Soil moisture monitor with modified bentonite seal

Abstract

The application discloses a soil moisture content monitor containing modified bentonite sealing, and belongs to the technical field of soil moisture content monitoring, and comprises a shell and a probe body arranged in the shell, a plurality of metal electrodes are arranged on the probe body, and a flow guide structure extending in a spiral shape is arranged on the outer wall of the shell; the flow guide structure comprises a plurality of flow guide flanges, grooves are formed in the side walls of the plurality of flow guide flanges, liquid inlets are formed in the top surfaces of the plurality of flow guide flanges and are communicated with the grooves, and modified bentonite particles are sealed and filled in the grooves. The application can reduce disturbance to the undisturbed soil structure around the probe body, reduce data deviation, omit the operation step of backfilling soil, save time and effort, improve installation efficiency, ensure the use reliability of long-term monitoring, and improve the accuracy of monitoring results through the flow guide structure formed on the outer wall of the shell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil moisture monitoring, and particularly relates to a soil moisture monitor with a modified bentonite plugging. BACKGROUND

[0002] Soil moisture is a key parameter in the fields of agricultural irrigation, hydrological monitoring, geological disaster warning, civil engineering, etc. Real-time and accurate monitoring of soil moisture is of great significance for efficient use of water resources and slope stability assessment. At present, the mainstream soil moisture monitoring technology is based on the measurement principle of electromagnetic waves, such as time domain reflectometry and frequency domain reflectometry. Such a monitor usually includes a probe, and a plurality of metal electrodes are arranged on the probe. By detecting the propagation characteristics of electromagnetic waves in the probe, the dielectric constant of the surrounding soil is inversely calculated, and then the soil volume moisture content is calculated.

[0003] In the prior art, the installation method of such a soil moisture monitor usually includes the following steps: first, a hole with the same diameter as the probe is drilled at the measured position, then the probe is placed in the drilled hole, and finally the excavated soil is backfilled and tamped to complete the installation of the monitor probe. However, as shown in the figure, this traditional installation method has some obvious technical defects: Figure 1

[0004] First, measurement errors are easily introduced during installation. Drilling and backfilling inevitably disturb the undisturbed soil structure around the probe, resulting in differences in porosity, density and structure between the backfilled area and the surrounding undisturbed soil, thus easily forming an installation disturbance zone. Especially when it rains, water penetrates into the backfilled area, changing the hydraulic characteristics of the backfilled area, and thus the probe actually measures the moisture content of the backfilled area during use, rather than the true undisturbed soil moisture content, which can cause data deviation.

[0005] Second, a preferential flow path for water is easily formed. Even after careful backfilling, the compaction and structure of the backfilled material are difficult to match the original soil. When it rains or irrigates, water will tend to quickly infiltrate along the backfilled area with less resistance, thus easily forming a continuous high-moisture "water sheath" on the outer wall surface of the probe, which makes the actual moisture content measured by the probe higher, and the measured result only reflects the moisture content change of the backfilled area soil, rather than the true and average moisture content of the surrounding soil, thus reducing the accuracy of the measurement.

[0006] ​Third, the installation is complex and the stability is insufficient. The traditional drilling and backfilling process is tedious, time-consuming and labor-intensive, and requires high technical requirements for installation personnel. The backfilling quality directly affects the measurement results. In addition, relying only on the fixed method of backfilling soil compaction, the soil is prone to settlement or loosening under complex and variable environmental factors, such as dry-wet cycles of sunny and rainy days, freeze-thaw cycles of hot weather and frost weather, etc. This can cause the probe to tilt or displace, thereby further introducing measurement errors in long-term monitoring, and the reliability is poor.

[0007] In view of the above defects, there are also corresponding improvement measures in the prior art, for example, a soil moisture content sensor burying device provided in the invention patent with publication number CN102235001B. The device can ensure that the moisture content sensor is vertically inserted into the soil body, thereby reducing the disturbance to the original soil structure, and can ensure the accuracy of the moisture content test results of the soil moisture content sensor. However, the device still needs to backfill the drilling soil and perform layered compaction after the probe is installed in place, and also needs to use bentonite or cement mortar for sealing. The overall operation steps are complex and tedious, not only requiring high labor intensity, but also increasing the installation cost and reducing the installation efficiency. Therefore, this improvement scheme does not fundamentally simplify the installation process or eliminate the errors caused by backfilling.

[0008] In addition, it is worth noting that even if the prior art attempts to optimize the installation method to reduce disturbance or simplify the process, there is still a key problem that has been ignored for a long time: in the use scenarios of forest ecological restoration, organic agriculture, and other underground organisms such as earthworms, termites, and jumping insects, biological excavation behavior can form a large number of biological pores in the soil around the monitor. These pores not only destroy the original soil's hydraulic conductivity channel, but also become a new preferential flow path for water. Especially during rainfall or irrigation, water will quickly seep along these pores to the shell or metal electrode, but existing monitors can only intercept surface infiltration along the outer wall of the shell, such as the spiral blade with publication number US10765073B2, and cannot effectively block the lateral seepage in the biological pores. At the same time, although there are attempts to use bentonite for sealing in the prior art, such as the backfilling sealing of CN102235001B, this type of sealing method only targets the drilling gap during installation and is a one-time static sealing method. It cannot be used to block new pores continuously generated after the installation is completed due to biological activity, resulting in water seeping into the electrode periphery along the new pores during subsequent use, causing local moisture content to abnormally increase, thereby further expanding the measurement deviation, and the actual measurement deviation can reach ±3%-4%, seriously affecting the accuracy and reliability of long-term monitoring.

[0009] Therefore, it is urgent to design an innovative soil moisture content monitor which can solve the error problem introduced by the probe in the embedding process from the mechanical structure, and can be suitable for the new pores continuously generated due to biological activities after the embedding is completed, and realize convenient, reliable installation and long-term stable accurate measurement. SUMMARY

[0010] The main purpose of the present application is to overcome the defects of the prior art, and provide an intelligent soil moisture content monitor which can solve the error problem introduced by the probe in the embedding process from the mechanical structure, and can be suitable for the new pores continuously generated due to biological activities after the embedding is completed, and realize convenient, reliable installation and long-term stable accurate measurement.

[0011] To achieve the above purpose, the present application provides a soil moisture content monitor with modified bentonite plugging, which comprises a shell and a probe body arranged in the shell, a plurality of metal electrodes are arranged on the probe body, a flow guide structure extending in a spiral shape is arranged on the outer wall of the shell, the flow guide structure is used to intercept the water infiltrating along the outer wall of the shell and guide the water to diffuse along the radial direction of the shell to move away from the metal electrodes; the flow guide structure comprises a plurality of flow guide flanges, the plurality of flow guide flanges all extend away from the shell, the plurality of flow guide flanges are all located above the metal electrodes to intercept the water on the outer wall of the shell, grooves are formed in the side walls of the plurality of flow guide flanges, and liquid inlets are formed in the top surfaces of the plurality of flow guide flanges and communicate with the grooves, and modified bentonite particles are sealed and filled in the grooves.

[0012] Preferably, the top surface of any flow guide flange is formed with a slope, the slope is arranged inclinedly from the outer wall of the shell to the metal electrodes along the radial direction of the shell, and the liquid inlet is located at the bottom of the slope.

[0013] Preferably, a handle and a bottom cover are detachably mounted on the top and bottom of the shell respectively, a frustum is formed on the bottom surface of the bottom cover, and a positioning groove for clamping the probe body is formed on the top surface of the bottom cover.

[0014] Preferably, an end cover is arranged on the top of the probe body, the end cover is detachably connected with the shell, and the end cover is arranged inclinedly from top to bottom along the radial direction of the shell.

[0015] Preferably, the plurality of metal electrodes are uniformly and spacedly arranged along the extension direction of the probe body.

[0016] Preferably, the modified bentonite particles are composed of the following raw materials in parts by weight: 82-85 parts of sodium-based bentonite, 2-2.5 parts of silane coupling agent, 11-14 parts of hollow glass microbeads, and 1.5-2 parts of sodium carboxymethyl cellulose.

[0017] Preferably, the modified bentonite particles have a water absorption expansion rate of 320%-350% in a distilled water environment for 24 hours, and a compressive strength of ≥4 MPa.

[0018] Preferably, the modified bentonite particles are irregularly spherical, with a particle size distribution range of 0.5mm-1mm, wherein the proportion of particles with a particle size of 0.7mm-0.9mm is ≥70%; the specific surface area of the modified bentonite particles is 35m² / g-40m² / g, and the modified bentonite particles have micropores of 1μm-3μm on the surface, which are used for rapid adsorption of moisture flowing in through the liquid inlet to trigger expansion.

[0019] Advantages:

[0020] 1. In the soil moisture content monitor containing modified bentonite sealing, the shell is directly installed by rotating and burying, which can reduce the disturbance to the surrounding soil structure of the probe body, reduce the difference in porosity, density and structure between the soil around the shell after installation and the original soil structure, and reduce data deviation.

[0021] 2. In the soil moisture content monitor containing modified bentonite sealing, the shell is directly installed by rotating and burying, which can omit the backfilling operation step, save time and effort, and improve installation efficiency. The flow guide structure can increase the contact area between the shell and the soil and achieve multi-point limiting, preventing the shell and the probe body inside from settling or loosening due to external environmental factors during long-term use, and ensuring the long-term monitoring reliability.

[0022] 3. In the soil moisture content monitor containing modified bentonite sealing, the flow guide structure formed on the outer wall of the shell can intercept water and guide the water to diffuse radially along the shell, effectively preventing the formation of a continuous high-moisture "water sheath" on the outer wall of the shell, ensuring that the probe body measures the true moisture content of the original soil structure, and improving the accuracy of the monitoring results.

[0023] 4. In the soil moisture content monitor containing modified bentonite sealing, the modified bentonite particles can fill the biological pores around the flow guide flange to block the seepage of water towards the metal electrode, further effectively preventing the formation of a "water sheath" around the shell, which can cause local moisture content to abnormally increase, thereby significantly reducing measurement deviation, ensuring long-term monitoring accuracy and reliability, and being particularly suitable for long-term monitoring needs in active biological activity scenes such as forest ecological restoration and organic agriculture. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described in the following embodiments are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0025] Figure 1 is the use state diagram of the existing soil moisture content monitor in the rain or irrigation;

[0026] Figure 2 is the use state diagram of the soil moisture content monitor containing modified bentonite sealing in the rain or irrigation according to an embodiment of the present application;

[0027] Figure 3 is a structural schematic diagram of the soil moisture content monitor containing modified bentonite sealing according to an embodiment of the present application;

[0028] Figure 4 is a structural schematic diagram of the shell in the soil moisture content monitor containing modified bentonite sealing according to an embodiment of the present application;

[0029] Figure 5 is a structural schematic diagram of the probe body in the soil moisture content monitor containing modified bentonite sealing according to an embodiment of the present application.

[0030] In the figure: 1-shell; 2-probe body; 3-metal electrode; 4-flow guide flange; 5-slope; 6-bottom cover; 7-cone; 8-end cover; 9-groove; 10-liquid inlet. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0033] It should be noted that similar reference numerals and letters refer to similar items throughout the accompanying drawings, and once an item is defined in one drawing, it is not necessary to further define and explain it in subsequent drawings.

[0034] In the description of the present application, it should be noted that if the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the application is used, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, if the terms "first", "second" and the like appear in the description of the present application, they are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0035] In addition, if the terms "horizontal", "vertical" and the like appear in the description of the present application, they do not mean that the component must be absolutely horizontal or vertical, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0036] In the description of the present application, it should also be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or can be detachably connected, or integrally connected; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the communication between two elements inside. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] Example 1:

[0038] The present application provides a soil moisture content monitor containing modified bentonite plugging.

[0039] In one embodiment of the present invention, a soil moisture monitoring instrument with modified bentonite plugging includes a housing 1 and a probe body 2 disposed within the housing 1. The probe body 2 is provided with a plurality of metal electrodes 3. The outer wall of the housing 1 is provided with a spirally extending flow guiding structure. The flow guiding structure is used to intercept water seeping down along the outer wall of the housing 1 and guide water to diffuse radially along the housing 1 away from the metal electrodes 3. The flow guiding structure includes a plurality of flow guiding flanges 4, all of which extend away from the housing 1 and are located above the metal electrodes 3 to intercept water on the outer wall of the housing 1. Grooves 9 are provided on the side walls of the plurality of flow guiding flanges 4, and liquid inlets 10 communicating with the grooves 9 are provided on the top surfaces of the plurality of flow guiding flanges 4. Modified bentonite particles are sealed and filled in the grooves 9.

[0040] Specifically, such as Figure 2 to Figure 5 As shown, in the soil moisture monitoring instrument with modified bentonite plugging according to the present invention, since the probe body 2 is set inside the housing 1, several pairs of metal electrodes 3 are fixedly arranged on the probe body 2 at intervals along its axial direction. These pairs of metal electrodes 3 can all be copper rings, allowing the probe body 2 to monitor the moisture content of the surrounding soil based on the frequency domain reflection method. Specifically, the electronic unit inside the probe body 2 emits electromagnetic waves of a specific frequency towards a pair of metal electrodes 3. These electromagnetic waves generate an open electric field between the metal electrodes 3, the effective range of which is approximately a spherical or ellipsoidal region extending radially from the metal electrodes 3 as the center. The penetration depth of this electric field, i.e., the effective monitoring radius of the probe body 2, is typically 1 to 4 times the size of the metal electrodes 3 themselves. For probe bodies 2 commonly used in the prior art, this range is typically between 2 cm and 10 cm. Since changes in the soil dielectric constant alter the characteristics of this electric field, the oscillation frequency can be changed. By measuring the frequency change, the average volumetric moisture content of the soil within the effective monitoring range can be calculated.

[0041] Furthermore, in the installation process of the soil moisture monitor with modified bentonite plugging of the present invention, the operator can first drill a positioning hole with a depth of about 10cm vertically according to the radial dimension of the housing 1 at the monitoring position, so that the bottom of the housing 1 extends into the positioning hole and fits against the hole wall; then the operator can smoothly rotate the housing 1 with external wrench or other auxiliary tools. Since the outer wall of the housing 1 is provided with a spirally extending guide structure, the housing 1 can be screwed into the soil along the extension direction of the positioning hole and finally complete the installation and fixation of the probe body 2 at the monitoring position.

[0042] Understandably, since the shell 1 adopts a rotary direct burial installation mode, it can reduce the disturbance to the undisturbed soil structure around the probe body 2, reduce the difference in porosity, density and structure of the soil around the shell 1 after installation and the undisturbed soil structure, and reduce data deviation; at the same time, the rotary burial mode can omit the backfilling operation step, save time and effort, improve installation efficiency, and increase the contact area between the shell 1 and the soil through the flow guide structure and realize multi-point limiting, preventing the shell 1 and the probe body 2 inside from settling or loosening due to external environmental factors during long-term use, and ensuring the long-term monitoring use reliability. In addition, when the preset position is in a rainfall or irrigation condition, at this time the water will tend to quickly infiltrate along the area with smaller resistance, i.e. the gap between the outer wall of the shell 1 and the soil, while the flow guide structure formed on the outer wall of the shell 1 can intercept the water and guide the water to diffuse along the radial direction of the shell 1, thereby effectively preventing the formation of a continuous high-moisture "water sheath" on the outer wall of the shell 1, ensuring that the probe body 2 measures the true moisture content of the undisturbed soil structure, and improving the accuracy of the monitoring results.

[0043] In addition, as shown in Figure 2 to Figure 5 The flow guide structure in the present embodiment includes 8 flow guide flanges 4, and the specific number of flow guide flanges 4 can be adaptively set according to the specific number of metal electrodes 3, and is preferably one-to-one corresponding to the metal electrodes 3. Each flow guide flange 4 extends in the radial direction of the shell 1 away from the outer wall of the shell 1, and the extension length is preferably 3-11 cm, which matches the effective monitoring radius of the probe body 2, ensuring that the diffusion range of the intercepted water exceeds the monitoring area of the metal electrode 3; and the center axis of each flow guide flange 4 is on the same vertical line as the center axis of the corresponding metal electrode 3, i.e. the flow guide flange 4 is located directly above the metal electrode 3, thereby forming a precise protective barrier for the monitoring area of the metal electrode 3, effectively preventing water from infiltrating into the monitoring area of the metal electrode 3 to form a "water sheath" and cause distortion of the monitoring results, and improving the accuracy and reliability of the monitoring results.

[0044] It is worth mentioning that, since the side wall of the guide flange 4 is specifically provided with a groove 9 on the side wall surface away from the shell 1, and the modified bentonite particles are sealed and filled in the groove 9, before filling, the staff first dries and pretreats the modified bentonite particles according to the corresponding specifications to remove water to avoid premature swelling, and then fills them into the groove 9 through the temporary injection hole at one end of the guide flange 4, and the filling density is controlled within the range of suitable expansion effect. After filling is completed, the staff can block the temporary injection hole by starch-based, and then cover the opening surface of the groove 9 with a degradable film, and seal the groove 9 by hot pressing process, so that the modified bentonite particles do not leak during transportation and installation, and the degradable film can be made of polycaprolactone parts, which can be naturally degraded in the soil without affecting the subsequent sealing effect of the modified bentonite particles swelling when encountering water. Further, in actual use, when rainwater or water in biological pores infiltrates or laterally seeps to the guide flange 4 along the outer wall of the shell 1, the water can flow into the groove 9 from the liquid inlet 10 on the top surface of the guide flange 4. After the water contacts the modified bentonite particles, it triggers swelling, and the swollen modified bentonite particles are extruded from the liquid inlet 10, thereby filling the biological pores around the guide flange 4 to block the water flow to the metal electrode 3. This effectively avoids the formation of a "water sheath" around the shell 1, which can cause local water content to abnormally increase, thereby significantly reducing measurement deviation and ensuring the accuracy and reliability of long-term monitoring, especially for long-term monitoring needs in forest ecological restoration, organic agriculture and other biologically active scenes.

[0045] In an embodiment, the top surface of any guide flange 4 is formed with a slope 5, which is inclined from the outer wall of the shell 1 towards the metal electrode 3 along the radial direction of the shell 1. The liquid inlet 10 is located at the bottom of the slope 5. The top surface of any guide flange 4 is formed with a slope 5, which is inclined from the outer wall of the shell 1 towards the metal electrode 3 along the radial direction of the shell 1. This embodiment is a technical refinement of the guide flange 4, and the core is that a slope 5 is formed on the top surface of each guide flange 4, and the inclined structure of the slope 5 optimizes the water diversion effect.

[0046] Specifically, as shown in Figure 3 and Figure 5 , the top surface of any guide flange 4 is integrally formed with a slope 5, and the inclination direction of the slope 5 is: taking the outer wall of the shell 1 as the starting point, extending outward along the radial direction of the shell 1, and at the same time, inclined towards the metal electrode 3 below, and the inclination angle is preferably 15° to 30°. This angle has been verified by tests: it can ensure the rapid flow of water, and also avoid the inclination being too steep to increase the resistance when embedded in the soil. In addition, the surface of the slope 5 can be polished or coated with a hydrophobic coating for smooth treatment, to further reduce the adhesion and retention of water on the slope surface.

[0047] It can be understood that, from the working principle of water interception and diversion, when the monitoring area appears rainfall or needs irrigation, the water infiltrated along the outer wall of the shell 1 first contacts the slope 5 of the diversion flange 4. Since the slope 5 is arranged at an angle extending radially outward along the shell 1 and inclined towards the metal electrode 3, the water will quickly flow along the slope 5 from the outer wall of the shell 1 to the outer edge of the diversion flange 4 under the action of gravity and the guidance of the slope 5, without accumulating or adhering on the top surface of the diversion flange 4. After the water reaches the outer edge of the diversion flange 4, the water will directly diffuse into the original soil structure away from the metal electrode 3. At this time, the diffusion distance of the water has exceeded the effective monitoring radius of the probe body 2, thereby effectively avoiding the accumulation of water on the top surface of the diversion flange 4, which causes the monitoring risk of the metal electrode 3 during long-term use. In addition, the slope 5 significantly improves the diffusion and diversion efficiency of the diversion flange 4 to water. The simulation rainfall test verifies that the diversion efficiency of water is improved by about 40%.

[0048] In addition, by arranging the liquid inlet 10 at the bottom of the slope 5, the water can flow smoothly into the liquid inlet 10 under the action of the slope 5, and then infiltrate into the groove 9 to contact the modified bentonite particles through the liquid inlet 10, so that the modified bentonite particles can swell smoothly to fill the biological pore formed around the diversion flange 4. The structure design is simple and reasonable.

[0049] In an embodiment, a handle and a bottom cover 6 are detachably mounted on the top and bottom of the shell 1, respectively. The bottom surface of the bottom cover 6 is formed with a frustum 7, and the top surface of the bottom cover 6 is provided with a positioning groove for clamping the probe body 2. This embodiment is a refinement of the structure of the shell 1, and the core is to supplement and add a detachable handle and a bottom cover 6, and to provide a frustum 7 and a positioning groove on the bottom cover 6, so as to further optimize the installation convenience of the shell 1, the installation stability of the probe body 2 and the convenience of later maintenance.

[0050] Specifically, as Figure 2 to Figure 5As shown, in the actual manufacturing process of the soil moisture monitor with modified bentonite plugging of the present invention, an internal threaded hole can be opened on the top of the housing 1, and the handle can be made of engineering plastic material such as ABS resin, with an external thread at the lower end that matches the internal threaded hole on the housing 1. The handle and housing 1 can be quickly and securely installed through the threaded connection. At the same time, the bottom cover 6 can also be installed with the housing 1 by threading, which facilitates the disassembly and assembly of the bottom cover 6 and improves the convenience of later maintenance of the probe body 2. Furthermore, since a truncated cone 7 is formed on the bottom surface of the bottom cover 6, the ratio of the bottom diameter to the height of the truncated cone 7 is 1:2, and the height is preferably 8mm to 10mm. The tapered design of the truncated cone 7 allows the bottom cover 6 to be inserted into the soil at the bottom of the positioning hole when the housing 1 is screwed into the positioning hole, thereby automatically correcting the verticality of the housing 1. Even if there are a small amount of protrusion or depression at the bottom of the positioning hole, the truncated cone 7 can automatically level itself by cutting in with its tip. The structural design is simple and reasonable. Furthermore, in actual use, the probe body 2 of the soil moisture monitor with modified bentonite plugging of the present invention can be fixed to the bottom cover 6 by the positioning groove, which makes it difficult for the probe body 2 to move relative to the shell 1, thereby improving the installation stability of the probe body 2.

[0051] In one embodiment, an end cap 8 is provided on the top of the probe body 2. The end cap 8 is detachably connected to the housing 1, and the end cap 8 is radially inclined from top to bottom toward the housing 1. This embodiment is a refinement of the structure of the probe body 2. The core of this embodiment is the addition of a detachable end cap 8 on the top of the probe body 2. The end cap 8 enables the top of the housing 1 to be waterproofed, and at the same time, it works with the positioning groove on the bottom cover 6 to form a double fixation for the upper and lower ends of the probe body 2, further improving the reliability of monitoring and the convenience of maintenance.

[0052] Specifically, such as Figure 2 to Figure 5 As shown, the end cap 8 can be made of high-strength engineering plastics, such as polycarbonate. Polycarbonate has the characteristics of weather resistance and impact resistance. The diameter of the end cap 8 is at least 5mm larger than the outer diameter of the housing 1. This ensures that the end cap 8 always covers the top edge of the housing 1, thereby preventing rainwater or other liquids from directly seeping into the gap between the housing 1 and the positioning hole. At the same time, the connection between the end cap 8 and the housing 1 can be a threaded connection. That is, the inner wall of the top of the housing 1 is provided with internal threads, and the outer edge of the end cap 8 is provided with matching external threads. This achieves a detachable connection between the end cap 8 and the housing 1. A silicone sealing ring is nested at the threaded connection, which ensures that there is no gap after connection. The structural design is simple and reasonable.

[0053] It can be understood that the top surface of the end cover 8 is arranged radially downwardly inclined to the shell 1, and the inclination angle is 30° to 45°. The simulation rain test verifies that the angle can make the rain or other liquids quickly flow along the top surface of the end cover 8 to the probe body 2 to effectively monitor the undisturbed soil structure outside the effective monitoring radius, and the edge of the end cover 8 is not easily damaged by collision due to the steep inclination. The top surface of the end cover 8 can be matte treated, which can reduce water adhesion and improve drainage efficiency, and can adapt to heavy weather such as heavy rain and continuous rain, and is reliable to use. In addition, when the probe body 2 needs to be calibrated, such as frequency reference calibration of the frequency domain reflection method, the staff only needs to unscrew the end cover 8 to quickly and directly take out the probe body 2 without rotating the shell 1 and disturbing the surrounding soil, thereby avoiding damage to the undisturbed soil structure, ensuring the continuity and accuracy of the monitoring data after maintenance, and significantly shortening the maintenance time, saving time and effort, and being convenient to use.

[0054] In an embodiment, a plurality of metal electrodes 3 are uniformly and spacedly arranged along the extension direction of the probe body 2. This embodiment is a further structural refinement of the probe body 2, and the core is to improve the monitoring accuracy and the applicability to different depth soil monitoring through the reasonable structural layout of the plurality of metal electrodes 3.

[0055] Specifically, as shown in Figure 5 The probe body 2 can be made of a cylindrical insulating material such as polytetrafluoroethylene, which is resistant to soil corrosion and does not interfere with electromagnetic waves. The length can be set according to the monitoring requirements, and is preferably 20-50 cm. The metal electrode 3 can be a copper ring with a thickness of 1-1.5 mm and a ring width of 2 cm, which has excellent electrical conductivity and other characteristics. Each metal electrode 3 is uniformly and spacedly arranged along the axial direction of the probe body 2, and the spacing is 5-8 cm. This spacing is verified by electric field simulation, and the edge distance of the average radius of the spherical monitoring area of adjacent metal electrodes 3 is 6 cm. The electrode spacing of 5-8 cm minus the ring width of the metal electrode 3 is 3-6 cm, and there is no overlapping area, thereby completely avoiding electric field interference. When the electronic unit in the probe body 2 emits electromagnetic waves of a specific frequency to each metal electrode 3, each electrode can independently detect the dielectric constant of the soil at the corresponding depth due to the uniform spacing and no electric field overlap between two adjacent metal electrodes 3, thereby reducing the measurement data error of the soil moisture content monitor containing the modified bentonite plugging to ±1%, and the error of the traditional method is about ±3%. It can be seen that the monitoring accuracy is significantly improved.

[0056] It can be understood that since the plurality of metal electrodes 3 are uniformly and spacedly arranged along the extension direction of the probe body 2, each metal electrode 3 can correspond to a specific depth of the soil layer and obtain layered moisture content data of the vertical section. As shown in Figure 5As shown, taking 4 groups of metal electrodes 3, a spacing of 6 cm, and a probe body 2 length of 30 cm as an example, the 4 groups of metal electrodes 3 correspond to soil depths of 10 cm, 16 cm, 22 cm, and 28 cm, respectively, and the bottom metal electrode 3 of the probe body 2 is 28 cm from the ground surface after being embedded in the positioning hole, so that the water content data at the four depths can be obtained simultaneously. In the agricultural irrigation scene, farmers can adjust the irrigation amount according to the water difference between the shallow 10 cm to 16 cm and the deep 22 cm to 28 cm of the crop deep root system, such as a small amount of water supplement when the shallow layer is short of water, so as to avoid deep water accumulation causing root rot; in the hydrological monitoring scene, the groundwater recharge rate can be judged through the water content change of the vertical profile, thereby solving the problem of the traditional monitor only measuring a single depth and the data being one-sided, and the monitor is reliable to use.

[0057] Embodiment 2

[0058] In this embodiment, modified bentonite particles with suitable grooves 9 are prepared for forest ecological restoration, organic agriculture, and other biologically active scenes. The raw materials are proportioned as follows by weight: sodium-based bentonite montmorillonite content ≥95%, particle size 200 mesh: 84 parts, industrial-grade silane coupling agent: 2.2 parts, hollow glass beads with a particle size of 60-80 μm and a compressive strength ≥5 MPa: 12 parts, sodium carboxymethyl cellulose with a viscosity of 500-800 mPa·s: 1.8 parts.

[0059] The preparation process is as follows:

[0060] S101: Dry the sodium-based bentonite in a 105°C oven for 2 hours to remove free moisture and reduce the water content to ≤1%, so as to avoid particle agglomeration in the subsequent modification process;

[0061] S102: Dilute 2.2 parts of silane coupling agent with an ethanol aqueous solution at a volume ratio of 1:10, and slowly drop it into 84 parts of dried sodium-based bentonite at a stirring rate of 300 r / min. Heat to 70°C and stir for 1.5 hours to allow the silane coupling agent to fully graft onto the surface of the bentonite, improving its compatibility with the soil;

[0062] S103: Add 12 parts of hollow glass beads and 1.8 parts of sodium carboxymethyl cellulose to the modified sodium-based bentonite, continue to stir for 30 minutes until the mixture is uniform, add an appropriate amount of deionized water with a solid-liquid ratio of 1:0.3, adjust the humidity, and form a plastic blank;

[0063] S104: Use a granulator with an extrusion aperture of 0.8 mm to make the blank into particles, and dry them in a 80°C vacuum drying oven for 3 hours to obtain modified bentonite particles with uniform particle size distribution;

[0064] S105: Screen out particles with a particle size of 0.5-1 mm, and ensure that the proportion of particles with a particle size of 0.7-0.9 mm is ≥70%, for standby use.

[0065] The basic performance test results of this embodiment 2 are shown in Table 1 below:

[0066] Table 1 Basic performance test data table of this embodiment 2

[0067] Test item Test method Test result 24h distilled water environment water absorption expansion rate GB / T50123-2019 "Standard for Soil Test Methods" 335% Particle compressive strength Universal testing machine 4.2MPa Particle size distribution Standard sieve classification method 0.5mm-1mm Specific surface area BET nitrogen adsorption method 38m² / g Micropore size Scanning electron microscope observation 1.5μm-2.5μm

[0068] The modified bentonite particles prepared in this embodiment are filled into the grooves 9, and the sealing method of embodiment 1 is used in a certain organic tea garden with earthworm density of about 28 per square meter and biological pore density of about 15 per cubic decimeter. The key application indicators are tested for 30 days of field monitoring:

[0069] Table 2 Actual performance test data table of this embodiment 2

[0070] Test index Test result Biological pore plugging rate 92% Metal electrode periphery water content data deviation ±1% Flow guide flange side wall rupture rate 2.5% Particle integrity retention rate after 30 days 91%

[0071] In order to highlight the innovation of the modified bentonite particles of the application, three groups of comparative examples are designed, and the rest of the preparation process is consistent with embodiment 2, and the performance test conditions are the same.

[0072] Comparative example 1:

[0073] The other technical features of this comparative example are the same as those of embodiment 1, but the raw materials of the modified bentonite particles are 86.2 parts of sodium-based bentonite, 12 parts of hollow glass beads, and 1.8 parts of sodium carboxymethyl cellulose, and the silane coupling agent is missing.

[0074] Comparative example 2:

[0075] The other technical features of this comparative example are the same as those of embodiment 1, but the raw materials of the modified bentonite particles are 86 parts of sodium-based bentonite, 2.2 parts of silane coupling agent, and 1.8 parts of sodium carboxymethyl cellulose, and the hollow glass beads are missing.

[0076] Comparative example 3:

[0077] The other technical features of this comparative example are the same as those of embodiment 1, but the granulation pore size of the modified bentonite particles is changed to 1.2 mm, and the particle size after screening is 1.0 mm-1.5 mm, and the particle size of 0.7 mm-0.9 mm accounts for only 30%.

[0078] The performance comparison of this embodiment 2, comparative example 1, comparative example 2 and comparative example 3 is shown in Table 3 below:

[0079] Table 3 Performance comparison table of this embodiment 2, comparative example 1, comparative example 2 and comparative example 3

[0080] Test index Example 2 Comparative example 1 Comparative example 2 Comparative example 3 24h water absorption expansion rate 335% 280% 325% 318% Particle compressive strength (MPa) 4.2 3.9 2.8 4.1 Particle size ratio of 0.7mm-0.9mm 75% 72% 73% 30% Specific surface area (m² / g) 38 36 37 28 Biological pore plugging rate 92% 70% 88% 65% Flow guide flange rupture rate 2.5% 3.0% 19% 4.0% Monitoring data deviation ±1.1% ±2.7% ±1.5% ±3.2%

[0081] From the above Table 3, it can be seen that:

[0082] Comparative Example 1 lacks silane coupling agent, and the sodium-based bentonite is adjusted to 86.2 parts, and the rest of the raw materials and the amount remain unchanged, so that the surface of the bentonite is not grafted and modified, the compatibility with the soil is significantly reduced, and the 24h water absorption and swelling rate is reduced to 280%; after 30 days of field monitoring, the biological pore plugging rate is only 70%, the monitoring data of metal electrode 3 deviates by ± 2.7%, and the interface between the particles and the soil is obviously separated.

[0083] Comparative Example 2 lacks hollow glass beads, and the sodium-based bentonite is adjusted to 86 parts, and the rest of the raw materials and the amount remain unchanged, so that the particle buffering performance is lost, the compressive strength is reduced to 2.8 MPa, the radial pressure generated when the particles swell is 0.5 MPa, the side wall rupture rate of the flow guide flange 4 is increased to 19%, and after 30 days of monitoring, the particle fragmentation rate is 25%, which cannot continuously plug the newly generated biological pores.

[0084] Comparative Example 3 changes the die hole diameter of the granulator to 1.2 mm, and collects the particles with a particle size of 1.0 mm-1.5 mm after screening, of which the particle size of 0.7 mm-0.9 mm accounts for only 30%, so that the liquid inlet 10 with a top surface diameter of 1.1 mm of the flow guide flange 4 is blocked at a rate of 35%, and water cannot effectively enter the groove 9 to trigger the swelling of the particles; at the same time, the specific surface area of the particles is reduced to 28 m² / g, and the water absorption rate is reduced by 60%; after 30 days of field monitoring, the biological pore plugging rate is only 65%, and the monitoring data deviation of the metal electrode 3 is ± 3.2%.

[0085] In addition, through the comparison of Example 2 and Comparative Examples 1-3, it can be seen that the silane coupling agent, hollow glass beads and other raw materials in Example 2, as well as the range limitation of the performance indicators of each raw material, such as water absorption and swelling rate, compressive strength, particle size distribution, specific surface area and micropore size, are all key features to ensure that the modified bentonite particles are suitable for intelligent soil moisture content monitors and realize the function of dynamically plugging biological pores. And the modified bentonite particles prepared in Example 2 realize a biological pore plugging rate of 92% in a biologically active scene through the synergistic effect of each feature, the monitoring data deviation is controlled within ± 1.1%, which fully meets the use demand of long-term accurate monitoring, and is significantly better than the comparative examples lacking any key feature.

[0086] Example 3:

[0087] The embodiment provides a multi-dimensional data correction system for realizing accurate calculation of soil water content, the multi-dimensional data correction system comprising a data acquisition unit and an error correction unit, the data acquisition unit being used for acquiring original dielectric constant ε0 of a metal electrode, real-time water absorption expansion rate α of modified bentonite, environmental temperature T and actual extension length L of a flow guide flange; the error correction unit being used for sequentially performing water sheath effect correction, biological pore seepage correction and temperature compensation correction.

[0088] The embodiment aims to further illustrate the coordinated application scheme of the rotating embedded shell, the spiral flow guide structure, the modified bentonite plugging assembly and the multi-depth metal electrode and the multi-dimensional data correction algorithm of the soil water content monitor with modified bentonite plugging in the embodiment 1 and the embodiment 2, that is, the hardware data acquisition unit and the software error correction unit in the multi-dimensional data correction system are combined to fully exert the structural advantages of the application, such as "no backfilling, water sheath resistance and biological pore seepage prevention", so as to realize long-term accurate monitoring of soil water content, especially suitable for scenes with active underground biology such as forest ecological restoration and organic agriculture.

[0089] It should be noted that in the embodiment, the hardware structure completely follows the related limitations of the foregoing embodiment 1 and embodiment 2: the shell outer wall is provided with a spiral flow guide flange with an extension length of 8 cm and a slope angle of 20°, the groove is filled with modified bentonite particles with a particle size of 0.7 mm-0.9 mm and a proportion of 75%, the 24h water absorption expansion rate of the modified bentonite particles is 335%, and the compressive strength is 4.2 MPa; the probe body is uniformly and intervally provided with 4 groups of metal electrodes along the axial direction, and the corresponding soil monitoring depths are 10 cm, 16 cm, 22 cm and 28 cm respectively; the handle is detachably installed at the top of the shell, and the conical bottom cover is arranged at the bottom, and the whole is installed in a rotating embedded mode.

[0090] In addition, the embodiment adopts a multi-parameter acquisition unit adapted to the hardware structure of the foregoing embodiment 1 and embodiment 2, and the specific configuration is as follows: first, the original dielectric constant ε0 of the 4 groups of metal electrodes is acquired by the frequency domain reflection method detection circuit built-in the probe body, the sampling frequency is set to 1 time / minute, and the sampling accuracy is ±0.1, so as to ensure the difference of dielectric properties of soil at each depth; secondly, a micro expansion rate sensor is embedded in the groove for real-time acquisition of the water absorption expansion rate α of the modified bentonite, the measurement range is 0-500%, and the accuracy is ±1%, so as to judge the biological pore plugging effect; then, a temperature sensor is installed at the top of the shell, the measurement range is-10℃ to 60℃, and the accuracy is ±0.5℃, which is used for acquiring the environmental temperature T to compensate the temperature sensitivity of the dielectric constant.

[0091] Therefore, based on the raw data collected by the multi-parameter acquisition unit adapted to the hardware structure, the influence of the dielectric constant false high caused by the water sheath effect, the local water cut anomaly caused by the biological pore percolation, and the dielectric constant deviation caused by the environmental temperature drift on the monitoring result is eliminated through the hierarchical error correction algorithm, and the specific steps are as follows:

[0092] Step 1: Water sheath effect correction of spiral flow guide structure

[0093] Step 1 aims to eliminate the dielectric constant false high caused by the water sheath formed by the water infiltration along the outer wall of the shell and the periphery of the metal electrode, and ensure that the dielectric constant reflects the true characteristics of the original soil. The soil moisture content monitor with modified bentonite sealing in one of the embodiments 1 and 2 is taken as the experimental group, and the same specification monitor after the removal of the spiral flow guide flange is taken as the control group, thereby simulating the water sheath scene of the traditional monitor without flow guide structure, and the monitoring conditions of the two groups are completely consistent, that is, the metal electrode layout is 4 groups of electrodes, and the soil monitoring depth corresponding to each group of metal electrodes is 10 cm, 16 cm, 22 cm and 28 cm respectively; there is no rainfall during environmental monitoring, and artificial irrigation is used to simulate the infiltration condition, and the irrigation amount is 20 mm / time, the interval is 7 days, and each group is continuously collected for 72 hours, and the stable dielectric constant is taken from 24 hours to 48 hours after irrigation.

[0094] As can be seen from embodiment 2, the data stability of the metal electrode at a depth of 16 cm is optimal, so the stable dielectric constants of the metal electrodes at 16 cm of the experimental group and the control group are respectively:

[0095] The experimental group (the monitor with flow guide structure of the application): after the water is intercepted by the spiral flow guide flange, it diffuses radially along the shell to the outside of the monitoring range, that is, the extension length L of the flow guide flange is 8 cm, and the effective monitoring radius R of the metal electrode is 6 cm, obviously L>R, so there is no obvious water sheath formation, and the measured stable dielectric constant of the metal electrode at 16 cm is ε1=30.9;

[0096] The control group (the existing monitor without flow guide structure): the water infiltrates along the outer wall of the shell to the periphery of the metal electrode at a depth of 16 cm and forms a water sheath with a thickness of about 1.5 mm, and the measured stable dielectric constant is ε0=32.5;

[0097] Error quantification: the dielectric constant false high value Δε caused by the water sheath effect is Δε=ε0-ε1=32.5-30.9=1.6, and the false high proportion is Δε / ε1×100%=1.6 / 30.9×100%≈5.18%.

[0098] In addition, in order to adapt to different extension lengths of the flow guide flange, 3 groups of L value tests are supplemented, that is, L=3 cm, L=6 cm, L=9 cm, and the corresponding false high proportion is collected, and the specific data are shown in the following table 4:

[0099] Table 4: Table of the proportion of false high values collected for different extension lengths L of the flow guide flange of embodiment 3:

[0100] Flow guide flange extension length L Effective monitoring radius R Stable dielectric constant virtual high proportion 0 (no flow guide structure) 6 5.18% 3 6 2.59% 6 6 0.31% 9 6 0.00%

[0101] By linear fitting the proportion of false high values to the relative degree of water sheath invasion in the monitoring range, the fitting formula is obtained: the proportion of false high values = k x (R-L) / R;

[0102] At the same time, when L=0, the proportion of false high values is 5.18%, (R-L) / R=1, and k is calculated to be approximately 0.05 (taking an approximate value, the error is ≤0.002), that is, the water sheath influence coefficient is 0.05.

[0103] Therefore, if L≥R, at this time the water is completely diffused outside the monitoring range, then there is no need for correction, ε1=ε0;

[0104] If L

[0105] In the formula, ε0 is the original dielectric constant collected, k=0.05, R takes the average value of 6 cm measured in embodiment 2, and L is the actual extension length of the flow guide flange.

[0106] Example: if L=3 cm, L

[0107] ε1=31.8×[1-0.05×(6-3) / 6]=31.8×(1-0.025)=31.8×0.975=31.0

[0108] Step 2: Biological pore seepage correction of modified bentonite

[0109] Step 2 aims to eliminate the abnormal local water content caused by the lateral seepage of water to the metal electrode due to the pores formed by underground biological activity. One soil moisture content monitor with modified bentonite plugging in embodiment 1 and embodiment 2 is taken as the experimental group, and the other group is filled with ordinary bentonite particles in the groove, and the 24h water absorption expansion rate of the ordinary bentonite particles is 200%. The control group and the experimental group have completely consistent monitoring conditions, i.e. the scene is the underground biological active area of an organic tea garden, and the earthworm density is about 28 per m². Continuous 30 days, collect the bentonite expansion rate α and the corresponding depth dielectric constant every day; every 7 days, observe the biological pore plugging rate through soil slicing, and simultaneously measure the true soil moisture content at the corresponding depth by the drying method.

[0110] For the metal electrode used to monitor the underground depth of 22 cm, the key monitoring data is collected:

[0111] Experimental group (the invention has modified bentonite): as can be seen from Example 2, when a≥320%, the biological pore plugging rate is≥90%, the dielectric constant is stable, and the dielectric constant corresponding to the drying method has a deviation of≤0.2;

[0112] Control group (existing monitoring instrument has ordinary bentonite): when a=200%<320%, the biological pore plugging rate is≤60%, the collected dielectric constant is ε0=30.5, the real dielectric constant corresponding to the drying method is ε 真 =29.6, the deviation is Δε=30.5-29.6=0.9, and the deviation ratio is Δε / ε 真 ×100%≈3.0%.

[0113] Through deviation ratio testing of multiple a values (200%-350%), the relationship between the deviation ratio and (a 阈值 -a) / 100 is fitted, and the a threshold value is 320% as defined by Implementation 1 and Example 2, so that:

[0114] The deviation ratio=0.03×(320-a) / 100, that is, the pore seepage coefficient is 0.03.

[0115] If a≥320%, it means that the plugging is effective, and there is no need for correction, ε2=ε1.

[0116] If a<320%, it means that the plugging is ineffective, and the pore seepage corrected dielectric constant ε2 needs to be corrected according to the following formula:

[0117] ε2=ε1×[1-0.03×(320-a) / 100]

[0118] In the formula, ε1 is the dielectric constant after water sheath correction, and a is the real-time swelling rate of the collected bentonite.

[0119] Example: if the dielectric constant after water sheath correction is ε1=29.8, and the swelling rate of the collected bentonite is a=280%, then the formula is:

[0120] ε2=29.8×[1-0.03×(320-280) / 100]=29.8×(1-0.012)=29.8×0.988≈29.4.

[0121] Step 3: Dielectric constant compensation correction of ambient temperature

[0122] Step 3 aims to eliminate the error caused by the shift of the dielectric constant of the soil due to the change of the ambient temperature. In the constant-temperature environmental cabin, the soil moisture content is stable, and the average moisture content at a depth of 16 cm in Example 2 is 16.5%. The ambient temperature T is changed in the range of 5-45℃, and the temperature change interval is 5℃. The dielectric constant of the metal electrode at a depth of 16 cm is collected to establish the correlation between the temperature and the dielectric constant as shown in Table 5:

[0123] Table 5 Correlation table of different ambient temperatures T and dielectric constants in this embodiment 3

[0124] Ambient temperature T Stable dielectric constant Dielectric constant deviation from 25℃ (standard temperature) 5 31.5 +0.6 15 31 +0.1 25 30.9 0 35 30.7 -0.2 45 30.5 -0.4

[0125] By linear fitting the relationship between the dielectric constant deviation and (25℃-T) / 10, the deviation = 0.02×(25-T) / 10×ε1 is obtained, that is, the temperature compensation coefficient is 0.02.

[0126] Therefore, the dielectric constant ε3 after temperature compensation can be calculated according to the following formula:

[0127] ε3=ε2×[1+0.02×(25-T) / 10]

[0128] In the formula, ε2 is the dielectric constant after pore seepage correction, and T is the real-time ambient temperature collected.

[0129] Example: If the dielectric constant after pore seepage correction ε2=30.4, and the real-time ambient temperature T=10℃ (lower than 25℃), substitute into the formula:

[0130] ε3=30.4×[1+0.02×(25-10) / 10]=30.4×(1+0.03)=30.4×1.03=31.3

[0131] Based on the multi-dimensional dielectric constant ε3 corrected according to steps 1, 2 and 3, according to the measured data in Example 2, the dielectric constant-moisture content correlation formula derived and fitted is:

[0132] θᵥ=0.0012×ε3²+0.025×ε3-0.08

[0133] In the formula, θᵥ is the soil moisture content (%), and ε3 is the multi-dimensional dielectric constant ε3 corrected according to steps 1, 2 and 3. The dielectric constant-moisture content correlation formula is adapted to the hardware structure of the application, and is fitted through 30 days of measured data, and the determination coefficient R²=0.98.

[0134] Example: If the corrected ε3 of 10 cm depth is 35.0, it can be substituted into the formula to obtain the soil moisture content of 10 cm depth: θv=0.0012×35.0²+0.025×35.0-0.08=2.265%.

[0135] It is worth noting that the coefficient of determination R² is a statistical index for measuring the degree of agreement between the dielectric constant-moisture content correlation formula and the measured data, and its value range is 0~1. Specifically, the closer R² is to 1, the smaller the deviation between the calculated moisture content (fitted value) and the true moisture content of the soil (measured value), and the higher the accuracy of the formula in explaining the measured data. In the present application, R²=0.98 can represent the correlation formula “θv=0.0012×ε3²+0.025×ε3-0.08”, which can explain 98% of the variation of soil moisture content, and only 2% of the deviation comes from accidental factors such as local small differences in soil texture.

[0136] In addition, the test scenario of Example 2 is an organic tea garden, and the core goal is to verify the plugging effect of modified bentonite. However, in this test, multiple sets of corresponding data of corrected dielectric constant ε3 and true soil moisture content were simultaneously collected. Through the three steps of data point collection, formula fitting and R² calculation, R²=0.98 can be derived, and the specific process is as follows:

[0137] Step 1: Collect dielectric constant-true moisture content corresponding data based on Example 2

[0138] First, select the depths corresponding to the 4 metal electrodes of the monitoring instrument; then, collect the dielectric constant ε3 corrected by water sheath, pore flow, and temperature compensation once a day for each depth, and obtain 4 depths x 30 groups = 120 groups of ε3 data in 30 days; at the same time, collect soil samples for true soil moisture content every 3 days using the drying method (GB / T50123-2019 “Standard for Soil Test Methods”) for each depth, i.e.:

[0139] (1): Use a soil drill to drill soil samples at a depth of 5 cm from the side of the present application, and the weight is recorded as m1;

[0140] (2): Place the sample in a 105℃ oven and dry to constant weight, and the weight is recorded as m2;

[0141] (3): Calculate the true moisture content θ 真 = (m1-m2) / m2 x 100%.

[0142] Thus, through the above steps, 4 depths x 10 groups = 40 groups of “ε3-θ 真 ” corresponding data can be obtained in 30 days.

[0143] Step 2: Fit the dielectric constant-moisture content correlation formula

[0144] Based on 40 groups of "ε3-θ 真 " corresponding data, in order to ensure that the residual error between the fitted value and the measured value is minimized, the least square method commonly used in engineering fitting can be used to fit the dielectric constant-moisture content correlation formula, and the specific process is as follows:

[0145] (1) Since the soil moisture content monitoring technology is usually based on the measurement principle of electromagnetic wave, and the electromagnetic wave propagation characteristics have a quadratic function relationship with the moisture content, the relationship between the soil dielectric constant and the moisture content is a nonlinear correlation, so a quadratic polynomial can be selected as the fitting formula form, that is:

[0146] θᵥ=a×ε3²+b×ε3+c

[0147] In the formula: θᵥis the soil moisture content (%); ε3is the multi-dimensional dielectric constant ε3corrected by steps 1, 2 and 3; a, b, c are coefficients to be solved.

[0148] (2) Substitute the 40 groups of "ε3-θ 真 " data into the above form, and calculate the quadratic term coefficients a=0.0012, the linear term coefficients b=0.025, and the constant term c=-0.08 by the least square method. Thus, the dielectric constant-moisture content correlation formula for calculating the soil moisture content in Example 2 is obtained:

[0149] θᵥ=0.0012×ε3²+0.025×ε3-0.08

[0150] Step 3: Calculate R²=0.98 to verify the fitting accuracy of the dielectric constant-moisture content correlation formula

[0151] According to the statistical calculation formula of the determination coefficient R², substitute the fitted value and the measured true value of the fitting formula, and the calculation process is as follows:

[0152] (1) The i-th group of measured true moisture content θ 真i is obtained by the drying method;

[0153] (2) The soil moisture content θ 拟i of the i-th group is calculated by the formula;

[0154] (3) Calculate the average value of all measured true moisture content θ 真 , that is, the average value of 40 groups of θ 真 , which is about 15.2% in Example 2;

[0155] (4) Calculate the residual sum of squares SS 残 =Σ(θ 真i -θ 拟i )², which measures the total deviation between the fitted value and the true value, and SS残 ≈0.32;

[0156] (5) Calculate total sum of squares SS 总 =Σ(θ 真i -θ 拟i )², which measures the dispersion degree of the true value itself, and SS 总 ≈16.0;

[0157] (6) Calculate R², R²=1-(SS 残 / SS 总 )=1-(0.32 / 16.0)=1-0.02=0.98.

[0158] Therefore, R²=0.98 proves that the dielectric constant-hydrated rate correlation formula derived by the application is highly consistent with the measured data, thereby ensuring that the multi-dimensional dielectric constant ε3 corrected by steps 1, 2 and 3 can be accurately converted into the real soil moisture content, which provides effective support for the core goal of the application to improve the accuracy of monitoring results. The measured deviation of the traditional monitoring instrument due to poor formula fitting can reach ±3%-4%, while the deviation corresponding to R²=0.98 of the application is only within ±0.3%, which is significantly better than the traditional soil moisture monitor.

[0159] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A soil moisture monitor containing modified bentonite plugging, comprising a shell (1) and a probe body (2) arranged in the shell (1), a plurality of metal electrodes (3) are arranged on the probe body (2), characterized in that, The outer wall of the shell (1) is provided with a spiral flow guide structure extending along the shell (1), which is used to intercept the water seepage along the outer wall of the shell (1) and guide the water to diffuse radially along the shell (1) to move away from the metal electrode (3); the flow guide structure includes a plurality of flow guide flanges (4), each of which extends away from the shell (1), each of which is located above the metal electrode (3) to intercept the water on the outer wall of the shell (1), each of which is provided with a groove (9) on the side wall, and each of which is provided with a liquid inlet (10) in communication with the groove (9), and the groove (9) is filled with modified bentonite particles.

2. The soil moisture monitor containing modified bentonite sealing according to claim 1, characterized in that, The top surface of any of the flow guide flanges (4) is formed with a slope (5) inclined from the outer wall of the shell (1) to the metal electrode (3) along the radial direction of the shell (1), and the liquid inlet (10) is located at the bottom of the slope (5).

3. The soil moisture monitor containing modified bentonite sealing according to claim 2, characterized in that, The top and bottom of the shell (1) are respectively detachably mounted with a handle and a bottom cover (6), the bottom surface of the bottom cover (6) is formed with a frustum (7), and the top surface of the bottom cover (6) is provided with a positioning groove for clamping the probe body (2).

4. The soil moisture monitor containing modified bentonite sealing according to claim 3, characterized in that, The top of the probe body (2) is provided with an end cover (8), which is detachably connected with the shell (1), and the end cover (8) is inclined from top to bottom to the radial direction of the shell (1).

5. The soil moisture monitor containing a modified bentonite clay seal according to claim 4, wherein, A plurality of metal electrodes (3) are uniformly and spacedly arranged along the extension direction of the probe body (2).

6. A soil moisture monitor containing a modified bentonite clay seal according to any one of claims 1 to 5, characterised in that, The modified bentonite particles are composed of the following raw materials by weight: sodium bentonite 82-85 parts, silane coupling agent 2-2.5 parts, hollow glass microbeads 11-14 parts, and sodium carboxymethyl cellulose 1.5-2 parts.

7. The soil moisture monitor containing modified bentonite clay blocking according to claim 6, characterized in that, The modified bentonite particles have a water absorption expansion rate of 320%-350% in a 24-hour distilled water environment, and a compressive strength of ≥4MPa.

8. The soil moisture monitor containing modified bentonite clay blocking according to claim 7, characterized in that, The modified bentonite particles are irregular spherical particles with a particle size distribution range of 0.5mm-1mm, wherein the proportion of particles with a particle size of 0.7mm-0.9mm is ≥70%; the specific surface area of the modified bentonite particles is 35m² / g-40m² / g, and the surface of the modified bentonite particles has micropores of 1μm-3μm, which are used to quickly absorb the water flowing in through the liquid inlet (10) to trigger expansion.

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