A method and apparatus for testing the ice content of soil based on electrochemical impedance spectroscopy.

Abstract

This invention belongs to the technical field of soil research equipment, and aims to solve the problem of measurement error when using time-domain reflectometry (TDAR) to measure soil ice content. It provides a method and apparatus for testing soil ice content based on electrochemical impedance spectroscopy (EIS), comprising: setting soil ice content testing parameters via a computer; adjusting and controlling the soil sample testing conditions using a temperature control device, with a control module driving the temperature control device to perform stepwise cooling of the soil sample; applying a disturbance signal to the soil sample via a testing module and simultaneously acquiring the response signal emitted by the soil sample; calculating the experimental value of the electrochemical impedance spectroscopy modulus using electrochemical impedance data analysis software, and fitting the measured value with the temperature signal to obtain a fitted value of the electrochemical impedance spectroscopy modulus; and inputting the above value and the initial moisture content into the soil ice content calculation model to obtain the ice content of the soil sample. This invention can quickly and accurately calculate the ice content of soil based on electrochemical impedance spectroscopy.

Description

Technical Field

[0001] This invention belongs to the technical field of soil research equipment, specifically relating to a method and apparatus for testing the ice content of soil based on electrochemical impedance modulus. Background Technology

[0002] Frozen soil is a highly temperature-sensitive medium widely distributed in cold regions. Its engineering properties (such as strength and deformation characteristics) have a crucial impact on infrastructure construction in cold regions (such as highways, railways, and building foundations). Because it contains unfrozen water, the properties of frozen soil are even more complex. For example, during the construction of the Qinghai-Tibet Railway, the problems of frost heave and thaw settlement of the soil posed a significant challenge to the project. Changes in the ice content of the soil lead to changes in soil volume, thus affecting the stability of the railway subgrade.

[0003] With the continuous development of cold-region engineering projects, such as the construction of polar research stations and infrastructure construction in high-altitude mountainous areas, the demand for accurate testing of soil ice content is becoming increasingly urgent. Accurate ice content testing can provide basic data for the study of soil thermophysical properties, helping engineers to better predict the physical and mechanical properties of soil under temperature changes, thereby enabling them to take effective engineering measures to ensure the stability of structures.

[0004] In early permafrost research, permafrost apparatus was widely used as a simple measuring tool. Its structure consists of an inner and outer tube. When the soil freezes, the freezing depth is determined by manually observing the freezing of water in the inner tube. However, since the freezing temperature of soil and water are different, this method can only determine the freezing condition to a certain extent and cannot accurately measure the ice content of the soil. Furthermore, with the development of soil dielectric theory, a time-domain reflectometry (TDR) device has been applied to measure the ice content of soil. However, this device can only measure the water content of unfrozen water in the soil. Only under the assumption that the total water content remains unchanged during the freezing process 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 the freezing process. However, in reality, during the freezing process, changes in the external environment (such as snowfall) and changes in the soil's own temperature will cause water migration within the soil area. Therefore, this method has a certain degree of error in measuring the ice content of soil. Therefore, it is essential to develop a new device and method for testing the ice content of soil to address the above problems. Summary of the Invention

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

[0006] According to the first aspect, a method for testing the ice content of soil based on electrochemical impedance spectroscopy is implemented through an integrated modular system control process, including the following steps:

[0007] Step S1: Set the soil ice content test parameters, which include at least amplitude, frequency range, temperature gradient and scanning mode;

[0008] Step S2: Perform a stepped cooling on the soil sample and collect temperature signals in real time;

[0009] Step S3: Apply a preset disturbance signal to the soil sample and simultaneously acquire the response signal emitted by the soil sample through the DC load balancing test circuit impedance.

[0010] Step S4: Based on the disturbance signal and response signal, obtain the experimental values ​​of electrochemical impedance modulus at different frequencies, and fit the curve of the experimental values ​​of electrochemical impedance modulus changing with the temperature signal according to the preset fitting function to obtain the fitted value of electrochemical impedance modulus.

[0011] Step S5: Obtain the initial moisture content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the experimental value of the electrochemical impedance spectroscopy, the fitted value of the electrochemical impedance spectroscopy, and the initial moisture content into the soil ice content calculation model to calculate the ice content of the soil sample.

[0012] Preferably, the soil ice content calculation model in step S5 is as follows:

[0013]

[0014] In the formula, This represents the ice content of the soil sample. The experimental value of the electrochemical impedance modulus of the soil sample; The fitted value of the electrochemical impedance modulus of the soil sample; This represents the initial moisture content of the soil sample.

[0015] Preferably, the preset fitting function is:

[0016]

[0017] In the formula, This represents a temperature signal, and its unit is Kelvin, K; These are the first parameter and the second parameter of the fitted curve, respectively.

[0018] Preferably, the soil sample preparation process is as follows:

[0019] Select desalinated soil and prepare saline soil samples with different salt and water contents; dissolve the salt and mix it with the soil, let it stand, compact it in layers and control the dry density to 1.70 g / cm³; place polishing electrodes on both sides of the sample and seal it.

[0020] Preferably, step S2 includes:

[0021] The control module drives the temperature control device to maintain the temperature at 30℃ until the soil sample temperature stabilizes. Then, a step-by-step cooling process is performed, with each temperature level held constant for 12 hours. Simultaneously, the real-time temperature signal is fed back to the computer.

[0022] According to the second aspect, an apparatus for testing the ice content of soil based on electrochemical impedance modulus is capable of performing a method for testing the ice content of soil based on electrochemical impedance modulus 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.

[0023] The electronic computer is connected to the control module, the data acquisition module, and the data analysis module respectively, and is used to globally control the test process, receive acquired data, trigger analysis commands, and store results.

[0024] 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.

[0025] The temperature control device is connected to the testing module and controls the temperature of the soil sample through stepped cooling. When the temperature drops to the negative temperature range, the cooling is adjusted at 3°C ​​intervals.

[0026] The test module includes a DC load module, an AC source module, and a sample placement device, which are used to apply a preset disturbance signal to the soil and collect the response signal.

[0027] The data acquisition module is connected to the test module and collects disturbance signals, response signals and temperature data at different frequencies in real time.

[0028] The data analysis module has built-in electrochemical impedance data analysis software and a soil ice content calculation model. It is used to calculate the experimental value of the electrochemical impedance modulus of the soil sample throughout the cooling process using the electrochemical impedance data analysis software, and to fit the curve of the experimental value of the electrochemical impedance modulus in the unfrozen state with the temperature signal to obtain the fitted value of the electrochemical impedance modulus of the soil sample in the unfrozen state under any temperature conditions. The experimental value of the electrochemical impedance modulus, the fitted value of the electrochemical impedance modulus, and the initial water content of the soil sample are then input into the soil ice content calculation model to obtain the ice content of the soil sample.

[0029] The data storage module categorizes and stores raw data, fitted values ​​of electrochemical impedance modulus, and calculation results of ice content.

[0030] Preferably, the test module includes:

[0031] The DC load module is used to eliminate electrode polarization effect and maintain the stability of the test circuit impedance.

[0032] The AC source module is used to generate disturbance signals of different frequencies and supports automatic frequency sweeping from high frequency to low frequency.

[0033] 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 resistance, the sealed cavity is used to reduce environmental interference, and the pressure sensor is used to monitor the contact pressure between the compacted soil sample and the gold electrode pair in real time.

[0034] Preferably, the control module and the test module communicate with each other using fiber optic isolation.

[0035] Preferably, the gold electrode pairs of the sample placement device are movable, and the electrode spacing is adjusted according to the length of the compacted soil sample.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] This invention achieves its goals through an integrated modular system control process. The control module manages the operation of the testing module, adjusting parameters such as testing frequency and amplitude to improve test performance. The control module also manages the temperature control device, adjusting the soil's test temperature to calculate the experimental value of the soil's electrochemical impedance modulus and ice content at a specified temperature, thus solving the problem of uncontrollable temperature in soil electrochemical impedance modulus tests. The testing module is simple and rationally designed, allowing for faster testing and a smaller, more portable device. The data acquisition module automatically collects data generated by the testing module. This system makes testing smoother and faster; the data analysis module has more powerful analytical functions, capable of both testing the experimental value of the electrochemical impedance modulus of soil samples and directly outputting the ice content of the soil; the soil ice content calculation model, through a new method for testing soil ice content, can quickly and accurately calculate the ice content of soil based on the fitted value of the electrochemical impedance modulus; the data storage module automatically stores the test data during the testing process, ensuring complete retention of the test data for easy retrieval later; the entire testing system has a complete structure and reasonable settings, proposing a new device and method for testing soil ice content based on the fitted value of the electrochemical impedance modulus, enabling more convenient, faster, and more accurate testing of soil ice content. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a device for testing the ice content of soil based on electrochemical impedance modulus, provided in an embodiment of the present invention.

[0040] Figure 2 This is a schematic flowchart of a method for testing the ice content of soil based on electrochemical impedance modulus provided in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the conductive path of saline soil provided in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the experimental value and the fitted value curve of the electrochemical impedance modulus provided in the embodiments of the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationships, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should fall within the scope of the technical content disclosed in 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.

[0045] like Figure 1 As shown, this embodiment of the invention provides a device for testing the ice content of soil based on electrochemical impedance modulus, including 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;

[0046] The electronic computer is connected to the control module, the data acquisition module, and the data analysis module respectively, and is used to globally control the test process, receive acquired data, trigger analysis commands, and store results.

[0047] 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.

[0048] The temperature control device is connected to the testing module and controls the temperature of the soil sample through stepped cooling. When the temperature drops to the negative temperature range, the cooling is adjusted at 3°C ​​intervals.

[0049] The test module includes a DC load module, an AC source module, and a sample placement device, which are used to apply a preset disturbance signal to the soil and collect the response signal.

[0050] The data acquisition module is connected to the testing module and stores disturbance signals, response signals and temperature data at different frequencies in real time.

[0051] The data analysis module has built-in electrochemical impedance data analysis software and a soil ice content calculation model. It is used to calculate the experimental value of the electrochemical impedance modulus of the soil sample throughout the cooling process using the electrochemical impedance data analysis software, and to fit the curve of the experimental value of the electrochemical impedance modulus in the unfrozen state with the temperature signal to obtain the fitted value of the electrochemical impedance modulus of the soil sample in the unfrozen state under any temperature conditions. The experimental value of the electrochemical impedance modulus, the fitted value of the electrochemical impedance modulus, and the initial water content of the soil sample are then input into the soil ice content calculation model to obtain the ice content of the soil sample.

[0052] The data storage module categorizes and stores raw data, fitted values ​​of electrochemical impedance modulus, and calculation results of ice content.

[0053] In this embodiment, the electronic computer is connected to the control module, which acts as the control center, controlling the operation of the temperature control device and the testing module. The electronic computer is also connected to the data acquisition module, collecting data generated by the testing module and transmitting it back to the electronic computer. Furthermore, the electronic computer is connected to the data analysis module, inputting the collected data for analysis, including but not limited to experimental values ​​of the soil's electrochemical impedance modulus. Data generated during the testing process is automatically stored in the data acquisition module. The control module is connected to both the electronic computer and the testing module, controlling various testing conditions and parameters of the soil sample during the testing process. The temperature control device is connected to the control module, adjusting the temperature parameters of the soil sample under the control of the control module. The temperature control device is also connected to the testing module, controlling the temperature parameters of the soil sample during the testing process. The testing module is connected to the control module, directly adjusting the testing conditions and parameters of the soil sample under the control of the control module. Finally, the testing module is connected to the data acquisition module. The system integrates multiple modules, including a DC load, an AC power source module, and a sample placement device. The data acquisition module connects to the testing module to collect various data generated during the testing process. It also connects to a computer to transmit the collected data. A data analysis module connects to the computer to analyze the collected data and generate analysis results. The data analysis module includes electrochemical impedance spectroscopy (EIS) analysis software and a soil ice content calculation model. The EIS analysis software analyzes the disturbance and response signals collected by the data acquisition module and outputs the experimental EIS modulus values ​​of the soil sample throughout the cooling process. It also fits the curves of the experimental EIS modulus values ​​under different testing frequencies and without freezing to obtain the fitted EIS modulus values ​​as a function of temperature. The soil ice content calculation model calculates and analyzes the experimental EIS modulus values, the fitted EIS modulus values, and the initial moisture content to convert them into the ice content of the soil sample.

[0054] In this embodiment, a computer controls the entire testing process, outputs the ice content of the soil sample, and stores the test data. Specifically, the control module controls the testing module to meet the frequency, proportion, amplitude, etc., of the disturbance signal required for the test; the control data acquisition module collects test data; the control data analysis software analyzes the collected data. First, the electrochemical impedance spectroscopy (EIS) data analysis software obtains the experimental values ​​of the electrochemical impedance spectroscopy modulus of the soil sample at different frequencies. Then, the experimental values ​​of the electrochemical impedance spectroscopy modulus of the soil sample are fitted to obtain the fitted electrochemical impedance spectroscopy modulus value. The experimental values ​​of the electrochemical impedance spectroscopy modulus, the fitted electrochemical impedance spectroscopy modulus value, and the initial water content of the soil sample are input into the soil ice content calculation model to calculate the ice content of the soil sample. The control data storage module stores the data generated during the test.

[0055] In this embodiment, the electronic computer adopts a hierarchical storage architecture, including a raw layer, a resolution layer, and an application layer. The raw layer stores the original waveforms of the disturbance / response signals according to temperature ranges; the resolution layer binds the experimental values ​​of the electrochemical impedance modulus, fitting parameters, and ice content results; the application layer generates the final test report (ice content-temperature change curve, error analysis table); and supports SQL queries and data export, is compatible with third-party analysis software, and has universality.

[0056] In this embodiment, the control module controls the operation of the temperature control device and the testing module, and adjusts the testing parameters such as the testing frequency and amplitude of the testing module. It parses the control commands issued by the computer and generates high-precision control signals: outputting temperature setpoints and constant temperature duration commands to the temperature control device; and outputting amplitude, frequency range, and scanning mode to the testing module.

[0057] In this embodiment, no phase transition occurs in saline soil at positive temperatures. Therefore, several representative temperatures are set to investigate the effect of temperature on the electrochemical impedance spectroscopy of saline soil. At the same time, a phase transition occurs in saline soil at negative temperatures, and the freezing temperature of saline soil with different salt contents is different. Considering the significant change in the phase transition properties of saline soil in the negative temperature range, the temperature interval at negative temperatures is set to 3°C. The control module performs gradual cooling control according to the preset temperature control time.

[0058] In this embodiment, the temperature control device, controlled by the control module, directly adjusts the temperature of the test soil during the test. This device integrates a high-low temperature constant temperature bath and a PID temperature controller, enabling it to execute a stepped cooling process; monitor the resistance abrupt change points of the soil sample, automatically increasing the density of temperature acquisition points (cooling intervals can be reduced to 1℃); maintain a constant temperature for ≥12 hours per stage to ensure the freeze-thaw phase transition is fully completed; and provide real-time temperature feedback to the data acquisition module to generate corresponding impedance test data.

[0059] In this embodiment, the testing module includes: a DC load module for eliminating electrode polarization effects and maintaining stable test circuit impedance; an AC source module for generating disturbance signals of different frequencies and supporting automatic frequency sweeping from high to low frequencies, continuously sending disturbance signals to the soil sample, and simultaneously receiving response signals from the soil sample via a data acquisition module; and a 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 between the compacted soil sample and the gold electrode pair in real time.

[0060] In this embodiment, the AC source module generates amplitude accuracy. The disturbance signal has a frequency resolution of up to High frequency is Low frequency is The gold electrode in the sample placement device affects the surface roughness. The sealed cavity consists of a plastic wrap to prevent leakage and a plastic bag insulation layer.

[0061] 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 compacted soil sample. The adjustment range of the electrode spacing is as follows: .

[0062] In this embodiment, the data acquisition module simultaneously acquires three signals, including disturbance signal, response signal and 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 according to temperature-timestamp classification to generate a structured database.

[0063] In this embodiment, the electrochemical impedance data analysis software processes the data acquired by the data acquisition module according to the complex form of Ohm's law. (in For impedance, For voltage, (where is the current), the experimental values ​​of the electrochemical impedance modulus of the soil sample at different frequencies are calculated, and these experimental values ​​of the electrochemical impedance modulus and the corresponding frequencies are plotted on the complex plane to obtain the electrochemical impedance spectrum of the soil sample.

[0064] like Figure 2 As shown, this embodiment of the 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:

[0065] Step S1: Set the soil ice content test parameters, which include at least amplitude, frequency range, temperature gradient and scanning mode;

[0066] Step S2: Perform a stepped cooling on the soil sample and collect temperature signals in real time;

[0067] Step S3: Apply a preset disturbance signal to the soil sample and simultaneously acquire the response signal emitted by the soil sample through the DC load balancing test circuit impedance.

[0068] Step S4: Based on the disturbance signal and response signal, obtain the experimental values ​​of electrochemical impedance modulus at different frequencies, and fit the curve of the experimental values ​​of electrochemical impedance modulus changing with the temperature signal according to the preset fitting function to obtain the fitted value of electrochemical impedance modulus.

[0069] Step S5: Obtain the initial moisture content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the experimental value of the electrochemical impedance spectroscopy, the fitted value of the electrochemical impedance spectroscopy, and the initial moisture content into the soil ice content calculation model to calculate the ice content of the soil sample.

[0070] In this embodiment, desalinated soil was selected for the test. Different types of salt were chosen, and saline soils with varying salt and moisture contents were prepared. When preparing the samples, the salt was first fully dissolved in water. Then, the solution was mixed with the soil and allowed to stand for a period of time to obtain the required salt and moisture content for the test. The prepared saline soil was then layered into a mold and compacted layer by layer to form the soil samples required for the test. The dry density was controlled at [specific value missing]. After sample preparation, polished gold electrodes are placed on both sides of the soil sample, then the soil sample is wrapped with plastic wrap and the outer layer is wrapped with a plastic bag. In practical engineering applications, non-saline soil can also be selected for soil sample preparation. Except for the salting part, the preparation of non-saline soil samples is the same as that of saline soil samples.

[0071] In this embodiment, the prepared soil sample was placed in a precision high-low temperature constant temperature bath, and the temperature was controlled by a computer-controlled temperature control device. The temperature of the soil sample was first kept constant at 30°C for a period of time until the temperature of the soil sample stabilized. Then, the electrochemical impedance spectroscopy of the soil sample was tested using the electrochemical impedance data analysis software built into the data analysis module. The entire experimental process adopted a stepped cooling method, with each temperature constant time being 12 hours to ensure the stability of the soil sample at the corresponding temperature. Saline soil does not undergo a phase transition at positive temperatures, so several representative temperatures were set to explore the effect of temperature on the electrochemical impedance spectroscopy of saline soil. The soil sample undergoes a phase transition at negative temperatures, and the freezing temperature of saline soil with different salt contents is different; considering the significant changes in the properties of the soil before and after the phase transition, the temperature interval at negative temperatures was set to 3°C. The electrochemical impedance spectroscopy was scanned using an impedance-frequency method, with the amplitude of the applied sine wave being 10mV, and the scan was performed from high frequency to low frequency, with a frequency range of [missing information]. The scanning mode adopted a linear logarithmic scanning method with a frequency overlay of 10 points / 10 overlays, obtaining 70 electrochemical impedance spectroscopy data points under each temperature condition. After the test, the experimental values ​​of electrochemical impedance modulus were fitted using electrochemical impedance data analysis software to obtain fitted values ​​of electrochemical impedance modulus, which were then transferred to the soil ice content calculation model.

[0072] In this embodiment, based on the electrochemical impedance modulus-temperature correlation surface, a correlation can be established between the experimental electrochemical impedance modulus values ​​at different temperatures under 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 ​​versus temperature at different test frequencies under unfrozen conditions are fitted, and the fitting function is adopted. In the formula, As the independent variable, As the dependent variable, , These are all curve parameters. Based on this fitting function, the fitting value function of the electrochemical impedance modulus as a function of temperature signal is obtained. In the formula, Kelvin, K The diagrams showing the first and second parameters of the fitted curve, the experimental values ​​of the electrochemical impedance spectroscopy modulus, and the fitted values ​​of the electrochemical impedance spectroscopy modulus are shown below. Figure 4 As shown, the fitted value of the electrochemical impedance modulus is the fitted value under any temperature condition assuming that the soil pore solution is always kept unfrozen.

[0073] In this embodiment, as Figure 3 As shown, there are three conductive pathways in the pre-freezing saline soil system: conductive pathway 1, conductive pathway 2, conductive pathway 3, and conductive pathway 3, which involves the continuous conduction of soil particles and pore solution.

[0074] Given the insulating properties of soil particles, conductive path 1 can be equivalent to a capacitor. Due to the non-uniformity of soil particle size distribution, this path actually exhibits non-ideal double-layer capacitance characteristics; therefore, a constant phase angle element is used for characterization. Conductive path 2, as the main conductive channel, achieves conductivity 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; its equivalent model consists of a resistor connected in series with a constant phase angle element.

[0075] Under negative temperature conditions, the soil sample freezes and undergoes a phase transition process to form ice / salt crystals, resulting in 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 using a constant phase angle element, while conductive path 5 is described by a combination of resistance and a constant phase angle element.

[0076] The significant increase in equivalent resistance caused by the freezing process stems primarily from two synergistic effects: firstly, the crystallization of ice crystals and hydrated salts reduces the liquid solution content, exacerbating ion migration resistance; secondly, crystal growth leads to pore blockage, increasing the tortuosity of ion conduction paths. The variation law of the equivalent resistance parameter can effectively characterize the dynamic evolution of ice content in the pore solution, providing important quantitative evidence for the study of the electrical properties of permafrost.

[0077] The soil ice content calculation model is used to convert the fitted value of the electrochemical impedance modulus of the soil sample into the ice content of the soil through calculation and analysis.

[0078] In this embodiment, the calculation model for the ice content of soil samples at any temperature is as follows:

[0079]

[0080] In the formula, This refers to the ice content of the soil sample. The experimental value of the electrochemical impedance modulus of the soil sample; The fitted value of the electrochemical impedance modulus of the soil sample; This represents the initial moisture content of the soil sample.

[0081] This invention provides a method and apparatus for testing the ice content of soil based on electrochemical impedance spectroscopy. The experimental apparatus includes: a 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 testing module includes a DC load, an AC power source module, and a sample placement device. The data analysis module incorporates electrochemical impedance spectroscopy data analysis software and a soil ice content calculation model. The entire testing process is controlled by a computer, automatically performing test data and storage operations. This provides a novel method for testing the ice content of soil, enabling rapid and accurate calculation of the ice content based on the soil ice content calculation model.

[0082] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for testing the ice content of soil based on electrochemical impedance spectroscopy, characterized in that, Includes the following steps: Step S1: Set the soil ice content test parameters, which include at least amplitude, frequency range, temperature gradient and scanning mode; Step S2: Perform a stepped cooling on the soil sample and collect temperature signals in real time; Step S3: Apply a preset disturbance signal to the soil sample and simultaneously acquire the response signal emitted by the soil sample through the DC load balancing test circuit impedance. Step S4: Based on the disturbance signal and response signal, obtain the experimental values ​​of electrochemical impedance modulus of soil samples at different frequencies throughout the cooling process, and fit the curve of the experimental values ​​of electrochemical impedance modulus in the unfrozen state with the temperature signal according to the preset fitting function to obtain the fitted value of electrochemical impedance modulus of pore solution of soil sample in unfrozen state under any temperature condition. Step S5: Obtain the initial moisture content of the soil sample, and simultaneously construct a soil ice content calculation model. Input the experimental value of the electrochemical impedance modulus, the fitted value of the electrochemical impedance modulus, and the initial moisture content into the soil ice content calculation model to calculate the ice content of the soil sample. The expression for the soil ice content calculation model in step S5 is: In the formula, This refers to the ice content of the soil sample. The experimental value of the electrochemical impedance modulus of the soil sample; The fitted value of the electrochemical impedance modulus of the soil sample; This represents the initial moisture content of the soil sample.

2. The method for testing the ice content of soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that, The preset fitting function is: In the formula, This represents a temperature signal, and its unit is Kelvin, K; These are the first parameter and the second parameter of the fitted curve, respectively.

3. The method for testing the ice content of soil based on electrochemical impedance spectroscopy according to claim 1, characterized in that, The preparation process of the soil sample is as follows: Select desalinated soil and prepare saline soil samples with different salt and water contents; dissolve the salt and mix it with the soil, let it stand, compact it in layers and control the dry density to 1.70 g / cm³; place polishing electrodes on both sides of the sample and seal it.

4. The method for testing the ice content of 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 maintain the temperature at 30℃ until the soil sample temperature stabilizes. Then, a step-by-step cooling process is performed, with each temperature level held constant for 12 hours. Simultaneously, the real-time temperature signal is fed back to the computer.

5. An apparatus for testing the ice content of soil based on electrochemical impedance spectroscopy, capable of performing the method for testing the ice content of soil based on electrochemical impedance spectroscopy as described in any one of claims 1-4, characterized in that, It includes 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, the data acquisition module, and the data analysis module respectively, and is used to globally control the test process, receive acquired data, trigger analysis commands, 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 testing module and controls the temperature of the soil sample through stepped cooling. When the temperature drops to the negative temperature range, the cooling is adjusted at 3°C ​​intervals. The test module includes a DC load module, an AC source module, and a sample placement device, which are used to apply a preset disturbance signal to the soil and collect the response signal. The data acquisition module is connected to the test module and collects 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. It is used to calculate the experimental value of the electrochemical impedance modulus of the soil sample throughout the cooling process using the electrochemical impedance data analysis software, and to fit the curve of the experimental value of the electrochemical impedance modulus in the unfrozen state with the temperature signal to obtain the fitted value of the electrochemical impedance modulus of the soil sample in the unfrozen state under any temperature conditions. The experimental value of the electrochemical impedance modulus, the fitted value of the electrochemical impedance modulus, and the initial water content of the soil sample are then input into the soil ice content calculation model to obtain the ice content of the soil sample. The data storage module categorizes and stores raw data, fitted values ​​of electrochemical impedance modulus, and calculation results of ice content.

6. The device for testing the ice content of soil based on electrochemical impedance spectroscopy according to claim 5, characterized in that, The test module includes: The DC load module is used to eliminate electrode polarization effect and maintain the stability of the test circuit impedance. The AC source module is used to generate disturbance signals of different frequencies and supports 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 resistance, the sealed cavity is used to reduce environmental interference, and the pressure sensor is used to monitor the contact pressure between the compacted soil sample and the gold electrode pair in real time.

7. The device for testing the ice content of soil based on electrochemical impedance spectroscopy according to claim 5, characterized in that, The control module and the test module communicate with each other using fiber optic isolation.

8. The device for testing the ice content of soil based on electrochemical impedance spectroscopy according to claim 5, characterized in that, The gold electrode pairs of the sample placement device are movable, and the electrode spacing is adjusted according to the length of the compacted soil sample.

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