A mine goaf point detection device and method

Abstract

The application belongs to the technical field of geophysical exploration and mineral disaster geological detection, and specifically discloses a goaf detection device and method for a mining area, which is characterized by the following steps: two power supply electrodes are arranged at fixed positions in a to-be-detected area, an observation line parallel to the connecting line of the power supply electrodes is arranged in the lateral equatorial observation area, and two receiving coils are arranged along the direction of the observation line at intervals; a transient electromagnetic transmitter is used to inject pulse current into a fixed grounding electrical source, and the two receiving coils synchronously receive induced voltage generated by the underground transient secondary magnetic field in the observation gap after the power supply electrodes are turned off; the induced voltages of the two receiving coils are differentiated to obtain the difference in the differential response of two adjacent receiving positions; the double-receiving-coil assembly is moved along the observation line, and the goaf boundary is identified according to the position of the enhanced differential response. The application suppresses the fixed-source slow-varying response, the uniform surrounding rock background and the related environmental interference through differentiation, and highlights the spatial non-uniform response caused by the goaf boundary.

Description

Technical Field

[0001] This application belongs to the field of geophysical exploration and mineral disaster geological detection technology, and more specifically, relates to a mining area goaf detection device and method. Background Technology

[0002] Mining voids, left after the extraction of mineral resources, are typically characterized by complex geological evolution states due to rock stress and ground activity, including non-collapse, collapsed and compacted, fractured, partially filled, or waterlogged areas. The formation of the void and its overlying fault zone significantly alters the initial pore structure, water enrichment, and macroscopic resistivity distribution of the underground medium. The presence of such geological anomalies can easily induce secondary geological disasters such as surface subsidence and mine water inrush, posing a serious threat to the foundation stability of engineering construction sites. Therefore, accurately detecting the lateral boundaries, planar distribution range, and width along the survey line of the void has become a crucial foundational task for ensuring safe mine production and conducting geological assessments of construction sites.

[0003] In the field of geophysical exploration of mined-out areas, the ground-based fixed electric source transient electromagnetic method is a core detection technique. Its basic principle involves injecting pulsed currents into the ground using two grounded power supply electrodes and observing the transient secondary electromagnetic field response excited by the underground conductive medium during the current-off interval. In a typical equatorial device observation mode, the receiving measurement point is located in the observation area to the side of the line connecting the power supply electrodes, and the observation profile is usually parallel to the electrode line. The observation relies primarily on the receiving coil to observe the attenuation evolution characteristics of the vertical magnetic field component over time. The effective detection depth and electromagnetic anomaly response characteristics of this detection scheme are comprehensively influenced by multiple detection parameters, including the distance between the power supply electrodes, the transmitter-receiver distance, the intensity of the transmitted current, and the receiving time window.

[0004] Although existing electrical source detection schemes have been widely used, they still have significant shortcomings in accurately delineating goaf boundaries. Current conventional techniques mostly employ a single receiving coil to measure the absolute electromagnetic response and use apparent resistivity calculations or inversions to determine anomalous areas. However, because the spatial field excited by a fixed electrical source changes slowly with the receiving position, single-coil observation data is often affected by a combination of factors, including the transmitting and receiving positions, regional geological background, and environmental noise. This makes the transverse electrical abrupt changes at the goaf boundary easily masked by a strong background field or a gradual spatial variation, severely limiting the reliability and effectiveness of goaf boundary identification. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application aims to provide a mining goaf detection device and method. The goal is to solve the problem that current conventional technologies often use a single receiving coil to measure the absolute electromagnetic response and rely on apparent resistivity calculation or inversion to determine abnormal areas. However, because the spatial field excited by a fixed electrical source changes slowly with the receiving position, single-coil observation data is often affected by a combination of factors such as the transmitting and receiving positions, regional geological background, and environmental noise. This makes it easy for the transverse electrical abrupt changes at the goaf boundary to be masked by a strong background field or a gradual spatial variation trend, thus severely restricting the reliability and effectiveness of goaf boundary identification.

[0006] The first aspect of this application relates to a mining goaf detection device, comprising: a fixed grounding electrical source, a transient electromagnetic transmitter, a dual receiving coil assembly, a dual-channel receiver, and a data processing unit; The fixed grounding electrical source includes two power supply electrodes; the transient electromagnetic transmitter is used to inject pulse current into the two power supply electrodes, and after the pulse current is turned off, the induced current in the underground medium diffuses over time and generates a transient secondary magnetic field. The dual-receiving coil assembly is located in the equatorial observation area of ​​a fixed grounded electrical source. The equatorial observation line is set to the side of the line connecting the two power supply electrodes and is parallel to the line connecting the two power supply electrodes. The dual-receiving coil assembly includes two receiving coils, which are independently connected to a dual-channel receiver. The two receiving coils have the same shape, the same number of turns, the same winding direction, and parallel coil axes. The coil plane is parallel to the ground surface and is used to move along the equatorial observation line to receive the time change of the vertical transient magnetic field component, thereby generating an induced voltage. The two-channel receiver is used to synchronously record the induced voltage of the two receiving coils; the data processing unit is used to differentially analyze the induced voltage generated by the two receiving coils, obtain the differential response difference along the equatorial observation line, and identify the boundary of the goaf based on the location of the enhanced differential response.

[0007] In some implementations, when the dual receiving coil assembly crosses the goaf boundary, with one receiving coil positioned above the goaf-affected area and the other above the intact surrounding rock, the differential response is enhanced, highlighting the spatial non-uniform response caused by the goaf boundary.

[0008] In some implementations, the differential response of the two receiving coils is: ; in, , ; and The induced voltage of the two receiving coils; and These represent the common background components at the locations of the two receiving coils, including the slowly varying response of the fixed electrical source in a local area, the uniform surrounding rock response, and the related interference coupled to the dual-channel receiver simultaneously. and These represent the abnormal responses generated at the locations of the two receiving coils in the goaf of the mining area and its boundary.

[0009] In some embodiments, the dual-receiver coil assembly includes two receiving coils and an insulating support; the two receiving coils are circular, rectangular, multi-turn hollow coils or magnetic core coils; the insulating support is used to maintain the spacing and orientation stability of the two receiving coils.

[0010] In some implementations, each receiving channel of the dual-channel receiver includes an input protection module, a low-noise amplification module, a low-pass filter module, an analog-to-digital conversion module, and a control module; The control module provides a common sampling clock and time zero point for the receiving channel and receives the synchronous trigger signal from the transient electromagnetic transmitter; the input protection module limits the overvoltage that occurs at the moment of transmission shutdown; the low-noise amplification module improves the transient response amplitude; the low-pass filter module suppresses out-of-band high-frequency interference; and the analog-to-digital converter module converts the analog induced voltage into a digital signal.

[0011] In some implementations, at an observation point, a transient electromagnetic transmitter is used to repeatedly output pulse current a preset number of times, and a dual-channel receiver is used to synchronously acquire the decay curves of the differential response of the two receiving coils over time after each shutdown; a data processing unit is used to superimpose the decay curves of the differential response over time of the repeated observations and calculate the differential response on the same time channel.

[0012] In some implementations, the dual receiving coil assembly is mounted on a non-metallic trolley, a towing bracket, or a manually carried bracket.

[0013] The second aspect of this application relates to a method for detecting goaf points in mining areas, specifically including the following steps: Step 1: Fix two power supply electrodes at the location in the area to be measured, set up an observation line parallel to the line connecting the power supply electrodes in the equatorial observation area to the side of the electrodes, and set up two receiving coils at intervals along the direction of the observation line; Step 2: A transient electromagnetic transmitter is used to inject pulse current into a fixed grounded electrical source. During the observation gap after the source is turned off, the two receiving coils synchronously receive the induced voltage generated by the underground transient secondary magnetic field. Step 3: Differentiate the induced voltages of the two receiving coils to obtain the differential response difference between two adjacent receiving positions; Step 4: Move the dual receiving coil assembly along the survey line and identify the boundary of the goaf based on the location of the enhanced differential response; the differential response is smaller when both receiving coils are above the same geoelectric medium, and the differential response is enhanced when the two coils are above the intact surrounding rock and the goaf area, respectively.

[0014] In some implementations, in step four, the decay of the differential response over time is recorded on multiple observation time channels, and the anomaly of the goaf boundary is confirmed based on the continuous change of the differential response at adjacent observation points.

[0015] In some implementations, the dual receiving coil assembly is sequentially spanned across the entry boundary, the interior of the goaf, and the exit boundary of the goaf, and differential response enhancement zones are formed at the entry and exit boundaries to determine the goaf boundary.

[0016] In some implementations, multiple parallel survey lines are laid out in the effective equatorial observation area of ​​the same fixed grounding electrical source, and each line is scanned using a dual receiving coil assembly to obtain the changes in the boundary of the goaf at different profile positions.

[0017] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: This application provides a method for detecting goaf points in mining areas. It uses a fixed grounded electrical source, and the position and direction of the power supply electrodes remain unchanged during the observation process. This avoids the need to repeatedly set up electrodes and power supply wires at each measuring point, which helps to improve the consistency of observations along the measuring line.

[0018] This application provides a method for detecting goaf points in mining areas. Two receiving coils are set up at intervals along the survey line in the equatorial observation area of ​​a fixed electrical source. Taking advantage of the fact that adjacent positions have a similar background, the method suppresses the slow-varying response of the fixed source, the uniform surrounding rock background, and related environmental interferences through differential suppression, highlighting the spatial non-uniform response caused by the goaf boundary.

[0019] This application provides a method for detecting goaf points in mining areas. Taking into account the large lateral range of mining goaf areas, two receiving coils are moved along the survey line that crosses the boundary of the goaf area. The method has a simple structure, a small number of channels, and is easy to deploy quickly and continuously scan.

[0020] This application provides a method for detecting goaf points in mining areas. Two receiving coils independently collect data and perform differential analysis in a receiver or data processing unit, which can retain the original data from the two receiving positions, facilitating the verification of boundary anomalies. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the differential detection method for dual receiving coils in a mining goaf provided in this application embodiment.

[0022] Figure 2(a) is a schematic diagram of the overall arrangement of the differential detection of the dual receiving coils in the equatorial region of the fixed grounding electrical source provided in the embodiment of this application.

[0023] Figure 2(b) is a cross-sectional schematic diagram showing the relationship between the receiving position and the underground electrical structure when the dual receiving coils cross the boundary of the goaf provided in the embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the dual receiving coil assembly structure and independent receiving relationship structure provided in the embodiments of this application.

[0025] Figure 4 This is a schematic diagram of the internal workings of the dual-channel receiver provided in the embodiments of this application.

[0026] Figure 5 This is a schematic diagram illustrating the response difference mechanism when dual receiving coils cross the boundary of a mining goaf, as provided in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0029] In this application, the terms “first” and “second” are used to distinguish different objects, rather than to describe a specific order of objects.

[0030] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0031] In the description of the embodiments in this application, unless otherwise stated, "multiple" means two or more.

[0032] On the one hand, this application provides a mining area goaf detection device, including a fixed grounding electrical source, a transient electromagnetic transmitter, a dual receiving coil assembly, a dual-channel receiver, and a data processing unit; The fixed grounding electrical source includes a first power supply electrode A and a second power supply electrode B; the positions, power supply directions, and distances between the first power supply electrode A and the second power supply electrode B remain fixed during a set of observations; a transient electromagnetic transmitter injects pulse current into the first power supply electrode A and the second power supply electrode B, and after the current is turned off, the induced current in the underground medium diffuses over time and generates a transient secondary magnetic field.

[0033] The dual receiving coil assembly is located in the equatorial observation area of ​​the fixed grounded electrical source; the equatorial observation survey line is set to the side of the line connecting the first power supply electrode A and the second power supply electrode B, and is parallel or approximately parallel to the line; the dual receiving coil assembly includes a first receiving coil R1 and a second receiving coil R2 arranged at intervals along the survey line direction. The two coils are mounted on an insulating support with low magnetic and low conductivity, and maintain their relative position and attitude during the moving observation process.

[0034] The first receiving coil R1 and the second receiving coil R2 have the same shape, number of turns, winding direction, and parallel coil axes. The coil plane is parallel to the ground surface to receive the time variation of the vertical transient magnetic field component. The two receiving coils are independently connected to a dual-channel receiver to preserve the original response at both spatial locations.

[0035] The dual-channel receiver includes an input protection module, a low-noise amplification module, a filtering module, an analog-to-digital conversion module, and a control module. The two channels share a sampling clock and a time zero point for synchronously recording the induced voltages of the first receiving coil R1 and the second receiving coil R2. The data processing unit differentially analyzes the synchronous responses of the two channels to obtain the spatial response differences along the measurement line.

[0036] According to Faraday's law of electromagnetic induction, the... i The induced voltage generated by each receiving coil can be expressed as: (1); in, For the first i The induced voltage of each receiving coil, This refers to the number of coil turns. The magnetic flux passing through the coil; For the first receiving coil R1 and the second receiving coil R2, which are arranged adjacently, their received signals can be expressed as follows: , (2); in, and These represent the common background components at the two receiving locations, including the slowly varying response of the fixed electrical source in a local range, the uniform surrounding rock response, and the related interference coupled to both channels simultaneously. and These represent the abnormal responses generated at the locations of the two receiving coils in the goaf of the mining area and its boundary.

[0037] The differential response of the two receiving coils is: (3); Since the two receiving coils are located adjacent to each other at the same time, have the same receiving direction, and have approximately the same structure, when the two coils are above the same or approximately the same ground dielectric, The common background component is suppressed in the differential equation; if both coils are simultaneously located above intact surrounding rock, or simultaneously located above the influence area of ​​a goaf with a large lateral range, then The differential response is relatively small.

[0038] When the dual-receiving coil assembly crosses the boundary of the goaf, one receiving coil is located above the goaf-affected area, and the other receiving coil is located above the intact surrounding rock. The electrical structure and induced current diffusion state are different at the two locations, making... and They are no longer equal; at this point, the difference response is approximately: (4); As can be seen from formula (4), the differential operation weakens the slowly varying background shared by the two receiving positions, while preserving and highlighting the spatial non-uniform response caused by the goaf boundary. The differential operation mainly suppresses the correlated common background, but it does not mean that the uncorrelated random noise of the two channels is completely canceled out. Therefore, in actual observation, the data stability can be improved by repeated transmission superposition and filtering.

[0039] Secondly, such as Figure 1 As shown, this application provides a method for detecting goaf points in mining areas based on the above-mentioned device, specifically including the following steps: Step 1: Set up a first power supply electrode A and a second power supply electrode B in a fixed position in the area to be measured. Set up an observation line parallel to the line connecting the power supply electrodes in the equatorial observation area to the side of the electrode. Set up the first receiving coil R1 and the second receiving coil R2 at intervals along the direction of the observation line. Step 2: The transient electromagnetic transmitter injects a pulse current into the fixed grounded electrical source. During the observation gap after the signal is turned off, the first receiving coil R1 and the second receiving coil R2 synchronously receive the induced voltage generated by the underground transient secondary magnetic field. Step 3: Differentiate the induced voltages of the two receiving coils to obtain the differential response difference between two adjacent receiving positions; Step 4: Move the dual receiving coil assembly along the survey line. When both receiving coils are above the same geoelectric medium, the differential response is small. When the two coils are above the intact surrounding rock and the goaf area respectively, the differential response is enhanced. Identify the goaf boundary based on the location of the enhanced differential response.

[0040] In some implementations, the decay of the differential response over time is recorded through multiple observation time channels to eliminate accidental interference at a single moment, and the anomaly of the goaf boundary is confirmed based on the continuous change of the differential response at adjacent observation points.

[0041] In some implementations, the dual receiving coil assembly sequentially spans the entry boundary, the interior of the goaf, and the exit boundary of the goaf; differential response enhancement zones are formed at the entry and exit boundaries, respectively, and the interior of the goaf exhibits a smaller differential response due to the re-approach of the responses received by the two coils.

[0042] In summary, this application has the following advantages compared with the prior art: This application uses a fixed grounding electrical source, and the position and direction of the power supply electrode remain unchanged during the observation process, avoiding the repeated deployment of electrodes and power supply wires at each measuring point, which helps to improve the consistency of observations along the measuring line.

[0043] This application sets up two receiving coils spaced apart along the survey line in the equatorial observation area of ​​a fixed electrical source. Taking advantage of the fact that adjacent positions share a similar background, it suppresses the slowly varying response of the fixed source, the uniform surrounding rock background, and related environmental interferences through differential suppression, thereby highlighting the spatially inconsistent response caused by the goaf boundary.

[0044] This application addresses the characteristic of large lateral extent in mining goaf areas by employing two receiving coils that move along the survey line crossing the boundary of the goaf area. The structure is simple, the number of channels is small, and it is easy to deploy quickly and continuously scan.

[0045] In this application, the two receiving coils independently acquire data and perform differential analysis in the receiver or data processing unit, which can retain the original data from the two receiving positions and facilitate the verification of boundary anomalies.

[0046] The embodiments of this application are described below with reference to the accompanying drawings.

[0047] As shown in Figures 2(a) and 2(b), this application provides a mineral goaf detection device, including a fixed grounding electrical source, a transient electromagnetic transmitter, a dual receiving coil assembly, a dual-channel receiver, and a data processing unit; the fixed grounding electrical source includes a first power supply electrode A and a second power supply electrode B, and the two power supply electrodes are connected to the transient electromagnetic transmitter through power supply wires; The transient electromagnetic transmitter is used to supply pulsed current to the first power supply electrode A and the second power supply electrode B. During the current stabilization period, a primary electromagnetic field is established underground. After the current is turned off, an induced current is formed in the underground conductive medium, which decays and diffuses over time. There are electrical differences between the mining goaf, collapse and fracture zone, fissure zone, or water-filled area and the intact surrounding rock, which causes changes in the induced current path and the distribution of the transient secondary magnetic field.

[0048] The equatorial observation survey line is located to the side of the line connecting the first power supply electrode A and the second power supply electrode B, and is parallel to the line connecting the power supply electrodes. Dual receiving coils are arranged on the equatorial observation survey line and move along the survey line direction. The survey line preferably passes through both sides of the expected goaf boundary, so that the two receiving coils sequentially experience intact surrounding rock, the boundary, the interior of the goaf, the other side boundary, and intact surrounding rock.

[0049] like Figure 3 As shown, the dual-receiving coil assembly includes a first receiving coil R1, a second receiving coil R2, and an insulating support. The first receiving coil R1 and the second receiving coil R2 can be circular, rectangular, multi-turn hollow coils, or magnetic core coils. Preferably, they have the same geometric dimensions, number of turns, and winding direction. The axes of the two coils are kept parallel, and the coil planes are parallel to the ground surface. The insulating support is made of a low-magnetic, low-conductivity material to maintain the spacing and orientation stability of the two receiving coils. The first receiving coil R1 and the second receiving coil R2 are connected to the dual-channel receiver via independent shielded cables. The two coils are not directly connected in reverse series at the analog front end, but instead retain the first channel response and the second channel response respectively. This connection method allows the original responses at both spatial locations to be recorded and differentially processed by the data processing unit.

[0050] like Figure 4 As shown, each receiving channel of the dual-channel receiver includes an input protection module, a low-noise amplification module, a low-pass filter module, an analog-to-digital converter module, and a control module. The control module provides a common sampling clock and time zero point for both channels and receives the synchronization trigger signal from the transient electromagnetic transmitter. The input protection module is used to limit the overvoltage that may occur at the moment of transmission shutdown. The low-noise amplification module is used to improve the amplitude of weak transient response, and the low-pass filter module is used to suppress out-of-band high-frequency interference. The analog-to-digital converter module is used to convert analog induced voltage into digital signal.

[0051] At one observation point, the transient electromagnetic transmitter repeatedly outputs pulse current a preset number of times. After each shutdown, the dual-channel receiver synchronously acquires the decay curves of the differential response of the first receiving coil R1 and the second receiving coil R2 over time. After superimposing the repeated observation results, the data processing unit calculates the differential response of the two channels on the same time track.

[0052] like Figure 5 As shown, when the dual-receiving coil assembly is located above intact surrounding rock, the slow-varying response of the fixed source received by the two coils is approximately consistent with the background of intact surrounding rock, and the differential response is small. As the device moves along the survey line, if the second receiving coil R2 enters the influence range of the goaf first, while the first receiving coil R1 is still located above intact surrounding rock, then the transient response at the two locations will show a significant difference, the differential response will be enhanced, and a first boundary response will be formed.

[0053] As the dual-receiving coil assembly continues to move, when both the first receiving coil R1 and the second receiving coil R2 are located above the influence range of the goaf, which has a large lateral range, the responses received by the two coils tend to converge again, and the differential response decreases. As the device continues to cross the other boundary of the goaf, one coil leaves the influence range of the goaf first while the other coil remains above the goaf, and the differential response strengthens again, forming a second boundary response.

[0054] The first and second boundary responses correspond to the processes of the dual-receiving coil assembly crossing the goaf and entering and leaving the boundary, respectively. The positive and negative directions of the differential response are related to the coil number, the direction of movement, and the electrical differences between the goaf and the relatively intact surrounding rock. In practical interpretation, the boundary is mainly identified based on the significant changes in the differential amplitude, the consistency of multiple time channels, and the spatial continuity of adjacent measuring points, without requiring the boundary anomaly to have a specific positive or negative sign.

[0055] In another embodiment, multiple parallel survey lines can be laid out within the effective equatorial observation area of ​​the same fixed grounded electrical source, and each line can be scanned using a dual-receiving coil assembly to obtain the changes in the goaf boundary at different profile positions. This embodiment is used to improve the degree of control over irregular boundaries, but does not change the basic principle of dual-receiving coils identifying boundaries through differences between adjacent positions.

[0056] In another embodiment, the dual receiving coil assembly can be mounted on a non-metallic trolley, a towed support, or a manually carried support; when using continuous moving observation, the dual-channel receiver can record the received data synchronously with the coil position.

[0057] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0058] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0059] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after the connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after the connection.

[0060] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0061] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A device for detecting goaf points in a mining area, characterized in that, include: Fixed grounding electrical source, transient electromagnetic transmitter, dual receiving coil assembly, dual-channel receiver and data processing unit; A fixed grounding electrical source includes two power supply electrodes; The transient electromagnetic transmitter is used to inject pulse current into two power supply electrodes. After the pulse current is turned off, the induced current in the underground medium diffuses over time and generates a transient secondary magnetic field. The dual-receiving coil assembly is located in the equatorial observation area of ​​a fixed grounded electrical source. The equatorial observation line is set to the side of the line connecting the two power supply electrodes and is parallel to the line connecting the two power supply electrodes. The dual-receiving coil assembly includes two receiving coils, which are independently connected to a dual-channel receiver. The two receiving coils have the same shape, the same number of turns, the same winding direction, and parallel coil axes. The coil plane is parallel to the ground surface and is used to move along the equatorial observation line to receive the time change of the vertical transient magnetic field component, thereby generating an induced voltage. The two-channel receiver is used to synchronously record the induced voltage of the two receiving coils; the data processing unit is used to differentially analyze the induced voltage generated by the two receiving coils, obtain the differential response difference along the equatorial observation line, and identify the boundary of the goaf based on the location of the enhanced differential response.

2. The mining area goaf detection device according to claim 1, characterized in that, When the dual-receiver coil assembly crosses the goaf boundary, with one receiving coil positioned above the goaf-affected area and the other above the intact surrounding rock, the differential response is enhanced, highlighting the spatial non-uniform response caused by the goaf boundary.

3. The mining area goaf detection device according to claim 1, characterized in that, The differential response of the two receiving coils is: ； in, , ; and The induced voltage of the two receiving coils; and These represent the common background components at the locations of the two receiving coils, including the slowly varying response of the fixed electrical source in a local area, the uniform surrounding rock response, and the related interference coupled to the dual-channel receiver simultaneously. and These represent the abnormal responses generated at the locations of the two receiving coils in the goaf of the mining area and its boundary.

4. The mining area goaf detection device according to any one of claims 1 to 3, characterized in that, The dual receiving coil assembly includes two receiving coils and an insulating support; the two receiving coils are circular, rectangular, multi-turn hollow coils or magnetic core coils; the insulating support is used to maintain the spacing and orientation stability of the two receiving coils.

5. The mining area goaf detection device according to claim 1, characterized in that, Each receiving channel of the dual-channel receiver includes an input protection module, a low-noise amplification module, a low-pass filter module, an analog-to-digital conversion module, and a control module; The control module provides a common sampling clock and time zero point for the receiving channel and receives the synchronization trigger signal from the transient electromagnetic transmitter; the input protection module limits the overvoltage that occurs at the moment of transmission shutdown. The low-noise amplifier module is used to improve the transient response amplitude; the low-pass filter module is used to suppress out-of-band high-frequency interference. The analog-to-digital converter module is used to convert analog induced voltage into digital signals.

6. The mining area goaf detection device according to claim 1, characterized in that, At one observation point, a transient electromagnetic transmitter is used to repeatedly output pulse current a preset number of times, and a dual-channel receiver is used to synchronously acquire the decay curve of the differential response of the two receiving coils over time after each shutdown; the data processing unit is used to superimpose the decay curves of the differential response over time of the repeated observations and calculate the differential response on the same time channel.

7. A method for detecting goaf points in a mining area, based on the goaf point detection device according to any one of claims 1 to 6, characterized in that, Specifically, the following steps are included: Step 1: Fix two power supply electrodes at the location in the area to be measured, set up an observation line parallel to the line connecting the power supply electrodes in the equatorial observation area to the side of the electrodes, and set up two receiving coils at intervals along the direction of the observation line; Step 2: A transient electromagnetic transmitter is used to inject pulse current into a fixed grounded electrical source. During the observation gap after the source is turned off, the two receiving coils synchronously receive the induced voltage generated by the underground transient secondary magnetic field. Step 3: Differentiate the induced voltages of the two receiving coils to obtain the differential response difference between two adjacent receiving positions; Step 4: Move the dual receiving coil assembly along the survey line and identify the boundary of the goaf based on the location of the enhanced differential response; the differential response is smaller when both receiving coils are above the same geoelectric medium, and the differential response is enhanced when the two coils are above the intact surrounding rock and the goaf area, respectively.

8. The method for detecting goaf points in a mining area according to claim 7, characterized in that, In step four, the decay of the differential response over time is recorded on multiple observation time channels, and the anomaly of the goaf boundary is confirmed based on the continuous change of the differential response at adjacent observation points.

9. The method for detecting goaf points in a mining area according to claim 7, characterized in that, The dual receiving coil assembly is sequentially spanned across the entry boundary, the interior of the goaf, and the exit boundary of the goaf. Differential response enhancement zones are formed at the entry and exit boundaries to determine the goaf boundary.

10. The method for detecting goaf points in a mining area according to any one of claims 7 to 9, characterized in that, Multiple parallel survey lines were laid out in the effective equatorial observation area of ​​the same fixed grounding electrical source, and scanned using dual receiving coil assemblies to obtain the changes of the goaf boundary at different profile positions.

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