Monitoring device and method for monitoring horizontal displacement of foundation pit based on piezoelectric sensing

Abstract

The invention discloses a monitoring device and method for monitoring horizontal displacement of a foundation pit based on piezoelectric sensing, the monitoring device comprises an acquisition instrument, a total signal transmission line and a monitoring assembly, the monitoring assembly is pre-buried in a peripheral soil body of the foundation pit and / or installed on the inner wall of the foundation pit, the monitoring assembly comprises a plurality of monitoring units, the plurality of monitoring units are vertically connected to form a monitoring surface, and the monitoring surface is provided with a plurality of piezoelectric sensors. Each monitoring unit internally comprises a piezoelectric cable network and a signal conduction piece, the piezoelectric cable networks are connected with the signal conduction pieces, the piezoelectric cable networks are used for monitoring impedance signals, the signal conduction pieces are used for transmitting the impedance signals, one end of the total signal transmission line vertically penetrates through the multiple monitoring units and is communicated with the signal conduction pieces of the multiple monitoring units, and the other end of the total signal transmission line is communicated with the signal conduction pieces of the multiple monitoring units. According to the foundation pit horizontal displacement monitoring device, the situation that only single-point displacement data can be obtained through traditional monitoring can be avoided, and more comprehensive and accurate data support is provided for foundation pit safety early warning.

Description

Technical Field

[0001] This invention relates to a monitoring device and method for horizontal displacement of a foundation pit based on piezoelectric sensing. Background Technology

[0002] Horizontal deformation of soil has always been a problem in the construction and operation of foundation pit projects. In recent years, foundation pit deformation and collapse accidents have seriously endangered people's lives and property. Therefore, monitoring the horizontal deformation of soil is particularly critical, as it aims to reflect the deformation and stability of underground structures in the horizontal direction.

[0003] Traditional monitoring equipment mostly adopts a point-based monitoring mode. Point-based monitoring can only obtain displacement data of discrete single points, which cannot reflect the differences and rates of change in soil displacement between adjacent monitoring points. It is difficult to comprehensively judge the overall deformation characteristics of the entire foundation pit surface, and the incomplete data can easily lead to delayed safety warnings. Although there is some research on the application of piezoelectric materials in structural health monitoring, it mainly focuses on damage monitoring and has not developed a dedicated monitoring device for horizontal displacement of foundation pits.

[0004] Meanwhile, existing point-based monitoring schemes mostly adopt a single deployment method, or only focus on monitoring one side of the perimeter or inner wall of the foundation pit, making it difficult to fully capture the complete horizontal deformation process of the foundation pit soil from the perimeter to the pit wall. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a monitoring device and method for horizontal displacement of foundation pit based on piezoelectric sensing. This device can avoid the limitations of traditional monitoring which can only obtain single-point displacement data, and provide more comprehensive and accurate data support for foundation pit safety early warning.

[0006] To achieve the above objectives, this application provides the following technical solution: a monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing, comprising a data acquisition unit, a main signal transmission line, and a monitoring component. The monitoring component is pre-embedded in the soil surrounding the foundation pit and / or installed on the inner wall of the foundation pit. The monitoring component includes multiple monitoring units, which are vertically connected to form a monitoring surface. Each monitoring unit includes a piezoelectric cable network and a signal transmission component. The piezoelectric cable network is connected to the signal transmission component. The piezoelectric cable network is used to monitor impedance signals, and the signal transmission component is used to transmit impedance signals. One end of the main signal transmission line vertically passes through multiple monitoring units and is connected to the signal transmission components of multiple monitoring units. The other end of the main signal transmission line is connected to the data acquisition unit, thereby realizing the monitoring of horizontal displacement of the foundation pit.

[0007] Furthermore, the monitoring unit includes a first flexible plate and a second flexible plate. Waterproof elastic elements are provided on the front and rear opposite sides of the first and second flexible plates. Upper and lower opposite end faces of the flexible plates are provided with upper and lower stepped surfaces. The top view cross section of the flexible plates is arc-shaped wave-shaped. The arc-shaped wave-shaped section consists of straight segments and arc segments evenly arranged. Expansion elastic elements are provided between the relatively straight segments. The relatively arc segments together form a limiting cavity.

[0008] Furthermore, the piezoelectric cable network includes multiple piezoelectric cable segments of a certain length, which are distributed within corresponding limiting cavities and reinforced with adhesive.

[0009] Furthermore, the upper cavity is formed by the relative upper stepped surfaces, and the signal transmission element is distributed in the upper cavity. The signal transmission element includes a first multi-core wire, and the core wires in the first multi-core wire are all connected to the piezoelectric cable segment.

[0010] Furthermore, the total signal transmission line includes multiple sets of second multi-core wires, which are connected to corresponding first multi-core wires, and the number of cores in the second multi-core wires is the same as that in the first multi-core wires.

[0011] Furthermore, it also includes a vertical assembly component that connects adjacent monitoring units, which is a sleeve with upper and lower bayonets.

[0012] This application also provides a monitoring method, including the following steps: S1: Based on the foundation pit grade, geological conditions and support type, determine the layout parameters of the first monitoring device on the periphery and the layout parameters of the monitoring device on the inner wall of the foundation pit, and complete the construction design; S2: Before the foundation pit is excavated, the first monitoring device is installed, the pre-embedded parts of the first monitoring device are completed, and the initial data is collected; S3: The foundation pit is excavated in layers. After each layer is excavated, the inner wall is cleaned and leveled. The monitoring device is installed using a connection method that is compatible with the support type. S4: If monitoring data is required, the monitoring data is obtained by connecting the first monitoring component and the monitoring device with the data acquisition instrument, thereby monitoring the horizontal deformation of the foundation pit soil.

[0013] Furthermore, the first monitoring component includes a clinometer tube, a clinometer probe, and a control cable. The clinometer tube is installed 3-5 meters outside the edge of the foundation pit and is evenly distributed along the perimeter of the foundation pit. It is pre-embedded by drilling and the tube is filled with grout to achieve tube-soil connection. When monitoring is required, the clinometer probe is connected to the data acquisition instrument through the control cable, and the data is collected by lowering the clinometer probe into the clinometer tube.

[0014] Furthermore, the first monitoring component includes a clinometer tube, which is multi-segmented and connected end to end to form a whole. Each clinometer tube segment is provided with at least one piezoelectric geocable cable. The top end of each piezoelectric cable segment is connected to the corresponding core wire in the third multi-core conductor. The third multi-core conductor runs through the clinometer tube and has multiple conductor connectors at its end. The conductor connectors are connected to the data acquisition instrument to collect the impedance signal of each piezoelectric cable segment.

[0015] Furthermore, the monitoring device is installed on the inner wall of the foundation pit using different fixing methods depending on the support type: If the support type is pile support, the gaps between the piles need to be filled with cement mortar first, and then a bracket is installed on the pile. The monitoring device is fixed to the bracket, and the flexible plate of the monitoring device is attached to the end face of the support structure with an adhesive surface. If the support type is a diaphragm wall, the wall is pre-embedded with protruding strips. The protruding strips have slots and the slot openings are fitted with sealing strips. When installing the monitoring device, the sealing strips are removed, and the slots on the flexible plate of the monitoring device are aligned and inserted. The flexible plate has an adhesive surface facing the wall.

[0016] Beneficial effects: ① This application forms a monitoring surface by connecting multiple monitoring units. The monitoring unit includes an arc-shaped corrugated flexible plate, a waterproof elastic component, a piezoelectric cable network, and a signal transmission component. A limiting cavity is formed between the flexible plates, which can accurately constrain the layout of the piezoelectric cable segment and avoid signal deviation caused by cable displacement. It is also reinforced with adhesive to further ensure the adhesion between the piezoelectric cable and the flexible plate, so that the soil displacement can be directly converted into the impedance change of the piezoelectric cable. The first flexible plate, the second flexible plate, and the waterproof elastic component protect the signal transmission component and the piezoelectric cable network, ensuring the continuous and stable monitoring data and preventing the influence of the external environment.

[0017] ② This application also uses vertical splicing components to connect multiple monitoring units, which can flexibly adjust the height of the monitoring surface according to the depth of the foundation pit. In addition, multiple sets of second multi-core wires of the main signal transmission line are connected to the signal transmission components of the monitoring units to ensure independent transmission and synchronous acquisition of the impedance signals of each piezoelectric cable, thereby realizing distributed monitoring.

[0018] ③ This application also implements different fixing methods for monitoring devices according to different support structures. The monitoring components are pre-embedded in the soil outside the foundation pit or installed on the inner wall of the foundation pit. Combined with the collaborative monitoring of the first monitoring component, a monitoring system covering both inside and outside is formed, which improves the comprehensive monitoring of the horizontal deformation of the foundation pit soil. Attached Figure Description

[0019] Figure 1 Schematic diagram for monitoring horizontal displacement of the foundation pit; Figure 2 This is a schematic diagram of the monitoring components; Figure 3A schematic diagram of the internal structure of the monitoring component; Figure 4 This is a schematic diagram of the first type of telescopic elastic element; Figure 5 This is a schematic diagram of the second type of telescopic elastic element; Figure 6 This is a schematic diagram of the third type of telescopic elastic element; Figure 7 This is a schematic diagram of the vertically assembled components; Figure 8 A schematic diagram showing the monitoring components installed on the pile foundation; Figure 9 A schematic diagram showing the monitoring components installed on a diaphragm wall. Figure 10 This is a schematic diagram of the inside of the inclinometer tube in Example 3.

[0020] Reference numerals: 1. Acquisition device; 2. Main signal transmission line; 3. Monitoring component; 4. Monitoring unit; 4-1. Piezoelectric cable network; 4-2. Signal transmission component; 5. First flexible plate; 6. Second flexible plate; 7. Waterproof elastic component; 8. Step surface; 9. Telescopic elastic component; 10. Limiting cavity; 11. Upper cavity; 12. Ear seat; 13. Second multi-core wire; 14. Vertical assembly component; 14-1. Sleeve; 15. First monitoring component; 16. Inclinometer tube; 17. Third multi-core wire; 18. Bracket; 19. Protrusion; 20. Clip; 21. Adhesive surface; 22. Piling; 23. Diaphragm wall; 24. Piezoelectric cable segment. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structure, features and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0022] For reference Figures 1-10As shown in the embodiment, this application provides a monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing. The device includes a data acquisition unit 1, a main signal transmission line 2, and a monitoring component 3. The monitoring component 3 is pre-embedded in the soil surrounding the foundation pit and / or installed on the inner wall of the foundation pit. The monitoring component 3 includes multiple monitoring units 4, which are vertically connected to form a monitoring surface. The monitoring surface accurately captures the displacement differences between adjacent soil masses. The soil displacement within the monitoring range of different monitoring units 4 is synchronously transmitted to the data acquisition unit 1. Based on the differentiated signals, the device can analyze the displacement difference and displacement change rate between adjacent soil masses, avoiding the limitations of traditional point monitoring which only acquires single-point displacement data. By combining the signal distribution characteristics of each monitoring unit 4, the displacement of the foundation pit surface is comprehensively judged, providing more comprehensive and accurate data support for foundation pit safety. To connect vertically adjacent monitoring units 4, a vertical splicing component 14 is provided. The vertical splicing component 14 is a sleeve 14-1 with upper and lower latches. The sleeve 14-1 is shaped to fit the monitoring unit 4, ensuring that the sleeve 14-1 can be inserted into the upper or lower end of the monitoring unit 4. To ensure a secure connection, the monitoring unit 4 has a first horizontal connecting hole at its upper or lower end. The sleeve 14-1 has an insertion hole corresponding to the first horizontal connecting hole. A plug is inserted into the insertion hole and coated with waterproof adhesive, thus connecting the sleeve 14-1 to the monitoring unit 4. Other connection methods can also be used, such as bonding or binding reinforcement. This application preferably uses a plug and waterproof adhesive for connection.

[0023] For reference Figures 1-10 As shown, the inner wall of each monitoring unit 4 includes a piezoelectric cable network 4-1 and a signal transmission component 4-2. The piezoelectric cable network 4-1 is connected to the signal transmission component 4-2. The piezoelectric cable network 4-1 is used to monitor impedance signals, and the signal transmission component 4-2 is used to transmit impedance signals. One end of the total signal transmission line 2 runs vertically through multiple monitoring units 4 and is connected to the signal transmission components 4-2 of multiple monitoring units 4. The other end of the total signal transmission line 2 is connected to the data acquisition instrument 1, thereby realizing the monitoring of the horizontal displacement of the foundation pit.

[0024] Specifically, the piezoelectric cable mesh 4-1 includes multiple piezoelectric cable segments 24 of a certain length, and the signal transmission component 4-2 includes a first multi-core conductor. The monitoring unit 4 includes a first flexible plate 5 and a second flexible plate 6. The front and rear opposite sides of the first flexible plate 5 and the second flexible plate 6 are provided with waterproof elastic components 7. The waterproof elastic components 7 are waterproof elastic membranes, waterproof elastic nets, waterproof elastic plates, or stretchable corrugated plates, which are circumferentially sealed by the first flexible plate 5, the second flexible plate 6, and the waterproof elastic components 7. The upper and lower opposite end faces of the flexible plates are provided with upper and lower stepped surfaces 8, which together form an upper cavity 11. The top view cross section of the flexible plates is an arc-shaped corrugated shape, which consists of straight sections and arc-shaped sections evenly arranged. Between the relatively straight sections, there are telescopic elastic components 9. The telescopic elastic components 9 are telescopic springs, multi-stage telescopic rods, or a combination of telescopic springs and multi-stage telescopic rods, which realize the connection between the middle parts of the relatively flexible plates. The relatively curved segments together form a limiting cavity 10. Piezoelectric cable segments 24 are distributed within their respective limiting cavities 10 and reinforced with adhesive to ensure the piezoelectric cable segments 24 are taut and tightly fitted to the first flexible plate 5 and the second flexible plate 6. This ensures the piezoelectric cable segments 24 can smoothly sense soil changes and generate impedance signals. A first multi-core conductor is distributed within the upper cavity 11. The length of the first multi-core conductor is longer than the length of the piezoelectric cable segment 24, creating a certain length redundancy. Multiple symmetrical lugs 12 are provided within the upper cavity 11 to restrict the first multi-core conductor and prevent it from detaching from the upper cavity 11. For example, the monitoring unit 4 has four sets of limiting cavities 10, four piezoelectric cable segments 24, and four sets of core wires corresponding to each piezoelectric cable segment 24 within the first multi-core conductor. Each core wire of the first multi-core conductor is connected to a corresponding piezoelectric cable segment 24, enabling independent transmission of the impedance signal of a single piezoelectric cable, avoiding mutual interference between signals, and improving the quality of monitoring data. The main signal transmission line 2 includes multiple sets of second multi-core conductors 13, which are connected to corresponding first multi-core conductors. The number of cores in each second multi-core conductor is the same as that in the first multi-core conductor. Through the configuration of the main signal transmission line 2, impedance signals can be transmitted to the data acquisition instrument 1. The monitoring device of this application monitors the horizontal displacement of the foundation pit by setting up multiple monitoring surfaces. Multiple sets of monitoring data are available within each monitoring surface. These multiple sets of data can be used to determine whether the soil displacement on that surface is uniform or uneven, and whether there is concentrated horizontal displacement, thereby comprehensively judging the horizontal displacement of that side of the foundation pit.

[0025] For reference Figure 1 As shown in Embodiment 2, this application also provides a monitoring method using the above-mentioned monitoring device, comprising the following steps: S1: Based on the foundation pit grade, geological conditions and support type, determine the layout parameters of the first monitoring element 15 on the periphery and the layout parameters of the monitoring device on the inner wall of the foundation pit, and complete the construction design; S2: Before the foundation pit is excavated, the first monitoring component 15 is installed, the pre-embedded parts of the first monitoring component 15 are completed and the initial data is collected; S3: The foundation pit is excavated in layers. After each layer is excavated, the inner wall is cleaned and leveled. The monitoring device is installed using a connection method that is compatible with the support type. S4: If monitoring data is required, the monitoring data is obtained by connecting the first monitoring component 15 and the monitoring device with the data acquisition instrument 1, thereby monitoring the horizontal deformation of the foundation pit soil.

[0026] Specifically, the first monitoring component 15 includes a clinometer tube 16, a clinometer probe, and a control cable. The clinometer tube 16 is installed 3-5 meters outside the deformation of the foundation pit, evenly distributed along the perimeter of the foundation pit, and is pre-embedded by drilling. The diameter of the drilled holes is greater than 110 mm. The clinometer tube 16 is lowered and backfilled from the bottom of the hole with a cement-bentonite mixture. The grouting pressure is maintained at 0.3-0.5 MPa to ensure that the tube body is in close contact with the soil. A protective cover is provided at the top and sealed at the bottom. When monitoring is required, the protective cover is opened, and the control cable is connected to the clinometer probe. The probe is then lowered into the clinometer tube 16 to collect monitoring data, thereby realizing the monitoring of the overall horizontal displacement of the deep soil layer. The monitoring device is then installed on the inner wall of the pit to achieve real-time monitoring of the shallow surface. The monitoring device includes multiple monitoring units 4. Before installation, adjacent monitoring units 4 are spliced ​​together, and the main signal transmission line 2 is simultaneously connected to the signal conduction component 4-2 of each monitoring unit 4. All cable connections are waterproof connectors. After installation, the device is checked for integrity and normal operation. Once confirmed, it is installed on the inner wall of the pit using different fixing methods according to the support type. For example... Figure 8 As shown, if the support type is pile 22 support, the gaps between the piles need to be filled with cement mortar first, and then a bracket needs to be installed on the pile 22. The monitoring device is fixed to the bracket 18, and the flexible plate of the monitoring device is attached to the end face of the support structure with an adhesive surface 21 to ensure that the deformation is smoothly conducted to the piezoelectric cable. Or as... Figure 9 As shown, if the support structure is a diaphragm wall 23, the wall is pre-embedded with a protruding strip 19. The protruding strip 19 is provided with a slot and the slot opening is fitted with a sealing strip. When the monitoring device is installed, the sealing strip is removed, and the slot strip 20 on the flexible plate of the monitoring device is symmetrically inserted into the slot. The flexible plate has an adhesive surface 21 facing the wall.

[0027] For reference Figure 10As shown, this application also provides a third embodiment, which is basically the same as the second embodiment, except that the first monitoring component 15 is improved. The first monitoring component 3 in the second embodiment cannot monitor in real time, so the third embodiment improves on this point. Specifically, the inclinometer tube 16 is multi-segmented and connected end to end to form a whole. The overall length of the inclinometer tube 16 is determined according to the required monitoring depth. Each segment of the inclinometer tube 16 is provided with at least one piezoelectric geocable cable. The top end of each piezoelectric cable is connected to the corresponding core wire in the third multi-core conductor 17. The third multi-core conductor 17 runs through the inclinometer tube 16 and has multiple conductor joints at its end. The conductor joints are connected to the data acquisition instrument 1 to collect the impedance signal of each piezoelectric cable segment. Through the combination of the first monitoring component 15 and the monitoring device, the deep horizontal displacement and shallow horizontal displacement are monitored. At the same time, the two monitoring data can be mutually verified to comprehensively judge the horizontal displacement data, providing a more accurate monitoring effect.

Claims

1. A monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing, characterized in that: The system includes a data acquisition unit, a main signal transmission line, and monitoring components. The monitoring components are pre-embedded in the soil surrounding the foundation pit and / or installed on the inner wall of the foundation pit. Each monitoring component consists of multiple monitoring units connected vertically to form a monitoring surface. Each monitoring unit contains a piezoelectric cable network and a signal transmission component. The piezoelectric cable network is connected to the signal transmission component. The piezoelectric cable network is used to monitor impedance signals, and the signal transmission component is used to transmit impedance signals. One end of the main signal transmission line runs vertically through multiple monitoring units and connects to the signal transmission components of multiple monitoring units. The other end of the main signal transmission line is connected to the data acquisition unit, thereby realizing the monitoring of the horizontal displacement of the foundation pit.

2. The monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 1, characterized in that: The monitoring unit includes a first flexible plate and a second flexible plate. Waterproof elastic elements are provided on the front and rear opposite sides of the first and second flexible plates. The upper and lower opposite end faces of the flexible plates are provided with upper and lower stepped surfaces. The top view cross section of the flexible plates is arc-shaped wave-shaped. The arc-shaped wave-shaped section is composed of straight sections and arc-shaped sections evenly arranged. There are telescopic elastic elements between the relatively straight sections. The relatively arc-shaped sections together form a limiting cavity.

3. The monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 2, characterized in that: The piezoelectric cable network includes multiple piezoelectric cable segments of a certain length, which are distributed in corresponding limiting cavities and reinforced with adhesive.

4. The monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 3, characterized in that: The upper cavity is formed by the upper stepped surface and the signal transmission element is distributed in the upper cavity. The signal transmission element includes a first multi-core wire, and the core wires of the first multi-core wire are all connected to the piezoelectric cable segment.

5. The monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 4, characterized in that: The total signal transmission line includes multiple sets of second multi-core conductors, which are connected to corresponding first multi-core conductors, and the number of cores in the second multi-core conductors is the same as that in the first multi-core conductors.

6. The monitoring device for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 5, characterized in that: It also includes a vertical assembly component that connects adjacent monitoring units, which is a sleeve with upper and lower bayonets.

7. A monitoring method using the monitoring device described in claims 1-6, characterized in that: Includes the following steps: S1: Based on the foundation pit grade, geological conditions and support type, determine the layout parameters of the first monitoring device on the periphery and the layout parameters of the monitoring device on the inner wall of the foundation pit, and complete the construction design; S2: Before the foundation pit is excavated, the first monitoring device is installed, the pre-embedded parts of the first monitoring device are completed, and the initial data is collected; S3: The foundation pit is excavated in layers. After each layer is excavated, the inner wall is cleaned and leveled. The monitoring device is installed using a connection method that is compatible with the support type. S4: If monitoring data is required, the monitoring data is obtained by connecting the first monitoring component and the monitoring device with the data acquisition instrument, thereby monitoring the horizontal deformation of the foundation pit soil.

8. The monitoring method for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 7, characterized in that: The first monitoring component includes a clinometer tube, a clinometer probe, and a control cable. The clinometer tube is installed 3-5 meters outside the edge of the foundation pit and is evenly distributed along the perimeter of the foundation pit. It is pre-embedded by drilling and the tube is filled with grout to achieve tube-soil connection. When monitoring is required, the clinometer probe is connected to the data acquisition instrument through the control cable and the data is collected by lowering the clinometer probe into the clinometer tube.

9. The monitoring method for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 7, characterized in that: The first monitoring component includes a clinometer tube, which is multi-segmented and connected end to end to form a whole. Each clinometer tube segment is provided with at least one piezoelectric geocable cable. The top end of each piezoelectric cable segment is connected to the corresponding core wire in a third multi-core conductor. The third multi-core conductor runs through the clinometer tube and has multiple conductor connectors at its end. The conductor connectors are connected to the data acquisition instrument to collect the impedance signal of each piezoelectric cable segment.

10. The monitoring method for horizontal displacement of a foundation pit based on piezoelectric sensing according to claim 8 or 9, characterized in that: The monitoring device is installed on the inner wall of the foundation pit using different fixing methods depending on the type of support: If the support type is pile support, the gaps between the piles need to be filled with cement mortar first, and then a bracket is installed on the pile. The monitoring device is fixed to the bracket, and the flexible plate of the monitoring device is attached to the end face of the support structure with an adhesive surface. If the support type is a diaphragm wall, the wall is pre-embedded with protruding strips. The protruding strips have slots and the slot openings are fitted with sealing strips. When installing the monitoring device, the sealing strips are removed, and the slots on the flexible plate of the monitoring device are aligned and inserted. The flexible plate has an adhesive surface facing the wall.

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