Ground array type three-dimensional transient electromagnetic detection method

Abstract

The invention belongs to the technical field of transient electromagnetism, and particularly relates to a ground array type three-dimensional transient electromagnetic detection method, which comprises the following steps of: 1, designing and planning a three-dimensional measurement network according to a detection task, obtaining coordinates of each sensor node, and forming a sensor array; 2, conveying the sensor to a corresponding coordinate point, synchronously transmitting a signal, and carrying out data synchronous acquisition; and step 3, processing and visualizing the collected data so as to carry out interpretation. According to the invention, simultaneous detection of a plurality of measurement points in a measurement area can be realized, so that a three-dimensional electrical structure image of an underground medium can be constructed, the electromagnetic field intensity of excitation can be greatly enhanced, the signal-to-noise ratio and the detection depth of a measurement signal can be improved, and the electrical distribution characteristics of the underground medium can be reflected more truly; the multiplicity of solutions is reduced, and the accuracy and reliability of exploration results are improved.

Description

Technical Field

[0001] The invention belongs to the field of transient electromagnetic technology, and in particular relates to a ground array type three-dimensional transient electromagnetic detection method. Background Art

[0002] In the field of geological exploration, transient electromagnetic method (TEM), as a time-domain electromagnetic exploration method, has long demonstrated its unique advantages in a variety of 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 transient electromagnetic detection methods are limited to one-dimensional detection modes and point-by-point measurement methods, and it is difficult to fully and accurately reflect the three-dimensional electrical structure of underground media.

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

[0004] In order to overcome these limitations, it is necessary to propose a new detection technology. Summary of the invention

[0005] The purpose of the present invention is to provide a ground array three-dimensional transient electromagnetic detection method, which can realize the simultaneous detection of multiple measuring points in the measurement area, so as to construct a three-dimensional electrical structure image of the underground medium. It can not only greatly enhance the electromagnetic field intensity of the excitation, improve the signal-to-noise ratio and detection depth of the measurement signal, but also more realistically reflect the electrical distribution characteristics of the underground medium, reduce ambiguity, and improve the accuracy and reliability of the exploration results.

[0006] The technical solution adopted by the present invention is as follows:

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

[0008] Step 1: Design and plan a 3D measurement network based on the detection task, obtain the coordinates of each sensor node, and form a sensor array;

[0009] Step 2: Transport the sensor to the corresponding coordinate point, transmit the signal synchronously, and carry out data synchronous collection;

[0010] Step 3: The collected data is processed and visualized for interpretation.

[0011] The technical effects achieved by the present invention are:

[0012] The present invention realizes simultaneous detection of multiple measuring points in the measurement area by adopting an array-type synchronous transmission-reception method, thereby being able to construct a three-dimensional electrical structure image of the underground medium. It can not only greatly enhance the electromagnetic field intensity of the excitation, improve the signal-to-noise ratio and detection depth of the measurement signal, but also more realistically reflect the electrical distribution characteristics of the underground medium, reduce ambiguity, and improve the accuracy and reliability of the exploration results. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0014] Figure 2 It is a schematic diagram of the underground abnormal body model in the present invention;

[0015] Figure 3 is the induced potential curve diagram of the present invention;

[0016] Figure 4 It is the apparent resistivity curve diagram in the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0018] like Figure 1-4 As shown, a ground array three-dimensional transient electromagnetic detection method can reflect the real three-dimensional structure of the underground medium. Through the array-type synchronous transmission and reception design, the electromagnetic field intensity excited by the transmitting antenna can be greatly enhanced, and the detection depth can be increased. The ground loop of the traditional one-dimensional detection is improved to a sensor array for three-dimensional detection. While meeting the detection depth requirements, it can significantly improve work efficiency and adapt to complex ground working environments, including the following steps:

[0019] S1: Design and plan a three-dimensional measurement network according to the detection task, obtain the coordinates of each sensor node, form a sensor array, and form a measurement network with multiple sensors distributed in an array. The network can be designed according to the actual ground working conditions and output parameter requirements, and can be rectangular or other shapes;

[0020] The number of sensor nodes in the sensor array is n. For any i-th sensor node, its ground coordinate (x i ,yi ,z i The formed measurement network is measured by GPS equipment. The number can be determined according to the requirements of detection depth and detection resolution. For a regular square measurement network, when the grid is 3×3, n is 9, when the grid is 4×4, n is 16, and so on. For an irregular measurement network, 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 contains a transmitting antenna and a receiving antenna. During actual three-dimensional detection, each node in the sensor array transmits and receives signals simultaneously. According to the electromagnetic field propagation theory in conductive media, when this synchronous transmission and reception method is adopted, the primary fields of each sensor node are superimposed on each other in the initial time period of excitation and in the ultra-shallow layer near the surface, and the secondary electromagnetic field is jointly induced in the underground medium, reflecting the electromagnetic field response of the underground target body;

[0022] S2: Use manual or unmanned aerial vehicles, intelligent robots and other carrying platforms to transport the sensors to the corresponding coordinate points, transmit signals synchronously, and carry out synchronous data collection;

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

[0024] Based on Maxwell's equations, an array three-dimensional electromagnetic field theory is proposed. During processing and visualization, it is realized through the array three-dimensional electromagnetic field theory. In the array electromagnetic three-dimensional measurement network, the electromagnetic field excited by each sensor node satisfies Maxwell's equations.

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

[0026]

[0027] Among them, δ(x i ,y i ,z i ) is the Dirac function at the source, μ is the magnetic permeability of the medium, is the i-th node (x i ,y i ,z i ). 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 the present invention can be overlapping loops or conical antennas. For the detection depth required by the work task, the traditional one-dimensional detection ground loop is improved into a three-dimensional detection sensor array, which can significantly improve work efficiency while meeting the detection depth requirement.

[0029] Attached Figure 2 For the underground anomaly model established, 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 is buried at a depth of 200 meters, and the thickness is 10 meters.

[0030] Attached Figure 3 and attached Figure 4 These are the comparison curves of induced potential and apparent resistivity when excited by two kinds of field sources. It can be seen from the curves 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 a large loop.

[0031] This application can achieve the following effects:

[0032] By synchronously transmitting and receiving at each node in the measurement area, the electromagnetic field strength of the excitation 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 work task, the traditional one-dimensional detection ground loop is improved to a three-dimensional detection sensor array, which can significantly improve work efficiency while meeting the detection depth requirements.

[0034] Moreover, 3D detection can reflect the real 3D structure of underground media, reduce geophysical ambiguity, and improve the accuracy of detection and interpretation results;

[0035] By utilizing three-dimensional detection technology and methods and reducing the size and weight of the antenna, it can be carried on an unmanned aerial vehicle, thereby improving the detection efficiency and maximizing its adaptability to the ground measurement environment.

[0036] The sensor array can be flexibly designed according to the detection depth requirements and the distribution of ground buildings and facilities to form regular and irregular three-dimensional measurement networks. Combined with actual working conditions and output parameter requirements, the optimal device form can be determined, and many options can be provided.

[0037] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A ground array three-dimensional transient electromagnetic detection method, characterized in that: The following steps are involved: S1: Design and plan a 3D measurement network according to the detection task, obtain the coordinates of each sensor node, and form a sensor array; S2: transport the sensor to the corresponding coordinate point, transmit the signal synchronously, and carry out data synchronous collection; S3: The acquired data is processed and visualized for interpretation.

2. The method according to claim 1, characterized in that: The number of sensor nodes n in the sensor array in S1, for any i-th sensor node, its ground coordinate (x i ,y i ,z i )The measurement network formed is measured by GPS equipment.

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 number of grids and sensor nodes can be flexibly designed.

4. The method according to claim 1, characterized in that: Each sensor node in S1 includes a transmitting antenna and a receiving antenna.

5. The method according to claim 1, characterized in that: The processing and visualization in S3 are realized through array three-dimensional electromagnetic field theory. In the array three-dimensional electromagnetic measurement network, the electromagnetic field excited by each sensor node satisfies Maxwell's equations. The underground electromagnetic field is excited simultaneously by each node in the electromagnetic array, generating an induced secondary electromagnetic field in the underground medium. When the displacement current is ignored, the time domain curl equation satisfied by the electric field component is: Among them, δ(x i ,y i ,z i ) is the Dirac function at the source, μ is the magnetic permeability of the medium, is the i-th node (x i ,y i ,z i ), n is the number of nodes in the electromagnetic array, and Σ represents the simultaneous excitation of the sensor array.

Images