Single-column soil moisture content testing method

Abstract

The invention discloses a single-column soil moisture content testing method, belongs to the technical field of soil moisture content testing, and solves the problem that an existing soil moisture content detection method cannot accurately prevent geological disasters. According to the method, measurement data including measurement impedance modulus and measurement phase in a monitored soil layer are obtained by utilizing multiple groups of measurement electrodes in a soil test column, and an impedance modulus correlation coefficient and a phase correlation coefficient between the measurement data and calibration data are calculated to obtain a comprehensive correlation coefficient; the calibrated soil moisture content distribution soil layer closest to the monitored soil layer is judged at the same time by combining the impedance modulus and the phase, the calibrated experimental soil layer has higher robustness, and even if the environmental condition changes, the strategy can be quickly adjusted by comparing the calibrated data, so that the continuity and stability of monitoring work are ensured, and the accuracy of monitoring is improved. And an expert can conveniently evaluate an accurate geological disaster early warning level.

Description

Technical Field

[0001] The invention relates to the technical field of soil moisture content testing, and in particular to a single-column soil moisture content testing method. Background Art

[0002] Soil moisture is closely related to geological disasters. High moisture content will reduce the shear strength of the soil and increase the weight of the soil, thereby increasing the risk of landslides and mudslides. At the same time, changes in soil moisture content may also lead to ground subsidence and soil collapse, especially in soft soil areas and geological structures with cavities. Therefore, accurate monitoring of soil moisture is of great significance for the early warning and prevention of geological disasters.

[0003] At present, most of the existing technologies assess the risk of geological disasters by directly measuring the moisture content of the soil. For example, the invention patent with the announcement number CN111537567B discloses a tube-needle soil moisture detection method, which includes a detector body and a detection rod, the lower end of the detector body is connected to the detection rod, the upper surface of the detector body is provided with a control panel, the lower end of the detection rod is designed in a sharp form, the outer wall of the lower end of the detection rod is embedded with a high-frequency electrode sheet distributed in a ring shape, the surface of the high-frequency electrode sheet is kept in contact with the outer wall of the lower end of the detection rod, the outer wall of the lower end of the detection rod is embedded with a detection port, the detection port is embedded with a protective net and a permeable membrane, the lower end of the detection rod is provided with symmetrically distributed high-frequency electrode contacts, and the detector body includes a power module, a high-frequency voltage generator, a voltage measuring device and a microprocessor. The invention ionizes the water in the soil through the high-frequency electrode sheet, and measures the moisture content quickly and effectively by detecting the conductivity between the high-frequency electrode contacts. However, the moisture content information of the soil cannot be accurately reflected directly through the conductivity, so it is impossible to accurately warn of geological disasters. Summary of the invention

[0004] In view of the above problems in the prior art, the present invention provides a single-column soil moisture content testing method, which solves the problem that the existing soil moisture content detection method cannot accurately prevent geological disasters.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A single-column soil moisture content testing method is provided, comprising the steps of: S1. Install the soil test column in the monitoring soil layer; wherein the soil test column is provided with Each soil electrode is electrically connected to four measurement interfaces in the measurement circuit through four multi-way switches. is a natural number greater than or equal to 4; S2. Place the soil in the test column The soil electrodes are sorted and numbered respectively, and grouped into groups of 4 adjacent soil electrodes. Soil electrodes are divided into A set of measuring electrodes; S3. The measurement data of all the measurement electrodes in the monitored soil layer at different characteristic frequencies are obtained through the measurement circuit. The measurement data include and ;in, For the The measuring electrodes are The measured impedance modulus obtained at the characteristic frequency is For the The measuring electrodes are The measured phase obtained at the characteristic frequency; S4, calculating the correlation coefficient between the measured data and the calibration data; The calibration data includes and , For the Calibrated soil moisture distribution in soil layer The measuring electrodes are The calibrated impedance modulus obtained by the characteristic frequency; For the Calibrated soil moisture distribution in the soil layer The measuring electrodes are The calibration phase obtained at the characteristic frequency; the correlation coefficient includes , and , For the The soil moisture content of the calibrated soil is distributed in the soil layer and Impedance modulus correlation coefficient between ; For the The soil moisture content of the calibrated soil is distributed in the soil layer and The phase correlation coefficient between For the The comprehensive correlation coefficient between the calibrated soil moisture distribution layer and the measured data is calculated by and Calculate and obtain; S5. Get The maximum value in , will be The corresponding calibrated soil moisture distribution soil layer is used as the actual soil moisture distribution soil layer of the monitoring soil layer; S6. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

[0006] In this scheme, multiple groups of measuring electrodes in the soil test column are used to obtain the measurement data of the monitoring soil layer including the measurement impedance mode and the measurement phase, and the impedance mode correlation coefficient and phase correlation coefficient between the measurement and calibration data are calculated and the comprehensive correlation coefficient is obtained. The calibration soil moisture distribution layer closest to the monitoring soil layer is determined by combining the impedance mode and phase. The calibration soil moisture distribution layer is the benchmark value set for the calibration experiment. Considering the complex and changeable conditions of the actual monitoring soil layer, the calibration experiment soil layer has stronger robustness. Even when the environmental conditions change, the strategy can be quickly adjusted by comparing the calibration data to ensure the continuity and stability of the monitoring work, so as to facilitate experts to assess the accurate geological disaster warning level. Among them, the impedance mode refers to the absolute value of the complex impedance, which represents the overall resistance encountered when the current passes through the medium. When the moisture in the soil increases, the impedance mode decreases due to the high dielectric constant of water; the phase refers to the phase difference between the voltage and the current, reflecting the capacitive and inductive components of the medium. The change in water content not only changes the resistivity of the soil, but also affects its capacitance characteristics, thereby changing the phase. As the moisture content increases, the capacitance effect of the soil increases, resulting in an increase in the phase. The combination of impedance mode and phase can better reflect the moisture content of the soil than the single conductivity.

[0007] Furthermore, each soil test column includes a cylindrical shell, the bottom of the shell is a conical structure, a top cover is arranged on the top of the shell, a filling layer is arranged inside the shell, an electrode sandwich is arranged between the inner wall of the shell and the outer wall of the filling layer, and a Soil electrodes, One end of each soil electrode passes through multiple measuring holes on the shell to contact the soil. The other end of each soil electrode is electrically connected to the measurement circuit located on the filling layer through the electrode connection line. The soil test column is easy to install and maintain, ensuring the stability and repeatability of the measurement results.

[0008] Furthermore, a plurality of guide grooves are provided on the inner wall of the housing in the height direction, and a flange is provided on the outer wall of the filling layer to slide with the plurality of guide grooves. The design of the guide grooves and the flange enables the filling layer to slide up and down in the housing without rotating, thereby ensuring the consistency of the position of the soil electrode, improving the measurement accuracy, helping to reduce the error caused by the movement of the device, and enhancing the reliability of the test results.

[0009] Furthermore, a plurality of fixing holes for the lock buckles to pass through are provided on the outer wall of the conical structure at the bottom of the shell, and a plurality of guide holes are vertically provided inside the filling layer. The bottoms of the plurality of guide holes are bent and connected to the plurality of fixing holes respectively, and the tips of the plurality of lock buckles enter the plurality of guide holes respectively and drill out from the plurality of fixing holes into the soil. The design of the fixing holes on the outer wall of the conical structure and the internal guide holes and lock buckles enables the entire device to be firmly embedded in the soil and remain stable even under soft or slippery surface conditions. For long-term monitoring, the lock buckle can prevent data deviation caused by equipment displacement.

[0010] Furthermore, the multiple measuring holes on the housing are evenly divided into multiple layers along the height direction, and the multiple measuring holes on each layer are distributed in a circular pattern. The measuring holes are evenly layered and distributed in a circular pattern along the height direction, which ensures the consistency of the soil contact area of ​​each electrode, thereby improving the comparability between the soil moisture content measurement values ​​at different depths. Such a layout also facilitates the effective contact between the electrode and the soil, further improving the measurement accuracy.

[0011] Furthermore, a fixing plate for fixing the measuring circuit with bolts is arranged on the top of the filling layer, and a connecting wire through-hole for passing a plurality of electrode connecting wires is opened in the middle of the fixing plate.

[0012] Furthermore, the measurement circuit includes four measurement interfaces, which are respectively a first measurement interface, a second measurement interface, a third measurement interface, and a fourth measurement interface electrically connected to four multi-way switches; the first measurement interface is electrically connected to a resistor, a sine signal generator, and a fourth measurement interface in sequence, and a resistor voltage amplifier electrically connected to a resistor voltage analog-to-digital converter is connected in parallel to the resistor, and the resistor voltage analog-to-digital converter is electrically connected to a microprocessor; the sine signal generator is electrically connected to the microprocessor; the second measurement interface and the third measurement interface are both electrically connected to a soil voltage amplifier, and the soil voltage amplifier is electrically connected to the microprocessor through a soil voltage analog-to-digital converter; the microprocessor is connected to a remote monitoring terminal signal through a communication interface. The measurement circuit can simultaneously obtain the resistor voltage and soil voltage information, providing a basis for calculating the impedance module. The use of the microprocessor and the remote monitoring terminal realizes the automatic processing and real-time transmission of data, greatly improving work efficiency.

[0013] Further, and The calculation method comprises the steps of: S3.1, set the frequency of the sine signal generator to the first The sampling frequencies of the soil voltage analog-to-digital converter and the resistance voltage analog-to-digital converter are set to The characteristic frequency times;; S3.2, respectively obtain The output data of the soil voltage analog-to-digital converter and the resistance voltage analog-to-digital converter are connected to the 100-pole measuring electrode. and , and calculate 100 and The absolute deviation value of and Deviation value of S3.3 Calculation and ;

[0014]

[0015] in, For 100 The sum of the absolute deviations of For 100 The sum of the absolute deviations of For 100 The sequence number of the negative zero crossing point in the deviation value; For 100 The sequence number of the negative zero crossing point in the deviation value.

[0016] In this scheme, by setting the output frequency of the sine signal generator and the sampling frequency of the analog-to-digital converter, the impedance modulus is calculated based on the absolute deviation value of a large number of sample points, thereby increasing the amount of data collection, reducing the impact of random errors, and improving the accuracy of impedance modulus calculation. This scheme uses the negative zero-crossing point number to determine the phase. By analyzing a large number of sample points, a more accurate phase can be obtained, and different types of soil media can be easily distinguished.

[0017] Furthermore, the characteristic frequency includes impedance mode characteristic frequencies and phase characteristic frequencies corresponding to a plurality of calibrated soil moisture distribution soil layers, and the method for obtaining the impedance mode characteristic frequency and phase characteristic frequency in each calibrated soil moisture distribution soil layer is: The soil test column is installed in the soil layer corresponding to the soil moisture distribution, and the impedance mode mean square error and phase mean square error of all combinations of measuring electrodes at different frequencies are obtained. The frequency corresponding to the maximum value of all impedance mode mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer, and the frequency corresponding to the maximum value of all phase mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer.

[0018] In this scheme, by measuring the impedance mode mean square error and phase mean square error of all combinations of measuring electrodes at different frequencies and selecting the frequency corresponding to the maximum mean square error as the characteristic frequency, the optimal operating frequency that reflects the change in soil moisture content can be determined more accurately. This helps to improve the accuracy and reliability of subsequent soil moisture monitoring. At the same time, by determining the optimal impedance mode characteristic frequency and phase characteristic frequency, it can help adjust the frequency of the sinusoidal signal generator in the measurement circuit, so that the equipment can operate within the most sensitive frequency range, thereby obtaining more accurate data. Based on this, changes in soil moisture content can be discovered earlier and more accurately, which is particularly important for early warning of geological disasters.

[0019] Further, The calculation method is: =

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] in, and Respectively The impedance modulus average and phase average of all combined measuring electrodes in the soil layer of the calibrated soil moisture distribution; is the total number of characteristic frequencies; K is the number of combinations of all measuring electrodes ; and They are and The average value of .

[0027] This scheme uses two parameters, impedance mode and phase, for comprehensive analysis, which can not only capture the changes in soil resistivity, but also reflect the influence of soil capacitance characteristics, which helps to monitor soil moisture content and its changing trends more comprehensively and reliably.

[0028] The invention discloses a single-column soil moisture content testing method, which has the following beneficial effects: The present invention utilizes multiple groups of measuring electrodes in a soil test column to obtain measurement data including measurement impedance mode and measurement phase in the monitored soil layer, and calculates the impedance mode correlation coefficient and phase correlation coefficient between the measured and calibrated data to obtain a comprehensive correlation coefficient. By combining the impedance mode and phase, the calibrated soil moisture distribution layer closest to the monitored soil layer is simultaneously judged. The calibrated experimental soil layer has stronger robustness. Even when environmental conditions change, the strategy can be quickly adjusted by comparing the calibration data, thereby ensuring the continuity and stability of the monitoring work, and facilitating experts to assess an accurate geological disaster warning level. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the soil test column; Figure 2 is a front view of the housing; Figure 3 is a schematic cross-sectional view of the housing; Figure 4 Schematic diagram of the structure of the electrode sandwich; Figure 5 is a schematic diagram of the soil electrode; Figure 6 It is a top view of the filling layer; Figure 7 is the internal schematic diagram of the filling layer; Figure 8 is a top view of the fixed plate; Fig. 9 It is a connection diagram of the electrode connector and the measuring circuit; Fig.10 This is the connection diagram of the measurement circuit; Fig.11 It is a schematic diagram of the composition of a multi-way switch; Fig.12 It is a structural schematic diagram of a sinusoidal signal generator; Fig.13 It is a schematic diagram of the structure of the soil voltage amplifier and the resistance voltage amplifier; Fig.14 is a schematic diagram of the structure of a microprocessor; Wherein: 1. shell; 2. electrode sandwich; 22. soil electrode; 23. electrode connecting wire; 24. conductor; 30. filling layer; 40. fixing plate; 41. connecting wire perforation; 5. top cover; 6. circuit board; 101. electrode connector; 102. connecting cable; 103. multi-way switch; 104. measuring circuit; 105. data acquisition server; 116-1. first measuring interface; 116-2. second measuring interface; 116-3. third measuring interface; 116-4. fourth measuring interface; 117. soil voltage amplifier; 118. resistor; 119. sinusoidal signal generator; 120. resistor voltage amplifier; 121. soil voltage analog-to-digital converter; 122. resistor voltage analog-to-digital converter; 123. microprocessor; 124. communication interface. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0031] refer to Figure 1 This embodiment provides a single-column soil moisture testing method, the purpose of which is to solve the problem that the existing soil moisture detection method cannot prevent geological disasters. It is demonstrated in detail below.

[0032] A single-column soil moisture content testing method comprises the following steps: S1. Install the soil test column in the monitoring soil layer. Figure 1 and Fig. 9 , where each soil test column is equipped with The soil electrodes 22 are electrically connected to the four measurement interfaces in the measurement circuit 104 through four multi-way switches 103, is a natural number greater than or equal to 4.

[0033] S2. Place the soil in the test column The soil electrodes 22 are sorted and numbered, and four adjacent soil electrodes 22 are grouped into a group. Soil electrodes 22 divided into Set of measuring electrodes.

[0034] S3, the measurement data of all the measurement electrodes in the monitored soil layer at different characteristic frequencies are obtained through the measurement circuit 104, and the measurement data include and ;in, For the The measuring electrodes are The measured impedance modulus obtained at the characteristic frequency is For the The measuring electrodes are The measured phase is obtained at a characteristic frequency.

[0035] S4. Calculate the correlation coefficient between the measured data and the calibration data.

[0036] The calibration data includes and , For the Calibrated soil moisture distribution in soil layer The measuring electrodes are The calibrated impedance modulus obtained by the characteristic frequency; For the Calibrated soil moisture distribution in soil layer The measuring electrodes are The calibration phase obtained at the characteristic frequency; the correlation coefficient includes , and , For the The soil moisture content of the calibrated soil is distributed in the soil layer and Impedance modulus correlation coefficient between ; For the The soil moisture content of the calibrated soil is distributed in the soil layer and The phase correlation coefficient between For the The comprehensive correlation coefficient between the calibrated soil moisture distribution layer and the measured data is calculated by and Obtained by calculation.

[0037] S5. Get The maximum value in , will be The corresponding calibrated soil moisture distribution layer is used as the actual soil moisture distribution layer of the monitoring soil layer.

[0038] S6. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

[0039] As a further solution of this embodiment, it is possible to judge in sequence The impedance modulus difference and phase difference of the group are greater than the corresponding thresholds set for the soil moisture content distribution layer. If the impedance modulus difference and phase difference of the group of measuring electrodes are greater than the corresponding thresholds set, the monitoring soil layer is located Soil electrode No. 22 and There is an abnormality in the soil moisture content between soil electrodes 22. is greater than or equal to 1 and less than or equal to An integer; otherwise the monitored soil layer is normal.

[0040] This embodiment If any of the impedance modulus difference and phase difference of the group of measuring electrodes is greater than the corresponding threshold value set, it means that the soil moisture content in the monitored soil layer is abnormal, and there is a possibility of geological disasters. The inventors consider that, ideally, the simultaneous changes of impedance modulus and phase should be considered. If both show a clear deviation trend, it is more likely to indicate that the soil moisture content has indeed changed. However, in practical applications, sometimes only one parameter may show a significant change. For example, if a large amount of free water suddenly appears in the soil, the first thing to be affected may be the impedance modulus because it is more sensitive to changes in resistivity; while changes in phase will be delayed or become less obvious under certain conditions. Vice versa, for some specific types of soil or materials, the phase may respond more sensitively to changes in moisture content than the impedance modulus.

[0041] Specifically, refer to Figure 1 As the specific structure of the soil test column, each soil test column includes an outer shell 1, an electrode interlayer 2, a plurality of soil electrodes 22, a filling layer 30, a fixing plate 40 and a top cover 5.

[0042] Housing 1, reference Figure 2 . The outer shell 1 is a cylindrical structure with a hollow interior, and the bottom of the outer shell 1 is a conical structure. The outer shell 1 is made of a material with good stress resistance. The present embodiment adopts steel and is manufactured by a casting process. A plurality of circular measuring holes are provided on the outer wall of the cylindrical structure. The plurality of measuring holes on the outer shell 1 are evenly divided into multiple layers along the height direction, and the plurality of measuring holes on each layer are distributed in a circular shape. The measuring holes are evenly layered and distributed in a circular shape along the height direction, which ensures the consistency of the soil contact area of ​​each electrode, thereby improving the comparability between the measured values ​​of soil moisture content at different depths. Such a layout also facilitates the effective contact between the electrode and the soil, further improving the measurement accuracy.

[0043] As a further solution of this embodiment, refer to Figure 2 11-1a, 11-1b, 11-1c, 11-2a, 11-2b, 11-2c, 11-3a, 11-3b and 11-3c are all measuring holes. The multiple measuring holes are divided into three layers, with six holes in each layer, and the cores of the six measuring holes in the same layer are on a circle on a plane, which is perpendicular to the axis of the shell 1, and the angle between the cores of adjacent measuring holes in the shell 1 is 60°.

[0044] A plurality of fixing holes for the lock buckle to pass through are provided on the outer wall of the conical structure at the bottom of the housing. In this embodiment, three fixing holes are distributed in a ring shape. The plane formed by the three fixing holes is perpendicular to the axis of the housing 1, and the angle between adjacent measuring holes is 120°. Figure 2 12-1 and 12-2 are both fixing holes.

[0045] Electrode sandwich 2, reference Figure 4 The electrode sandwich 2 is a cylindrical structure, made of insulating material, and polytetrafluoroethylene is used in this embodiment; the outer diameter of the electrode sandwich 2 is smaller than the inner diameter of the upper half of the shell 1, so that the electrode sandwich 2 can be inserted into the shell 1 and fit closely to the shell 1. The height of the electrode sandwich 2 is slightly higher than the height of the uppermost measuring hole and the lowermost measuring hole. At the measuring hole position corresponding to the shell 1, an electrode mounting hole is opened. Reference Figure 4 21-1a, 21-1b, 21-1c, 21-2a, 21-2b, 21-2c, 21-3a, 21-3b and 21-3c are all electrode mounting holes.

[0046] The electrode mounting hole opening can be circular, and its radius is less than 0.8 times the radius of the measuring hole of the housing 1. Soil electrodes 22, One end of each soil electrode 22 passes through a plurality of measuring holes on the housing 1 to contact the soil. The other end of each soil electrode 22 is electrically connected to a measuring circuit 104 located on the filling layer 30 through an electrode connecting wire.

[0047] Soil electrode 22, ref. Figure 5 The soil electrode 22 is circular and smaller than the electrode mounting hole, and is glued to the electrode mounting hole by glue; one end of the soil electrode 22 is connected to the electrode connecting wire 23, which is a connecting wire with a conductor 24 in the middle and an insulating layer on the outside. The insulating layers are peeled off at both ends, one end is welded to the inside of the electrode, and the other end is fixed to the electrode connector 101 with a screw; the electrode connector 23 is led out from the top, passes through the connecting wire through hole 41 from the top, and is fixed to the electrode connector 101, and the electrode connector 101 is electrically connected to the multi-way switch 103 through the connecting cable 102.

[0048] Filling layer 30, reference Figure 7. The filling layer 30 is made of engineering plastic and has the same shape as the inner shape of the outer shell 1. It is installed in the outer shell 1 and is used to fix the electrode interlayer 2 in the outer shell 1. A plurality of guide holes are vertically arranged inside the filling layer. The bottoms of the plurality of guide holes are bent and respectively connected with the plurality of fixing holes. The tips of the plurality of lock buckles respectively enter the plurality of guide holes and drill out from the plurality of fixing holes into the soil. The lock buckle is a strip-shaped cylinder with one end being pointed. It is made of a material with good stress resistance and a certain deformation ability. The lock buckle is used to pass through the guide hole and embed into the soil. The design of the fixing holes on the outer wall of the conical structure and the internal guide holes and lock buckles enables the entire device to be firmly embedded in the soil and remain stable even under soft or slippery surface conditions. For long-term monitoring, the lock buckle can prevent data deviation caused by equipment displacement. Figure 7 31 - 1 , 31 - 2 and 31 - 3 are all guide holes.

[0049] In order to facilitate the filling layer 30 to be installed in the housing 1, refer to Figure 3 and Figure 6 In this embodiment, the inner wall of the housing 1 is provided with a plurality of guide grooves along the height direction, and the outer wall of the filling layer 30 is provided with flanges that slide with the plurality of guide grooves. Figure 3 13-1, 13-2, 13-3, and 13-4 are all guide grooves. Figure 6 32-1, 32-2, 32-3, and 32-4 are all flanges. The design of the guide groove and the flange allows the filling layer 30 to slide up and down in the housing 1 without rotating, ensuring the consistency of the position of the soil electrode 22, improving the measurement accuracy, helping to reduce the error caused by the movement of the device, and enhancing the reliability of the test results. In this embodiment, there are three guide holes, which are arranged in a circle at intervals of 120°.

[0050] Fixing plate 40, reference Figure 8 The fixing plate 40 is located at the top of the filling layer and is used to fix the fixing plate 40 of the measuring circuit 104 with bolts. A connection wire through hole 41 is provided in the middle of the fixing plate 40 for passing multiple electrode connection wires. The fixing plate 40 is a disc structure with an outer thread on the outside, which matches the inner thread on the top of the shell 1. The fixing plate 40 is fixed to the top of the shell 1 by the outer thread on the outside engaging with the inner thread on the top of the shell 1. The fixing plate 40 has four circuit board fixing holes, which are Figure 8 42 - 1 , 42 - 2 , 42 - 3 , and 42 - 4 are all used to mount the circuit board 6 of the measuring circuit 104 .

[0051] Top cover 5, reference Figure 1 The top cover 5 matches the external thread on the top of the housing 1 and is used to be installed on the top of the housing 1 so that the internal measuring circuit 104 is in a sealed state.

[0052] This embodiment provides a method for installing a soil test column, comprising the steps of: Step 1: Put the electrode sandwich 2 on the filling layer 30 and put it into the shell 1; when putting it in, the soil electrode 22 corresponds to the measuring hole of the shell 1 and is concentric with the soil electrode 22, and the soil electrode 22 does not contact the shell 1; Step 2: Use a hammer to knock the housing 1 into the monitored soil layer; Step 3: Place the pointed ends of the three lock buckles downward and use hammers to make them pass through the three guide holes and enter the soil layer through the fixing holes of the outer shell 1, so that the lock buckle parts are in the soil and lock the outer shell 1; the top of the lock buckle is knocked into the inner layer.

[0053] Step 4: After passing the connecting wire through the connecting wire hole, install it to the electrode connector; and install the fixing plate 40 on the housing 1.

[0054] Step 5: Connect the electrode connector 101 to the circuit board 6; Step 6: Install the circuit board 6 of the measuring circuit 104 onto the fixing plate 40; Step 7: Install the top cover 5 onto the housing 1; Complete the installation of the soil test column through the above 7 steps.

[0055] As a specific connection circuit of the measurement circuit 104 of this embodiment, refer to Fig. 9 and Fig.10 The measurement circuit 104 includes four measurement interfaces, which are a first measurement interface 116 - 1 , a second measurement interface 116 - 2 , a third measurement interface 116 - 3 , and a fourth measurement interface 116 - 4 electrically connected to the four multi-way switches 103 .

[0056] The first measurement interface 116-1 is electrically connected to the resistor 118, the sinusoidal signal generator 119 and the fourth measurement interface 116-4 in sequence. A resistor-voltage amplifier 120 electrically connected to a resistor-voltage analog-to-digital converter 122 is connected in parallel to the resistor 118. The resistor-voltage analog-to-digital converter 122 is electrically connected to the microprocessor 123; the sinusoidal signal generator 119 is electrically connected to the microprocessor 123.

[0057] The second measurement interface 116-2 and the third measurement interface 116-3 are both electrically connected to the soil voltage amplifier 117, and the soil voltage amplifier 117 is electrically connected to the microprocessor 123 through the soil voltage analog-to-digital converter 121; the microprocessor 123 is connected to the remote monitoring terminal signal through the data acquisition server 105, and the data acquisition server 105 of this embodiment includes a communication interface 124. The measurement circuit 104 can simultaneously obtain the resistance voltage and soil voltage information, providing a basis for calculating the impedance module. The use of the microprocessor 123 and the remote monitoring terminal realizes the automatic processing and real-time transmission of data, greatly improving the work efficiency.

[0058] In this embodiment, the multi-way switch 103 is a 64-to-one switch circuit. If there are less than 64 electrodes, only a part of the design can be used, or corresponding simplification can be made. Specifically, the 64-to-one switch circuit is referenced Fig.11 , composed of 9 chips MM74HC4051 from National Semiconductor, U1~U9. In the figure, the connection terminals N1~N64 are respectively connected to 64 BNC female connectors, and the BNC female connector electrode array cable detector connector is connected. The connection terminals A, B, C, E, D, and F are connected to the microprocessor 123. The sine signal generator 119 is a DDS integrated circuit, model AD9852, produced by Analog Devices, USA, reference Fig.12 The soil voltage amplifier 117 and the resistance voltage amplifier 120 use the same amplification circuit, refer to Fig.13 UA1 is the integrated circuit DAC1210 produced by National Semiconductor Corporation of the United States, and UA2 is the integrated circuit AD811 produced by ANALOG DEVICES of the United States. A_IN is the analog input terminal, and A_OUT is the amplified output terminal. A_D1-A_D10 are connected to the microprocessor 123 and are set to the gain size under the control of the microprocessor 123. The microprocessor 123 selects the integrated circuit TMS320F2812 produced by Texas Instruments of the United States, which integrates an analog-to-digital converter. Fig.14 , the microprocessor 123 is used to execute steps S2 to S4. Fig.14 ADC_IN1 is connected to the earth voltage amplifier 117, and ADC_IN2 is connected to the earth voltage amplifier 118. DDS_A0-DDS_A5, DDS_D0-DDS_D7 are control lines of the sine signal generator 119, connected to the sine signal generator 119. A_D1-A_D10 are connected to the program-controlled amplifier to control the gain of the program-controlled amplifier.

[0059] As a further solution of this embodiment, and The calculation method comprises the steps of: S3.1, set the frequency of the sine signal generator 119 to the first The sampling frequencies of the soil voltage analog-to-digital converter 121 and the resistance voltage analog-to-digital converter 122 are set to the first The characteristic frequency times; S3.2, respectively obtain The output data of the soil voltage analog-to-digital converter 121 and the resistance voltage analog-to-digital converter 122 are connected to the group of measuring electrodes. and , and calculate 100 and The absolute deviation value of and Deviation value of S3.3 Calculation and ;

[0060]

[0061] in, For 100 The sum of the absolute deviations of For 100 The sum of the absolute deviations of For 100 The sequence number of the negative zero crossing point in the deviation value; For 100 The sequence number of the negative zero crossing point in the deviation value. The sequence number of the negative zero crossing point is 100 in sequence. and The number of deviation values ​​that changes from positive to negative. For example: Assume that and )indivual The deviation values ​​are and , is a positive number, If is a negative number, the sequence number of the negative zero crossing point is , is a natural number.

[0062] The method for obtaining calibration data is the same as that for measuring data, except that the serial number of the calibration test soil layer is added.

[0063] In this embodiment, the characteristic frequency includes impedance mode characteristic frequencies and phase characteristic frequencies corresponding to a plurality of calibrated soil moisture distribution soil layers, and the method for obtaining the impedance mode characteristic frequency and phase characteristic frequency in each calibrated soil moisture distribution soil layer is: The soil test column is installed in the soil layer corresponding to the soil moisture distribution, and the impedance mode mean square error and phase mean square error of all combinations of measuring electrodes at different frequencies are obtained. The frequency corresponding to the maximum value of all impedance mode mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer, and the frequency corresponding to the maximum value of all phase mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer.

[0064] As a further solution of this embodiment, The calculation method is: = .

[0065] in:

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] in, and Respectively The impedance modulus average and phase average of all combined measuring electrodes in the soil layer of the calibrated soil moisture distribution; is the total number of characteristic frequencies; that is ; K is the number of combinations of all measuring electrodes , ; and They are and The average value of .

[0072] Example 2 This embodiment is further limited on the basis of Embodiment 1. The specific improvement lies in proposing a method for making a soil layer for calibrating soil moisture content distribution. For other parts not mentioned, refer to Embodiment 1 or the prior art.

[0073] This embodiment provides a method for calibrating soil moisture distribution soil layers, including the following steps: (1) Extract soil samples from the test points of the monitoring soil layer; (2) Dry the soil sample and grind it with a grinder; (3) Take dried soil and water and mix them with a mixer; (4) Place soil samples in multiple test chambers according to the uniform humidity and stratified humidity methods, and install humidity sensors. Use the humidity sensors to calibrate the soil moisture content distribution of two types of soil layers: uniform humidity and stratified humidity.

[0074] The length, width and height of the test chamber are all 1 meter. Uniform humidity means that all soil has the same humidity. Layered humidity means that the humidity increases in layers from bottom to top.

[0075] In this embodiment, ten kinds of calibrated soil moisture distribution soil layers with uniform humidity of 5%, 10%, 15%, ..., 50% were prepared respectively; there were seven kinds of calibrated soil moisture distribution soil layers with stratified humidity, all of which were set in 20 cm thick layers. The stratified humidity is shown in Table 1: Table 1 Layered humidity of soil layers for seven calibrated soil moisture content distributions

[0076] Therefore, this embodiment has a total of 17 calibrated soil moisture distribution soil layers, namely . Calibration data and The method of obtaining the data is the same as that of the measurement data, except that the serial number of the calibration experimental soil layer is added.

[0077] In summary, the beneficial effects of this solution are: The calibration experimental soil layer has stronger robustness. Even when environmental conditions change, the strategy can be quickly adjusted by comparing the calibration data, ensuring the continuity and stability of the monitoring work, making it easier for experts to assess accurate geological disaster warning levels.

[0078] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A single column soil moisture content testing method, characterized in that: Includes steps: S1. Install the soil test column in the monitoring soil layer; wherein the soil test column is provided with Each soil electrode is electrically connected to four measurement interfaces in the measurement circuit through four multi-way switches. is a natural number greater than or equal to 4; S2. Place the soil in the test column The soil electrodes are sorted and numbered respectively, and grouped into groups of 4 adjacent soil electrodes. Soil electrodes are divided into A set of measuring electrodes; S3. The measurement data of all the measurement electrodes in the monitored soil layer at different characteristic frequencies are obtained through the measurement circuit. The measurement data include and ;in, For the The measuring electrodes are The measured impedance modulus is obtained at the characteristic frequency , For the The measuring electrodes are The measured phase at the characteristic frequency ; S4, calculating the correlation coefficient between the measured data and the calibration data; The calibration data includes and , For the Calibrated soil moisture distribution in the soil layer The measuring electrodes are The calibrated impedance modulus obtained by the characteristic frequency; For the Calibrated soil moisture distribution in the soil layer The measuring electrodes are The calibration phase obtained at the characteristic frequency; the correlation coefficient includes , and , For the The soil moisture content of the calibrated soil is distributed in the soil layer and Impedance modulus correlation coefficient between ; For the The soil moisture content of the calibrated soil is distributed in the soil layer and The phase correlation coefficient between For the The comprehensive correlation coefficient between the calibrated soil moisture distribution layer and the measured data is calculated by and Calculate and obtain; S5. Get The maximum value in , will be The corresponding calibrated soil moisture distribution soil layer is used as the actual soil moisture distribution soil layer of the monitoring soil layer; S6. Based on the actual soil moisture content, soil layer distribution and geological structure of the monitored soil layer, the geological disaster warning level of the monitored soil layer is given by expert evaluation.

2. The single column soil moisture content testing method according to claim 1, characterized in that: The soil test column comprises a cylindrical shell, the bottom of the shell is a conical structure, a top cover is arranged on the top of the shell, a filling layer is arranged inside the shell, an electrode sandwich is arranged between the inner wall of the shell and the outer wall of the filling layer, and a Soil electrodes, One end of each soil electrode passes through multiple measuring holes on the shell to contact the soil. The other end of each soil electrode is electrically connected to a measuring circuit located on the filling layer through an electrode connecting wire.

3. The single column soil moisture content testing method according to claim 2, characterized in that: A plurality of guide grooves are provided on the inner wall of the shell along the height direction, and a flange which is slidably matched with the plurality of guide grooves is provided on the outer wall of the filling layer.

4. The single column soil moisture content testing method according to claim 2, characterized in that: A plurality of fixing holes for the lock buckles to pass through are provided on the outer wall of the conical structure at the bottom of the shell, a plurality of guide holes are vertically arranged inside the filling layer, the bottoms of the plurality of guide holes are bent and respectively connected with the plurality of fixing holes, and the tips of the plurality of lock buckles respectively enter the plurality of guide holes and drill out from the plurality of fixing holes into the soil.

5. The single column soil moisture content testing method according to claim 2, characterized in that: The multiple measuring holes on the shell are evenly divided into multiple layers along the height direction, and the multiple measuring holes on each layer are distributed in a circular shape.

6. The single column soil moisture content testing method according to claim 2, characterized in that: A fixing plate for fixing the measuring circuit with bolts is arranged on the top of the filling layer, and a connecting wire through-hole for passing a plurality of electrode connecting wires is opened in the middle of the fixing plate.

7. The single column soil moisture content testing method according to claim 1, characterized in that: The measurement circuit includes four measurement interfaces, which are respectively a first measurement interface, a second measurement interface, a third measurement interface, and a fourth measurement interface electrically connected to four multi-way switches; The first measurement interface is electrically connected to the resistor, the sinusoidal signal generator and the fourth measurement interface in sequence, a resistor voltage amplifier electrically connected to the resistor voltage analog-to-digital converter is connected in parallel to the resistor, the resistor voltage analog-to-digital converter is electrically connected to the microprocessor; the sinusoidal signal generator is electrically connected to the microprocessor; The second measurement interface and the third measurement interface are both electrically connected to the soil voltage amplifier, and the soil voltage amplifier is electrically connected to the microprocessor through a soil voltage analog-to-digital converter; the microprocessor is connected to the remote monitoring terminal signal through the communication interface.

8. The single column soil moisture content testing method according to claim 7, characterized in that: and The calculation method comprises the steps of: S3.1, set the frequency of the sine signal generator to the first The sampling frequencies of the soil voltage analog-to-digital converter and the resistance voltage analog-to-digital converter are set to The characteristic frequency times; S3.2, respectively obtain The output data of the soil voltage analog-to-digital converter and the resistance voltage analog-to-digital converter are connected to the 100-pole measuring electrode. and , and calculate 100 and The absolute deviation value of and Deviation value of S3.3 Calculation and ; in, For 100 The sum of the absolute deviations of For 100 The sum of the absolute deviations of For 100 The sequence number of the negative zero crossing point in the deviation value; For 100 The sequence number of the negative zero crossing point in the deviation value.

9. The single column soil moisture content testing method according to claim 8, characterized in that: The characteristic frequency includes impedance mode characteristic frequencies and phase characteristic frequencies corresponding to a plurality of calibrated soil moisture distribution soil layers. The method for obtaining the impedance mode characteristic frequency and phase characteristic frequency in each calibrated soil moisture distribution soil layer is as follows: The soil test column is installed in the soil layer corresponding to the soil moisture distribution, and the impedance mode mean square error and phase mean square error of all combinations of measuring electrodes at different frequencies are obtained. The frequency corresponding to the maximum value of all impedance mode mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer, and the frequency corresponding to the maximum value of all phase mean square errors is taken as the impedance mode characteristic frequency of the corresponding soil moisture distribution layer.

10. The single column soil moisture content testing method according to claim 9, characterized in that: The calculation method is: = in, and Respectively The impedance modulus average and phase average of all combined measuring electrodes in the soil layer of the calibrated soil moisture distribution; is the total number of characteristic frequencies; K is the number of combinations of all measuring electrodes ; and They are and The average value of .

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