Concrete dam active crack electromagnetic signal acquisition device and method

Abstract

The application discloses a kind of concrete dam active crack electromagnetic signal acquisition device and method, wherein the device includes: three-axis electromagnetic monitoring sensor, electromagnetic signal correction unit, electromagnetic signal conditioning unit, intelligent control unit and power supply unit;Three-axis electromagnetic monitoring sensor is used to obtain the spatial magnetic field data of concrete dam body surface, electromagnetic signal correction unit is used to eliminate concrete dam background noise, electromagnetic signal conditioning unit is used to convert electromagnetic analog signal collected by three-axis electromagnetic monitoring sensor into electromagnetic digital signal, intelligent control unit is used to identify and store the electromagnetic signal generated by active crack of concrete dam, and power supply unit is used to provide required voltage and current for normal operation of three-axis electromagnetic monitoring sensor, electromagnetic signal correction unit, electromagnetic signal conditioning unit and intelligent control unit.The application can realize the collection of concrete dam active crack electromagnetic signal, and the collection area is more extensive, and the device power consumption is low.

Description

Technical Field

[0001] This invention relates to the field of online electromagnetic signal acquisition technology, and in particular to an electromagnetic signal acquisition device and method for active cracks in concrete dams. Background Technology

[0002] As large-volume concrete structures, concrete dams have a tensile strength far lower than their compressive strength, making them prone to active cracking. Furthermore, dams must withstand water pressure and seismic forces reaching tens of millions of tons. Under the combined action of dynamic and static cracks, these cracks easily propagate, threatening the dam's safety and stability. However, because concrete dams bear the immense pressure of reservoir water in hydropower stations and are constantly under stress, direct observation from the reservoir side is difficult. The high frequency and low amplitude of electromagnetic signals generated by active cracks make the acquisition of these signals a persistent challenge in nondestructive testing. Therefore, the acquisition of electromagnetic signals from active cracks in concrete dams is of great significance.

[0003] However, there is currently no mature electromagnetic signal acquisition device for large-scale active concrete cracks in the world. Manual inspection consumes a lot of manpower and material resources, but can only periodically assess crack defects in dams, making it difficult to determine the state of crack defects in real time; conventional electromagnetic signal acquisition devices have low sampling frequencies, making it impossible to record the complete waveform of active crack signals in concrete dams; and electromagnetic radiation monitoring devices used in mines can only identify the characteristics of electromagnetic radiation signals in mines or coal seams, making it difficult to identify and record electromagnetic signals of active cracks on concrete dams. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, this invention proposes an electromagnetic signal acquisition device for active cracks in concrete dams. This device utilizes a triaxial electromagnetic monitoring sensor and related signal conditioning modules to identify electromagnetic signals generated by active cracks, providing a basis for monitoring changes in active cracks in concrete dams and offering technical support for the safe operation of dams.

[0006] Another objective of this invention is to propose a method for acquiring electromagnetic signals of active cracks in concrete dams.

[0007] To achieve the above objectives, the present invention proposes an electromagnetic signal acquisition device for active cracks in concrete dams, comprising: a triaxial electromagnetic monitoring sensor (1), an electromagnetic signal correction unit (2), an electromagnetic signal conditioning unit (3), an intelligent control unit (4), and a power supply unit (5).

[0008] The triaxial electromagnetic monitoring sensor (1) is used to acquire spatial three-dimensional magnetic field data of the surface of the concrete dam body;

[0009] The electromagnetic signal correction unit (2) includes a differential circuit (21) and a notch filter circuit (22) for removing electromagnetic background noise from the electromagnetic radiation signal generated by the active cracks in the concrete dam.

[0010] The electromagnetic signal conditioning unit (3) includes a first-stage amplifier circuit (31), a low-pass filter circuit (32), a second-stage amplifier circuit (33), a band-pass filter circuit (34), and an analog-to-digital converter circuit (35), which is connected to the triaxial electromagnetic monitoring sensor (1) and is used to convert the electromagnetic analog signal collected by the triaxial electromagnetic monitoring sensor (1) into an electromagnetic digital signal.

[0011] The intelligent control unit (4) includes a signal temporary storage module (41), a signal comparison module (42), a signal feature extraction module (43), and a signal storage module (44), which are connected to the electromagnetic signal conditioning unit (3) and are used to identify and store electromagnetic signals generated by active cracks in concrete dams.

[0012] The power supply unit includes a power supply battery (51), a power protection circuit (52), a power conversion circuit (53), and a power filtering circuit (54), which are connected to the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4) to provide the required voltage and current for the normal operation of the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4).

[0013] Optionally, the sampling rate of the electromagnetic signal of the triaxial electromagnetic monitoring sensor (1) is greater than 10MHz, and the minimum scale value of the electromagnetic signal is less than 10nT.

[0014] Optionally, the differential circuit (21) is used to compare the difference between the triaxial electromagnetic analog signal and the background noise of the concrete dam in order to filter out low-frequency electromagnetic signals.

[0015] The notch filter circuit (22) is used to remove background noise of a preset frequency from the triaxial electromagnetic analog signal;

[0016] The first-stage amplifier circuit (31) is a low-gain, low-noise voltage amplifier circuit with noise levels below 5nV / √Hz and a voltage amplification factor not exceeding 20.

[0017] The low-pass filter circuit (32) is used to filter out low-frequency interference electromagnetic signals with a frequency below 100Hz;

[0018] The secondary amplifier circuit (33) is a high-gain, high-speed voltage amplifier circuit with a gain-bandwidth product greater than 2GHz and a voltage amplification factor of not less than 200.

[0019] The bandpass filter circuit (34) is used to filter out interfering electromagnetic signals with frequencies below 10kHz and above 10MHz;

[0020] The sampling resolution of the analog-to-digital converter circuit (35) is not less than 16 bits, and the data conversion rate is not less than 50MHz.

[0021] Optionally, the signal temporary storage module (41) is used to temporarily record the waveform of the triaxial electromagnetic digital signal, and the duration of a single recorded electromagnetic signal is greater than 2ms.

[0022] The signal comparison module (42) is used to compare the differences between the waveforms of the three-axis electromagnetic digital signals and eliminate interference noise inside the electromagnetic signal acquisition device.

[0023] The signal feature extraction module (43) is used to distinguish between electromagnetic signals of active cracks in concrete dams and environmental interference signals and interference noise inside the electromagnetic signal sampling unit.

[0024] The signal storage module (44) is connected to the signal feature extraction module (43) and is used to store electromagnetic signals of active cracks in concrete dams. The duration of the electromagnetic signal generated by a single active crack is greater than 2ms.

[0025] Optionally, the power supply battery (51) is powered by a combination of a high-energy-density lithium battery pack and a solar panel;

[0026] The power protection circuit (52) is used to protect the power supply battery from overvoltage and overcurrent.

[0027] The power conversion circuit (53) is used to convert the power supply voltage of the power supply battery into the power supply voltage corresponding to the triaxial electromagnetic monitoring sensor, electromagnetic signal acquisition unit and intelligent control unit;

[0028] The power supply filter circuit (54) is used to filter out the non-DC component in the power supply voltage.

[0029] To achieve the above objectives, a second aspect of the present invention provides a method for acquiring electromagnetic signals of active cracks in concrete dams, applied to the electromagnetic signal acquisition device for active cracks in concrete dams described in the first aspect of the present invention, comprising the following steps:

[0030] Based on the distribution pattern of active cracks in concrete dams, areas where active crack signals need to be collected are selected. Triaxial electromagnetic monitoring sensors are installed on the concrete dam body, and combined with supporting electromagnetic signal correction units, electromagnetic signal conditioning units, intelligent control units and power supply units, triaxial electromagnetic signals of the concrete dam body containing background noise are collected and stored.

[0031] When active cracks in the concrete dam body propagate, the generated electromagnetic signal is converted into a triaxial electromagnetic analog signal by a triaxial electromagnetic monitoring sensor. Compared with electromagnetic background noise, the triaxial electromagnetic analog signal is amplified, filtered, and converted from analog to digital by an electromagnetic signal conditioning unit, and then converted into a triaxial electromagnetic digital signal and sent to the intelligent control unit.

[0032] The signal comparison module of the intelligent control unit combines the frequency and amplitude differences of the triaxial electromagnetic digital signals to eliminate internal interference noise.

[0033] The signal feature extraction module of the intelligent control unit combines the time-domain characteristics of the triaxial electromagnetic digital signal to identify the electromagnetic signal generated by the active crack in the concrete dam, and transmits the identified electromagnetic signal to the signal storage module.

[0034] Optionally, the selected areas for active crack sampling include: areas of the concrete dam that bear a high proportion of the load, areas that are prone to cracks during routine inspections, and areas that have developed micro-cracks but have not yet developed into serious cracks.

[0035] Optionally, the triaxial electromagnetic analog signal includes: x, y, z three-axis magnetic field components collected by the triaxial electromagnetic monitoring sensor (1) in the spatial radiation field of the acquisition area, the three axes being perpendicular to each other.

[0036] Optionally, the combination of frequency and amplitude differences of the three-axis electromagnetic digital signal includes: when the three-axis electromagnetic digital signal received by the intelligent control unit (4) is not simultaneously recognized, the main frequency of the three-axis electromagnetic digital signal is inconsistent, or the main frequency of the three-axis electromagnetic digital signal is outside the range of 10kHz-10MHz, the three-axis electromagnetic digital signal is environmental interference noise.

[0037] Optionally, the combination of the time-domain characteristics of the triaxial electromagnetic digital signal includes: when the triaxial electromagnetic digital signal received by the intelligent control unit (4) is a pulse oscillation attenuation signal, and the signal rise time is less than 0.5ms and the attenuation time is less than 1.5ms, the received triaxial electromagnetic digital signal is an electromagnetic signal generated by active cracks in the concrete dam.

[0038] The electromagnetic signal acquisition device and method for active cracks in concrete dams according to embodiments of the present invention can extract electromagnetic signals generated by active cracks in concrete dams using a triaxial electromagnetic monitoring sensor, filter out spatial magnetic field interference signals with the help of an electromagnetic signal correction unit and a conditioning unit, and identify and store the electromagnetic signals generated by active cracks through an intelligent control unit. The acquisition device can acquire electromagnetic signals generated by active cracks inside concrete dams, with a wider acquisition area and higher reliability. The method has a simple solution model and good real-time performance. The device has low power consumption.

[0039] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0040] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0041] Figure 1 This is a schematic diagram of an electromagnetic signal acquisition device for active cracks in a concrete dam according to an embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the electromagnetic signal correction unit structure of an electromagnetic signal acquisition device for active cracks in a concrete dam according to an embodiment of the present invention.

[0043] Figure 3 A schematic diagram of the electromagnetic signal conditioning unit structure of an electromagnetic signal acquisition device for active cracks in a concrete dam according to an embodiment of the present invention.

[0044] Figure 4 A schematic diagram of the intelligent control unit of a concrete dam active crack electromagnetic signal acquisition device according to an embodiment of the present invention.

[0045] Figure 5 A schematic diagram of the power supply unit structure of an electromagnetic signal acquisition device for active cracks in a concrete dam according to an embodiment of the present invention.

[0046] Figure 6 This is a flowchart of a method for acquiring electromagnetic signals of active cracks in a concrete dam according to an embodiment of the present invention.

[0047] Figure 7 This is a waveform diagram of electromagnetic signal interference noise in an active crack of a concrete dam according to an embodiment of the present invention.

[0048] Figure 8 This is a waveform diagram of electromagnetic signals for active cracks in a concrete dam according to an embodiment of the present invention. Detailed Implementation

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0051] The electromagnetic signal acquisition device and method for active cracks in concrete dams according to embodiments of the present invention are described below with reference to the accompanying drawings.

[0052] Figure 1 This is a schematic diagram of the structure of the electromagnetic signal acquisition device for active cracks in a concrete dam according to an embodiment of the present invention.

[0053] like Figure 1 As shown, the device includes: a triaxial electromagnetic monitoring sensor (1), which is used to acquire spatial three-dimensional magnetic field data of the surface of the concrete dam.

[0054] Electromagnetic signal correction unit (2), the electromagnetic signal correction unit (2) includes a differential circuit (21) and a notch filter circuit (22), used to remove electromagnetic background noise in the electromagnetic radiation signal generated by active cracks in concrete dams;

[0055] The electromagnetic signal conditioning unit (3) includes a first-stage amplifier circuit (31), a low-pass filter circuit (32), a second-stage amplifier circuit (33), a band-pass filter circuit (34), and an analog-to-digital converter circuit (35), which is connected to the triaxial electromagnetic monitoring sensor (1) and is used to convert the electromagnetic analog signal collected by the triaxial electromagnetic monitoring sensor (1) into an electromagnetic digital signal.

[0056] The intelligent control unit (4) includes a signal temporary storage module (41), a signal comparison module (42), a signal feature extraction module (43), and a signal storage module (44), which are connected to the electromagnetic signal conditioning unit (3) and are used to identify and store electromagnetic signals generated by active cracks in concrete dams.

[0057] The power supply unit (5) includes a power supply battery (51), a power protection circuit (52), a power conversion circuit (53), and a power filtering circuit (54). It is connected to the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4) to provide the required voltage and current for the normal operation of the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4).

[0058] Furthermore, in one embodiment of the present invention, the sampling rate of the spatial electromagnetic signal of the triaxial electromagnetic monitoring sensor is not less than 10MHz, and the minimum resolution of the electromagnetic signal is less than 10nT.

[0059] Furthermore, in one embodiment of the present invention, the differential circuit compares the difference between the triaxial electromagnetic analog signal and the background noise of the concrete dam to filter out interference from low-frequency electromagnetic signals such as the geomagnetic field.

[0060] The notch filter circuit removes background noise from power line frequency and integer harmonic electromagnetic radiation in the triaxial electromagnetic analog signal.

[0061] The first-stage amplifier circuit is a low-gain, low-noise voltage amplifier circuit with a noise level of 5nV / √Hz and a voltage amplification factor of 20.

[0062] The low-pass filter circuit is used to filter out low-frequency interference electromagnetic signals with a frequency below 100Hz.

[0063] The secondary amplifier circuit is a high-gain, high-speed voltage amplifier circuit with a gain-bandwidth product of 2GHz and a voltage amplification factor of 200.

[0064] The bandpass filter circuit is used to filter out interfering electromagnetic signals with frequencies below 10kHz and above 10MHz;

[0065] The analog-to-digital converter circuit has a sampling resolution of 16 bits and a data conversion rate of 50MHz.

[0066] Furthermore, in one embodiment of the present invention, the power supply battery is powered by a combination of a high-energy-density lithium battery pack and a solar panel. When there is sufficient sunlight, the solar panel is used for power supply, and when there is insufficient sunlight, the high-energy-density lithium battery pack is used for power supply.

[0067] The power protection circuit is used to protect the power supply battery from overvoltage and overcurrent.

[0068] The power conversion circuit is used to convert the 12V power supply voltage of the power supply battery into the 5V, 3.3V, etc. power supply voltages corresponding to the triaxial electromagnetic monitoring sensor, electromagnetic signal acquisition unit, and intelligent control unit.

[0069] The power supply filtering circuit is used to filter out the non-DC component in the power supply voltage and reduce the fluctuation of the device's power supply voltage.

[0070] It is understood that the intelligent control unit used in this embodiment of the invention is a high-performance STM32F7 series microcontroller manufactured by STMicroelectronics; the signal storage module uses a high-speed 128G memory card manufactured by SanDisk; and the triaxial electromagnetic monitoring sensor uses a triaxial magnetic field sensor manufactured by Honeywell. Those skilled in the art can choose according to the actual situation, and no specific limitation is made here.

[0071] The electromagnetic signal acquisition device for active cracks in concrete dams proposed in this embodiment of the invention solves the problem of difficulty in acquiring active crack signals in concrete dams. The active crack identification method is simple, the acquisition area is wider, and the reliability is higher. The solution model of the method is simple and has good real-time performance. The device has low power consumption.

[0072] Further, the method for acquiring electromagnetic signals of active cracks in concrete dams according to an embodiment of the present invention will be described with reference to the accompanying drawings. The method for acquiring electromagnetic signals of active cracks in concrete dams is applied in a device for acquiring electromagnetic signals of active cracks in concrete dams, such as... Figure 6 As shown, the method includes:

[0073] S1. Based on the distribution pattern of active cracks in concrete dams, select the area where active crack signals need to be collected, install a triaxial electromagnetic monitoring sensor on the concrete dam body, and combine it with the matching electromagnetic signal correction unit, electromagnetic signal conditioning unit, intelligent control unit and power supply unit to collect and store triaxial electromagnetic signals containing background noise of the concrete dam body.

[0074] S2, when active cracks in the concrete dam body expand, the electromagnetic signals generated are converted into triaxial electromagnetic analog signals by triaxial electromagnetic monitoring sensors. Compared with electromagnetic background noise, the triaxial electromagnetic analog signals are amplified, filtered and converted from analog to digital by electromagnetic signal conditioning units, and then converted into triaxial electromagnetic digital signals and sent to the intelligent control unit.

[0075] S3, the signal comparison module of the intelligent control unit combines the frequency and amplitude differences of the three-axis electromagnetic digital signals to eliminate the influence of internal interference noise in the device;

[0076] S4, the signal feature extraction module of the intelligent control unit combines the time-domain characteristics of the triaxial electromagnetic digital signal to identify the electromagnetic signal generated by the active crack in the concrete dam, and transmits the identified electromagnetic signal to the signal storage module.

[0077] Furthermore, in one embodiment of the present invention, the area selected for active crack signal acquisition is an area where cracks are likely to occur during routine inspections.

[0078] Furthermore, in one embodiment of the present invention, the triaxial electromagnetic simulation signal includes: x, y, z-axis magnetic field components collected by the triaxial electromagnetic monitoring sensor in the spatial radiation field of the acquisition area, wherein the three axes are perpendicular to each other.

[0079] Furthermore, in one embodiment of the present invention, the combination of frequency and amplitude differences of the triaxial electromagnetic digital signals includes: when the triaxial electromagnetic digital signals received by the intelligent control unit are not simultaneously identified, the main frequencies of the triaxial electromagnetic digital signals are inconsistent, or the main frequency of the triaxial electromagnetic digital signals is outside the 10kHz-10MHz range, the triaxial electromagnetic digital signals are considered to be environmental interference noise. Specifically, in an embodiment of the present invention, the waveform diagram of electromagnetic signal interference noise from active cracks in a concrete dam is as follows: Figure 7 As shown, the three-axis digital electromagnetic signals were not detected simultaneously, which can be attributed to environmental interference noise.

[0080] Furthermore, in one embodiment of the present invention, the step of combining the time-domain characteristics of the triaxial electromagnetic digital signal includes: when the triaxial electromagnetic digital signal received by the intelligent control unit is a pulse oscillation decay signal, and the signal rise time is less than 0.5ms and the decay time is less than 1.5ms, the received triaxial electromagnetic digital signal is considered to be an electromagnetic signal generated by an active crack in a concrete dam. Specifically, in an embodiment of the present invention, the waveform of the electromagnetic signal of an active crack in a concrete dam is as follows: Figure 8 As shown, the electromagnetic digital signal is a pulse decay signal, and its signal characteristics meet the requirements for generating electromagnetic signals by active cracks. Therefore, the electromagnetic digital signal at this time is stored in the signal storage module and awaits the next signal acquisition process.

[0081] The electromagnetic signal acquisition method for active cracks in concrete dams according to embodiments of the present invention can extract electromagnetic signals generated by active cracks in concrete dams using a triaxial electromagnetic monitoring sensor, filter out spatial magnetic field interference signals with the help of an electromagnetic signal correction unit and a conditioning unit, and identify and store the electromagnetic signals generated by active cracks through an intelligent control unit. The acquisition device can acquire electromagnetic signals generated by active cracks inside concrete dams, with a wider acquisition area and higher reliability. The method has a simple solution model, good real-time performance, and low power consumption.

[0082] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0083] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

Claims

1. An electromagnetic signal acquisition device for active cracks in a concrete dam, characterized in that, The device includes: a triaxial electromagnetic monitoring sensor (1), an electromagnetic signal correction unit (2), an electromagnetic signal conditioning unit (3), an intelligent control unit (4), and a power supply unit (5); The triaxial electromagnetic monitoring sensor (1) is used to acquire spatial three-dimensional magnetic field data of the surface of the concrete dam body; The electromagnetic signal correction unit (2) includes a differential circuit (21) and a notch filter circuit (22) for removing electromagnetic background noise from the electromagnetic radiation signal generated by the active cracks in the concrete dam. The electromagnetic signal conditioning unit (3) includes a first-stage amplifier circuit (31), a low-pass filter circuit (32), a second-stage amplifier circuit (33), a band-pass filter circuit (34), and an analog-to-digital converter circuit (35), which is connected to the triaxial electromagnetic monitoring sensor (1) and is used to convert the electromagnetic analog signal collected by the triaxial electromagnetic monitoring sensor (1) into an electromagnetic digital signal. The intelligent control unit (4) includes a signal temporary storage module (41), a signal comparison module (42), a signal feature extraction module (43), and a signal storage module (44), which are connected to the electromagnetic signal conditioning unit (3) and are used to identify and store electromagnetic signals generated by active cracks in concrete dams. The power supply unit includes a power supply battery (51), a power protection circuit (52), a power conversion circuit (53), and a power filtering circuit (54), which are connected to the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4) to provide the required voltage and current for the normal operation of the triaxial electromagnetic monitoring sensor (1), the electromagnetic signal correction unit (2), the electromagnetic signal conditioning unit (3), and the intelligent control unit (4).

2. The apparatus as claimed in claim 1, characterized in that, The sampling rate of the electromagnetic signal of the triaxial electromagnetic monitoring sensor (1) is greater than 10MHz, and the minimum scale value of the electromagnetic signal is less than 10nT.

3. The apparatus as described in claim 1, characterized in that, The differential circuit (21) is used to compare the difference between the triaxial electromagnetic analog signal and the background noise of the concrete dam in order to filter out low-frequency electromagnetic signals. The notch filter circuit (22) is used to remove background noise of a preset frequency from the triaxial electromagnetic analog signal; The first-stage amplifier circuit (31) is a low-gain, low-noise voltage amplifier circuit with noise levels below 5nV / √Hz and a voltage amplification factor not exceeding 20. The low-pass filter circuit (32) is used to filter out low-frequency interference electromagnetic signals with a frequency below 100Hz; The secondary amplifier circuit (33) is a high-gain, high-speed voltage amplifier circuit with a gain-bandwidth product greater than 2GHz and a voltage amplification factor of not less than 200. The bandpass filter circuit (34) is used to filter out interfering electromagnetic signals with frequencies below 10kHz and above 10MHz; The sampling resolution of the analog-to-digital converter circuit (35) is not less than 16 bits, and the data conversion rate is not less than 50MHz.

4. The apparatus as claimed in claim 1, characterized in that, The temporary signal storage module (41) is used to temporarily record the waveform of the triaxial electromagnetic digital signal, and the duration of a single recorded electromagnetic signal is greater than 2ms. The signal comparison module (42) is used to compare the differences between the waveforms of the three-axis electromagnetic digital signals and eliminate interference noise inside the electromagnetic signal acquisition device. The signal feature extraction module (43) is used to distinguish between electromagnetic signals of active cracks in concrete dams and environmental interference signals and interference noise inside the electromagnetic signal sampling unit. The signal storage module (44) is connected to the signal feature extraction module (43) and is used to store electromagnetic signals of active cracks in concrete dams. The duration of the electromagnetic signal generated by a single active crack is greater than 2ms.

5. The apparatus as claimed in claim 1, characterized in that, The power supply battery (51) is powered by a combination of a high-energy-density lithium battery pack and a solar panel; The power protection circuit (52) is used to protect the power supply battery from overvoltage and overcurrent. The power conversion circuit (53) is used to convert the power supply voltage of the power supply battery into the power supply voltage corresponding to the triaxial electromagnetic monitoring sensor, electromagnetic signal acquisition unit and intelligent control unit; The power supply filter circuit (54) is used to filter out the non-DC component in the power supply voltage.

6. A method for acquiring electromagnetic signals of active cracks in a concrete dam, characterized in that, The method, when applied to the electromagnetic signal acquisition device for active cracks in concrete dams as described in any one of claims 1-5, includes the following steps: Based on the distribution pattern of active cracks in concrete dams, areas where active crack signals need to be collected are selected. Triaxial electromagnetic monitoring sensors are installed on the concrete dam body, and combined with supporting electromagnetic signal correction units, electromagnetic signal conditioning units, intelligent control units and power supply units, triaxial electromagnetic signals of the concrete dam body containing background noise are collected and stored. When active cracks in the concrete dam body propagate, the generated electromagnetic signal is converted into a triaxial electromagnetic analog signal by a triaxial electromagnetic monitoring sensor. Compared with electromagnetic background noise, the triaxial electromagnetic analog signal is amplified, filtered, and converted from analog to digital by an electromagnetic signal conditioning unit, and then converted into a triaxial electromagnetic digital signal and sent to the intelligent control unit. The signal comparison module of the intelligent control unit combines the frequency and amplitude differences of the triaxial electromagnetic digital signals to eliminate internal interference noise. The signal feature extraction module of the intelligent control unit combines the time-domain characteristics of the triaxial electromagnetic digital signal to identify the electromagnetic signal generated by the active crack in the concrete dam, and transmits the identified electromagnetic signal to the signal storage module.

7. The method as described in claim 6, characterized in that, The selected areas for active crack sampling include: areas of concrete dams with a high load-bearing ratio, areas prone to cracks during routine inspections, and areas where micro-cracks have appeared but have not yet caused serious cracking.

8. The method as described in claim 6, characterized in that, The triaxial electromagnetic simulation signal includes: x, y, z three-axis magnetic field components collected by the triaxial electromagnetic monitoring sensor (1) in the spatial radiation field of the acquisition area, and the three axes are perpendicular to each other.

9. The method as described in claim 6, characterized in that, The combination of frequency and amplitude differences of the three-axis electromagnetic digital signal includes: when the three-axis electromagnetic digital signal received by the intelligent control unit (4) is not recognized simultaneously, the main frequency of the three-axis electromagnetic digital signal is inconsistent, or the main frequency of the three-axis electromagnetic digital signal is outside the range of 10kHz-10MHz, the three-axis electromagnetic digital signal is environmental interference noise.

10. The method as described in claim 6, characterized in that, The combination of the time-domain characteristics of the triaxial electromagnetic digital signal includes: when the triaxial electromagnetic digital signal received by the intelligent control unit (4) is a pulse oscillation attenuation signal, and the signal rise time is less than 0.5ms and the attenuation time is less than 1.5ms, the received triaxial electromagnetic digital signal is an electromagnetic signal generated by the active crack of the concrete dam.

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