A soil salt content detection method and device based on double-probe thermal decoupling

Abstract

A soil salt content detection method and device based on double-probe thermal-electric decoupling belong to the technical field of geotechnical engineering and soil in-situ detection, a water-salt coupling relationship between soil initial electric response parameters and water content and salt content is established, and the electric response contribution caused by water content change in the initial electric response parameters is determined; a water content inversion relationship between soil thermal response parameters and water content is established; before applying a thermal excitation, the initial electric response parameters of the soil to be measured are collected through the electrode conductor between the excitation probe and the identification probe; then the excitation probe applies a thermal excitation to the soil to be measured, and the temperature response curve is collected through the identification probe, and the thermal response parameters are extracted from the temperature response curve; the water content of the soil to be measured is inverted according to the thermal response parameters; the water content contribution in the initial electric response parameters is corrected by using the inverted water content, and the corrected electric response parameters are obtained; and the salt content of the soil to be measured is interpreted according to the corrected electric response parameters.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and in-situ soil testing technology, and relates to a method and equipment for detecting soil salinity based on dual-probe thermoelectric decoupling. It is applicable to the rapid detection and continuous monitoring of salinity in saline soil subgrades, cold region engineering, infrastructure in salt lake areas, soil in groundwater-affected areas, and other saline soils. Background Technology

[0002] Saline soils are widely distributed in arid, semi-arid, coastal, salt lake, and cold-arid regions. Soluble salts in the soil significantly affect water migration, salt swelling deformation, freeze-thaw deformation, strength attenuation, and long-term stability. Accurately obtaining soil salinity is crucial for the classification, diagnosis, construction quality control, and long-term service performance evaluation of saline soils in railway, highway, airport runway, canal, and infrastructure construction in salt lake areas. Existing methods for detecting soil salinity mainly include the drying and weighing method, the leachate conductivity method, ion chromatography, titration, and X-ray diffraction. While these methods offer high accuracy, they typically require on-site sampling, sample transportation, indoor extraction, and chemical analysis, resulting in long testing cycles and complex procedures. This makes it difficult to meet the need for rapid and continuous on-site acquisition of soil salinity from multiple points. Furthermore, the sampling process can easily damage the original soil structure and water-salt distribution, leading to test results that may not accurately reflect the true salinity of the soil at the site.

[0003] Resistivity, conductivity, and impedance methods offer advantages such as fast testing speed, simple equipment structure, and suitability for field applications, making them suitable for indirectly characterizing soil salinity. However, soil electrical response parameters are not a single function of salinity but are influenced by factors such as water content, salinity, temperature, dry density, and pore structure. In unsaturated soils, changes in water content alter pore water connectivity and electrical conductivity paths, meaning that increases in both water content and salinity can lead to similar changes in electrical response parameters. Therefore, interpreting salinity solely based on electrical response parameters is not unique and can easily introduce water-salt coupling errors. Soil thermal response parameters are closely related to water content. Due to the significant differences in the thermal properties of water, air, and soil particles, thermal response characteristics such as the temperature rise amplitude, heating rate, cooling rate, temperature recovery time, and apparent thermal conductivity under external thermal excitation can be used to characterize soil water content. Therefore, a soil moisture content benchmark can be obtained through thermal response parameters, and this benchmark can then be used to correct the contribution of moisture content changes in the electrical response parameters, thereby improving the accuracy of the electrical interpretation of salinity. Existing thermal pulse-time domain reflectometry (TDR) probes can acquire moisture content, salinity, and thermal parameters in the same device; however, their moisture and salinity measurements mainly rely on electromagnetic or electrical response measurements, while the thermal response portion is primarily used for acquiring thermal parameters or water flow. Although this type of method achieves integrated testing functions, it does not establish a separate interpretation relationship between the moisture content and salinity contributions in the electrical response parameters, nor does it disclose the processing flow for correcting the moisture content contribution of the electrical response parameters after inverting the moisture content using the thermal response. Summary of the Invention

[0004] This invention addresses the problems of existing technologies by providing a method and device for detecting soil salinity based on dual-probe thermo-electric decoupling. It can first obtain a moisture content benchmark through thermal response parameters, and then use the moisture content benchmark to correct the moisture content contribution in the initial electrical response parameters, thereby obtaining corrected electrical response parameters that better characterize the changes in salinity, and interpreting the soil salinity accordingly.

[0005] A soil salinity detection device based on dual-probe thermo-electric decoupling includes a power supply module, an excitation probe, an identification probe, a thermal excitation control module, an electrical signal excitation and acquisition module, a temperature acquisition module, a data acquisition module, and a data processing and analysis unit.

[0006] A method for detecting soil salinity based on dual-probe thermo-electric decoupling includes the following steps: establishing a water-salt coupling relationship between the initial electrical response parameters of the soil and its water content and salinity, used to characterize the electrical response contributions caused by changes in water content and salinity in the initial electrical response parameters; establishing a water content inversion relationship between the soil's thermal response parameters and its water content, the thermal response parameters being obtained from the soil's temperature response curve under thermal excitation; inserting or embedding an excitation probe and an identification probe into the soil to be tested, and before applying thermal excitation, detecting the salinity of the soil by means of the excitation probe... The electrode conductor between the needle and the identification probe collects the initial electrical response parameters of the soil to be tested. After the initial electrical response parameters are collected, thermal excitation is applied to the soil to be tested through the excitation probe, and the temperature response curve of the soil to be tested is collected through the identification probe. The thermal response parameters are extracted from the temperature response curve. The water content of the soil to be tested is obtained according to the inversion relationship between the thermal response parameters and the water content. The water content contribution in the initial electrical response parameters is corrected according to the water content of the soil to be tested to obtain the corrected electrical response parameters. The salt content of the soil to be tested is obtained according to the interpretation relationship between the corrected electrical response parameters and the salt content.

[0007] A soil salinity detection device based on dual-probe thermo-electric decoupling includes a power module to provide stable power to the device, an excitation probe (including a heating element and an electrode conductor) to apply thermal excitation to the soil and input electrical signals, an identification probe (including a temperature sensor and an electrode conductor) to acquire the temperature response of the soil and receive its electrical response signal, a thermal excitation control module to control the heating element in the excitation probe to apply thermal excitation to the soil, a temperature acquisition module to acquire the temperature response signal obtained by the temperature sensor in the identification probe, an electrical signal excitation and acquisition module to apply electrical excitation to the soil through the electrode conductors in the excitation and identification probes and acquire initial electrical response parameters, a data acquisition module to acquire and store the thermal response signal, electrical response signal, and ambient temperature signal, and a data processing and analysis unit to invert the soil moisture content based on the thermal response parameters, correct the moisture content contribution in the initial electrical response parameters to obtain corrected electrical response parameters, and interpret the salinity of the soil based on the corrected electrical response parameters.

[0008] Compared with the prior art, the present invention has the following beneficial effects.

[0009] First, this invention establishes a water-salt coupling relationship between initial electrical response parameters, water content, and salinity, and uses the water content obtained by inversion from thermal response parameters to correct the contribution of water content in the initial electrical response parameters, which can reduce the influence of water content changes on the electrical interpretation results of salinity.

[0010] Second, the present invention transforms the initial electrical response parameters, which are simultaneously affected by moisture content and salinity, into modified electrical response parameters, making the modified electrical response parameters more suitable for salinity interpretation, thereby improving the stability of soil salinity detection results under different moisture conditions.

[0011] Third, the present invention obtains a moisture content benchmark through thermal response parameters, and then uses the moisture content benchmark to correct the electrical response parameters, thereby realizing the coupled utilization of thermal response parameters and electrical response parameters at the data interpretation level, which is different from the detection method that only integrates thermal measurement function and electrical measurement function into the same device.

[0012] Fourth, the present invention collects the initial electrical response parameters before applying thermal excitation, which can obtain the electrical response information of the soil under test at the initial temperature state, thus avoiding the influence of temperature changes caused by thermal excitation on the initial electrical response parameters.

[0013] Fifth, this invention obtains electrical and thermal response parameters within the same or overlapping test area by using excitation probes and identification probes, which can reduce spatial mismatch errors caused by separate thermal and electrical tests and improve the applicability of the thermal response moisture content benchmark for correcting electrical response parameters.

[0014] Sixth, the present invention has a simple structure, small test disturbance, and fast response speed. It can be used for indoor testing, in-situ detection and long-term continuous monitoring. It is suitable for the detection of salinity in saline soil subgrades, cold region engineering, infrastructure in salt lake areas and soil in groundwater-affected areas.

[0015] Seventh, the present invention can obtain the differences in thermal and electrical responses of different types of soil, and use these differences to establish characteristic relationships corresponding to soil moisture content and salinity, thereby improving the adaptability of the detection model to different soil conditions.

[0016] Eighth, this invention can extract a variety of thermoelectric response characteristic parameters from the original electrical response data and temperature response curves, and reduce the impact of single parameter test fluctuations on the detection results through multi-feature joint characterization, thereby improving the stability of soil water and salt state identification.

[0017] Ninth, this invention can calibrate standard soil samples and update models based on different soil types, dry densities, initial temperatures, and salinity types, and can use multiple sets of dual probes for multi-point deployment, making it suitable for rapid on-site detection and long-term continuous monitoring. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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. As shown in the figures: Figure 1 This is the overall flowchart of the present invention.

[0019] Figure 2 This is a schematic diagram of the dual-probe structure of the present invention.

[0020] Figure 3 This is a schematic diagram of the probe thermal and electrical response test path of the present invention.

[0021] Figure 4 This is a schematic diagram of the dual-probe thermal response test path and temperature response curve acquisition of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below 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 embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: As Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, a method and device for detecting soil salinity based on dual-probe thermoelectric decoupling is presented, which solves the problems that a single electrical response parameter is difficult to distinguish between the effects of water content and salinity, that existing thermoelectric combined probes focus on integrated testing functions but lack a water-salt contribution separation and interpretation process, and that it is difficult to quickly detect and continuously monitor soil salinity on site.

[0024] A method for detecting soil salinity based on dual-probe thermoelectric decoupling includes the following steps.

[0025] Step S1: Establish the water-salt coupling relationship between the initial electrical response parameters of the soil and its moisture content and salinity. The water-salt coupling relationship is used to characterize the contributions of the initial electrical response parameters caused by changes in moisture content and salinity. The water-salt coupling relationship can be expressed as: E = F ( i , C s , T , rd ) In the formula, E These are the initial electrical response parameters. i Soil moisture content, C s This refers to the soil salinity. T The initial temperature of the soil. r d This represents the dry density of the soil.

[0026] Step S2: Establish the water content inversion relationship between soil thermal response parameters and water content. The thermal response parameters are obtained from the soil's temperature response curve under thermal excitation. The water content inversion relationship can be expressed as: i = g ( H , T , r d ) In the formula, i Soil moisture content, H These are the thermal response parameters extracted from the temperature response curve, where T is the initial temperature of the soil. r d The dry density of the soil. Thermal response parameters include one or more of the following: temperature rise amplitude, heating rate, cooling rate, time to peak temperature, temperature recovery time, integral value of temperature response, apparent thermal conductivity, and apparent thermal diffusivity.

[0027] Step S3 involves inserting or embedding the excitation probe and identification probe into the soil to be tested. Before applying thermal excitation, the initial electrical response parameters of the soil are collected through the electrode conductor between the excitation probe and the identification probe. These initial electrical response parameters include one or more of the following: resistance, resistivity, conductivity, impedance modulus, phase angle, real part of complex impedance, and imaginary part of complex impedance. The electrical excitation can be DC excitation, single-frequency AC excitation, multi-frequency AC excitation, or frequency scanning electrical excitation.

[0028] Step S4: After completing the initial electrical response parameter acquisition, thermal excitation is applied to the soil under test using an excitation probe, and the temperature response curve of the soil under test is acquired using an identification probe. Thermal response parameters are then extracted from the temperature response curve. Thermal excitation can employ constant power thermal pulses, short-duration thermal pulses, or step-type thermal excitation. The temperature response curve is used to extract thermal response parameters and provides input for the inversion of the soil moisture content.

[0029] Step S5: Obtain the moisture content of the soil to be tested based on the thermal response parameters and the moisture content inversion relationship. The moisture content of the soil to be tested obtained from the thermal response parameters is used as the moisture content benchmark for correcting the initial electrical response parameters, and is used to subsequently correct the electrical response contribution caused by the change in moisture content in the initial electrical response parameters.

[0030] Step S6: Based on the moisture content of the soil to be tested, correct the contribution of moisture content to the initial electrical response parameters to obtain the corrected electrical response parameters. The corrected electrical response parameters can be expressed as: E ′= F ( E , i , T , r d ) In the formula, E ′ is to correct the electrical response parameters, E These are the initial electrical response parameters. i The soil moisture content is obtained by inversion from thermal response parameters. T The initial temperature of the soil. r d The dry density of the soil. The moisture content contribution correction includes one or more of the following: moisture content normalization, moisture content compensation, model calibration, table lookup correction, ratios or differences of electrical response parameters at different frequencies, normalized differences, or dispersion parameter construction.

[0031] Step S7: Obtain the salt content of the soil to be tested based on the corrected electrical response parameters and the salt content interpretation relationship. The salt content interpretation relationship can be expressed as: C s = f ( E′ , T , r d ) In the formula, C s The salt content of the soil to be tested. E ′ is to correct the electrical response parameters, T The initial temperature of the soil. r d This represents the dry density of the soil.

[0032] Furthermore, the water-salt coupling relationship, water content inversion relationship, water content contribution correction relationship, and salinity interpretation relationship were obtained through standard soil sample calibration. Standard soil samples included soil samples under different water contents, salinities, and dry densities, and the initial temperature at the time of testing was recorded. The above relationships could be established using standard soil samples through linear regression, nonlinear regression, table lookup interpolation, support vector regression, random forest, neural networks, or other data fitting methods.

[0033] Example 2: Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, the present invention provides a soil salinity detection device based on dual-probe thermo-electric decoupling, including a power supply module, an excitation probe, an identification probe, a thermal excitation control module, a temperature acquisition module, an electrical signal excitation and acquisition module, a data acquisition module, and a data processing and analysis unit.

[0034] The power module provides stable power to the testing equipment. The excitation probe, including a heating element and electrode conductors, applies thermal excitation to the soil under test and inputs electrical signals to it. The identification probe, including a temperature sensor and electrode conductors, acquires the temperature response of the soil under test and receives its electrical response signal. The thermal excitation control module controls the heating element in the excitation probe to apply thermal excitation to the soil under test. The temperature acquisition module acquires the temperature response signal obtained by the temperature sensor in the identification probe. The electrical signal excitation and acquisition module applies electrical excitation to the soil under test through the electrode conductors in the excitation and identification probes and acquires initial electrical response parameters. The data acquisition module acquires and stores the thermal response signal, electrical response signal, and ambient temperature signal. The data processing and analysis unit inverts the moisture content of the soil under test based on the thermal response parameters, corrects the moisture content contribution in the initial electrical response parameters using the moisture content, obtains the corrected electrical response parameters, and interprets the salinity of the soil under test based on the corrected electrical response parameters.

[0035] like Figure 2 As shown, the dual-probe detection assembly includes a housing base, an excitation probe, an identification probe, and a data transmission line. The excitation probe and the identification probe are arranged parallel to each other, with their upper ends fixed to the housing base and their lower ends for insertion or embedding in the soil to be tested. The excitation probe is equipped with a heating element and a first electrode conductor, wherein the heating element applies thermal excitation to the soil to be tested, and the first electrode conductor inputs an electrical signal to the soil to be tested. The identification probe is equipped with a temperature sensor and a second electrode conductor, wherein the temperature sensor acquires the temperature response signal of the soil to be tested, and the second electrode conductor receives the electrical response signal of the soil to be tested. The heating element, temperature sensor, first electrode conductor, and second electrode conductor are connected to the data transmission line via the housing base, and the data transmission line is further connected to a thermal excitation control module, a temperature acquisition module, an electrical signal excitation and acquisition module, and a data acquisition module.

[0036] like Figure 3As shown, the dual-probe detection assembly is used to test the thermal and electrical responses of different types of soil. The excitation probe and the identification probe are inserted or buried parallel to each other in the soil at a predetermined interval. The first electrode conductor in the excitation probe, the second electrode conductor in the identification probe, and the soil between the two probes together form the electrical response test path, used to collect the initial electrical response parameters of the soil. After the initial electrical response parameters are collected, the heating element in the excitation probe applies thermal excitation to the soil. Heat is transferred from the excitation probe to the identification probe, and the temperature response is collected by the temperature sensor in the identification probe, thus forming the thermal response test path.

[0037] Because different soil types differ in their particle composition, pore structure, moisture content, salinity, and dry density, their electrical and thermal conductivity vary. Therefore, even with identical probe structure, probe spacing, electrical excitation conditions, and thermal excitation conditions, different soil types may exhibit differences in electrical response parameters such as resistance, conductivity, impedance, and phase angle, as well as thermal response parameters such as temperature rise amplitude, heating rate, time to peak temperature, cooling rate, and temperature recovery time. Figure 3 This is used to illustrate the differences in thermal and electrical response characteristics of different types of soil, and to provide a basis for establishing corresponding water-salt coupling relationships and moisture content inversion relationships for different soil types.

[0038] like Figure 4 The diagram illustrates the data acquisition and characteristic parameter extraction process for dual-probe thermoelectric testing. Under conditions without thermal excitation, electrical excitation is applied to the soil sample through the first electrode conductor in the excitation probe and the second electrode conductor in the identification probe, and the soil's electrical response data is collected. Depending on the electrical excitation method used, electrical response results under DC, single-frequency AC, multi-frequency AC, or frequency scanning conditions can be obtained, and characteristic electrical response parameters such as resistance, resistivity, conductivity, impedance modulus, phase angle, real part of complex impedance, and imaginary part of complex impedance can be extracted.

[0039] After initial electrical response data acquisition, thermal excitation is applied to the soil under test through the heating element in the excitation probe, and temperature change data is continuously collected at set sampling intervals using the temperature sensor in the identification probe to obtain the temperature-time response curve. Based on the temperature response curve, thermal response characteristic parameters such as temperature rise amplitude, heating rate, peak temperature, peak temperature occurrence time, cooling rate, temperature recovery time, temperature response integral value, apparent thermal conductivity, and apparent thermal diffusivity can be extracted.

[0040] The extracted electrical and thermal response characteristic parameters together constitute the thermoelectric response data features of the soil under test. The thermal response features are primarily used to characterize the soil's water content, while the electrical response features are influenced by both the soil's water content and salinity. These characteristic parameters can serve as input data for subsequently establishing the inversion relationship between thermal response parameters and water content, the water-salt coupling relationship between initial electrical response parameters and water content and salinity, and for correcting the interpretation relationship between electrical response parameters and salinity.

[0041] Example 3: As Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, this invention first establishes the water-salt coupling relationship between the initial electrical response parameters of soil and its moisture content and salinity. Representative soil materials are selected to prepare standard soil samples under different moisture contents, salinities, and dry densities. The electrical response of each standard soil sample is tested using a dual-probe testing device to obtain the initial electrical response parameters of the soil under different conditions. The initial electrical response parameters include one or more of the following: resistance, resistivity, conductivity, impedance modulus, phase angle, real part of complex impedance, and imaginary part of complex impedance.

[0042] Based on the initial electrical response parameters obtained under different conditions, the correspondence between the initial electrical response parameters and moisture content, salinity, initial temperature, and dry density is established: E = F ( i , C s , T , r d ) In the formula, E These are the initial electrical response parameters. i Soil moisture content, C s This refers to the soil salinity. T The initial temperature of the soil. r d This represents the dry density of the soil.

[0043] Since soil electrical response parameters are affected by both moisture content and salinity, directly interpreting salinity using initial electrical response parameters results in water-salt coupling errors. This invention achieves accurate salinity interpretation by further obtaining soil thermal response parameters to invert moisture content and then using the obtained moisture content information to correct the initial electrical response parameters.

[0044] After completing the initial electrical response parameter acquisition, thermal excitation is applied to the soil under test, and the soil temperature response change process is acquired simultaneously.

[0045] Thermal response parameters are extracted from the temperature response curve. These parameters include one or more of the following: temperature rise amplitude, heating rate, cooling rate, time to peak temperature, temperature recovery time, integral value of temperature response, apparent thermal conductivity, and apparent thermal diffusivity. Based on standard soil sample test results, a correspondence between the thermal response parameters and soil moisture content is established. i = g ( H , T , r d ) In the formula, i Soil moisture content, H These are the thermal response parameters extracted from the temperature response curve, where T is the initial temperature of the soil. r d This represents the dry density of the soil.

[0046] The contribution of moisture content in the initial electrical response parameters is corrected based on the moisture content obtained from the thermal response parameters. Specifically, a correction relationship is established based on the initial electrical response parameter E, the obtained moisture content, the initial temperature, and the dry density: E ′= F ( E , i , T , r d ) In the formula, E ′ is to correct the electrical response parameters, E These are the initial electrical response parameters. i The soil moisture content is obtained by inversion from thermal response parameters. T The initial temperature of the soil. r d This represents the dry density of the soil.

[0047] Through the above correction process, the influence of moisture content changes on electrical response parameters is reduced, enabling the corrected electrical response parameters to more effectively reflect changes in soil salinity. Furthermore, the interpretable relationship between the corrected electrical response parameters and salinity is established: C s = f ( E′ , T , r d ) In the formula, C s The salt content of the soil to be tested. E ′ is to correct the electrical response parameters, T The initial temperature of the soil. rd This represents the dry density of the soil.

[0048] The salt content of the soil to be tested can be obtained using this interpretation relationship.

[0049] This invention employs a dual-probe detection device to simultaneously acquire thermal response parameters and electrical response parameters.

[0050] Dual-probe detection equipment includes an excitation probe and a recognition probe.

[0051] The excitation probe includes an electrode conductor and a thermal excitation element, which are used to input electrical signals to the soil under test and apply thermal excitation.

[0052] The identification probe includes an electrode conductor and a temperature sensor, used to collect the electrical and temperature response signals of the soil under test.

[0053] During the testing process, the initial electrical response parameters of the soil under test are first collected using the electrical response test path formed between the excitation probe and the identification probe.

[0054] Subsequently, thermal excitation is applied to the soil under test through a thermal excitation element, and the soil temperature response process is collected using a temperature sensor.

[0055] Since the electrical response parameters and thermal response parameters correspond to the same or overlapping test areas, the moisture content obtained by inverting the thermal response parameters can be used to correct the moisture content contribution in the initial electrical response parameters within the corresponding area.

[0056] The corrected electrical response parameters are obtained by correcting the contribution of the water content in the initial electrical response parameters to the water content of the soil under test, and are expressed as follows: E ′= F ( E , i , T , r d ) In the formula, E ′ is to correct the electrical response parameters, E These are the initial electrical response parameters. i The soil moisture content is obtained by inversion from thermal response parameters. T The initial temperature of the soil. r d This represents the dry density of the soil.

[0057] The salt content interpretation relation is used to describe the correspondence between the corrected electrical response parameters and the salt content of the soil being measured, and is expressed as: C s = f ( E′ , T , r d ) In the formula, C s The salt content of the soil to be tested. E ′ is to correct the electrical response parameters, T The initial temperature of the soil. r d This represents the dry density of the soil.

[0058] The initial electrical response parameters include one or more of the following: resistance, resistivity, conductivity, impedance magnitude, phase angle, real part of complex impedance, and imaginary part of complex impedance. The electrical excitation can be DC excitation, single-frequency AC excitation, multi-frequency AC excitation, or frequency scanning excitation. When using single-frequency AC excitation, multi-frequency AC excitation, or frequency scanning excitation, the initial electrical response parameters include the resistivity, conductivity, impedance magnitude, phase angle, and real or imaginary part of complex impedance at the corresponding frequency.

[0059] Thermal response parameters include one or more of the following: temperature rise amplitude, heating rate, cooling rate, time to peak temperature, temperature recovery time, integral value of temperature response, apparent thermal conductivity, and apparent thermal diffusivity.

[0060] Moisture content contribution correction includes one or more of the following: moisture content normalization, moisture content compensation, model calibration, table lookup correction, ratios or differences of electrical response parameters at different frequencies, normalized differences, or dispersion parameter construction.

[0061] The water-salt coupling relationship, water content inversion relationship, water content contribution correction relationship, and salt content interpretation relationship were obtained through standard soil sample calibration. The standard soil samples included soil samples under different water contents, different salt contents, and different dry densities, and the initial temperature at the time of testing was recorded.

[0062] A soil salinity detection device based on dual-probe thermoelectric decoupling includes: The power module is used to provide power to the testing equipment; An excitation probe, including a heating element and an electrode conductor, is used to apply thermal excitation to the soil and to input electrical signals into the soil; The identification probe, including a temperature sensor and an electrode conductor, is used to acquire the soil temperature response and to receive the soil electrical response signal; The thermal excitation control module is used to control the heating element in the excitation probe to apply thermal excitation to the soil; The temperature acquisition module is used to acquire and identify the soil temperature response signal obtained by the temperature sensor in the probe; The electrical signal excitation and acquisition module is used to apply electrical excitation to the soil through the electrode conductors in the excitation probe and the identification probe, and to acquire the initial electrical response parameters of the soil. The data acquisition module is used to acquire and store thermal response signals, electrical response signals, and ambient temperature signals; The data processing and analysis unit is used to invert the soil moisture content based on the thermal response parameters, correct the moisture content contribution in the initial electrical response parameters using the soil moisture content, obtain the corrected electrical response parameters, and interpret the soil salinity based on the corrected electrical response parameters.

[0063] The excitation probe and the identification probe are arranged in parallel, and a set distance is maintained between the two probes; the excitation probe and the identification probe simultaneously form an electrical response test path and a thermal response test path, so that the initial electrical response parameters and thermal response parameters correspond to the same or overlapping soil test area; the heating element is one of resistance wire, heating film, miniature heating rod or metal heating core, the temperature sensor is one of thermocouple, thermistor or platinum resistance temperature sensor, and the electrode conductor is one of stainless steel electrode, copper electrode, graphite electrode or corrosion-resistant alloy electrode.

[0064] This invention reduces the impact of moisture content changes on the electrical interpretation results of salinity through a processing flow of "thermal response moisture content benchmark - electrical response moisture content contribution correction - salinity interpretation". It is suitable for rapid detection and continuous monitoring of salinity in saline soil subgrades, cold region engineering, infrastructure in salt lake areas, and soil in groundwater-affected areas.

[0065] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for detecting soil salinity based on dual-probe thermoelectric decoupling, characterized in that... The process includes the following steps: establishing the water-salt coupling relationship between the initial electrical response parameters of the soil and the water content and salt content, which is used to characterize the electrical response contribution caused by the change in water content and the electrical response contribution caused by the change in salt content in the initial electrical response parameters; A moisture content inversion relationship is established between soil thermal response parameters and moisture content. The thermal response parameters are obtained from the temperature response curve of the soil under thermal excitation. An excitation probe and an identification probe are inserted or buried in the soil to be tested. Before applying thermal excitation, the initial electrical response parameters of the soil to be tested are collected through the electrode conductor between the excitation probe and the identification probe. After the initial electrical response parameters are collected, thermal excitation is applied to the soil to be tested through the excitation probe, and the temperature response curve of the soil to be tested is collected through the identification probe. The thermal response parameters are extracted from the temperature response curve. The moisture content of the soil to be tested is obtained based on the thermal response parameters and the moisture content inversion relationship. Based on the moisture content of the soil to be tested, the contribution of moisture content in the initial electrical response parameters is corrected to obtain the corrected electrical response parameters. The salinity of the soil to be tested is obtained by interpreting the modified electrical response parameters and salinity.

2. The method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, Includes the following steps: The thermal response parameters are obtained from the temperature response curves of the soil under thermal excitation. The excitation probe and the identification probe are inserted or buried in the soil to be tested. After the initial electrical response parameters are acquired, the temperature response curve of the soil under test is acquired by the identification probe, and the thermal response parameters are extracted from the temperature response curve. The moisture content of the soil to be tested is obtained based on the thermal response parameters and the moisture content inversion relationship. Based on the moisture content of the soil to be tested, the contribution of moisture content in the initial electrical response parameters is corrected to obtain the corrected electrical response parameters. The salinity of the soil to be tested is obtained by interpreting the modified electrical response parameters and salinity.

3. The method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, The water-salt coupling relationship is used to describe the correspondence between initial electrical response parameters and soil moisture content, salt content, initial temperature, and dry density, and is expressed as: E = F ( θ , C s , T , ρ d ) In the formula, E These are the initial electrical response parameters. θ The soil moisture content, C s This refers to the soil salinity. T The initial temperature of the soil. ρ d This represents the dry density of the soil.

4. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, The moisture content inversion relationship is used to describe the correspondence between thermal response parameters and soil moisture content, and is expressed as: θ = g ( H , T , ρ d ) In the formula, θ The soil moisture content, H These are the thermal response parameters extracted from the temperature response curve, where T is the initial temperature of the soil. ρ d This represents the dry density of the soil.

5. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, The corrected electrical response parameters are obtained by correcting the contribution of the water content in the initial electrical response parameters to the water content of the soil under test, and are expressed as follows: E ′= Φ ( E , θ , T , ρ d ) In the formula, E ′ is to correct the electrical response parameters, E These are the initial electrical response parameters. θ The soil moisture content is obtained from the inversion of thermal response parameters. T The initial temperature of the soil. ρ d This represents the dry density of the soil.

6. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 2, characterized in that, The salt content interpretation relation is used to describe the correspondence between the corrected electrical response parameters and the salt content of the soil being measured, and is expressed as: C s = f ( E′ , T , ρ d ) In the formula, C s The salt content of the soil to be tested. E ′ is to correct the electrical response parameters, T The initial temperature of the soil. ρ d This represents the dry density of the soil.

7. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, The initial electrical response parameters include one or more of the following: resistance, resistivity, conductivity, impedance magnitude, phase angle, real part of complex impedance, and imaginary part of complex impedance. The electrical excitation is DC excitation, single-frequency AC excitation, multi-frequency AC excitation, or frequency scanning excitation. When using single-frequency AC excitation, multi-frequency AC excitation, or frequency scanning excitation, the initial electrical response parameters include resistivity, conductivity, impedance magnitude, phase angle, real part of complex impedance, or imaginary part of complex impedance at the corresponding frequency.

8. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, Thermal response parameters include one or more of the following: temperature rise amplitude, heating rate, cooling rate, time to peak temperature, temperature recovery time, integral value of temperature response, apparent thermal conductivity, and apparent thermal diffusivity. Moisture content contribution correction includes one or more of the following: moisture content normalization, moisture content compensation, model calibration, table lookup correction, ratios, differences, normalized differences, or dispersion parameter construction at different frequencies.

9. A method for detecting soil salinity based on dual-probe thermoelectric decoupling according to claim 1, characterized in that, The water-salt coupling relationship, water content inversion relationship, water content contribution correction relationship, and salt content interpretation relationship were obtained through standard soil sample calibration. The standard soil samples included soil samples under different water contents, different salt contents, and different dry densities, and the initial temperature at the time of testing was recorded.

10. A soil salinity detection device based on dual-probe thermoelectric decoupling, characterized in that, The power supply module provides stable power to the testing equipment. The excitation probe, including a heating element and an electrode conductor, applies thermal excitation to the soil under test and inputs electrical signals to it. The identification probe, including a temperature sensor and an electrode conductor, acquires the temperature response of the soil under test and receives its electrical response signal. The thermal excitation control module controls the heating element in the excitation probe to apply thermal excitation to the soil under test. The temperature acquisition module acquires the temperature response signal obtained by the temperature sensor in the identification probe. The electrical signal excitation and acquisition module applies electrical excitation to the soil under test through the electrode conductors in the excitation and identification probes and acquires initial electrical response parameters. The data acquisition module acquires and stores the thermal response signal, electrical response signal, and ambient temperature signal. The data processing and analysis unit inverts the moisture content of the soil under test based on the thermal response parameters, corrects the moisture content contribution in the initial electrical response parameters using the moisture content, obtains the corrected electrical response parameters, and interprets the salinity of the soil under test based on the corrected electrical response parameters.

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