An omnidirectional conductivity tracing exploration device

Abstract

The present invention discloses an omnidirectional apparent conductivity tracing exploration device, including a field device for exploration, a data acquisition system, a data collation and diagram system, and a data analysis and interpretation system. The omnidirectional apparent conductivity data of dense measuring points can be obtained through the provided field device and data acquisition system, and the planar position of the target body can be determined through the provided data collation and diagram system; the provided data analysis and interpretation system is used to adjust the frequency of the transmitted signal, and then analyze the characteristics of the received signal at different frequencies, which is used to qualitatively evaluate the buried depth of the target body. Compared with the traditional artificial field source frequency domain electromagnetic dipole profiling method, the present invention has better exploration effect, can effectively solve the engineering exploration problems such as the exploration of PE pipelines, has the advantages of strong anti-interference ability and large transmission power, and its emission peak magnetic moment can reach nearly 1,000 Am 2 , small footprint, weak volume effect, can more quickly identify whether there are targets such as PE pipes underground, and effectively solve difficult detection problems.

Description

Technical Field

[0001] The invention relates to the technical field of geophysical exploration, in particular to an omnidirectional apparent conductivity tracing exploration device. Background Art

[0002] In recent years, with the extensive and in-depth development of engineering construction, the demand for geophysical exploration (hereinafter referred to as geophysical exploration) of shallow (less than ten meters underground) geological bodies or buried objects has become increasingly widespread and complex, including special needs under specific environments, and positioning detection of PE pipelines is one of them.

[0003] PE pipes are polyethylene pipes, which have been widely used in water pipes, gas pipes, heating pipes and other pipes in recent years. The pipe body itself is non-magnetic, has poor conductivity and good plasticity. Based on the above physical properties, it is difficult to detect the specific buried position of the pipeline using magnetic measurement, conventional electrical method and elastic wave method. Due to the construction environment (disturbance of human and vehicle flow, inability to ground electrodes or detectors, high background noise, etc.), many methods cannot be constructed in the field. At present, the positioning and detection of PE pipelines (especially PE pipelines without buried tracer wires) is still a technical problem.

[0004] The artificial field source frequency domain ground electromagnetic method involved in the present invention is a type of geophysical exploration technology. The present invention belongs to the branch of magnetic dipole horizontal coil profiling method under its classification. The principle of the method is summarized as follows:

[0005] As attached Figure 1As shown: In the existing method, the transmitter inputs a harmonic current (sine or cosine wave) of a certain frequency into the transmitting coil (a multi-turn coil with an air core or a magnetic core, generally circular or square) T, and the transmitting coil generates a primary magnetic field H1. Excited by H1, the underground medium (stratum, buried objects, etc.) will generate a secondary electric field E2. The magnitude of E2 is positively correlated with the conductivity of the underground medium (because the influence of the medium magnetic permeability on E2 is relatively weak, the influence of the magnetic permeability is ignored). E2 will generate a secondary magnetic field H2, which is detected by the receiving coil (a multi-turn coil with an air core or a magnetic core, generally circular or square) R and input into the receiver, and then amplified, converted and stored to form H2 harmonic magnetic field signal data with the same transmitting frequency. By analyzing the amplitude, Phase and other information can be used to infer or invert the conductivity of the underground medium between TRs (observations corresponding to a certain TR position can collect and infer an apparent resistivity or apparent conductivity value); this conductivity data is a comprehensive measure of the conductivity of the underground medium between TRs (not the apparent conductivity corresponding to a specific point), with a clear volume effect. The larger the TR spacing, the more significant the volume effect and the coarser the spatial resolution; by translating the TR system along the survey line or changing the TR plane position, a profile curve for evaluating the quality of conductivity can be obtained. By analyzing the high and low changes (abnormalities) of the curve, the spatial strength changes of the conductivity of the underground medium can be inferred; if the observed profiles are arranged regularly, a profile map or a plane contour map can be drawn to analyze the plane characteristics of the conductivity of the underground medium. In the above method, the diameter of the TR coil is generally not large (tens of centimeters to several meters), and there are many types of devices (referring to the relative placement and orientation of the TRs), which will not be repeated here. For a detailed introduction to the artificial field source frequency domain electromagnetic dipole profile method, please refer to "Introduction to Geophysical Exploration".

[0006] Based on the above method, the apparent conductivity of the underground medium calculated is a modulus, which can only reflect the strength of conductivity, has no directionality, and cannot determine the anisotropy of the underground medium. Its measurement parameter--apparent conductivity has obvious volume effect, and its spatial resolution depends on many factors such as device size, signal frequency, and measurement point density. The direct use of this method to detect underground media such as PE pipes is not ideal. The target anomaly (caused by target bodies such as PE pipes) in the apparent conductivity cross-section map (or plane contour map) is masked by the background anomaly (caused by the spatial change of stratum-like media or backfill), and the linear features are not obvious. It is difficult to determine the position of the target body through the map, so there are certain technical defects. Summary of the invention

[0007] The purpose of the present invention is to provide an omnidirectional apparent conductivity tracing exploration device. By essentially changing the observation device, observation method, and data sorting and analysis mode adopted, the apparent conductivity of the measured underground medium has both amplitude and direction, that is, the apparent conductivity value in each direction is observed 360 degrees, and then the anisotropy of the underground medium is determined by analyzing the difference in conductivity in different directions, thereby tracing the direction of the linear underground medium to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] An omnidirectional apparent conductivity tracing exploration device, which inputs a high-power harmonic current through a transmitting coil and uses a receiving coil to receive a secondary magnetic field signal generated by the stimulation of an underground medium; it includes a field device for exploration, a data acquisition system, a data collation and diagram system, and a data analysis and interpretation system. The omnidirectional apparent conductivity data of dense measuring points can be obtained through the set field device and data acquisition system, and the plane position of the target body can be determined through the set data collation and diagram system; the set data analysis and interpretation system is used to adjust the frequency of the transmitting signal, and then analyze the characteristics of the receiving signal at different frequencies, so as to qualitatively evaluate the buried depth of the target body;

[0010] The field device includes a transmitter, a receiver and a power supply system arranged inside the host; the field device designs the transmitting coil T and the receiving coil R into a rectangular shape with the centers of the two on the same plumb line and the length-to-width ratio being greater than 2, so that the excitation magnetic field and the received secondary magnetic field are directional; the size of the coil varies with different detection depths;

[0011] The collection steps of the data acquisition system are as follows:

[0012] S1: Place the transmitting coil T and receiving coil R in the field device horizontally just above the measuring point, with the long sides of the two coils facing north. After ensuring that the equipment is connected normally, the transmitter inside the host inputs a harmonic current with a frequency of F1 and a corresponding period of T1 into the transmitting coil T to start transmitting electromagnetic signals. At the same time, the receiver inside the host starts to receive signals in time series mode and store them in real time. The data sampling frequency is greater than 10×F1, and the observation time is kept above 10×T1.

[0013] S2: With the center of the transmitting coil T and the receiving coil R as the axis, rotate the transmitting coil T and the receiving coil R clockwise by an angle n°, repeat the S1 observation action until one rotation is completed to achieve all-round data collection. In order to achieve the depth measurement goal, a multi-frequency data collection mode is required, that is, after completing data collection at frequency F1, change the transmitting frequency to F2, and repeat the above observation action until all the required frequencies Fn are completed;

[0014] The specific method of data sorting diagram system is as follows:

[0015] S1: Data preprocessing: Remove the primary magnetic field residual value ΔH1(t) from the time series observation data, and then denoise the removed data to form the secondary magnetic field time series data H2(t); if it is continuous sampling, then divide H2(t) into time segments to form H2 corresponding to different directions. n (t);

[0016] S2: Data conversion: to H2 n (t) are transformed into spectrum data corresponding to the transmitting frequency by Fourier transform, wherein the spectrum value is positively correlated with the comprehensive conductivity of the underground medium, and can be directly compared with the apparent conductivity for graphical analysis, or converted into the apparent conductivity by adopting the chart conversion mode for graphical analysis; using the same parameters and transmitting current values ​​as those of the transmitting coil T and the receiving coil R, the secondary magnetic field spectra corresponding to different frequencies and different conductivities are forward calculated with a one-dimensional uniform earth model, and a spectrum table of the secondary magnetic field H2(t) and its difference ΔH2(t) corresponding to each transmitting frequency and each typical conductivity can be formed, and the observed and calculated spectrum values ​​can be converted into apparent conductivity values ​​by looking up the table.

[0017] Furthermore, the receiving coil R is designed into two wire frames with exactly the same specifications, which are symmetrically placed on the upper and lower sides of the transmitting wire frame. The centers of the three wire frames are on a plumb line, and the long sides are parallel to each other. The two receiving coils R are connected in series in reverse order to offset the primary field H1.

[0018] Furthermore, the receiving coil R is placed at the center of the transmitting coil T, and the compensating coil B is laid outside it. The receiving coil R, the transmitting coil T and the compensating coil B are in the same plane, with the centers coinciding and the long sides parallel to each other. A current of the same frequency in the opposite direction to that in the transmitting coil T is input into the compensating coil B to offset the primary magnetic field signal received by the receiving coil R. The observed signal is the vertical component signal of the secondary magnetic field at the center of the receiving coil R.

[0019] Furthermore, after the data analysis and interpretation system processes the data according to the data collation and diagram system, it can form an apparent conductivity rose diagram for each measuring point. When the underground medium is uniform and has no detailed directional changes, the measured apparent conductivity rose diagram is approximately circular; when there is a pipeline cave underground with a detailed directional medium, if the medium is filled with water or the medium itself has strong conductivity, the measured apparent conductivity rose diagram is approximately elliptical, and the direction of the major axis of the ellipse indicates the direction of the pipeline cave; if the directional medium is a high-resistance body, the measured apparent conductivity rose diagram is approximately dumbbell-shaped, and the waist of the dumbbell indicates the direction of the pipeline cave. For the convenience of marking, an apparent resistivity rose diagram can be drawn, and its figure is presented as an ellipse, and the direction of the major axis of the ellipse indicates the direction of the pipeline cave. The apparent conductivity rose diagrams of all measuring points can be drawn on a plane map to facilitate the determination of the target body.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The omnidirectional apparent conductivity tracing exploration device provided by the present invention is more targeted than the traditional artificial field source frequency domain electromagnetic dipole profiling method. The original method has a wide range of applicable scenarios, but it is not ideal for finding shallow PE pipelines or caves, especially in towns and streets with serious noise interference. It is difficult to implement; the present invention is mainly aimed at the engineering exploration problems such as the exploration of PE pipelines, because of its strong anti-interference ability, large transmission power, and emission peak magnetic moment of nearly 1,000 Am 2 , small footprint, weak volume effect, can more quickly identify whether there are targets such as PE pipes underground, and effectively solve difficult detection problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the basic principle diagram of the existing artificial field source frequency domain electromagnetic dipole profile method;

[0023] Figure 2 It is a schematic diagram of the layout of the first field device scheme of the present invention;

[0024] Figure 3 It is a schematic diagram of the layout of the second field device scheme of the present invention;

[0025] Figure 4 is the apparent conductivity rose diagram of the present invention;

[0026] Figure 5 It is a comprehensive plan view of the apparent conductivity rose diagram of the present invention;

[0027] Figure 6 This is an example diagram of the omnidirectional conductivity tracing survey of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] An omnidirectional apparent conductivity tracing exploration device is provided in an embodiment of the present invention. The device inputs a high-power harmonic current through a transmitting coil, and uses a receiving coil to receive a secondary magnetic field signal generated by the stimulation of an underground medium. The device also includes a field device for exploration, a data acquisition system, a data collation and diagram system, and a data analysis and interpretation system. The omnidirectional apparent conductivity data of dense measuring points can be obtained through the provided field device and data acquisition system, and the planar position of a target body can be determined through the provided data collation and diagram system. The provided data analysis and interpretation system is used to adjust the frequency of the transmitting signal, and then analyze the characteristics of the receiving signal at different frequencies, so as to qualitatively evaluate the buried depth of the target body.

[0030] See also Figure 2-3 The field device in the embodiment of the present invention includes a transmitter, a receiver and a power supply system arranged inside the host; the field device designs the transmitting coil T and the receiving coil R into a rectangle and the centers of the two are on the same plumb line, and the aspect ratio is greater than 2 (it can also be designed as an ellipse, and its major axis or minor axis ratio is greater than 2), so that the excitation magnetic field and the received secondary magnetic field are directional (long side or major axis direction), so the excitation magnetic field and the received secondary magnetic field are also directional; the size of the above coils can be designed into multiple styles to be suitable for different detection depths. The greater the target detection depth, the larger the coil size needs to be; the present invention is mainly aimed at difficult exploration problems such as PE pipelines shallower than 10 meters, so the size of the transmitting coil is temporarily designed to be 3 meters × 1 meter, and the size of the receiving coil is designed to be 1.5 meters × 0.5 meters, and the number of turns are 5 turns and 200 turns respectively.

[0031] Based on the above description, the field device type is initially designed into two schemes (other schemes are not described here):

[0032] Option 1: If Figure 2 As shown, the receiving coil R is designed to be two wire frames with exactly the same specifications, which are symmetrically placed on the upper and lower sides of the transmitting wire frame (T and R are both placed horizontally). The centers of the three wire frames are on a plumb line, and the long sides are parallel to each other. The two receiving coils R are connected in series in reverse order to offset the influence of the primary field H1 (because the specifications of R1 and R2 cannot be exactly the same, and the distances between the two and the transmitting wire frame cannot be absolutely equal, the actual manufacturing equipment must have a residual value of the primary field vertical component. This residual value can be calibrated and tested at a standard site after the equipment is prepared, and is recorded as a calibration file ΔH1 (t), which is a time series data file so that the residual value can be removed during data sorting. The duration of t is the period corresponding to the frequency of the transmitting signal). The observed signal is the difference (ΔH2 (t)) between the vertical component signals of the secondary magnetic field at the centers of R1 and R2.

[0033] Option 2: If Figure 3As shown, the receiving coil R is placed at the center of the transmitting coil T, and the compensation coil B is laid outside it. The receiving coil R, the transmitting coil T and the compensation coil B are in the same plane, with the centers overlapping and the long sides parallel to each other; a current of the same frequency in the opposite direction to that in the transmitting coil T is input into the compensation coil B to offset the primary magnetic field signal received by the receiving coil R (when actually preparing the equipment, the specifications of B need to be adjusted in advance to try to make the primary field residual value in R not greater than 10 times the expected secondary magnetic field value to be detected, and the calibration after equipment preparation is the same as above), and the observed signal is the vertical component signal of the secondary magnetic field at the center of the receiving coil R.

[0034] Based on the descriptions of the above two solutions, when making the entire field device, it is necessary to use non-magnetic, non-conductive, and highly rigid materials to make the frame, and place the T and R coils in appropriate positions (hereinafter referred to as the "TR probe system") to ensure that T and R do not deform and their relative positions do not change.

[0035] In actual work, both schemes need to consider the problem of residual value of primary magnetic field, that is, after the equipment is prepared, it needs to be calibrated in a standard site (a site with small and stable external electromagnetic noise), and the primary field residual value ΔH1 (t) is tested and a calibration file is generated. This file is a time series of ΔH1 data. The data density should be higher than 10 times the corresponding transmission frequency. The sequence length is one transmission cycle. In actual work, the residual value needs to be removed from the measured data in a synchronous manner.

[0036] In the embodiment of the present invention, the data acquisition system has the following steps:

[0037] Step 1: Place the transmitting coil T and receiving coil R in the field device horizontally just above the measuring point, with the longer sides of the two coils facing north. After ensuring that the equipment is connected normally, the transmitter inside the host inputs a harmonic current with a frequency of F1 and a corresponding period of T1 into the transmitting coil T to start transmitting electromagnetic signals. At the same time, the receiver inside the host (transmission and reception are synchronized) starts to receive signals in a time series mode and store them in real time. The data sampling frequency is greater than 10×F1 (easy to achieve with current analog-to-digital converters). To ensure data quality, the observation time can be kept above 10×T1 to achieve multiple superpositions.

[0038] Step 2: With the center of the transmitting coil T and the receiving coil R as the axis, rotate the transmitting coil T and the receiving coil R clockwise by an angle (n°, it is recommended not to exceed 10°), and repeat the observation action in step 1 until one rotation is completed to achieve all-round data collection. In order to achieve the depth measurement goal, it is necessary to adopt a multi-frequency data collection mode, that is, after completing data collection at frequency F1, change the transmitting frequency to F2, and repeat the above observation action until all required frequencies Fn are completed.

[0039] In the above embodiment, in order to facilitate field work and improve field work efficiency, the following three measures can be taken:

[0040] (1): When making the equipment, an automatic rotating device is installed. Two modes can be adopted: hanging or rotating platform. Regardless of which mode is adopted, the "TR probe system" should not be too high from the ground (should not exceed 10cm).

[0041] (2): Since the present invention is mainly aimed at shallow exploration, the transmission frequency does not need to be too low (above 100 Hz), so the time corresponding to one transmission cycle is relatively short. Therefore, continuous observation can be achieved when the "TR probe system" rotates at a constant speed (the rotation speed should not be faster than 2 revolutions per minute), that is, while the "TR probe system" rotates at a constant speed, the transmission and reception work uninterruptedly to achieve continuous data collection.

[0042] (3): The exploration target depth of the present invention is less than ten meters, and the depth range is limited, so there is no need for too many transmission frequencies. Considering factors such as equipment cost, the transmission frequency is designed to be 128Hz, 512Hz, 2048Hz, 8192Hz and other frequencies. At present, the above frequency signals can be transmitted simultaneously, that is, the time series data of the secondary field signal is received and stored after multi-frequency transmission; when the equipment adopts the multi-frequency simultaneous transmission mode, the duration t of its verification file ΔH1 (t) should not be shorter than the period corresponding to the lowest frequency, and the verification sample density should be higher than 10 times the highest transmission frequency.

[0043] Through the above three measures, the field efficiency can be greatly improved. The observation time of each measuring point can be shortened to tens of seconds, and the collected data can be organized into omnidirectional apparent conductivity values ​​of the four frequencies of the measuring point, which greatly increases the amount of information.

[0044] In the embodiment of the present invention, the data arrangement and diagramming system is mainly divided into two parts, one is data preprocessing, and the other is data conversion. The specific method is as follows:

[0045] Step 1: Data preprocessing: Remove the primary magnetic field residual ΔH1(t) from the time series observation data (transmission and reception are synchronized, periodically removed according to the verification file, and synchronously removed according to the time series in each period), and then denoise the removed data to form the secondary magnetic field time series data H2(t); if it is continuous sampling, then divide H2(t) into time segments to form H2 corresponding to different directions. n (t);

[0046] Step 2: Data conversion: H2 n(t) are transformed into the spectrum data corresponding to the transmitting frequency (when 4 frequencies are transmitted at the same time, 4 spectrum data corresponding to the transmitting frequency can be extracted), wherein the spectrum value is positively correlated with the comprehensive conductivity of the underground medium, and can be directly compared with the apparent conductivity for graphical analysis, or converted into the apparent conductivity by adopting the chart conversion mode for graphical analysis; using the same parameters and transmitting current values ​​as those of the transmitting coil T and the receiving coil R, the secondary magnetic field spectra corresponding to different frequencies and different conductivities are forward calculated with the one-dimensional uniform earth model, and a spectrum table of the secondary magnetic field H2 (t) and its difference ΔH2 (t) corresponding to each transmitting frequency and each typical conductivity can be formed, and the observed and calculated spectrum values ​​can be converted into apparent conductivity values ​​by looking up the table.

[0047] In the above embodiment, the graphical representation is an apparent conductivity rose diagram, such as Figure 4 As shown, in the plane diagram, the measuring point is taken as the center, the observation azimuth corresponds to the azimuth in the diagram, the calculated apparent conductivity (or spectrum) value of the azimuth is taken as the radial fixed point (the distance from the point to the center point is equivalent to the apparent conductivity value or spectrum value of the azimuth), and all points are connected in sequence to form a closed trajectory diagram; except for the apparent conductivity rose diagram, the present invention can still use the original graphical representation mode of the artificial field source frequency domain electromagnetic dipole profile method, including profile curve diagram, plane section diagram, plane contour diagram, etc.; the specific azimuth apparent conductivity, minimum apparent conductivity, maximum apparent conductivity, comprehensive apparent conductivity, etc. of each measuring point can be used to draw a plane contour diagram, and the position of the target object can also be clearly displayed. Because it is the same as the traditional graphical representation method, it will not be repeated here.

[0048] In the embodiment of the present invention, the data analysis and interpretation system can form an apparent conductivity rose diagram of each measuring point after processing according to the data arrangement and diagram system, such as Figure 4 As shown, when the underground medium is uniform and has no obvious directional changes, the measured apparent conductivity rose diagram is approximately circular ( Figure 4 A, affected by noise and local unevenness, the measured graph jumps slightly along the circumference); when there is a pipeline cave underground with a clear directional medium, if the medium is filled with water or the medium itself is highly conductive, the measured apparent conductivity rose diagram is approximately elliptical ( Figure 4 B), the direction of the major axis of the ellipse indicates the direction of the pipeline cave; if the directional medium is a high-resistance body, the measured apparent conductivity rose diagram is approximately dumbbell-shaped ( Figure 4 C), the waist of the dumbbell indicates the direction of the pipeline cave, and the apparent resistivity (the inverse of the apparent conductivity) rose diagram can be drawn for easy marking. The figure is elliptical, and the direction of the major axis of the ellipse indicates the direction of the pipeline cave. The apparent conductivity rose diagram of all measuring points can also be drawn on a plane map. When there is a pipeline or cave with good conductivity underground, it will be displayed as follows Figure 5 When there are pipes or caves with poor conductivity underground, the target A will behave like Figure 5 Medium B target body.

[0049] In order to further better explain the present invention, the following specific examples are also provided:

[0050] Taking the PE water supply trunk pipeline without tracer line as an example, assuming that the pipeline passes through a certain block, runs in a north-east direction, and is buried no more than ten meters deep, then Figure 6 The following steps are shown to carry out trace exploration work:

[0051] Step 1: Measure a northwest-oriented survey line (L0 line) in the middle of the target block, with a measurement point spacing of 4 meters, and conduct omnidirectional apparent conductivity measurement point by point; through this survey line, the position of the PE pipeline on the L0 line can be roughly determined ( Figure 6 Point 36 of the L0 line) and trace its direction;

[0052] Step 2: Increase the number of measurement points near point 36 on line L0 to accurately determine the plane position and direction of the target pipeline ( Figure 6 Point 35 on the middle L0 line, running nearly east-west);

[0053] Step 3: From point 35 of L0 line, trace successively to the east and west sides in the form of short sections. According to the orientation shown in the rose diagram of point 35, the orientation of the subsequent construction section is changed to a near north-south direction, that is, observe L01W, L02W, and L03W in turn to the west. Because there is no target object on the L03W line, it is necessary to add the survey line L03WA. After the pipeline is turned by the supplementary survey line, the orientation and position of the short section are re-determined, and then the L04W, L05W and other survey lines are continued to be measured; observe L01E, L02E and other survey lines in turn to the east (extend outward and so on); the plane position of the target pipeline can be determined in this way;

[0054] Step 4: Select several typical apparent conductivity rose diagrams measured above the pipeline and analyze the anisotropy of the apparent conductivity at four frequencies. A one-dimensional uniform earth plus high-resistance pipeline model can be used for forward fitting to invert the pipeline depth, or the pipeline depth can be estimated by the detection depth sensitive to the frequency with the largest anisotropy.

[0055] In summary, the present invention provides an omnidirectional apparent conductivity tracing exploration device, which follows the basic principle of the artificial field source frequency domain electromagnetic dipole profiling method, inputs a high-power harmonic current into the transmitting coil and uses the receiving coil to receive the secondary magnetic field signal generated by the stimulation of the underground medium, but has made innovations in four aspects: field device, data acquisition mode, data collation and diagram mode, and data analysis and interpretation, which is essentially different from the traditional method; through the field data acquisition of the present invention, the omnidirectional apparent conductivity data of dense measuring points can be obtained, because the omnidirectional apparent conductivity of the measuring points above the target body (PE pipe, cave, etc.) has obvious anisotropy (the apparent conductivity along the direction of the target body is higher or lower), so the plane position of the target body can be judged; by adjusting the frequency of the transmitting signal, the characteristics of the receiving signal (omnidirectional apparent conductivity) at different frequencies are analyzed, because the signal frequency is related to the detection depth, the lower the frequency, the greater the detection depth, and thus the burial depth of the target body can be qualitatively evaluated.

[0056] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An omnidirectional apparent conductivity tracing exploration device, which inputs a high-power harmonic current through a transmitting coil and uses a receiving coil to receive a secondary magnetic field signal generated by the stimulation of the underground medium; characterized in that: include: Field equipment, data acquisition systems, data compilation and graphic systems, and data analysis and interpretation systems for exploration; The field device and data acquisition system are used to obtain all-round apparent conductivity data of dense measuring points; the planar position of the target body is determined by the data collation and diagram system; the data analysis and interpretation system is used to adjust the frequency of the transmitted signal, and then analyze the characteristics of the received signal at different frequencies to qualitatively evaluate the buried depth of the target body; The field device includes a transmitter, a receiver and a power supply system arranged inside the host; the field device designs the transmitting coil T and the receiving coil R into a rectangular shape, and the centers of the two are on the same plumb line, and the length-to-width ratio is greater than 2, so that the excitation magnetic field and the received secondary magnetic field are directional; the size of the coil varies with different detection depths; The collection steps of the data acquisition system are as follows: S1: Place the transmitting coil T and receiving coil R in the field device horizontally just above the measuring point, with the longer sides of the two coils facing north. After ensuring that the equipment is connected normally, the transmitter inside the host inputs a harmonic current with a frequency of F1 and a corresponding period of T1 into the transmitting coil T; start transmitting electromagnetic signals, and at the same time, the receiver inside the host starts receiving signals in a time series mode and storing them in real time; the data sampling frequency is greater than 10×F1, and the observation time is kept above 10×T1; S2: With the center of the transmitting coil T and the receiving coil R as the axis, rotate the transmitting coil T and the receiving coil R clockwise by an angle n°, repeat the S1 observation action until one circle is completed to achieve all-round data collection; in order to achieve the depth measurement goal, it is necessary to adopt a multi-frequency data collection mode, that is, after completing the data collection at the frequency F1, change the transmitting frequency to F2, and repeat the above observation action until all the required frequencies Fn are completed; The specific method of data sorting diagram system is as follows: S1: Data preprocessing: Remove the primary magnetic field residual value ΔH1(t) from the time series observation data, and then denoise the removed data to form the secondary magnetic field time series data H2(t); if it is continuous sampling, then divide H2(t) into time segments to form H2 corresponding to different directions. n (t); S2: Data conversion: to H2 n (t) are transformed into spectrum data corresponding to the transmitting frequency by Fourier transform, wherein the spectrum value is positively correlated with the comprehensive conductivity of the underground medium and can be directly compared with the apparent conductivity for graphical analysis, or converted into apparent conductivity by adopting the chart conversion mode for graphical analysis; the parameters and transmitting current values ​​with the same specifications as the transmitting coil T and the receiving coil R are used to forward calculate the secondary magnetic field spectrum corresponding to different frequencies and different conductivities with a one-dimensional uniform earth model, forming a spectrum table of the secondary magnetic field H2(t) and its difference ΔH2(t) corresponding to each transmitting frequency and each typical conductivity, and the observed and calculated spectrum values ​​are converted into apparent conductivity values ​​by looking up the table.

2. An omnidirectional conductivity tracing exploration device as claimed in claim 1, characterized in that: The receiving coil R is designed to be two wire frames with exactly the same specifications, which are symmetrically placed on the upper and lower sides of the transmitting wire frame. The centers of the three wire frames are on a plumb line, and the long sides are parallel to each other. The two receiving coils R are connected in series in reverse order to offset the primary field H1.

3. An omnidirectional conductivity tracing exploration device as claimed in claim 2, characterized in that: The receiving coil R is placed at the center of the transmitting coil T, and the compensating coil B is laid outside it. The receiving coil R, the transmitting coil T and the compensating coil B are in the same plane, with the centers coinciding and the long sides parallel to each other. A current of the same frequency in the opposite direction to that in the transmitting coil T is input into the compensating coil B to offset the primary magnetic field signal received by the receiving coil R. The observed signal is the vertical component signal of the secondary magnetic field at the center of the receiving coil R.

4. The omnidirectional conductivity tracing exploration device according to claim 1, characterized in that: After the data analysis and interpretation system processes the data according to the data collation and diagram system, an apparent conductivity rose diagram of each measuring point is formed; when the underground medium is uniform and has no detailed directional changes, the measured apparent conductivity rose diagram is approximately circular; when there is a pipeline cave underground with a detailed directional medium, if the medium is filled with water or the medium itself has strong conductivity, the measured apparent conductivity rose diagram is approximately elliptical, and the direction of the major axis of the ellipse indicates the direction of the pipeline cave; if the directional medium is a high-resistance body, the measured apparent conductivity rose diagram is approximately dumbbell-shaped, and the waist of the dumbbell indicates the direction of the pipeline cave. In order to facilitate the marking of the apparent resistivity rose diagram, its figure is presented as an ellipse, and the direction of the major axis of the ellipse indicates the direction of the pipeline cave. The apparent conductivity rose diagrams of all measuring points are drawn on a plane map to facilitate the determination of the target body.

Images