Nondestructive testing device and method for axial force of underwater steel pipe pile

Abstract

According to the nondestructive testing device and method for the axial force of the underwater steel pipe pile, the device is arranged on the outer wall of the steel pipe pile and in a water environment around a steel structure, and a magnetic induction coil array annularly arranged on the outer wall of the steel pipe pile captures the magnetic flux density change of the steel pipe pile; after modulation of the magnetic field monitoring and modulation module, transmission of the underwater wireless transmission unit and inversion algorithm processing of the rear-end data processing unit, the stress state of the steel pipe pile body is obtained. The method comprises the steps that the signal excitation module applies a background magnetic field to the periphery of the magnetic induction coil array, the magnetic induction coil array induces magnetic field changes outside the steel pipe pile in real time, and the magnetic field monitoring and modulating module recognizes the magnetic field changes and converts the magnetic field changes into voltage signals; the modulated voltage signal is sent to a receiving end underwater through an underwater wireless transmission unit, and a rear-end data processing unit calculates the stress distribution in the pile body according to the change of a multi-point magnetic field and by calling a multi-coil magnetic flux inversion algorithm, and outputs real-time displacement trend, stress change and abnormal alarm information.

Description

Technical Field

[0001] This invention relates to the field of geotechnical and structural monitoring technology, and in particular to a non-destructive testing device and method for axial force of underwater steel pipe piles. Background Technology

[0002] In the construction of foundation pits, bridges, and offshore structures, steel pipe piles serve as primary load-bearing components, and changes in their axial force directly impact structural safety. Currently, commonly used methods for detecting pile axial force rely on contact technologies such as embedded strain gauges, fiber optic sensors, or strain meters. However, these methods suffer from difficulties in underwater environments, including installation challenges, poor sealing reliability, and severe signal attenuation. Especially in high turbidity or deep water conditions, sensors struggle to operate stably for extended periods, leading to delayed or even malfunctioning acquisition of pile stress information. Therefore, there is an urgent need for a non-contact method capable of real-time monitoring of pile axial force in complex underwater environments to improve the reliability and intelligence of structural safety monitoring. Summary of the Invention

[0003] Existing methods for detecting axial force in pile foundations suffer from problems such as installation difficulties, poor sealing reliability, and severe signal transmission attenuation in underwater environments. The purpose of this invention is to provide a non-destructive testing device and method for the axial force of underwater steel pipe piles.

[0004] The technical solution adopted by this invention to solve its technical problem is: an underwater non-destructive testing device for axial force of steel pipe piles, comprising: a magnetic induction coil array, a signal excitation module, a magnetic field monitoring and modulation module, an underwater wireless transmission unit, and a back-end data processing unit; the underwater non-destructive testing device for axial force of steel pipe piles is set in the water environment surrounding the outer wall of the steel pipe pile and the steel structure; the magnetic induction coil array is arranged circumferentially along the outer wall of the steel pipe pile to form a closed magnetic field monitoring array, used to sense changes in the internal magnetic field of the steel pipe pile in real time; the signal excitation module is used to generate periodic excitation signals to form a background magnetic field around the steel pipe pile; the magnetic field monitoring and modulation module is used to identify changes in the magnetic field and convert them into voltage signals; the underwater wireless transmission unit transmits the modulated voltage signal from underwater to a receiving end located on the water surface or shore; the back-end data processing unit is installed on a hoisting control platform on shore, used to calculate the stress distribution of the steel pipe pile based on changes in the magnetic field at multiple points, and output the axial force time history, stress distribution, and abnormal early warning information of the steel pipe pile.

[0005] The underwater non-destructive testing device for axial force of steel pipe piles of the present invention includes a magnetic induction coil array, a signal excitation module, a magnetic field monitoring and modulation module, an underwater wireless transmission unit, and a back-end data processing unit. It is integrated into the aquatic environment surrounding the outer wall of the steel pipe pile and the steel structure. Under external loads, the steel pipe pile generates axial pressure or tension, causing a slight change in the internal magnetic permeability. The magnetic induction coil array, circumferentially arranged on the outer wall of the steel pipe pile, captures the local drift in magnetic flux density. After modulation by the magnetic field monitoring and modulation module, transmission by the underwater wireless transmission unit, and processing by the back-end data processing unit's inversion algorithm, the stress state of the steel pipe pile is obtained, thereby achieving real-time, accurate, and non-contact measurement of the axial force state of the steel pipe pile. Compared with traditional pile foundation axial force testing methods, the present invention has the following significant advantages:

[0006] 1. The circumferential closed magnetic field monitoring array formed by the magnetic induction coil array realizes multi-dimensional magnetic field capture, which can effectively invert the three-dimensional stress field distribution and realize indirect and accurate global perspective of the internal mechanical state of steel pipe piles;

[0007] 2. Based on the signal excitation design of stress permeability effect, the internal stress of steel pipe piles can be sensed from a distance in the form of magnetic field changes, realizing non-destructive monitoring across water bodies.

[0008] 3. Real-time monitoring and remote transmission of axial force in steel pipe piles were achieved through a multi-coil magnetic flux inversion algorithm, which improved the real-time performance and intelligence of axial force monitoring in steel pipe piles.

[0009] 4. It eliminates the need to install strain gauges, fiber optic sensors, or strain plates on the surface of steel pipe piles, enabling non-contact axial force detection of steel pipe piles. It also eliminates the need for waterproofing the sensors and avoids disturbance to the structure, overcoming the problems of traditional contact sensors being difficult to deploy and prone to failure in deep water environments.

[0010] 5. The axial force non-destructive testing device can be integrated with the structural health monitoring system to achieve synchronous measurement of pile groups or multiple points, and has strong scalability;

[0011] This invention improves the accuracy and reliability of axial force monitoring for underwater steel pipe piles, enabling long-term online monitoring and intelligent early warning. It can be widely applied in underwater foundation pits, bridge piers, wharves, and offshore wind power projects. It is also suitable for monitoring pile foundation stress in complex environments such as deep water, high sediment, and high salinity, demonstrating broad engineering application prospects.

[0012] Furthermore, the magnetic induction coil array is arranged on the outer wall of the steel pipe pile in an evenly distributed manner at equal angles, and a highly insulating waterproof coating is provided between the magnetic induction coil and the outer wall of the steel pipe pile.

[0013] Furthermore, the magnetic induction coil maintains a 3-10mm gap with the steel pipe pile through a highly insulating and waterproof coating.

[0014] Furthermore, the signal excitation module consists of a low-frequency magnetic excitation source, a driving circuit, and a frequency stabilization unit. The low-frequency magnetic excitation source generates a periodic excitation signal, forming a background magnetic field around the steel pipe pile. When compressive or tensile stress is generated inside the steel pipe pile, its magnetic permeability changes, altering the local distribution of the background magnetic field.

[0015] Furthermore, the magnetic field monitoring and modulation module includes a magnetic flux coupling unit, a low-noise differential amplifier, a phase-locked modulation unit, and a magnetoelectric sensor. The magnetic flux density change sensed by the magnetic induction coil array is output as a microvolt-level signal. The low-noise differential amplifier suppresses environmental noise and underwater stray magnetic fields. The phase-locked modulation unit uses the excitation signal as a reference to synchronously demodulate the target magnetic field disturbance signal, and converts it into a voltage signal after conversion by the magnetoelectric sensor for use by the back-end data processing unit.

[0016] Furthermore, the back-end data processing unit stores the structural health monitoring system, which consists of an embedded computing module and a magnetic field inversion algorithm library. The magnetic field inversion algorithm library has a built-in multi-coil magnetic flux inversion algorithm, which calculates the stress distribution of steel pipe piles through multi-point magnetic field changes and establishes a two-way mapping model of "magnetic field change-axial force". The structural health monitoring system automatically compensates for the magnetic differences of different steel pipe piles and outputs axial force time history, stress distribution and abnormal early warning information.

[0017] Furthermore, the underwater wireless transmission unit includes a transmitter that integrates a water pressure-resistant sealed chamber, a power supply voltage regulator, and a signal synchronization circuit, as well as a receiver located on the water surface or shore. The transmitter performs non-contact underwater transmission via low-frequency electromagnetic waves, and the receiver receives multi-node data over long distances.

[0018] In addition, the present invention also provides a method for non-destructive testing of axial force of underwater steel pipe piles, the steps of which are as follows:

[0019] S1: The underwater steel pipe pile axial force non-destructive testing device is set in the water environment around the outer wall of the steel pipe pile and the steel structure. The signal excitation module is turned on to apply a stable low-frequency background magnetic field to the magnetic induction coil array. The structural health monitoring system of the back-end data processing unit enters the initial steady state. The structural health monitoring system automatically performs environmental calibration and establishes the initial magnetic field baseline.

[0020] S2: When the underwater steel pipe pile is subjected to force, the change in its internal magnetic permeability causes a change in the external magnetic flux density. The magnetic induction coil array synchronously collects data from each circumferential coil to sense the change in the external magnetic field of the steel pipe pile in real time. The magnetic field monitoring and modulation module identifies the magnetic field change and converts it into a voltage signal. The structural health monitoring system compares the initial magnetic field baseline and generates a magnetic field disturbance spectrum in real time.

[0021] S3: The modulated voltage signal is transmitted underwater via the underwater wireless transmission unit to the receiving end located on the water surface or shore.

[0022] S4: The back-end data processing unit calculates the internal stress distribution of the steel pipe pile based on the changes in the magnetic field at multiple points and calls the multi-coil magnetic flux inversion algorithm. It uses the magnetic permeability sensing mechanism to calculate the axial stress and outputs real-time displacement trend, stress change and abnormal alarm information.

[0023] The underwater non-destructive testing method for axial force of steel pipe piles of the present invention firstly involves setting up an underwater non-destructive testing device for axial force of steel pipe piles in the water environment surrounding the outer wall of the steel pipe pile and the steel structure. A signal excitation module applies a stable low-frequency background magnetic field to the area around the magnetic induction coil array. The structural health monitoring system establishes an initial magnetic field baseline. Each circumferential coil of the magnetic induction coil array synchronously senses changes in the external magnetic field of the steel pipe pile in real time. The magnetic field monitoring and modulation module identifies the magnetic field changes and converts them into voltage signals. The structural health monitoring system compares the initial magnetic field baseline and generates a magnetic field disturbance spectrum in real time. The modulated voltage signal is transmitted underwater to a receiving end located on the water surface or shore via an underwater wireless transmission unit. The back-end data processing unit calculates the internal stress distribution of the steel pipe pile based on the changes in the magnetic field at multiple points and calls a multi-coil magnetic flux inversion algorithm. It uses a permeability-sensitive mechanism to estimate the axial stress and outputs real-time displacement trends, stress changes, and abnormal alarm information. This non-destructive testing method is based on signal excitation design using the stress permeability effect, enabling the internal stress of steel pipe piles to be sensed remotely in the form of magnetic field changes, achieving non-destructive monitoring across water bodies. Three-dimensional differential magnetic field observation is achieved through multiple circumferentially arranged magnetic induction coil arrays, eliminating the reliance on single-point measurements for stress distribution analysis. Real-time monitoring and remote transmission of axial force in the steel pipe pile are realized through a multi-coil magnetic flux inversion algorithm, improving the real-time performance and intelligence of axial force monitoring. A fusion algorithm combining machine learning and multi-point electromagnetic field inversion improves the structural health monitoring system's identification accuracy by 3 to 10 times compared to single-coil measurements.

[0024] Furthermore, in step S2, the output signal of the magnetic induction coil array enters the differential front-end amplifier of the magnetic field monitoring and modulation module to suppress symmetry error. The low-noise differential amplifier is used to suppress environmental noise and underwater stray magnetic fields.

[0025] Furthermore, in step S1, the structural health monitoring system is equipped with a periodic self-calibration mode, which automatically refreshes the initial magnetic field baseline after each water level change or construction phase switch; in step S4, the structural health monitoring system automatically adjusts the transmission power to adapt to changes in water depth and water quality, and the receiving end of the back-end data processing unit automatically performs real-time synchronous demodulation and error correction. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an embodiment of the underwater steel pipe pile axial force non-destructive testing device of the present invention;

[0027] Figure 2 This is a curve showing the relationship between magnetic flux change and axial force in one embodiment of the present invention.

[0028] The numbers in the diagram are as follows:

[0029] 1. Steel pipe pile; 11. Magnetic induction coil array; 12. High insulation and waterproof coating; 14. Underwater wireless transmission unit; 15. Signal excitation module; 16. Magnetic field monitoring and modulation module; 17. Back-end data processing unit. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the embodiments of the present invention. For ease of description, the terms "upper" and "lower" used below are consistent with the upper and lower directions in the drawings, but this should not be construed as a limitation of the technical solution of the present invention.

[0031] Combination Figure 1 and Figure 2 The underwater steel pipe pile axial force non-destructive testing device of the present invention includes: a magnetic induction coil array 11, a signal excitation module 15, a magnetic field monitoring and modulation module 16, an underwater wireless transmission unit 14, and a back-end data processing unit 17. The underwater steel pipe pile axial force non-destructive testing device is integrated into the water environment surrounding the outer wall of the steel pipe pile 1 and the steel structure, realizing non-contact, real-time monitoring of the stress state of the underwater steel pipe pile 1. The magnetic induction coil array 11 is arranged circumferentially along the outer wall of the steel pipe pile 1 to form a closed magnetic field monitoring array for real-time sensing of the steel... The magnetic field inside the steel pipe pile 1 changes; the signal excitation module 15 is used to generate periodic excitation signals to form a background magnetic field around the steel pipe pile 1; the magnetic field monitoring and modulation module 16 is used to identify the magnetic field changes and convert them into voltage signals; the underwater wireless transmission unit 14 transmits the modulated voltage signals from underwater to the receiving end located on the water surface or shore; the back-end data processing unit 17 is installed on the shore pile control platform to calculate the stress distribution of the steel pipe pile 1 based on the changes in the magnetic field at multiple points, and outputs the axial force time history, stress distribution and abnormal warning information of the steel pipe pile 1.

[0032] The underwater non-destructive testing device for axial force of steel pipe piles of the present invention includes a magnetic induction coil array 11, a signal excitation module 15, a magnetic field monitoring and modulation module 16, an underwater wireless transmission unit 14, and a back-end data processing unit 17. It is integrated into the aquatic environment surrounding the outer wall of the steel pipe pile 1 and the steel structure. Under external load, the steel pipe pile 1 generates axial pressure or tension, causing a slight change in the internal magnetic permeability. The magnetic induction coil array 11, circumferentially arranged on the outer wall of the steel pipe pile 1, captures the local drift in magnetic flux density. After modulation by the magnetic field monitoring and modulation module 16, transmission by the underwater wireless transmission unit 14, and processing by the inversion algorithm of the back-end data processing unit 17, the stress state of the steel pipe pile 1 is obtained, thereby achieving real-time, accurate, and non-contact measurement of the axial force state of the steel pipe pile 1. Compared with traditional pile foundation axial force testing methods, the present invention has the following significant advantages:

[0033] 4. The circumferential closed magnetic field monitoring array formed by the magnetic induction coil array 11 realizes multi-dimensional magnetic field capture, which can effectively invert the three-dimensional stress field distribution and realize indirect and accurate global perspective of the internal mechanical state of the steel pipe pile 1.

[0034] 5. Based on the signal excitation design of stress permeability effect, the internal stress of steel pipe pile 1 can be sensed from a distance in the form of magnetic field change, realizing non-destructive monitoring across water bodies.

[0035] 6. Real-time monitoring and remote transmission of axial force of steel pipe pile 1 were realized through multi-coil magnetic flux inversion algorithm, which improved the real-time performance and intelligence of axial force monitoring of steel pipe pile 1;

[0036] 4. There is no need to install strain gauges, fiber optic sensors or strain plates on the surface of steel pipe pile 1, which realizes non-contact axial force detection of steel pipe pile 1. There is no need to take waterproof measures for the sensor, and it avoids disturbance to the structure. It overcomes the problems of traditional contact sensors being difficult to deploy and prone to failure in deep water environment.

[0037] 5. The axial force non-destructive testing device can be integrated with the structural health monitoring system to achieve synchronous measurement of pile groups or multiple points, and has strong scalability;

[0038] This invention improves the accuracy and reliability of axial force monitoring for underwater steel pipe piles, enabling long-term online monitoring and intelligent early warning. It can be widely applied in underwater foundation pits, bridge piers, wharves, and offshore wind power projects. It is also suitable for monitoring pile foundation stress in complex environments such as deep water, high sediment, and high salinity, demonstrating broad engineering application prospects.

[0039] like Figure 1As shown, the magnetic induction coil array 11 is arranged on the outer wall of the steel pipe pile 1 in a uniformly distributed manner at equal angles (such as 4, 8, or 16 coils), and a highly insulating and waterproof coating 12 is provided between the magnetic induction coils and the outer wall of the steel pipe pile. The non-contact isolation design between the magnetic induction coil array 11 and the steel pipe pile 1 improves the stability and durability of the axial force non-destructive testing device.

[0040] The magnetic induction coil is separated from the steel pipe pile 1 by a 3-10mm gap through a highly insulating and waterproof coating 12. The magnetic induction coil does not directly contact the outer wall of the steel pipe pile 1, avoiding electromagnetic short circuits and mechanical wear. The magnetic induction coil is wound with corrosion-resistant copper wire or tin-plated copper wire and coated with a marine-grade epoxy coating, allowing it to be submerged in underwater environments for extended periods. This ensures a stable electromagnetic transmission channel between the magnetic induction coil array 11 and the water body, guaranteeing stable induction of magnetic field changes.

[0041] like Figure 1 As shown, the signal excitation module 15 consists of a low-frequency magnetic excitation source, a drive circuit, and a frequency stabilization unit. The low-frequency magnetic excitation source generates a periodic excitation signal in the range of 10Hz to 1kHz, forming a stable background magnetic field around the steel pipe pile 1. The constant amplitude frequency stabilization technology is adopted to ensure that the background magnetic field will not drift due to silt, conductivity, or temperature fluctuations in the underwater environment. When compressive or tensile stress is generated in the steel pipe pile 1, its magnetic permeability (μ) changes slightly, thereby changing the local distribution of the background magnetic field.

[0042] like Figure 1 As shown, the magnetic field monitoring and modulation module 16 includes a magnetic flux coupling unit, a low-noise differential amplifier, a phase-locked modulation unit, and a high-sensitivity magnetoelectric sensor. The magnetic flux coupling unit gathers, guides, and concentrates the weak magnetic flux disturbances caused by stress changes in the target area into the effective sensing area of ​​the magnetic induction coil array 11. The magnetic flux density changes sensed by the magnetic induction coil array 11 are output as microvolt-level signals. The low-noise differential amplifier suppresses environmental noise and underwater stray magnetic fields. The phase-locked modulation unit uses the excitation signal as a reference to synchronously demodulate the target magnetic field disturbance signal, which is then converted into a voltage signal by the magnetoelectric sensor for use by the back-end data processing unit 17. By employing underwater weak magnetic field disturbance extraction technology, the magnetic flux changes caused by weak stress changes within the steel pipe pile 1 can be accurately identified even under strong background noise. The differential + phase-locked dual modulation method greatly improves the signal-to-noise ratio.

[0043] like Figure 1As shown, the backend data processing unit 17 stores a structural health monitoring system, which consists of an embedded computing module and a magnetic field inversion algorithm library. The magnetic field inversion algorithm library includes a multi-coil magnetic flux inversion algorithm, which calculates the stress distribution of the steel pipe pile 1 through multi-point magnetic field changes and establishes a two-way mapping model of "magnetic field change-axial force." This two-way mapping model can be trained using a BP neural network, radial basis function network, or finite element method. The stress-permeability curve is obtained through calibration experiments. The structural health monitoring system automatically compensates for the magnetic differences among different steel pipe piles 1. Data is refreshed in real time at 10–100 Hz, and finally, the system outputs the axial force time history, stress distribution, and anomaly warning information. This invention utilizes underwater inversion technology to reconstruct the stress state of the pile body using multi-point magnetic flux distribution, achieving completely non-contact, full life-cycle monitoring, and providing a new structural health monitoring mode for deep foundation pit underwater steel pipe piles 1.

[0044] like Figure 1 As shown, the underwater wireless transmission unit 14 includes a transmitter integrating a water pressure-resistant sealed chamber, a power supply voltage regulator, and a signal synchronization circuit, as well as a receiver located on the water surface or shore. The transmitter uses low-frequency electromagnetic waves for non-contact underwater transmission, eliminating the need for cable connections. The low-frequency electromagnetic wave pulses can propagate stably in highly turbid and saline waters, avoiding the unreliability of optical and underwater acoustic communications. Data is coded for error correction before transmission, enhancing its resistance to attenuation. Using underwater low-frequency electromagnetic communication instead of traditional wired communication significantly improves the deployability and security of the structural health monitoring system. The receiver uses a signal acquisition instrument, enabling long-distance reception of data from multiple nodes. The underwater wireless transmission unit 14 achieves "wireless" underwater deployment, overcoming the limitations of traditional underwater monitoring's heavy reliance on wired transmission and significantly reducing construction risks and costs.

[0045] Combination Figure 1 and Figure 2 The method for non-destructive testing of axial force in underwater steel pipe piles according to the present invention includes the following specific steps:

[0046] S1. Establishing Background Magnetic Field Excitation: The underwater steel pipe pile axial force non-destructive testing device is set in the water environment around the outer wall of the steel pipe pile 1 and the steel structure. The signal excitation module 15 is turned on to apply a stable low-frequency background magnetic field around the magnetic induction coil array 11. The structural health monitoring system of the back-end data processing unit 17 enters the initial steady state. The structural health monitoring system automatically performs environmental calibration, including water conductivity background measurement, environmental magnetic noise modeling, etc., and establishes the initial magnetic field equipotential line distribution as the initial magnetic field baseline of the "stress-free state". The environmental calibration mechanism ensures that the structural health monitoring system can operate automatically and stably in underwater construction, varying water depth and turbidity environments.

[0047] S2. Magnetic induction coil array 11 collects magnetic flux changes in real time: After the underwater steel pipe pile 1 is subjected to force, the change in its internal magnetic permeability causes the change in external magnetic flux density. Each circumferential coil of the magnetic induction coil array 11 collects data synchronously and senses the change in the external magnetic field of the steel pipe pile 1 in real time. The magnetic field monitoring and modulation module 16 identifies the magnetic field change and converts it into a voltage signal. The structural health monitoring system compares the initial magnetic field baseline and generates a magnetic field disturbance spectrum in real time.

[0048] S3, Underwater wireless signal transmission: The modulated voltage signal is transmitted underwater to the receiving end located on the water surface or shore via the underwater wireless transmission unit 14.

[0049] S4. Data Inversion and Stress Calculation: The back-end data processing unit 17 calculates the internal stress distribution of the steel pipe pile 1 based on the changes in the magnetic field at multiple points and by calling the multi-coil magnetic flux inversion algorithm. It uses the magnetic permeability sensing mechanism to calculate the axial stress and outputs real-time displacement trend, stress change and abnormal alarm information.

[0050] The underwater non-destructive testing method for axial force of steel pipe piles of the present invention firstly involves setting up an underwater non-destructive testing device for axial force of steel pipe piles in the water environment surrounding the outer wall of the steel pipe pile 1 and the steel structure. The signal excitation module 15 applies a stable low-frequency background magnetic field to the magnetic induction coil array 11. The structural health monitoring system establishes an initial magnetic field baseline. Each circumferential coil of the magnetic induction coil array 11 synchronously senses the changes in the external magnetic field of the steel pipe pile 1 in real time. The magnetic field monitoring and modulation module 16 identifies the changes in the magnetic field and converts them into voltage signals. The structural health monitoring system compares the initial magnetic field baseline and generates a magnetic field disturbance spectrum in real time. The modulated voltage signal is transmitted underwater to a receiving end located on the water surface or shore via the underwater wireless transmission unit 14. The back-end data processing unit 17 calculates the internal stress distribution of the steel pipe pile 1 based on the changes in the magnetic field at multiple points and calls the multi-coil magnetic flux inversion algorithm. It uses the permeability sensitivity mechanism to estimate the axial stress and outputs real-time displacement trend, stress change, and abnormal alarm information. This non-destructive testing method is based on the signal excitation design of the stress permeability effect, which enables the internal stress of the steel pipe pile 1 to be sensed remotely in the form of magnetic field changes, realizing non-destructive monitoring across water bodies; three-dimensional magnetic field differential observation is realized through multiple circumferentially arranged magnetic induction coil arrays 11, so that stress distribution analysis no longer depends on single-point measurement; real-time monitoring and remote transmission of the axial force of the steel pipe pile 1 are realized through the multi-coil magnetic flux inversion algorithm, improving the real-time performance and intelligence of the axial force monitoring of the steel pipe pile 1; the fusion algorithm composed of machine learning and multi-point electromagnetic field inversion improves the identification accuracy of the structural health monitoring system by 3 to 10 times compared with single-coil measurement.

[0051] In step S2, the output signal of the magnetic induction coil array 11 enters the differential front-end amplifier of the magnetic field monitoring and modulation module 16 to suppress left and right symmetry errors. The low-noise differential amplifier is used to suppress environmental noise and underwater stray magnetic fields.

[0052] In steps S2 and S3, the structural health monitoring system automatically adjusts the transmission power to adapt to changes in water depth and water quality, and the receiving end of the back-end data processing unit 17 automatically performs real-time synchronous demodulation and error correction.

[0053] Step S1 further includes long-term operation and self-calibration maintenance. The structural health monitoring system has a periodic self-calibration mode, which automatically refreshes the initial magnetic field baseline after each water level change or construction phase switch. It can monitor the stress change trend of steel pipe pile 1 over a long period of time, providing closed-loop control data for construction safety. The underwater magnetic field monitoring mode of "self-calibration + self-learning" significantly reduces maintenance requirements and is especially suitable for long-term immersion environments.

[0054] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the claims.

Claims

1. A non-destructive testing device for axial force of underwater steel pipe piles, characterized in that, It includes: The system includes a magnetic induction coil array, a signal excitation module, a magnetic field monitoring and modulation module, an underwater wireless transmission unit, and a back-end data processing unit. The underwater steel pipe pile axial force non-destructive testing device is set in the water environment around the outer wall of the steel pipe pile and the steel structure. The magnetic induction coil array is arranged circumferentially along the outer wall of the steel pipe pile to form a closed magnetic field monitoring array, which is used to sense the changes in the magnetic field inside the steel pipe pile in real time. The signal excitation module is used to generate periodic excitation signals to form a background magnetic field around the steel pipe pile. The magnetic field monitoring and modulation module is used to identify the changes in the magnetic field and convert them into voltage signals. The underwater wireless transmission unit transmits the modulated voltage signal from underwater to the receiving end located on the water surface or shore. The back-end data processing unit is installed on the shore pile control platform to calculate the stress distribution of the steel pipe pile based on the changes in the magnetic field at multiple points, and outputs the axial force time history, stress distribution and abnormal early warning information of the steel pipe pile.

2. The underwater steel pipe pile axial force non-destructive testing device according to claim 1, characterized in that: The magnetic induction coil array is arranged on the outer wall of the steel pipe pile in an evenly distributed manner at equal angles, and a highly insulating and waterproof coating is provided between the magnetic induction coil and the outer wall of the steel pipe pile.

3. The underwater steel pipe pile axial force non-destructive testing device according to claim 2, characterized in that: The magnetic induction coil is separated from the steel pipe pile by a 3-10 mm gap through a highly insulating and waterproof coating.

4. The underwater steel pipe pile axial force non-destructive testing device according to claim 1, characterized in that: The signal excitation module consists of a low-frequency magnetic excitation source, a driving circuit, and a frequency stabilization unit. The low-frequency magnetic excitation source generates a periodic excitation signal, forming a background magnetic field around the steel pipe pile. When compressive or tensile stress is generated inside the steel pipe pile, its magnetic permeability changes, altering the local distribution of the background magnetic field.

5. The underwater steel pipe pile axial force non-destructive testing device according to claim 1, characterized in that: The magnetic field monitoring and modulation module includes a magnetic flux coupling unit, a low-noise differential amplifier, a phase-locked modulation unit, and a magnetoelectric sensor. The magnetic flux density change sensed by the magnetic induction coil array is output as a microvolt-level signal. The low-noise differential amplifier suppresses environmental noise and underwater stray magnetic fields. The phase-locked modulation unit uses the excitation signal as a reference to synchronously demodulate the target magnetic field disturbance signal, and converts it into a voltage signal after conversion by the magnetoelectric sensor for use by the back-end data processing unit.

6. The underwater steel pipe pile axial force non-destructive testing device according to claim 1, characterized in that: The back-end data processing unit stores the structural health monitoring system, which consists of an embedded computing module and a magnetic field inversion algorithm library. The magnetic field inversion algorithm library has a built-in multi-coil magnetic flux inversion algorithm, which calculates the stress distribution of steel pipe piles through multi-point magnetic field changes and establishes a two-way mapping model of "magnetic field change-axial force". The structural health monitoring system automatically compensates for the magnetic differences of different steel pipe piles and outputs axial force time history, stress distribution and abnormal early warning information.

7. The underwater steel pipe pile axial force non-destructive testing device according to claim 1, characterized in that: The underwater wireless transmission unit includes a transmitter that integrates a water pressure-resistant sealed chamber, a power supply voltage regulator, and a signal synchronization circuit, as well as a receiver located on the water surface or shore. The transmitter performs non-contact underwater transmission via low-frequency electromagnetic waves, and the receiver receives data from multiple nodes over a long distance.

8. A non-destructive testing method for axial force of underwater steel pipe piles, characterized in that, The steps are as follows: S1: The underwater steel pipe pile axial force non-destructive testing device is set in the water environment around the outer wall of the steel pipe pile and the steel structure. The signal excitation module is turned on to apply a stable low-frequency background magnetic field to the magnetic induction coil array. The structural health monitoring system of the back-end data processing unit enters the initial steady state. The structural health monitoring system automatically performs environmental calibration and establishes the initial magnetic field baseline. S2: When the underwater steel pipe pile is subjected to force, the change in its internal magnetic permeability causes a change in the external magnetic flux density. The magnetic induction coil array synchronously collects data from each circumferential coil to sense the change in the external magnetic field of the steel pipe pile in real time. The magnetic field monitoring and modulation module identifies the magnetic field change and converts it into a voltage signal. The structural health monitoring system compares the initial magnetic field baseline and generates a magnetic field disturbance spectrum in real time. S3: The modulated voltage signal is transmitted underwater via the underwater wireless transmission unit to the receiving end located on the water surface or shore. S4: The back-end data processing unit calculates the internal stress distribution of the steel pipe pile based on the changes in the magnetic field at multiple points and calls the multi-coil magnetic flux inversion algorithm. It uses the magnetic permeability sensing mechanism to calculate the axial stress and outputs real-time displacement trend, stress change and abnormal alarm information.

9. The method for non-destructive testing of axial force in underwater steel pipe piles according to claim 8, characterized in that: In step S2, the output signal of the magnetic induction coil array enters the differential front-end amplifier of the magnetic field monitoring and modulation module to suppress symmetry error. The low-noise differential amplifier is used to suppress environmental noise and underwater stray magnetic fields.

10. The method for non-destructive testing of axial force in underwater steel pipe piles according to claim 8, characterized in that: In step S1, the structural health monitoring system is equipped with a periodic self-calibration mode, which automatically refreshes the initial magnetic field baseline after each water level change or construction phase switch; in step S4, the structural health monitoring system automatically adjusts the transmission power to adapt to changes in water depth and water quality, and the receiving end of the back-end data processing unit automatically performs real-time synchronous demodulation and error correction.

Images