A composite resistance reducing electrode and a high density electrical method of resistance reduction using the electrode

Abstract

The application relates to a composite resistance-lowering electrode and a high-density electrical method for lowering resistance by applying the electrode, and relates to the technical field of resistance-lowering electrodes, and solves the problem that the prior art is difficult to simultaneously meet the requirements of long-term stable resistance lowering, flexible adaptation to different soil environments, corrosion resistance and low-cost exploration. The electrode comprises a plurality of nested hollow rod bodies and a slow-release ion assembly; the rod bodies are sequentially sleeved from top to bottom, and the adjacent rods are limited in extension by limiting devices; the rod bodies are made of titanium alloy material, and the side walls are provided with permeation micropores; the bottom end of the lowermost rod body is provided with a conical electrode head; the slow-release ion assembly is arranged in the rod body, and comprises chlorides, bentonite, nano titanium dioxide and a curing agent. During exploration, a hole is dug at a target position, the electrode is inserted, and a composite conductive medium is filled in the gap between the electrode and the hole; saturated brine is injected from the top end of the electrode and then sealed; the grounding resistance is detected, if the preset value is not met, saturated brine, the conductive medium or the extension length of the electrode is adjusted until the standard is met.

Description

Technical Field

[0001] This invention relates to the field of resistance-reducing electrode technology, specifically to a composite resistance-reducing electrode and a high-density electrochemical resistance-reducing method using the electrode. Background Technology

[0002] High-density electrical resistivity tomography (EDT) is one of the core technologies in the field of geophysical exploration. By deploying a high-density electrode array on the surface, applying a stable current to the underground and collecting potential difference signals, it can invert the resistivity distribution of underground media. It has been widely used in mineral resource exploration, urban underground space exploration, hydrogeological surveys and engineering geological exploration.

[0003] Grounding resistance is a core parameter that determines the accuracy and reliability of high-density electrical resistivity tomography (EDT). Excessive grounding resistance directly leads to attenuation of the transmitted current, a decrease in the effective signal-to-noise ratio, and an increase in electromagnetic interference, ultimately causing distortion of the detection data, a decrease in resolution, and even the inability to complete effective data acquisition.

[0004] Currently, high-density electrical resistivity reduction technology mainly focuses on two directions. The first is to optimize the electrode-soil contact conditions by selecting high-conductivity electrode materials such as copper and galvanized steel, or by using methods such as excavating holes and backfilling with conductive media to expand the effective contact area between the electrode and the soil, thereby reducing contact resistance. The second is to improve the conductivity of the soil itself by injecting salt water into the soil or laying resistance-reducing agents to directly reduce soil resistivity and improve overall conductivity.

[0005] While the aforementioned technologies have improved the grounding resistance problem to some extent, they still suffer from insurmountable systemic defects in actual field exploration. Firstly, the resistance reduction effect is unstable. Traditional resistance-reducing agents (such as salt and graphite powder) are easily affected by environmental humidity. In arid regions, the resistance-reducing effect significantly diminishes after rapid evaporation of water, and the agents are easily washed away by rainwater, failing to achieve long-term resistance reduction. Secondly, the contact between the electrode and the soil is not tight enough. High-density electrode arrays are densely packed, and traditional electrodes have fixed lengths, making them unsuitable for soils or hardened surfaces such as asphalt with varying depths, hardness, and surface conditions. This can easily lead to electrode loosening and poor contact, resulting in increased contact resistance. Thirdly, construction is not convenient enough. During field exploration, the processes of hole excavation, electrode placement, and resistance-reducing agent filling are cumbersome, affecting detection efficiency. Fourthly, corrosion resistance is poor. Traditional metal electrodes are easily corroded in soils with high acid, alkali, and salt content, shortening their service life and increasing exploration costs. Corrosion-resistant graphite-based or composite electrode materials are complex to process and expensive, making large-scale application difficult.

[0006] In summary, existing technologies struggle to simultaneously meet the demands of high-density electrical resistivity tomography (EDT) exploration, which requires long-term stable resistivity reduction, flexible adaptation to different soil environments, convenient construction, corrosion resistance, and low cost. Therefore, developing such synergistically integrated resistivity reduction technologies is crucial for overcoming existing technological bottlenecks and improving the quality and efficiency of high-density EDT exploration. Summary of the Invention

[0007] To address the challenges of existing technologies in simultaneously meeting the requirements of long-term stable resistance reduction, flexible adaptation to different soil environments, convenient construction, corrosion resistance, and low cost in high-density electrical resistivity tomography, this invention proposes a composite resistance-reducing electrode and a high-density electrical resistivity tomography method using this electrode.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A composite resistance-reducing electrode includes multiple nested hollow rods and a slow-release ion assembly; The rods are connected sequentially from top to bottom, and the extension and retraction of adjacent rods are achieved by a limiting device; the rods are made of titanium alloy, the surface of the rods is coated with a TiO2 film, and the side walls of the rods are provided with permeable micropores; the bottom end of the lowest rod section is provided with a conical electrode head; The slow-release ion assembly is built into the hollow rod body; the slow-release ion assembly includes chloride, bentonite, nano titanium dioxide and curing agent in a mass ratio of 40:30:15:15; the chloride is a mixture of potassium chloride and sodium chloride in a mass ratio of 1:1.

[0009] Preferably, the permeation micropores are evenly distributed in a spiral shape along the axial direction of the rod, with a micropore diameter of 0.1~0.5mm and a micropore spacing of 5~8cm.

[0010] Preferably, the length of a single section of the rod is 0.2~0.3m, the total telescopic length ranges from 0.2~1m, and the wall thickness is 3~5mm.

[0011] Preferably, the limiting device is a snap-on or threaded limiting structure.

[0012] This invention also provides a high-density electrochemical resistance reduction method, which utilizes the aforementioned composite resistance-reducing electrode. The method includes the following steps: S1. Adjust the electrode to the target extension length according to exploration needs, and lock each section of the rod body through the limiting device; S2. Excavate a cylindrical hole at the target measuring point, and then insert the conical electrode head into the hole to make the electrode rod fully contact the soil. S3. Fill the gap between the electrode and the hole with a composite conductive medium made of graphite powder, bentonite and undisturbed soil. S4. After filling, inject saturated saline solution from the top of the telescopic electrode body, and then seal the top. S5. If the grounding resistance of the detection electrode does not meet the preset threshold, then inject saturated saline solution, add conductive medium, or adjust the hole depth and electrode extension length until the resistance reduction target is achieved.

[0013] Preferably, the diameter of the cylindrical hole is 2-3 cm larger than the diameter of the composite resistance-reducing electrode, and the depth is shorter than the extension length of the composite resistance-reducing electrode.

[0014] Preferably, the composite conductive medium is filled using a layered compaction method, with each layer having a compaction thickness of 10-15 cm and an overall compaction density ≥1.5 g / cm³. 3 .

[0015] Preferably, the mass ratio of graphite powder, bentonite, and undisturbed soil in the composite conductive medium is 30:20:50.

[0016] Preferably, a mixed humectant of glycerol and sodium carboxymethyl cellulose is added to the composite conductive medium, wherein the mass ratio of glycerol to sodium carboxymethyl cellulose is 2:1. Preferably, the mass ratio of the mixed moisturizer to the composite conductive medium is 5:95.

[0017] The composite resistance-reducing electrode and the high-density electrochemical resistance-reducing method using this electrode provided by this invention, through the synergistic design of a retractable hollow titanium alloy rod, a fixed-ratio columnar slow-release ion assembly, and precise filling with a composite conductive medium, coupled with standardized and streamlined construction operations, achieve dual innovation in structure and process. This fundamentally solves the industry pain points of existing high-density electrochemical resistance-reducing technologies, such as unstable resistance-reducing effects, poor soil compatibility, cumbersome construction, insufficient corrosion resistance, and high costs. Compared with existing technologies, it has significant advantages, as detailed below: 1. The columnar slow-release ion assembly built into the electrode of this invention provides a continuous supply of conductive ions via chloride, while bentonite locks in water and ions, and nano-titanium dioxide stabilizes the assembly structure. Experimental verification shows that it can continuously release conductive ions for more than 48 hours. Combined with a composite conductive medium composed of graphite powder, bentonite, and undisturbed soil, and a humectant compounded with glycerol and sodium carboxymethyl cellulose, it effectively locks in moisture, delays ion loss, and prevents the resistance reduction effect from being diminished by environmental humidity. It is also suitable for various complex soil environments, including high resistivity, acidic, alkaline, and saline soils, providing a long-lasting and stable resistance reduction effect.

[0018] 2. The electrode of this invention adopts a multi-section nested hollow titanium alloy rod design, which can flexibly adjust the length according to exploration needs, perfectly adapting to soil environments of different depths and hardnesses, solving the problems of loosening and poor contact of traditional fixed-length electrodes; the spirally distributed permeable micropores on the side wall of the rod allow the conductive ions released by the slow-release ion component to permeate evenly into the surrounding soil, avoiding resistance reduction deviation caused by uneven local ion concentration; at the same time, the composite conductive medium filling the gap between the electrode and the pores has both high conductivity and soil compatibility, which can achieve a tight conductive connection between the electrode and the soil on the pore wall, greatly reducing contact resistance, which is far superior to traditional copper electrodes and graphite-based electrodes.

[0019] 3. The electrode rod of this invention is made of titanium alloy and undergoes anodizing treatment, forming a dense TiO2 oxide film on the surface. After immersion in acidic, alkaline, and saline soil corrosive environments, the weight loss rate is extremely low, and there is no obvious surface corrosion. This is far superior to easily oxidized and corroded copper electrodes and graphite-based electrodes that are prone to spot corrosion, significantly extending the field service life of the electrode and reducing electrode replacement and maintenance costs. At the same time, the composite conductive medium uses the original soil at the exploration site as the main component, and the slow-release ion component uses industrial-grade conventional raw materials, requiring no customized processing. The raw materials are readily available and inexpensive, and no additional conductive layer is required during construction, further controlling the overall exploration cost. It balances corrosion resistance and economy, making it suitable for large-scale promotion and application.

[0020] 4. This invention designs a standardized resistance reduction construction process, and the electrode extension and retraction adjustment operation is convenient, without the need to customize the electrode according to the soil depth; the composite conductive medium can be directly filled into the gap between the electrode and the hole, and a layered compaction process can be used to achieve a dense fit, without the need for cumbersome auxiliary procedures, which can greatly improve construction efficiency and has broad application prospects. Attached Figure Description

[0021] Figure 1 This is a schematic diagram showing the extended and retracted states of the composite resistance-reducing electrode of the present invention; Figure 2 This is a cross-sectional schematic diagram of the composite resistance-reducing electrode of the present invention in use; Figure 3 This is a schematic flowchart of the resistance reduction method of the present invention. Detailed Implementation

[0022] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0023] Example 1. In this embodiment, TC4 titanium alloy is used as the raw material to fabricate a three-section nested hollow rod. Each rod section is 0.2m long and 4mm thick. Adjacent rods are connected by a snap-fit ​​limiting structure to achieve telescopic limitation and locking. A schematic diagram of the electrode's extended and retracted states in this embodiment is shown below. Figure 1 The rod body has uniformly spiral-shaped permeation micropores along the axial direction on the side wall. The micropore diameter is 0.2 mm and the micropore spacing is 6 cm. After the titanium alloy rod body is anodized, a dense TiO2 oxide film with a thickness of 5~8 μm is formed on the surface, which improves the corrosion resistance. A conical electrode head with a cone angle of 45° is welded to the bottom end of the lowest section of the rod body to facilitate insertion into soils of different hardness.

[0024] Prepare the slow-release ion assembly in advance by weighing chloride, bentonite, nano-titanium dioxide (particle size 20-50nm), and epoxy resin curing agent (polyamide 650 curing agent) in a mass ratio of 40:30:15:15. The chloride is a mixture of potassium chloride and sodium chloride in a 1:1 mass ratio. Add the above raw materials to a mixer and mix thoroughly. Then add an appropriate amount of water to adjust the consistency and cure at room temperature for 24 hours to form a columnar slow-release ion assembly. During construction, directly insert the pre-prepared ion assembly into the rod body.

[0025] Weigh graphite powder (100-200 mesh), sodium bentonite, and undisturbed soil from the exploration site at a mass ratio of 30:20:50, and mix them evenly to prepare a composite conductive medium. Separately, weigh glycerol and sodium carboxymethyl cellulose at a mass ratio of 2:1, mix and stir until completely dissolved to prepare a mixed moisturizing agent in advance. Mix the composite conductive medium and the mixed moisturizing agent at a mass ratio of 95:5, stir evenly, and set aside. The medium with this ratio has high conductivity, moisture retention, and soil compatibility, and its viscosity is moderate, which is convenient for layered compaction in the field.

[0026] Example 2. This embodiment uses the composite resistance-reducing electrode prepared in Example 1 to conduct field exploration at a geological hazard investigation site for detecting the thickness of the detachment layer in a debris flow gully in a mountainous area. The exploration site is located in the transition zone at the foot of the mountain. The specific construction steps are as follows (see the schematic diagram of the operation process). Figure 3 ): According to the exploration design requirements, the composite resistance-reducing electrode was adjusted to the target extension length of 0.5m, and each section of the rod was locked by a snap-fit ​​limiting structure. The integrity of the permeable micropores on the side wall of the rod was checked to ensure that there was no blockage or damage. At the same time, the prepared composite conductive medium was stirred evenly and put into a sealed bag for later use to prevent moisture loss.

[0027] A small handheld drilling device was used to excavate a cylindrical hole with a diameter 2.5 cm larger than that of the composite resistance-reducing electrode and a depth of 0.3 m. After excavation, the surface soil and debris inside the hole were removed.

[0028] The pretreated composite resistance-reducing electrode is slowly and vertically inserted into the hole. The electrode position is adjusted to be centered, ensuring that a uniform filling gap is left between the electrode and the hole wall, and that there is no situation where one side is attached to the wall.

[0029] The spare composite conductive medium is evenly filled into the gap between the electrode and the hole wall. The construction is carried out by layer compaction, with each layer being 12cm thick. A small tamping rod is used to compact each layer to ensure that the filling is dense and without gaps.

[0030] 150 mL of saturated saline solution is slowly injected through the injection port at the top of the titanium alloy rod. The saturated saline solution fully wets the internal slow-release ion component through the permeation micropores, activating the conductive ion release function. A cross-sectional schematic diagram of the electrode in use in this embodiment is shown below. Figure 2 After the installation is completed, the electrode grounding resistance is tested using a Jiaopeng E60DN high-density electrical resistivity meter. Each test is repeated three times, and the average value is taken as the final result.

[0031] Comparative Example 1. (Routine Field Operations) Solid copper electrodes are used, with a diameter of 15mm and a length of 0.3m; the bottom of the electrode adopts a conventional conical head; the top of the electrode has a reserved wiring terminal for connecting to high-density electrical resistivity tomography instruments.

[0032] During construction, the electrodes are directly inserted into the soil, and an appropriate amount of salt water is poured onto the insertion site. If there are gaps between the electrodes and the borehole wall, they are filled directly with in-situ soil.

[0033] Comparative Example 2. Solid copper electrodes are used, with a diameter of 15mm and a length of 0.3m; the bottom of the electrode has a tapered head; and a wiring terminal is reserved at the top of the electrode.

[0034] During construction, after the hole is excavated, the electrode is placed in, and ordinary industrial-grade graphite powder (particle size 100~200 mesh) is directly filled into the gap between the electrode and the hole wall. An appropriate amount of salt water is poured at the electrode insertion point. There is no additional long-term sustained-release design.

[0035] Example of results. The three electrodes used in Example 1 and Comparative Examples 1 and 2 were used to conduct exploration at the same field exploration site, where the soil environment, temperature and humidity, and construction equipment were completely identical.

[0036] The initial grounding resistance of each group of electrodes was tested using a GEOPEN E60DN high-density electrical resistivity tomography (EDT) instrument, and the results are shown in Table 1. The initial grounding resistance of this invention is 1528Ω, which is 22% higher than that of Comparative Example 1 and 11% higher than that of Comparative Example 2. This demonstrates that the synergistic design of the composite conductive dielectric and electrode structure in this invention can significantly reduce the grounding resistance.

[0037] Table 1

[0038] During normal high-density electrical resistivity tomography (EDT) operation and at 4, 14, 24, and 48 hours after construction, the grounding resistance of each group of electrodes was tested, and the grounding resistance attenuation rate was calculated. The results are shown in Table 2. In this invention, the grounding resistance only increased slightly during the 48-hour test period; however, the grounding resistance of the two proportional pairs increased significantly over time, with 48-hour change rates reaching 31.68% and 26.97%, respectively. Conventional high-density EDT measurements typically require 48 hours for data acquisition. This demonstrates that the slow-release ion assembly of this invention can achieve continuous release of conductive ions. Combined with the moisturizing design of the composite conductive medium, it effectively solves the problem of easy attenuation of resistance reduction effect in existing technologies, achieving long-term stable resistance reduction.

[0039] Table 2

[0040] The electrodes of each embodiment and the electrode of Comparative Example 1 were placed in acidic soil (pH=4.5), alkaline soil (pH=8.5), and saline soil (salt content 1.2%), respectively, and immersed for 60 days. The weight loss rate of the electrodes was tested and calculated, and the results are shown in Table 3. In the corrosive environments of acid, alkali, and saline soil, the titanium alloy electrode of the present invention exhibited extremely low weight loss and no obvious surface corrosion, which is far superior to the traditional copper electrode. This proves that the present invention can significantly improve the corrosion resistance of the electrode and extend its service life.

[0041] Table 3

[0042] In summary, the composite resistance-reducing electrode and high-density electrical resistivity reduction method of the present invention, through the synergistic design of a titanium alloy telescopic hollow rod, a fixed-ratio long-lasting slow-release ion component, and a composite conductive medium, combined with a standardized construction process, can simultaneously achieve long-term stable resistance reduction, high environmental adaptability, convenient and efficient construction, strong corrosion resistance, and controllable cost. It completely solves the pain points of existing high-density electrical resistivity reduction technologies and is applicable to various soil environments such as silty clay, sandy soil, acidic and alkaline soil, and saline soil, as well as various high-density electrical resistivity exploration operations such as mineral resource exploration, urban underground space exploration, and hydrogeological surveys. It has extremely high engineering practical value and promotion value.

[0043] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite resistance-reducing electrode, characterized in that, It includes a multi-section nested hollow rod and a slow-release ion assembly; The rods are connected sequentially from top to bottom, and the extension and retraction of adjacent rods are achieved by a limiting device; the rods are made of titanium alloy, the outer surface of the rods is coated with a TiO2 film, and the sidewalls of the rods are provided with permeable micropores; the bottom of the lowest rod section is provided with a conical electrode head. The slow-release ion assembly is built into the hollow rod body; the slow-release ion assembly includes chloride, bentonite, nano titanium dioxide and curing agent in a mass ratio of 40:30:15:15; the chloride is a mixture of potassium chloride and sodium chloride in a mass ratio of 1:

1.

2. The composite resistance-reducing electrode according to claim 1, characterized in that, The permeation micropores are evenly distributed in a spiral shape along the axial direction of the rod, with a pore diameter of 0.1~0.5mm and a micropore spacing of 5~8cm.

3. The composite resistance-reducing electrode according to claim 1, characterized in that, The length of a single section of the rod is 0.2~0.3m, the total telescopic length ranges from 0.2 to 1m, and the wall thickness is 3~5mm.

4. The composite resistance-reducing electrode according to claim 1, characterized in that, The limiting device is a snap-on or threaded limiting structure.

5. A high-density electrical resistivity reduction method, characterized in that, The method of using the composite resistance-reducing electrode as described in any one of claims 1 to 4 includes the following steps: S1. Adjust the electrode to the target extension length according to the exploration requirements, and lock each section of the rod body through the limiting device; S2. Excavate a cylindrical hole at the target measuring point, and then insert the conical electrode head into the hole to make the electrode rod fully contact the soil. S3. Fill the gap between the electrode and the hole with a composite conductive medium made of graphite powder, bentonite and undisturbed soil. S4. After filling, inject saturated saline solution from the top of the telescopic electrode body, and then seal the top. S5. If the grounding resistance of the detection electrode does not meet the preset threshold, then inject saturated saline solution, add conductive medium, or adjust the hole depth and electrode extension length until the resistance reduction target is achieved.

6. The high-density electrical resistivity reduction method according to claim 5, characterized in that, The diameter of the cylindrical hole is 2-3 cm larger than the diameter of the composite resistance-reducing electrode, and the depth is shorter than the extension length of the composite resistance-reducing electrode.

7. The high-density electrical resistivity reduction method according to claim 5, characterized in that, The composite conductive medium is filled using a layered compaction method, with each layer having a compaction thickness of 10-15 cm and an overall compaction density ≥1.5 g / cm³. 3 .

8. The high-density electrical resistivity reduction method according to claim 5, characterized in that, The mass ratio of graphite powder, bentonite, and undisturbed soil in the composite conductive medium is 30:20:

50.

9. The high-density electrical resistivity reduction method according to claim 5, characterized in that, The composite conductive medium contains a mixed humectant of glycerol and sodium carboxymethyl cellulose, wherein the mass ratio of glycerol to sodium carboxymethyl cellulose is 2:

1.

10. The high-density electrical resistivity reduction method according to claim 9, characterized in that, The mass ratio of the mixed moisturizer to the composite conductive medium is 5:95.

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