Accurate positioning method for underground deep vertical metal structure

Abstract

The invention discloses an accurate positioning method for an underground deep vertical metal structure. The method comprises the following steps: delimiting a ground to-be-measured area and gridding measuring points, constructing a drill hole penetrating into an underground phreatic bed and below the underground phreatic bed in the area, putting a positive electrode in a pair of power supply electrodes into the drill hole, and putting the other power supply negative electrode to an infinite distance; one of the pair of observation electrodes is connected with the infinite pole of the power supply electrode, and the other observation electrode is in close contact with a ground medium in a to-be-determined area; a power supply electrode and an observation electrode are connected to an electrical prospecting instrument through wires respectively, the potential difference of the ground measuring electrode potential of a to-be-measured area relative to the infinite electrode potential is measured point by point according to measuring points, the coordinate position of an area point corresponding to the potential difference value is recorded, and a geoelectric signal contour map of the to-be-measured area is drawn according to measured data. Therefore, the ground projection center position of the vertical metal structure is determined. The method and device are accurate and convenient in detection and positioning, simple and flexible in construction, low in cost and wide in application range.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, and in particular relates to a method for precise positioning of deep underground vertical metal structures. Background Technology

[0002] Vertical metal structures buried underground, such as steel cages of abandoned pile foundations, oil well pipes, and steel pipe piles, present significant challenges for later location, exploration, and harmless disposal due to their small projected area on the ground and deep burial. Existing ground geophysical exploration methods have obvious limitations in locating such targets: ground-penetrating radar methods suffer from severe attenuation of electromagnetic wave signals in metallic media, limiting their detection depth; seismic exploration methods lack sufficient resolution for small-scale vertical targets; and traditional electrical exploration methods (such as high-density electrical resistivity tomography) suffer from severe volume effects, making it difficult to identify anomalous responses of such small targets from the macroscopic background field. Blindly drilling for exploration is costly, inefficient, and has a low success rate. There is an urgent need for precise location technology for such targets in engineering fields such as subway construction crossing existing factory areas and the investigation of abandoned oil and gas wells. Summary of the Invention

[0003] The main objective of this invention is to provide a method for accurately locating deep underground vertical metal structures that is simple to construct, low in cost, and accurate in positioning.

[0004] Therefore, the present invention provides a method for precise positioning of deep underground vertical metal structures, which uses an electrical resistivity tomography (OTT) instrument for measurement. This OTT instrument includes a pair of power supply electrodes and a pair of observation electrodes, and comprises the following steps: S1. Delineate the area to be measured on the ground and grid it; S2. Drill at least one borehole in the area to be tested, the depth of which reaches below the groundwater level; S3. Using an insulated wire, the positive power supply electrode of a pair of power supply electrodes is dropped below the water surface through the drill hole, and the negative power supply electrode of the pair of power supply electrodes is placed at an infinite distance from the center of the area to be measured. S4. Place one of the pair of observation electrodes at infinity, and move the other observation electrode on the grid measurement points in the area to be measured, while maintaining good electrical contact with the ground medium; S5. Start the electrical exploration instrument, supply current to the ground through the power supply electrode, and use the observation electrode to measure the geoelectric signal of each grid measuring point in the area to be measured relative to the infinity electrode. The geoelectric signal includes potential difference, excitation polarization parameter or induced electromotive force. S6. Record the coordinates of each measuring point and its corresponding geoelectric signal; S7. Based on the measured data, draw a geoelectric signal contour map of the area to be measured. The contour map presents a concentric circle shape centered on a high or low anomaly and spreading outwards. The center of the concentric circle is the center of the projection of the underground vertical metal structure on the ground.

[0005] Specifically, the electrical exploration instrument is a direct current electrical resistivity instrument, and the geoelectric signal is a potential difference.

[0006] Specifically, the electrical exploration instrument is an alternating current electrical instrument, and the geoelectric signal is a potential difference or induced electromotive force.

[0007] Specifically, when using an alternating current method instrument, a coil or magnetic rod is used to measure the electromagnetic field anomaly generated by the underground alternating current field, and an induced electromotive force contour map is drawn for location.

[0008] Specifically, the electrical exploration instrument is a time-domain / frequency-domain induced polarization method instrument, and the geoelectric signal is the induced polarization parameter.

[0009] Specifically, the drilled hole is an angled hole or a directional hole, and its opening position is located inside or outside the area to be tested.

[0010] Specifically, the positive electrode or infinity electrode of the power supply electrode is arranged in a parallel manner using multiple electrodes.

[0011] Specifically, in step S4, the infinity electrode of the observation electrode and the infinity electrode of the power supply electrode share the same electrode.

[0012] Specifically, the maximum diameter or side length of the area to be measured is L, and the distance from the power supply electrode to the center of the ground of the area to be measured is greater than or equal to 5L.

[0013] The metal structures include steel cages for abandoned pile foundations, oil well pipes, and steel pipe piles.

[0014] Specifically, the coordinates of the moving observation electrode can be determined using a total station or GPS.

[0015] The basic principle of this invention is as follows: A high potential is projected using electrodes inserted deep into an underground aquifer. This high potential diffuses and decays outwards. If an exposed metallic medium exists within the diffusion range, the potential at that location will be transmitted to the ground through the equipotential body of the metallic structure. Therefore, a high potential will be projected onto the ground at the location of the vertical metallic structure, and this potential will diffuse and decay outwards from that point. By measuring the distribution map of the ground potential in the area to be determined, the ground projection location of the vertical metallic structure can be determined. This method can be performed using the excited polarization method, which is similar in principle to potential measurement methods. The excited polarization method can be a time-domain method or a frequency-domain method.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Innovative Principle: By extending the power supply electrodes below the water surface to establish a stable artificial electric field, and by cleverly utilizing the good conductivity and equipotential properties of vertical metal structures, the deep electric field signal is "guided" to the surface, forming easily identifiable concentric circle potential or induced polarization anomalies, thus solving the problem of difficult detection of small-scale, deeply buried targets.

[0017] 2. Precise positioning: By measuring the fine distribution of the ground electric field, the target positioning is improved from "regional estimation" to "point projection", and the positioning results are intuitive and accurate.

[0018] 3. High adaptability: It can adapt to complex construction environments by adjusting the drilling position and depth, and is effective for various types of vertical metal structures, with a wide range of applications.

[0019] 4. Economical and efficient: Compared with a large number of blind exploratory boreholes, this invention only requires the construction of one or more small number of boreholes. Combined with rapid ground surveying, the cost is significantly reduced and the efficiency is greatly improved. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the positioning method in Embodiment 1 of the present invention; Figure 2 This is a contour map of the distribution of measured potential or polarizability data in the area to be tested obtained in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the positioning method in Embodiment 2 of the present invention; Figure 4 This is a contour map showing the distribution of measured potential or polarizability data in the area to be tested, obtained in Embodiment 2 of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0024] 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 one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0025] A method for accurately locating deep underground vertical metal structures uses an electrical resistivity tomography (EPT) instrument, which includes a pair of power supply electrodes (transmitting electrodes) and a pair of observation electrodes (receiving electrodes), and comprises the following steps: S1. Delineate the area to be measured on the ground and grid it; S2. Drill at least one borehole in the area to be tested, the depth of which reaches below the groundwater level; S3. Using an insulated wire, the positive power supply electrode of a pair of power supply electrodes is lowered below the water table through the borehole, and the negative power supply electrode of the pair of power supply electrodes is placed at an infinite distance from the center of the area to be measured. By lowering the electrodes below the water table, the property of water to enhance the conductivity of the underground medium is utilized. In a highly conductive medium, the potential decays more slowly, resulting in a better "current collection" effect of the vertical metal pipe.

[0026] S4. Place one of the pair of observation electrodes at infinity, and move the other observation electrode on the grid measurement points in the area to be measured, while maintaining good electrical contact with the ground medium; S5. Start the electrical exploration instrument, supply current to the ground through the power supply electrode, and use the observation electrode to measure the geoelectric signal of each grid measuring point in the area to be measured relative to the infinity electrode. The geoelectric signal includes potential difference, excitation polarization parameter or induced electromotive force. S6. Record the coordinates of each measuring point and its corresponding geoelectric signal; S7. Based on the measured data, draw a geoelectric signal contour map of the area to be measured. The contour map presents a concentric circle shape centered on a high or low anomaly and spreading outwards. The center of the concentric circle is the center of the projection of the underground vertical metal structure on the ground.

[0027] This invention employs electrodes inserted deep into underground aquifers to project a high potential. This high potential diffuses and decays outwards. If an exposed metallic medium exists within the diffusion range, the potential at that location will be transmitted to the ground through the equipotential body of the metallic structure. Therefore, a high potential will be projected onto the ground at the location of the vertical metallic structure, and this potential will diffuse and decay outwards from that point. By measuring the distribution map of the ground potential in the area to be determined, the center position of the vertical metallic structure's ground projection can be determined.

[0028] This invention establishes a stable artificial electric field by inserting the power supply electrode below the water surface. By cleverly utilizing the good conductivity and equipotential properties of vertical metal structures, the deep electric field signal is "guided" to the surface, forming easily identifiable concentric circle potential or induced polarization anomalies, thus solving the problem of difficult detection of small-scale, deeply buried targets.

[0029] In practical design, vertical holes are typically used for power supply drilling. However, in situations where there are buildings or facilities above, angled or directional drilling can be considered to avoid drilling directly above the site. The borehole diameter is usually small and will not affect the observation results. The drilling location can be flexibly selected either inside or outside the area to be determined. The drilling depth can exceed the depth of the vertical metal structure, meaning the power supply point can extend beyond the depth of the vertical metal structure. By supplying power and observing at different depths, the burial depth range of the vertical metal structure can be inferred.

[0030] The specific steps for determining the burial depth range are as follows: Power supply electrodes are applied from deep to shallow depths for observation. When the burial depth of the power supply electrodes is greater than that of the metal structure, an extremely high potential anomaly or an excitation polarization anomaly will appear directly above the vertical metal pipe. The drawn potential contour lines or excitation polarization parameter value contour lines are approximately concentric circles, with the center of the concentric circle being the highest potential point. When the burial depth of the power supply electrodes is less than that of the metal structure, the anomaly is exactly the opposite; an extremely low potential anomaly point is observed directly above. Within the burial depth range of the metal structure, the potential contour line distribution will shift. Therefore, the burial depth of the metal structure can be determined based on the potential distribution.

[0031] Specifically, the maximum diameter or side length of the area to be measured is L, and the distance from the power supply electrode to the center of the ground of the area to be measured is greater than or equal to 5L. The infinity electrode of the pair of electrodes used for receiving measurements can be located in the same position as the transmitting infinity electrode, sharing one electrode, or it can be set up separately, located at the periphery of the maximum diameter (length) of the area to be measured at least 5 times, to ensure good electrode grounding.

[0032] When the method employs potential measurement, the electrical exploration instruments used are either direct current (DC) or alternating current (AC) instruments, used to measure the abnormal electric field distribution generated on the ground by concealed vertical pipes. When the measurement is performed using the induced polarization method, the electrical instruments used are induced polarization instruments, with a basic principle similar to the potential measurement method. This method is used to measure the induced polarization anomalies generated on the ground by concealed vertical pipes. The induced polarization method can be a time-domain method or a frequency-domain measurement method.

[0033] In some feasible implementation schemes, the positive and infinity electrodes used can be two or more, connected in parallel and integrated into the power supply circuit of the electrical exploration instrument. That is, the positive and / or infinity electrodes are arranged in parallel using multiple electrodes. This design, with multiple power supply electrodes connected in parallel, enhances the current and thus strengthens the observed signal.

[0034] When the electrical exploration instrument is a DC electrical resistivity instrument, the geoelectric signal is the potential difference; when the electrical exploration instrument is a time-domain / frequency-domain induced polarization method instrument, the geoelectric signal is the induced polarization parameter. When using a DC electrical resistivity instrument or an induced polarization method instrument for detection and measurement, an extremely high potential anomaly or induced polarization anomaly will appear directly above the vertical metal pipe. This high potential or induced polarization anomaly will attenuate radially outwards, showing a decreasing trend in the potential gradient or induced polarization gradient. If potential contour lines or induced polarization parameter value contour lines are drawn, the contour lines will form concentric circles centered on the ground projection of the vertical metal pipe. The center of the concentric circles indicates the center position of the ground projection of the vertical metal pipe.

[0035] When the electrical exploration instrument is an AC electrical resistivity instrument, the geoelectric signal is a potential difference or induced electromotive force. When using an AC electrical resistivity instrument, a coil or magnetic rod is used to measure the electromagnetic field anomaly generated by the underground AC electric field, and an induced electromotive force contour map is drawn for location. During interpretation, an extremely high induced electromotive force anomaly value will appear directly above the vertical metal pipe. This extremely high anomaly value decays radially in all directions, showing a decreasing trend of induced electromotive force gradient or induced polarization gradient. If the induced electromotive force contour lines are drawn, the contour lines will form concentric circles centered on the ground projection of the vertical metal pipe. In other words, the center of the concentric circles indicates the center position of the ground projection of the vertical metal pipe.

[0036] This application utilizes an electrical exploration instrument comprising at least one pair of power supply electrodes (emitting electrodes) and one pair of observation electrodes (receiving electrodes). The location detection method involves delineating the ground area to be tested, where metallic structures may exist, and gridding the measurement points, with the maximum diameter or side length set to L. At least one power supply borehole is drilled in this area, reaching the groundwater level and below. Using an insulated wire, the positive electrode of the power supply electrode pair is lowered below the water table through the borehole, while the other negative electrode is placed at an infinity distance greater than 5 times L (relative to the center of the test area). One of the observation electrodes is connected to the infinity electrode of the power supply electrode, while the other observation electrode is in close contact with the ground medium within the designated area. The voltage output terminal of the power supply electrode and the voltage input terminal of the receiving electrode are connected to the electrical exploration instrument. The potential difference between the ground electrode potential and the infinity electrode potential in the test area is measured point by point, and the coordinates of the corresponding points are recorded. Interpretation method: Draw a contour map of the potential distribution in the area to be measured. A concentric circle will appear directly above the projection of the vertical metal pipe. The center of the concentric circle is the highest potential anomaly or excitation polarization anomaly value. This high potential or excitation polarization anomaly value decays radially outward to form concentric circles, showing the trend of the potential gradient or excitation polarization gradient decreasing from the maximum value to the surrounding areas. The center of the concentric circle indicates the center position of the ground projection of the vertical metal pipe. Example

[0037] For abandoned oil production pipes, refer to Figure 1 and Figure 2 As shown, an abandoned oil well exists beneath a 10m × 10m area of ​​ground. The well is a 400mm diameter steel pipe, vertically buried at a certain location, with a length exceeding 100m. The goal is to locate and properly dispose of this pipe. The area consists of Quaternary sedimentary strata, with a groundwater level of 12m.

[0038] First, the area to be measured is gridded to form a grid of 0.5m × 0.5m measuring points. Then, the observation electrodes perform potential measurements on these measuring points.

[0039] A DC electrical resistivity tomography (EDT) instrument is used, consisting of a pair of power supply electrodes and a pair of observation electrodes. A power supply borehole is drilled vertically to the center of the area, with a depth of 15m. The positive electrode of the power supply electrode pair is lowered to the bottom of the borehole using an insulated wire, while the negative electrode is placed at an "infinity" distance of 100m from the borehole opening, ensuring good grounding. One of the observation electrodes is connected to the "infinity" pole of the power supply electrode (short-circuited on the instrument panel), and the other observation electrode is placed in good contact with the ground medium within a 10m × 10m area to be determined, for example, by driving a copper rod into the ground. The voltage output terminal of the power supply electrode and the voltage input terminal of the receiving electrode are connected to the EDT instrument, and the two receiving electrodes are connected to the measuring end of the EDT instrument. Turn on the electrical exploration instrument and supply 100V DC power to the ground through the power supply electrode. Move the observation electrode point by point on the ground and measure the potential difference between the ground electrode potential in the test area and the potential of the electrode at infinity. Record the relative coordinate position of the corresponding point in the test area to obtain the coordinate distribution of the ground potential when the ground is powered.

[0040] The interpretation method involves drawing a contour map of the potential distribution in the area to be measured. A concentric circle appears directly above the projection of the vertical metal pipe. The center of the concentric circle is the highest potential anomaly. This high potential anomaly decays radially outward to form concentric circles, showing the potential gradient decreasing from its maximum value to the surrounding areas. The center of the concentric circle indicates the center position of the ground projection of the vertical oil metal pipe. Example

[0041] For the positioning of the pile foundation reinforcement cage, see [reference needed]. Figure 3 and Figure 4 The planned subway line in the city will pass underground through an old steel factory area. After several renovations, the surface area is now a park. There are bored piles 5 to 10 meters underground in this area. The piles have steel cages and metal caps at the bottom. The piles are about 50 meters long and are distributed within a 30m x 50m area on the ground within the park.

[0042] A set of electrical exploration instruments for induced polarization measurement, such as a dual-frequency induced polarization instrument, is used, including a pair of power supply electrodes and a pair of observation electrodes. Considering the inconvenience of drilling directly on the green area, trenchless directional drilling is used, drilling from the periphery of the park towards the target area. The drill bit stops at the target area, with a vertical depth of 50m from the ground. Using insulated wires, the positive electrode of the pair of power supply electrodes is placed at the bottom of the borehole through the borehole, while the other negative electrode is placed at "infinity" on the ground, 300m from the borehole opening, ensuring good grounding. One of the observation electrodes is connected to the "infinity" pole of the power supply electrode (short-circuited on the instrument panel), and the other observation electrode is in good contact with the ground medium within a 10m × 10m area to be determined, for example, by driving a copper steel rod into the ground. The voltage output terminal of the power supply electrode and the voltage input terminal of the receiving electrode are connected to the electrical exploration instrument, and the two receiving electrodes are connected to the measuring end of the instrument. Power the induced polarization method instrument with a 200V power supply, turn on the electrical exploration instrument, keep the power supply electrode and the infinity electrode of the observation electrode stationary, and move the other observation electrode point by point on the ground. Measure the potential difference between the ground electrode potential and the infinity electrode potential in the area to be measured, as well as the induced polarization parameter, and record the relative coordinate positions of the corresponding points in the area to be measured. Obtain the coordinate distribution of the ground potential when the underground power supply is applied to the area to be measured.

[0043] The coordinates of the moving observation electrode can be determined using a total station or GPS.

[0044] The interpretation method involves drawing contour maps of potential distribution and induced polarization distribution in the area to be measured. Multiple concentric circles appear on a 30m×50m plane. The center of each concentric circle represents a relatively high potential anomaly or induced polarization anomaly. This high potential or induced polarization anomaly decreases radially outward to form concentric circles, showing the decreasing trend of the potential gradient or induced polarization gradient from its maximum value outward. The center of each concentric circle indicates the center position of the vertical pile foundation with steel reinforcement cage on the ground projection. There are multiple such positions.

[0045] The results of the induced polarization method and the results of the potential measurement show that the location of the reinforcing cage is consistent. One of them can be used, or the two can be used to verify each other.

[0046] Unless otherwise stated, if any of the technical solutions disclosed in this invention specify a numerical range, then the disclosed numerical range is a preferred numerical range. Any person skilled in the art should understand that the preferred numerical range is merely one among many feasible numerical values ​​that has a more obvious or representative technical effect. Because there are many numerical values, it is impossible to list them all. Therefore, this invention discloses only some numerical values ​​to illustrate the technical solutions of this invention. Furthermore, the numerical values ​​listed above should not constitute a limitation on the scope of protection of this invention.

[0047] Furthermore, if the present invention discloses or relates to mutually fixedly connected components or structural parts, then unless otherwise stated, a fixed connection can be understood as: a detachable fixed connection (e.g., using bolts or screws), or a non-detachable fixed connection (e.g., riveting, welding). Of course, mutually fixed connections can also be replaced by an integral structure (e.g., manufactured using a casting process) (except where it is obviously impossible to use an integral molding process).

[0048] Furthermore, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in this invention include states or shapes that are similar to, analogous to, or close to those states or shapes. Any component provided by this invention can be assembled from multiple individual components or can be a single component manufactured using a one-piece molding process.

[0049] The above embodiments are merely illustrative examples to clearly illustrate the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for precise positioning of vertical metal structures deep underground, characterized in that, Measurements were performed using an electrical exploration instrument consisting of a pair of power supply electrodes and a pair of observation electrodes, comprising the following steps: S1. Delineate the ground area to be measured and grid it; S2. Drill at least one borehole in the area to be tested, the depth of which reaches below the groundwater level; S3. Using an insulated wire, the positive power supply electrode of a pair of power supply electrodes is dropped below the water surface through the drill hole, and the negative power supply electrode of the pair of power supply electrodes is placed at an infinite distance from the center of the area to be measured. S4. Place one of the pair of observation electrodes at infinity, and move the other observation electrode on the grid measurement points in the area to be measured, while maintaining good electrical contact with the ground medium; S5. Start the electrical exploration instrument, supply current to the ground through the power supply electrode, and use the observation electrode to measure the geoelectric signal of each grid measuring point in the area to be measured relative to the infinity electrode. The geoelectric signal includes potential difference, excitation polarization parameter or induced electromotive force. S6. Record the coordinates of each measuring point and its corresponding geoelectric signal; S7. Based on the measured data, draw a geoelectric signal contour map of the area to be measured. The contour map presents a concentric circle shape centered on a high or low anomaly and spreading outwards. The center of the concentric circle is the center of the projection of the underground vertical metal structure on the ground.

2. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The electrical exploration instrument is a direct current electrical instrument, and the geoelectric signal is a potential difference.

3. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The electrical exploration instrument is an alternating current electrical instrument, and the geoelectric signal is a potential difference or induced electromotive force.

4. The method for precise positioning of deep underground vertical metal structures according to claim 3, characterized in that: When using an alternating current method instrument, a coil or magnetic rod is used to measure the electromagnetic field anomaly generated by the underground alternating current electric field, and an induced electromotive force contour map is drawn for location.

5. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The electrical exploration instrument is a time-domain / frequency-domain induced polarization method instrument, and the geoelectric signal is the induced polarization parameter.

6. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The drilled hole is a vertical hole, an inclined hole, or a directional hole, and its opening position is located inside or outside the area to be measured.

7. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The coordinates of the moving observation electrode can be determined using a total station or GPS.

8. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The positive electrode or infinity electrode of the power supply electrode is arranged in a parallel manner using multiple electrodes.

9. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: In step S4, the infinity electrode of the observation electrode and the infinity electrode of the power supply electrode share the same electrode.

10. The method for precise positioning of deep underground vertical metal structures according to claim 1, characterized in that: The maximum diameter or side length of the area to be measured is L, and the distance from the power supply electrode to the center of the ground of the area to be measured is greater than or equal to 5L.

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