Simulation method and experimental system of array magnetic anomaly detection

Abstract

The application relates to the field of underground magnetic anomaly detection, and discloses an array magnetic anomaly detection simulation method and an experimental system.The experimental system comprises a layered medium simulation device, an array transmitting coil module and an array receiving coil module.The array transmitting coil module mainly generates a primary magnetic field signal required by the experiment;the layered medium simulation device adopts a scale reduction principle to simulate actual working conditions, is composed of multiple layers of acrylic plates, each layer can be further divided horizontally, a magnetic anomaly object can be placed in a grid formed by the acrylic plates, and the position of the magnetic anomaly object and geological parameters can be controlled during the experiment; and the array receiving coil module mainly receives an induced magnetic field signal of the magnetic anomaly object at different positions.The application can simulate actual geophysical prospecting working conditions, the experimental method adopts a transient electromagnetic method, the array transmitting and receiving coil is used to detect the magnetic anomaly object, and by analyzing the response signal difference of the magnetic anomaly object at different positions, the forward research on the underground medium magnetic anomaly object can be carried out.

Description

Technical Field

[0001] This invention relates to the field of underground magnetic anomaly detection, and more particularly to a simulation method and experimental system for array magnetic anomaly detection. Background Technology

[0002] With the continuous development of urbanization, the ongoing exploitation of mineral resources, and the demands of the military field, the exploration technology for magnetic anomalies such as underground cavities, mineral deposits, and unexploded ordnance in cities has become increasingly complex, placing higher demands on exploration accuracy and identification precision. Interpreting the response signals of underground magnetic anomalies has become more challenging. Therefore, the analysis of the excitation response characteristics of underground magnetic anomalies is of great significance. Transient electromagnetic methods, due to their portable equipment, long detection range, and low dependence on the environment, have long been a research hotspot in the field of underground magnetic anomaly detection. When using transient electromagnetic methods for magnetic anomaly detection, extensive forward modeling studies of underground magnetic anomalies are necessary beforehand to more accurately interpret the depth, location, and structure of the detected target.

[0003] In practical geophysical exploration, interpreting the detection signals of various magnetic anomalies requires prior forward and inverse modeling studies to analyze their response mechanisms. However, conducting experiments under actual working conditions is cumbersome; therefore, simulation studies can be performed in the laboratory using physical simulation experiments. Physical simulation experiments can realistically and objectively simulate actual field conditions, obtaining the response characteristics of underground magnetic anomalies and increasing the reliability of the results. Due to its economic efficiency and ability to more accurately reflect actual conditions compared to numerical simulation, physical simulation is favored by many researchers.

[0004] When establishing a physical model, scaling relationships can be used for design. However, it's impossible to keep all phenomena unchanged during scaling down; some phenomena cannot be proportionally reduced. If these phenomena are unimportant, while important research phenomena can be preserved, then such scaling is considered feasible. Simulation experiments can study a phenomenon scaled down, rather than scaling down the entire experimental conditions. Combining simulation, theoretical research, and experimental results for analysis improves accuracy. By abstractly modeling geological conditions, a simulation experimental system for array magnetic anomaly detection can be established. In this simulation system, the electromagnetic wave propagation mechanism is independent of the scaling scale; therefore, the rationality of the array's transceiver coil positions can be studied, and the propagation mechanism of electromagnetic waves in different underground media and the attenuation characteristics of magnetic anomalies can be explored. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a simulation method and experimental system for array magnetic anomaly detection, establish a layered medium simulation device, simulate actual geophysical exploration conditions, change the parameters of magnetic anomalies and geological structures, and conduct magnetic anomaly detection experiments using an array coil structure through transient electromagnetic methods, which facilitates the study of transient electromagnetic response characteristics in complex geological conditions.

[0006] To achieve the aforementioned objectives, the technical solution adopted is as follows:

[0007] A simulation experimental system for array magnetic anomaly detection includes a layered medium simulation device, an array transmitting coil module, and an array receiving coil module;

[0008] In actual underground material exploration, geological bodies can be abstracted into simple multi-layered structures based on geological differences at different depths. Therefore, experimental simulations can be carried out by constructing a layered medium simulation device with similar geometric shape and electromagnetic properties.

[0009] The layered medium simulation device is composed of multiple transparent acrylic plates of different sizes. The overall shape is a cuboid with a horizontal multi-layer structure. The horizontal layers are separated by acrylic plates. At any layer of the device, it can be further divided vertically by small acrylic plates. The space divided by the acrylic plates is easy to adjust. The simulated geological materials can be easily replaced in the space according to different experimental contents. Since the acrylic material has a small influence in the electromagnetic propagation process, its influence can be ignored in the process of magnetic anomaly detection using transient electromagnetic method. Moreover, the acrylic material has the advantages of good transparency and excellent strength, and the experimental state can be easily observed during the experiment.

[0010] The array transmitting coil module consists of multiple identical excitation coils, which are evenly placed on the top layer of the layered medium simulation device. A signal source provides the same alternating pulse signal to each excitation coil. Each excitation coil generates a primary alternating excitation magnetic field of the same magnitude at its location. The generated primary magnetic field diffuses in the layered medium simulation device. When it propagates to the geological simulation layer and magnetic anomalies in the layered medium simulation device, it generates an induced secondary magnetic field signal. Due to the different positions of each excitation coil, the distance between the different coils and the magnetic anomalies at a fixed position is different. Therefore, the responses generated by different excitation coils in the magnetic anomalies are also different.

[0011] The array receiving coil module consists of multiple identical induction coils, which are also placed on the top layer of the layered medium simulation device and evenly distributed around the corresponding excitation coils. This method can effectively reduce the mutual inductance between the excitation coil and the induction coil, reduce primary field signal interference, and maximize the reception of secondary field induction signals. Since the array induction coils are located at different positions above the magnetic anomaly, the secondary magnetic field signals received by each induction coil will be different. By analyzing the position of the magnetic anomaly and the response characteristics of the secondary magnetic field signals, forward modeling studies of the magnetic anomaly can be performed.

[0012] As a further improvement of the present invention, the layered medium simulation device is composed of acrylic sheets and is divided into four layers in the horizontal direction: L1 layer, L2 layer, L3 layer and L4 layer, which are separated from each other by acrylic sheets. The top and bottom layers are complete cuboid structures, and the two middle layers are further separated by small acrylic sheets. Magnetic anomalies are placed in the two middle layers. The experimental process can be intuitively expressed by the placement position.

[0013] A simulation method for array magnetic anomaly detection includes the following steps:

[0014] First, the magnetic anomaly is placed at a position k1 in the layered medium simulation device. An array alternating pulse signal i1(t) is provided to the array transmitting coil module. Each excitation coil is excited at its position to generate a primary excitation magnetic field. The primary excitation magnetic field generates a primary excitation magnetic field in the mutual inductance M of the transmitting and receiving coils. TR Under the influence of the magnetic field, a primary induced electromotive force v1(t) is generated. The primary magnetic field diffuses within the layered medium simulation device, generating an eddy current signal i2(t) inside the magnetic anomaly. At the instant the signal is turned off, the eddy current signal in the magnetic anomaly also decays, generating a secondary magnetic field signal. The secondary magnetic field signal is generated by the mutual inductance M between the magnetic anomaly and the receiving coil. RC A secondary induced electromotive force v2 is generated under the action of the action. ( The induction coil collects the total induced electromotive force v(t) at position k1, consisting of the primary magnetic field induced electromotive force v1(t) and the secondary magnetic field induced electromotive force v2(t), where v1(t) is the interference signal and v2(t) is the effective signal. The response mechanism of the magnetic anomaly at this position v2(t) is studied. The position of the magnetic anomaly is changed to k2, and the above steps are repeated to obtain the total induced electromotive force v(t) at position k2. By changing the magnetic anomaly to different layers and positions, forward modeling studies of the magnetic anomaly response at different positions can be performed. The principle of array transient detection is shown in the following equation. This simulation experimental system can be used to conveniently conduct transient electromagnetic detection experiments.

[0015]

[0016] In the formula, v(t) is the total induced electromotive force of the receiving coil, v1(t) is the primary induced electromotive force, v2(t) is the secondary induced electromotive force, i1(t) is the excitation source of the transmitted signal, I0 is the amplitude of the excitation source, i2(t) is the eddy current induced by the magnetic anomaly, and L... c τ is the inductance of the magnetic anomaly, τ is the time constant of the magnetic anomaly, and Φ is the magnetic flux received by the receiving coil.

[0017] The following formulas represent the conditions and research parameters that the medium in a layered medium simulation device must meet based on actual operating conditions;

[0018]

[0019] In the formula: σ m μ m , ε m t m These represent the electrical conductivity, magnetic permeability, geometric length, dielectric constant, and sampling time of the physical simulation experiment, respectively. f μ f , ε f t f Let N represent the conductivity, permeability, geometric length, dielectric constant, and sampling time of the actual detection experiment, respectively; N be the number of turns of the induction coil; φ(t) be the magnetic flux through the induction coil; S be the area of ​​the induction coil; B(t) be the magnetic flux density; and Δt be the magnetic flux density. i To investigate the differences in response signals of magnetic anomalies at different locations, the analysis was conducted using Δ at different locations. i The difference can be used to conduct forward modeling studies on magnetic anomalies in underground media, f(k i ) represents position k i The induced magnetic field signal at the location, f(k) i+1 ) represents position k i+1 The induced magnetic field signal at the location.

[0020] The beneficial effects of this invention are:

[0021] 1. The present invention discloses a simulation method and experimental system for array magnetic anomaly detection, which can simulate the actual working conditions of geophysical exploration and facilitate the study of transient electromagnetic response characteristics in complex geological conditions.

[0022] 2. In the simulation experiment of array magnetic anomaly detection, the present invention can achieve controllability of the magnetic anomaly target position by changing the position of the magnetic anomaly object in the dielectric layer; and achieve controllability of array coil detection by changing the number and structure of array transceiver coils.

[0023] 3. This invention uses acrylic material to divide the dielectric layer, which has good transparency and high strength, making the experimental process more intuitive. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is a geological simulation diagram of the present invention;

[0026] Figure 2 This is a three-dimensional structural schematic diagram of Embodiment 2 of the present invention;

[0027] Figure 3 This is a flowchart illustrating the simulation experiment process and structure of the present invention. Specific embodiments

[0028] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0029] In order to enable those skilled in the art of this technology to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0030] Embodiment 1

[0031] As Figure 1 shown, an analog experimental system for array magnetic anomaly detection includes a layered medium simulation device, an array transmitting coil module, and an array receiving coil module;

[0032] In actual underground material exploration, geological bodies can be abstracted into a simple multi-layer structure according to geological differences at different depths. Therefore, experimental simulations can be carried out by constructing a layered medium simulation device with similar geometric shapes and electromagnetic properties;

[0033] The layered medium simulation device is composed of multiple transparent acrylic plates of different sizes, with an overall cuboid shape, a horizontal multi-layer structure. The horizontal layers are separated by acrylic plates horizontally, and in any layer of the device, longitudinal separation can be carried out again by small acrylic plates. The space divided by the above acrylic plates is convenient to adjust, and the simulated geological materials can be simply replaced in the space according to different specific experimental contents. Since the influence of acrylic materials on electromagnetic propagation is very small, during the process of magnetic anomaly detection using the transient electromagnetic method, its influence can be ignored. Moreover, acrylic materials have the advantages of good transparency and excellent strength, and the experimental state can be conveniently observed during the experiment;

[0034] The array transmitting coil module is composed of multiple identical excitation coils, which are evenly placed on the top layer of the layered medium simulation device. A signal source is used to provide the same alternating pulse signal to each excitation coil. Each excitation coil will generate the same magnitude of primary alternating excitation magnetic field at its location. When the generated primary magnetic field diffuses in the layered medium simulation device and propagates to the geological simulation layer and magnetic anomaly object in the layered medium simulation device, an induced secondary magnetic field signal will be generated. Since the positions of each excitation coil are different, for a magnetic anomaly object at a fixed position, the distances between different coils and the magnetic anomaly object are different. Therefore, the responses generated by different excitation coils in the magnetic anomaly object are also different;

[0035] The array receiving coil module consists of multiple identical induction coils. The induction coils are also placed on the top layer of the layered medium simulation device and evenly placed around the corresponding excitation coils. This method can effectively reduce the mutual inductance between the excitation coil and the induction coil, reduce the interference of the primary field signal, and receive the secondary field induction signal to the maximum extent. Since the array induction coils are located at different positions above the magnetic anomaly object, there will be differences in the secondary magnetic field signals received by each induction coil. Through the position of the magnetic anomaly object and the response characteristics of the secondary magnetic field signal, forward research on the magnetic anomaly object can be carried out.

[0036] Example 2

[0037] Based on the structure of Example 1, in Example 2, as Figure 2 shown, the layered medium simulation device is composed of acrylic plates and is divided into four layers in the horizontal direction: L1 layer, L2 layer, L3 layer, and L4 layer, separated by acrylic plates. The top and bottom layers are complete cuboid structures, and the middle two layers are further separated by small acrylic plates. The magnetic anomaly object is placed in the middle two layers, and the experimental process can be intuitively expressed through the placement position.

[0038] Example 3

[0039] As Figure 3 shown, a simulation method for array magnetic anomaly detection includes the following steps:

[0040] First, place the magnetic anomaly object at the position k1 in the middle of the first layer L1 of the layered medium simulation device, provide an array alternating pulse signal to the array transmitting coil module, and each excitation coil generates a primary excitation magnetic field at its position. The primary magnetic field diffuses in the layered medium simulation device, generates an eddy current signal inside the magnetic anomaly object, and at the moment when the signal is turned off, the eddy current signal of the magnetic anomaly object also decays, generating a secondary magnetic field signal. The induction coil collects the secondary magnetic field signal f(k1) at the position k1, studies the response mechanism of the magnetic anomaly object at this position, changes the position of the magnetic anomaly object to the corresponding position k2 in the second layer L2, and performs the above steps again to obtain the secondary magnetic field signal f(k2) at the position k2. Through the difference in the response between f(k2) and f(k1), the response mechanisms of the magnetic anomaly object at the burial depths L2 and L1 can be studied. By changing the magnetic anomaly object to different layers and different horizontal positions, forward research on the magnetic anomaly response at different positions of the magnetic anomaly object can be carried out. At the same time, by changing the medium parameters of different layers, different geological conditions can be simulated. The following formula is the condition and research parameter that the medium in the layered medium simulation device needs to meet according to the actual working conditions;

[0041]

[0042] In the formula: σ m 、μm , ε m t m These represent the electrical conductivity, magnetic permeability, geometric length, dielectric constant, and sampling time of the physical simulation experiment, respectively. f μ f , ε f t f Let N represent the conductivity, permeability, geometric length, dielectric constant, and sampling time of the actual detection experiment, respectively; N be the number of turns of the induction coil; φ(t) be the magnetic flux through the induction coil; S be the area of ​​the induction coil; B(t) be the magnetic flux density; and Δt be the magnetic flux density. i To investigate the differences in response signals of magnetic anomalies at different locations, the response signals Δ at different locations were analyzed. i The difference can be used to conduct forward modeling studies on magnetic anomalies in underground media, f(k i ) represents position k i The induced magnetic field signal at the location, f(k) i+1 ) represents position k i+1 The induced magnetic field signal at the location.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, component splitting or combination, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A simulation experimental system for array magnetic anomaly detection, characterized in that: It includes a layered medium simulation device, an array transmitting coil module, and an array receiving coil module; The layered medium simulation device is composed of multiple transparent acrylic sheets of different sizes. The overall shape is a cuboid with a horizontal multi-layer structure. The horizontal layers are separated by acrylic sheets. At any layer of the device, it can be further divided vertically by small acrylic sheets. The array transmitting coil module consists of multiple identical excitation coils, which are evenly placed on the top layer of the layered medium simulation device. A signal source provides the same alternating pulse signal to each excitation coil. Each excitation coil generates a primary alternating excitation magnetic field of the same magnitude at its location. The generated primary magnetic field diffuses in the layered medium simulation device. When it propagates to the geological simulation layer and magnetic anomalies in the layered medium simulation device, it generates an induced secondary magnetic field signal. Due to the different positions of each excitation coil, the distance between the different coils and the magnetic anomalies at a fixed position is different. Therefore, the responses generated by different excitation coils in the magnetic anomalies are also different. The array receiving coil module consists of multiple identical induction coils, which are also placed on the top layer of the layered medium simulation device and evenly distributed around the corresponding excitation coils. Since the array induction coils are located at different positions above the magnetic anomaly, the secondary magnetic field signals received by each induction coil will differ. By analyzing the position of the magnetic anomaly and the response characteristics of the secondary magnetic field signals, forward modeling studies of the magnetic anomaly can be conducted.

2. The simulation experimental system for array magnetic anomaly detection according to claim 1, characterized in that: The layered medium simulation device is made of acrylic sheets and is divided into four layers in the horizontal direction: L1 layer, L2 layer, L3 layer and L4 layer. The layers are separated by acrylic sheets. The top and bottom layers are complete cuboid structures, and the two middle layers are further separated by small acrylic sheets. Magnetic objects are placed in the two middle layers. The placement of the objects allows for a direct representation of the experimental process.

3. A simulation method for array magnetic anomaly detection, characterized in that, Includes the following steps: First, the magnetic anomaly is placed at a position k1 in the layered medium simulation device. An array alternating pulse signal i1(t) is provided to the array transmitting coil module. Each excitation coil is excited at its position to generate a primary excitation magnetic field. The primary excitation magnetic field generates a primary excitation magnetic field in the mutual inductance M of the transmitting and receiving coils. TR Under the influence of the magnetic field, a primary induced electromotive force v1(t) is generated. The primary magnetic field diffuses within the layered medium simulation device, generating an eddy current signal i2(t) inside the magnetic anomaly. At the instant the signal is turned off, the eddy current signal in the magnetic anomaly also decays, generating a secondary magnetic field signal. The secondary magnetic field signal is generated by the mutual inductance M between the magnetic anomaly and the receiving coil. RC Under the action of the magnetic field, a secondary induced electromotive force v2(t) is generated; the induction coil collects the total induced electromotive force v(t) at position k1, which is composed of the primary magnetic field induced electromotive force v1(t) and the secondary magnetic field induced electromotive force v2(t), where v1(t) is the interference signal and v2(t) is the effective signal. The response mechanism of the magnetic anomaly at this position v2(t) is studied. The position of the magnetic anomaly is changed to k2, and the above steps are repeated to obtain the total induced electromotive force v(t) at position k2. By changing the magnetic anomaly to different layers and positions, the forward modeling study of the magnetic anomaly response at different positions can be carried out. The principle of array transient detection is shown in the following formula. This simulation experimental system can be used to conveniently carry out transient electromagnetic detection experiments. In the formula, v(t) is the total induced electromotive force of the receiving coil, v1(t) is the primary induced electromotive force, v2(t) is the secondary induced electromotive force, i1(t) is the excitation source of the transmitted signal, I0 is the amplitude of the excitation source, i2(t) is the eddy current induced by the magnetic anomaly, and L... c τ is the inductance of the magnetic anomaly, τ is the time constant of the magnetic anomaly, and Φ is the magnetic flux received by the receiving coil. The following formulas represent the conditions and research parameters that the medium in a layered medium simulation device must meet based on actual operating conditions; In the formula: σ m μ m , ε m t m These represent the electrical conductivity, magnetic permeability, geometric length, dielectric constant, and sampling time of the physical simulation experiment, respectively. f μ f , ε f t f Let N represent the conductivity, permeability, geometric length, dielectric constant, and sampling time of the actual detection experiment, respectively; N be the number of turns of the induction coil; φ(t) be the magnetic flux through the induction coil; S be the area of ​​the induction coil; B(t) be the magnetic flux density; and Δt be the magnetic flux density. i To investigate the differences in response signals of magnetic anomalies at different locations, the analysis was conducted using Δ at different locations. i The difference can be used to conduct forward modeling studies on magnetic anomalies in underground media, f(k i ) represents position k i The induced magnetic field signal at the location, f(k) i+1 ) represents position k i+1 The induced magnetic field signal at the location.

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