Electrical prospecting electrode observation system and method suitable for desert landscape

Abstract

The invention discloses an electrical prospecting electrode observation system and method suitable for desert landscaps.The method comprises the steps that after electrode points are divided at the position of a preset survey line and a layout area is optimized, a pit body with a certain depth is excavated to avoid a high-resistance weathering layer of the earth surface, wetting treatment is conducted on the pit bottom and the pit wall, and an initial conductive interface is formed; a large-area metal sheet electrode is horizontally arranged in the center of the pit bottom, and a sufficient current conduction surface is provided; the integrity of a signal transmission path is guaranteed by connecting the insulated wire and reasonably leading out; clay or loam with the water content controlled to be 18%-22% is adopted for layer-by-layer backfilling, initial water replenishing is conducted after layer-by-layer compaction, and the equivalent resistance of a medium around an electrode is remarkably reduced; covering a moisturizing material, and standing for not less than 30 minutes, so that moisture fully permeates, and the electric field tends to be stable; dynamically supplementing water according to an environmental evaporation rule during observation, and maintaining a low-resistance state; and finally, accessing an acquisition system to complete potential reading, and evaluating multiplexing conditions after observation is finished.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of exploration, and particularly relates to an electrode observation system and method for electrical exploration suitable for desert landscape. BACKGROUND

[0002] When electrical exploration is carried out in arid regions such as deserts and Gobi, the surface medium is mainly composed of dry and loose sand and stone, and the resistivity is extremely high, which makes it difficult to establish a stable and low-resistance electrical connection between the measuring electrode and the ground. The traditional method usually uses steel drill or copper rod as electrode to directly punch into the sand layer, but due to the small contact area and the lack of free ions in dry sand, the current conduction ability is extremely weak, resulting in excessive grounding resistance, weak signal strength and severe potential reading fluctuation.

[0003] In order to improve the grounding condition, the existing technology usually increases the number of electrodes, deeply buries the electrodes or irrigates salt water, which can reduce the resistance to a certain extent, but still has the problems of low construction efficiency, short effect or negative impact on the ecological environment. Especially in long-term observation or multi-frequency measurement, the unstable interface between the electrode and the medium leads to poor data repeatability, which seriously affects the reliability of geological interpretation. SUMMARY

[0004] The purpose of the present application is to provide an electrode observation system and method for electrical exploration suitable for desert landscape, which changes the contact mode of the electrode and the desert stratum from "point-surface" contact to "surface-body" conduction, effectively solves the technical problem of grounding difficulty in arid environment, and greatly improves the signal quality and observation stability.

[0005] To achieve the above purpose, the present application adopts the following technical scheme: an electrode observation method for electrical exploration suitable for desert landscape, comprising the following steps: Divide the electrode layout points at equal intervals at the preset measurement line position, and check the surface conditions to determine the final layout position; dig a pit with a depth of 30 to 50 centimeters at each electrode layout point, and preliminarily wet the pit bottom and pit wall; horizontally place a metal sheet electrode in the center of the wet pit bottom, connect an insulating lead and fix the lead-out path; use wet soil with a water content of 18% to 22% for layered backfilling, lightly press each layer, then perform initial watering compensation, cover moisture-retaining materials and stand for not less than 30 minutes; monitor the environmental parameters during the standing period, supplement water according to the evaporation law, then connect a multi-channel acquisition unit, apply a constant current excitation and synchronously read the potential difference, evaluate the residual humidity of the pit after the observation, and decide the disposal method.

[0006] Preferably, the division of the electrode layout points comprises: Determine the measurement line direction and length according to the geological task, so that the measurement line is perpendicular to the target structure distribution direction; Mark the points along the survey line with high-precision GPS or total station at intervals of 5-50 meters; Mark the ground with wooden stakes, colored flags or waterproof labels, and record the coordinates of each point in the field log.

[0007] Preferably, the verification of ground conditions includes: On-site inspection of each marked point to observe the type of ground cover, slope and gravel accumulation; Preferably, the terrain is flat, without obvious mobile sand dunes, and the ground is relatively hard. If there are large stones or severe loose at the original location, fine-tune the point within ±2 meters, and update the coordinates of the fine-tuned point simultaneously.

[0008] Preferably, the excavation depth of 30-50 cm pits includes: Excavate a rectangular or circular pit with an extension of at least 10 cm outside the size of the metal sheet electrode; Control the pit depth to be between 30-50 cm, so that the pit can accommodate the electrode and leave a filling space; Separately place the surface dry sand and the lower slightly wet sand.

[0009] Preferably, the preliminary wetting of the pit bottom and walls includes: Use a portable water bag to evenly sprinkle 1.5-2.5 liters of clean water on the pit bottom and walls; After wetting, stand for 5 minutes to allow water to penetrate downward to form a shallow wet transition zone; Observe the stability of the pit, if there is local collapse, then trim and recompact the pit wall, and confirm the stability of the structure before covering the pit opening with a windproof cloth or plastic film.

[0010] Preferably, the horizontal placement of the metal sheet electrode in the center of the wetted pit bottom includes: Select 40 cm x 40 cm, 2-5 mm thick aluminum plate as the electrode material; Place the aluminum plate horizontally in the center of the wet pit, and ensure that the edges of the aluminum plate are approximately equal in distance from the pit wall to achieve central placement.

[0011] Preferably, the connection of the insulated wire and the fixing of the lead-out path includes: Take a copper core wire with a polyethylene insulation layer, and strip 1.5 cm of the insulation layer at one end; Connect it to the aluminum plate reserved hole position with stainless steel clamps or welding method, wrap the joint with multiple layers of waterproof insulation tape and heat shrink tube and heat shrink; The wire is led out obliquely along one side of the pit wall, and a rubber pad is laid at the edge of the pit opening for cushioning.

[0012] Preferably, the wet soil layer-by-layer backfilling includes: The clay or loam soil adjacent to the edge of the oasis or dry riverbed is selected as the backfill material; The water content of the soil is adjusted to 18% to 22%, and the criterion is that the soil can be held together by hand and scattered on the ground; The soil is poured into the pit in three to four layers, each layer being 10 to 15 cm thick, and slowly poured from the side of the electrode.

[0013] Preferably, the time-based water replenishment according to the evaporation law comprises: After each layer of wet soil is poured, it is lightly compacted with a palm or small rammer to remove air bubbles; After backfilling, the water replenishment amount is estimated according to the pit area, soil water absorption coefficient and water content difference; The calculated water amount is evenly sprinkled on the backfill soil surface, allowing it to naturally infiltrate, and then covered with a reed mat or cotton and linen blanket.

[0014] In another aspect, the present application proposes an electrode observation system for electrical prospecting in desert landscapes, comprising: A plurality of electrode units are arranged at equal intervals along the survey line, each electrode unit containing a metal sheet electrode buried in a 30 to 50 cm deep pit, the inner wall of the pit is moistened with clean water and forms a wet transition zone; The metal sheet electrode is an aluminum plate with a thickness of 2 to 5 mm, horizontally placed at the center of the pit bottom, and one corner is connected to an insulated lead wire with a double-sealed joint, the lead wire is led out obliquely along the pit wall and is provided with anti-pulling protection; The pit is backfilled with clay or loam soil with a water content of 18% to 22% in layers and compacted layer by layer, and the backfill soil surface is covered with a reed mat or cotton and linen blanket after initial watering compensation; The entire survey line is equipped with reference stakes and review points for unified spatial reference, meteorological observation devices and water replenishment devices are provided during observation, the electrode lead wire is connected to a multi-channel acquisition unit, and a complete observation array is formed.

[0015] The technical effects and advantages of the present application are as follows: The application forms an initial conductive interface by dividing electrode points at preset survey line positions, preferably arranging the area, digging a pit body of a certain depth to avoid the surface high resistance weathering layer, and carrying out wetting treatment on the pit bottom and pit wall; a large-area metal sheet electrode is horizontally placed at the center of the pit bottom to provide sufficient current conduction surface; the integrity of the signal transmission path is ensured by connecting the insulated wires and reasonably leading out; the equivalent resistance of the medium around the electrode is significantly reduced by using clay or soil with a water content of 18% to 22% for layered backfilling, and then carrying out initial water replenishment after layer-by-layer compaction; the moisture-retaining material is covered and left for not less than 30 minutes to make the water fully penetrate and the electric field tend to be stable; during the observation period, dynamic water replenishment is carried out according to the evaporation law of the environment to maintain the low resistance state; finally, the collection system is connected to complete the potential reading, and the reuse condition is evaluated after the observation is completed. The scheme fundamentally changes the contact mode of the electrode and the desert stratum, changes from "point-surface" contact to "surface-body" conduction, effectively solves the technical problem of grounding difficulty in arid environment, and greatly improves the signal quality and observation stability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The flowchart of the electrode observation method for the electrical exploration suitable for the desert landscape of the application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the application will be clearly and completely described with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. The specific embodiments described herein are only used to explain the application, and are not used to limit the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0018] The application provides an electrode observation method for electrical exploration suitable for a desert landscape, as shown in formula (I): Figure 1 The electrode observation method for electrical exploration suitable for the desert landscape of the application comprises the following steps: The electrode arrangement points are equally divided at the preset survey line positions, and the surface conditions are checked to determine the final arrangement positions; wherein the electrode arrangement points are divided as follows: the survey line direction and length are determined according to the geological task, so that the survey line is perpendicular to the target structure distribution direction; the point positions are marked along the survey line at an interval of 5-50 meters by using a high-precision GPS or a total station; the ground is marked by using wooden stakes, colored flags or waterproof labels, and the coordinates of each point position are recorded in the field log.

[0019] Further, the verification of the ground conditions includes: on-site investigation of each marker point, observation of the type of ground cover, slope and gravel accumulation; preferentially selecting areas with flat terrain, no obvious mobile sand dunes, and hard ground surface as the layout points; if there are large stones or serious loose at the original location, fine-tune the point within ±2 meters, and update the coordinate record of the fine-tuned point at the same time.

[0020] By dividing the electrode layout points equidistantly at the preset survey line position and combining with the on-site verification and optimization of the point position, the entire observation system has a unified spatial reference and good geometric regularity. The survey line direction is perpendicular to the target structure, which enhances the lateral resolution of underground anomalies and is beneficial to obtaining clear electrical boundary response. High-precision instrument marking and coordinate recording ensure the traceability of the electrode position, providing accurate spatial correspondence for later data processing. The ground marking uses wind-resistant materials, effectively preventing the loss of point position in the desert environment. Combined with on-site investigation, the ground conditions are screened to avoid construction in loose or unstable areas, improving the long-term stability of the pit structure. The fine-tuning mechanism improves the on-site adaptability while ensuring the overall layout accuracy, making each electrode point have good construction conditions and grounding potential, thereby laying a reliable physical foundation for subsequent construction of low-resistance paths.

[0021] Dig a pit with a depth of 30 to 50 centimeters at each electrode layout point, and perform preliminary wetting of the pit bottom and walls. The specific steps are as follows: Excavate a rectangular or circular pit with an extension of at least 10 centimeters outside the metal sheet electrode size; control the pit depth between 30 to 50 centimeters, so that the pit can accommodate the electrode and leave a filling space; separate the surface dry sand and the lower slightly wet sand. Use a portable water bag to evenly sprinkle 1.5 to 2.5 liters of water on the pit bottom and walls; after wetting, stand for 5 minutes to allow the water to penetrate downward to form a shallow wet transition zone; observe the stability of the pit, if there is local collapse, then trim and recompact the pit wall, and confirm the stability of the structure before temporarily covering the pit opening with a windproof cloth or plastic film.

[0022] By digging a certain depth of pit, the extremely dry and high-resistivity loose sand layer on the ground surface is effectively avoided, and the underlying relatively dense and high water potential original sand is used as the basic conductive layer. The pit size reserves sufficient space for the subsequent electrode arrangement and uniform wet soil wrapping, providing physical conditions to ensure the symmetric diffusion of current to the surrounding medium. Layered stacking of surface and lower sand is convenient for the rational use of materials with different physical properties during backfilling, reducing the formation of high-resistance interlayers. Preliminary wetting of the pit bottom and wall activates the weak conductive ability of the original sand, forming a continuous initial conductive interface, significantly reducing the contact barrier between the electrode and the original stratum. The standing infiltration process promotes water migration to the deep layer, building a stable wet transition zone, enhancing the electrical connection between the artificial improved layer and the natural stratum. Temporary covering measures effectively prevent sand and wind from entering, maintaining the cleanliness and humidity of the pit environment before electrode installation, ensuring the continuity of subsequent procedures in a controlled state, and improving the reliability and consistency of the overall grounding system.

[0023] The metal sheet electrode is placed horizontally in the center of the wet pit bottom, connected to the insulated wire and fixed to the lead-out path; the specific steps are as follows: Select 40 cm x 40 cm, 2-5 mm thick aluminum plate as electrode material; place the aluminum plate horizontally in the center of the wet pit bottom, and ensure that the edges around the aluminum plate are approximately equal in distance from the pit wall to achieve central arrangement. Take a polyethylene insulated copper core wire, strip 1.5 cm of the insulation from one end; connect it to the aluminum plate reserved hole position using a stainless steel clamp or welding method, wrap the joint with multiple layers of waterproof insulation tape and heat-shrinkable tube and heat shrink; the wire is led out obliquely along one side of the pit wall, and a rubber pad is laid at the edge of the pit opening to cushion.

[0024] Using a large area of metal sheet as electrode material significantly increases the contact area with the improved medium, making the current distribution more uniform, effectively reducing the current density per unit area, and reducing the polarization effect and contact resistance. Aluminum plate has good electrical conductivity and environmental adaptability, and the natural oxide film formed under desert dry conditions is stable and does not affect the overall conductivity. Its lightweight characteristics facilitate transportation and on-site operation. Horizontal central arrangement ensures that the electrode is in the center of the backfilled wet soil, avoiding distortion of the current field due to offset, ensuring the symmetry of current conduction and the geometric fidelity of measurement data. Wire connection uses a combination of mechanical clamping and sealing, not only achieving firm electrical connection between the electrode and the wire, but also preventing water from migrating outward or infiltrating from the outside through double insulation protection, preventing joint corrosion and electrical leakage. The oblique lead-out path combined with the cushion pad at the pit opening eliminates direct friction between the wire and sharp edges, reducing the risk of damage caused by wind and sand swings or external forces, ensuring the integrity and stability of the signal transmission channel over a long period of observation. The overall structural design takes into account both electrical performance and mechanical durability, providing key support for building a long-term reliable low-resistance grounding system.

[0025] The wet soil with water content of 18% to 22% is layered backfilled, and after light pressure, initial watering compensation is carried out, and moisture retaining material is covered and left for not less than 30 minutes; the specific steps include: selecting clay or loam near the edge of an oasis or a dried riverbed as the backfill material; adjusting the water content of the soil to 18% to 22%, with the criterion of hand holding into a ball and falling to the ground; pouring into the pit in three to four layers, each layer being 10 to 15 cm thick, and slowly pouring from one side of the electrode.

[0026] The fine-grained soil with moderate water content is used for backfilling, fully utilizing its high water holding capacity and low permeability characteristics, to build a stable artificial low-resistance medium body, significantly improving the current conduction environment between the electrode and the surrounding strata. The improved soil layer has high ion migration capacity, effectively bridging the electrical difference between the metal electrode and the high-resistance sand layer, forming a continuous and low-impedance current diffusion channel. The combination of layered backfilling and layer-by-layer light pressure makes the soil loose and ventilated while being moderately compacted, which not only eliminates the air voids in the wrapping layer, but also avoids excessive compaction that leads to pore closure and hinders water migration, thereby optimizing the connectivity of the conductive network. The slow pouring from one side of the electrode ensures that the wet soil is evenly distributed around the electrode, preventing electrode deviation or local suspension caused by unilateral impact, and ensuring the integrity and symmetry of the electrode-medium interface. The water content is controlled in the range of 18% to 22%, which is within the optimal water threshold range of soil electrical conductivity, which can maintain sufficient free ion concentration and prevent flow or settlement due to excessive wetness, ensuring the dual stability of the backfill body in physics and electricity. As the functional core of the electrode system, this artificial low-resistance body fundamentally solves the grounding difficulty problem in desert areas, providing reliable protection for the stable establishment of the subsequent electric field and accurate collection of potential signals.

[0027] During the standing period, environmental parameters are monitored, water is supplemented according to the evaporation law, then a multi-channel acquisition unit is connected, a constant current excitation is applied and the potential difference is read synchronously, after the observation is completed, the residual humidity of the pit body is evaluated and the disposal method is determined.

[0028] When watering, including: gently compacting with a palm or small rammer after each layer of wet soil is poured, to eliminate air bubbles; after backfilling, the water supplement amount is estimated according to the pit area, soil water absorption coefficient and water content difference; the calculated water amount is evenly sprinkled on the backfill soil surface, and then a reed mat or cotton linen blanket is covered.

[0029] The standing phase provides sufficient physical and electrochemical equilibrium time for the artificially constructed low-resistance medium, so that the water is uniformly distributed under the action of gravity and capillary force, the ions complete double-layer reconstruction on the surface of soil particles, and the electrochemical interface between the electrode and the medium tends to be stable, thereby significantly reducing the dynamic fluctuation of the contact impedance and providing repeatable initial conditions for subsequent measurement. Continuous monitoring of environmental parameters reveals key external factors affecting water retention, enabling dynamic adjustment of water replenishment strategies based on actual evaporation intensity, avoiding blind operation, and improving water resource utilization efficiency.

[0030] The water replenishment estimation method based on pit area, soil properties and water content difference makes water replenishment predictable and reasonable, preventing insufficient water replenishment from causing resistivity to rise again, and avoiding excessive watering from causing soil loss or structural damage, thereby maintaining the physical integrity and electrical continuity of the backfill layer. Uniform watering combined with natural infiltration process ensures smooth infiltration of water in the vertical direction, avoiding surface water accumulation or runoff, and making the water content of the entire wet soil layer consistent.

[0031] After covering the water-retaining material, the evaporation of the ground surface caused by sunlight and wind is significantly inhibited, the duration of the low-resistance state is prolonged, and the maintenance frequency is reduced. The entire standing and water replenishment process works together to keep the electrode system highly stable during observation, enhancing the signal-to-noise ratio and time consistency of potential readings, providing a reliable premise for multi-channel synchronous acquisition. After the observation is completed, the residual moisture is evaluated to provide an intuitive basis for determining whether the electrode point meets the reuse conditions, achieving efficient use of resources and effective control of operating costs.

[0032] On the other hand, the present application proposes an electrical exploration electrode observation system suitable for desert landscape, comprising: A plurality of electrode units are arranged at equal intervals along the survey line, each electrode unit containing a metal sheet electrode buried in a 30 to 50 cm deep pit, and the inner wall of the pit is wetted with clean water to form a wet transition zone; The metal sheet electrode is an aluminum plate with a thickness of 2 to 5 mm, horizontally placed at the center of the pit bottom, and one corner is connected to an insulated wire with a double-sealed joint. The wire is led out obliquely along the pit wall and is provided with anti-pulling protection; The pit is backfilled with clay or loam with a water content of 18% to 22% in layers and compacted layer by layer. The surface of the backfilled soil is covered with a reed mat or a cotton and linen blanket after initial watering compensation; The entire survey line is equipped with reference stakes and review points for unified spatial reference, and meteorological observation devices and water replenishment devices are provided during observation. The electrode wire is connected to a multi-channel acquisition unit to form a complete observation array.

[0033] The following will combine the above-mentioned electrical exploration electrode observation system suitable for desert landscape to explain the specific implementation steps of an electrical exploration electrode observation method suitable for desert landscape in detail: Step One: Line Planning and Electrode Positioning Before any field deployment, the orientation of the survey line and the spatial distribution of electrode positions should be determined. The survey line is the basic geometric framework of electrical prospecting, determining the direction and range of the subsurface electrical structure exploration. The electrode positions are the actual locations of current injection and potential measurement, and their positioning accuracy directly affects the spatial resolution and geometric fidelity of the final imaging results.

[0034] Step 1.1: Determine the direction and length of the survey line based on the geological task: According to the geological target served by this exploration, such as the identification of concealed structures, the positioning of aquifers, or the investigation of basement depth, the start and end points of the survey line and the overall orientation are preliminarily determined. For example, if the goal is to find out the extension of a north-west trending fault, the survey line should be perpendicular to the structure to obtain the best lateral resolution. The total length of the survey line is determined based on the estimated size of the target, usually covering a certain distance on both sides of the potential anomaly to ensure the completeness of the boundary response. This step provides a spatial reference for all subsequent ground operations and is the starting point of the entire operation process.

[0035] Step 1.2: Divide the electrode positions along the survey line at equal intervals: After determining the survey line path, use high-precision GPS equipment or total station to mark the positions of each electrode along the straight line at the pre-set interval. The point distance is set according to the type of electrical prospecting device used (such as Wenner, Schlumberger, dipole-dipole, etc.) and the required exploration depth, usually between 5 meters and 50 meters. The marking method can use wooden stakes, colored flags, or waterproof labels to ensure that they are not easily buried by wind and sand on loose sandy surfaces. The coordinates of each point are recorded in the field log as the basis for spatial coordinates in later data processing. This division process establishes the spatial framework of the electrode system, providing clear target positions for the next step of pit excavation.

[0036] Step 1.3: Check the surface conditions of electrode points and optimize the layout positions: Each marked electrode point is investigated in the field to observe the type of surface cover, slope, vegetation distribution, and whether there are gravel accumulations or evidence of shifting sand activity. Preferably, select areas with relatively flat terrain, no obvious mobile sand dunes, and hard ground surface as the final layout points. If there are large stones or severe loose sand at the original location, the point can be adjusted within a range of ±2 meters, but the coordinate record needs to be updated simultaneously. This checking process avoids the collapse or electrode displacement that may occur on unstable surfaces during construction, ensuring the long-term stability of the subsequent pit structure.

[0037] Step 1.4: Establish survey line reference stakes and review mechanism: Permanent or semi-permanent reference stakes are set up at both ends of the survey line and at key turning points in the middle, using metal poles or deeply buried wooden stakes with reflective markers to prevent the survey line from shifting due to wind erosion or human interference. At the same time, every 10 electrode points are set with a review point, using independent measurement methods to confirm the coordinates again, ensuring the linearity and consistency of the point distance of the entire survey line. This reference system provides a unified spatial reference for the subsequent continuous construction of multiple electrode points, ensuring that the entire observation array remains geometrically regular in space, laying the foundation for later multi-channel synchronous measurement.

[0038] Step two: electrode pit excavation and foundation treatment The core purpose of this step is to avoid the extremely dry and high-resistivity weathered sand layer on the ground surface, providing a physical space for the subsequent construction of a low-resistance environment. The size and depth of the pit directly affect the contact state between the electrode and the surrounding medium, and are the prerequisite for good grounding.

[0039] Step 2.1: Excavate the electrode pit according to the design parameters: According to the technical parameters set earlier, a rectangular or circular pit is excavated at each electrode point using a shovel or small excavator. The pit should be larger than the metal plate electrode to be laid, with a length or diameter of at least 10 cm beyond the electrode edge, and the depth should be controlled between 30 and 50 cm. For example, if the electrode size is 40 cm x 40 cm, the pit should be excavated to 50 cm x 50 cm, with a depth of 40 cm. This design ensures that there is enough space around the electrode to fill the improved soil and form a uniform wrapping layer. During the excavation process, the surface dry sand and the lower layer of slightly wet sand are placed separately for subsequent classification and treatment.

[0040] Step 2.2: Clean up loose particles on the pit wall and pit bottom: After the pit is formed, use your hands or a brush to remove the loose sand and small stones attached to the pit wall and pit bottom, ensuring that the inner wall is smooth and free of sharp protrusions. This prevents the metal electrode from being scratched or pierced during placement, and also reduces the gap between the electrode and the filling soil, which is beneficial for forming a dense contact after compaction. For local loose and collapsible pit walls, you can use your palm to press and reinforce them, and if necessary, lay a layer of thin non-woven fabric as a temporary wall, but it should not affect the final current conduction path.

[0041] Step 2.3: Preliminary wetting of the pit bottom and pit wall: Use a portable water bag to evenly sprinkle an appropriate amount of water on the bottom and walls of the pit. The water volume should be about 1.5 to 2.5 liters, adjusted according to the dryness of the sandy soil. The purpose of wetting is to activate the original sand soil's electrical conductivity potential in advance, changing it from a complete insulator to a weak conductor with certain ion migration ability. This pre-treatment process can effectively reduce the initial contact resistance and provide a good interface connection for the subsequent backfilling of wet soil. After wetting, wait for 5 minutes to allow the water to penetrate downward, forming a shallow wet transition zone that will serve as a buffer layer between the artificial low-resistance body and the original stratum.

[0042] Step 2.4: Evaluate the stability of the pit and make temporary protection: After wetting is complete, observe whether the pit has side wall collapse or bottom water accumulation. If local collapse is found, it should be immediately trimmed and compacted again; if the bottom seeps water too quickly, it indicates the presence of a coarse-grained layer below, which requires increasing the number of wetting to improve the overall water level. After confirming the stability of the pit structure, cover the pit opening with a windproof cloth or plastic film to prevent wind and sand from falling in. This protective measure continues the maintenance of the pit state in the previous step, ensuring that the pit environment is not disturbed by external factors before the electrode is laid out, maintaining a clean and wet state.

[0043] Step Three: Metal electrode layout and wire connection After completing the pit preparation, proceed to the main installation phase of the electrode system. This step involves placing the metal sheet electrodes and connecting the signal wires, which is the core link to achieve current conduction function. The selected conductor material and its installation method directly affect the electrochemical compatibility and long-term stability between the electrode and the improved medium.

[0044] Step 3.1: Select and inspect the metal sheet electrode: Select aluminum plates with a thickness of 2 to 5 millimeters as the main electrode material, with a size of 40 centimeters x 40 centimeters and a total area of 1600 square centimeters. Aluminum is an ideal conductor choice in desert environments due to its low density, good ductility, stable natural oxide film, and low cost. Before use, check whether the aluminum plate surface is flat, has no serious oxidation spots or mechanical damage. If there are minor stains, they can be wiped off with clean water and dried; if there are perforations or cracks, they should be replaced. The inspected and qualified electrodes are numbered and prepared for placement in the pit. This inspection procedure follows the design of the pit size in the previous process, ensuring that the electrode can be placed smoothly and have enough filling space.

[0045] Step 3.2: Place the metal electrode horizontally in the center of the pit bottom: Carefully place the approved aluminum plate horizontally in the center of the wetted pit bottom, avoiding tilting or one-sided contact. Place gently to prevent impact from causing the pit bottom to loosen or water to splash. The aluminum plate should be completely attached to the pit bottom, with the edges at approximately equal distances from the pit walls to ensure uniform thickness of the subsequent backfill soil layer. If the pit bottom is slightly uneven, gently press the aluminum plate with your hand to adapt to the terrain, but do not force it to bend. This central arrangement continues the design of the pit size reserved in Step 2.1, ensuring that the electrode is at the center of the improved medium, which is beneficial for the symmetrical diffusion of current to all directions.

[0046] Step 3.3: Connect the insulated wire and seal the joint: Take a copper core wire about 2 meters long with a polyethylene insulation layer, and strip about 1.5 centimeters of insulation from one end. Use a stainless steel clamp or welding method to securely connect it to the reserved hole in one corner of the aluminum plate. After the connection is complete, wrap the joint with waterproof insulation tape in multiple layers, then cover it with a heat shrink tube and heat it to shrink, forming a double-sealed structure. This sealing process prevents water from seeping in and causing corrosion of the aluminum plate, while also preventing the local concentration of grounding current at the joint. The other end of the wire is left long enough to be drawn out of the pit for subsequent connection to the measuring instrument. This connection method relies on the stable placement of the aluminum plate in the previous step to ensure that the electrode position does not move during the joint operation.

[0047] Step 3.4: Fix the wire exit path and protect against pulling: Draw the connected wire along the side of the pit wall upward, avoiding direct crossing over the surface of the aluminum plate. Lay a small section of rubber mat or hardboard at the edge of the pit opening as a support and buffer for the wire, preventing sand and stone from damaging the outer skin. After the wire is drawn out of the soil, lay it along the predetermined line to the instrument, and at regular intervals along the way, use sandbags or stones to press it down to prevent wind drag. The exit section should be as straight as possible to reduce bending. This protection measure continues the requirement for joint sealing in the previous step, ensuring that the entire transmission path from the electrode to the instrument is complete and reliable, and is not damaged by external forces.

[0048] Step Four: Wet Soil Backfill and Initial Compaction After the electrode and wire installation is complete, the key stage of medium improvement begins - wet soil backfill. This step replaces high-resistivity sand soil with low-resistivity soil and combines water regulation to create an artificial low-resistivity environment. The quality of the backfill soil and the construction quality directly determine the overall electrical conductivity of the electrode.

[0049] Step 4.1: Prepare and transport the improved wet soil: Clay or loam soil taken from the vicinity of the oasis edge or dry riverbed is chosen as the backfill material. Its natural particles are finer, with strong water-holding capacity and far superior electrical conductivity to pure sand. The soil is transported to the vicinity of the test line and concentrated in piles. A sprayer or manual watering is used to adjust the moisture content to between 18% and 22%. The criteria for judging are: hold in the palm of the hand, fall to the ground and scatter. About 150 to 200 liters of water per cubic meter of wet soil is needed, with the specific amount adjusted according to soil differences. This moisture content range is based on extensive field practice, which can ensure smooth ion migration and will not cause excessive wetness to affect the structural stability due to strong fluidity. This preparation process provides a medium foundation that meets the electrical requirements for subsequent backfilling, extending the design of the space reservation for the pit body in the previous process.

[0050] Step 4.2: Pour wet soil in layers and wrap around the electrode: The adjusted wet soil is poured into the pit in three to four layers, each about 10 to 15 cm thick. Start from one side of the electrode, pour slowly and ensure that the wet soil evenly surrounds the aluminum plate on all sides, avoiding unilateral accumulation that may cause deviation. The first layer covers the bottom and lower side of the aluminum plate, the second layer fills the middle section, and the third layer completes the top coverage. After each pouring, pause the operation and observe whether there are voids or empty spaces. This layering method ensures that the electrode is fully surrounded by wet soil, forming a continuous conductive interface and meeting the requirement of centering the electrode in step 3.2, preventing poor contact caused by uneven filling.

[0051] Step 4.3: Lightly press each layer to remove air and enhance compaction: After pouring each layer of wet soil, use your palms or a small tamper to lightly compact it, with moderate force to avoid damaging the soil structure. The purpose of compaction is to remove air bubbles between soil particles, reducing porosity and thus improving the overall electrical conductivity of the soil. Air is a good insulator, and its presence will significantly increase the equivalent resistance of the medium. By manually compacting, the wet soil forms a tighter physical contact with the aluminum plate surface, reducing the electrical resistance of the contact interface. At the same time, moderate compaction also enhances the mechanical strength of the backfill, preventing subsidence and void formation due to self-weight in the later stage. This operation continues the strategy of layering and filling in the previous step, ensuring that each layer is compacted to the desired density.

[0052] Step 4.4: Calculate and apply the initial watering compensation formula: After completing the backfill and initial compaction, immediate full watering is required to compensate for water loss during construction and further reduce the overall resistivity. The amount of water can be estimated by the following empirical formula: ; Where: : required water amount (unit: liters); : Soil water absorption coefficient, for clay loam, take 0.8~1.2 L / (m²·%); : Pit horizontal projection area (unit: m²); : Target water content, set to 20%; : Current water content measured or estimated after backfilling, set to 16%.

[0053] For example, for a pit of 0.5 m × 0.5 m, , take , then: ; This formula reflects the quantitative relationship between water replenishment and soil water holding capacity. Its principle lies in maintaining the concentration and migration rate of free ions in the medium, thereby ensuring the continuity of current conduction. In practical operation, the calculated water amount is evenly sprinkled on the surface of the backfill soil, allowing it to naturally infiltrate. This water replenishment process complements the previous compaction operation, together completing the final shaping of the artificial low-resistance body and creating conditions for the next stage of electric field stabilization.

[0054] Step five: Electric field stabilization and humidity balance period After completing the wet soil backfilling and initial water replenishment, the electrode system has not yet reached the optimal working state. At this time, water is in the process of diffusing from the surface to the deep layer, and ions are redistributing among soil particles. The electrochemical properties of the electrode-medium interface are not yet stable. Therefore, a static time must be set to allow the entire system to reach dynamic equilibrium, ensuring the consistency and repeatability of potential response in subsequent measurement processes.

[0055] Step 5.1: Cover with moisture-retaining material to reduce evaporation loss: Immediately after the backfilling operation is completed, a layer of water-retaining and breathable natural material such as reed mat, coconut palm mat, or cotton and linen blanket is laid on the surface of the pit opening. These materials have good capillary action and sun-shading properties, effectively slowing down the evaporation rate of soil moisture. When laying, the entire backfill area should be completely covered, and the edges should be pressed down with small stones or sandbags to prevent being blown up by the wind. This cover layer not only continues the attention to water regulation in the previous process, but also builds a microclimate barrier in the open environment, providing continuous humidity support for the internal wet soil and avoiding the rise of resistivity due to rapid surface water loss.

[0056] Step 5.2: Set the electric field steady-state waiting period: According to the field temperature, wind speed and solar intensity, determine the reasonable electric field stable waiting time. Generally, this period should not be less than 30 minutes. During this period, any personnel are prohibited from walking near the electrode point or carrying out other construction activities, so as to avoid disturbing the underground electric field distribution. The essence of waiting is to let the current channel fully establish between the electrode and the surrounding medium, so that the free charge completes the reconstruction of the double layer between the aluminum plate surface and the wet soil particles. This process is similar to the charging stage of a capacitor, and only when the interface charge distribution tends to be uniform can the smooth output of potential reading in subsequent measurement be ensured. This waiting period is a necessary preparation for the activation of the function of the artificial low resistance body, which is the physical change process after watering in step 4.4.

[0057] Step 5.3: Estimate the decay trend of medium resistivity over time: During the standing process, the resistance evolution direction of the grounding system can be predicted by empirical rules. The soil resistivity is closely related to its water content and pore connectivity, which can be described by the following relationship: ; Where: : the equivalent resistivity at time (unit: Ω·m); : initial resistivity at the beginning of backfilling; : decay coefficient, affected by soil type, temperature and ventilation conditions, about for clay soil in desert environment; : standing time (unit: minutes).

[0058] This exponential decay model reflects the process of gradually improving the medium's conductivity with water penetration and ion activation. For example, if , after 30 minutes, the resistivity will drop to about 40% of the initial value. This estimate is not for real-time measurement, but to provide a theoretical basis for operators to understand why a long enough stabilization period is needed. It continues the explanation of the electric field reconstruction mechanism in the previous step, further illustrating the important role of time in grounding quality.

[0059] Step 5.4: Establish a multi-point synchronous standing coordination mechanism: Since a survey line usually contains dozens of electrode points, the completion time of each point is different. To ensure that all electrodes enter the observation stage in the same state, a unified static start and end rule needs to be established. Taking the last electrode to complete backfilling as the benchmark, the "virtual start time" of the remaining electrodes is set by back calculation, that is, the earlier completed electrodes enter the waiting state in advance. For example, if a certain point is 20 minutes earlier than the last point, its actual waiting time is 50 minutes, but the effective stable period is still calculated as 30 minutes. This coordination ensures that the electrode system on the entire survey line reaches a stable state synchronously, and the analysis of time dependence in the previous formula makes the data acquisition of the entire array have a consistent time reference.

[0060] Step six: environmental monitoring and dynamic water replenishment maintenance After entering the formal observation stage, external climate conditions will continue to affect the humidity around the electrodes. Especially under the action of strong sunlight and dry air flow, the water in the backfilling soil will continue to migrate to the atmosphere, causing the resistivity to slowly rise. Therefore, a set of continuous environmental monitoring and water replenishment mechanism must be established to maintain the long-term effectiveness of the artificial low resistance body.

[0061] Step 6.1: Install a simple weather observation device: A small weather station is set up in the middle of the survey line or a representative location, equipped with basic sensors: a dry and wet bulb thermometer for measuring air temperature and humidity, an anemometer for recording wind speed, and a transparent rain gauge for observing precipitation. These devices do not require complex power supply and can meet the needs of mechanical or passive sensing design. Through hourly manual readings, the main environmental parameters affecting water evaporation are mastered. This arrangement continues the analysis of the relationship between time and resistance in the previous process, and includes macro climate factors in the management category, providing an objective basis for subsequent water replenishment decisions.

[0062] Step 6.2: Define the reference value of daily average evaporation per unit area: Combined with local climate data and short-term measured data, an average daily evaporation rate model suitable for the current season is established. For bare soil in desert areas, the daily average evaporation can be approximately expressed as: ; Where: : Daily evaporation of unit area (mm / d); : Saturated water vapor pressure (related to surface temperature); : Actual water vapor pressure (calculated from relative humidity); : Average wind speed at 2 meters above the ground (m / s); , : empirical coefficients, 0.18 and 0.25 respectively under typical conditions in the western margin of the Qaidam Basin.

[0063] For example, when the daily maximum air temperature is 35℃ ( ), the relative humidity is 15% ( ), and the wind speed is 3 m / s, ; Converting to a single electrode pit (area 0.25 m²), the daily water loss is about 0.4 liters. This calculation is not used for automatic control, but to help the operator estimate the order of magnitude of water replenishment, which takes into account the prediction logic of the resistance decay in step 5.3, reflecting the long-term impact of environmental variables on system performance.

[0064] Step 6.3: Develop a time-based water replenishment plan: Based on the above evaporation estimates, develop a regular water replenishment plan. It is generally recommended to complete the first water replenishment before 9 am each day, with a replenishment amount of 60% to 80% of the daily loss, i.e. about 0.25 to 0.3 liters / pit; a small amount of additional spray can be added during the afternoon high-temperature period (13:00-15:00) as needed; and before closing work in the evening, to maintain slow infiltration at night. Use portable spray bottles or drip irrigation bags for water replenishment to avoid surface loss caused by large water flushing. This plan continues the understanding of the evaporation pattern in the previous step, converting theoretical estimates into executable operating procedures to ensure that the water supply rhythm matches the consumption rhythm.

[0065] Step 6.4: Implement round-trip inspection and abnormal handling: Arrange for a dedicated person to inspect along the survey line, focusing on observing whether the coverings at each electrode point have shifted, whether the surface soil has cracked, and whether the wires have come loose. If local dry shrinkage cracks are found, the surface layer should be scraped and a small amount of water should be added; if the coverings are damaged, they should be replaced immediately. At the same time, record the time and amount of water replenishment each time to form an operation log. This inspection system incorporates all the previous maintenance measures and forms a closed-loop feedback system to ensure that each electrode is in good working condition throughout the observation period.

[0066] Step Seven: Signal acquisition and potential reading When all electrodes have completed stabilization and entered the maintenance state, the measuring instrument can be started, and the acquisition of potential data can be carried out. The core task of this stage is to accurately obtain the potential difference between different electrode combinations under the set current excitation, providing raw information for subsequent inversion of underground structures.

[0067] Step 7.1: Connect the multi-channel potential acquisition unit: The pre-laid electrode wires are sequentially connected to the input ports of the multi-channel voltage recorder, arranged in numerical order to avoid misconnection. The instrument itself is placed in a cool place and protected by a sunshade to prevent high temperature from affecting the stability of the internal circuit. Each channel is equipped with a high input impedance amplifier (≥10 GΩ) to minimize the impact on the measured potential. This connection process continues the design of the wire lead-out and protection in the previous process, ensuring the integrity of the signal path from the underground electrode to the front end of the instrument, laying a hardware foundation for high-precision measurement.

[0068] Step 7.2: Apply a constant current excitation source: Select a pair of remote electrodes as the power supply electrodes and connect them to a direct current or low-frequency alternating current source. The output current size is set according to the target depth and the background resistivity of the formation, typically between 100 mA and 2 A. The current waveform should be a square wave or a pseudo-random sequence to facilitate the filtering of natural interference signals later. The power supply duration is synchronized with the sampling period, usually switching polarity every 10 seconds to eliminate the drift error caused by electrode polarization. This excitation method takes advantage of the low grounding resistance of the electrode system, allowing sufficient current to be injected even in high-resistance backgrounds, enhancing signal penetration.

[0069] Step 7.3: Synchronously read the potential difference between multiple measuring electrodes: While the current is being injected, a multi-channel recorder is used to synchronously collect the potential difference between non-powered electrodes. For example, in a Wenner device, the electrodes are arranged in the order of , and the voltage between and is measured. All readings are completed under the control of the same clock, ensuring time consistency. Each reading retains an average value of at least 3 cycles to weaken random noise. This synchronous acquisition mechanism continues the geometric regularity of the overall measurement line layout, allowing responses at different positions to be compared in a unified time-space framework.

[0070] Step 7.4: Apply the apparent resistivity conversion formula for preliminary calculation: According to the measured power supply current and potential difference , combined with the electrode spacing, the apparent resistivity of the point can be calculated, with the expression: ; where is the device coefficient, which depends on the electrode arrangement. Taking the Wenner four-pole method as an example, is the distance between adjacent electrodes. If , then . Assuming that is measured, then: ; This formula is the basis of electrical interpretation, which converts the original voltage and current values into physical quantities reflecting the properties of the underground medium. This calculation process takes into account the optimization of current conduction ability in the previous steps, and only when the grounding is good and the signal is clear, the resulting apparent resistivity has geological significance.

[0071] Step Eight: Recovery and Reuse Evaluation after Observation After a round of measurement, the electrode system needs to be properly handled. Some electrodes may need to be kept for a long time for repeated observations, and others need to be removed to restore the landscape. This stage not only ensures the safety of equipment, but also takes into account environmental protection and resource conservation.

[0072] Step 8.1: Sequentially disconnect instrument connections and store wires: First, turn off the power, disconnect the recorder and wire interface one by one, and check for signs of corrosion or looseness. Wind the wire into a circle according to the number, and put it into a special storage box to prevent entanglement and knotting. This operation continues the attention to wire protection in the early stage, prolongs its service life, and creates conditions for subsequent measurement lines or project reuse.

[0073] Step 8.2: Evaluate the residual moisture and structural integrity of the electrode pit: Open the cover and observe the color and texture of the backfill soil surface. If it is still dark brown and feels moist, it indicates that the water remains good, and the electrode can be reused; if it has turned white and cracked, it needs to be re-wetted before it can be used again. At the same time, check for signs of collapse or animal disturbance. This evaluation takes into account the data accumulated during the entire maintenance period to determine whether the point has reuse value and avoid blind repetition of construction.

[0074] Step 8.3: Decide on the electrode disposal method and perform the corresponding operation: For temporary measurement lines, carefully dig out the aluminum plate, clean the attached soil, and recycle it; wet soil is flattened in place, covered with sand on the surface, and the original landscape is restored; for long-term monitoring points, the electrode is kept in place, only the cover layer is reinforced and a permanent marker post is set up. This continues the environmental design concept, saving resources and reducing ecological disturbance.

[0075] Step 8.4: Organize and archive the entire process operation log for reference: All records of this operation - including point coordinates, construction time, water consumption, weather data, maintenance records, measurement results, etc. - are compiled into a book, clearly indicating the responsible person and time node for each link. This document not only provides a traceable basis for this exploration, but also provides practical reference for future work in similar areas, taking into account the whole process management idea from planning to completion, forming a complete operation loop.

[0076] The whole scheme of the embodiment is based on the combination of material characteristics and natural laws, and successfully overcomes the electrical conduction problem under extreme drought conditions by artificially intervening in the local environment, thereby providing a feasible technical path for geophysical investigation in similar areas.

[0077] Finally, it should be noted that the above only for the preferred embodiments of the present application, and is not intended to limit the present application, although the foregoing detailed description of the application has been made, for those skilled in the art, it still can be modified, or the equivalent replacement of some technical features, as recorded in the foregoing embodiments of the technical solutions, within the spirit and principles of the present application, any modification, equivalent replacement, improvement, etc., should be included within the scope of the present application.

Claims

1. A method for electrical exploration electrode observation suitable for desert landscapes, characterized in that, Includes the following steps: Electrode placement points are divided at equal intervals at the pre-set survey line location, and the ground conditions are checked to determine the final placement location; Excavate a pit to a depth of 30 to 50 centimeters at each electrode placement point, and pre-wet the bottom and walls of the pit. Place the thin metal plate electrode horizontally into the center of the wetted pit bottom, connect the insulated wire and fix the lead-out path; Backfill with moist soil with a moisture content of 18% to 22% in layers, lightly press each layer down, and then water initially to compensate. Cover with moisture-retaining material and let stand for at least 30 minutes. During the settling period, environmental parameters are monitored, water is replenished in stages according to the evaporation pattern, and then connected to a multi-channel acquisition unit. A constant current excitation is applied and the potential difference is read synchronously. After the observation is completed, the residual humidity of the pit is assessed and the disposal method is determined.

2. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 1, characterized in that: The electrode placement points include: The direction and length of the survey line are determined based on the geological task, so that the survey line is perpendicular to the direction of the target structure. Mark points along the survey line using a high-precision GPS or total station at intervals of 5 to 50 meters; Use wooden stakes, colored flags, or waterproof labels to mark the ground, and record the coordinates of each point in the field log.

3. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 2, characterized in that: The verification of surface conditions includes: Conduct on-site surveys of each marked point to observe the type of surface cover, slope, and gravel accumulation. Priority should be given to selecting areas with flat terrain, no obvious moving sand dunes, and relatively hard ground as deployment sites; If there are large rocks or severe looseness at the original location, the location is fine-tuned within ±2 meters, and the coordinate record of the fine-tuned location is updated synchronously.

4. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 1, characterized in that: The pit with an excavation depth of 30 to 50 centimeters includes: Excavate a rectangular or circular pit at least 10 cm outward from the size of the metal sheet electrode. The pit depth is controlled between 30 and 50 centimeters, so that the pit can accommodate the electrodes and leave room for filling. Place the dry surface sand separately from the slightly moist lower layer of sand.

5. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 4, characterized in that: The preliminary wetting of the pit bottom and pit walls includes: Use a portable water bag to evenly sprinkle 1.5 to 2.5 liters of clean water onto the bottom and four walls of the pit; After wetting, let it stand for 5 minutes to allow the water to seep downwards and form a shallow moist transition zone; Observe the stability of the pit. If a local collapse occurs, repair and recompact the pit walls. After confirming that the structure is stable, temporarily cover the pit opening with windproof cloth or plastic film.

6. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 1, characterized in that: The step of horizontally placing the thin metal plate electrode into the center of the wetted pit includes: Aluminum plates measuring 40 cm × 40 cm and with a thickness of 2 to 5 mm were selected as electrode materials; Place the aluminum plate horizontally in the center of the wetting pit, ensuring that the distance from the four edges of the aluminum plate to the pit wall is approximately equal, thus achieving a centered arrangement.

7. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 6, characterized in that: The connection of the insulated wire and the fixing of the lead-out path include: Take a copper core wire with polyethylene insulation and strip 1.5 cm of insulation from one end; Connect it to the pre-drilled hole in the aluminum plate using stainless steel clamps or welding. Wrap the joint with multiple layers of waterproof insulating tape and heat shrink tubing to shrink it. The conductor is led out diagonally upward along one side of the pit wall, and a rubber pad is laid at the edge of the pit opening for cushioning.

8. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 1, characterized in that: The layered backfilling of the wet soil includes: Clay or loam soil near the edge of the oasis or a dry riverbed should be selected as backfill material. Adjust the soil moisture content to 18% to 22%, using the criterion that it can be formed into a ball when squeezed in the hand but crumbles when dropped. Pour the mixture into the pit in three to four layers, each layer being 10 to 15 centimeters thick, slowly pouring it from one side of the electrode.

9. The electrical resistivity tomography electrode observation method suitable for desert landscapes according to claim 8, characterized in that: The method of replenishing water in stages according to the evaporation pattern includes: After each layer of wet soil is poured, gently compact it with your palm or a small tamper to remove air bubbles; After backfilling is completed, the amount of water to be replenished is estimated based on the pit area, soil water absorption coefficient, and moisture content difference. Sprinkle the calculated amount of water evenly on the surface of the backfill soil and let it seep in naturally, then cover it with reed mats or cotton and linen blankets.

10. An electrical resistivity tomography electrode observation system suitable for desert landscapes for implementing the method as described in any one of claims 1-9, characterized in that, include: Multiple electrode units are arranged at equal intervals along the survey line. Each electrode unit contains a thin metal plate electrode buried in a pit 30 to 50 centimeters deep. The inner wall of the pit is wetted with clean water to form a wet transition zone. The metal plate electrode is an aluminum plate with a thickness of 2 to 5 mm. It is placed horizontally in the center of the pit bottom. One corner of it is connected to an insulated wire with a double-sealed joint. The wire is led out obliquely upward along the pit wall and is provided with anti-pull protection. The pit is backfilled in layers with clay or loam soil with a moisture content of 18% to 22% and compacted layer by layer. After initial watering compensation, the surface of the backfill soil is covered with reed mats or cotton and linen blankets. The entire survey line is equipped with reference stakes and check points for unified spatial reference. During the observation period, meteorological observation devices and water replenishment devices are installed. Electrode wires are connected to multi-channel acquisition units to form a complete observation array.

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