Ground array three-dimensional transient electromagnetic detection method

Abstract

This invention belongs to the field of transient electromagnetic technology, specifically relating to a ground-based array-type three-dimensional transient electromagnetic detection method. The method includes: first, designing and planning a three-dimensional measurement network according to the detection task, obtaining the coordinates of each sensor node, and forming a sensor array; second, transporting the sensors to the corresponding coordinate points, synchronously transmitting signals, and conducting synchronous data acquisition; and third, processing and visualizing the acquired data for interpretation. This invention enables simultaneous detection of multiple measurement points within a measurement area, thereby constructing a three-dimensional electrical structure image of the underground medium. It not only significantly enhances the intensity of the excitation electromagnetic field, improves the signal-to-noise ratio and detection depth of the measurement signal, but also more realistically reflects the electrical distribution characteristics of the underground medium, reduces ambiguity, and improves the accuracy and reliability of exploration results.

Description

Technical Field

[0001] This invention belongs to the field of transient electromagnetic technology, specifically relating to a ground-based array-type three-dimensional transient electromagnetic detection method. Background Technology

[0002] In the field of geological exploration, the Transient Electromagnetic Method (TEM), as a time-domain electromagnetic exploration method, has long demonstrated its unique advantages in various application scenarios. This technology infers the electrical characteristics of underground media by observing the changes in electromagnetic fields over time, thereby revealing important information such as geological structure, mineral distribution, and hydrogeological conditions. However, traditional ground-based transient electromagnetic detection methods are limited by one-dimensional detection modes and point-by-point measurement methods, making it difficult to comprehensively and accurately reflect the three-dimensional electrical structure of underground media.

[0003] Specifically, one-dimensional detection means that at a given measurement point, only the vertical electrical changes of the underground medium below that point can be obtained, but the horizontal electrical differences cannot be directly revealed. This limitation is particularly obvious under complex geological conditions, which may lead to increased ambiguity in the detection results, affecting the accuracy and efficiency of exploration. In addition, the point-by-point measurement method is not only time-consuming and labor-intensive, but also easily limited by the ground working environment and instrument equipment conditions, making it difficult to adapt to the needs of large-area, high-efficiency exploration.

[0004] To overcome these limitations, it is necessary to develop a new detection technology. Summary of the Invention

[0005] The purpose of this invention is to provide a ground-based array-type three-dimensional transient electromagnetic detection method that can simultaneously detect multiple measuring points within a measurement area, thereby constructing a three-dimensional electrical structure image of the underground medium. This method not only greatly enhances the intensity of the excitation electromagnetic field and improves the signal-to-noise ratio and detection depth of the measurement signal, but also more realistically reflects the electrical distribution characteristics of the underground medium, reduces ambiguity, and improves the accuracy and reliability of exploration results.

[0006] The specific technical solution adopted by this invention is as follows:

[0007] A ground-based array-type three-dimensional transient electromagnetic detection method includes the following steps:

[0008] Step 1: Design and plan a 3D measurement network according to the exploration mission, obtain the coordinates of each sensor node, and form a sensor array;

[0009] Step 2: Transport the sensor to the corresponding coordinate point, transmit signals synchronously, and carry out synchronous data acquisition.

[0010] The third step is to process and visualize the collected data for interpretation.

[0011] The technical effects achieved by this invention are as follows:

[0012] This invention employs an array-based synchronous transmission-reception method to simultaneously detect multiple measuring points within a measurement area, thereby constructing a three-dimensional electrical structure image of the underground medium. This not only greatly enhances the intensity of the excitation electromagnetic field and improves the signal-to-noise ratio and detection depth of the measurement signal, but also more realistically reflects the electrical distribution characteristics of the underground medium, reduces ambiguity, and improves the accuracy and reliability of exploration results. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the array-type three-dimensional transient electromagnetic detection of the present invention;

[0014] Figure 2 This is a schematic diagram of the underground anomaly model in this invention;

[0015] Figure 3 This is the induced potential curve diagram in this invention;

[0016] Figure 4 This is the apparent resistivity curve in this invention. Detailed Implementation

[0017] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is merely used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention.

[0018] like Figure 1-4 As shown, a ground-based array-type three-dimensional transient electromagnetic detection method can reflect the true three-dimensional structure of the underground medium. Through an array-type synchronous transmission and reception design, the electromagnetic field intensity excited by the transmitting antenna can be greatly enhanced, increasing the detection depth. The traditional one-dimensional detection ground loop is improved into a three-dimensional detection sensor array, which, while meeting the detection depth requirements, significantly improves work efficiency and adapts to complex ground working environments. The method includes the following steps:

[0019] S1: Design and plan a three-dimensional measurement network according to the exploration mission, obtain the coordinates of each sensor node, form a sensor array, and form a measurement network by multiple sensor arrays. This network can be designed according to the actual ground working conditions and output parameter requirements. It can be rectangular or other shapes.

[0020] The sensor array contains n sensor nodes. For any i-th sensor node, its ground coordinates (x, y, y) are given by the given information. i ,yi ,z i The resulting measurement network is determined by GPS equipment. The number of nodes can be determined based on requirements such as detection depth and resolution. For a regular square measurement network, n is 9 for a 3×3 grid, 16 for a 4×4 grid, and so on. For irregular measurement networks, the number of grids and sensor nodes can be flexibly designed, as shown in the attached figure. Figure 1 As shown;

[0021] Each sensor node includes a transmitting antenna and a receiving antenna. During actual 3D detection, each node in the sensor array simultaneously transmits and receives signals. According to the theory of electromagnetic field propagation in conductive media, when using this synchronous transmission and reception method, the primary fields of each sensor node at the initial excitation time and in the very shallow layer near the surface are superimposed, jointly inducing a secondary electromagnetic field in the underground medium and reflecting the electromagnetic field response of the underground target.

[0022] S2: Use manual labor, drones, intelligent robots, or other platforms to transport sensors to the corresponding coordinate points, transmit signals synchronously, and collect data synchronously.

[0023] S3: The acquired data is processed and visualized using three-dimensional transient electromagnetic processing technology for interpretation.

[0024] Based on Maxwell's equations, an array-type three-dimensional electromagnetic field theory is proposed. During processing and visualization, this theory is used. In the array-type electromagnetic three-dimensional measurement network, the electromagnetic fields excited by each sensor node satisfy Maxwell's equations.

[0025] The underground electromagnetic field is simultaneously excited by each node in the electromagnetic array, generating an induced secondary electromagnetic field in the underground medium. Neglecting displacement current, the time-domain curl equation satisfied by the electric field components is:

[0026]

[0027] Where, δ(x) i ,y i ,z i ) is the Dirac function at the source, and μ is the permeability of the medium. For the i-th node (x) in the electromagnetic array i ,y i ,z i The emitted magnetic moment of ). n is the number of nodes in the electromagnetic array, and Σ represents the simultaneous excitation of the sensor array.

[0028] The sensor nodes in this invention can be overlapping loops or conical antennas. To meet the detection depth requirements of the task, the traditional one-dimensional ground loop detection is improved into a three-dimensional sensor array, which can significantly improve work efficiency while meeting the detection depth requirements.

[0029] Appendix Figure 2 For the established underground anomaly model, the ground excitation field source is a large loop and multiple small loops with the same magnetic moment. The top interface of the anomaly is buried at a depth of 150 meters, the bottom interface at a depth of 200 meters, and the thickness is 10 meters.

[0030] Appendix Figure 3 and attached Figure 4 The figures show the comparison curves of induced potential and apparent resistivity under two different field source excitations. The curves show that the induced potential and apparent resistivity obtained by using a cluster of small sensors with equal magnetic moments can reflect abnormal information and achieve a detection capability similar to that of the Great Loop.

[0031] This application can achieve the following effects:

[0032] By synchronously transmitting and receiving at each node in the measurement area, the intensity of the excitation electromagnetic field can be greatly enhanced, the signal-to-noise ratio of the measurement signal can be improved, and the detection depth can be increased.

[0033] As for the detection depth required by the task, the traditional one-dimensional ground loop detection is improved into a three-dimensional sensor array, which can significantly improve work efficiency while meeting the detection depth requirements.

[0034] Moreover, three-dimensional detection can reflect the true three-dimensional structure of the underground medium, reduce geophysical ambiguity, and improve the accuracy of detection and interpretation results;

[0035] By utilizing three-dimensional detection technology and methods, and by reducing antenna size and weight, drones can be used to carry out detection, thereby improving detection efficiency while maximizing adaptability to ground measurement environments.

[0036] Sensor arrays can be flexibly designed to form regular and irregular three-dimensional measurement networks based on the required detection depth and the distribution of ground buildings and facilities. The optimal device form can be determined by combining actual working conditions and output parameter requirements, and a variety of options are available.

[0037] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A ground-based array-type three-dimensional transient electromagnetic detection method, characterized in that, Includes the following steps: S1: Design and plan a three-dimensional measurement network according to the detection mission, obtain the coordinates of each sensor node, and form a sensor array; each sensor node includes a transmitting antenna and a receiving antenna; S2: Transport the sensor to the corresponding coordinate point, transmit signals synchronously, and carry out synchronous data acquisition; S3: The acquired data is processed and visualized for interpretation; during processing and visualization, it is achieved through array-type three-dimensional electromagnetic field theory. In the array-type electromagnetic three-dimensional measurement network, the electromagnetic fields excited by each sensor node satisfy Maxwell's equations. The underground electromagnetic field is simultaneously excited by each node in the electromagnetic array, generating an induced secondary electromagnetic field in the underground medium. Neglecting displacement current, the time-domain curl equation satisfied by the electric field components is: Where δ(xi,yi,zi) is the Dirac function at the source, and μ is the permeability of the medium. Let be the emitted magnetic moment of the i-th node (xi,yi,zi) in the electromagnetic array, n be the number of nodes in the electromagnetic array, and Σ represent the simultaneous excitation of the sensor array.

2. The method according to claim 1, characterized in that: In S1, the number of sensor nodes n in the sensor array is such that for any i-th sensor node, the ground coordinates (xi,yi,zi) form a measurement network determined by a GPS device.

3. The method according to claim 2, characterized in that: For a regular square measurement network, n is 9 for a 3×3 grid, 16 for a 4×4 grid, and so on. For irregular measurement networks, the grid and the number of sensor nodes can be flexibly designed.

Images