High-precision magnetic imaging method, device and equipment for underground preferential flow channel and medium

Abstract

This application relates to a high-precision magnetic imaging method, apparatus, equipment, and medium for underground dominant flow channels. The method includes: responding to the need for high-precision magnetic imaging of underground dominant flow channels, preparing a magnetotactic bacterial tracer fluid and constructing a target medium model; based on an underground flow field magnetic detection platform, controlling the injection of the magnetotactic bacterial tracer fluid into the target medium model and collecting magnetic field data throughout the seepage process; processing the magnetic field data using a geophysical inversion algorithm to obtain a magnetic parameter matrix; based on the relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, inverting the magnetic parameter matrix into a flow velocity vector field matrix; and obtaining the imaging results of the underground dominant flow channel based on the target medium model and the flow velocity vector field matrix. This solves the problems in related technologies, such as the inability to penetrate metal shielding structures, susceptibility to solid particle blockage, restricted transport, environmental background noise interference, and the inability to eliminate static background effects.

Description

Technical Field

[0001] This application relates to the field of geological disaster prevention and control technology, and in particular to a high-precision magnetic imaging method, device, equipment and medium for underground dominant flow channels. Background Technology

[0002] In the fields of water conservancy and hydropower engineering (piping in dams), urban underground space engineering (seepage in shield tunnels), geological disaster prevention and control, and groundwater pollution remediation, it is crucial to accurately characterize the evolution and velocity characteristics of dominant flow channels (such as piping channels, karst conduits, and high-permeability fissures) within concealed media. Current monitoring technologies mainly include electrical resistance tomography (ERT), ground penetrating radar (GPR), self-potential (SP), isotope / chemical tracing, and conventional particle tracing. However, these methods all face insurmountable technical bottlenecks when dealing with complex metallic shielding environments and characterizing deep microscopic dynamic mechanisms.

[0003] First, conventional geophysical exploration methods face severe problems of signal shielding, resolution attenuation, and multiple solutions in complex environments. For scenarios involving metal structures such as shield tunnels: existing electrical resistivity tomography (EPR) and ground-penetrating radar (GPR) methods are extremely ineffective at detecting grouting or seepage channels behind tunnel walls. This is because the dense steel mesh inside the shield segments forms a "Faraday cage," strongly shielding and reflecting electric fields and high-frequency electromagnetic waves, making it difficult for detection signals to penetrate the segments and reach the back wall. Furthermore, the strong inductive signal from the steel mesh masks weak fluid signals, creating a near-field blind zone, making it impossible to effectively identify cavities or water flow behind the wall. For natural rock and soil scenarios: traditional EPR methods suffer from severe resolution attenuation with depth and primarily reflect differences in resistivity, making it difficult to distinguish between static high-water-content areas and high-speed flowing piping channels. They are also insensitive to fluid dynamics characteristics, easily leading to engineering misjudgments. While the spontaneous potential method is based on electrokinetic effects, its signal is weak (millivolt level), highly susceptible to environmental electromagnetic noise and soil chemical potential interference, resulting in a high misjudgment rate and difficulty in early identification of small piping channels.

[0004] Secondly, traditional tracer technologies lack the ability to actively respond to fluid dynamics and face the dual challenges of poor timeliness and impeded transport. Chemical or dye tracers are passive monitoring methods, requiring sampling and analysis at the outlet, resulting in significant time lags and an inability to obtain information on three-dimensional underground flow paths. While conventional solid nanoparticle tracers attempt to utilize functionalized particles for detection, they face severe filtration effects: dead particles lack autonomous movement and rely entirely on water flow for transport. When flowing through narrow pores and throats in heterogeneous soil and rock media, they are highly susceptible to physical adsorption, mechanical retention, or flocculation blockage due to Brownian motion impacting the pore walls. This not only leads to the loss of deep signals but also alters the original permeability of the medium, causing secondary blockages. Furthermore, existing geophysical exploration approaches are mostly limited to optimizing external detection instruments, rarely considering functional modification of the tracer liquid itself. Conventional tracers cannot actively emit physical fields as signal sources, resulting in low signal-to-noise ratios and heavy reliance on external strong excitation sources. Summary of the Invention

[0005] This application provides a high-precision magnetic imaging method, apparatus, equipment, and medium for underground dominant flow channels, in order to solve the problems in related technologies such as inability to penetrate metal shielding structures, susceptibility to blockage by solid particles, limited transport, interference from environmental background noise, and inability to eliminate the influence of static background.

[0006] To achieve the above objectives, the first aspect of this application proposes a high-precision magnetic imaging method for underground dominant flow channels, comprising the following steps:

[0007] In response to the need for high-precision magnetic imaging of underground dominant flow channels, a magnetotactic bacterial tracer fluid was prepared and a target medium model was constructed. Based on a pre-set underground flow field magnetic detection platform, the magnetotactic bacterial tracer fluid is injected into the target medium model, and magnetic field data of the entire seepage process is collected. Based on a pre-set geophysical inversion algorithm, the magnetic field data is processed to obtain a magnetic parameter matrix. Based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. Based on the type of the target medium model, the imaging results of the underground dominant flow channel of the target medium model are obtained according to the flow velocity vector field matrix.

[0008] According to one embodiment of this application, the target medium model is a natural rock and soil seepage model, and the step of obtaining the imaging results of the underground dominant flow channels of the target medium model based on the type of the target medium model and the flow velocity vector field matrix includes: Based on the natural rock and soil seepage model, a strip-shaped channel diagram that satisfies the preset flow velocity is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the strip-shaped channel diagram of the preset flow velocity.

[0009] According to one embodiment of this application, the target medium model is an indoor standard calibration model, and the step of obtaining the imaging results of the underground dominant flow channels of the target medium model based on the type of the target medium model and the flow velocity vector field matrix includes: Based on the indoor standard calibration model, a flow velocity cloud map is generated according to the flow velocity vector field matrix; The imaging results of the subsurface dominant flow channels of the target medium model are obtained based on the velocity cloud map. According to one embodiment of this application, the target medium model is a metal-shielded environment model. The step of obtaining the imaging results of the subsurface dominant flow channels of the target medium model based on the type of the target medium model and the velocity vector field matrix includes: Based on the metal shielding environment model, the unfolded diagram of the seepage field behind the tunnel's entire annular wall is obtained according to the velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are obtained based on the unfolded diagram of the seepage field behind the tunnel's full annular wall.

[0010] According to one embodiment of this application, before inverting the magnetic parameter matrix into a velocity vector field matrix based on a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the method further includes: Determine multiple test flow rates, multiple applied magnetic field frequencies, and multiple metal shielding coefficients; Based on each test flow rate, the magnetic signal response of the bacterial cluster was measured under the combined conditions of multiple external magnetic field frequencies and multiple metal shielding coefficients, so as to obtain the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow rate. The preset relationship between the penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity is constructed based on the penetrating magnetic signal characteristics corresponding to each parameter combination at each test flow rate.

[0011] According to one embodiment of this application, after obtaining the imaging results of the subsurface dominant flow channel of the target medium model based on the flow velocity vector field matrix, the method further includes: The target medium model is placed in a magnetotactic bacteria degradation environment and the survival rate of the degraded magnetotactic bacteria is obtained; and / or, an environmentally friendly antibacterial agent or oxidant is injected into the target medium model and the survival rate of the treated magnetotactic bacteria is obtained. When the survival rate of the degraded magnetotactic bacteria is lower than a preset threshold, or when the survival rate of the treated magnetotactic bacteria is lower than the preset threshold, the preset safety conditions are determined to be met.

[0012] The high-precision magnetic imaging method for underground dominant flow channels proposed in this application involves controlling the injection of magnetotactic bacterial tracer fluid into a target medium model and collecting magnetic field data throughout the seepage process. The magnetic field data is processed to obtain a magnetic parameter matrix. Based on the relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are then obtained from the flow velocity vector field matrix. This solves the problems in related technologies, such as the inability to penetrate metal shielding structures, susceptibility to solid particle blockage, restricted transport, environmental background noise interference, and the inability to eliminate static background effects.

[0013] To achieve the above objectives, a second aspect of this application provides a high-precision magnetic imaging device for underground dominant flow channels, comprising: The module was constructed in response to the need for high-precision magnetic imaging of underground dominant flow channels, to prepare magnetotactic bacterial tracer fluid and build a target medium model; The acquisition module, based on a preset underground flow field magnetic detection platform, controls the injection of the magnetotactic bacterial tracer fluid into the target medium model and acquires magnetic field data of the entire seepage process. Based on a preset geophysical inversion algorithm, the magnetic field data is processed to obtain a magnetic parameter matrix. The imaging module, based on a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, inverts the magnetic parameter matrix into a flow velocity vector field matrix, and obtains the imaging results of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix according to the type of the target medium model.

[0014] According to one embodiment of this application, the target medium model is a natural rock and soil seepage model, and the imaging module is specifically used for: Based on the natural rock and soil seepage model, a strip-shaped channel diagram that satisfies the preset flow velocity is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the strip-shaped channel diagram of the preset flow velocity.

[0015] According to one embodiment of this application, the target medium model is an indoor standard calibration model, and the imaging module is specifically used for: Based on the indoor standard calibration model, a flow velocity cloud map is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the flow velocity cloud map.

[0016] According to one embodiment of this application, the target medium model is a metal-shielded environment model, and the imaging module is specifically used for: Based on the metal shielding environment model, the unfolded diagram of the seepage field behind the tunnel's entire annular wall is obtained according to the velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are obtained based on the unfolded diagram of the seepage field behind the tunnel's full annular wall.

[0017] According to one embodiment of this application, the imaging module is further configured to: Determine multiple test flow rates, multiple applied magnetic field frequencies, and multiple metal shielding coefficients; Based on each test flow rate, the magnetic signal response of the bacterial cluster was measured under the combined conditions of multiple external magnetic field frequencies and multiple metal shielding coefficients, so as to obtain the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow rate. The preset relationship between the penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity is constructed based on the penetrating magnetic signal characteristics corresponding to each parameter combination at each test flow rate.

[0018] According to one embodiment of this application, after obtaining the imaging result of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix, the imaging module is further configured to: The target medium model is placed in a magnetotactic bacteria degradation environment and the survival rate of the degraded magnetotactic bacteria is obtained; and / or, an environmentally friendly antibacterial agent or oxidant is injected into the target medium model and the survival rate of the treated magnetotactic bacteria is obtained. When the survival rate of the degraded magnetotactic bacteria is lower than a preset threshold, or when the survival rate of the treated magnetotactic bacteria is lower than the preset threshold, the preset safety conditions are determined to be met.

[0019] The high-precision magnetic imaging device for underground dominant flow channels proposed in this application controls the injection of magnetotactic bacterial tracer fluid into a target medium model and collects magnetic field data throughout the seepage process. The magnetic field data is processed to obtain a magnetic parameter matrix. Based on the relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are then obtained from the flow velocity vector field matrix. This solves the problems in related technologies, such as the inability to penetrate metal shielding structures, susceptibility to solid particle blockage, restricted transport, environmental background noise interference, and the inability to eliminate static background effects.

[0020] To achieve the above objectives, a third aspect of this application provides an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the high-precision magnetic imaging method for underground dominant flow channels as described in the above embodiments.

[0021] To achieve the above objectives, a fourth aspect of this application provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement the high-precision magnetic imaging method for underground dominant flow channels as described in the above embodiments.

[0022] To achieve the above objectives, a fifth aspect of this application provides a computer program product, which, when executed by a processor, implements the high-precision magnetic imaging method for underground dominant flow channels as described in the above embodiments.

[0023] Additional aspects and advantages of this application 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 this application. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of a high-precision magnetic imaging method for underground dominant flow channels provided according to an embodiment of this application; Figure 2 This is a schematic diagram illustrating the dynamic response principle of magnetotactic bacteria based on a magnetohydrodynamic coupling mechanism according to an embodiment of this application; Figure 3 This is a schematic diagram of a magnetic signal characteristic versus flow velocity quantitative calibration curve provided according to an embodiment of this application; Figure 4 This is a comparative schematic diagram of the related technical detection method provided according to an embodiment of this application and the imaging method of the embodiment of this application; Figure 5 A flowchart of a high-precision magnetic imaging method for underground dominant flow channels according to an embodiment of this application; Figure 6 This is a schematic diagram of the structure of a high-precision magnetic imaging system for underground dominant flow channels according to an embodiment of this application; Figure 7 This is a schematic diagram of the structure of a magnetic scanning detection system for piping channels in the foundation of an earth-rock dam, according to an embodiment of this application. Figure 8 This is a schematic diagram of a high-precision magnetic scanning detection system according to an embodiment of this application; Figure 9 This is a schematic diagram of a vehicle-mounted tunnel wall-mounted magnetic scanning observation system according to an embodiment of this application; Figure 10 This is a block diagram of a high-precision magnetic imaging device for underground dominant flow channels provided according to an embodiment of this application; Figure 11This is a schematic diagram of the structure of an electronic device provided according to an embodiment of this application. Detailed Implementation

[0025] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0026] The following describes, with reference to the accompanying drawings, a high-precision magnetic imaging method, apparatus, equipment, and medium for underground dominant flow channels according to embodiments of this application. First, the high-precision magnetic imaging method for underground dominant flow channels according to embodiments of this application will be described with reference to the accompanying drawings.

[0027] Figure 1 This is a flowchart of a high-precision magnetic imaging method for underground dominant flow channels according to an embodiment of this application.

[0028] like Figure 1 As shown, the high-precision magnetic imaging method for the underground dominant flow channel includes the following steps: In step S101, in response to the need for high-precision magnetic imaging of underground dominant flow channels, a magnetically tactic bacterial tracer fluid is prepared, and a target medium model is constructed.

[0029] Among them, the subsurface dominant flow channel refers to the preferential fluid transport path formed by the heterogeneity of the medium space in underground porous / fractured media. Magnetotactic bacterial tracer fluid refers to a functional tracer fluid prepared by combining magnetotactic bacteria as tracers with a fluid medium.

[0030] Specifically, in this application embodiment, magnetotactic bacterial strains with high magnetotaxis and strong motility (such as magnetotactic spirochetes) are selected as probes, amplified and cultured in a specific culture medium to the logarithmic growth phase, and then prepared into a concentration of 10 by centrifugation and resuspension. 7 -10 8Concentrated bacterial solution with cells / mL. This application's embodiments address the biochemical matching, rheological regulation, and activity modification of the base fluid for different underground environments: For natural groundwater environments, a buffer solution with ionic strength and pH value similar to the target groundwater is prepared as the base fluid, and trace amounts of chemotactic inducers (such as succinate) are added to further guide bacterial migration to specific areas using chemotaxis; For tunnel wall grouting or highly alkaline environments, alkali-resistant strains are selected or surface biofilm modification technology is used to protect bacterial activity, while adjusting the density and viscosity parameters of the base fluid to match uncoagulated grout or high-viscosity fluids. The tracer base fluid is not limited to groundwater or grouting fluid, but can also be extended to non-Newtonian fluids, high-viscosity polymer solutions, or gas-containing multiphase flows. Utilizing the hindering effect of different fluid rheological properties on bacterial movement, the rheological parameters of the fluid can be further inverted. Thus, the preparation of the magnetotactic bacterial tracer fluid is completed. As one possible approach, the tracer probe can also be selected from other strains with strong magnetotaxis or special environmental adaptability, including but not limited to: magnetotactic cocci or genetically engineered Escherichia coli with high magnetosome production, to adapt to groundwater environments with different temperatures, high salinity, or extreme pH values; for extreme environments such as high temperature and strong acid that are unsuitable for biological survival, artificial magnetic helical micro-nano robots can be used to replace natural bacteria, which can also move under magnetic field drive and respond to fluid shear; in addition, for scenarios where biological penetration is not required and only the detection of large cavities behind the wall or large flow leakage is needed, a high concentration of superparamagnetic nano iron oxide suspension can be used directly to achieve rapid scanning of deep macroscopic flow fields using its stronger magnetic response signal; furthermore, the probe surface is not limited to biofilm modification, but can also be loaded with repair materials (such as nano silicates) or multimodal contrast agents (such as conductive polymers), and while completing the detection, the loaded material is released using the magnetocaloric effect or environmental response mechanism to achieve "integrated detection and blocking" or "magnetic-electric joint detection".

[0031] Furthermore, after the magnetically tactic bacterial tracer fluid is prepared, this embodiment of the application needs to determine the magnetic response curve of the fluid and the bacterial flagellar motility to ensure that it maintains solution-like suspension stability and active transport capability in complex underground environments.

[0032] Furthermore, this application embodiment constructs three types of physical models or monitoring scenarios based on the observation object. The target medium models are a natural rock seepage model, a metal shielding environment model, and an indoor standard calibration model. Specifically, this application embodiment constructs a natural rock and soil seepage model (such as dam foundations and slopes) to observe bacterial transport with water flow and the tracing effect on dominant channels in non-uniform porous media; it constructs a metal shielding environment model (such as shield tunnel segments with steel mesh) to verify the penetration capability of low-frequency magnetic fields into metal structures and the extraction effect of fluid signals behind the wall; and it constructs an indoor standard calibration model, using transparent microfluidic chips or standard sand columns to establish a quantitative relationship between magnetic signals and fluid dynamic parameters under controlled conditions. In addition, this application embodiment is not limited to dam piping and tunnel leakage, but is also applicable to the monitoring of hydraulic fracturing fluid migration in petroleum engineering (depicting fracture networks), the diffusion tracking of groundwater pollution plumes, and the assessment of grouting fullness of microcracks inside concrete structures.

[0033] In step S102, based on the preset underground flow field magnetic detection platform, the magnetically tactile bacteria tracer fluid is injected into the target medium model, and magnetic field data of the entire seepage process is collected. Based on the preset geophysical inversion algorithm, the magnetic field data is processed to obtain the magnetic parameter matrix.

[0034] The pre-designed underground flow field magnetic detection platform refers to a pre-designed and constructed magnetic measurement system used to detect the characteristics of underground fluid flow. The pre-designed geophysical inversion algorithm can be a user-defined algorithm, an algorithm obtained through a limited number of experiments, or an algorithm obtained through a limited number of computer simulations.

[0035] Specifically, the pre-designed underground flow field magnetic detection platform mainly consists of a low-frequency magnetic field excitation unit, a high-sensitivity magnetic acquisition unit, and a data processing workstation. The excitation unit uses a Helmholtz coil or a large loop of flexible conductive wire laid on the ground surface to generate a low-frequency alternating magnetic field with an adjustable frequency (1-20Hz) and an intensity approximately 2-5 times that of the Earth's magnetic field as a modulation signal. The frequency selection must avoid the power frequency (50 / 60Hz) and be low enough to penetrate the steel mesh without producing a significant skin effect. The acquisition unit uses a high-sensitivity fluxgate sensor array or an atomic magnetometer, placed close to the tunnel wall, the ground surface, or in the measurement borehole. It employs differential measurement technology to eliminate background static magnetic field interference and is used to acquire secondary magnetic field signals containing bacterial response information. As a possible approach, although fluxgate magnetometers are relatively mature in engineering applications, for the detection of extremely weak seepage signals in shallow layers, superparamagnetic quantum interference devices can be used as an alternative to obtain extremely high magnetic field resolution at the femtotes level. For shield tunnel construction scenarios, a ring sensor array can be designed and installed at the tail of the shield machine to scan the grouting quality behind the wall in real time as tunneling progresses, achieving synchronous construction monitoring. Furthermore, in addition to using sinusoidal magnetic field modulation, square wave or pulsed magnetic field excitation can also be used. By measuring the relaxation time of bacterial magnetic moments, fluid viscosity and pore structure characteristics can be inverted. For deep detection of extremely thick shield segments or double-layer linings, a physically rotating permanent magnet array can be used instead of coils to generate a low-frequency magnetic field, thereby generating a stronger magnetic torque to penetrate the shielding layer.

[0036] Furthermore, in this embodiment, based on a target medium model, magnetotactic bacterial tracer fluid is injected upstream of the target area in the target medium model (such as boreholes, grouting holes, rainfall infiltration surfaces, or upstream of known seepage points). The bacteria migrate with the fluid, relying on their own flagellar oscillations to penetrate soil pores or fissures. Further, this embodiment activates a magnetic field excitation unit, emitting a guiding magnetic field of a specific frequency (e.g., 8Hz), and uses lock-in amplification technology to extract the secondary magnetic field component in the acquisition unit that is at the same frequency as the excitation. During this process, this embodiment captures abnormal areas of the magnetic signal in real time: in still water or low-velocity areas, the signal amplitude is high and the phase lag is small; in the dominant flow channel (high-velocity area), due to strong fluid shear interference, the bacterial magnetic moment alignment decohers, resulting in a significant decrease in signal amplitude and a large phase lag, thus distinguishing between still and moving water bodies.

[0037] Furthermore, in this embodiment of the application, a preset geophysical inversion algorithm is used to process the collected magnetic field data to obtain a magnetic parameter matrix.

[0038] In step S103, based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. Based on the type of the target medium model, the imaging results of the underground dominant flow channel of the target medium model are obtained according to the flow velocity vector field matrix.

[0039] Optionally, in some embodiments, the target medium model is a natural rock and soil seepage model. Based on the type of the target medium model, the imaging results of the underground dominant flow channels of the target medium model are obtained according to the velocity vector field matrix, including: generating a strip-shaped channel map that satisfies a preset flow velocity based on the natural rock and soil seepage model and the velocity vector field matrix; and obtaining the imaging results of the underground dominant flow channels of the target medium model according to the strip-shaped channel map with the preset flow velocity.

[0040] Among them, the penetrating magnetic signal characteristic refers to the inherent quantitative characteristics of the effective magnetic signal generated by the magnetotactic bacterial tracer fluid as it migrates with the underground fluid in the target medium model, capable of penetrating the target medium. The metal shielding coefficient refers to the quantitative characteristic parameter of the degree of shielding and attenuation of the penetrating magnetic signal by the metal components and metallic structures in the target medium model. The velocity vector field matrix refers to a two-dimensional or three-dimensional matrix formed by digitizing and meshing the velocity vector information of the fluid within the micropores of the soil and rock medium. The preset velocity can be a user-defined velocity, a velocity obtained through a finite number of experiments, or a velocity obtained through a finite number of computer simulations.

[0041] Specifically, when the target medium model is a natural rock and soil seepage model, this embodiment uses a differential algorithm to remove static geomagnetic field interference from the magnetic parameter matrix obtained in step S102 and extracts dynamic magnetic response components. Based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic velocity, the surface magnetic parameter (such as phase and amplitude) matrix is ​​inverted into the underground velocity vector field. The reconstruction result shows a high-velocity strip-shaped channel. Specifically, this embodiment analyzes the underground velocity vector field matrix obtained based on the biomagnetic probe inversion and extracts the velocity amplitude and flow direction vector information in each three-dimensional grid cell. According to the preset dominant flow determination threshold (usually set to 3 to 5 times the average velocity of the entire field, corresponding to the high response area of ​​biomagnetic clusters), the entire field data is binarized and filtered to retain high-velocity characteristic grid cells with amplitudes greater than the threshold. Subsequently, the data is further processed... The selected discrete high-velocity units undergo spatial connectivity discrimination. A 3D region growing algorithm is used to group spatially adjacent continuous grids with consistent velocity vector directions (angle less than a preset tolerance) into the same dominant flow core domain, forming an initial channel distribution model. Then, through morphological skeleton extraction and strip reconstruction (including central ridge refinement, weighted dilation based on local flux, and edge smoothing), irregular clumps are reconstructed into linearly extending, topologically clear strip or tubular structures. Finally, combining the geological model coordinate system with the reconstruction results, a high-precision magnetic imaging map of the underground dominant flow channels is generated, which intuitively reflects the concentrated transport path of groundwater and has a clear flow direction indication. Thus, the imaging results of the underground dominant flow channels of the target medium model are obtained.

[0042] Optionally, in some embodiments, the target medium model is an indoor standard calibration model. Based on the type of the target medium model, the imaging results of the underground dominant flow channels of the target medium model are obtained according to the velocity vector field matrix, including: generating a velocity cloud map based on the velocity vector field matrix of the indoor standard calibration model; and obtaining the imaging results of the underground dominant flow channels of the target medium model according to the velocity cloud map.

[0043] Among them, the velocity cloud map refers to a spatial distribution visualization image of underground fluid velocity generated based on the velocity vector field matrix as the core data foundation.

[0044] Specifically, when the target medium model is an indoor standard calibration model, based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, this embodiment of the application transforms the magnetic field intensity distribution in the magnetic parameter matrix obtained in step S102 into a microscopic flow velocity vector field, and the further generated flow velocity cloud map shows the complex transport path of pollutants around the lens. Specifically, this embodiment first performs data cleaning and denoising preprocessing on the discrete velocity vector field matrix obtained from the inversion based on the biomagnetic probe, extracting the velocity vector components in the x, y, and z directions of each spatial node; the velocity amplitude of each node is calculated through vector modulus operation to form a basic velocity scalar field; then, an adaptive boundary-preserving interpolation algorithm with gradient weighting is adopted to reconstruct the discrete point data into a high-resolution continuous spatial velocity distribution field while suppressing channel edge blurring and artifact diffusion; subsequently, a dynamic threshold is set according to the velocity amplitude distribution range, and a multi-color gradient spectrum from cool to warm tones is used to color map different velocity ranges, using the difference in color warmth to intuitively represent the velocity strength, and three-dimensional vector symbols such as streamlines or arrows are superimposed on the velocity cloud map to accurately indicate the local flow direction; finally, the geometric boundary of the model, geological stratification information, and spatial coordinate system are integrated to complete the three-dimensional visualization rendering, ultimately generating a high-precision velocity vector cloud map that can clearly reflect the spatial distribution law of groundwater velocity and also has the function of flow direction indication. Thus, the imaging results of the underground dominant flow channel of the target medium model are obtained.

[0045] Optionally, in some embodiments, the target medium model is a metal-shielded environment model. Based on the type of the target medium model, the imaging results of the underground dominant flow channels of the target medium model are obtained according to the velocity vector field matrix, including: obtaining the tunnel full-ring wall back-seepage field unfolding diagram based on the metal-shielded environment model and the velocity vector field matrix; and obtaining the imaging results of the underground dominant flow channels of the target medium model according to the tunnel full-ring wall back-seepage field unfolding diagram.

[0046] Among them, the tunnel full-ring wall back seepage field unfolding diagram refers to the exclusive seepage field visualization image that unfolds the three-dimensional spatial distribution of the seepage field behind the tunnel full-ring wall into a two-dimensional plane.

[0047] Specifically, when the target medium model is a metal-shielded environment model, this embodiment uses differential inversion imaging technology to generate a behind-wall seepage field unfolding map of the magnetic parameter matrix obtained in step S102, and performs spatial registration and differential processing on the collected time series data. Based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic velocity, the static strong interference of the tunnel segment reinforcement is eliminated, and the remaining dynamic magnetic anomaly signal is inverted into the microscopic velocity vector distribution of the fluid behind the wall, generating a tunnel full-ring behind-wall seepage field unfolding map. Specifically, this embodiment establishes a cylindrical coordinate system for the behind-wall region in conjunction with the tunnel annular structure characteristics, and performs coordinate transformation on the three-dimensional velocity vector data of the spatial nodes behind the tunnel full-ring wall obtained based on the biomagnetic probe inversion. x , y , z → r , θ , z ), extract the radial velocity components of each node ( v r The total velocity amplitude was then used to map the region behind the annular wall into a two-dimensional plane coordinate system (horizontal axis for axial mileage, vertical axis for circumferential angle). Discrete velocity data behind the wall were mapped onto this plane, and a continuous two-dimensional seepage velocity distribution field was reconstructed using a high-fidelity spatial interpolation algorithm. Then, dynamic color levels were defined based on the velocity amplitude range, and a multi-color gradient chromatogram was used for color mapping, targeting radial infiltration (…). v r <0) and extravasation ( v r >0) Flow velocity is indicated by warm / cool color tones or vector direction markers to visually represent the migration direction and intensity differences of water behind the tunnel wall. Finally, engineering annotation information such as tunnel circumferential orientation (e.g., arch crown, arch waist, arch bottom) and axial mileage is superimposed to complete the visualization rendering, ultimately generating a high-precision unfolded map of the seepage field that comprehensively reflects the spatial distribution characteristics of seepage behind the tunnel wall and the infiltration risk level. This yields the imaging results of the underground dominant flow channels of the target medium model.

[0048] Therefore, the embodiments of this application are based on a multi-physics coupling mechanism of microhydrodynamic shearing and biomagnetic synergistic response. The core lies in constructing a bioengineering-optimized magnetotactic bacterial tracer fluid system. This system utilizes naturally synthesized nanoscale magnetic body chains within the bacteria as distributed microscopic magnetic sensors, combined with active modulation technology of low-frequency alternating magnetic fields, to achieve non-destructive detection of the internal flow field of complex, concealed underground media. Figure 2 As shown, Figure 2This is a schematic diagram illustrating the dynamic response principle of magnetotactic bacteria based on a magnetohydrodynamic coupling mechanism, according to an embodiment of this application. When the fluid is stationary, under the influence of an externally applied low-frequency guiding magnetic field, magnetotactic bacteria are driven by magnetic torque to align neatly along magnetic field lines, exhibiting a strong induced magnetic field with the same frequency and phase as the excitation source. When the fluid flows through a dominant flow channel (such as piping, fissures, or cavities behind structural walls), the fluid viscosity influences the formation of a velocity gradient within the pores, generating a hydrodynamic shear torque on the bacterial surface. This shear torque competes with the external magnetic field torque, causing the directional alignment of the bacterial cluster to be disturbed or periodically reversed, thereby generating a dynamic secondary magnetic field response containing specific phase lag and amplitude attenuation. Benefiting from the excellent penetration ability of low-frequency magnetic fields (<100Hz) into non-magnetic media (rock, soil, concrete) and metal mesh structures, as well as the dynamic characteristics of biomagnetic signals in the frequency domain, this embodiment can effectively overcome signal attenuation in deep strata and interference from complex environments (such as metal shielding or strong background noise). The dynamic magnetic response of bacterial clusters under flowing shear conditions is distinctly different in the frequency domain from the static or linear fundamental frequency response of stationary media (soil and rock skeletons, reinforced concrete structures). By extracting this dynamic characteristic using lock-in amplification (LAP), flowing water can be precisely separated from a static background. Based on magnetohydrodynamics and Langevin statistics, the local velocity gradient within pores is quantitatively correlated with the magnetic order of bacterial clusters (i.e., the phase lag / amplitude attenuation of the secondary magnetic field signal) (i.e., higher velocity leads to stronger shear disturbance and greater phase lag). Therefore, by transmitting a low-frequency modulated magnetic field through the overburden layer at the surface or through observation wells, and using a high-sensitivity magnetic sensor array to capture the dynamic response of underground bacterial clusters, and establishing a quantitative physical mapping model of "magnetic signal characteristics (phase / amplitude) - shear stress - fluid velocity," the invisible underground microscopic seepage velocity field can be transformed into a visible and quantifiable magnetic signal field, enabling precise location and dynamic characterization of dominant flow channels within various soil and rock media and engineering structures.

[0049] Furthermore, in this embodiment of the application, a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity is constructed through coupling tests of multiple sets of flow velocities, applied magnetic field frequencies, and metal shielding coefficients.

[0050] Optionally, in some embodiments, before inverting the magnetic parameter matrix into a velocity vector field matrix based on a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the method further includes: determining multiple test flow velocities, multiple applied magnetic field frequencies, and multiple metal shielding coefficients; measuring the magnetic signal response of the bacterial cluster under the combined conditions of multiple applied magnetic field frequencies and multiple metal shielding coefficients based on each test flow velocity to obtain the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow velocity; and constructing a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity based on the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow velocity.

[0051] Among them, bacterial clusters refer to the regional group aggregation and distribution state of magnetotactic bacteria in a fluid medium under the combined effects of test conditions such as test flow rate, applied magnetic field frequency, and metal shielding coefficient.

[0052] Specifically, in this embodiment of the application, calibration tests are conducted in a standard flow channel and shielded environment before formal detection. This embodiment of the application determines multiple sets of test flow rates ( v ), multiple external magnetic field frequencies ( f ) and multiple metal shielding coefficients ( S Three types of test parameters. For each test flow rate, this application embodiment measures the magnetic signal response (amplitude) of bacterial colonies under different combinations of external magnetic field frequencies and metal shielding coefficients. M With phase The magnetic signal response is used as the characteristic of the penetrating magnetic signal under the corresponding parameter combination. Specifically, the embodiments of this application adopt a fixed single flow rate + magnetic field frequency and metal shielding coefficient full combination method: first, multiple sets of gradient test flow rates are set, and for each independent test flow rate, different external magnetic field frequencies and different metal shielding coefficients are matched and combined in pairs to form multiple sets of "magnetic field frequency-metal shielding coefficient" test conditions; under each condition, the magnetic signal response of bacterial clusters is measured to obtain the penetrating magnetic signal characteristics corresponding to the flow rate and the parameter combination, and finally, based on the results of all combinations under all test flow rates, the quantitative relationship of the four is constructed.

[0053] Furthermore, addressing the signal attenuation and nonlinear response issues of biomagnetic probes in complex engineering environments such as tunnels containing metal segments and reinforced concrete, this application's embodiments optimize key technologies through multi-dimensional calibration and modeling: First, a multi-parameter coupling correction model is constructed to decouple multiple physical fields. To address the interference of the skin effect and shielding effect of metallic media such as tunnel reinforcement and support structures on bacterial magnetic signals, a four-dimensional lookup table or mathematical model including the metal shielding coefficient is established to separate environmental interference from the effective flow velocity response signal, avoiding flow velocity misjudgment caused by metal shielding. Second, the nonlinear rheological-magnetic response characteristics of the bioprobe are quantified, clarifying the response law of magnetic bacteria that differs from linear Hall elements, determining the correlation mechanism between flow velocity threshold and bacterial cluster arrangement, characterizing the sensitive and saturation ranges of magnetic signals as flow velocity changes, and constructing a precise quantitative magnetic signal-flow velocity-viscosity (MFV) model. The first function relationship enables accurate quantitative inversion of the velocity vector; the second function is to optimize the frequency domain based on multiple external magnetic field frequencies, analyze the differences in metal medium penetration characteristics and bacterial excitation response of magnetic fields at different frequencies, and screen out the working frequency with the best signal-to-noise ratio, so as to maximize the response intensity of the biological probe while minimizing metal shielding interference.

[0054] It should be noted that the "penetrating magnetic signal characteristic" proposed in this application is a complex vector parameter containing amplitude and phase information. The calibration relationship constructed by it essentially includes two dimensions of physical response mechanisms: First, a shielding correction mechanism based on amplitude attenuation: for the electromagnetic shielding effect (skin effect) of metallic media, it mainly utilizes the nonlinear relationship between the magnetic signal amplitude attenuation rate and the metal shielding coefficient to compensate and correct the signal intensity after penetrating the metallic obstacle; Second, a rheological response mechanism based on phase hysteresis: for the rotational resistance characteristics of the biomagnetic probe under fluid shearing, it mainly utilizes the dynamic response relationship between the magnetic signal phase hysteresis and the fluid shear rate (i.e., the faster the flow rate, the larger the hysteresis angle of the bacterial magnetic moment following the external field) to achieve high-sensitivity inversion of macroscopic flow velocity. Therefore, the "penetrating magnetic signal characteristic-metal shielding coefficient-fluid shear rate-macroscopic flow velocity relationship" constructed in this application is essentially a multi-parameter coupled calibration model that combines the amplitude compensation equation and the phase response equation. Furthermore, for the sake of simplicity, when describing the overall inversion logic, it is collectively referred to as the "penetrating magnetic signal characteristic" calibration; when describing the specific flow velocity sensitivity, it specifically refers to the "magnetic signal phase hysteresis".

[0055] Furthermore, in order to adapt to the diversity of underground engineering environments, this application embodiment constructs a multi-parameter coupling calibration model containing two specific forms of "magnetic-fluid-field" based on the different monitoring objects and media environments: (1) For engineering scenarios with metal support structures (such as behind shield tunnel walls and underground pipe corridors), this application embodiment mainly constructs a calibration equation of "penetrating magnetic signal characteristics - metal shielding coefficient - fluid shear rate - macroscopic flow velocity". In this scenario, the "metal shielding coefficient" is introduced to correct the electromagnetic shielding and eddy current loss generated by reinforced concrete or metal pipe segments, and the shear response of the biological probe is mapped to the macroscopic average flow velocity in the channel; (2) For geological scenarios with natural rock and soil media (such as earth-rock dam foundations and groundwater pollution plumes), this application embodiment mainly constructs a calibration equation of "magnetic signal characteristics - media permeability - microscopic pore flow velocity". In this scenario, the "media permeability" (or porosity) parameter is introduced to characterize the obstruction effect of complex pore networks on the movement path of biological probes, and the shear response of biological probes is mapped to the microscopic real flow velocity at the pore scale. Therefore, the above two calibration equations are essentially specific expressions of the "environmental response mechanism of biomagnetic probe" under different boundary conditions in the embodiments of this application. In practical applications, the appropriate calibration model can be selected for parameter inversion based on the geological data or engineering drawings of the area to be tested.

[0056] Furthermore, considering the unique characteristics of underground engineering (especially tunnel environments with metal support structures), the calibration process in this application embodiment includes two temporally independent but functionally complementary physical steps: First, this application embodiment performs environmental static background field calibration (background subtraction), that is, before injecting the biomagnetic probe, a "reinforcing mesh static background field calibration" is carried out on the entire tunnel ring. This step aims to obtain the baseline of the inherent magnetic field distribution formed by the superposition of reinforced concrete segments, metal support structures, and the geomagnetic field, which is used in subsequent real-time monitoring through differential calculations (…). The first step involves eliminating constant background interference and extracting the net magnetic anomaly signal generated solely by the biological probe. The second step, in this embodiment, involves calibrating the signal's dynamic transmission characteristics (quantitative inversion). This involves analyzing the extracted net magnetic anomaly signal using a pre-constructed calibration equation of "penetrating magnetic signal characteristics - metal shielding coefficient - fluid shear rate - macroscopic flow velocity." This step aims to solve two core problems: first, compensating for the amplitude attenuation of the net signal when penetrating the steel mesh (skin effect) through the metal shielding coefficient; and second, inverting the compensated signal strength / phase into a macroscopic flow velocity vector through the fluid shear rate relationship. Thus, the two calibration processes correspond to the two key stages of "signal-to-noise ratio improvement (background removal)" and "physical quantity quantification (flow velocity calculation)," together forming the complete data processing chain for high-precision imaging in this embodiment.

[0057] Through the above calibration relationship, quantitative compensation for the magnetic shielding effect in complex engineering environments is achieved. Specifically, in response to the attenuation interference of magnetic signals caused by metal support structures, which are widely present in underground engineering (such as shield tunnels), this application embodiment introduces a correction factor called "metal shielding coefficient" to construct a multi-parameter coupled calibration model. This effectively eliminates the nonlinear distortion effect of ferromagnetic media on biological probe signals, significantly improving the anti-interference capability and absolute accuracy of velocity inversion under strong metal interference environments. The rheological dynamic response benchmark of the biomagnetic probe is established. Specifically, a nonlinear mapping relationship from microscopic fluid shear rate to macroscopic magnetic signal response is established, overcoming the problem of inconsistent response sensitivity of biological probes in different velocity ranges. This provides a reliable mathematical model and physical benchmark for the subsequent accurate inversion of weak biomagnetic anomaly signals into underground velocity vector fields.

[0058] like Figure 3 As shown, Figure 3 This is a schematic diagram of the magnetic signal characteristics versus flow velocity quantitative calibration curve provided according to an embodiment of this application. This embodiment of the application constructs the penetration magnetic signal characteristics based on experimental data related to the penetration magnetic signal characteristics corresponding to various parameter combinations at all test flow velocities, combined with a Langevin function correction model. M , - Metal shielding coefficient ( S - Fluid shear rate ( γ - Macroscopic flow velocity ( v The quantitative constitutive equation of the magnetic signal is used to establish the physical basis for the transformation of the magnetic signal into the velocity field.

[0059] As one possible approach, in addition to establishing a physical mapping formula for "magnetic signal-shear stress", this application embodiment can also employ data-driven machine learning algorithms to collect a large number of magnetic response spectra under different flow velocity modes and metal shielding conditions, train convolutional neural networks or recurrent neural networks, establish a nonlinear mapping relationship between the time-frequency characteristics of the magnetic field and the flow velocity vector field, and realize end-to-end intelligent identification of the flow velocity field. On the other hand, the magnetic data and high-density electrical resistivity data of this application embodiment are jointly constrained and inverted. The electrical resistivity method is used to determine the macroscopic contour of the aquifer (resistivity anomaly), and the magnetic resistivity method is used to determine the core path of the flow (flow velocity anomaly). Cross-validation is used to improve the uniqueness of the solution and eliminate the multi-solution error of a single geophysical exploration method.

[0060] Furthermore, this application embodiment conducts a non-invasive evaluation, using a permeability sensitivity test to ensure that the permeability loss rate of the medium after bacterial fluid injection is within the allowable range, proving that the method has no significant impact on the original seepage field.

[0061] This effectively eliminates the interference of multi-parameter coupling on the magnetic signal and significantly improves the accuracy of inverting fluid dynamic parameters from the characteristics of penetrating magnetic signals.

[0062] Furthermore, in order to achieve ecological safety management after magnetotactic bacterial tracing detection, the bacteria need to be treated.

[0063] Optionally, in some embodiments, after obtaining the imaging results of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix, the method further includes: placing the target medium model for magnetotactic bacterial degradation and obtaining the survival rate of the degraded magnetotactic bacteria, and / or injecting an environmentally friendly antibacterial agent or oxidant into the target medium model and obtaining the survival rate of the treated magnetotactic bacteria; if the survival rate of the degraded magnetotactic bacteria is lower than a preset threshold, or the survival rate of the treated magnetotactic bacteria is lower than a preset threshold, it is determined that the preset safety conditions are met.

[0064] The preset threshold can be a threshold set by the user, a threshold obtained through a limited number of experiments, or a threshold obtained through a limited number of computer simulations. The preset security conditions can be conditions set by the user, conditions obtained through a limited number of experiments, or conditions obtained through a limited number of computer simulations.

[0065] Specifically, after the test, the embodiment of this application is a groundwater environment harmless treatment process after the magnetotactic bacteria tracer has completed its detection task. Two methods are used to achieve the inactivation and degradation of magnetotactic bacteria: one is to rely on the natural biodegradation characteristics of magnetotactic bacteria to make them die naturally and complete decomposition within a few days to a few weeks; the other is to inject specially made environmentally friendly antibacterial agents or oxidants into the strata to achieve rapid inactivation of magnetotactic bacteria.

[0066] Therefore, it is possible to effectively avoid long-term biological pollution or adverse ecological impact on the groundwater environment caused by tracers after the exploration is completed, thus meeting the requirements of green exploration.

[0067] To facilitate a better understanding of the high-precision magnetic imaging method for underground dominant flow channels proposed in the embodiments of this application, the following is combined with... Figures 4-6 Further explanation is needed.

[0068] like Figure 4 As shown, Figure 4This is a comparative schematic diagram of the imaging of a related technical detection method provided according to an embodiment of this application and the method of this application embodiment. As shown in the figure, the related technology uses high-frequency electromagnetic signals, which are easily affected by natural complex media and metal shielding structures, forming detection blind zones. After the traditional tracer is injected, the path is in a black box state, and monitoring can only be carried out at the outlet end, which cannot achieve full-process detection of underground flow channels. The embodiment of this application achieves full-domain penetration through low-frequency magnetic fields. Combined with magnetotactic bacteria tracer fluid, the dominant flow channel containing magnetotactic bacteria can be tracked in full-process visualization, breaking through the shielding and black box limitations of the related technology, and realizing accurate and full-process detection of underground fluid transport paths. Thus, the embodiment of this application solves the problems of detection blind zones and low quantitative characterization accuracy of the hidden flow field behind the wall in environments with strong metal shielding such as shield tunnels; solves the problems of the deep transport obstruction and easy physical blockage of traditional solid tracers in complex porous media; solves the problems of low signal-to-noise ratio and inability to effectively eliminate static structural background interference of existing geophysical exploration methods; and solves the problems of existing monitoring methods being unable to distinguish between static and dynamic water bodies and unable to quantitatively characterize microscopic flow velocity vectors.

[0069] On the one hand, such as Figure 5 As shown, Figure 5 This is a flowchart of a high-precision magnetic imaging method for underground dominant flow channels according to an embodiment of this application. The high-precision magnetic imaging method for underground dominant flow channels includes the following steps: S501, Cultivation and Functional Modification of Magnetotactic Bacterial Tracer Fluids.

[0070] S502, construction of different types of detection scenarios and physical models.

[0071] S503, Active Source Magnetic Probe System Established.

[0072] S504, Calibration Test and Relationship Establishment.

[0073] S505, tracer injection and dynamic monitoring.

[0074] S506, Flow Field Inversion and Channel Imaging.

[0075] S507, Environmental and Ecological Safety Control.

[0076] On the other hand, such as Figure 6 As shown, Figure 6This is a schematic diagram of the high-precision magnetic imaging system for underground dominant flow channels proposed in the embodiments of this application. As shown in the figure, the system injects a tracer containing biological probes into the underground medium through an injection module. Relying on an artificial magnetic field guiding module (composed of surface / well coils), controllable magnetic lines of force are generated to guide the biological probes to actively migrate along the magnetic lines of force. The magnetic detection array captures underground magnetic signals in real time. After the collected signals are preprocessed by the data acquisition and processing unit, they are transmitted to the inversion imaging workstation to complete the inversion imaging of the underground flow field or dominant flow channels, thereby realizing the accurate detection and visualization of underground fluid transport paths.

[0077] Therefore, addressing the issue of severe signal attenuation caused by the "Faraday cage" effect in strong metal shielding environments such as tunnel lining segments and reinforced concrete dams, traditional high-density electrical resistivity tomography (EDS) and high-frequency ground-penetrating radar (GPR) are susceptible to damage. This application utilizes the excellent penetration characteristics of low-frequency magnetic fields into concrete and non-ferromagnetic media, combined with magnetic biological probes, to effectively overcome the detection blind spots behind shielding layers using conventional methods. By actively emitting a low-frequency modulated magnetic field, this application can penetrate metal mesh structures, achieving efficient and non-destructive detection of grouting voids, leakage channels, and deep soil and rock hazards behind tunnel walls. This significantly improves the detection depth and signal recognition capability in complex engineering environments such as those with strong metal shielding, and enables penetration of the flow field behind concealed structural walls. This invention addresses the limitations of traditional chemical or isotope tracing techniques, which primarily calculate macroscopic average flow velocity by monitoring the transport time of tracers between two points. These techniques struggle to reflect spatial distribution differences and transient changes within the flow field. This application establishes a physical mapping model of "magnetic signal phase lag / amplitude attenuation - fluid shear stress," utilizing the microscopic perturbation mechanism of fluid shear force on the directional alignment of magnetotactic bacteria. This transforms the dynamic shear state of fluid flow into a quantifiable magnetic signal, enabling the detection results to reflect the local instantaneous flow velocity characteristics at specific locations. This provides a more direct physical basis for accurately identifying the topology of dominant flow channels, overcoming the limitations of traditional tracing techniques that rely on the "input-output" time difference to extrapolate average flow velocity. This invention overcomes the limitations of traditional passive tracers, enabling direct characterization of in-situ fluid dynamics in underground flow fields. Addressing the issues of traditional solid particle tracers (such as ordinary nano-iron powder) relying entirely on water flow for transport and being prone to physical interception or sedimentation at narrow pore throats in heterogeneous soil and rock media, leading to signal attenuation at deeper depths, this application utilizes the flagellar-driven mechanism of magnetotactic bacteria. This endows the probe with the ability to actively traverse obstacles and avoid adsorption. This biological autonomous mobility effectively reduces the risk of physical blockage. Compared to traditional passive tracer particles, it can penetrate deeper into more complex micro-fracture networks, thereby obtaining underground flow field information with a wider detection range and stronger representativeness. This improves the transport performance of traditional particulate tracers in dense porous media and combines the advantages of biological probes. The advantages of active transport and the high sensitivity of magnetic detection: Addressing the problem that traditional geophysical methods struggle to effectively distinguish weak flowing fluid signals from strong static structural (such as steel reinforcement and rock mass) background signals, this application's embodiments modify the tracer fluid with biomagnetism, making it a dynamic signal source modulated by an external magnetic field. Utilizing lock-in amplification and frequency domain filtering techniques, based on the specific frequency domain modulation characteristics of flow shear on magnetic signals, effective separation (decoupling) of the target fluid signal from environmental static background noise is achieved. This significantly improves the detection signal-to-noise ratio in complex engineering environments, solves the problem of extracting weak flowing signals in static background noise environments, and enables high signal-to-noise ratio target identification under complex interference conditions.

[0078] Further explanation will be provided in conjunction with specific embodiments.

[0079] For example, the target medium model is a physical model of piping in the foundation of an earth-rock dam. Considering the characteristics of the reservoir's water environment and the need for long-distance transport, this application uses Magnetospirillum magneticum AMB-1 (AMB-1), a bacterium with strong magnetotropy and fast migration speed (>40 μm / s), as a biological probe. It is amplified and cultured to the logarithmic growth phase under oxygen-rich conditions, and then concentrated by centrifugation to prepare a product with a concentration of [missing information]. The suspension was further biochemically matched with the base solution. A low-mineralization buffer solution with the same ionic strength as the reservoir water was used as the base solution, and 5 mM sodium succinate was added as a chemotactic inducer. The chemotaxis of bacteria to carbon sources was used to guide their active migration to the depth of the seepage channel. At the same time, the magnetic response curve of the bacterial solution was monitored to ensure the uniformity of the magnetic moment of the bacterial cluster (M). sat It meets the detection requirements and maintains highly active flagellar motility in a simulated groundwater environment. As shown in Table 1, Table 1 contains specific parameters of the magnetotactic bacterial tracer fluid provided according to an embodiment of this application.

[0080] Table 1

[0081] Furthermore, in this embodiment of the application, a physical model of piping in the foundation of an earth-rock dam is constructed. First, a large seepage physical model box of an earth-rock dam (3.0 m × 1.0 m × 1.5 m) is constructed. The model filling material is wide-graded gravel taken from the engineering site. A controllable piping channel with a diameter of about 10 cm is preset at the bottom of the model and surrounded by weakly permeable clay. At the same time, a constant head water supply system is set up upstream of the model to simulate the high water level condition during the flood season (hydraulic gradient i = 0.5). This model aims to simulate the typical geological structure of the dam foundation forming a dominant flow channel under the action of seepage pressure.

[0082] Based on the determined experimental materials and parameters, this application embodiment constructs an active-source magnetic detection system, such as... Figure 7 As shown, Figure 7This is a schematic diagram of a magnetic scanning detection system for piping channels in an earth-rock dam foundation, according to an embodiment of this application. As shown in the diagram, the system consists of four subsystems: a magnetic field excitation system, a model seepage system, a magnetic signal acquisition system, and a data processing system. The magnetic field excitation system lays multiple turns of high-power Helmholtz coils along the dam axis, connecting a low-frequency signal generator and a power amplifier to generate a sinusoidal alternating magnetic field with a frequency of 5 Hz and an intensity of 100 μT. This frequency avoids power frequency interference (50 Hz) and is sufficient to penetrate the dam overburden and drive the bacterial magnetic moments to undergo forced oscillations. The model seepage system uses tracer injection holes located upstream of the dam, injecting bacterial solution at a constant flow rate via a precision peristaltic pump. The magnetic signal acquisition system uses a high-sensitivity triaxial fluxgate sensor array (noise level) arranged in a 5m × 5m grid in the dam's back slope and toe area. The sensor is placed close to the model surface to capture weak secondary magnetic field signals; the data processing system uses a multi-channel data acquisition card to synchronously record the excitation current and magnetic field response signals, and integrates a lock-in amplification algorithm to extract the signal component with the same frequency as the excitation frequency (5Hz) and its phase information.

[0083] Furthermore, prior to the formal experiment, in-situ calibration was performed using a standard sand column channel. First, a media compatibility assessment was conducted to confirm that the change rate of the sand column permeability coefficient after bacterial injection was less than 5%, verifying the low invasiveness of the biological probe. Subsequently, the response of the bacterial colony to a 5Hz magnetic field was measured at different flow rate gradients (0.1-5 cm / s). Therefore, the embodiments of this application fitted and constructed a "magnetic signal phase hysteresis (…)" model. - Fluid shear rate ( γ - Macroscopic flow velocity ( v The quantitative constitutive equation (based on the Langevin function correction model) establishes the physical benchmark for the transformation of magnetic signals into velocity fields.

[0084] Based on this, this embodiment of the application activates the excitation system for continuous monitoring. Before injecting the bacterial solution, background magnetic field data is recorded, showing a stable background phase without abnormal fluctuations. In this embodiment, magnetotactic bacterial fluid is injected upstream. As the bacteria enter the dam foundation with the seepage flow, in the conventional seepage zone (low flow velocity), the bacterial magnetic moments can follow the external magnetic field well, with a small signal phase lag (<5°). When the bacteria migrate to the preset piping channel (high flow velocity zone), the fluid shear force increases significantly, causing a severe decoherence effect in the bacterial magnetic moment alignment. The sensor array captures a sudden phase lag of 30°-40° in the secondary magnetic field signal in a specific coordinate region (corresponding to the piping location inside the model), while the signal amplitude attenuates by approximately 60%.

[0085] This application's embodiments utilize geophysical inversion software to process the collected magnetic field data, employing a differential algorithm to eliminate static geomagnetic field interference and extract dynamic magnetic response components. Based on the constructed "magnetic signal phase lag (… - Fluid shear rate ( γ - Macroscopic flow velocity ( v The quantitative constitutive equation of “” inverts the magnetic parameter (phase, amplitude) matrix of the surface into the underground velocity vector field. The reconstruction result clearly shows a high velocity strip channel with a burial depth of about 12m and a diameter of about 10cm. Its spatial location matches the model’s preset channel with a degree of greater than 90%, achieving accurate positioning of the piping channel.

[0086] Furthermore, this application implemented targeted treatment and ecological safety control. Based on the inversion positioning results, a targeted curtain grouting treatment was simulated, successfully blocking the piping channel. After the experiment, the injection of bacterial solution was stopped. Since the selected AMB-1 strain is a non-pathogenic environmental bacterium, after the nutrient supply was stopped, the bacteria died naturally and degraded into organic matter within a few days. Monitoring showed that the biological indicators of the model effluent quickly recovered to the background level, verifying the environmental and ecological safety of the method.

[0087] Therefore, taking the monitoring of seepage stability of earth-rock dam foundation under high water level during the flood season as the background, the problem of the strong concealment of piping channels inside the dam foundation and the difficulty of traditional monitoring methods to detect small channels and quantitatively characterize flow velocity in the early stage was solved.

[0088] Another example involves a target medium model that is a heterogeneous large sandbox model containing lenses. In this embodiment, magnetotactic spirochetes (AMB-1), which have strong environmental adaptability, are selected as the biological probe. To simulate a groundwater pollution environment, a base solution containing simulated pollutants (500 mg / L sodium chloride as a non-toxic tracer salt) is prepared to maintain the same ionic strength and pH value (pH=7.5) as the in-situ groundwater. In this embodiment, a gentle centrifugation technique is used to resuspend the bacteria in the base solution, and the concentration is adjusted to 10. 8 The key is to maintain the motility of bacteria in a high-mineralization environment: adding a mixture of trace vitamins and minerals ensures that the bacterial flagella do not fall off or become entangled, and using the principle of chemotaxis, serine at a concentration gradient is added to the base solution as a chemotactic inducer to guide the bacteria to preferentially migrate along the high osmotic velocity region, ensuring the long-term migration and targeted enrichment of the tracer in the heterogeneous medium.

[0089] Furthermore, this embodiment constructs a large heterogeneous sand box model containing lenses, with dimensions of 2.0 m × 1.0 m × 1.0 m. This embodiment uses quartz sand of different particle sizes to simulate heterogeneous strata, with medium sand (permeability coefficient K1) as the background medium. Two lens structures are pre-embedded in the center of the model: a low-permeability clay lens (K2 ≤ K1) and a high-permeability coarse sand lens (K3 ≥ K1). Constant head boundaries are set on both sides of the model, and the overall hydraulic gradient (i = 0.01-0.05) is controlled by adjusting the water level difference. This model aims to simulate the complex flow around and dominant flow behavior of pollutants when encountering low-permeability barriers and high-permeability preferential channels. As shown in Table 2, Table 2 lists the specific parameters of the pollution simulation tracer fluid and heterogeneous model provided in this embodiment.

[0090] Table 2

[0091] Based on the determined experimental materials and parameters, this application embodiment constructs a high-precision magnetic scanning detection system, such as... Figure 8 As shown, Figure 8 This is a schematic diagram of a high-precision magnetic scanning detection system according to an embodiment of this application. As shown in the diagram, the detection system consists of four subsystems: a fluid drive system, a sandbox model system, a non-contact magnetic scanning system, and a data inversion system. The fluid drive system uses a multi-channel peristaltic pump to inject a simulated contamination solution mixed with magnetotactic bacteria from upstream of the model at a constant flow rate (1-10 mL / min). The sandbox model system uses a non-magnetic acrylic material for the model housing to avoid metal interference. The non-contact magnetic scanning system uses a high-sensitivity atomic magnetometer with sensitivity superior to [missing information - likely a specific parameter]. The sensor is mounted on a three-dimensional automatic displacement stage and performs non-contact gridding scanning close to the model surface with a step size of 2cm. The data inversion system uses real-time imaging software developed with LabVIEW (Laboratory Virtual Instrument Engineering Workbench) to simultaneously record the displacement stage coordinates and magnetic field data, and construct a three-dimensional spatial distribution map of the magnetic field strength.

[0092] Furthermore, prior to the formal testing, this embodiment of the application utilizes a standard cylindrical sand column for in-situ calibration. First, the magnetic response baseline values ​​of the background medium (medium sand) at different flow velocities are measured; subsequently, tests are conducted in pure clay and pure coarse sand columns respectively, establishing a "magnetic signal characteristics (phase / amplitude) - medium permeability (…)" model. K ) - Micropore flow velocity ( vThe multivariate nonlinear calibration curve of “” is obtained. In particular, for high-permeability coarse sand media, the decoherence threshold of magnetic signal caused by high flow velocity is established as a physical criterion for identifying dominant flow channels.

[0093] Based on this, the embodiments of this application initiate the injection of tracer using a peristaltic pump, while simultaneously activating an 8Hz low-frequency modulated magnetic field for excitation. In the initial diffusion stage, i.e., the laminar flow stage, the embodiments of this application observe a uniform wavefront propagation of the magnetic signal, indicating that the pollutant undergoes uniform Darcy flow in the background sand. In the flow-around stage (encountering a low-permeability lens), when the pollutant plume's frontal surface contacts the clay lens, the magnetic signal is observed to accumulate and intensify on the water-facing side of the lens. Subsequently, the signal streamlines undergo significant deflection, bypassing the lens from both sides, forming a clear shadow area that precisely delineates the spatial boundary of the low-permeability body. In the fingering stage (encountering a high-permeability lens), when the pollutant plume contacts the coarse sand lens, a severe phase lag in the magnetic signal is observed, and the signal region rapidly advances forward, forming a finger-like flow pattern. This directly reflects the sudden increase in fluid velocity and intensified shear within the high-permeability zone.

[0094] Furthermore, in this embodiment of the application, the collected spatiotemporal sequence data is inverted, utilizing the constructed "magnetic signal characteristics (phase / amplitude) - medium permeability (... K ) - Micropore flow velocity ( v The multivariate nonlinear calibration curve of the "" transforms the magnetic field intensity distribution into a micro-velocity vector field. The velocity cloud map generated by the embodiment of this application clearly shows the complex transport path of pollutants around the lens. Specifically, the velocity is close to zero in the low-permeability zone and 3-5 times higher than the background in the high-permeability zone, with a resolution of centimeter level. This verifies that the non-uniformity of the micro-velocity field is the fundamental reason for controlling the diffusion and tailing phenomenon of macro-pollution plume morphology.

[0095] After the experiment, the tracer injection was stopped in this embodiment, and clean water was used for displacement. The biodegradation characteristics of magnetotactic bacteria were utilized to monitor the decay curve of bacterial concentration at the outlet over time. At the same time, a trace amount of oxidant (such as 0.1% H2O2) was injected into the model to simulate the in-situ chemical oxidation remediation process, quickly inactivating residual bacteria and ensuring that there was no biological contamination residue in the sand box medium after the experiment, meeting the laboratory waste discharge standards.

[0096] This solves the problem of the strong heterogeneity of aquifer media (such as those containing lenses), the complex diffusion path of pollution plumes, and the difficulty of identifying the micro-flow field morphology of the pollution front using traditional sampling methods in the remediation of chemical plant sites and groundwater pollution.

[0097] Another example involves a target medium model that is a physical model of seepage behind the tunnel wall during the operational phase. This application's embodiment targets the conventional groundwater environment (neutral pH, low organic matter) and seepage characteristics of micro-fractures behind the tunnel wall during the operational phase. Magnetotactic spirochetes (AMB-1), known for their strong environmental adaptability and fast migration speed, are selected as probes. To ensure the tracer can penetrate deep micron-level fissures with weak seepage, a low-viscosity, low-mineralization buffer solution (simulating natural groundwater composition) is used as the base liquid to construct a "high-permeability, high-activity" tracer system. Simultaneously, the biochemical parameters of the base liquid are adjusted by adding trace amounts of chelated iron and a carbon source (sodium lactate) to maintain the bacteria's flagellar motility activity for 48 hours under nutrient-poor conditions. Furthermore, the key lies in improving transportability: a trace amount of biosurfactant (rhamnolipid) is added before injection to reduce the non-specific adsorption of bacteria to soil particles and concrete walls, ensuring that bacteria can respond to weak hydraulic gradients and migrate long distances to the seepage convergence point.

[0098] Furthermore, in this embodiment of the application, a physical model of leakage behind the tunnel wall during the operational period is constructed, and standard C50 (strength grade) reinforced concrete segments are selected as the shielding medium (thickness 350mm, with internal double layers). The tunnel wall is reinforced with 16mm threaded steel mesh (150mm x 150mm mesh spacing). This embodiment fills the backwater side of the tunnel lining with saturated sand and pre-defines different types of hazard models: including surface seepage with low flow velocity (simulating chronic seepage at tunnel joints), concentrated water inflow channels with high flow velocity (simulating fissure seepage), and saturated still water zones (simulating the background aquifer). This model aims to simulate a real strong metal shielding environment and verify the penetration of low-frequency magnetic fields and the ability to identify different seepage velocity levels. As shown in Table 3, Table 3 presents the parameters of the tunnel wall back-wall detection tracer fluid and system according to an embodiment of this application.

[0099] Table 3

[0100] Based on the determined experimental materials and parameters, this application embodiment constructs a vehicle-mounted tunnel wall-mounted magnetic scanning observation system, such as... Figure 9 As shown, Figure 9This is a schematic diagram of a vehicle-mounted tunnel wall back magnetic scanning observation system according to an embodiment of this application. As can be seen from the figure, the system consists of four subsystems: a micro-destructive injection system, a tunnel segment system, a mobile magnetic scanning system, and a data imaging system. The micro-destructive injection system utilizes existing pre-reserved grouting holes or hoisting holes on the tunnel segments, installs customized water-stopping injection heads, and injects tracer bacterial solution into the soil behind the tunnel wall under low pressure (<0.2MPa), allowing it to diffuse naturally with the groundwater seepage field; the tunnel segment system is an actual operating tunnel or the aforementioned physical model, serving as the detection object and signal shielding layer; the mobile magnetic scanning system is integrated into the automatic scanning platform of the tunnel inspection vehicle, equipped with a high-power low-frequency transmitting coil and a differential magnetic sensor array. The transmitting coil generates a guiding magnetic field with a frequency of 12Hz and an intensity of 200μT. The key parameter of 12Hz is chosen because it can effectively penetrate the electromagnetic shielding of the tunnel segment's steel mesh while ensuring sufficient signal resolution, directly acting on the water behind the tunnel wall; the data imaging system uses an on-board industrial control computer to process sensor data in real time, integrates mileage encoder signals to achieve spatial positioning, and performs continuous scanning at a cruising speed of 0.5m / s.

[0101] Furthermore, this embodiment of the application performs full-ring calibration and subtraction of the static background field of the steel reinforcement mesh. Given that the uneven distribution of the steel reinforcement mesh in the tunnel segments generates a periodic static induced magnetic field, a blank scan calibration is required before injecting the tracer. This embodiment of the application measures the distribution characteristics of the background magnetic field throughout the tunnel ring, establishes a tunnel reference magnetic texture database, and constructs a differential filtering algorithm to subtract this reference background in real time during subsequent re-measurement scans, eliminating static interference from the steel reinforcement and segment bolts, and highlighting the dynamic response caused by fluid shear behind the tunnel wall.

[0102] Based on this, the embodiments of this application perform dynamic scanning and feature recognition along the tunnel axis. Two hours after injecting the tracer, the inspection vehicle was started and moved along the tunnel axis to continuously excite and collect signals behind the wall. Based on the difference in the response of bacterial clusters to different fluid dynamic states, the secondary magnetic field characteristics were extracted by lock-in amplification technology to identify the following three typical working conditions: (1) Bacteria are randomly distributed or slowly diffused with still water in areas without leakage or in still water. They are well oriented and arranged under the control of external magnetic field. The measured signal shows a quasi-static characteristic with high amplitude and low phase lag. There is no obvious abnormality after superimposing with the reference background. (2) In the leakage convergence area, due to the presence of water flow converging towards cracks or joints behind the wall, the flow velocity suddenly increases to form a high shear zone. The bacterial cluster undergoes violent overturning and decoherence. The detector captures a 12Hz signal with a significant phase lag peak and a secondary field amplitude depression, accurately indicating the source direction of the leakage water. (3) If there is a high-velocity piping channel in the concentrated water inrush channel, the strong turbulent shearing causes the bacterial magnetic signal to be completely decoherent (disordered), showing a local magnetic signal "black hole" or severe dynamic noise anomaly.

[0103] Furthermore, this embodiment utilizes differential inversion imaging technology to generate a unfolded map of the seepage field behind the tunnel wall. Spatial registration and differential processing are performed on the acquired time-series data. Based on the aforementioned calibration background, static strong interference from the tunnel segment reinforcement is eliminated, and the remaining dynamic magnetic anomaly signals are inverted into the microscopic velocity vector distribution of the fluid behind the tunnel wall, generating a unfolded map of the seepage field behind the tunnel wall for the entire circumference. Figure 9 As can be seen, the bright warm-colored area (high phase lag area) in the figure is the convergence path or source channel of the leaking water, which enables accurate location of the hidden leakage source behind the wall.

[0104] After the test, based on the positioning results of the unfolded diagram, the embodiments of this application guide the construction personnel to perform targeted minimally invasive drilling and grouting in the core area of ​​the abnormal signal. After the grouting and plugging are completed, the scanning system is used again for retesting. If the original high phase lag dynamic signal disappears and turns into a static background signal consistent with the surroundings, it is determined that the leakage channel has been effectively blocked, realizing the closed-loop control of "detection-treatment-acceptance".

[0105] Therefore, for shield tunnels of subways or highways that are already in operation, this method solves the problem that the "Faraday cage" shielding effect formed by the dense steel mesh inside the tunnel segments makes it impossible to accurately locate the tiny leakage paths and water collection channels behind the tunnel wall.

[0106] The high-precision magnetic imaging method for underground dominant flow channels proposed in this application involves controlling the injection of magnetotactic bacterial tracer fluid into a target medium model and collecting magnetic field data throughout the seepage process. The magnetic field data is processed to obtain a magnetic parameter matrix. Based on the relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are then obtained from the flow velocity vector field matrix. This solves the problems in related technologies, such as the inability to penetrate metal shielding structures, susceptibility to solid particle blockage, restricted transport, environmental background noise interference, and the inability to eliminate static background effects.

[0107] Next, referring to the accompanying drawings, a high-precision magnetic imaging device for underground dominant flow channels according to an embodiment of this application is described.

[0108] Figure 10 This is a block diagram of a high-precision magnetic imaging device for underground dominant flow channels according to an embodiment of this application.

[0109] like Figure 10 As shown, the high-precision magnetic imaging device 10 for underground dominant flow channels includes: a construction module 100, an acquisition module 200, and an imaging module 300.

[0110] Module 100 is constructed to meet the requirements of high-precision magnetic imaging of underground dominant flow channels, prepare magnetotactic bacterial tracer fluid, and build a target medium model. The acquisition module 200, based on a preset underground flow field magnetic detection platform, controls the injection of magnetotactic bacteria tracer fluid into the target medium model and acquires magnetic field data of the entire seepage process. Based on a preset geophysical inversion algorithm, the magnetic field data is processed to obtain a magnetic parameter matrix. The imaging module 300, based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, inverts the magnetic parameter matrix into a flow velocity vector field matrix, and obtains the imaging results of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix according to the type of the target medium model.

[0111] According to one embodiment of this application, the target medium model is a natural rock and soil seepage model, and the imaging module 300 is specifically used for: Based on the natural rock and soil seepage model, a strip-shaped channel diagram that satisfies the preset flow velocity is generated according to the velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the strip channel diagram with preset flow velocity.

[0112] According to one embodiment of this application, the target medium model is an indoor standard calibration model, and the imaging module 300 is specifically used for: Based on the indoor standard calibration model, a flow velocity cloud map is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the flow velocity cloud map.

[0113] According to one embodiment of this application, the target medium model is a metal-shielded environment model, and the imaging module 300 is specifically used for: Based on the metal shielding environment model, the unfolded diagram of the seepage field behind the tunnel's entire annular wall is obtained according to the velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model were obtained based on the unfolded diagram of the seepage field behind the tunnel's full annular wall.

[0114] According to one embodiment of this application, the imaging module 300 is further configured to: Determine multiple test flow rates, multiple applied magnetic field frequencies, and multiple metal shielding coefficients; Based on each test flow rate, the magnetic signal response of the bacterial cluster was measured under the combined conditions of multiple external magnetic field frequencies and multiple metal shielding coefficients, and the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow rate were obtained. Based on the penetrating magnetic signal characteristics corresponding to each parameter combination at each test flow rate, a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity is constructed.

[0115] According to one embodiment of this application, after obtaining the imaging results of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix, the imaging module 300 is further configured to: The target medium model is placed in a magnetotactic bacteria degradation environment and the survival rate of the degraded magnetotactic bacteria is obtained; and / or, an environmentally friendly antibacterial agent or oxidant is injected into the target medium model and the survival rate of the treated magnetotactic bacteria is obtained. If the survival rate of magnetotactic bacteria after degradation is lower than a preset threshold, or if the survival rate of magnetotactic bacteria after treatment is lower than a preset threshold, the preset safety conditions are deemed met.

[0116] It should be noted that the foregoing explanation of the high-precision magnetic imaging method for underground dominant flow channels also applies to the high-precision magnetic imaging device for underground dominant flow channels in this embodiment, and will not be repeated here.

[0117] The high-precision magnetic imaging device for underground dominant flow channels proposed in this application controls the injection of magnetotactic bacterial tracer fluid into a target medium model and collects magnetic field data throughout the seepage process. The magnetic field data is processed to obtain a magnetic parameter matrix. Based on the relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are then obtained from the flow velocity vector field matrix. This solves the problems in related technologies, such as the inability to penetrate metal shielding structures, susceptibility to solid particle blockage, restricted transport, environmental background noise interference, and the inability to eliminate static background effects.

[0118] Figure 11 This is a schematic diagram of an electronic device provided in an embodiment of the present invention. The electronic device may include: The memory 1101, the processor 1102, and the computer program stored on the memory 1101 and executable on the processor 1102.

[0119] When the processor 1102 executes the program, it implements the high-precision magnetic imaging method for underground dominant flow channels provided in the above embodiments.

[0120] Furthermore, electronic devices also include: Communication interface 1103 is used for communication between memory 1101 and processor 1102.

[0121] The memory 1101 is used to store computer programs that can run on the processor 1102.

[0122] The memory 1101 may include high-speed RAM (Random Access Memory) memory, and may also include non-volatile memory, such as at least one disk storage.

[0123] If the memory 1101, processor 1102, and communication interface 1103 are implemented independently, then the communication interface 1103, memory 1101, and processor 1102 can be interconnected via a bus to complete communication between them. The bus can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Extended Industry Standard Architecture) bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 11 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0124] Optionally, in a specific implementation, if the memory 1101, processor 1102, and communication interface 1103 are integrated on a single chip, then the memory 1101, processor 1102, and communication interface 1103 can communicate with each other through an internal interface.

[0125] The processor 1102 may be a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement embodiments of the present invention.

[0126] This invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described high-precision magnetic imaging method for underground dominant flow channels.

[0127] This application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the steps in any of the above embodiments of the high-precision magnetic imaging method for underground dominant flow channels.

[0128] 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 application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0129] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. 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.

[0130] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A high-precision magnetic imaging method for underground dominant flow channels, characterized in that, include: In response to the need for high-precision magnetic imaging of underground dominant flow channels, a magnetotactic bacterial tracer fluid was prepared and a target medium model was constructed. Based on a pre-set underground flow field magnetic detection platform, the magnetotactic bacterial tracer fluid is injected into the target medium model, and magnetic field data of the entire seepage process is collected. Based on a pre-set geophysical inversion algorithm, the magnetic field data is processed to obtain a magnetic parameter matrix. Based on the preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the magnetic parameter matrix is ​​inverted into a flow velocity vector field matrix. Based on the type of the target medium model, the imaging results of the underground dominant flow channel of the target medium model are obtained according to the flow velocity vector field matrix.

2. The method according to claim 1, characterized in that, The target medium model is a natural rock and soil seepage model. The imaging results of the subsurface dominant flow channels of the target medium model, obtained based on the type of the target medium model and the flow velocity vector field matrix, include: Based on the natural rock and soil seepage model, a strip-shaped channel diagram that satisfies the preset flow velocity is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the strip-shaped channel diagram of the preset flow velocity.

3. The method according to claim 1, characterized in that, The target medium model is an indoor standard calibration model. The imaging results of the subsurface dominant flow channels of the target medium model, obtained based on the type of the target medium model and the flow velocity vector field matrix, include: Based on the indoor standard calibration model, a flow velocity cloud map is generated according to the flow velocity vector field matrix; The imaging results of the underground dominant flow channels of the target medium model are obtained based on the flow velocity cloud map.

4. The method according to claim 1, characterized in that, The target medium model is a metal-shielded environment model. The imaging results of the subsurface dominant flow channels of the target medium model, obtained based on the type of the target medium model and the flow velocity vector field matrix, include: Based on the metal shielding environment model, the unfolded diagram of the seepage field behind the tunnel's entire annular wall is obtained according to the velocity vector field matrix. The imaging results of the underground dominant flow channels of the target medium model are obtained based on the unfolded diagram of the seepage field behind the tunnel's full annular wall.

5. The method according to claim 1, characterized in that, Before inverting the magnetic parameter matrix into a velocity vector field matrix based on a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, the process also includes: Determine multiple test flow rates, multiple applied magnetic field frequencies, and multiple metal shielding coefficients; Based on each test flow rate, the magnetic signal response of the bacterial cluster was measured under the combined conditions of multiple external magnetic field frequencies and multiple metal shielding coefficients, so as to obtain the penetrating magnetic signal characteristics corresponding to each parameter combination under each test flow rate. The preset relationship between the penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity is constructed based on the penetrating magnetic signal characteristics corresponding to each parameter combination at each test flow rate.

6. The method according to claim 1, characterized in that, After obtaining the imaging results of the subsurface dominant flow channels of the target medium model based on the velocity vector field matrix, the method further includes: The target medium model is placed in a magnetotactic bacteria degradation environment and the survival rate of the degraded magnetotactic bacteria is obtained; and / or, an environmentally friendly antibacterial agent or oxidant is injected into the target medium model and the survival rate of the treated magnetotactic bacteria is obtained. When the survival rate of the degraded magnetotactic bacteria is lower than a preset threshold, or when the survival rate of the treated magnetotactic bacteria is lower than the preset threshold, the preset safety conditions are determined to be met.

7. A high-precision magnetic imaging device for underground dominant flow channels, characterized in that, include: The module was constructed in response to the need for high-precision magnetic imaging of underground dominant flow channels, to prepare magnetotactic bacterial tracer fluid and build a target medium model; The acquisition module, based on a preset underground flow field magnetic detection platform, controls the injection of the magnetotactic bacterial tracer fluid into the target medium model and acquires magnetic field data of the entire seepage process. Based on a preset geophysical inversion algorithm, the magnetic field data is processed to obtain a magnetic parameter matrix. The imaging module, based on a preset relationship between penetrating magnetic signal characteristics, metal shielding coefficient, fluid shear rate, and macroscopic flow velocity, inverts the magnetic parameter matrix into a flow velocity vector field matrix, and obtains the imaging results of the underground dominant flow channel of the target medium model based on the flow velocity vector field matrix according to the type of the target medium model.

8. An electronic device, characterized in that, include: A memory, a processor, and a computer program stored in the memory and executable on the processor, the processor executing the program to implement the high-precision magnetic imaging method for underground dominant flow channels as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, The program is executed by a processor to implement the high-precision magnetic imaging method for underground dominant flow channels as described in any one of claims 1-6.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the high-precision magnetic imaging method for underground dominant flow channels as described in any one of claims 1-6.

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