Randomly distributed tensor resistivity measurement method and system

Abstract

To solve the problem that conventional tensor resistivity measurement methods are often limited in their application by site terrain conditions and surface environments because the laying of the electrodes requires a regular arrangement.SOLUTION: Provided are a randomly distributed tensor resistivity measurement method and system. In the method, electrode deployment can be randomly arranged based on site-specific grounding conditions. The current supply station sequentially energizes two orthogonal current injection channels, while all potential measurement stations simultaneously and in parallel acquire potential differences across two potential measurement channels. The current and potential difference data are recorded with GPS timestamps, enabling synchronization of current supply and potential measurement station data based on corresponding time. Using the recorded data, current density vectors and electric field intensity vectors are calculated for each supply-measurement station combination, from which the corresponding apparent resistivity tensor is derived. With this configuration, geological exploration corresponding to various depths and complex surface conditions is realized.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention belongs to the field of non-destructive detection and transmission imaging, and particularly relates to a method and system for measuring randomly distributed tensor resistivity. [Background technology]

[0002] The traditional DC resistivity method and its derivative high-density electrical method are all resistivity measurement methods based on the quadrupole probe method, which are widely used in medicine, industrial process detection and monitoring, and geophysics. The quadrupole probe method uses four electrodes for measurement, two of which are power electrodes (A and B) and two of which are potential measurement electrodes (M and N). The instrument system simultaneously measures the power current of the power electrodes and the potential difference generated between the potential measurement electrodes, and combines this with the spatial positions of the four electrodes to calculate the true resistivity of the underground medium and the apparent resistivity value related to the spatial position relationship of the four electrodes. Furthermore, by inverse fitting, the resistivity distribution inside the detection object can be obtained, which further helps to determine the internal structure and physical properties of the target object.

[0003] The DC resistivity method is a detection technique that realizes penetration imaging of the interior of a target by measuring the potential distribution information in a stable current field. The apparent resistivity value obtained by the measurement is not only related to the actual resistivity (including anisotropy) and its spatial distribution of the underground medium, but also closely related to geometric characteristics such as the position, pitch, and direction of the measurement point. For example, the electrode pitch between the feed and potential measurement electrodes, the distance between the feed and potential measurement electrodes, and the installation direction of the feed and potential measurement electrodes all directly affect the apparent resistivity. The reliability of the apparent resistivity measurement is not only related to the distance between the feed and potential measurement electrodes (increasing the feed current improves the signal-to-noise ratio), but is also very sensitive to the direction, resulting in directional dependence and variability of the apparent resistivity value obtained by the measurement.

[0004] 1. When the position of the power supply electrode pair is fixed and the direction of rotation of the measurement electrode pair is variable, if the measurement electrode pair MN is laid along the direction of the equipotential surface gradient, the potential difference value between the MNs will be maximum, and if the MNs are laid parallel to the equipotential surface direction, the potential difference value will be close to zero.

[0005] 2. When the position of the measurement electrode pair is fixed and the direction rotation of the power electrode pair is variable, the apparent resistivity value also changes between a minimum and a maximum value.

[0006] Both of these situations explain the directional variability (non-uniqueness) of apparent resistivity obtained by conventional resistivity methods, making it difficult to establish a one-to-one correspondence with the true resistivity of the underground target, significantly affecting the accuracy of resistivity imaging. For 2D high-density electrical methods, the potential measurement electrode pair MN and the power electrode pair AB are aligned and always aligned in the gradient direction where the current-field potential difference is maximized, accurately reflecting the electric field potential distribution within the measurement cross section. Therefore, there is no need to consider the electrode orientation. On the other hand, for 3D resistivity surveys, the power electrode AB and the potential measurement electrode MN can be positioned in any position and orientation, and the apparent resistivity value changes regardless of the orientation of the power electrode pair or the potential measurement electrode pair, further significantly affecting the inversion results. Using this directional variable apparent resistivity value to invert and determine the true (unique) resistivity of the underground target is subject to relatively large uncertainties and incompleteness, making it difficult to fully accurately reflect the electric field characteristics and distribution of the underground medium.

[0007] In summary, the quadrupole probe method has the following inherent shortcomings:

[0008] 1. Uncertainties and imperfections in the scalar resistivity measurement method: The apparent resistivity value when measuring a single component changes with directional changes, and the direction of the maximum value is unknown. There are obvious blind spots and imperfections in the collection method and measurement point design. The obtained single-channel apparent resistivity value cannot fully describe the actual electric field characteristics of the earth's surface. These defects are more obvious when measuring in three dimensions.

[0009] 2. The blindness of the electrode position design makes the single component potential measurement susceptible to interference: The blindness of the electrode placement means that the potential measurement electrode point is placed along the equipotential surface, which may cause the potential difference to be close to 0. Especially when the K value of the device system is large, the potential difference obtained by the measurement will be very small, and the apparent resistivity value will be extremely susceptible to the influence of instrument stability and external electromagnetic interference, resulting in jumps or false values ​​in the apparent resistivity value.

[0010] The evolution from the quadrupole probe resistivity method to the high-density resistivity method has improved data density and imaging resolution through multichannel measurements, but it has not eliminated the above-mentioned drawbacks of the quadrupole probe method and has added some new deficiencies.

[0011] 1. The use of multi-core cables in the high-density resistivity method and their shared use of power supply and potential measurement channels is likely to cause coupling between the power supply and potential measurement signals, which will seriously interfere with the secondary electric field measurement in the excitation polarization method. Multi-core cables are also not suitable for large current supply, making it difficult to apply to deep exploration or long-term power supply excitation polarization measurements.

[0012] 2. Conventional high-density electrical measurements continue to suffer from the blindness and imperfections of quadrupole probes. The electrodes are arranged according to a regular grid and can only move along two orthogonal directions of the measurement line, making it a pseudo-three-dimensional measurement, not a true three-dimensional exploration. In urban or complex environmental conditions, it is difficult to find a suitable, regular rectangular area for regularly laying electrodes, which seriously limits the field application of high-density electrical measurements.

[0013] 3. Traditional high-density electrical measurement equipment uses long cables with all electrodes connected in series, and each measurement can only be performed by selecting four electrodes (power supply / measurement) according to the electrode's position on the cable, resulting in low collection efficiency. Heavy cables increase the labor intensity of the installation process, and the presence of obstacles (rivers, large buildings, traffic dry lines, etc.) often makes on-site cable installation difficult.

[0014] 4. Due to the number of electrodes, electrode distance and cable length, traditional 3D high-density electrical systems can only cover a limited area. To cover the entire 3D survey area, multiple rolling stitching is required. However, the rolling stitching process of traditional 3D high-density electrical methods is very complicated, making it even more difficult to implement when the ground conditions are complex.

[0015] 5. Conventional high-density electrical methods are limited by the electrode distance and total number of electrodes. They are generally used for shallow surface detection of 50 m or more, and cannot meet the demands of deep exploration of hundreds to thousands of meters (mineral exploration, geothermal exploration, etc.). 6. The measurement parameters of the conventional high-density electrical method are limited, and each electrode is responsible for both power supply and potential measurement, making it difficult to perform spontaneous potential measurement and excitation polarization measurement, which seriously limits the application of the high-density electrical method in the field of mineral exploration. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] China Patent Publication CN110376650A [Patent Document 2] China Patent Publication CN112433252A Summary of the Invention [Problem to be solved by the invention]

[0017] To address the shortcomings of the prior art, the present invention proposes a random distribution type tensor resistivity measurement method and measurement system, and the specific technical solutions are as follows: [Means for solving the problem]

[0018] A randomly distributed tensor resistivity measurement method, the method comprising: Step S1: Arranging a plurality of potential measurement sites P covering the entire measurement area in accordance with the ground surface conditions within the measurement area; Step S2: arrange four potential measurement electrode points M1, N1, M2, and N2 around each potential measurement site P, arrange one potential measurement station at each potential measurement site P, and the line connecting M1 and N1 intersects with the line connecting M2 and N2, the distance between M1 and N1 and the distance between M2 and N2 are the electrode distance a, a=(1 / 10~1 / 20)H, and H is the exploration depth; Step S3: Arranging a plurality of feeding points within the measurement area, arbitrarily selecting four feeding points A1, B1, A2, and B2, and satisfying that the line connecting A1 and B1 intersects with the line connecting A2 and B2; First, the power supply station supplies power to the electrodes at A1 and B1, and the electrodes at all potential measurement sites P simultaneously measure the potential. The power supply station measures the power supply current I1 of the electrodes at A1 and B1, and each potential measurement station measures the potential difference ΔU of the power supply at A1 and B1 corresponding to M1, N1 and M2, N2. M1N1 (1) and ΔU M2N2 (1) The power supply station supplies power to the electrodes at A2 and B2, and the electrodes at all potential measurement sites P simultaneously measure the potential. The power supply station measures the power supply current I2 of the electrodes at A2 and B2, and each potential measurement station measures the potential difference ΔU of the power supply at A2 and B2 corresponding to M1, N1 and M2, N2. M1N1 (2) and ΔU M2N2 (2) Step S4 of measuring Based on the power supply currents I1 and I2 and the positional relationship between A1, B1 and point P, a first current density vector generated by A1 and B1 at point P and a second current density vector generated by A2 and B2 at point P are obtained, and a potential difference ΔU M1N1 (1) and ΔU M2N2 (1) Based on the electrode distance, A1 and B1 obtain the first electric field intensity vector generated at point P, and ΔU M1N1 (2) and ΔU M2N2 (2) and step S5 of obtaining a second electric field intensity vector generated at point P by A2 and B2 based on the electrode distance; The method includes a step S6 of vector-resolving the first current density vector, the second current density vector, the first electric field intensity vector, and the second electric field intensity vector in the same coordinate system to calculate an apparent resistivity tensor.

[0019] Furthermore, this method further includes, before performing S1, first dividing the entire measurement area into a plurality of sub-measurement areas, and then performing S1 to S6 in each sub-measurement area, and completing the tensor resistivity measurement of the entire measurement area after completing the tensor resistivity measurement of each sub-measurement area.

[0020] Furthermore, this method includes, before executing S1, first dividing the entire measurement area into a plurality of sub-measurement areas, and then executing S1 to S2 in each sub-measurement area, and arranging a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 in each sub-measurement area; The placement and selection of the power supply points in step S3 are replaced as follows: k internal power supply points are placed within each sub-measurement area, and l external power supply points are placed on the periphery of each sub-measurement area; one of the k internal power supply points is selected and named as point O; two of the l external power supply points are arbitrarily selected and named as A1 and A2; that is, B1 and B2 overlap with point O; The method further includes performing S4 to S6 in each sub-measurement area, and completing the tensor resistivity measurement of the entire measurement area when the tensor resistivity measurement of each sub-measurement area is completed.

[0021] Furthermore, before executing S1, the entire measurement area is first divided into a plurality of sub-measurement areas, and S1 to S2 are executed in each sub-measurement area, and a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 are arranged in each sub-measurement area; The arrangement and selection of the power supply points in step S3 is replaced as follows: arrange four or more external power supply points on the periphery of each sub-measurement area, and arbitrarily select four of the external power supply points, which are named A1, B1, A2, and B2, and the line connecting A1 and B1 intersects with the line connecting A2 and B2; Then, steps S4 to S6 are executed in each sub-measurement area, and when the tensor resistivity measurement for each sub-measurement area is completed, the tensor resistivity measurement for the entire measurement area is completed.

[0022] Furthermore, the external power supply points arranged on the periphery of each sub-measurement area are distributed in each direction on the periphery of the sub-measurement area.

[0023] Furthermore, there are eight external power supply points arranged on the periphery of the sub-measurement area, distributed in eight directions around the periphery of the sub-measurement area: east, west, south, north, southwest, northwest, southeast, and northeast.

[0024] Furthermore, in step S2, the potential measurement electrode points N1 and N2 overlap with the potential measurement site P.

[0025] Furthermore, the power supply points B1 and B2 overlap at point O, and the power supply station is located at this point O.

[0026] Furthermore, the pitch between adjacent potential measurement sites is 2 to 3 times the electrode distance, and the distance between adjacent power supply points is 3 to 5 times the distance between adjacent potential measurement sites.

[0027] A randomly distributed tensor resistivity measurement system, the system including a plurality of power feed stations and a potential measurement station; The power supply station includes a power supply station host, a long-distance power supply cable, a power supply electrode, and a boost power supply; The power supply station host includes a first control module, a first power supply module, a first internal battery, a current measurement module, and a first GPS module, and the first control module is used to control the selection of power supply electrode channels throughout the power supply station, the setting of power supply parameters, the access of an external boost power supply, the internal power management, the power supply process current measurement, the GPS clock, and the registration of power supply current data measured in the power supply process, thereby forming time-series current data and storing it by segments at set time intervals; the current measurement module measures and digitizes the power supply current value using an A / D conversion circuit; the first power supply module is used to select a specific power supply channel and connect to the boost power supply through a power supply interface; the first internal battery is used to provide electrical energy necessary for the power station to operate for a long period of time; the first GPS module includes an external antenna that is controlled by the first control module, and continuously transmits GPS codes to the power supply station host after power-on and self-check is normal, and provides location and clock information; The power supply station host provides four power output ports, and connects the power supply electrodes located at the four power supply points A1, B1, A2, and B2 via the long-distance power supply cable, and sequentially supplies power underground; the potential measuring station includes a potential measuring station host, a potential measuring cable, and a potential measuring electrode; the potential measuring station host includes a second control module, a second power supply module, a second built-in battery, a potential measuring module, and a second GPS module; the second control module is used to control the selection of the potentiometric electrode channel, the setting of the potential measurement parameters, the internal power management, the measurement and storage of the dual-channel potential difference, the registration of the GPS clock and the potentiometric data, and to generate a time series of potential difference data and store it by segments at set time intervals; the potential measurement module is used to simultaneously collect potential difference data of two cross-positioned potential measurement channels; The second power module is used to monitor and manage the monitoring status and charging process of the built-in battery; the second built-in battery is used to provide electrical energy required for the long-term operation of the potential measuring station; the second GPS module includes an external antenna that is controlled by the second control module, and continuously transmits GPS codes to the second control module after powering on and self-checking, providing position and clock information of the measuring station; The potential measuring station host provides four potential measuring ports, which connect the potential measuring electrodes located at M1, N1, M2, and N2 via the potential measuring cables, respectively, and receive potential difference information between the potential measuring electrode points. [Effects of the Invention]

[0028] The beneficial effects of the present invention are as follows:

[0029] 1. The method of the present invention adopts a randomly distributed collection site design, allowing the power supply point and potential measurement point locations to be flexibly arranged according to the ground conditions, avoiding the limitations of on-site collection due to unfavorable ground conditions and increasing the flexibility of on-site construction. The obtained tensor resistivity can be used for inversion to achieve true three-dimensional and four-dimensional resistivity imaging of the measurement area.

[0030] 2. The method of the present invention can obtain complete information on the distribution of the earth's electric field by time-division multi-directional sequential power supply and simultaneous collection and acquisition of cross-directional potential difference data by a group. It adopts the mode of single excitation and multiple reception and multi-point sequential excitation, and realizes group automatic parallel measurement through GPS timing synchronization, thereby improving data collection efficiency.

[0031] 3. In the random distribution tensor resistivity measurement system of the present invention, the power supply station and the potential measurement station host are designed independently, each node works independently, the power supply and potential measurement cables are separated, coupling interference is avoided, and multiple parameters such as resistivity, excitation polarization and natural potential can be measured.

[0032] 4. The method and system of the present invention can flexibly adjust collection parameters according to exploration needs, and can be adapted to mid-to-shallow 3D resistivity exploration, and can also be applied to deep exploration needs (mineral exploration, geothermal exploration, etc.). [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a flowchart of the random distribution tensor resistivity measurement method of the present invention. [Figure 2] FIG. 1 is a schematic diagram of the relationship between the power supply and the potential measurement electrode points in tensor resistivity measurement. [Figure 3] FIG. 10 is a schematic diagram of another method for laying out power supply and potential measurement electrode points for tensor resistivity measurement. [Figure 4] FIG. 1 is a schematic diagram of the effect of the placement of measurement points in randomly distributed tensor resistivity measurements. [Figure 5] FIG. 10 is a schematic diagram of a rolling measurement of a tensor resistivity sub-measurement area. [Figure 6] FIG. 2 is a structural schematic diagram of a power supply station host. [Figure 7] FIG. 2 is a structural schematic diagram of the potential measuring station host. [Figure 8] FIG. 10 is a comparison of the results of conventional scalar resistivity imaging and the results of tensor resistivity imaging using numerical simulations. [Figure 9] FIG. 10 is a comparison of imaging results for different feed electrode lengths using the tensor resistivity method. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, the present invention will be described in detail based on the drawings and preferred embodiments, so that the object and effect of the present invention will become more apparent. It should be understood that the specific examples described herein are used only to interpret the present invention and are not intended to limit the present invention.

[0035] In practical electrical exploration, the derivative of conductivity - resistivity ρ - is often used to describe the electrical properties of a medium. At the surface interface, the vertical components of current density and electric field strength in Ohm's law are zero, and the resistivity tensor degenerates to a 2x2 matrix, which can be calculated by measuring the applied current and potential difference with instruments.

[0036] JPEG2025179835000002.jpg17154

[0037] JPEG2025179835000003.jpg54170

[0038] As shown in FIG. 1, the random distribution tensor resistivity measurement method of this embodiment includes two parts: one is the design and installation of measurement points, which specifically includes the following steps S1 to S3; the other is the data collection process and collection step, which specifically includes the following steps S4 to S6.

[0039] 1. Design and installation of measuring points The unique feature and advantage of the randomly distributed tensor resistivity method is that the power supply and potential measurement units are independent and separate (an individual is described as independently managing the collection process at each site, while a group is described as the collaborative work of multiple sites), and the measurement points can be positioned arbitrarily according to the ground conditions. Both the power supply and potential measurement use a four-electrode or three-electrode dual-channel node collection station design, allowing for flexible placement depending on the ground conditions. At the same time, the randomly distributed system does not require specific placement of electrode pairs, but it allows for uniform placement within a measurement area, which is advantageous for uniform detection of underground targets. First, the collection parameters are designed, and then parameters such as the potential measurement electrode distance, power supply electrode distance, and measurement point density are determined based on the exploration depth requirements. Then, the potential measurement points and power supply points are designed and arranged on the map. The specific measurement point design steps are as follows:

[0040] S1: Depending on the ground surface conditions, multiple potential measurement sites P covering the entire measurement area are arbitrarily arranged within the measurement area, and the pitch between adjacent potential measurement sites is 2 to 3 times the electrode distance.

[0041] S2: Four potential measurement electrode points M1, N1, M2, and N2 are arranged around each potential measurement site P, and one potential measurement station is arranged at each potential measurement site P. The four ports on this potential measurement station are respectively connected to the four potential measurement electrode points M1, N1, M2, and N2 via potential measurement cables. The electrode points M1, N1, M2, and N2 satisfy the following conditions: the line connecting M1 and N1 intersects the line connecting M2 and N2 (it does not need to be perpendicular, but should intersect at as large an angle as possible). The distance between M1 and N1 and the distance between M2 and N2 are called the electrode distance a (they do not need to be equal, and the specific length is determined by the position coordinates), where a = (1 / 10 to 1 / 20)H, and H is the exploration depth.

[0042] S3: Arrange multiple power supply points within the measurement area, with the distance between adjacent power supply points being 3 to 5 times the distance between adjacent potential measurement sites P. Four power supply points (the specific power supply method and power supply point selection method will be described in detail later) are arbitrarily selected within the measurement area and named A1, B1, A2, and B2. The four power supply points A1, B1, A2, and B2 must satisfy the requirement that the line connecting A1 and B1 intersects the line connecting A2 and B2. The electrodes at A1, B1, A2, and B2 are connected to the power supply station via long-distance power supply cables.

[0043] The relationship between the power supply and the potential measurement electrode points for tensor resistivity measurement is as shown in Figure 2.

[0044] To facilitate field installation and improve operational efficiency, the power supply points B1 and B2 may overlap, overlapping with point O, and the power supply station is located at this point O. For similar reasons, the potential measurement electrode points N1 and N2 overlap with the potential measurement site P. The installation method shown in Figure 3 is more advantageous for the layout and implementation of field work.

[0045] Here, in one embodiment, the effect of completing the installation of the power supply and potential measurement electrodes is to adopt a mixed arrangement, as shown in FIG.

[0046] To perform inverse imaging for larger exploration depths while actually measuring, the distance between the feed point and the potential measurement site increases with increasing exploration depth. At the same time, due to limitations on the number of feed and potential measurement collection station equipment, it is generally impossible to complete equipment coverage of a single measurement area at once. To achieve relatively uniform imaging in all directions across the measurement area, the entire measurement area can be divided into multiple sub-measurement areas before installing the feed points and potential measurement sites. The feed points and potential measurement sites can then be installed within each sub-measurement area. After completing the measurement process for one sub-measurement area, the next sub-measurement area is sequentially scrolled to and steps S1-S2 are executed. When the measurement process for the last sub-measurement area is completed, the data collection process for the entire measurement area is completed.

[0047] During actual construction, the measurement installation is also divided into paper design and on-site verification. After the final installation location of the measurement point is confirmed, surveying equipment such as GPS is used to collect the measurement point position coordinates and numbers of the electrode pairs, which are used to optimize the design of the subsequent collection plan and to set the equipment parameters during on-site construction.

[0048] In addition, there are various flexible methods for laying the power supply points and their power supply modes in Step 3.

[0049] 1. Power supply mode with approximately equidistant grid nodes The advantage of using a designed grid-like feed point to create a nearly orthogonal combination of feed points (B1-B2 and B1-B6 in Figure 5) is that it can be advanced sequentially in an orthogonal direction along the designed feed grid, and the length of the feed line is short, which is advantageous for installation. However, because the pitch between feed points is short, they are susceptible to electromagnetic interference during measurement. Therefore, during measurement, it is necessary to increase the feed voltage to increase the feed current or the feed dipole moment, i.e., to select one measurement point at multiple intervals to feed power.

[0050] 2. Ambient lighting imaging power supply mode Each sub-measurement area is equipped with one external power supply point. Four of these points are randomly selected and named A1, A2, B1, and B2 to form a power supply point combination (the power supply site is defined as point O, where the line connecting A1 and B1 intersects with the line connecting A2 and B2). As shown in Figure 5, the entire measurement area is first divided into four rectangular sub-measurement areas. The small red dots in Figure 5 represent power supply points. Taking measurement area 1 in the lower left as an example, eight peripheral long-distance power supply points and 25 potential measurement collection stations are designed in this area. The eight peripheral long-distance power supply points are AA1-AA3, AA5, AA7, and AA9-AA11, and are distributed in eight directions around the perimeter of measurement area 1: east, west, south, north, southwest, northwest, southeast, and northeast. For example, AA5 and AA7 can be selected as A1 and B1, and AA2 and AA10 as A2 and B2, or AA9 and AA2 can be selected as A1 and B1, and AA2 and AA11 can be selected as A2 and B2. For the selected power supply combination, all potential measurement stations (M1N1 and M2N2 are dual-channel) within the sub-measurement area perform parallel measurements simultaneously. This power supply mode has the smallest workload.

[0051] 3. Near and far combination power supply mode As shown in Figure 5, the entire measurement area is first divided into four rectangular sub-measurement areas. The small red dots in Figure 5 represent power supply points. Taking measurement area 1 in the lower left as an example, this area is designed with 36 internal power supply points, eight peripheral far-field power supply points, and 25 potential measurement collection stations. Power is supplied using a combination of the far-field measurement point of the ambient lighting imaging (measurement point AA in Figure 5) and the near-field measurement point of the sub-measurement area (measurement point BB in Figure 5). That is, k internal power supply points are placed within each sub-measurement area, and l external power supply points are placed around the periphery of each sub-measurement area. One of the k internal power supply points is selected and named point O, and two of the l external power supply points are arbitrarily selected and named A1 and A2. That is, B1 and B2 overlap with point O. Specifically, in Figure 5, the combinations are AA5 and BB34 and AA2 and BB34 in Figure 5. The AA feed points and BB common points have various feed combinations, allowing for "illumination" imaging of underground targets from multiple directions, resulting in higher measurement point density and resolution. For example, first select feeds (AA1:BB1) and (AA2:BB1), then move to feeds (AA1:BB2) and (AA2:BB2), and complete feeds (AA1:BB36) and (AA2:BB36). Then, according to the rules for array combination, select feeds (AA2:BB1) and (AA3:BB1), and repeat this cycle until all AA and BB feed points have been selected, completing the feed process. During the feed process, the two feed channels feed sequentially, and with each feed, all 25 potential measurement and collection stations simultaneously measure potential. After completing the measurement process for measurement area 1, all feed points and potential measurement and collection station configurations are moved to measurement area 2. The above feed and potential measurement process is then repeated. Then, the measurement processes of the 3-measurement area and the 4-measurement area are arranged sequentially until the measurement processes of all the measurement areas are completed.

[0052] The feed points are spread around the periphery of the sub-measurement area, which not only provides multi-directional "illumination" imaging, but also increases the feed electrode distance and increases the probing depth, ensuring coverage of a certain number of measurement points for near, medium, and far imaging depths.

[0053] Therefore, the design and installation of the measurement points in this embodiment may be as follows.

[0054] Before performing S1, the entire measurement area is first divided into multiple sub-measurement areas, and then a complete random distribution tensor resistivity measurement method is performed in each sub-measurement area. After completing the tensor resistivity measurement for each sub-measurement area, the tensor resistivity measurement for the entire measurement area is completed.

[0055] Alternatively, before executing S1, the entire measurement area is first divided into a plurality of sub-measurement areas, and S1 to S2 are executed in each sub-measurement area, and a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 are arranged in each sub-measurement area; The placement and selection of the power supply points in step S3 are replaced as follows: k internal power supply points are placed within each sub-measurement area, and l external power supply points are placed on the periphery of each sub-measurement area; one of the k internal power supply points is selected and named point O; two of the l external power supply points are arbitrarily selected and named A1 and A2; that is, B1 and B2 both overlap with point O.

[0056] Alternatively, before executing S1, the entire measurement area is first divided into a plurality of sub-measurement areas, and S1 to S2 are executed in each sub-measurement area, and a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 are arranged in each sub-measurement area; The placement and selection of the power supply points in step S3 is replaced as follows: four or more external power supply points are placed around the periphery of each sub-measurement area, and four of the external power supply points are arbitrarily selected and named A1, B1, A2, and B2, and the line connecting A1 and B1 intersects with the line connecting A2 and B2.

[0057] 2. Data collection process and collection steps The installation of the power feeder station and the rolling of the measurement station are separate and independent processes from the potential measurement collection station. They do not communicate with each other and operate continuously at set intervals until the measurement task is completed and the system shuts down. The power feeder is designed and located according to the power supply mode described above. The power feeder is then powered on, self-checked (including GPS signal), and operational parameters are set. After the equipment is operational, the A1B1 and A2B2 power feeder point coordinates obtained and recorded by GPS or other surveying tools are entered. After safety is confirmed, the power supply process is carried out, and the equipment system automatically records information such as the time and power supply current. After the measurement is completed, the system moves to the next power feeder station and repeats the above process.

[0058] The specific steps of the power supply measurement process are as follows:

[0059] S4: The power supply station first supplies power to the electrodes at the power supply points A1 and B1, and the electrodes at all potential measurement sites P simultaneously measure the potential. The power supply station measures the power supply current I1 of the electrodes at the power supply points A1 and B1, and each potential measurement station measures the potential difference ΔU of the power supply at A1 and B1 corresponding to the measurement electrode points M1, N1 and M2, N2. M1N1 (1) and ΔU M2N2 (1) Measure Furthermore, the power supply station supplies power to the electrodes at the power supply points A2 and B2, and the electrodes at all potential measurement sites P simultaneously measure the potential. The power supply station measures the power supply current I2 of the electrodes at the power supply points A2 and B2, and each potential measurement station measures the potential difference ΔU of the power supply at A2 and B2 corresponding to the potential measurement electrode points M1, N1 and M2, N2. M1N1 (2) and ΔU M2N2 (2) Measure.

[0060] S5: Based on the supply currents I1 and I2 and the positional relationship between A1, B1 and point P, a first current density vector generated by A1 and B1 at point P and a second current density vector generated by A2 and B2 at point P are obtained, and a potential difference ΔUM1N1 (1) and ΔU M2N2 (1) Based on the electrode distance, A1 and B1 obtain the first electric field intensity vector generated at point P, and ΔU M1N1 (2) and ΔU M2N2 (2) Based on the electrode distance, A2 and B2 obtain the second electric field intensity vector generated at point P.

[0061] S6: The first current density vector, the second current density vector, the first electric field intensity vector, and the second electric field intensity vector are vector-resolved in the same coordinate system to calculate the apparent resistivity tensor.

[0062] A specific formula for calculating the apparent resistivity tensor is as follows:

[0063] JPEG2025179835000004.jpg255163where (x A1 ,y A1 ), (x B1 ,y B1 ), (x A2 ,y A2 ), (x B2 ,y B2 ) are the coordinates of the four feeding points A1, B1, A2, and B2, respectively, and (x M1 ,y M1 ), (x N1 ,y N1 ), (x M2 ,y M2 ), (x N2 ,y N2 ) are the coordinates of the four potential difference measurement points, and (x P ,y P ) are the coordinates of the potential measurement site P, JPEG2025179835000005.jpg62170

[0064] The randomly distributed tensor resistivity measurement system of the present invention includes multiple power supply stations and potential measurement stations, each of which operates independently and provides unified timing using its own GPS clock, stores data records in clock order, and extracts current or potential difference data at the corresponding time of each station according to the clock registration during subsequent data processing.

[0065] In this embodiment, the power supply station is composed of a power supply station host, four long-distance power supply cables, four to ten stainless steel or copper electrodes, a booster power supply, and a generator or battery.

[0066] As shown in Figure 6, the power supply station host includes a first control module, a first power supply module, a first internal battery, a current measurement module, and a first GPS module. The first control module is the core of the entire power supply station and is responsible for selecting the power supply electrode channel within the entire power supply station system, setting power supply parameters, accessing the external power supply, managing the internal power supply, measuring the power supply process current, and registering the GPS clock with the power supply current data measured during the power supply process (time marker encoding). It then forms time-series current data and stores it in segments at set time intervals (binary data file). The file header contains information such as the power supply start and end times, the power supply station number, the power supply channel number, and the associated electrode position coordinates.

[0067] The current measurement module is controlled by the first control module, and measures and digitizes the power supply current value using an A / D conversion circuit, exports it to the control circuit, and records and stores it.

[0068] The first power supply module selects a specific channel (A1, B1 or A2, B2) under the control of the first control module, and connects it to an external boost power supply through the power supply interface to provide an external power supply input. The first power supply module is also responsible for monitoring the built-in battery status and monitoring and managing the charging process.

[0069] The first built-in battery provides the electrical energy required for the power station to operate for a long time, and also provides the minimum electrical energy consumption required for the system clock, memory information and some chip operations during the system shutdown or standby process.

[0070] The first GPS module is controlled by the first control module and includes an external antenna and a GPS control module that continuously transmits GPS codes to the host after powering on and self-checking successfully, providing position and clock information. The host records and stores the clock information together with the power supply current measurement data, providing a "timestamp" for subsequent data processing.

[0071] The power supply station host is designed with multiple interfaces according to functional needs. 1. Four power output ports are used to connect distant power supply electrodes A1, B1, A2, and B2 via long-distance power supply cables, and subsequently supply power underground. 2. The power input interface is connected to a boost power supply and is used to input high-power, high-voltage DC power. 3. The charging interface is used to charge the built-in power supply. 4. The communication interface is used to export power supply current data (time series) recorded during fieldwork that is stored in the device during office work. The communication interface is equipped with an external wireless communication module, which can be upgraded to realize remote data transmission and remote telemetry control.

[0072] The boost power supply is a high-power DC power output device with inverter boost function, and its power setting and device design depend on the exploration depth requirements. The boost power supply is connected to a battery or battery pack and can be boosted by a DC-DC inverter, or it can be boosted by a generator to 220V AC and rectified to output DC power.

[0073] The choice between generators, batteries, and battery packs is based on the exploration depth (power supply) and the difficulty of surface travel. Batteries and battery packs are more convenient to transport, but have limited power supply and operating time. Generators have a wider range of power supply times and options, but are relatively large in volume and weight, making them difficult to transport in complex terrain conditions. The choice can be made flexibly according to the surface conditions and exploration target requirements.

[0074] As shown in FIG. 7, the potential measuring station includes a potential measuring station host, two to four potential measuring cables, three to four non-polarized electrodes, and the like.

[0075] The potential measuring station host includes a second control module, a second power supply module, a second internal battery, a potential measuring module, and a second GPS module. The second control module is the core of the entire potential measuring station system and is responsible for selecting the potential difference measurement electrode channel within the entire potential measuring station system, setting the potential measurement parameters, managing the internal power supply, measuring and storing the dual-channel potential difference, and registering the GPS clock and potential difference measurement data (time marker encoding). It then forms time-series potential difference data and stores it in segments at set time intervals (binary data file). The file header contains information such as the start and end times of the potential difference measurement, the potential measuring station number, the potential difference measurement channel number, and the associated electrode position coordinates.

[0076] The potential measurement module is controlled by the second control module and is used to simultaneously collect potential difference data of two cross-positioned potential measurement channels, which are recorded and stored by the control circuit.

[0077] The second power supply module is used to monitor the internal battery status and monitor and manage the charging process under the control of the second control module.

[0078] The second built-in battery is used to provide the electrical energy required when the potential measuring station operates for a long period of time, and further contains the minimum electrical energy consumption required for the system clock, memory information and some chip operations during the system shutdown or standby process.

[0079] The second GPS module includes an external antenna and a GPS module that is controlled by the second control module and continuously transmits GPS codes to the control module after powering on and performing a self-check, providing the measurement station's position and clock information. The second control module records and stores the clock information together with the current measurement data, providing a "timestamp" for subsequent data processing.

[0080] The potential measurement station host is designed with multiple interfaces according to functional needs. 1. The four potential measurement ports are used to connect remote potential measurement electrodes M1, N1, M2, and N2 via potential measurement cables to receive potential difference information between measurement points. 2. The charging interface is used to charge the built-in power supply. 3. The communication interface is used to export potential difference data (time series) recorded during fieldwork that is stored in the device during office work. The communication interface is equipped with an external wireless communication module, which can be upgraded to enable remote data transmission and remote telemetry control.

[0081] To perform inverted imaging of the underground of the measurement area, after obtaining data from all power supply stations and potential measurement stations, the processing software needs to extract the potential measurement data of the four channels of each potential measurement station, align the corresponding power supply current data extracted from the power supply stations with timestamps, combine the measurement station number and location coordinates, calculate the apparent resistivity tensor combining each power supply station and potential measurement station, and then perform inverted imaging directly, or extract the rotational invariant of the apparent resistivity tensor to perform inverted imaging.

[0082] There are generally two methods for extracting rotation invariants:

[0083] 1. Based on a combination of three independent rotation invariants There are three independent invariants (Determinant, Root Mean Square (RMS), and Trace of the matrix) associated with the apparent resistivity tensor matrix elements, which allow the three rotational invariants to be extended and combined into an infinite set of invariants to characterize and evaluate the electrical parameters of subsurface structures.

[0084] JPEG2025179835000006.jpg25170

[0085] JPEG2025179835000007.jpg28170

[0086] JPEG2025179835000008.jpg28170

[0087] 2.WAL rotation invariant The formula for the tensor resistivity is appropriately decomposed into a combination of rotational invariants and variable quantities, JPEG2025179835000009.jpg117170

[0088] JPEG2025179835000010.jpg27170

[0089] JPEG2025179835000011.jpg29170

[0090] JPEG2025179835000012.jpg27170

[0091] These rotationally invariant combined parameters are typically used to invert and plot various plots, remove the directional effects of conventional resistivity measurements, improve plot quality, provide cross-comparison validation of multiple parameter plots, and further improve interpretation accuracy.

[0092] To verify the beneficial effects of the method of the present invention, numerical simulation imaging was carried out using the conventional resistivity method and the tensor resistivity method of the present application, respectively. The results are shown in Figure 8. Figure 8 (e) shows a rectangular underground wall structure model installed, with 13 x 13 electrode points arranged at equal intervals along the X and Y directions around it. The conventional resistivity method selects and measures the power supply points and potential difference measurement points along the X or Y direction, and then performs inverted imaging to obtain a total of four imaging results. Here, ρ in Figure 8 (a) xx represents the imaging results of the X-direction power supply and X-direction potential measurement, and ρ in (b) of Figure 8 xy represents the imaging results of the X-direction power supply and the Y-direction potential measurement, and ρ in (c) of Figure 8 yx represents the imaging results of the Y-direction power supply and the X-direction potential measurement, and (d)ρ in Fig. 8 yy represents the imaging results of the Y-direction power supply and the Y-direction potential measurement. As can be seen from the imaging results in Figure 8, there is a clear directionality in the conventional scalar resistivity method. For example, when the X-direction power supply and the X-direction potential measurement (ρ xx ) makes it impossible to clearly image the boundary of the fence along the Y direction, and spurious anomalous interference appears on the outer periphery in the Y direction. Similarly, the Y-direction power supply and Y-direction potential measurement (ρ yy ) makes it difficult to clearly image the boundary of the wall along the X direction, and spurious anomalous interference appears on the outer periphery in the X direction. xy and ρ yx In this case, more complex imaging structures, such as defects, deformations, and spurious anomalous interference, appear. Figure 8 (f) shows the apparent resistivity tensor matrix obtained by the tensor resistivity method, and the results of inversion imaging after extracting its rotational invariants. As can be seen from the figure, the imaging results are in good agreement with the actual wall model, with no directional defects and suppressed directional interference.

[0093] Figure 9 compares numerical simulations for different power supply methods. Figure 9(a) shows the model setup, with five small target models placed within the measurement area, while still using the grid electrode arrangement shown in Figure 7. Figure 9(b) shows the imaging result of the tensor resistivity method with a single grid node pitch. The five small target models are not clearly distinguishable. Figure 9(c) shows the imaging result of the tensor resistivity method with a six-node grid node pitch. The five small target models are still not clearly distinguishable. Figure 9(d) shows the imaging result of the tensor resistivity method (at the model boundary) with a 12-node grid node pitch. The five target models are clearly distinguishable. Further simulation experiments with larger power supply pitches proved that adding an external power supply point or combining external and internal power supply points is an effective way to improve imaging.

[0094] It is understood by those skilled in the art that the above are merely preferred examples of the invention and are not intended to limit the invention, and although the invention has been described in detail with reference to the above examples, those skilled in the art may still modify the technical solutions described in the above examples or replace some of the technical features with equivalents, and any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall fall within the protection scope of the invention.

Claims

1. A random distribution tensor resistivity measurement method, comprising: Step S1: Arranging a plurality of potential measurement sites P covering the entire measurement area in accordance with the ground surface conditions within the measurement area; Step S2: arrange four potential measurement electrode points M1, N1, M2, and N2 around each potential measurement site P, arrange one potential measurement station at each potential measurement site P, and the line connecting M1 and N1 intersects with the line connecting M2 and N2, the distance between M1 and N1 and the distance between M2 and N2 are electrode distance a, a=(1 / 10-1 / 20)H, and H is the exploration depth; Step S3: Arranging a plurality of power supply points within the measurement area, arbitrarily selecting four power supply points A1, B1, A2, and B2, and satisfying that the line connecting A1 and B1 intersects with the line connecting A2 and B2; First, the power supply station supplies power to the electrodes at A1 and B1, and the electrodes at all potential measurement sites P simultaneously measure potential. The power supply station supplies a power supply current I １ The potential difference ΔU of the power supply at A1 and B1 corresponding to M1, N1 and M2, N2 is measured at each potential measuring station. M1N1 （１） and ΔU M２N２ （１） The power supply station supplies power to the electrodes at A2 and B2, and the electrodes at all potential measurement sites P simultaneously measure the potential. The power supply station supplies the power supply current I ２ The potential difference ΔU of the power supply at each potential measuring station corresponds to M1, N1 and M2, N2. M1N1 （２） and ΔU M２N２ （２） Step S4 of measuring Power supply current I １ and I ２ , and based on the positional relationship between A1, B1 and point P, A1 and B1 obtain a first current density vector generated at point P and A2 and B2 obtain a second current density vector generated at point P, and the potential difference ΔU M1N1 （１） and ΔU M２N２ （１） Based on the electrode distance, A1 and B1 obtain a first electric field intensity vector generated at point P, and ΔU M1N1 （２） and ΔU M２N２ （２） and step S5 of obtaining a second electric field intensity vector generated by A2 and B2 at point P based on the electrode distance; and step S6 of vector-decomposing the first current density vector, the second current density vector, the first electric field strength vector, and the second electric field strength vector in the same coordinate system to calculate an apparent resistivity tensor.

2. The random distribution tensor resistivity measurement method of claim 1, further comprising: before performing S1, first dividing the entire measurement area into a plurality of sub-measurement areas, and then performing S1 to S6 in each sub-measurement area; and completing the tensor resistivity measurement for each sub-measurement area after completing the tensor resistivity measurement for the entire measurement area.

3. In this method, before executing S1, the entire measurement area is first divided into a plurality of sub-measurement areas, and S1 to S2 are executed in each sub-measurement area, and a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 are arranged in each sub-measurement area; The placement and selection of the power supply points in step S3 are replaced as follows: k internal power supply points are placed within each sub-measurement area, and l external power supply points are placed on the periphery of each sub-measurement area; one of the k internal power supply points is selected and named point O; two of the l external power supply points are arbitrarily selected and named A1 and A2; that is, B1 and B2 both overlap with point O; The random distribution tensor resistivity measurement method of claim 1 further comprises performing steps S4 to S6 in each sub-measurement area, and completing the tensor resistivity measurement of the entire measurement area when the tensor resistivity measurement of each sub-measurement area is completed.

4. Before executing S1, the entire measurement area is first divided into a plurality of sub-measurement areas, and S1 to S2 are executed in each sub-measurement area, and a potential measurement site P and potential measurement electrode points M1, N1, M2, and N2 are arranged in each sub-measurement area; The arrangement and selection of the power supply points in step S3 are replaced as follows: four or more external power supply points are arranged on the periphery of each sub-measurement area, and four of the external power supply points are arbitrarily selected and named A1, B1, A2, and B2, and the line connecting A1 and B1 intersects with the line connecting A2 and B2; The random distribution tensor resistivity measurement method of claim 1, characterized in that steps S4 to S6 are performed within each sub-measurement area, and when the tensor resistivity measurement for each sub-measurement area is completed, the tensor resistivity measurement for the entire measurement area is completed.

5. The random distribution tensor resistivity measurement method according to claim 4, characterized in that the external power supply points arranged on the periphery of each sub-measurement area are distributed in each direction of the periphery of the sub-measurement area.

6. The random distribution tensor resistivity measurement method according to claim 5, characterized in that there are eight external power supply points arranged on the periphery of the sub-measurement area, and they are distributed in eight directions, namely east, west, south, north, southwest, northwest, southeast, and northeast, on the periphery of the sub-measurement area.

7. 2. The random distribution type tensor resistivity measurement method according to claim 1, wherein in step S2, the potential measurement electrode points N1 and N2 overlap with the potential measurement site P.

8. The random distribution type tensor resistivity measurement method according to claim 1, characterized in that the power supply points B1 and B2 overlap at point O, and the power supply station is located at point O.

9. The random distribution tensor resistivity measurement method according to claim 1, characterized in that the pitch between adjacent potential measurement sites is 2 to 3 times the electrode distance, and the distance between adjacent power supply points is 3 to 5 times the distance between adjacent potential measurement sites.

10. A randomly distributed tensor resistivity measurement system, comprising: a plurality of power feed stations and a potential measurement station; The power supply station includes a power supply station host, a long-distance power supply cable, a power supply electrode, and a boost power supply; The power supply station host includes a first control module, a first power supply module, a first internal battery, a current measurement module, and a first GPS module, and the first control module is used to control the selection of power supply electrode channels throughout the power supply station, the setting of power supply parameters, the access of an external boost power supply, the internal power management, the power supply process current measurement, the GPS clock, and the registration of power supply current data measured in the power supply process, thereby forming time-series current data and storing it by segments at set time intervals; the current measurement module measures and digitizes the power supply current value using an A / D conversion circuit; the first power supply module is used to select a specific power supply channel and connect to the boost power supply through a power supply interface; the first internal battery is used to provide electrical energy necessary for the power station to operate for a long period of time; the first GPS module includes an external antenna controlled by the first control module, and continuously transmits GPS codes to the power supply station host after power-on and self-check is normal, and provides location and clock information; The power supply station host provides four power output ports, and connects the power supply electrodes located at the four power supply points A1, B1, A2, and B2 via the long-distance power supply cable, and sequentially supplies power underground; the potential measuring station includes a potential measuring station host, a potential measuring cable, and a potential measuring electrode; the potential measuring station host includes a second control module, a second power supply module, a second internal battery, a potential measuring module, and a second GPS module; the second control module is used to control the selection of the potentiometric electrode channel, the setting of the potential measurement parameters, the internal power management, the measurement and storage of the dual-channel potential difference, the registration of the GPS clock and the potentiometric data, and to generate a time series of potential difference data and store it by segments at set time intervals; the potential measurement module is used to simultaneously collect potential difference data of two cross-positioned potential measurement channels; The second power module is used to monitor and manage the monitoring status and charging process of the built-in battery; the second built-in battery is used to provide electrical energy required for the long-term operation of the potential measuring station; the second GPS module includes an external antenna controlled by the second control module, and continuously transmits GPS codes to the second control module after powering on and self-checking, providing position and clock information of the measuring station; The potential measurement station host provides four potential measurement ports, which connect the potential measurement electrodes located at M1, N1, M2, and N2 via the potential measurement cables, respectively, and receives potential difference information between the potential measurement electrode points.

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