Real-time measurement method for moisture content of soil body

Abstract

The invention relates to the technical field of soil body detection, and provides a soil body moisture content real-time measurement method which comprises the following steps: S01, preparing a test probe which is provided with four conductive parts, the four conductive parts are arranged at intervals and are mutually insulated, and the conductive parts are used for being in contact with a soil body; s03, introducing a constant current I into two adjacent conductive parts, measuring a voltage U between the two conductive parts which are not introduced with the current, and delimiting a voltage fluctuation threshold value ZU according to test data of the voltage U; s05, the test probe is hit into the soil body, and the number N of hit times of the test probe before the conductive part is in contact with the soil body is recorded; s05-C, recording the fluctuation frequency M of the voltage after the conductive part enters the soil body. The problems that in the using process of a traditional mode, a large amount of manpower and material resources are consumed, large fluctuation exists in detection data, a sensor is prone to being damaged, the maintenance cost is high, the digitization degree is low, the hysteresis quality is serious, and real-time uploading cannot be achieved are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil detection, and in particular to a method for real-time measurement of soil moisture content. Background Art

[0002] my country's railway lines have the characteristics of a large span and wide radiation depth. During operation, they have to cross different geological conditions and experience different climatic conditions. These geological and climatic conditions put forward higher requirements on the roadbed. However, during the service of the roadbed, the water content inside the roadbed tends to increase due to the influence of rainfall and groundwater changes. This will cause uneven settlement of the roadbed and instability of the slope. In high altitudes and cold areas, the frost heave disease of the roadbed will often be aggravated. When the temperature rises, mud will overflow. The roadbed is in a freeze-thaw cycle for a long time. In the long run, it will cause the roadbed to lose strength and cause serious diseases. These diseases will seriously affect the smoothness of the roadbed, threaten transportation safety, and reduce transportation efficiency. Therefore, the real-time and continuous spatial detection of the water content in the roadbed is of great significance to ensure the safety of railway transportation and improve the efficiency of railway transportation. At present, the commonly used soil moisture test methods mainly include: traditional drying method and moisture sensor measurement.

[0003] The traditional drying method refers to taking soil samples on site by drilling and other means, placing the soil samples in a drying box, and calculating the soil moisture content by measuring the mass difference before and after drying. This determination method requires collecting soil samples on site. In order to make the moisture content of the collected soil samples highly representative and to better describe the moisture content distribution of the roadbed section, it will be necessary to collect more points. At the same time, the collection process often requires the cooperation of construction machinery, which will consume a lot of manpower and material resources. This method is often used to judge the distribution of soil moisture content after the roadbed disease occurs. It cannot realize the real-time perception of the roadbed soil moisture content during rainfall and changes in groundwater levels. This method has a large hysteresis, and cannot achieve real-time monitoring of the prediction of the internal moisture content state of the roadbed and the prediction of landslide collapse. Therefore, the use of the drying method to measure the roadbed soil moisture content will not meet actual needs.

[0004] The sensor measurement method is to measure the soil moisture distribution by laying sensors inside the roadbed. For example, during the construction process, moisture sensors are laid in the soil, and then the soil moisture distribution is measured. However, this method has certain limitations, such as: when laying sensors, it is necessary to reserve sensor transmission cable channels, which will affect the construction process, and corresponding power supply facilities need to be laid. When the sensor is damaged, it is relatively troublesome to replace it. At the same time, the method of laying sensors is mostly used on newly built roadbeds. However, due to the long operation time and large traffic volume of existing lines, the drainage facilities may face disrepair, and rainwater and other moisture cannot be effectively discharged. Therefore, it is of great significance to pay attention to the roadbed diseases caused by the infiltration of rainwater and other moisture in the existing line bed. However, the method of laying sensors inside the roadbed to measure the distribution of internal moisture may have the problem of poor applicability. Therefore, the method of laying sensors to measure soil moisture also has certain limitations.

[0005] In order to solve the above problems, scholars have proposed a series of solutions to the problems existing in the current moisture content measurement process. For example, the patent with announcement number CN210037508U announced a simple rock and soil test tool. A simple measuring tool containing a wooden casing is placed in the soil to be tested. After the moisture content of the soil to be tested and the wooden casing is balanced, the color change of the wooden casing is observed to judge the moisture content of the soil. However, this method has the following problems: For example, the measurement of the device is mostly based on the senses (human eyes observe the color change of the casing) to judge the moisture content of the soil, and there is a high test error. At the same time, the device has a low level of digitization. When measuring the moisture content, technicians or surveyors are often required to read the data on site, which poses a great challenge to the timely measurement of the moisture content. At the same time, when observing the moisture content distribution of the roadbed soil, the more sensors are arranged, the more representative and accurate the observed data is. However, measuring the moisture content by the above method will consume a lot of manpower. Therefore, this method has certain limitations in observing the moisture content of the soil, and its applicability for measuring the moisture content of the roadbed section that stretches for several kilometers is low.

[0006] Another example is the patent with announcement number CN112129679B, which discloses a real-time rainfall infiltration status monitoring device for hydraulic geotechnical structures. The device heats the soil through a heating rod. When the soil moisture content is different, its heat conduction capacity is also different. The temperature change before and after the rock and soil are heated is detected by a photometer, the moisture content distribution is estimated, and the soil moisture content is measured by thermodynamic principles. When this method is used to measure the soil moisture content, the soil needs to be heated to a certain temperature before detection can be carried out, which will require supporting power supplies and power facilities. When monitoring the moisture content on the railway roadbed, the conditions are relatively harsh, and the feasibility of using a fixed power supply is low. When part of the roadbed to be measured is in a semi-freeze-thaw zone, when measuring the soil moisture content, the soil needs to be heated during the measurement process, which will destroy the mechanical stability of the soil in the semi-freeze-thaw zone and may cause a certain degree of attenuation of its strength. Therefore, there are certain limitations in using this method.

[0007] For example, the announcement number CN113450542B announced a real-time monitoring system for rock and soil moisture content, which monitors soil moisture content through a nuclear magnetic resonance monitoring device, and transmits data to a database through a data processing and data transmission system, thereby realizing dynamic monitoring and real-time analysis of soil moisture content, and improving the timeliness of monitoring. However, the core component of the moisture content test of this method is a nuclear magnetic resonance instrument, and the working environment of the device is relatively harsh, such as "32±1℃" mentioned in the article, and it has poor adaptability to the harsh natural environment where the roadbed is located. At the same time, the device requires more auxiliary and protective facilities during the measurement process, and there are certain inconveniences in application. At the same time, the cost of the probe rod of the device is relatively high, which is not conducive to the monitoring of the moisture content of the roadbed soil over long distances. Summary of the invention

[0008] The present invention proposes a real-time measurement method for soil moisture content, which solves the problems existing in the traditional drying method and moisture sensor measurement method, such as consuming a large amount of manpower and material resources, low efficiency, high energy consumption, large fluctuations in detection data, easy damage of sensors, high maintenance cost, low degree of digitization, serious lag, and inability to achieve real-time upload.

[0009] The technical solution of this scheme is as follows: A real-time measurement method of soil moisture content includes the following steps: S01. Prepare a test probe, wherein the test probe has four conductive parts, which are arranged at intervals and insulated from each other, and are used to contact the soil. The conductive parts are numbered Q, W, E, and R in the same direction; S03, a constant current I is passed through two adjacent conductive parts, and the voltage U between the two conductive parts without current is measured, and the voltage fluctuation threshold Z is defined according to the test data of the voltage U U ; S05, driving the test probe into the soil, and recording the number of times N the test probe is struck before the conductive member contacts the soil; S05-C, record the number of voltage fluctuations M after the conductive part enters the soil, when the fluctuation value Y of the voltage U in the conductive part is greater than the voltage fluctuation threshold Z U When the number of fluctuations M is recorded, the total number of knocks on the test probe is L = the number of fluctuations M + the number of hits N.

[0010] Optionally, in step S03, the voltage fluctuation threshold Z U The definition method is: record the fluctuation value Y of the voltage U under the stable state of multiple test probes 1 ; Hammer the test probe downward and record the fluctuation value Y of the voltage U during the movement of the test probe 2 , where Y 1 Maximum value < voltage fluctuation threshold Z U <Y 2 The minimum value of .

[0011] Optionally, the method further comprises the steps of: S05-A, alternately generate a constant current I to the conductive parts Q and W QW , a constant current I is generated to the conductive parts E and R ER ; S05-B, a constant current I is generated to the conductive parts Q, W QW When measuring the voltage U at the conductive parts E and R ER , a constant current I is generated to the conductive parts E and R ER When the voltage U at the conductive part Q and W is measured QW .

[0012] Optionally, the method further comprises the steps of: S06, multiple groups I QW and U ER ,I ER and U QW Substitute the value into the soil conductivity ρ calculation formula: ρ = K (U ER / i QW +U QW / i ER ), calculate and obtain multiple groups of different soil conductivity ρ; S07, putting multiple groups of soils with different electrical conductivities ρ into a drying box for drying to obtain the soil moisture content W; S08, the soil moisture content at a distance of H*n from the ground is W Hn The soil moisture content at this point measured by the test probe is W Hn1 , the interference term is denoted as W Hn2 ; Substitute the soil moisture content W into the correction calculation formula: W Hn = WHn1 + W Hn2 .

[0013] Optionally, in step S08, W Hn2 is the soil moisture content and W measured by the front X-stroke and the back X-stroke at the H*n position measured by the test probe Hn1 The mean of the differences is: W Hn2 ={(W （Hn1）-X -W Hn1 )+ (W （Hn1）-(X-1) -W Hn1 )+...+(W （Hn1）-1 -W Hn1 )+(W （Hn1）+1 -W Hn1 )+...+(W （Hn1）+X -W Hn1 )} / 2X.

[0014] Optionally, in step S01, the testing probe further includes: Touch probe; The insulating sleeve is arranged on the probe head, and the four conductive parts are evenly arranged on the insulating sleeve.

[0015] Optionally, the method further comprises the steps of: S04. Measure the diameter d of the conductive part and the height h of the insulating sleeve, and substitute the coefficient K into the calculation formula: K=(1 / d+1 / h)*1 / ln2.

[0016] Optionally, the method further comprises the steps of: S02, inserting the test probe into the soil so that the conductive member contacts the soil; Driving the test probe into the soil in step S02 and step S05 specifically includes: defining one or more probing areas on the roadbed, inserting the test probe into the probing area, or removing the soil in the probing area and inserting the test probe into the removed soil.

[0017] Optionally, the method further comprises the steps of: S10. Insert one or more test probes having at least one insulating part into the roadbed, and make the conductive part on the insulating part contact with the soil, and connect the signal of the moisture content measurement value with the Beidou positioning system. The test probe is also equipped with a photovoltaic system, which provides power to the test probe by setting a solar panel on each test probe or setting a solar base station for multiple test probes.

[0018] Optionally, in step S10, one or more test probes have a plurality of insulating members arranged at intervals, wherein a sleeve is provided around the insulating member away from the probe head, and a diameter of the sleeve at one end away from the probe head is larger than a diameter at one end close to the probe head.

[0019] The working principle and beneficial effects of the present invention are: In the present invention, the distribution of water content inside the roadbed is monitored in real time by combining a self-made test probe with the Beidou navigation system, and the data is transmitted back to the data center in real time. The four conductive members on the test probe are arranged at intervals and insulated from each other to ensure that the measurement of current and voltage is not disturbed and reduce test errors. The test probe with four conductive members is inserted into the soil, and a constant current I is passed through two of the conductive members, and the voltage U of the two adjacent conductive members is measured at the same time. The test probe is hit downward with a through-hammer, and the actual number of voltage fluctuations M is recorded during the movement of the test probe. The principle of recording the number of fluctuations is that when the test probe is stable, the measured values ​​of the constant current I and the voltage U will tend to be stable and will not have large fluctuations. When the through-hammer is used to hammer, the friction between the conductive member and the soil will cause the contact resistance between the conductive member and the soil to change, thereby causing instantaneous changes in current and voltage. By setting a suitable threshold, the small fluctuations during normal measurement and the large changes caused by hammering and displacement can be distinguished. The simultaneous recording of the soil conductivity ρ and the number of knocks can be achieved by recording the number of current or voltage changes exceeding the threshold. By recording the soil conductivity ρ, the soil conductivity ρ is closely related to its water content W. The water in the soil is a good conductive medium. As the soil water content W increases, the soil conductivity ρ usually decreases. This is because the ions (such as salt) in the water molecules can move freely, thereby increasing the conductivity of the soil. Within a certain range, the soil conductivity ρ is a function of the soil water content W. This means that the soil water content W can be inferred by measuring the soil conductivity ρ. At the same time, the soil strength can be evaluated by recording the number of hammer strikes, which reflects the soil's ability to resist penetration. The more hammer strikes, the higher the soil density and the higher the strength; conversely, the fewer hammer strikes, the lower the soil density and the lower the strength. Different types of soil will react differently to the same hammer energy. By recording the number of hammer strikes, the type of soil can be preliminarily determined, such as clay, sand, silt, etc. In the dynamic penetration test, the penetration resistance refers to the number of hammer strikes required per unit depth of the cone head. Penetration resistance is one of the important parameters for evaluating the mechanical properties of soil, and can be used to calculate the bearing capacity and deformation modulus of soil. In road and building construction, dynamic penetration tests are often used to evaluate the compaction effect of fill. By comparing the number of hammer blows in different areas, it can be determined which areas have better compaction effects and which areas need further compaction. The results of the dynamic penetration test can provide important reference data for engineering design. For example, foundation design, roadbed design, etc. all require understanding of the mechanical properties of the soil, and the number of hammer blows is one of the important indicators for evaluating these properties. If the number of hammer blows at a certain point suddenly increases or decreases significantly, it may indicate that there are abnormal conditions at that point, such as weak layers, hard interlayers, etc. Timely detection of these problems helps to take appropriate treatment measures. In summary, this scheme uses a homemade penetration device, combined with the measurement of current and voltage, to achieve the recording of the number of blows, the calculation and correction of soil conductivity, Combined with the dynamic penetration data and the moisture content distribution curve of the joint determination, combined with the roadbed disease and the roadbed settlement form, and combined with the Beidou navigation system, the real-time data feedback is realized, which improves the timeliness of data feedback. According to the existing data, roadbed diseases often repeat at a certain point and occur multiple times, so the demarcation of key monitoring areas is of great significance for the early warning of roadbed diseases. Therefore, multiple test probes are reasonably arranged according to the test requirements (such as test density, etc.), and connected through rods, and the transmission line is placed inside the rod. After the connection is completed, each test probe is connected to the moisture content measurement system at the top, and it is hammered into the roadbed with a through hammer, the accuracy of the test data is observed, and the probe position in the moisture content measurement device is numbered. Combined with the Beidou navigation system and the solar power supply system, the real-time data feedback is realized, which improves the timeliness of data feedback, improves the quality of roadbed soil moisture content monitoring, and specifies the early warning plan and disposal measures in combination with the moisture content distribution. It is suitable for applications in multiple fields.

[0020] At the same time, the test device can be reasonably arranged according to the monitoring needs. Due to its strong durability and other characteristics, its connection lines are mostly placed inside the rod, which has strong antioxidant ability, reduces the interference of the external environment (animals, machinery) on the moisture content test, and has high practicality and the ability to resist changes in the external environment. When a component is damaged, the entire rod can be directly taken out and replaced accordingly, without the need to use methods such as excavation of the roadbed. The replacement is more convenient and simple, and the replacement cost is low. This method not only improves the accuracy and reliability of the measurement, greatly improves the convenience and efficiency, but also provides rich soil information and is suitable for applications in multiple fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The preferred implementation modes will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0022] Figure 1 This is a schematic diagram of real-time measurement of soil moisture content according to the present invention; Figure 2 The soil moisture content detection data of the present invention (the horizontal axis T is the time axis, the vertical axis W is the soil moisture content, -20~-820 is the depth below the ground, the unit is cm); Figure 3 It is a schematic diagram of the dynamic probing of the present invention.

[0023] In the figure: 1. Test probe; 2. Conductive component; 3. Roadbed; 4. Photovoltaic system. DETAILED DESCRIPTION

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0025] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically shown, or only one of them is marked. In this article, "one" not only means "only one", but also means "more than one", and "several" includes "two" and "more than two".

[0026] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0028] Reference Figure 1~Figure 3 , a real-time measurement method for soil moisture content is proposed, which includes the following steps: S01, prepare a test probe 1, wherein the test probe 1 has four conductive members 2, the four conductive members 2 are arranged at intervals and insulated from each other, the conductive members 2 are used to contact the soil, and are numbered Q, W, E, and R in the same direction; S03, a constant current I is passed through two adjacent conductive members 2, and a voltage U is measured between the two conductive members 2 without current, and a voltage fluctuation threshold Z is defined based on the test data of the voltage U. U ; S05, driving the test probe 1 into the soil, and recording the number of times N that the test probe 1 is struck before the conductive member 2 contacts the soil; S05-C, record the number of voltage fluctuations M after the conductive member 2 enters the soil, when the fluctuation value Y of the voltage U in the conductive member 2 is greater than the voltage fluctuation threshold Z U When the number of fluctuations M is recorded, the total number of knocks of the test probe 1 is L = the number of fluctuations M + the number of knocks N.

[0029] In this embodiment, the soil moisture content W is measured by a self-made probing device. The four conductive members 2 on the test probe 1 are arranged at intervals and insulated from each other to ensure that the current and voltage measurements are not disturbed. The test probe 1 with four conductive members 2 is inserted into the soil, and a constant current I is passed through two of the conductive members 2, and the voltage U of the two adjacent conductive members 2 is measured at the same time. The test probe 1 is hit downward with a core hammer, and the actual number of voltage fluctuations M is recorded during the movement of the test probe 1. The principle of recording the number of fluctuations is that when the test probe 1 is stable, the measured values ​​of the constant current I and the voltage U will tend to be stable and will not fluctuate greatly. When the core hammer is used to hammer, the friction between the conductive member 2 and the soil will cause the contact resistance between the conductive member 2 and the soil to change, thereby causing instantaneous changes in current and voltage. By setting a suitable threshold, it is possible to distinguish between small fluctuations during normal measurement and large changes caused by hammering and displacement. The simultaneous recording of the soil conductivity ρ and the number of knocks can be achieved by recording the number of current or voltage changes exceeding the threshold. By recording the soil conductivity ρ, the soil conductivity ρ is closely related to its water content W. The water in the soil is a good conductive medium. As the soil water content W increases, the soil conductivity ρ usually decreases. This is because the ions (such as salt) in the water molecules can move freely, thereby increasing the conductivity of the soil. Within a certain range, the soil conductivity ρ is a function of the soil water content W. This means that the soil water content W can be inferred by measuring the soil conductivity ρ. At the same time, the soil strength can be evaluated by recording the number of hammer strikes, which reflects the soil's ability to resist penetration. The more hammer strikes, the harder the soil and the higher the strength; conversely, the fewer hammer strikes, the softer the soil and the lower the strength. Different types of soil will react differently to the same hammer energy. By recording the number of hammer strikes, the type of soil can be preliminarily determined, such as clay, sand, silt, etc. In the dynamic penetration test, the penetration resistance refers to the number of hammer strikes required per unit depth of the cone head. Penetration resistance is one of the important parameters for evaluating the mechanical properties of soil, and can be used to calculate the bearing capacity and deformation modulus of soil. In road and building construction, dynamic penetration tests are often used to evaluate the compaction effect of fill. By comparing the number of hammer strikes in different areas, it can be determined which areas have better compaction effects and which areas need further compaction. The results of dynamic penetration tests can provide important reference data for engineering design. For example, foundation design, roadbed design, etc. all require understanding of the mechanical properties of soil, and the number of hammer strikes is one of the important indicators for evaluating these properties. If the number of hammer strikes at a certain point suddenly increases or decreases significantly, it may indicate that there are abnormal conditions at that point, such as weak layers, hard interlayers, etc. Timely discovery of these problems helps to take corresponding treatment measures. In summary, this scheme uses a homemade penetration device, combined with current and voltage measurements, to record the number of strikes, calculate and correct soil conductivity, and combines the Beidou navigation system to achieve real-time data feedback, thereby improving the timeliness of data feedback.This method not only improves the accuracy and reliability of measurement, greatly improves convenience and efficiency, but also provides rich soil information and is suitable for applications in multiple fields.

[0030] Furthermore, the method further comprises the following steps: In step S03, the voltage fluctuation threshold Z U The definition method is: record the fluctuation value Y of the voltage U of multiple test probes 1 in the stable state 1 ; Hammer the test probe 1 downward and record the fluctuation value Y of the voltage U of the test probe 1 during the movement 2 , where Y 1 Maximum value < voltage fluctuation threshold Z U <Y 2 The minimum value of .

[0031] In this embodiment, in order to accurately distinguish between the small fluctuations during normal measurement and the large changes caused by hammering and displacement, it is necessary to determine the current threshold Z I Or voltage fluctuation threshold Z U In this solution, it is preferred to use the voltage fluctuation threshold Z U Before re-probing, insert the test probe 1 into the soil, pass a constant current I, and record the fluctuation value Y of the voltage U of multiple groups of test probes 1 in a stable state. 1 Then, the test probe 1 is struck and the fluctuation value Y of the voltage U during the movement is recorded. 2 , the purpose of which is to obtain the voltage fluctuation threshold Z U , that is, when the current or voltage fluctuation value is greater than a certain value, it is caused by the hammer hitting the test probe 1, and when the voltage or current fluctuation value is less than a certain value, it may be a normal fluctuation value in the stable measurement process. Therefore, the voltage fluctuation threshold Z U You need to choose a value between the maximum fluctuation value in the stable state and the minimum fluctuation value in the moving state, that is, Y 1 Maximum value < voltage fluctuation threshold Z U <Y 2 The minimum value of the voltage fluctuation threshold Z is determined by U , can accurately distinguish between small fluctuations during normal measurement and large changes caused by hammering and displacement, thereby improving the accuracy and reliability of measurement. Recording the actual number of fluctuations M can accurately reflect the number of movements of the test probe 1 and avoid measurement errors caused by misjudgment.

[0032] In step S01 , the test probe 1 further includes: a probe head; an insulating sleeve, the insulating sleeve is arranged on the probe head, and four conductive members 2 are evenly arranged on the insulating sleeve.

[0033] In this embodiment, there are four conductive members 2, which are evenly spaced, that is, 90° apart from each other. Such an arrangement can form a more uniform electric field distribution in the soil. In the electric field simulation experiment, the electric field uniformity coefficient under this arrangement is as high as 0.92. Compared with the unevenly arranged conductive members 2, the standard deviation of the test results is reduced by at least 10%, so that the conductivity of the soil can be measured more accurately, and more accurate water content data can be obtained. Preferably, only the end of the conductive member 2 is exposed for contact with the soil. The end of the conductive member 2 is flush with the surrounding side of the insulating sleeve to avoid interference with the soil and damage to the conductive member 2. If the conductive member 2 extends out of the insulating sleeve and interferes with the soil and has a large degree of friction, the surface of the conductive member 2 will be more prone to wear and the surface roughness will increase. The increase in surface roughness will lead to an increase in contact resistance, affecting the conductive performance. At the same time, friction may also cause soil particles to adhere to the surface of the conductive member 2, causing pollution, further increasing the contact resistance. After experimental observation, after a long period of friction, the wear degree of the surface of the conductive part 2 may reach 0.1mm to 0.2mm, which will reduce the conductivity by about 10% to 20%, resulting in a gradual increase in the conductivity measurement error, reduced stability of the test results, and reduced repeatability of the test results. Considering that the exposed electrode part may still cause uneven electric field distribution, affecting the accuracy of the test results, and the exposed part is easily affected by the surrounding environment (such as humidity and temperature), which may cause unstable test results, the main part of the conductive part 2 is set inside the insulating sleeve, and its role is that the insulating sleeve can protect the conductive part 2 from corrosion and wear. The entire conductive part 2 is covered by the insulating sleeve, which can significantly reduce the interference of uneven electric field distribution on the test and improve the accuracy of the test results.

[0034] Furthermore, the method further comprises the step of: S06, combining the plurality of groups I QW and U ER ,I ER and U QW Substitute the value into the soil conductivity ρ calculation formula: ρ = K (U ER / i QW +U QW / i ER ), calculate and obtain multiple groups of different soil conductivity ρ; S07, putting multiple groups of soils with different electrical conductivities ρ into a drying box for drying to obtain the soil moisture content W; S08, the soil moisture content at a distance of H*n from the ground is W Hn The soil moisture content at this point measured by the test probe (1) is W Hn1 , the interference term is denoted as W Hn2 ; Substitute the soil moisture content W into the correction calculation formula: W Hn = W Hn1 + W Hn2 .

[0035] In step S08, W Hn2 is the soil moisture content and W measured by the front X-stroke and the back X-stroke at the H*n position measured by the test probe 1 Hn1 The mean of the differences is: W Hn2 ={(W （Hn1）-X -W Hn1 )+ (W （Hn1）-(X-1) -W Hn1 )+...+(W （Hn1）-1 -W Hn1 )+(W （Hn1）+1 -W Hn1 )+...+(W （Hn1）+X -W Hn1 )} / 2X.

[0036] S09. Substitute the soil moisture content W and soil conductivity ρ into the formula: W=Aρ B , calculate the fitting parameters A and B.

[0037] In this embodiment, considering that the method used to detect the moisture content of the soil is mainly obtained by measuring and calculating the current and voltage, it is necessary to complete the calculation of the fitting parameters A and B in the formula; Specifically, take H as 15cm, X as 3, and n as 2 as an example: The soil moisture content W at a distance of 30 cm from the ground is W 30 , the soil moisture content W is measured by the touch test probe 1 as W 301 , the interference term of the system on the test results is reduced by the calculation algorithm and recorded as W 302 , W 302 The moisture content and W of the first 3 hits and the last 3 hits at the 30 cm position 301 The mean of the difference in moisture content measured at the location is calculated as: W 302 ={(W （301）-3 -W 301 )+(W （301）-2 -W 301 )+(W （301）-1 -W 301 )+(W （301）+1 -W 301 )+(W （301）+2 -W 301 )+(W （301）+3 -W 301 )} / 6.

[0038] According to the requirements of the Geotechnical Investigation Code, the number of times the cone head penetrates 30cm into the soil should be recorded, so a marking line is drawn every 30cm on the test probe 1. In order to meet the test accuracy requirements of the moisture content of the roadbed 3, the height of the roadbed 3 is often as high as 7-10m, so the moisture content is measured every 15cm, which can basically meet the accuracy requirements of drawing the moisture content curve with depth. Therefore, the following moisture content algorithm is illustrated by the above embodiment. In order to reduce the interference of system errors on the test results, the moisture content calculation method is improved.

[0039] Furthermore, driving the test probe 1 into the soil in step S02 and step S05 is specifically as follows: defining one or more probing areas on the roadbed 3, inserting the test probe 1 into the probing area, or removing the soil in the probing area and inserting the test probe 1 into the removed soil.

[0040] In this embodiment, in the process of measuring soil conductivity and inferring the position of the roadbed 3 with different soil moisture contents through the soil conductivity, there are two ways. One is to directly mark the probing area on the roadbed 3 and insert the test probe 1. The other is to remove the soil in the probing area and use the test probe 1 to insert the removed soil. The purpose is to obtain multiple groups of soil conductivity ρ with different values ​​to improve the quality of drawing the relationship curve between soil conductivity ρ and soil moisture content W.

[0041] Furthermore, the method also includes the following steps: S10, inserting one or more test probes 1 having multiple insulating parts into the roadbed 3, and making the conductive parts 2 on the insulating parts contact with the soil, and connecting the signal of the moisture content measurement value with the Beidou positioning system. The test probe 1 is also equipped with a photovoltaic system 4, which provides electrical energy to the test probe 1 by arranging solar panels on each test probe 1 or arranging solar base stations for multiple test probes 1.

[0042] In this embodiment, according to the measurement requirements, one or more test probes 1 having insulating parts and conductive parts 2 are connected in sequence through connecting rods and numbered. The test probe 1 is located at the connection of the rods, and the test probe 1 is connected to the soil moisture test system at the top through a wire. Several test probes 1, connecting rods and soil moisture test systems form a test unit. According to the test requirements, a single or multiple test units are arranged.

[0043] The test unit can also be equipped with a photovoltaic system 4 and a power storage system, which can provide power support for a single or several test units. At the same time, the setting of the power storage system also provides power support for measurements at night and during non-lighting times such as rain, which is convenient for monitoring the internal moisture distribution of the roadbed 3.

[0044] Preferably, several similar test units can be grouped into a test group, each test group is equipped with a Beidou navigation (GNSS) device, and the coordinate positions of the test units in the test group are numbered. Through the numbering, the moisture content distribution pattern of the roadbed 3 section in the test group can be monitored in the data center.

[0045] Furthermore, in step S10, one or more test probes 1 have a plurality of insulating members arranged at intervals, wherein a sleeve is provided around the insulating member away from the probe head, and the diameter of the sleeve at one end away from the probe head is larger than the diameter at one end close to the probe head.

[0046] In this embodiment, the kit is in the shape of a truncated cone, and its function is to enable the conductive member 2 located at the top to better contact with the soil to avoid the situation of no contact or contact short circuit.

[0047] The comprehensive working steps are as follows: Get the voltage fluctuation threshold Z U Specifically, define an area P and take the following steps in P: S01. Prepare a test probe 1, wherein the test probe 1 has four conductive members 2, which are arranged at intervals and insulated from each other, and are used to contact the soil; the test probe 1 also includes: a probe head; an insulating sleeve, which is arranged on the probe head, and the four conductive members 2 are evenly arranged at intervals on the insulating sleeve, and are numbered Q, W, E, and R in the same direction; S02, inserting the test probe 1 into the area P, or removing the soil in the area P, and inserting the test probe 1 into the removed soil, so that the conductive element 2 contacts the soil; S03, a constant current I is passed through two adjacent conductive members 2, and a voltage U is measured between the two conductive members 2 without current, and a voltage fluctuation threshold Z is defined based on the test data of the voltage U. U Specifically: record the fluctuation value Y of the voltage U of multiple test probes 1 in a stable state 1 ; Hammer the test probe 1 downward and record the fluctuation value Y of the voltage U of the test probe 1 during the movement 2 , where Y 1 Maximum value < voltage fluctuation threshold Z U <Y 2 The minimum value of .

[0048] It should be noted that in this process, Figure 3 As shown, the test probe 1 used is only provided with a single contact probe, a single insulating sleeve and corresponding four conductive members 2 .

[0049] The total number of knocks L is recorded and the soil moisture content W is obtained. Specifically, one or more probe areas N are defined on the roadbed 3, and the following steps are performed in the probe area N: S04. Measure the diameter d of the conductive part 2 and the height h of the insulating sleeve, and substitute the coefficient K into the calculation formula: K=(1 / d+1 / h)*1 / ln2; K is a calculation coefficient related to soil type. After field tests and numerical simulation calculations, it is found that the appropriate value for this section of roadbed 3 (mainly silt soil) is 1.85. Soil conductivity ρ calculation formula: ρ=K(U ER / i QW +U QW / i ER ), multiple groups of different soil conductivity ρ are calculated.

[0050] S05, insert the test probe 1 into the probing area N, or remove the soil in the probing area N, insert the test probe 1 into the removed soil, and record the number of times N that the test probe 1 is struck before the conductive member 2 contacts the soil; S05-A, alternately generate a constant current I to the conductive member 2Q and the conductive member 2W QW , a constant current I is generated to the conductive member 2E and the conductive member 2R ER ; S05-B, a constant current I is generated to the conductive parts 2Q and 2W QW When the voltage U between the conductive part 2E and the conductive part 2R is measured ER , a constant current I is generated to the conductive member 2E and the conductive member 2R ER When the voltage U between the conductive part 2Q and the conductive part 2W is measured QW ; S05-C, record the number of voltage fluctuations M after the conductive member 2 enters the soil, when the fluctuation value Y of the voltage U in the conductive member 2 is greater than the voltage fluctuation threshold Z U When the test probe 1 is directly inserted into the soil, so that the conductive component 2 is in direct contact with the soil, M is the total number of strikes (that is, N is 0). The number of hammer strikes is recorded based on this, and the soil density and mechanical properties and other data are determined.

[0051] S06, multiple groups I QW and U ER ,I ER and U QW Substitute the value into the soil conductivity ρ calculation formula: ρ = K (U ER / i QW +U QW / i ER ), calculate and obtain multiple groups of different soil conductivity ρ; Among them, S05-A, S05-B, and S05-C occur synchronously with S05; S07, putting multiple groups of soils with different electrical conductivities ρ into a drying box for drying to obtain the soil moisture content W; S08, the soil moisture content at a distance of H*n from the ground is W Hn The soil moisture content at this point measured by the test probe 1 is W Hn1 , the interference term is denoted as W Hn2 ; Substitute the soil moisture content W into the correction calculation formula: W Hn = W Hn1 + W Hn2 .

[0052] W Hn2 is the soil moisture content and W measured by the front X-stroke and the back X-stroke at the H*n position measured by the test probe 1 Hn1 The mean of the differences is: W Hn2 ={(W （Hn1）-X -W Hn1 )+ (W （Hn1）-(X-1) -W Hn1 )+...+(W （Hn1）-1 -W Hn1 )+(W （Hn1）+1 -W Hn1 )+...+(W （Hn1）+X -W Hn1 )} / 2X.

[0053] The moisture content calculation method can basically eliminate the systematic error of the moisture content measurement at the specified location. The calculation method and operation logic of the measured moisture content are encoded into the moisture content test system through the encoder. The moisture content test system consists of several single-chip microcomputers containing digital processing chips and electrical signal processing chips and power supply modules, which can realize data collection and processing, and can export test data to the specified location.

[0054] S09. Substitute the soil moisture content W and soil conductivity ρ into the formula: W=Aρ B , calculate the fitting parameters A and B; Parameters A and B are determined and input into the soil moisture content test system. The output value of the test system in the test unit is the soil moisture content W at each position inside the roadbed 3.

[0055] One or more detection areas T are defined on the roadbed 3, and the following steps are performed in the detection area T: S10, inserting one or more test probes 1 having multiple insulating parts into the roadbed 3, and making the conductive parts 2 on the insulating parts contact with the soil, and connecting the signal of the moisture content measurement value with the Beidou positioning system, the test probes 1 are also equipped with a photovoltaic system 4, which provides power to the test probes 1 by arranging solar panels on each test probe 1 or arranging solar base stations for multiple test probes 1; In S10, each test probe 1 is provided with a plurality of insulating members arranged at intervals, such as Figure 1 As shown, a sleeve is provided on the peripheral side of the insulating member away from the contact probe, and the diameter of the sleeve at one end away from the contact probe is larger than the diameter at one end close to the contact probe.

[0056] In the above scheme, S stands for step and the numbers are the order of operations.

[0057] In summary, combined with this test method, the problem of accurate calculation of water content and preliminary prediction of soil properties in the process of soil density test is effectively solved. Several test probes 1 are connected by rods to form test units, and several test units are arranged in the roadbed. The water content test data is realized by connecting the device with the Beidou signal, and the soil water content data collected by the test unit can be quickly transmitted to the data center to ensure the timely update of the monitoring data. The low latency characteristic of the Beidou system makes the time from data collection to transmission and then to data center processing extremely short, providing a strong guarantee for real-time monitoring. This enables monitoring personnel to quickly obtain the latest water content information and take timely countermeasures. The Beidou system can provide high-precision positioning services at the sub-meter level or even the centimeter level to ensure that the location information of each test unit is accurate. This high-precision positioning helps to accurately calibrate the position of the test unit, which is convenient for subsequent data analysis and processing. Each test unit is assigned a coordinate position number. Through these numbers, the data center can accurately locate the specific test unit and monitor its water content status in real time. This numbering method simplifies the data management and analysis process and improves monitoring efficiency. The BeiDou system supports signal transmission in multiple frequency bands, which improves the stability and reliability of positioning. Even in complex environmental conditions, such as mountainous areas, forests or densely populated urban areas, the BeiDou system can maintain high-precision positioning and data transmission. The BeiDou system can be integrated with a variety of sensors such as soil moisture sensors and temperature sensors to form a comprehensive monitoring network. Through the high-precision positioning and real-time data transmission provided by the BeiDou system, comprehensive monitoring of multiple parameters such as soil moisture content and temperature can be achieved. The data transmitted back by the BeiDou system can be visualized in the data center to generate a real-time moisture content distribution map. This helps monitoring personnel to intuitively understand the moisture content status of the roadbed and discover potential risk points in a timely manner. The BeiDou system is a global satellite navigation system independently developed by China, with completely independent intellectual property rights, not affected by external factors, ensuring the safety and controllability of the system.

[0058] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for real-time measurement of soil moisture content, characterized in that: The following steps are involved: S01. preparing a test probe (1), wherein the test probe (1) has four conductive parts (2), the four conductive parts (2) are arranged at intervals and insulated from each other, the conductive parts (2) are used to contact the soil, and are numbered Q, W, E, and R in the same direction; S03, passing a constant current I through two adjacent conductive members (2), and measuring a voltage U between the two conductive members (2) without passing the current, and defining a voltage fluctuation threshold Z according to the test data of the voltage U U ; S05, driving the test probe (1) into the soil, and recording the number of times N that the test probe (1) is struck before the conductive member (2) comes into contact with the soil; S05-C, record the number of voltage fluctuations M after the conductive member (2) enters the soil, when the fluctuation value Y of the voltage U in the conductive member (2) is greater than the voltage fluctuation threshold Z U When the number of fluctuations M is recorded, the total number of knocks of the test probe (1) is L = the number of fluctuations M + the number of knocks N.

2. A method for real-time measurement of soil moisture content according to claim 1, characterized in that: In the step S03, the voltage fluctuation threshold Z U is defined as follows: record the fluctuation value Y1 of the voltage U in the stable state of multiple groups of test probes (1); hammer the test probe (1) downward, and record the fluctuation value Y2 of the voltage U during the movement of the test probe (1), where the maximum value of Y1 < the voltage fluctuation threshold Z U < the minimum value of Y2.

3. A method for real-time measurement of soil moisture content according to claim 2, characterized in that: Also includes the steps: S05-A, alternately generate a constant current I to the conductive parts (2) Q, W QW , a constant current I is generated to the conductive member (2) E, R ER ; S05-B, a constant current I is generated to the conductive member (2) Q and the conductive member (2) W QW When the voltage U between the conductive part (2) E and the conductive part (2) R is measured ER , a constant current I is generated to the conductive member (2) E and the conductive member (2) R ER When the voltage U between the conductive part (2) Q and the conductive part (2) W is measured QW .

4. A method for real-time measurement of soil moisture content according to claim 3, characterized in that: Also includes the steps: S06, multiple groups I QW and U ER ,I ER and U QW Substitute the value into the soil conductivity ρ calculation formula: ρ = K (U ER / i QW +U QW / i ER ), calculate and obtain multiple groups of different soil conductivity ρ; S07, putting multiple groups of soils with different electrical conductivities ρ into a drying box for drying to obtain the soil moisture content W; S08, the soil moisture content at a distance of H*n from the ground is W Hn The soil moisture content at this point measured by the test probe (1) is W Hn1 , the interference term is denoted as W Hn2 ; Substitute the soil moisture content W into the correction calculation formula: W Hn = W Hn1 + W Hn2 .

5. A method for real-time measurement of soil moisture content according to claim 4, characterized in that: In step S08, W Hn2 is the soil moisture content and W measured by the front X-stroke and the back X-stroke at the H*n position measured by the test probe (1) Hn1 The mean of the differences is: IN Hn2 ={(In （Hn1）-X - IN Hn1 )+ (In （Hn1）-(X-1) - IN Hn1 )+...+(In （Hn1）-1 - IN Hn1 )+(In （Hn1）+1 - IN Hn1 )+...+(In （Hn1）+X - IN Hn1 )} / 2X。 6. A method for real-time measurement of soil moisture content according to claim 1, characterized in that: In the step S01, the testing probe (1) further comprises: Touch probe; An insulating sleeve is arranged on the probe head, and four conductive members (2) are evenly spaced and arranged on the insulating sleeve.

7. A method for real-time measurement of soil moisture content according to claim 1, characterized in that: Also includes the steps: S04. Measure the diameter d of the conductive part (2) and the height h of the insulating sleeve, and substitute the coefficient K into the calculation formula: K = (1 / d + 1 / h) * 1 / ln2.

8. The method for real-time measurement of soil moisture content according to claim 1, characterized in that: Also includes the steps: S02, inserting the test probe (1) into the soil so that the conductive member (2) contacts the soil; The steps S02 and S05 of driving the test probe (1) into the soil specifically include: defining one or more probing areas on the roadbed (3), inserting the test probe (1) into the probing area, or removing the soil in the probing area and inserting the test probe (1) into the removed soil.

9. The method for real-time measurement of soil moisture content according to claim 1, characterized in that: Also includes the steps: S10, inserting one or more test probes (1) having multiple insulating parts into the roadbed (3), and making the conductive parts (2) on the insulating parts contact with the soil, and connecting the signal of the water content measurement value to the Beidou positioning system, the test probe (1) is also equipped with a photovoltaic system (4), and provides electric energy to the test probe (1) by arranging a solar panel on each test probe (1) or arranging a solar base station for multiple test probes (1).

10. A method for real-time measurement of soil moisture content according to claim 9, characterized in that: In the step S10, one or more test probes (1) are provided with a plurality of insulating parts arranged at intervals, wherein a sleeve is provided around the insulating part away from the probe head, and the diameter of the sleeve at one end away from the probe head is larger than the diameter at one end close to the probe head.

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