Short-distance detection device for goaf of fluorite mine

Abstract

The invention discloses a short-distance detection device for a goaf of a fluorite mine, and belongs to the technical field of detection equipment, and the short-distance detection device comprises a magnetic field measuring instrument and a data processing system which are used for determining the distribution condition of measuring lines of a measuring area according to collected parameters, transmitting transient electromagnetic waves to each measuring line of the measuring area, and detecting transient feedback electromagnetic waves fed back by each measuring line; performing inversion analysis on the feedback electromagnetic wave of each measuring line, and obtaining inversion resistivity and depth data of each measuring line according to an inversion analysis result; according to the inversion resistivity and depth data of each measuring line, a low-resistance abnormal area and a goaf abnormal area in the goaf are determined; the boundary position of the goaf is determined according to the low-resistance abnormal area and the goaf abnormal area in combination with geological and geophysical information, and the short-distance detection precision and efficiency of the fluorite mine goaf are improved.

Description

Technical Field

[0001] This invention belongs to the field of detection equipment technology, specifically relating to a short-range detection device for fluorite mine goaf areas. Background Technology

[0002] Goaf areas are "cavities" created by mining mineral resources beneath the surface. Due to the large number of untreated mining sites, chambers, and tunnels left over from mining, goaf areas are characterized by strong concealment, poor spatial distribution patterns, and unpredictable roof collapses. They pose a significant safety hazard to any new construction projects that pass through or through goaf areas. Therefore, major railway and highway projects often adopt bypass strategies when passing through mining areas. For mining areas where bypass conditions are poor and costs are high, reinforcement treatment is necessary after clarifying the distribution characteristics of goaf areas on both sides of the railway line. Therefore, accurately obtaining the spatial patterns and distribution range of goaf areas within the railway line's influence area is a prerequisite for bypassing or reinforcement.

[0003] Existing methods for detecting goaf areas mainly include three types. The first is using large geological testing equipment. However, because the location of goaf areas is unpredictable and the equipment is very heavy, deploying such equipment within the goaf area can easily trigger geological collapses, posing a risk of workers and equipment falling into the goaf. The second method is establishing a ground pressure monitoring network for long-term effective monitoring. However, establishing such a network typically takes too long, and because goaf areas vary in size, the network cannot accurately monitor smaller goaf areas, resulting in low accuracy. The third method is geophysical methods, which indirectly measure goaf areas by measuring the distribution of stratigraphic resistivity (high-density resistivity method) or dielectric constant (ground-based radar). The resistivity method relies on volumetric effects and suffers from low spatial resolution, while radar has a shallow detection depth, further contributing to low accuracy. Summary of the Invention

[0004] This invention provides a short-range detection device for fluorite mine goaf areas, comprising: a magnetic field measuring instrument and a data processing system. The magnetic field measuring instrument is deployed at the detection point to collect data. The data processing system establishes different geophysical numerical models based on the geological and geophysical information of the survey area, performs forward modeling on the geophysical numerical models to obtain transient electromagnetic response characteristics under different parameters, determines the detection parameters of the survey area based on the simulation results, conducts detection experiments at typical measurement points in the survey area to verify the selected detection parameters, and determines the acquisition parameters based on the verification results. Based on the acquisition parameters, the distribution of survey lines in the survey area is determined, transient electromagnetic waves are emitted to each survey line in the survey area, and the transient feedback electromagnetic waves fed back from each survey line are detected.

[0005] Furthermore, the feedback electromagnetic waves of each survey line are inverted and analyzed, and the inverted resistivity and depth data of each survey line are obtained based on the inversion analysis results.

[0006] Furthermore, based on the inversion resistivity and depth data of each survey line, the low resistivity anomaly zone and the goaf anomaly zone within the goaf area are determined; based on the low resistivity anomaly zone and the goaf anomaly zone, combined with geological and geophysical information, the boundary location of the goaf area is determined.

[0007] Furthermore, the detector employs a magnetic field measuring instrument, which includes a measuring instrument body and a base for supporting multi-stage magnets; a first turntable and a second turntable are disposed opposite to each other on the base and are rotatably connected to the base respectively, and the axis of the first turntable coincides with the axis of the second turntable.

[0008] Furthermore, the first positioning fixture is connected to the side of the first turntable facing the second turntable, and the second positioning fixture is connected to the side of the second turntable facing the first turntable.

[0009] Furthermore, the first positioning fixture has multiple first limiting points, and the second positioning fixture has multiple second limiting points that correspond one-to-one with the multiple first limiting points. The wire passes around the corresponding first limiting points and second limiting points and is threaded through the multi-stage magnet.

[0010] Furthermore, the wire located between the first limiting point and the second limiting point is parallel to the axis of the first turntable, and the distance between it and the axis of the first turntable is less than the inner circumference of the multi-stage magnet.

[0011] The beneficial effects of this invention include: This invention provides a short-range detection device for fluorite mine goaf areas, including a magnetic field measuring instrument and a data processing system. Based on collected parameters, the distribution of survey lines in the survey area is determined. Transient electromagnetic waves are emitted to each survey line in the survey area, and the transient feedback electromagnetic waves from each survey line are detected. The feedback electromagnetic waves from each survey line are inverted and analyzed to obtain the inversion resistivity and depth data for each survey line. Based on the inversion resistivity and depth data of each survey line, low-resistivity anomaly zones and goaf anomaly zones within the goaf area are determined. Based on the low-resistivity anomaly zones and goaf anomaly zones, combined with geological and geophysical information, the boundary location of the goaf area is determined, thus improving the accuracy and efficiency of short-range detection of fluorite mine goaf areas. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of a short-range detection device for a fluorite mine goaf in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the disassembled close-range detection device for fluorite mine goaf according to the present invention; Figure 3 This is a schematic diagram of the electric field response of a low-resistivity anomaly on the earth's surface according to the present invention. The components include: 1. Magnetic field measuring instrument; 11. Measuring instrument body; 12. Multi-stage magnet; 13. Base. Detailed Implementation

[0014] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0015] This invention discloses a short-range detection device for fluorite mine goaf areas, comprising a magnetic field measuring instrument and a data processing system. The magnetic field measuring instrument is deployed at the detection point to collect data. The data processing system establishes different geophysical numerical models based on the geological and geophysical information of the survey area, performs forward modeling on the geophysical numerical models to obtain transient electromagnetic response characteristics under different parameters, determines the detection parameters of the survey area based on the simulation results, conducts detection experiments at typical measurement points in the survey area to verify the selected detection parameters, and determines the acquisition parameters based on the verification results, determines the distribution of survey lines in the survey area based on the acquisition parameters, transmits transient electromagnetic waves to each survey line in the survey area, and detects the transient feedback electromagnetic waves fed back from each survey line, performs inversion analysis on the feedback electromagnetic waves of each survey line, and obtains the inversion resistivity and depth data of each survey line based on the inversion analysis results, determines the low resistivity anomaly zone and the goaf anomaly zone within the goaf area based on the inversion resistivity and depth data of each survey line, and determines the boundary location of the goaf area based on the low resistivity anomaly zone and the goaf anomaly zone, combined with geological and geophysical information.

[0016] The detector employs a magnetic field measuring instrument 1, which includes a measuring instrument body 11 and a base 13 for supporting multi-stage magnets 12. A first turntable and a second turntable are disposed opposite to each other on the base 13 and are rotatably connected to the base 13 respectively. The axis of the first turntable coincides with the axis of the second turntable. A first positioning fixture is connected to the side of the first turntable facing the second turntable, and a second positioning fixture is connected to the side of the second turntable facing the first turntable. The first positioning fixture has multiple first limiting points, and the second positioning fixture has multiple second limiting points corresponding one-to-one with the multiple first limiting points. A wire passes around the corresponding first limiting point and second limiting point and passes through the multi-stage magnet. The wire located between the first limiting point and the second limiting point is parallel to the axis of the first turntable, and the distance between the wire and the axis of the first turntable is less than the inner circumference radius of the multi-stage magnet.

[0017] Controlled-Source Audio-Frequency Magnetotellurics (CSAMT) is a frequency sounding method using artificial field sources. It boasts advantages such as high signal strength, high efficiency, high lateral and longitudinal resolution, and clear structural reflection, and has been widely used in recent years for detecting goaf areas. However, when local conductive inhomogeneities exist on the surface, the Carnia apparent resistivity curve exhibits a static effect of multiple shifts in a logarithmic coordinate system. This effect can lead to false structures or anomalies appearing vertically in the cross-sectional view, severely affecting the CSAMT results. Currently, there are various static correction methods, mainly including filtering, wavelet transform, and curve translation. Curve translation is the most commonly used method to eliminate static displacement. It utilizes the translation characteristics of the Carnia apparent resistivity curve in a logarithmic coordinate system to shift the curve vertically to achieve correction. However, this method lacks a standard correction value, often resulting in under- or over-correction.

[0018] Based on the characteristics of the Transient Electromagnetic Method (TEM) in directly measuring magnetic field data and thus effectively avoiding the influence of shallow inhomogeneities, the CSAMT curve was shifted using TEM magnetic field data as a reference, effectively suppressing the static effect of CSAMT.

[0019] Static effects, based on the characteristics of electromagnetic fields, indicate that in a horizontally homogeneous layered medium, the direction of the current field is parallel to the interface, and no charge accumulates at the interface. When local inhomogeneities exist at or near the surface, the observed electric field will be distorted due to their influence. Current converges in low-resistivity areas and diverges in high-resistivity areas.

[0020] When a stream flows through the interface of an inhomogeneous volume, charge accumulates on the boundary surface. The charge volume density in the medium can be expressed as:

[0021] In the formula, σ is the conductivity, ε0 ​​is the permittivity, and E is the primary electric field. The secondary electric field generated by the accumulated charge is:

[0022] In the formula It is a secondary magnetic vector potential field. It is the electrostatic potential generated by accumulated charge. If the electromagnetic field penetrates to a depth greater than the size of the inhomogeneous body, due to the secondary magnetic vector potential... The electric field that varies with time is very small compared to the electrostatic field and can be neglected. Therefore, the secondary electric field is independent of frequency. According to Coulomb's law:

[0023] In the formula, r represents the volume element from the observation point to the non-uniform volume. Distance vector between, It is the charge density, and r0 is the unit vector of r.

[0024] Carnia apparent resistivity Defined as the ratio of electric field to magnetic field. To induce a magnetic field:

[0025] It is known that the additional field generated by the accumulated charge at the interface of the inhomogeneous body is proportional to the background field. When an inhomogeneous body is present, the secondary electric field value increases or decreases by a factor, causing the calculated Carnia apparent resistivity value to also change by a factor. Compared with the case without an inhomogeneous body, the curve will have an up-and-down shift characteristic, which is the static displacement. However, the magnetic field is not affected by this. Therefore, magnetic field data can be measured to help correct CSAMT data and eliminate static displacement.

[0026] EM directly measures magnetic field data and calculates apparent resistivity using the measured magnetic field components. It is insensitive to changes in lateral resistivity, and the calculated apparent resistivity effectively avoids the influence of shallow inhomogeneities. Early TEM data contained errors due to calculations in later formulas; therefore, later TEM data was used as a reference to correct the static displacement of the CSAMT sounding curve.

[0027] The skin depth formula for CSAMT in a uniform half-space is:

[0028] In the formula, f is the detection frequency of CSAMT. The skin depth formula of TEM in a uniform half-space of the ground is:

[0029] In the formula, t is the detection time in the late stage of TEM (in seconds).

[0030] make = Then there is

[0031] The time of the late TEM is converted into the corresponding frequency. The late TEM and CSAMT responses are compared. The difference in apparent resistivity between the two is the static displacement. The CSAMT curve is shifted to eliminate the static displacement.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A short-range detection device for fluorite mine goaf areas, characterized in that, include: The magnetic field measuring instrument and data processing system are used to collect data at the detection points. The data processing system establishes different geophysical numerical models based on the geological and geophysical information of the survey area and performs forward modeling on the geophysical numerical models to obtain transient electromagnetic response characteristics under different parameters. Based on the simulation results, the detection parameters of the survey area are determined. Detection tests are carried out at typical measurement points in the survey area to verify the selected detection parameters. The acquisition parameters are determined based on the verification results. The distribution of the survey lines in the survey area is determined based on the acquisition parameters. Transient electromagnetic waves are emitted to each survey line in the survey area, and the transient feedback electromagnetic waves fed back from each survey line are detected.

2. The short-range detection device for fluorite mine goaf as described in claim 1, characterized in that, The feedback electromagnetic waves of each survey line are inverted and analyzed, and the inverted resistivity and depth data of each survey line are obtained based on the inversion analysis results.

3. The short-range detection device for fluorite mine goaf as described in claim 2, characterized in that, Based on the inversion resistivity and depth data of each survey line, the low resistivity anomaly zone and the goaf anomaly zone within the goaf area are determined; based on the low resistivity anomaly zone and the goaf anomaly zone, combined with geological and geophysical information, the boundary location of the goaf area is determined.

4. The short-range detection device for fluorite mine goaf as described in claim 1, characterized in that, The detector uses a magnetic field measuring instrument, which includes the measuring instrument body and a base for supporting multi-stage magnets; the first turntable and the second turntable are arranged opposite to each other on the base and are rotatably connected to the base respectively, and the axis of the first turntable coincides with the axis of the second turntable.

5. A short-range detection device for fluorite mine goaf as described in claim 4, characterized in that, The first positioning fixture is connected to the side of the first turntable facing the second turntable, and the second positioning fixture is connected to the side of the second turntable facing the first turntable.

6. The short-range detection device for fluorite mine goaf as described in claim 5, characterized in that, The first positioning fixture has multiple first limiting points, and the second positioning fixture has multiple second limiting points that correspond one-to-one with the multiple first limiting points. The wire passes around the corresponding first limiting points and second limiting points and is threaded through a multi-stage magnet.

7. A short-range detection device for fluorite mine goaf as described in claim 6, characterized in that, The wire located between the first limiting point and the second limiting point is parallel to the axis of the first turntable, and the distance between the wire and the axis of the first turntable is less than the inner circumference of the multi-stage magnet.

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