Method and device for testing ice content of soil body based on electrochemical impedance modulus value

Abstract

The invention belongs to the technical field of soil research equipment, and aims to solve the problem of measurement errors when a time domain reflection device is used for measuring the ice content of soil. The invention provides a method and a device for testing the ice content of a soil body based on an electrochemical impedance modulus value. The method comprises the following steps: setting test parameters of the ice content of the soil body through an electronic computer; a temperature control device is used for adjusting and controlling test conditions of the soil body sample, and a control module drives the temperature control device to perform stepped cooling on the soil body sample; applying a disturbance signal to the soil body sample through the test module, and synchronously collecting a response signal sent by the soil body sample; calculating an experimental value of an electrochemical impedance module value by using electrochemical impedance data analysis software, fitting by combining with the temperature signal to obtain a fitting value of the electrochemical impedance module value, and substituting the value and the initial water content into a soil mass ice content calculation model to obtain the ice content of the soil mass sample. According to the invention, the ice content of the soil body can be rapidly and accurately calculated based on the chemical-electrochemical impedance modulus value.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil research equipment, and in particular relates to a method and device for testing the ice content of soil based on electrochemical impedance spectroscopy. Background Art

[0002] Frozen soil is a highly temperature-sensitive medium widely distributed in cold regions. Its engineering properties (such as strength and deformation characteristics) are crucial for infrastructure construction in cold regions, including roads, railways, and building foundations. The presence of unfrozen water in soil further complicates its properties. For example, during the construction of the Qinghai-Tibet Railway, frost heave and thaw settlement posed significant engineering challenges. Changes in soil ice content lead to changes in soil volume, thus impacting the stability of the railway subgrade.

[0003] With the continuous development of cold-region projects, such as the construction of polar research stations and infrastructure development in high-altitude mountainous areas, the need for precise soil ice content testing is becoming increasingly urgent. Accurate ice content testing provides fundamental data for studying the thermophysical properties of soil, helping engineers better predict the physical and mechanical properties of soil under temperature fluctuations, enabling them to implement effective engineering measures to ensure structural stability.

[0004] In early studies of frozen soil, a simple measuring instrument, consisting of an inner tube and an outer tube, was widely used. When soil freezes, the freezing depth of the water in the inner tube is determined by manually observing its presence. However, because the freezing temperature of soil differs from that of water, this method can only determine the freezing state of the soil to a certain extent and cannot accurately measure the soil ice content. Furthermore, with the development of soil dielectric theory, a time-domain reflectometry (TDR) instrument has been applied to measure soil ice content. However, this instrument only measures the amount of unfrozen water in the soil. Only by assuming that the total water content of the soil does not change during freezing can the ice content in the soil be calculated based on the difference between the water content during the unfrozen period and the water content during freezing. However, in reality, during the freezing process, changes in the external environment (such as snowfall) and changes in the soil's temperature can cause water migration within the soil. Therefore, this method can produce a certain degree of error in measuring soil ice content. Therefore, it is imperative to develop a new device and method for measuring soil ice content to address these issues. Summary of the Invention

[0005] In order to solve at least one of the above-mentioned technical problems existing in the prior art, the present invention provides a method and device for testing the ice content of soil based on electrochemical impedance spectroscopy.

[0006] According to a first aspect, a method for testing soil ice content based on electrochemical impedance spectroscopy is implemented through an integrated modular system control process, comprising the following steps: Step S1: setting soil ice content test parameters, wherein the test parameters include at least amplitude, frequency range, temperature gradient and scanning mode; Step S2: performing step-by-step cooling on the soil sample and collecting temperature signals in real time; Step S3: applying a preset disturbance signal to the soil sample, and synchronously collecting a response signal emitted by the soil sample by balancing the test loop impedance through a DC load; Step S4: obtaining electrochemical impedance modulus experimental values ​​at different frequencies based on the disturbance signal and the response signal, and fitting a curve of the electrochemical impedance modulus experimental value changing with the temperature signal according to a preset fitting function to obtain an electrochemical impedance modulus fitting value; Step S5: Obtain the initial water content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content into the soil ice content calculation model for calculation to obtain the ice content of the soil sample.

[0007] Preferably, the soil ice content calculation model in step S5 is: Where, is the ice content of the soil sample; is the experimental value of electrochemical impedance spectroscopy of the soil sample; is the electrochemical impedance spectroscopy fitting value of the soil sample; is the initial moisture content of the soil sample.

[0008] Preferably, the preset fitting function is: Where, Represents temperature signal, its unit is Kelvin, K; are the first parameter of the fitting curve and the second parameter of the fitting curve respectively.

[0009] Preferably, the soil sample is prepared as follows: Desalinated soil was selected and saline soil samples with different salt and water contents were prepared. The salt was dissolved and mixed with the soil, and then allowed to stand. The soil was compacted layer by layer and the dry density was controlled to 1.70g / cm³. Polished electrodes were placed on both sides of the samples and sealed.

[0010] Preferably, step S2 includes: The control module drives the temperature control device to control the temperature at 30°C until the temperature of the soil sample is stable, and then performs step-by-step cooling, with each level of temperature constant time being 12 hours. At the same time, the real-time temperature signal is fed back to the electronic computer.

[0011] According to a second aspect, a device for testing soil ice content based on electrochemical impedance spectroscopy (EIS) is provided, capable of executing the method for testing soil ice content based on EIS as described in the first aspect and any preferred embodiment, comprising an electronic computer, a control module, a temperature control device, a testing module, a data acquisition module, a data analysis module, and a data storage module. The electronic computer is connected to the control module, data acquisition module and data analysis module respectively, and is used to globally control the test process, receive collected data, trigger analysis instructions and store results; The control module is connected to the temperature control device and the test module and is used to adjust the test temperature, amplitude and frequency range; The temperature control device is connected to the test module and controls the temperature of the soil sample by step-by-step cooling. When the temperature drops to the negative temperature range, the temperature is adjusted at intervals of 3°C. The test module includes a DC load module, an AC source module and a sample placement device, which is used to apply a preset disturbance signal to the soil and collect a response signal; The data acquisition module is connected to the test module to collect disturbance signals, response signals and temperature data at different frequencies in real time; The data analysis module has built-in electrochemical impedance data analysis software and a soil ice content calculation model, which is used to calculate the electrochemical impedance modulus experimental value of the soil sample during the entire cooling process through the electrochemical impedance data analysis software, and fit the curve of the electrochemical impedance modulus experimental value in the unfrozen state with the temperature signal to obtain the electrochemical impedance modulus fitting value when the pore solution of the soil sample always remains in the unfrozen state under any temperature condition. The electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content of the soil sample are introduced into the soil ice content calculation model to obtain the ice content of the soil sample; The data storage module stores raw data, electrochemical impedance spectroscopy fitting values ​​and ice content calculation results in a classified manner.

[0012] Preferably, the test module includes: The DC load module is used to eliminate the electrode polarization effect and maintain the stability of the test loop impedance; The AC source module is used to generate disturbance signals of different frequencies and support automatic frequency sweeping from high frequency to low frequency; The sample placement device includes a gold electrode pair, a sealed cavity and a pressure sensor. The gold electrode pair is used to reduce contact impedance, the sealed cavity is used to reduce environmental interference, and the pressure sensor is used to monitor in real time the contact pressure with the gold electrode pair when compacting the soil sample.

[0013] Preferably, the control module and the test module communicate using optical fiber isolation.

[0014] Preferably, the gold electrode pair of the sample placement device is movably arranged, and the electrode spacing is adaptively adjusted according to the length of the soil sample after compaction.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention is realized through an integrated modular system control process. The control module controls the operation of the test module. By adjusting the test parameters of the test module, such as the test frequency and amplitude, the test device can better perform the test. The control module controls the operation of the temperature control device. By adjusting the test temperature of the soil, the test device can calculate the electrochemical impedance modulus experimental value and the ice content of the soil at a specified temperature, thereby solving the problem of being unable to control the temperature in the electrochemical impedance modulus test of the soil. The test module is simple and reasonable to set up. Through a simple design, the test can be completed more quickly, and the volume of the test device can also be compressed, making the test device easy to carry. The data acquisition module can automatically collect the data generated by the test module. Make the test smoother and faster; the data analysis module has more powerful analysis functions, which can not only test the electrochemical impedance modulus experimental value of the soil sample, but also directly output the ice content of the soil; the soil ice content calculation model, through a new soil ice content test method, can quickly and accurately calculate the ice content of the soil based on the electrochemical impedance modulus fitting value; the data storage module automatically stores the test data during the test, and can retain the test data completely, which is convenient for later data retrieval; the entire test system structure is complete and the setting is reasonable. A new device and method for testing soil ice content based on electrochemical impedance modulus fitting value is proposed, which can test soil ice content more conveniently, quickly and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a schematic diagram of a device for testing ice content in soil based on electrochemical impedance spectroscopy, provided in an embodiment of the present invention; Figure 2This is a flow chart of a method for testing ice content in soil based on electrochemical impedance spectroscopy provided by an embodiment of the present invention; Figure 3 Schematic diagram of the conductive path of saline soil provided by an embodiment of the present invention; Figure 4 1 is a schematic diagram of the electrochemical impedance spectroscopy experimental value and electrochemical impedance spectroscopy fitting value curve provided by the embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other implementations derived by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0019] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention. It should be noted that in this specification, relational terms such as first and second are only used to distinguish one entity from several other entities, and do not necessarily require or imply any actual relationship or order between these entities.

[0020] like Figure 1 As shown, an embodiment of the present invention provides a device for testing the ice content of soil based on electrochemical impedance spectroscopy, including an electronic computer, a control module, a temperature control device, a test module, a data acquisition module, a data analysis module, and a data storage module; The electronic computer is connected to the control module, data acquisition module and data analysis module respectively, and is used to globally control the test process, receive collected data, trigger analysis instructions and store results; The control module is connected to the temperature control device and the test module and is used to adjust the test temperature, amplitude and frequency range; The temperature control device is connected to the test module and controls the temperature of the soil sample by step-by-step cooling. When the temperature drops to the negative temperature range, the temperature is adjusted at intervals of 3°C. The test module includes a DC load module, an AC source module and a sample placement device, which is used to apply a preset disturbance signal to the soil and collect a response signal; The data acquisition module is connected to the test module and stores disturbance signals, response signals and temperature data at different frequencies in real time; The data analysis module has built-in electrochemical impedance data analysis software and a soil ice content calculation model, which is used to calculate the electrochemical impedance modulus experimental value of the soil sample during the entire cooling process through the electrochemical impedance data analysis software, and fit the curve of the electrochemical impedance modulus experimental value in the unfrozen state with the temperature signal to obtain the electrochemical impedance modulus fitting value when the pore solution of the soil sample always remains in the unfrozen state under any temperature condition. The electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content of the soil sample are introduced into the soil ice content calculation model to obtain the ice content of the soil sample; The data storage module stores raw data, electrochemical impedance spectroscopy fitting values ​​and ice content calculation results in a classified manner.

[0021] In this embodiment, the electronic computer is connected to the control module, and the electronic computer serves as the control center, which controls the operation of the temperature control device and the test module through the control module; the electronic computer is connected to the data acquisition module, which collects data generated by the test module and transmits it back to the electronic computer; the electronic computer is connected to the data analysis module, and the collected data is input into the data analysis module for analysis, and the input includes but is not limited to data such as the electrochemical impedance modulus experimental value of the soil; the electronic computer is connected to the data acquisition module, and the data generated during the test will be automatically stored in the data acquisition module; the control module is connected to the electronic computer and the test module, and controls various test conditions and parameters of the soil sample during the test; the temperature control device is connected to the control module, and the temperature control device adjusts the temperature parameters of the soil sample through the control of the control module; the temperature control device is connected to the test module, and the temperature parameters of the soil sample during the test are controlled by the test module; the test module is connected to the control module, and the test module directly adjusts the test conditions and parameters of the soil sample through the control of the control module; the test module and the data acquisition module are connected. The collection module is connected to input the data generated during the test into the data acquisition module; the test module includes a DC load, an AC source module and a sample placement device; the data acquisition module is connected to the test module to collect various data generated during the test; the data acquisition module is connected to an electronic computer to transmit the collected data to the electronic computer; the data analysis module is connected to the electronic computer to analyze the collected data and generate analysis results; the data analysis module includes electrochemical impedance data analysis software and a soil ice content calculation model; the electrochemical impedance data analysis software analyzes the disturbance signal and response signal collected by the data acquisition module and outputs the electrochemical impedance modulus experimental value of the soil sample during the entire cooling process, and fits the change curve of the electrochemical impedance modulus experimental value under unfrozen conditions and at different test frequencies with the temperature signal to obtain the electrochemical impedance modulus fitting value that changes with temperature; the soil ice content calculation model converts the electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value and the initial water content into the ice content of the soil sample through calculation and analysis.

[0022] In this embodiment, an electronic computer controls the entire testing process, outputs the ice content of the soil sample, and stores the test data. Specifically, a control module controls the testing module to achieve the frequency, ratio, and amplitude of the disturbance signal required for the test; controls the data acquisition module to collect test data; and controls the data analysis software to analyze the collected data. First, the electrochemical impedance modulus (EIM) experimental values ​​of the soil sample at different frequencies are obtained using EIM data analysis software. These EIM experimental values ​​are then fitted to obtain EIM fitting values. These EIM experimental values, EIM fitting values, and the initial water content of the soil sample are then incorporated into a soil ice content calculation model to calculate the ice content of the soil sample. Finally, a data storage module is controlled to store the data generated during the test.

[0023] In this embodiment, the electronic computer adopts a hierarchical storage architecture, including an original layer, an analysis layer, and an application layer. The original layer stores the original waveform of the disturbance / response signal according to the temperature range; the analysis layer binds the experimental value of the electrochemical impedance modulus, the fitting parameters, and the ice content results; the application layer generates the final test report (ice content-temperature change curve, error analysis table); and supports SQL query and data export, is compatible with third-party analysis software, and has universal applicability.

[0024] In this embodiment, the control module controls the operation of the temperature control device and the test module, adjusting the test module's test parameters, such as frequency and amplitude. It interprets control instructions from the computer and generates high-precision control signals: it outputs the temperature setpoint and constant temperature duration instructions to the temperature control device; and it outputs the amplitude, frequency range, and scanning mode to the test module.

[0025] In this embodiment, saline soil will not undergo phase change at positive temperature, so several representative temperatures are set to explore the effect of temperature on the electrochemical impedance spectrum of saline soil. At the same time, saline soil will undergo phase change at negative temperature, and saline soils with different salt contents have different freezing temperatures. Considering the significant changes in the phase change properties of saline soil in the negative temperature range, the temperature interval at negative temperature is set to 3°C, and the control module performs gradual temperature reduction control according to the preset temperature control time.

[0026] In this embodiment, the temperature control device, controlled by the control module, directly regulates the test soil temperature during the test. This device integrates a high- and low-temperature thermostat and a PID temperature controller, enabling a step-by-step cooling process. It monitors the resistance mutation points of the soil sample and automatically increases the number of temperature collection points (with cooling intervals as short as 1°C). Each temperature level is maintained constant for 12 hours or longer to ensure the freeze-thaw phase transition is fully complete. The temperature signal is fed back to the data acquisition module in real time to generate the corresponding impedance test data.

[0027] In this embodiment, the test module includes: the DC load module, which is used to eliminate the electrode polarization effect and maintain the stability of the test loop impedance; the AC source module, which is used to generate disturbance signals of different frequencies and support automatic frequency sweeping from high frequency to low frequency, continuously sending disturbance signals to the soil sample, and at the same time receiving the response signal fed back by the soil sample through the data acquisition module; the sample placement device, including a gold electrode pair, a sealed cavity and a pressure sensor, the gold electrode pair is used to reduce contact impedance, the sealed cavity is used to reduce environmental interference, and the pressure sensor is used to monitor the contact pressure with the gold electrode pair when compacting the soil sample in real time.

[0028] In this embodiment, the AC source module generates an amplitude accuracy The disturbance signal has a frequency resolution of , high frequency is , low frequency is ; Surface roughness of the gold electrode in the sample placement device The sealed cavity is composed of a plastic wrap anti-leakage layer and a plastic bag insulation layer.

[0029] In this embodiment, the gold electrode pair of the sample placement device is movable, and the electrode spacing is adjusted according to the length of the soil sample after compaction. The electrode spacing adjustment range is .

[0030] In this embodiment, the data acquisition module synchronously collects three signals, including a disturbance signal, a response signal, and a temperature signal. The disturbance signal includes voltage and frequency, and the response signal includes current and phase difference. An anti-aliasing filter and a 24-bit ADC converter are used to ensure the accuracy of response signal acquisition. The raw data is stored by temperature-timestamp classification to generate a structured database.

[0031] In this embodiment, the electrochemical impedance spectroscopy data analysis software converts the data collected by the data acquisition module into the complex form of Ohm's law. (in is the impedance, is the voltage, The electrochemical impedance modulus experimental values ​​of the soil sample at different frequencies are calculated. These electrochemical impedance modulus experimental values ​​and the corresponding frequencies are plotted on the complex plane to obtain the electrochemical impedance spectrum of the soil sample.

[0032] like Figure 2 As shown, an embodiment of the present invention provides a method for testing the ice content of soil based on electrochemical impedance spectroscopy, which is implemented through an integrated modular system control process and includes the following steps: Step S1: setting soil ice content test parameters, wherein the test parameters include at least amplitude, frequency range, temperature gradient and scanning mode; Step S2: performing step-by-step cooling on the soil sample and collecting temperature signals in real time; Step S3: applying a preset disturbance signal to the soil sample, and synchronously collecting a response signal emitted by the soil sample by balancing the test loop impedance through a DC load; Step S4: obtaining electrochemical impedance modulus experimental values ​​at different frequencies based on the disturbance signal and the response signal, and fitting a curve of the electrochemical impedance modulus experimental value changing with the temperature signal according to a preset fitting function to obtain an electrochemical impedance modulus fitting value; Step S5: Obtain the initial water content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content into the soil ice content calculation model for calculation to obtain the ice content of the soil sample.

[0033] In this embodiment, desalinated soil was selected for testing. The type of salt was selected and saline soil with different salt and water contents was prepared. When preparing the sample, the salt was first fully dissolved in water, and then the solution and soil were mixed and allowed to stand for a period of time to obtain saline soil with the required ice and salt content for the test. The prepared saline soil was loaded into the mold layer by layer and compacted layer by layer to form the soil sample required for the test. The dry density was controlled at After sample preparation is complete, the polished gold electrode pairs are placed on both sides of the soil sample. The soil sample is then wrapped in plastic wrap and then covered with a plastic bag. In actual engineering applications, non-saline soil can also be used for soil sample preparation. The preparation of non-saline soil samples is the same as that of saline soil samples, except for the addition of salt.

[0034] In this embodiment, the prepared soil sample is placed in a precise high and low temperature constant temperature bath and the temperature is controlled by an electronic computer-controlled temperature control device. The temperature of the soil sample is first kept constant at 30°C for a period of time. When the temperature of the soil sample is stable, the electrochemical impedance data analysis software built into the data analysis module is used to test the electrochemical impedance spectrum of the soil sample. The entire test process adopts a step-by-step cooling method, and each level of temperature is kept constant for 12 hours to ensure that the soil sample is stable at the corresponding temperature. Saline soil will not undergo phase change at positive temperature, and several representative temperatures are set to explore the effect of temperature on the electrochemical impedance spectrum of saline soil. The soil sample will undergo phase change at negative temperature, and saline soils with different salt contents have different freezing temperatures; considering the significant changes in the properties of the soil before and after the phase change, the temperature interval at negative temperature is set to 3°C. The electrochemical impedance spectrum is scanned in an impedance-frequency manner. The amplitude of the sine wave applied during the scan is 10mV, and the scan is performed from high frequency to low frequency. The frequency range is The scanning mode used a linear logarithmic sweep with a 10-point / 10-decade sweep, acquiring 70 EIS data points at each temperature. After the test, the EIS data analysis software was used to fit the experimental EIS modulus values ​​to obtain fitted EIS values, which were then transferred to the soil ice content calculation model.

[0035] In this embodiment, based on the electrochemical impedance modulus-temperature correlation surface, it can be concluded that there is a correlation between the experimental electrochemical impedance modulus values ​​at different temperatures at a specified test frequency and the ice content of the soil. For saline soils with different salt contents and initial water contents, the curves of the experimental electrochemical impedance modulus values ​​at different test frequencies under unfrozen conditions with temperature are fitted, and the fitting function is adopted. , where is the independent variable, is the dependent variable, 、 All of them are curve parameters. According to the fitting function, the electrochemical impedance modulus fitting value function that changes with the temperature signal is obtained. , where Kelvin, K, They are the first parameter of the fitting curve and the second parameter of the fitting curve, and the curve diagram of the experimental value of the electrochemical impedance modulus and the fitting value of the electrochemical impedance modulus is shown in Figure 4 As shown in Figure 2, the electrochemical impedance spectroscopy fitting value is the fitting value under any temperature condition assuming that the soil pore solution always remains unfrozen.

[0036] In this embodiment, Figure 3 As shown in FIG, there are three conductive paths in the saline soil system before freezing: conductive path 1 of continuous soil particle conduction, conductive path 2 of pore solution conduction, and conductive path 3 of soil particle-pore solution series conduction.

[0037] Given the insulating properties of soil particles, conductive path 1 can be equivalent to a capacitor. Due to the non-uniform size distribution of soil particles, this path exhibits non-ideal double-layer capacitance characteristics, so a constant phase angle element is used to characterize it. Conductive path 2, as the primary conductive channel, conducts electricity through ion migration in the pore solution, and its conductivity can be characterized by resistance. Conductive path 3 involves a series conduction mechanism between soil particles and the pore solution, and its equivalent model consists of a resistor connected in series with a constant phase angle element.

[0038] Under negative temperature conditions, ice / salt crystals form during the phase transition after freezing of the soil sample, creating two new conductive paths: conductive path 4 (continuous ice / salt crystal conduction) and conductive path 5 (discontinuous ice crystal-pore solution series conduction). Conductive path 4 is characterized by constant phase angle elements, while conductive path 5 is described by a combination of resistors and constant phase angle elements.

[0039] The significant increase in equivalent resistance during freezing is primarily due to the synergistic effects of two factors: first, the crystallization of ice crystals and hydrated salts reduces the liquid solution content, increasing resistance to ion migration; second, crystal growth leads to pore blockage, increasing the tortuosity of ion conduction paths. The variation in the equivalent resistance parameter effectively characterizes the dynamic evolution of ice content in the pore solution, providing an important quantitative basis for studying the electrical properties of frozen soils.

[0040] The soil ice content calculation model is used to convert the electrochemical impedance modulus fitting value of the soil sample into the soil ice content through calculation and analysis.

[0041] In this embodiment, the calculation model for the ice content of a soil sample at any temperature is: Where, is the ice content of the soil sample; is the experimental value of electrochemical impedance spectroscopy of the soil sample; is the electrochemical impedance spectroscopy fitting value of the soil sample; is the initial moisture content of the soil sample.

[0042] Embodiments of the present invention provide a method and apparatus for testing soil ice content based on electrochemical impedance spectroscopy (EIS) measurements. The test apparatus comprises a computer, a control module, a temperature control device, a test module, a data acquisition module, a data analysis module, and a data storage module. The test module includes a DC load, an AC source module, and a sample placement device. The data analysis module incorporates EIS data analysis software and a soil ice content calculation model. The entire test process is controlled by a computer, with automated data collection and storage. This provides a novel soil ice content testing method that can quickly and accurately calculate soil ice content based on the soil ice content calculation model.

[0043] The foregoing description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed herein should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for testing soil ice content based on electrochemical impedance spectroscopy, characterized in that: The steps include: Step S1: setting soil ice content test parameters, wherein the test parameters include at least amplitude, frequency range, temperature gradient and scanning mode; Step S2: performing step-by-step cooling on the soil sample and collecting temperature signals in real time; Step S3: applying a preset disturbance signal to the soil sample, and synchronously collecting a response signal emitted by the soil sample by balancing the test loop impedance through a DC load; Step S4: obtaining electrochemical impedance modulus experimental values ​​at different frequencies based on the disturbance signal and the response signal, and fitting a curve of the electrochemical impedance modulus experimental value changing with the temperature signal according to a preset fitting function to obtain an electrochemical impedance modulus fitting value; Step S5: Obtain the initial water content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content into the soil ice content calculation model for calculation to obtain the ice content of the soil sample.

2. The method for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that: The soil ice content calculation model in step S5 is expressed as follows: Where, is the ice content of the soil sample; is the experimental value of electrochemical impedance spectroscopy of the soil sample; is the electrochemical impedance spectroscopy fitting value of the soil sample; is the initial moisture content of the soil sample.

3. The method for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that: The preset fitting function is: Where, Represents temperature signal, its unit is Kelvin, K; are the first parameter of the fitting curve and the second parameter of the fitting curve respectively.

4. The method for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that: The preparation process of the soil sample is as follows: Desalinated soil was selected and saline soil samples with different salt and water contents were prepared. The salt was dissolved and mixed with the soil, and then allowed to stand. The soil was compacted layer by layer and the dry density was controlled to 1.70g / cm³. Polished electrodes were placed on both sides of the samples and sealed.

5. The method for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that: Step S2 includes: The control module drives the temperature control device to control the temperature at 30°C until the temperature of the soil sample is stable, and then performs step-by-step cooling, with each level of temperature constant time being 12 hours. At the same time, the real-time temperature signal is fed back to the electronic computer.

6. A device for testing soil ice content based on electrochemical impedance spectroscopy, capable of executing the method for testing soil ice content based on electrochemical impedance spectroscopy as claimed in any one of claims 1 to 5, characterized in that: It includes an electronic computer, a control module, a temperature control device, a test module, a data acquisition module, a data analysis module and a data storage module; The electronic computer is connected to the control module, data acquisition module and data analysis module respectively, and is used to globally control the test process, receive collected data, trigger analysis instructions and store results; The control module is connected to the temperature control device and the test module and is used to adjust the test temperature, amplitude and frequency range; The temperature control device is connected to the test module and controls the temperature of the soil sample by step-by-step cooling. When the temperature drops to the negative temperature range, the temperature is adjusted at intervals of 3°C. The test module includes a DC load module, an AC source module and a sample placement device, which is used to apply a preset disturbance signal to the soil and collect a response signal; The data acquisition module is connected to the test module to collect disturbance signals, response signals and temperature data at different frequencies in real time; The data analysis module has built-in electrochemical impedance data analysis software and a soil ice content calculation model, which is used to calculate the electrochemical impedance modulus experimental value of the soil sample during the entire cooling process through the electrochemical impedance data analysis software, and fit the curve of the electrochemical impedance modulus experimental value in the unfrozen state with the temperature signal to obtain the electrochemical impedance modulus fitting value when the pore solution of the soil sample always remains in the unfrozen state under any temperature condition. The electrochemical impedance modulus experimental value, the electrochemical impedance modulus fitting value, and the initial water content of the soil sample are introduced into the soil ice content calculation model to obtain the ice content of the soil sample; The data storage module stores raw data, electrochemical impedance spectroscopy fitting values ​​and ice content calculation results in a classified manner.

7. The device for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 6, characterized in that: The test module includes: The DC load module is used to eliminate the electrode polarization effect and maintain the stability of the test loop impedance; The AC source module is used to generate disturbance signals of different frequencies and support automatic frequency sweeping from high frequency to low frequency; The sample placement device includes a gold electrode pair, a sealed cavity and a pressure sensor. The gold electrode pair is used to reduce contact impedance, the sealed cavity is used to reduce environmental interference, and the pressure sensor is used to monitor in real time the contact pressure with the gold electrode pair when compacting the soil sample.

8. The device for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 6, characterized in that: The control module and the test module communicate with each other using optical fiber isolation.

9. The device for testing ice content in soil based on electrochemical impedance spectroscopy according to claim 6, characterized in that: The gold electrode pair of the sample placement device is movably arranged, and the distance between the electrodes is adaptively adjusted according to the length of the soil sample after compaction.

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