Device and method for measuring electrical parameters of rock and soil sample

Abstract

The invention provides an electrical parameter measuring device and method for a rock and soil sample. The device comprises a device base, a horizontal holder assembly, a pressure assembly, an AB power supply electrode assembly, a top end M and N spring electrode assembly, a lateral MN probe electrode assembly and an electrical parameter measuring module. Two horizontal clamp assemblies are symmetrically arranged on the left side and the right side of the device base, pressure assemblies are installed on the horizontal clamp assemblies and abut against the AB power supply electrode set, the top end M and N spring electrode assemblies are installed at the two ends of the middle of the device base and stretch across the device base, and the lateral MN probe electrode assembly is installed on the rear side of the device base. And the electrical parameter measuring module is connected with an electrode column on the device base. The technical problems that in a traditional method, clamping force is difficult to control, contact is poor, current distribution is uneven, the process is opaque, data cannot be post-processed and the like are solved, and universalization, high precision and repeatable measurement of rock and soil samples are achieved.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical electrical property measurement technology, and particularly relates to a device and method for measuring the electrical parameters of geotechnical samples. Background Technology

[0002] In geophysical exploration, geological hazard investigation, and soil environmental pollution research, the resistivity and polarizability of soil and rock are important physical properties, which are influenced by a variety of factors such as compaction degree, water content, porosity, and temperature. Accurately obtaining the electrical parameters of soil and rock is of great significance for identifying underground anomalies, analyzing engineering geological conditions, and assessing the migration behavior of environmental pollutants.

[0003] Currently, electrical parameter testing primarily targets rock specimens. Typically, collected rock samples are processed into regular geometric shapes (such as cubes with sides of 10 cm) or core columns with a diameter of 1-2 inches are drilled. After grinding the two ends, measurements are taken using the four-electrode method. Existing methods often involve clamping the specimen tightly with vises or screws and adding electrode fluid to the power supply electrodes to improve electrical contact. However, this method has the following limitations in practical applications:

[0004] (1) The clamping force is difficult to control uniformly: excessive clamping pressure will cause the rock sample to crack, while insufficient pressure will result in poor contact between the power supply electrode and the side of the specimen, leading to unstable measurement results. Furthermore, different clamping forces have different degrees of influence on the measurement results.

[0005] (2) Poor electrode contact reliability: When the specimen end face is uneven, it is difficult for the power supply electrode to fit well with the specimen, which easily leads to poor contact and unstable power supply current. The specification recommends adding electrode liquid through the injection hole to improve contact, but when the electrode and the sample do not fit tightly, the electrode liquid is prone to leakage; for soil samples with large porosity, the electrode liquid will quickly seep into the interior and change the original electrical characteristics of the sample.

[0006] (3) Uneven current distribution: During the measurement process, the current is difficult to pass through the sample cross-section evenly, resulting in a significant difference in current density between the surface and the interior, and the measurement results obtained based on surface voltage sampling have a large error.

[0007] (4) Insufficient controllability and data transparency in the measurement process: Existing instruments typically output resistivity and polarizability values ​​directly after setting a set of fixed parameters (such as power-off delay, integration width, etc.), without providing intermediate process data. When the measurement state is unstable, operators cannot judge the reliability of the measurement process in real time.

[0008] (5) Difficulty in parameter adjustment and data reprocessing: If it is found that the original measurement parameters are not suitable for some samples, the parameters need to be adjusted and the measurements need to be repeated, which is inefficient and repetitive. If the waveform curves of voltage and current can be recorded simultaneously during measurement, the results under the new parameters can be obtained directly by recalculation without repeating the experiment, which is convenient for subsequent comparative analysis and parameter optimization.

[0009] Therefore, there is an urgent need for an electrical parameter measurement method and device that can be applied to both rock and soil specimens, has reliable contact, uniform current distribution, controllable measurement process, and supports post-processing of data. Summary of the Invention

[0010] The purpose of this invention is to provide a device and method for measuring the electrical parameters of soil and rock samples, which can be applied to the testing of electrical parameters of soil samples as well as rock samples.

[0011] To achieve the above objectives, the present invention employs the following technical means: An electrical parameter measuring device for soil and rock samples includes: a device base, a horizontal clamp assembly, a pressure assembly, an AB power supply electrode assembly, a top M and N spring electrode assembly, a lateral MN probe electrode assembly, and an electrical parameter measuring module; two horizontal clamp assemblies are symmetrically arranged on the left and right sides of the device base, and a pressure assembly is installed on the horizontal clamp assembly. The pressure assembly abuts against the AB power supply electrode assembly. The top M and N spring electrode assemblies are installed at both ends of the middle part of the device base and span across the device base. The lateral MN probe electrode assembly is installed on the rear side of the device base. The electrical parameter measuring module is connected to the electrode post on the device base.

[0012] Furthermore, the device base includes: a base, screw holes, a gate-shaped bracket, a sample support column, a horizontal clamp bracket and an electrode terminal block, and a rubber buffer pad; The sample support column can be adjusted and installed on the base through screw holes; the horizontal clamp bracket is symmetrically arranged on the left and right sides of the base; the electrode terminal block is fixed to the rear side of the base; the gantry bracket is welded to the middle of the base and spans across the base in the width direction; rubber buffer pads are provided on the four corners of the base plate.

[0013] Furthermore, the left and right sides of the electrode terminal block are respectively provided with a set of A terminal, M terminal, N terminal and B terminal, and the middle is provided with A1 terminal, M1 terminal, N1 terminal and B1 terminal. The A terminal and A1 terminal on the left and right sides are connected by wires, and the B terminal and B1 terminal on the left and right sides are connected by wires.

[0014] Furthermore, the horizontal clamp assembly includes: a guide block, a clamping screw, a horizontal clamp operating handle, a horizontal clamp guide bracket, and a horizontal clamp pressure plate; Two horizontal clamp guide brackets are symmetrically arranged on the horizontal clamp bracket, and the bottom of the guide block is fixed to the horizontal clamp guide bracket by bolts. The clamping screw passes through the central screw hole of the guide block, with one end connected to the horizontal clamping device operating handle and the other end connected to the horizontal clamping device pressure plate via a nut.

[0015] Furthermore, the pressure assembly includes: a pressure sensor, a polyester fiber block I, and a pressure transducer; The pressure sensor is embedded in the polyester fiber block I and connected to the horizontal clamping plate; the pressure sensor is connected to the pressure converter inside the electrical parameter measurement module via a signal line.

[0016] Furthermore, the AB power supply electrode assembly includes: two polyester fiber pads II and two copper sheet electrodes; A copper electrode is embedded in one end face of the polyester fiber pad II to form electrode A and electrode B; the two copper electrodes are connected to the A1 terminal and the B1 terminal respectively through electrode wires.

[0017] Furthermore, the top M and N spring electrode assembly includes: an electrode plate, a vertical clamping screw, a spring contact electrode M, a vertical clamping screw handle, a spring contact electrode N, and a polyester fiber support column; The two ends of the electrode plate are slidably connected to the U-shaped groove of the portal frame and are located within the frame of the portal frame; Spring contact electrode M and spring contact electrode N are symmetrically arranged on the electrode plate. Spring contact electrode M and spring contact electrode N are connected to the M terminal and N terminal on the right side of the electrode terminal block respectively through wires. Both spring contact electrode M and spring contact electrode N are provided with polyester fiber support columns; One end of the vertical clamping screw passes through the portal frame and is fixedly connected to the electrode plate via a flange, while the other end is equipped with a vertical clamping screw handle.

[0018] Furthermore, the lateral MN probe electrode assembly includes: a lateral probe electrode bracket, a bracket fixing angle bracket, and two retractable probe electrodes; The lateral probe electrode holder is fixed to the device base by bracket fixing angle brackets and bolts; two probe electrodes are symmetrically arranged on the left and right sides of the probe electrode holder; The two probe electrodes are connected to the M1 terminal and N1 terminal on the electrode terminal block, respectively. The probe electrode has a needle diameter of 1mm, the distance between the two probe electrodes is 50mm, and the needle is replaceable.

[0019] A method for measuring the electrical parameters of a soil and rock sample, comprising the following steps: S1. Conductive auxiliary material is prepared by mixing saturated copper sulfate solution with edible flour at a mass ratio of 1:2. S2. Load the soil sample into a perforated PVC pipe, and seal both ends of the PVC pipe with conductive material before installing copper end caps, or install copper end caps and conductive material at both ends of the core column to obtain the sample to be tested. S3. Place the prepared sample to be tested in the electrical parameter measuring device for soil and rock samples according to any one of claims 1-8, connect the electrodes and adjust the clamping pressure; S4. Apply a bipolar low-frequency pulse current to the sample through electrodes A and B, and simultaneously acquire the waveform curves of current and voltage. S5. Determine the measurement status based on the collected voltage and current waveform curves; S6. The acquired voltage and current waveforms are subjected to bias correction and quality judgment. After meeting the preset indicators, the resistivity and polarizability of the sample are calculated.

[0020] Furthermore, the preset indicators in step S5 include: (1) The voltage and current bias deviations during forward and reverse power supply in each measurement cycle are both less than 5.0%; (2) The voltage and current bias deviations during forward and reverse power outages in each measurement cycle are both less than 5.0%; (3) The root mean square error of voltage and current during forward and reverse power supply in each measurement cycle is less than 1.0; (4) The root mean square error of voltage and current during forward and reverse power outages in each measurement cycle is less than 1.0; (5) The normalized difference index of the data curves during the power supply period and the power outage attenuation period in each measurement cycle is less than 5.0%.

[0021] The beneficial effects of this invention are as follows: 1. This invention, through the design of an adjustable sample support column and a mechanical structure with coordinated horizontal and vertical clamping, and the use of a pressure assembly composed of a pressure sensor and a polyester fiber buffer block, can apply uniform, controllable, and quantifiable clamping pressure to samples in various physical states, from hard rock cores to loose remolded soil columns. This solution effectively solves the problems in the prior art where clamping force is difficult to control uniformly, excessive pressure will damage the sample, and insufficient pressure will result in poor contact.

[0022] 2. By combining conductive auxiliary material (saturated copper sulfate dough) with copper end caps, and using a complementary design of spring contact electrodes and lateral probe electrodes, reliable and stable electrical contact between the power supply electrodes (A, B) and the measuring electrodes (M, N) under different sample end face flatness conditions is ensured. This overcomes the shortcomings of poor contact, liquid leakage and sample contamination in the traditional liquid injection method, laying a physical foundation for accurate measurement.

[0023] 3. This invention, through the thorough filling of the power supply end face with conductive auxiliary materials and the uniform pressure of the end cap, promotes a more uniform current distribution across the sample cross-section, significantly reducing measurement errors caused by uneven current density. The complementary potential measurement schemes—the top spring contact electrode (for rock samples) and the lateral retractable probe electrode (for soil samples)—enable direct detection of the surface and internal potential fields, particularly suitable for accurate observation of excited polarization effects. This structure, combined with the intermediate gradient electrode arrangement, effectively overcomes the voltage sampling deviation caused by electric field distortion in the traditional two-end method, making the obtained resistivity and polarizability parameters more representative.

[0024] 4. During the measurement process, waveform data of current and voltage are simultaneously acquired and displayed in real time. Data quality is assessed through rigorous bias correction and five quantitative indicators (bias deviation, root mean square error, normalized difference index, etc.). Only data from qualified periods are used for parameter calculation, ensuring the traceability of results. The saving of raw waveform data allows for reprocessing after measurement by resetting calculation parameters (such as delay and integration width) as needed. Results under new parameters can be obtained without repeating the experiment, overcoming the inherent shortcomings of traditional instruments, such as single output results, opaque processes, and difficult parameter adjustments.

[0025] 5. This invention forms a complete and highly operable standardized process, from the preparation of conductive auxiliary materials, soil remodeling and sample loading, and rock sample end face treatment, to sample placement, pressure adjustment, data acquisition and processing. This method uses readily available materials (such as PVC pipes, saturated copper sulfate solution, and flour), and is suitable for preparing a series of comparative samples with different moisture contents, mineralization, or pollution levels, while effectively maintaining the original state of the samples. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the cylindrical sample measurement method provided by the present invention; Figure 2 This is a graph showing the changes in current flowing through the sample and voltage signal between the measuring electrodes MN, provided by the present invention. Figure 3 A schematic diagram of the measuring device provided by this invention; Figure 4 A schematic diagram of the base structure of the measuring device provided by the present invention; Figure 5 A schematic diagram of the base structure of the measuring device provided by the present invention; Figure 6 Top view of the measuring device provided by this invention; Figure 7 A front view of the measuring device provided by the present invention.

[0027] Reference numerals: 1-Device base; 2-Horizontal clamp assembly; 3-Clamping pressure sensing assembly; 4-AB power supply electrode assembly; 5-Top M and N spring electrode assembly; 6-Side MN probe electrode assembly; 7-Electrical parameter measurement module; 8-Sample; 101-Gate-shaped bracket; 102-Base rubber buffer pad; 103-Sample support column screw hole; 104-Base plate; 105-Sample support column; 106-Horizontal clamp bracket; 107-Electrode terminal block; 108-A electrode terminal; 109-M electrode terminal; 110-N electrode terminal; 111-B electrode terminal; 112-A1 electrode terminal; 113-M1 electrode terminal; 114-N1 electrode terminal. 115-B1 terminal block; 201-guide block, 202-clamping screw, 203-horizontal clamping device operating handle, 204-horizontal clamping device guide bracket, 205-horizontal clamping device pressure plate; 301-pressure sensor, 302-polyester fiber block I; 401-polyester fiber pad II, 402-copper sheet electrode; 501-electrode plate, 502-vertical clamping screw, 503-spring contact electrode M, 504-handle of vertical clamping screw, 505-spring contact electrode N, 506-clamping screw guide bushing, 507-flange, 508-polyester fiber support column; 601-lateral probe electrode bracket, 602-bracket fixing angle bracket, 603-probe electrode. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] The application principle of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] In this embodiment, to achieve the aforementioned resistivity and polarizability testing objectives for rock and soil samples, this invention proposes an electrical parameter measuring device for rock and soil samples, comprising: a device base 1, a horizontal clamp assembly 2, a clamping pressure sensing assembly 3, an AB power supply electrode assembly 4, a top M and N spring electrode assembly 5, a lateral MN probe electrode assembly 6, an electrical parameter measuring module 7, and a sample 8. Two horizontal clamp assemblies 2 are symmetrically arranged on the left and right sides of the device base 1. A clamping pressure assembly 3 is installed on the horizontal clamp base 2, and the pressure assembly 3 abuts against the AB power supply electrode assembly 4. The top M and N spring electrode assemblies 5 are installed at both ends of the middle portion of the device base 1 and span across the device base 1. The lateral MN probe electrode assembly 6 is installed on the rear side of the device base 1. The electrical parameter measuring module 7 is connected to the electrode posts on the device base 1, and the sample 8 is placed on the device base 1.

[0031] Please refer to Figures 1-7 The device base 1 includes a gate-shaped bracket 101, a base rubber buffer pad 102, a specimen support column screw hole 103, a base plate 104, a sample support column 105, a horizontal clamp bracket 106, and an electrode connection board 107.

[0032] The base plate 104 of the device base 1 is a rectangular steel plate, 440mm long, 350mm wide, and 5mm high. A portal-shaped bracket 101 is welded to the middle of the base 104. The portal-shaped bracket 101 is arranged along the width direction of the base 104 and spans across the base 104. Rubber buffer pads 102 are provided at the four corners of the base plate 104.

[0033] A horizontal clamp bracket 106 is symmetrically installed on the left and right sides of the base plate 104. The horizontal clamp bracket 106 is 60*100mm in length and width. The outer side of the horizontal clamp bracket 106 is aligned with the outer side of the base plate 104. The distance between the inner sides of the horizontal clamp brackets 106 on the left and right sides is 320mm. The horizontal center axis of the horizontal clamp bracket 106 coincides with the horizontal center axis of the base plate 104.

[0034] Four sets of screw holes 103 are symmetrically distributed along the horizontal central axis in the middle of the base plate 104. Each set has 10 screw holes, with 5 screw holes on each side. These are used to flexibly select the position for installing polyester fiber sample support columns 105. The sample support columns 105 have an outer diameter of 15mm and a height of 20mm. They are used to place the rock or soil specimen to be tested, preventing the specimen 8 from directly contacting the device base 1, thus achieving electrical insulation. The nearest screw holes 103 in each set are 20mm apart, and the farthest are 100mm apart. This allows the polyester fiber-coated sample support columns 105 to be flexibly moved according to the different diameters or volumes of the specimen 8 to accommodate specimens 8 of different sizes or shapes. The distance between two adjacent sets of screw holes 103 is 50mm to accommodate specimens 8 of different lengths. When measuring shorter specimens 8, the four sample support columns 105 are installed on the four symmetrically arranged screw holes 103 in the middle two sets. When measuring longer samples, four sample support pillars 105 are installed on the four screw holes 103 symmetrically located in the two sets on both sides.

[0035] An electrode connection plate 107 is installed on the rear side of the base 104 so that each electrode of the device can be connected to the corresponding terminal of the electrical parameter measuring module 7.

[0036] The electrode terminal block 107 is an insulating plate. On its left and right sides, there are sequentially arranged A-pole terminals 108, M-pole terminals 109, N-pole terminals 110, and B-pole terminals 111. In the middle, there are sequentially arranged A1-pole terminals 112, M1-pole terminals 113, N1-pole terminals 114, and B1-pole terminals 115. The A-pole terminals 108 and A1-pole terminals 112 on both sides are connected by wires, and the B-pole terminals 111 and B1-pole terminals 115 on both sides are connected by wires. These connections are used to connect to the pulse current signal output terminal of the electrical parameter measurement module 7, supplying power to the sample 8 under test. All terminals are 4mm banana plugs for easy connection of measurement wires.

[0037] When measuring rock or core samples, the four terminals A, M, N, and B on the right side are connected to the A, M, N, and B terminals of the electrical parameter measurement module 7, respectively. At this time, the M and N terminals on the right side of the electrode terminal block 107 are connected to contact electrodes M503 and N505 via wires to measure the potential difference on the rock sample. When measuring the electrical parameters of soil samples, the four terminals A, M, N, and B on the left side are connected to the A, M, N, and B terminals of the electrical parameter measurement module 7, respectively. At this time, the M and N terminals on the left side of the electrode terminal block 107 are connected to the two probe electrodes M and N on the lateral probe holder 6 via wires to measure the potential difference on the soil sample.

[0038] The horizontal clamp assembly 2 includes a guide block 201, a clamping screw 202, a horizontal clamp operating handle 203, a horizontal clamp guide bracket 204, and a horizontal clamp pressure plate 205.

[0039] Two horizontal clamp guide brackets 204 are symmetrically arranged on the horizontal clamp bracket 106. The bottom of the guide block 201 is fixed to the horizontal clamp guide bracket 204 by bolts. The horizontal clamping screw 202 passes through the central screw hole of the guide block 201. One end is equipped with a horizontal clamping operating handle 203, and the other end of the clamping screw 202 is connected to the horizontal clamping plate 205 by a nut. The axis of the clamping screw 202 is basically coincident with the horizontal axis of the specimen 8 to be tested placed horizontally on the sample support column 105. The horizontal clamping operating handle 203 can be rotated to make the horizontal clamping plate 205 at its front end move closer to the center along the axis, thereby clamping the specimen 8 to be tested.

[0040] The pressure sensing assembly 3 includes two pressure sensors 301 (left and right) and two polyester fiber blocks I302. A horizontal clamping plate 206 is fixedly connected to one end of the pressure sensor 301 by fixing bolts, and the other end of the pressure sensor 301 is embedded in the polyester fiber block I302. Hot melt adhesive is used to firmly bond the bottom of the pressure sensor 301 to the contact surface of the circular polyester fiber block I302. This design avoids rigid contact between the pressure sensor 301 and the specimen, providing a certain degree of cushioning. The signal lines of the pressure sensor 301 are all led out from the side holes of the corresponding circular polyester fiber block I302 and connected to the pressure converter inside the electrical parameter measurement module 7. The pressure value is converted by the pressure converter inside the electrical parameter measurement module 7 and then transmitted to the computer through the RS485 interface of the electrical parameter measurement module 7. The measurement control program on the computer displays the magnitude of the pressure clamped on the left and right sides of the sample, so that the measurement personnel can clearly know the magnitude of the clamping pressure on the left and right sides of the sample, so as to better adjust and control the clamping pressure at both ends of the sample and maintain the pressure balance applied to both ends of the specimen, avoiding the impact or damage to the physical properties of the sample when placing it.

[0041] The AB power supply electrode assembly 4 includes two polyester fiber pads II 401 (left and right) and two copper sheet electrodes 402. Each polyester fiber pad II 401 has a copper sheet electrode 402 embedded on one end face, forming electrode A and electrode B. The two copper sheet electrodes 401 are connected to terminals A1 112 and B1 115 respectively via electrode wires. This application allows for flexible disassembly or replacement of electrodes of different sizes to accommodate specimens with different cross-sections or lengths. During measurement, the movable electrodes A and B, together with the copper end caps on both sides of the sample and the conductive auxiliary material inside the end caps, form the power supply electrode for measurement.

[0042] The top M and N spring electrode assembly 5 includes an electrode plate 501, a vertical clamping screw 502, a spring contact electrode M 503, a vertical clamping screw handle 504, a spring contact electrode N 505, and a polyester fiber support column 508.

[0043] The electrode plate 501 is a thick acrylic plate. Both ends of the electrode plate 501 are slidably connected to the U-shaped groove of the portal bracket 101 and are located within the frame of the portal bracket 101. One end of the vertical clamping screw 502 passes through the portal bracket 101 and is fixedly connected to the electrode plate 501 via a flange 507. The vertical clamping screw 502 and the portal bracket 101 are limited by a clamping screw guide sleeve 506. The other end of the vertical clamping screw 502 is equipped with a vertical clamping screw handle 504. By rotating the vertical clamping screw handle 504, the electrode plate 501 can be vertically raised and lowered. Spring contact electrodes M503 and N505 are symmetrically arranged on the bottom surface of electrode plate 501, and each spring contact electrode M503 and N505 is provided with a polyester fiber support column 508. A portion of the spring contact electrode M503 and N505 is exposed above the polyester fiber support column 508. The center distance between the spring contact electrodes M503 and N505 is 50mm. The direction of the line connecting the spring contact electrodes M503 and N505 is consistent with the measurement direction of the sample. The spring contact electrodes M503 and N505 are 2mm higher than the top surface of the polyester fiber support column 508. The extension stroke of the spring contact electrodes is 8mm. When the vertical clamping screw 502 is rotated to lower the electrode pressure plate 501 until the polyester fiber support column 508 contacts the top of the sample to be tested, the spring contact electrodes M503 and N505 inside it make good contact with the top surface of the sample under the normal pressure of the spring. The larger pressure is absorbed by the polyester fiber support column 508 to protect the two spring contact electrodes from being damaged by excessive pressure.

[0044] Spring contact electrode M503 and spring contact electrode N505 are connected to the M terminal 109 and N terminal 110 on the right side of the electrode terminal block on the base 104 respectively via wires.

[0045] The lateral spring probe electrode assembly 6 includes a lateral probe electrode bracket 601, a bracket fixing angle bracket 602, and two retractable probe electrodes 603. The lateral probe electrode bracket 601 is fixed to the device base 1 by bolts via the bracket fixing angle bracket 602. The probe electrodes 603 are two detachable stainless steel spring needle-shaped electrodes, symmetrically mounted on the left and right sides of the lateral probe electrode bracket 601 by fastening nuts. The probe electrodes 603 can be extended or retracted by pulling the handle at the rear of the probe electrodes 603. The extension and retraction stroke of the probe electrodes 603 is 25mm, the distance between the two probe electrodes 603 is 50mm, and the needle diameter of the probe electrodes is 1mm, which can be replaced as needed. Before measuring the soil sample, the needles of the two probe electrodes 603 are inserted into the sample 8. The height of the two probe electrodes 603 is on the same horizontal plane. By adjusting the height of the lateral probe bracket 601, the probe electrodes 603 are slightly adjusted up and down to keep them flush with the two probe holes on the side of the PVC pipe of the sample to be tested, so as to smoothly insert them into the sample. The two probe electrodes 603 are connected to the M1 terminal 113 and N1 terminal 114 on the electrode terminal block via 4mm banana plugs at one end, respectively, for easy assembly and disassembly. Simultaneously, two pinholes on the two PVC pipes are used to restrict the insertion position of the probe electrodes 603 into the specimen, ensuring that the center distance between the two probe electrodes 603 is strictly maintained at 50mm, thus reducing measurement error.

[0046] The electrical parameter measurement module 7 consists of a DC power supply, a pressure converter, a pulse signal generator and controller, and a current and voltage synchronous acquisition module. The electrical parameter measurement module 7 is connected to a computer via a USB interface. The computer-side measurement software controls the module to apply a bidirectional low-frequency pulse current signal with adjustable frequency and amplitude to the sample under test, and controls the start and stop of the measurement process. During the measurement preparation stage, the computer-side measurement software displays the pressure applied to both sides of the sample in real time. During the measurement process, the current and voltage synchronous acquisition module converts the current signal flowing through the sample and the real-time voltage signal between the M and N electrodes into data, which is transmitted to the control computer. The computer-side software displays and calculates the measurement results.

[0047] A method for measuring the electrical parameters of a soil and rock sample, comprising the following steps: S1, Preparation of conductive auxiliary materials Since copper plates or sheets are commonly used as electrode materials in measurements, adding a neutral saturated salt solution related to copper can effectively reduce the polarization between the metal electrode and the dough, minimizing the impact of electrode polarization on the electrical parameters of the sample and making the measurement results more accurate. During preparation, a saturated copper sulfate solution (approximately 20% concentration) and edible flour are mixed in a 1:2 mass ratio and repeatedly kneaded until a uniform texture and smooth surface are achieved. The mixture is then wrapped in plastic wrap to prevent moisture loss, thus obtaining the conductive auxiliary material. This conductive auxiliary material is simple to prepare, relatively inexpensive, does not easily penetrate the sample, has excellent conductivity, is not easily flowable, and possesses good plasticity, maintaining a relatively stable state during measurement.

[0048] S2, Sample Preparation The specific steps for preparing soil samples are as follows: (1) Two 1.2mm holes are drilled on the outer side wall of the PVC pipe at 50mm intervals along its axis. The two holes are symmetrically distributed on the side wall along the axial direction so that the probe electrode 603 can be smoothly inserted into the soil sample during measurement.

[0049] (2) Crush the soil sample to be tested, dry it, and sieve it through a 200-mesh sieve. Alternatively, depending on actual needs, the original particle size of the soil sample can be maintained without crushing or sieving.

[0050] (3) Lock the split steel mold with the same inner diameter as the outer diameter of the PVC pipe, then put the soil sample into the PVC pipe. After pressing the soil sample according to the required degree of compaction, remove the steel mold and leave the PVC pipe. The soil sample is inside the PVC pipe. The soil sample can maintain a good column shape, and the cross section of the soil column is exactly the same as the inner cross section of the PVC pipe.

[0051] (4) After pressing and demolding, use conductive auxiliary material to seal the two ends of the PVC pipe, install copper end caps, and then wrap the entire sample with plastic wrap. The plastic wrap can be removed for measurement during the actual measurement.

[0052] (5) After the measurement is completed, when it is necessary to clean the sample, simply let it dry properly and the saturated copper sulfate dough at both ends of the PVC pipe will fall off naturally. Then remove the original soil inside the pipe.

[0053] When preparing soil samples with different moisture contents or different concentrations of pollutants of the same type, the conductive auxiliary material and the sealing effect of the plastic wrap can effectively maintain the moisture content or pollutant concentration inside the sample at the level at the time of sample preparation during measurement, and can also ensure good electrical contact between the two end faces of the sample and the metal electrodes during measurement.

[0054] To measure samples with different moisture contents, the dry mass of the soil needs to be measured during sample preparation. and the mass after adding water or solution In order to calculate its moisture content The calculation formula is as follows:

[0055] The core sample preparation process is as follows: (1) Using a cutting machine, cut off the irregular parts at both ends perpendicular to the core column axis, leaving a relatively standard columnar section with a length of 100mm to 200mm in the middle section; (2) Clean the dust and particles off the surface of the columnar lithological sample with a damp cloth; (3) Take two copper end caps with a diameter similar to that of the cylindrical sample. Fill the copper end caps with an appropriate amount of saturated copper sulfate dough conductive material. Cover the two ends of the core column with the two copper end caps respectively. Hold the rock column between the two copper end caps and press the two copper end caps lightly so that the dough in the two ends is evenly filled between the end face of the core sample and the cap.

[0056] If it is necessary to measure core samples with different moisture contents, the core samples need to be soaked in water appropriately, and the mass of the dry sample before soaking and the wet sample after soaking need to be measured and recorded. The mass of the wet sample after soaking needs to be measured after the surface is dried in order to calculate the moisture content of the core sample. Since it is not easy to obtain the constant weight of the rock sample after drying, the moisture content given is usually the moisture content relative to the naturally dried sample.

[0057] For rock samples with general shapes (irregular shapes), when measuring electrical parameters in different directions, a cutting machine can be used to cut the rock sample into standard hexahedral shapes with sides no less than 100mm in the direction to be measured, forming three sets of parallel surfaces. After cleaning off the surface dust, two appropriately sized round or square copper end caps are used, with conductive material added to the bottom, to cover the two sides in the direction to be measured. The sample is placed between the two copper end caps, and the copper end caps on both sides of the sample are gently pressed to ensure that the conductive material is evenly distributed between the sample cross-section and the copper end caps. Excessive force should be avoided to prevent excessive extrusion of the conductive material. If it is necessary to measure electrical parameters in another direction, the measurement direction of the sample can be changed.

[0058] S3, Place the sample to be tested Rotate the top vertical clamping screw 502 to raise the top electrode plate 501 to its highest position. Place the prepared sample horizontally on the sample support column 106 on the device base 1. Place polyester fiber blocks II 401 on both sides of the sample, so that the copper sheet electrodes 402 on the polyester fiber blocks II 401 are in contact with the copper end caps on both sides of the sample.

[0059] If the sample to be tested is a reshaped soil sample, rotate the PVC tube containing the soil sample appropriately so that the two small holes on its sidewall face the lateral probe electrode 603 and align the two small holes with the insertion direction of the probe electrode 603. Rotate the vertical clamping screw 502 at the top of the gate-type bracket 101 so that the two polyester fiber support columns on the top electrode plate 501 press down on the sample to prevent it from shaking. Then, insert the two probe electrodes 603 on the lateral probe electrode bracket 601 mounted on the base 1 horizontally into the two holes on the sidewall of the PVC tube, with an insertion depth of about 10 mm, to obtain the potential difference between points M and N on the soil sample during measurement. Operate the horizontal clamping assembly 2 to clamp the sample from both ends, ensuring good contact between the A and B electrodes and the copper end caps at both ends of the sample. At the same time, the pressure assembly 3 senses the clamping pressure on both sides of the sample to ensure that both sides of the sample bear equal preset clamping pressure.

[0060] If the sample to be tested is a rock sample, whether it is a columnar core sample or a regular hexahedral rock sample, it is necessary to rotate the probe electrode 603 to fix the nut and screw, or use the handle at the tail of the probe electrode 603 to retract the lateral M and N probes until the needles cannot contact the sample. Then rotate the top clamping screw to slowly lower the top electrode plate, so that the two insulating support columns on the bottom surface of the top electrode plate press down on the sample, keeping the sample stable. The two spring contact electrodes M and N installed in the two polyester fiber insulating support columns can then make good contact with the top of the sample. This allows the potential difference between points M and N on the sample to be obtained during measurement. Then operate the horizontal clamp to hold the sample, ready for measurement.

[0061] When placing the soil sample to be tested, the pressure should not be too high when adjusting the horizontal clamps at both ends to prevent the bottom surface of the copper end caps on both sides of the sample from directly contacting the outer wall of the PVC pipe, so that the measured pressure data is the actual pressure applied to the sample, rather than the pressure applied to the PVC pipe wall.

[0062] The advantages of this intermediate gradient quadrupole array device with spring contact electrodes M, N, A, and B are: (1) The sampling positions of spring contact electrodes M and N are not on the two end faces of the sample, but in the middle part of the sample. Even if a high supply voltage is applied to both ends of A and B electrodes, the potential difference between spring contact electrodes M and N will not be too high, which can effectively avoid the risk of the measurement voltage between M and N exceeding the upper limit of the measuring instrument or damaging the input circuit of the measuring instrument; (2) Because there is a full filling of saturated copper sulfate dough at both ends of A and B electrodes, The current through electrodes A and B can be evenly distributed to the entire cross section of the soil column to be tested, so that the current density at various points on the cross section reaches a relatively balanced level. Accurate measurement data can be obtained by using a probe to penetrate the soil sample or by sampling the voltage signal on the surface of the rock sample. (3) Even if the end face of the sample is not flat, the filling of the plastic conductive material can make the electrode fit tightly with the surface of the sample, ensuring the stability of the power supply current and not transmitting the polarization effect of the power supply electrode to the measuring electrode. (4) The measurement results are basically unaffected by the contact resistance between the power supply electrode and the sample.

[0063] Connect the A, B, M, and N terminals on the electrode terminal block 107 to the corresponding A, B, M, and N terminals on the measurement module using wires to complete the placement of the sample to be tested.

[0064] Generally, polarizability is more advantageous than resistivity in measuring soil metal ion or organic pollution. Therefore, if both parameters can be obtained in a single measurement, using both resistivity and polarizability to assess the physicochemical properties of a soil sample is more reliable than using resistivity alone.

[0065] S4. Measurement of Electrical Parameters. To simultaneously measure the resistivity and polarizability of the sample under test, a bipolar low-frequency pulse voltage signal of a certain intensity is applied to the sample under test through electrodes A and B during measurement, instead of a constant DC current. The frequency and amplitude of the pulse voltage signal output by the electrical parameter measurement module are adjustable. One cycle of the signal is divided into four segments, with the current transformation rhythm being: forward power supply - power off - reverse power supply - power off. Each segment has an equal time interval, which can be 4s, 8s, 16s, 32s, etc., and remains unchanged after selection. It is recommended to choose a larger value to accommodate samples with strong excitation polarization characteristics and long charge and discharge times, allowing for longer charging and discharging times. The current enters the sample under test from the positive terminal of the signal source E through electrode A, and returns to the negative terminal of the power supply through electrode B and the ammeter, forming a closed loop. The distance between the two probes M and N is... The cross-sectional area of ​​the sample being tested is The potential difference between the two probes M and N was measured to be The magnitude of the current in the circuit is Both voltage and current change over time. During the measurement, the electrical parameter measurement module synchronously acquires the voltage between two points M and N on the sample at a sampling frequency of not less than 500Hz. and the current flowing through the sample cross section The data is then transmitted to a computer via USB, where the collected voltage and current data are displayed and saved in real time. The voltage and current waveforms during the measurement process are shown below. Figure 2 Each sample must be measured for at least 3 complete measurement cycles.

[0066] Recording and displaying the waveform of the supply current during the measurement process effectively monitors the power supply and measurement status. By judging the waveform of the voltage signal between M and N, it can be seen whether the voltage change curve between M and N meets the requirements throughout the measurement process. Only when both meet the requirements can the final output result have high reliability. Therefore, real-time display and recording of voltage and current waveforms during the measurement process has important reference value. In addition, after all samples have been measured and all sample quality waveform data have been obtained, the resistivity and polarizability of all samples can be recalculated using the optimal calculation parameters. This effectively avoids the risk of reworking all samples if the measurement results are questionable due to incorrectly set optimal calculation parameters during the measurement process.

[0067] S5. Method for determining the measurement state. The current signal waveform should remain stable during each forward and reverse power supply period, without significant jumps, indicating good contact between the power supply electrode and the sample, and a stable and normal power supply. Simultaneously, the voltage signal during the forward power supply period... It rises slowly, then tends to a stable value. During the period when forward power supply is stopped, the voltage signal is a non-zero value. The value gradually decreases and tends to During reverse power supply, the voltage signal is supplied by... The initial value is used as a reference, and as the power supply continues, the absolute value slowly increases and tends to stabilize. During the period when reverse power supply stops, the voltage signal is a non-zero value. Gradually tending to If the voltage signal exhibits distortions or jumps that do not conform to the above rules, it indicates that the measurement process is unstable and the measurement results will be unreliable.

[0068] S6. Data Curve Correction and Quality Judgment Method. After the measurement data sequence is checked and corrected for voltage and current bias, parameters for measuring the quality of the data curve are calculated and used to identify the quality of the measurement data. These parameters are the voltage and current bias deviation in each measurement cycle, the root mean square error of the data during forward and reverse power supply, the root mean square error of current and voltage during forward and reverse power outages, and the curve normalization difference index. The data correction method and parameter calculation method are as follows:

[0069] Taking the correction of the acquired voltage signal as an example, the average values ​​of the data sequences during the forward power supply period and the data sequences during the reverse power supply period of each measurement cycle are taken separately. After averaging the two values ​​again, the DC bias voltage during the power supply period is obtained. Subtract the data sequence during the forward power supply period and the data sequence during the reverse power supply period from each measurement cycle respectively. This method achieves correction of the DC bias voltage for the data. The data sequences during the forward power supply stop period and the reverse power supply stop period of each measurement cycle are averaged separately, and then the average of these two values ​​is taken again to obtain the DC bias voltage during both forward and reverse power supply stop periods. Subtract the data sequences during the forward power supply stoppage and the reverse power supply stoppage periods of this measurement cycle respectively. To correct the DC bias voltage data during power outages, the following formula is used to calculate the DC voltage bias deviation during power supply and power outage periods:

[0070] Using the data sequence corrected for DC bias voltage and current, calculate the root mean square error of the data sequence during the forward and reverse power supply periods and the forward and reverse power supply stop periods in each measurement cycle according to the following formulas:

[0071] The formula for calculating the average signal level of the voltage signal during the power supply cycle is:

[0072] The formula for calculating the normalized difference index of data curves is:

[0073] The calculation methods for the parameters corresponding to the current data sequence are the same as those for the voltage data sequence. After bias voltage and bias current correction, the data sequence is considered to be of acceptable measurement quality if it simultaneously meets the following five preset indicators:

[0074] (1) The voltage and current bias deviations during the forward and reverse power supply periods in each measurement cycle are all less than 5.0%; (2) The voltage and current bias deviations during forward and reverse power outages in each measurement cycle are both less than 5.0%; (3) The root mean square error of voltage and current during the forward and reverse power supply periods in each measurement cycle is less than 1.0; (4) The root mean square error of voltage and current during the forward and reverse power outages in each measurement cycle is less than 1.0; (5) The normalized difference index of the data curves during the power supply period and the power outage attenuation period in each measurement cycle is less than 5.0%.

[0075] Normally, the bias values ​​of DC voltage and current during forward and reverse power supply should correspond to the same bias values ​​during forward and reverse power outages. However, due to factors such as potential DC bias in the low-frequency pulse power supply output of the measurement module, weak polarization of the power supply electrodes, and thermal effects of the sample during measurement, the system output current and voltage will not be completely zero, and the voltage curve acquired during power outages will not completely decay to zero. Therefore, the acquired data may contain DC bias voltage, causing the data curve to be asymmetrical during forward and reverse power supply or power outages. Thus, the measurement data needs to be corrected to eliminate the effects of weak leakage current in the output circuit of the measuring instrument or measurement module, weak polarization effects of the power supply electrodes, and thermal effects. Only after appropriate correction can more accurate electrical parameters be obtained.

[0076] S7. Calculation method of electrical parameters. Electrical parameters include resistivity and polarizability. After the full waveform voltage and current data sequences are corrected in step S6, and the quality of the curve data in each measurement cycle meets the five requirements in S6, the data can be extracted and the resistivity and polarizability of the samples can be calculated using the following method based on the corrected full waveform data sequences of synchronously changing voltage and current in each measurement cycle:

[0077] Because the voltage and current of the signal source are not stable at the moment of power-on during the measurement process, the measured voltage and current data may fluctuate. Therefore, when extracting and calculating data, it is necessary to appropriately avoid data from the fluctuating periods during power-on and power-off. The calculation starts from the moment of power-on during the first and second half-cycles of each measurement cycle, and the delay time is taken as the starting point. The relatively stable segment of the current curve thereafter is taken as the time width. The mean values ​​of the internal voltage data sequence and the current data sequence are respectively denoted as: , and , To avoid voltage and current fluctuations at the moment of power outage, the time elapsed between the end of forward and reverse power supply is taken as... The width of the previous stable section was The mean of the voltage data sequence within the segment is denoted as follows: , The delay time at the end of the forward and reverse power supply is... The width after is The mean of the voltage data sequence within the time segment is denoted as . and The positions of each voltage and current signal in the waveform are shown in Figure-1.

[0078] The formulas for calculating the resistivity and polarizability of the sample in each measurement cycle are as follows:

[0079]

[0080] and These represent the cross-sectional area of ​​the sample and the distance between electrodes M and N, respectively.

[0081] The resistivity and polarizability are averaged over multiple measurement periods with acceptable data quality. and The final electrical parameter measurement results of the sample are then used as the basis for evaluating the reliability of the electrical parameter measurement results. The calculation formula is as follows:

[0082]

[0083] In comparing parameters from multiple electrical samples, the delay time for extracting voltage and current when calculating resistivity for each sample is considered. Interval time Delay time Time slice width and All should remain unchanged. Usually, it is taken as... , , , , These values ​​are related to the sampling rate setting and can be adjusted appropriately depending on the sampling rate set when measuring the electrical parameters of the wooden block.

[0084] For cylindrical rock cores and soil samples, the diameter of the sample being tested is The distance between the two voltage sampling points M and N is The effective cross-sectional area of ​​the sample is:

[0085] For a hexahedral rock sample, the interface through which the current flows is rectangular, and the width of the rectangular cross-section is... The height is The effective cross-sectional area of ​​the sample is:

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for measuring the electrical parameters of soil and rock samples, characterized in that, The device base, horizontal holder assembly, pressure assembly, AB power supply electrode assembly, top M, N spring electrode assembly, lateral MN probe electrode assembly, and electrical parameter measurement module are provided. The device base includes a base, screw holes, a door-shaped support, a sample support column, a horizontal holder bracket, an electrode wiring board, and a rubber buffer pad.

2. The apparatus for measuring an electrical property of a geotechnical sample according to claim 1, wherein, The sample support column is adjustably installed on the base through the screw holes. The horizontal holder bracket is symmetrically arranged on the left and right sides of the base.

3. The apparatus of claim 2, wherein, The electrode wiring board is fixed to the rear side of the base, and the door-shaped support is welded to the middle part of the base and spans the base in the width direction.

4. The apparatus for measuring an electrical property of a geotechnical sample of claim 1, wherein, The rubber buffer pads are arranged on the four corners of the base. The left and right sides of the electrode wiring board are respectively provided with a group of A, M, N, and B electrode terminals, and the middle part is provided with A1, M1, N1, and B1 electrode terminals. The A electrode terminals on the left and right sides are connected to the A1 electrode terminals through wires.

5. The apparatus for measuring an electrical property of a geotechnical sample of claim 1, wherein, The horizontal holder assembly includes a guide block, a clamping lead screw, a horizontal holder handle, a horizontal holder guide support, and a horizontal holder pressing plate. The guide block is fixed to the horizontal holder guide support through a bolt at the bottom.

6. The apparatus of claim 1, wherein, The clamping lead screw passes through the center screw hole of the guide block, and one end is connected to the horizontal holder handle, and the other end is connected to the horizontal holder pressing plate through a nut. The pressure assembly includes a pressure sensor and a polyester fiber block I.

7. The apparatus of claim 1, wherein, The pressure sensor is embedded in the polyester fiber block I and connected to the horizontal holder pressing plate. The pressure sensor is connected to the pressure converter inside the electrical parameter measurement module through a signal line. The AB power supply electrode assembly includes two polyester fiber pads II and two copper sheet electrodes. The copper sheet electrodes are embedded on the end face of one end of the polyester fiber pad II to form A and B electrodes. The two copper sheet electrodes are connected to the A1 and B1 electrode terminals through electrode wires, respectively. The top M, N spring electrode assembly includes an electrode plate, a vertical clamping lead screw, a spring contact electrode M, a vertical clamping lead screw handle, a spring contact electrode N, and a polyester fiber support column. The two ends of the electrode plate are slidingly connected to the U-shaped groove of the door-shaped support and located inside the frame of the door-shaped support. The spring contact electrode M and the spring contact electrode N are symmetrically arranged on the electrode plate. The spring contact electrode M and the spring contact electrode N are connected to the M and N electrode terminals on the right side of the electrode wiring board through wires, respectively. The spring contact electrode M and the spring contact electrode N are provided with a polyester fiber support column. One end of the vertical clamping lead screw is fixedly connected to the electrode plate through a flange of the door-shaped support, and the other end is provided with a vertical clamping lead screw handle.

8. The apparatus of claim 1, wherein, The lateral MN probe electrode assembly comprises a lateral probe electrode support, a support fixed angle code, and two telescopic probe electrodes; The lateral probe electrode support is fixed on the device base by the support fixed angle code through bolts; the probe electrode support is symmetrically provided with two probe electrodes on the left and right sides; The two probe electrodes are connected with the M1 and N1 electrode connection posts on the electrode connection plate respectively; The needle diameter of the probe electrode is 1mm, the distance between the two probe electrodes is 50mm, and the needle can be replaced.

9. A method for measuring the electrical parameters of a soil and rock sample, characterized in that, The method comprises the following steps: S1, a conductive auxiliary material is prepared by mixing saturated copper sulfate solution and edible flour at a mass ratio of 1:2; S2, the soil sample is loaded into a PVC pipe with holes, and the pipe openings at both ends are sealed with conductive auxiliary materials, and then copper end covers are loaded or copper end covers and conductive auxiliary materials are loaded at both ends of the rock core column body to obtain the sample to be measured; S3, the prepared sample to be measured is placed in the geotechnical sample electrical parameter measuring device according to any one of claims 1-8, the electrodes are connected, and the clamping pressure is adjusted; S4, a bipolar low-frequency pulse current is loaded to the sample through the A electrode and the B electrode, and the waveform curves of the current and the voltage are synchronously collected; S5, the state of measurement is judged according to the collected voltage and current waveform curves; S6, the collected voltage and current waveform curves are subjected to bias correction and quality discrimination, and after meeting the preset index, the resistivity and polarization rate of the sample are calculated.

10. The method of measuring an electrical parameter of a geotechnical sample according to claim 9, wherein, The preset index in step S5 includes: (1) the voltage and current bias deviation during the forward and reverse power supply in each measurement period is less than 5.0%; (2) the voltage and current bias deviation during the forward and reverse power supply in each measurement period is less than 5.0%; (3) the root mean square error of voltage and current during forward and reverse power supply in each measurement period is less than 1.0; (4) the root mean square error of voltage and current during forward and reverse power supply in each measurement period is less than 1.0; (5) the normalized difference index of the data curve during power supply and power-off decay period in each measurement period is less than 5.0%.

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