Tunnel in-hole frequency domain electromagnetic advanced detection method and system based on decoupling coil

Abstract

The invention relates to the technical field of tunnel frequency domain electromagnetic advanced detection, and provides a frequency domain electromagnetic advanced detection method and system in a tunnel based on a decoupling coil, and the method comprises the steps: obtaining the vertical magnetic field measurement data of each receiving coil in a decoupling coil device; the vertical magnetic field measurement data of the receiving coils are combined in pairs, and gradient observation data in multiple directions are obtained through differential observation; calculating, for each receiving coil, a first apparent resistivity based on the vertical magnetic field measurement data; for each direction, calculating a second apparent resistivity based on the gradient observation data; and performing error verification based on the first apparent resistivity and the second apparent resistivity, and outputting apparent resistivity distribution. And the apparent resistivity imaging distribution in front of the tunnel face can be quickly, comprehensively and accurately obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel frequency domain electromagnetic advanced detection, and particularly relates to a tunnel hole frequency domain electromagnetic advanced detection method and system based on a decoupling coil. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] Affected by strong plate activity, the construction of dangerous mountainous tunnel (hole) projects faces extremely complex geological conditions such as super-high water pressure and high ground stress, the geological genesis and occurrence characteristics of disaster-causing water bodies and disaster sources such as strong karst are increasingly complex and variable, and the disaster-causing effect is more sudden and destructive, which puts forward higher requirements for the long-distance detection of disaster-causing water bodies.

[0004] At present, the detection distance of the mainstream tunnel electrical method and electromagnetic water detection method is only tens of meters, for example, the detection distance of the transient electromagnetic method is generally about 60 meters (there is a detection blind area), the advanced detection distance of the tunnel induced polarization method is 30-40 meters, and the advanced detection distance of the geological radar method is only 20-30 meters.

[0005] In comparison, the controlled source frequency domain electromagnetic method has the advantages of strong anti-interference ability and large detection depth, and has been widely applied in the fields of mineral resource exploration and groundwater exploration. Based on this, a tunnel frequency domain electromagnetic advanced detection method is proposed, which uses the advantage of "frequency sounding" to realize the detection of disaster-causing water bodies at a farther distance. However, the main problem is that the traditional artificial source frequency domain electromagnetic method (such as the controlled source audio-frequency magnetotelluric method CSAMT) usually requires observation in the far zone, because in the far zone the primary field interference has decayed completely, the wave field form is relatively simple, and it is easy to solve, while the internal space of the tunnel is narrow, the observation distance is limited, resulting in a small transmitting-receiving distance and a high primary field amplitude, which completely covers the secondary field response signal containing geological information, making it difficult to obtain effective geological information. SUMMARY

[0006] In order to solve the technical problems existing in the background art, the present application provides a tunnel hole frequency domain electromagnetic advanced detection method and system based on a decoupling coil, which simultaneously carries out single-point measurement and differential measurement, and through multi-point parallel acquisition and differential analysis, rich multi-gradient observation data can be obtained, and the apparent resistivity obtained based on single-point measurement and differential measurement can be mutually checked, so that the apparent resistivity imaging distribution in front of the tunnel face can be quickly, comprehensively and accurately obtained.

[0007] In order to achieve the above purpose, the present application adopts the following technical solutions: The first aspect of the present application provides a tunnel hole frequency domain electromagnetic advanced detection method based on a decoupling coil, which comprises: Obtaining vertical magnetic field measurement data of each receiving coil in the decoupling coil device; Combining the vertical magnetic field measurement data of the receiving coils two by two, and obtaining multi-directional gradient observation data through differential observation; For each receiving coil, calculating a first apparent resistivity based on the vertical magnetic field measurement data; For each direction, calculating a second apparent resistivity based on the gradient observation data; After error verification based on the first apparent resistivity and the second apparent resistivity, outputting an apparent resistivity distribution.

[0008] Further, the decoupling coil device comprises a transmitting coil, a compensating coil and a plurality of receiving coils; the transmitting coil and the compensating coil are arranged concentrically and coplanarly, forming a weak magnetic flux region in the middle region of the transmitting coil and the compensating coil, and the receiving coils are coplanar with the transmitting coil and arranged in the weak magnetic flux region.

[0009] Further, for the two receiving coils combined, the gradient observation data in the direction of the line connecting the centers of the two receiving coils is , wherein is the distance between the centers of the two receiving coils, and the vertical magnetic field measurement data of the two receiving coils are d and Hzi , respectively. Hzj .

[0010] Further, the first apparent resistivity is . . , wherein is the first apparent resistivity ，i is a complex number, is an angular frequency, is the air permeability, is the vertical magnetic field measurement data of the receiving coil, and the wave number , is the resistivity value, f is the frequency, and are the radii of the transmitting coil and the compensating coil, respectively, and are the current values input by the transmitting coil and the compensating coil, respectively, and are the number of turns of the transmitting coil and the compensating coil, respectively, and the intermediate parameter , is an integral variable, is the transmitting-receiving offset distance, and represent the zeroth-order and first-order Bessel functions, respectively.

[0011] Further, the second apparent resistivity is: ; ; ; wherein, is the second apparent resistivity, r i and r j are the transceiver offsets of the receiving coil Rxi and the receiving coil Rxj respectively, is the gradient observation data, i is a complex number, is the angular frequency, is the air permeability, the wave number , is the resistivity value, f is the frequency, and are the radii of the transmitting coil and the compensation coil respectively, and are the current values input by the transmitting coil and the compensation coil respectively, and are the number of turns of the transmitting coil and the compensation coil respectively, intermediate parameters , is the integral variable, and represent the zeroth order and first order Bessel functions respectively.

[0012] The second aspect of the present application provides a tunnel hole inside frequency domain electromagnetic advanced detection system based on decoupling coil, which comprises: a data acquisition module configured to acquire the vertical magnetic field measurement data of each receiving coil in the decoupling coil device; a difference observation module configured to combine the vertical magnetic field measurement data of the receiving coils two by two, and obtain multi-directional gradient observation data through difference observation; a first calculation module configured to calculate the first apparent resistivity based on the vertical magnetic field measurement data for each receiving coil; a second calculation module configured to calculate the second apparent resistivity based on the gradient observation data for each direction; a verification module configured to output the apparent resistivity distribution after error verification based on the first apparent resistivity and the second apparent resistivity.

[0013] Further, the decoupling coil device comprises a transmitting coil, a compensating coil and a plurality of receiving coils; the transmitting coil and the compensating coil are arranged concentrically and coplanarly, a weak magnetic flux area is formed in the middle area of the transmitting coil and the compensating coil, and the receiving coils are coplanar with the transmitting coil and arranged in the weak magnetic flux area.

[0014] Further, for the combined two receiving coils, the gradient observation data in the direction of the line connecting the centers of the two receiving coils is , wherein, d is the distance between the centers of the two receiving coils, and the vertical magnetic field measurement data of the two receiving coils are Hzi and Hzj .

[0015] Further, the first apparent resistivity is: ; ; wherein, is the first apparent resistivity ，i is a complex number, is an angular frequency, is the magnetic permeability of air, is the vertical magnetic field measurement data of the receiving coil, and the wave number , is the resistivity value, f is the frequency, and are the radii of the transmitting coil and the compensating coil, respectively, and are the current values inputted by the transmitting coil and the compensating coil, respectively, and are the number of turns of the transmitting coil and the compensating coil, respectively, and the intermediate parameter , is an integral variable, is the transmitter-receiver offset distance, and represent the zeroth-order and first-order Bessel functions, respectively.

[0016] Further, the second apparent resistivity is: ; ; ; wherein, is the second apparent resistivity, r i and r j are the transmitter-receiver offset distances of the receiving coil Rxi and the receiving coil Rxj, respectively, For gradient observation data, i It is a complex number. Angular frequency, air permeability, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, and These represent the zeroth-order and first-order Bessel functions, respectively.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention simultaneously performs single-point measurement and differential measurement. Through multi-point parallel acquisition and differential analysis, it can obtain rich multi-gradient observation data. Furthermore, it cross-verifies the apparent resistivity obtained based on single-point measurement and differential measurement, enabling rapid, comprehensive, and accurate acquisition of the apparent resistivity imaging distribution in front of the tunnel face.

[0018] This invention proposes a differential gradient observation method that randomly combines multiple receiving coils in pairs. This method can not only acquire vertical magnetic field data of a single receiving coil, but also obtain magnetic field gradient observation data in multiple directions. The gradient data is more sensitive to changes in the resistivity of the underground medium, especially in the narrow space of a tunnel. Multi-directional gradient observation can reflect the distribution characteristics of the geological body in front from different angles, effectively improving the ability and resolution to identify small-scale, low-resistivity or high-resistivity anomalies. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, 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 improper limitation of the invention.

[0020] Figure 1 This is a layout diagram of the electromagnetic device according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the decoupling coil device according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the observation points in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the apparent resistivity calculation results in scenario one of the embodiments of the present invention; Figure 5This is a schematic diagram of the tunnel dual-anomaly geological model according to Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the apparent resistivity calculation results in scenario two of embodiment one of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] Example 1 This embodiment provides a frequency domain electromagnetic advance detection method for tunnels based on decoupling coils.

[0024] The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils provided in this embodiment, such as Figure 1 As shown, it relies on an electromagnetic device installed inside the tunnel.

[0025] In this embodiment, the electromagnetic device is a decoupling coil device. The decoupling coil device effectively cancels out the primary field interference generated by the original transmitting coil on the receiving coil by introducing a compensation coil with a reverse magnetic moment, thereby achieving direct acquisition of the pure secondary field frequency domain electromagnetic response signal.

[0026] like Figure 2 As shown, the decoupling coil device includes a transmitting coil, a compensating coil, and several receiving coils. The transmitting coil and the compensating coil are arranged concentrically and coplanarly, exciting currents of the same direction but different magnitudes. By precisely controlling key parameters such as the current magnitude, number of turns, and radius of the transmitting coil and the compensating coil, a weak magnetic flux region is formed in the middle region of the two coils, so that the total primary magnetic flux through the receiving coil is zero, achieving effective cancellation of the primary field. The receiving coil is coplanar with the transmitting coil and the compensating coil and is arranged in the weak magnetic flux region. The primary magnetic flux of the transmitting coil and the compensating coil to the receiving coil is equal.

[0027] The decoupling coil device introduces a compensation coil with a reverse magnetic moment into the transmitting coil, so that the primary magnetic flux at the receiving coil approaches zero. Thus, under near-zero offset conditions, it effectively suppresses primary field interference, directly obtains the frequency domain electromagnetic response signal of the pure secondary field, and significantly improves the data signal-to-noise ratio.

[0028] The decoupling coil device integrates a receiving coil array, giving it the significant advantage of "one-time transmission, multiple-point reception".

[0029] The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils provided in this embodiment includes the following steps: Step 1: Determine the device parameters of the decoupling coil device and supply the set current waveform to the transmitting coil and the compensation coil.

[0030] The device parameters include the radius, current, and number of turns of the transmitting coil and the compensation coil.

[0031] Step 2: Obtain the vertical magnetic field measurement data of each receiving coil in the decoupling coil device.

[0032] Step 3: The vertical magnetic field measurement data of multiple receiving coils are randomly combined in pairs, and gradient observation data in multiple directions are obtained through differential observation.

[0033] Specifically, two receiving coils, Rxi and Rxj, are randomly selected to obtain the corresponding vertical magnetic field measurement data Hzi and Hzj, and the gradient is calculated by differential calculation, that is, the direction of the line connecting the centers of the two receiving coils is obtained. Gradient observation data , where d is the distance between the centers of the two receiving coils; by randomly combining two receiving coils, multi-angle gradient observation data can be obtained.

[0034] Step 4: For each receiving coil, calculate the first apparent resistivity based on the vertical magnetic field measurement data and the device parameters.

[0035] The formula for calculating the first apparent resistivity is as follows: ; ; in, Let i be the first apparent resistivity, and i be a complex number. Angular frequency, air permeability, This refers to the vertical magnetic field measurement data of a certain receiving coil. , wave number , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, This is the transmit / receive offset. and These represent the zeroth-order and first-order Bessel functions, respectively.

[0036] The derivation of the first apparent resistivity is as follows: The analytical formula for the perpendicular magnetic field strength of a single transmitting coil in a uniform all-space medium is: ;in, I The current value input to a single transmitting coil. a The radius of a single transmitting coil; According to the principle of electromagnetic field vector superposition, the formula for calculating the vertical magnetic field component of the decoupling coil device in a uniform all-space medium is as follows: ; Multiply both sides of the equation by the wave number. Rearranging the above equation, the formula for calculating the first apparent resistivity can be defined as follows: .

[0037] Step 5: For each direction, calculate the second apparent resistivity based on gradient observation data and device parameters.

[0038] The formula for calculating the second apparent resistivity is as follows: ; ; ; in, The second apparent resistivity, r i and r j These are the transmit / receive offsets of receiving coils Rxi and Rxj, respectively. This refers to the vertical magnetic field gradient observation data. .

[0039] This embodiment innovatively proposes a differential gradient observation method using random pairwise combinations of multiple receiving coils. This method can not only acquire vertical magnetic field data from a single receiving coil but also obtain multi-directional magnetic field gradient observation data. Gradient data is more sensitive to changes in the resistivity of the underground medium, especially in the confined space of a tunnel. Multi-directional gradient observation can reflect the distribution characteristics of geological bodies ahead from different angles, effectively improving the ability and resolution to identify small-scale, low-resistivity, or high-resistivity anomalies.

[0040] Step 6: After error verification based on the first and second apparent resistivity, output the apparent resistivity distribution, that is, the first apparent resistivity of each receiving coil and the second apparent resistivity in each direction.

[0041] Specifically, for a certain direction, the first apparent resistivity of the two receiving coils corresponding to that direction is obtained, the average of the first apparent resistivity of the two receiving coils is calculated, and compared with the second apparent resistivity in that direction. If the error between the two is less than a threshold, the first apparent resistivity of each receiving coil and the second apparent resistivity in each direction are output; otherwise, return to step 2.

[0042] This embodiment introduces a dual apparent resistivity error verification mechanism. By comparing the error between the average first apparent resistivity and the second apparent resistivity in the same direction, the validity of the data is determined. If the error exceeds the threshold, the data is re-acquired. This closed-loop verification process can effectively eliminate noise interference and abnormal data, ensuring that the final output apparent resistivity distribution result is more reliable.

[0043] like Figure 1 As shown in Scenario 1: A water-rich fault measuring 80m × 80m × 10m exists 100m ahead of the tunnel face. The background resistivity is 1000 Ω·m, and the resistivity of the water-rich fault is 1 Ω·m. The calculation frequency of the decoupling coil device is 10Hz to 1000kHz. Measurement points are as follows... Figure 3 As shown, the measuring points are distributed along the y-direction on the working face, with a distance of 1m between adjacent measuring points. The apparent resistivity distribution is as follows. Figure 4 As shown, the horizontal axis represents frequency. The higher the frequency, the shallower the depth of reflection, and the lower the frequency, the deeper the depth of reflection. Figure 4 The white dashed box in the middle indicates the approximate location of the water-rich fault, so the calculated apparent resistivity distribution can basically reflect the distribution of the water-rich fault.

[0044] like Figure 5 As shown in Scenario 2: There are two water-rich faults ahead of the tunnel face. The closer fault measures 20m × 20m × 5m, is 20m from the face, and has a resistivity of 5Ω·m. The farther fault measures 100m × 100m × 10m, is 120m from the face, and has a resistivity of 1Ω·m. The surrounding rock resistivity is 1000Ω·m. The calculation frequency of the decoupling coil device is 10Hz to 1000kHz. Figure 6 As shown, the apparent resistivity distribution map clearly reflects the existence of two water-rich faults. Based on the frequency, the location of the water-rich faults can be further determined.

[0045] The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils provided in this embodiment simultaneously conducts single-point measurement and differential measurement. Through multi-point parallel acquisition and differential analysis, rich multi-gradient observation data can be obtained. Furthermore, the apparent resistivity obtained based on single-point measurement and differential measurement is cross-verified, which can quickly, comprehensively and accurately obtain the apparent resistivity imaging distribution in front of the tunnel face.

[0046] Example 2 The frequency domain electromagnetic advance detection system for tunnels based on decoupling coils provided in this embodiment includes: The data acquisition module is configured to acquire vertical magnetic field measurement data of each receiving coil in the decoupling coil device; The differential observation module is configured to combine the vertical magnetic field measurement data of the receiving coil in pairs and obtain gradient observation data in multiple directions through differential observation. The first calculation module is configured to: for each receiving coil, calculate a first apparent resistivity based on vertical magnetic field measurement data; The second calculation module is configured to calculate the second apparent resistivity for each direction based on gradient observation data. The verification module is configured to perform error verification based on the first and second apparent resistivity, and then output the apparent resistivity distribution.

[0047] Furthermore, the decoupling coil device includes a transmitting coil, a compensating coil, and several receiving coils; the transmitting coil and the compensating coil are arranged concentrically and coplanarly, forming a weak magnetic flux region in the middle area between the transmitting coil and the compensating coil, and the receiving coil is coplanar with the transmitting coil and arranged in the weak magnetic flux region.

[0048] Furthermore, for the two combined receiving coils, the direction of the line connecting the centers of the two receiving coils is... The gradient observation data on the above are ,in, d The distance between the centers of the two receiving coils is given. The measured data of the vertical magnetic field of the two receiving coils are as follows: Hzi and Hzj .

[0049] Furthermore, the first apparent resistivity is: ; ; in, First apparent resistivity ，i It is a complex number. Angular frequency, air permeability, To receive the vertical magnetic field measurement data of the receiving coil, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, This is the transmit / receive offset. and These represent the zeroth-order and first-order Bessel functions, respectively.

[0050] Furthermore, the second apparent resistivity is: ; ; ; in, The second apparent resistivity, r i and r j These are the transmit / receive offsets of receiving coils Rxi and Rxj, respectively. For gradient observation data, i It is a complex number. Angular frequency, air permeability, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, and These represent the zeroth-order and first-order Bessel functions, respectively.

[0051] It should be noted that each module in this embodiment corresponds one-to-one with each step in Embodiment 1, and their specific implementation processes are the same, so they will not be repeated here.

[0052] 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, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A frequency-domain electromagnetic advance detection method for tunnels based on decoupling coils, characterized in that, include: Acquire vertical magnetic field measurement data of each receiving coil in the decoupling coil device; The vertical magnetic field measurement data of the receiving coil are combined in pairs, and gradient observation data in multiple directions are obtained through differential observation. For each receiving coil, the first apparent resistivity is calculated based on the vertical magnetic field measurement data; For each direction, the second apparent resistivity is calculated based on gradient observation data; Based on the first and second apparent resistivity, after error verification, the apparent resistivity distribution is output.

2. The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils as described in claim 1, characterized in that, The decoupling coil device includes a transmitting coil, a compensating coil, and several receiving coils; the transmitting coil and the compensating coil are arranged concentrically and coplanarly, forming a weak magnetic flux region in the middle area between the transmitting coil and the compensating coil, and the receiving coils are coplanar with the transmitting coil and arranged in the weak magnetic flux region.

3. The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils as described in claim 1, characterized in that, For a combination of two receiving coils, the direction of the line connecting the centers of the two receiving coils... The gradient observation data on the above are ,in, d The distance between the centers of the two receiving coils is given. The measured data of the vertical magnetic field of the two receiving coils are as follows: Hzi and Hzj .

4. The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils as described in claim 1, characterized in that, The first apparent resistivity is: ； ； in, First apparent resistivity ，i It is a complex number. Angular frequency, air permeability, To receive the vertical magnetic field measurement data of the receiving coil, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, This is the transmit / receive offset. and These represent the zeroth-order and first-order Bessel functions, respectively.

5. The frequency domain electromagnetic advance detection method for tunnels based on decoupling coils as described in claim 1, characterized in that, The second apparent resistivity is: ； ； ； in, The second apparent resistivity, r i and r j These are the transmit / receive offsets of receiving coils Rxi and Rxj, respectively. For gradient observation data, i It is a complex number. Angular frequency, air permeability, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, and These represent the zeroth-order and first-order Bessel functions, respectively.

6. A frequency-domain electromagnetic advance detection system for tunnels based on decoupling coils, characterized in that, include: The data acquisition module is configured to acquire vertical magnetic field measurement data of each receiving coil in the decoupling coil device; The differential observation module is configured to combine the vertical magnetic field measurement data of the receiving coil in pairs and obtain gradient observation data in multiple directions through differential observation. The first calculation module is configured to: for each receiving coil, calculate a first apparent resistivity based on vertical magnetic field measurement data; The second calculation module is configured to calculate the second apparent resistivity for each direction based on gradient observation data. The verification module is configured to perform error verification based on the first and second apparent resistivity, and then output the apparent resistivity distribution.

7. The tunnel frequency domain electromagnetic advance detection system based on decoupling coils as described in claim 6, characterized in that, The decoupling coil device includes a transmitting coil, a compensating coil, and several receiving coils; the transmitting coil and the compensating coil are arranged concentrically and coplanarly, forming a weak magnetic flux region in the middle area between the transmitting coil and the compensating coil, and the receiving coils are coplanar with the transmitting coil and arranged in the weak magnetic flux region.

8. The tunnel frequency domain electromagnetic advance detection system based on decoupling coils as described in claim 6, characterized in that, For a combination of two receiving coils, the direction of the line connecting the centers of the two receiving coils... The gradient observation data on the above are ,in, d The distance between the centers of the two receiving coils is given. The measured data of the vertical magnetic field of the two receiving coils are as follows: Hzi and Hzj .

9. The tunnel frequency domain electromagnetic advance detection system based on decoupling coils as described in claim 6, characterized in that, The first apparent resistivity is: ； ； in, First apparent resistivity ，i It is a complex number. Angular frequency, air permeability, To receive the vertical magnetic field measurement data of the receiving coil, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, This is the transmit / receive offset. and These represent the zeroth-order and first-order Bessel functions, respectively.

10. The tunnel frequency domain electromagnetic advance detection system based on decoupling coils as described in claim 6, characterized in that, The second apparent resistivity is: ； ； ； in, The second apparent resistivity, r i and r j These are the transmit / receive offsets of receiving coils Rxi and Rxj, respectively. For gradient observation data, i It is a complex number. Angular frequency, air permeability, wavenumber , This is the resistivity value. f For frequency, and These are the radii of the transmitting coil and the compensation coil, respectively. and These are the current values ​​input to the transmitting coil and the compensation coil, respectively. and These are the number of turns of the transmitting coil and the compensation coil, respectively, and intermediate parameters. , For integration variables, and These represent the zeroth-order and first-order Bessel functions, respectively.

Images