depth of the electrode slot for installing the first electrode plate is greater than the depth of the electrode slot for installing the second electrode plate, so that the first electrode plate contacts the flexible self-sensing layer and the second electrode plate contacts the friction layer.

[0011] Furthermore, the fixed electrode support also includes a placement boss and a drying cage. The placement boss is located between the two electrode slots and is provided with blind holes at intervals. The blind holes are used to fix the tenons of the drying cage, and the drying cage is used to load desiccant.

[0012] Furthermore, the overall length of the drying cage is shorter than the length of the placement boss. The drying cage includes a top plate and a bottom plate arranged opposite each other, two side plates and two wire meshes respectively connecting the top plate and the bottom plate, and the surface of the bottom plate is provided with a tenon that matches the blind hole.

[0013] Furthermore, the fixed electrode support also includes a mudguard plate, which is disposed on the vertical plate. An embedding platform is provided on one side of the mudguard plate, which is used to embed into the external soil.

[0014] Furthermore, a sheet-like solid desiccant, including activated carbon, is placed inside the drying cage to absorb moisture, and the wire mesh can prevent the desiccant from passing through.

[0015] Furthermore, the flexible self-sensing layer is grid-shaped, strip-shaped, or integral, and the composite self-sensing coating is uniformly laid in each layer; the overall height of the shield tunnel soil-side crack monitoring device is 1~3mm to meet the smoothness and sealing requirements during segment assembly and shield tail grouting. Beneficial effects

[0016] Compared with existing technologies, the present invention has at least the following beneficial effects: The present invention proposes a shield tunnel adjacent to soil crack monitoring device, which applies a composite self-inductive coating to the outer arc surface of the tunnel segment. Both ends of the coating are connected to electrode plates in a fixed electrode support. When a crack occurs on the outer arc surface of the tunnel segment, the flexible self-inductive layer maintains a high degree of consistency with the cracking behavior and generates relative displacement with the friction layer at the crack, thereby generating a triboelectric signal characterizing the crack's features. This triboelectric signal is received by a wireless acquisition module pre-embedded within the tunnel segment and fed into an information terminal. Therefore, the beneficial effects of the present invention are: (1) It can perform distributed long-term real-time monitoring of cracks on the soil side of shield tunnels, collect information such as the location, width and distribution of cracks on the soil side, fill the gap in this field and ensure the safety of the overall structure. (2) By setting each functional layer in the composite self-sensing coating, the overall durability of the tunnel segment against the harsh environment on the soil side is enhanced; (3) The flexible self-sensing layer can be deployed in different ways to meet the corresponding crack monitoring accuracy requirements. It is widely used and quite flexible. (4) The overall layout of the device is simple and can be mass-produced and constructed, which is efficient and convenient. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0018] Figure 1 A schematic diagram of the shield tunnel soil-side crack monitoring device of the present invention is shown. Figure 2 A schematic cross-sectional view of the fixed electrode support of the present invention is shown; Figure 3 A schematic cross-sectional view of the fixed electrode support of the present invention is shown; Figure 4 A schematic cross-sectional view of the drying cage of the present invention is shown; Among them, 1. Composite self-inductive coating; 2. Fixed electrode support; 3. Electrode sheet; 4. Tube sheet; 5. Drying cage; 201. Vertical plate; 202. Side insert plates; 203. Electrode groove; 204. Blind hole; 205. End insulation pad; 206. Shovel-shaped embedding platform; 207. Storage boss; 208. Mudguard; 501. Wire mesh; 502. Tenon; 503. Side plate; 504. Top plate; 505. Bottom plate. Implementation

[0019] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Please see Figure 1-4 A device for monitoring cracks on the soil side of a shield tunnel, the monitoring device mainly includes a composite self-sensing coating 1, a wireless acquisition module, two first electrode plates 3, two second electrode plates 4 and two fixed electrode supports 2. The composite self-sensing coating 1 includes a flexible self-sensing layer and a friction layer. The flexible self-sensing layer is laid close to the outer arc surface of the tube segment 6 and expands and contracts accordingly as the outer arc surface of the tube segment 6 cracks. The friction layer is laid close to the flexible self-sensing layer and generates a relative displacement with the flexible self-sensing layer after the outer arc surface of the tube segment 6 cracks, thus generating a triboelectric signal. Two fixed electrode supports 2 are respectively located at both ends of the tube 6, and a first electrode plate 3 and a second electrode plate 4 are fixed in each fixed electrode support 2. Two first electrode plates 3 are respectively connected to the two ends of the flexible self-sensing layer, and two second electrode plates 4 are respectively connected to the two ends of the friction layer; The wireless acquisition module is used to acquire the triboelectric signals of the first electrode plate 3 and the second electrode plate 4.

[0021] The electrical signals collected by the wireless acquisition module are transmitted to the processing end via wireless communication to characterize the corresponding information of the cracks.

[0022] The side facing the soil refers to the outer arc surface of the pipe segment 6. The composite self-sensing coating 1 can be applied to the outer arc surface of any type of pipe segment 6, such as: capping block, adjacent block, standard block; preferably, the composite self-sensing coating 1 is applied to the outer arc surface of all types of pipe segments 6 to achieve a comprehensive monitoring effect.

[0023] The application can be done by spraying, dipping or other processes, as long as the composite self-sensing coating 2 can be applied properly.

[0024] The composite self-sensing coating 1 also includes a functional layer, which is laid close to the friction layer to protect the flexible self-sensing layer and the friction layer.

[0025] The functional layer may be one or more layers, including one or more layers such as an anti-chloride ion permeation functional layer and an anti-permeation layer.

[0026] The functional layers can be modified to correspond to their specific functions according to the surrounding soil environment, and can also be set up with features such as an anti-oxidation layer.

[0027] To ensure proper assembly of segment 6, the thickness of each layer of the composite self-sensing coating 1 should not be too thick, and its overall thickness can be 3-5mm.

[0028] The flexible self-sensing layer and the friction layer are mainly composed of materials capable of generating electricity through friction. The flexible self-sensing layer and the friction layer have different affinities for electrons. The friction layer has a larger elastic modulus than the flexible self-sensing layer. The surface of the friction layer is roughened. When the outer arc surface of the tube 6 is not cracked, the flexible self-sensing layer remains relatively stationary with the friction layer and is in a non-charged state. When the outer arc surface of the tube 6 cracks, the flexible self-sensing layer maintains a high degree of tension with the crack. The friction layer remains in its original state and rubs against the flexible self-sensing layer in the tension state when the crack is cracked, generating an electrical signal at the crack.

[0029] The affinity of the flexible self-sensing layer and the friction layer for electrons should differ significantly. The flexible self-sensing layer may be made of polymers such as polyethylene terephthalate, but is not limited to, and the friction layer may be made of polymers such as polyvinyl alcohol.

[0030] The fixed electrode support 2 includes a vertical plate 201, which is fixed to the tube 6. The vertical plate 201 has two electrode grooves 203 on the side facing the tube 6 to respectively install a first electrode plate 3 and a second electrode plate 4. The depth of the electrode groove 203 for installing the first electrode plate 3 is higher than the depth of the electrode groove 203 for installing the second electrode plate 4, so that the first electrode plate 3 contacts the flexible self-sensing layer and the second electrode plate 4 contacts the friction layer.

[0031] In the illustrated embodiment, an end insulating pad 205 is provided between the first electrode plate 3, the second electrode plate 4 and the groove wall of the electrode groove 23.

[0032] The fixed electrode support 2 also includes a placement boss 207 and a drying cage 5. The placement boss 207 is located between two electrode slots 203. The placement boss 207 is provided with blind holes 204 at intervals. The blind holes 204 are used to fix the tenon 502 of the drying cage 5. The drying cage 5 is used to load desiccant.

[0033] The overall length of the drying cage 5 is shorter than the length of the placement boss 207. The drying cage 5 includes a top plate 504 and a bottom plate 505 arranged opposite to each other, and two side plates 503 and two wire meshes 501 respectively connecting the top plate 504 and the bottom plate 505. The surface of the bottom plate 505 is provided with a tenon 502 that matches the blind hole 204.

[0034] A sheet-like solid desiccant, such as activated carbon, is placed inside the drying cage 5 to absorb moisture. The wire mesh 501 prevents the desiccant from leaking out through the gaps in the wire mesh 501.

[0035] The fixed electrode support 2 also includes a mudguard 208, which is disposed on the vertical plate 201. An embedding platform 206 is provided on one side of the mudguard 208. The embedding platform 206 is used to embed into the external soil to ensure that the monitoring device is tightly embedded with the grouting layer and the external soil.

[0036] The fixed electrode support also includes two side plates 202. The two side plates 202 are located between the vertical plate 201 and the mudguard 208. The connection between the two side plates 202 and the vertical plate 201 and the mudguard 208 is provided with multiple locking teeth for fixing. The bottom of the two side plates 202 can precisely block the two ends of the two electrode slots 203, and its upper end is consistent with the vertical plate (201).

[0037] The flexible self-sensing layer is grid-shaped, strip-shaped, or integral, and the composite self-sensing coating is uniformly applied to each layer.

[0038] The overall height of the shield tunnel adjacent soil crack monitoring device is 1~3mm to meet the smoothness and sealing requirements during segment assembly and shield tail grouting.

[0039] Implementation Example: This invention includes a shield tunnel soil-side crack monitoring device for distributed, long-term, real-time monitoring of soil-side cracks. The shield tunnel soil-side crack monitoring device mainly includes a composite self-sensing coating, a fixed electrode support, electrode plates, tunnel segments, and a drying cage.

[0040] In this example, the composite self-sensing coating applied to the outer arc surface of the pipe segment consists of four layers: a flexible self-sensing layer, a friction layer, an anti-chloride ion penetration layer, and an anti-permeability layer, which are arranged in sequence next to the outer arc surface. The flexible self-sensing layer is arranged in a grid pattern, and each layer is 1 mm thick. The overall length of the fixed electrode support is consistent with the width of the pipe segment, and its overall height is set to 1 cm.

[0041] The flexible self-sensing layer bonds well with the outer arc surface of the pipe segment, and its elastic modulus is much smaller than that of the pipe segment, thus ensuring that it can maintain a high degree of consistency with the development of cracks on the adjacent side. The elastic modulus of the outer friction layer is greater than that of the flexible self-sensing layer, so that when the flexible self-sensing layer cracks with the outer arc surface, the friction layer does not produce corresponding cracking deformation, resulting in relative displacement between the two, friction, and thus generating triboelectric signals to characterize the location, width, distribution and other information of the cracks.

[0042] The electrode sheet material connected to the flexible self-sensing layer at both ends is made of polyethylene terephthalate, while the electrode sheet material connected to the friction layer is made of polyvinyl alcohol. At the same time, the side of the friction layer that contacts the flexible self-sensing layer is roughened. The electrode groove embedded in the electrode sheet connected to the friction layer is 1 mm deeper than the other electrode groove, so that the height difference at the top of the two electrode sheets after they are fully embedded is 1 mm, which is the thickness of the friction layer, ensuring that the electrode sheet is well connected to each layer. Thin sheet activated carbon is placed in the drying cage to absorb moisture.

[0043] This invention can be mass-produced and installed, is convenient to lay, and can perform distributed long-term real-time monitoring of cracks on the outer arc surface of shield tunnel segments, and evaluate the overall structural performance of the tunnel in real time to ensure the safety of train operation.

[0044] The examples described above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made based on the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for monitoring cracks on the soil-facing side of a shield tunnel, characterized in that: The monitoring device mainly includes a composite self-sensing coating (1), a wireless acquisition module, two first electrode plates (3), two second electrode plates (4), and two fixed electrode supports (2). The composite self-sensing coating (1) includes a flexible self-sensing layer and a friction layer. The flexible self-sensing layer is laid close to the outer arc surface of the tube segment (6) and expands and contracts accordingly as the outer arc surface of the tube segment (6) cracks. The friction layer is laid close to the flexible self-sensing layer and generates a relative displacement with the flexible self-sensing layer after the outer arc surface of the tube segment (6) cracks, thus generating a frictional electrical signal. The flexible self-sensing layer and the friction layer are mainly composed of materials that can generate electricity through friction. The flexible self-sensing layer and the friction layer have different affinities for electrons. The friction layer has a larger elastic modulus than the flexible self-sensing layer. The surface of the friction layer is roughened. When the outer arc surface of the tube segment (6) is not cracked, the flexible self-sensing layer remains relatively stationary with the friction layer and is in a non-charged state. When the outer arc surface of the tube segment (6) cracks, the flexible self-sensing layer maintains a high tension state with the crack. The friction layer remains in its original state and rubs against the flexible self-sensing layer in the tension state when the crack is cracked, generating an electrical signal at the crack. Two fixed electrode supports (2) are respectively located at both ends of the tube segment (6), and a first electrode plate (3) and a second electrode plate (4) are fixed in each fixed electrode support (2). Two first electrode plates (3) are respectively connected to the two ends of the flexible self-sensing layer, and two second electrode plates (4) are respectively connected to the two ends of the friction layer; The fixed electrode support (2) includes a vertical plate (201), which is fixed to the tube (6). The vertical plate (201) has two electrode grooves (203) on the side facing the tube (6) to install the first electrode plate (3) and the second electrode plate (4) respectively. The depth of the electrode groove (203) for installing the first electrode plate (3) is higher than the depth of the electrode groove for installing the second electrode plate (4), so that the first electrode plate (3) contacts the flexible self-sensing layer and the second electrode plate (4) contacts the friction layer. The wireless acquisition module is used to acquire the triboelectric signals of the first electrode plate (3) and the second electrode plate (4); The overall height of the shield tunnel adjacent soil crack monitoring device is 1~3mm.

2. The device for monitoring cracks on the soil-facing side of a shield tunnel according to claim 1, characterized in that: The composite self-sensing coating (1) also includes a functional layer, which is laid close to the friction layer to protect the flexible self-sensing layer and the friction layer.

3. The device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 2, characterized in that: The functional layer may be one or more layers, including one or more of the following: a chloride ion permeation resistant functional layer and an anti-permeation layer.

4. The device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 1, characterized in that: The fixed electrode support (2) also includes a placement boss (207) and a drying cage (5). The placement boss (207) is located between two electrode slots (203). The placement boss (207) is provided with blind holes (204) at intervals. The blind holes (204) are used to fix the tenon (502) of the drying cage (5). The drying cage (5) is used to load desiccant.

5. A device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 4, characterized in that: The overall length of the drying cage (5) is shorter than the length of the placement boss (207). The drying cage (5) includes a top plate (504) and a bottom plate (505) arranged opposite to each other, and two side plates (503) and two wire meshes (501) respectively connecting the top plate (504) and the bottom plate (505). The bottom plate (505) has a tenon (502) that matches the blind hole (204) on its surface.

6. The device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 5, characterized in that: The fixed electrode support (2) also includes a mudguard (208), which is disposed on the vertical plate (201). An embedding platform (206) is provided on one side of the mudguard (208), which is used to embed the grouting layer and the external soil.

7. A device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 6, characterized in that: A sheet-like solid desiccant, including activated carbon, is placed inside the drying cage (5) to absorb moisture. The wire mesh (501) can prevent the desiccant from passing through.

8. The device for monitoring cracks on the soil-adjacent side of a shield tunnel according to claim 1, characterized in that: The flexible self-sensing layer is grid-shaped, strip-shaped, or integral, and the composite self-sensing coating is evenly applied to each layer to meet the requirements of smoothness and sealing during segment assembly and tail grouting.

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