Quantitative analysis method and device for water-salt phase change of saline soil

Abstract

The application provides a quantitative analysis method and device for water-salt phase change of saline soil, which comprises the following steps: S1, preparing a saline soil sample and placing the saline soil sample in a sample cup, a first sensor being in contact with the saline soil sample to detect the temperature and humidity of the saline soil sample; S2, placing a isolation cover on the outside cover of the sample cup and making X-rays pass through the isolation cover and the saline soil sample in sequence; S3, setting a target temperature of the sample cup, collecting the temperature data of the saline soil sample and the humidity data of the saline soil sample, and an XRD diffraction pattern in the process of temperature change or constant temperature through the first sensor 3; S4, establishing a quantitative relationship model of temperature-humidity-salt crystallization and a quantitative relationship model of temperature-humidity-dissolution phase state of the saline soil sample according to the temperature data of the saline soil sample, the humidity data of the saline soil sample and the XRD diffraction pattern; and the crystal type, crystallization rate and crystallization amount at different temperatures of the dissolution phase state of the saline soil sample.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering testing technology, specifically to a quantitative analysis method and apparatus for water-salt phase transition in saline soil. Background Technology

[0002] Saline soils are widely distributed in arid, semi-arid, and coastal areas, and their engineering properties are significantly affected by internal water-salt phase transitions (such as salt crystallization and dissolution, and ice formation and melting). Quantitative studies on the dynamic processes of water migration and salt crystallization / dissolution in saline soils under different temperature conditions are of great value in revealing the mechanisms of freeze-thaw damage and salt swelling corrosion.

[0003] Currently, most studies on the water-salt phase transition in saline soils employ indirect methods, such as using differential scanning calorimetry (DSC) to determine the latent heat of phase transition, or inferring the phase transition process by measuring physical parameters such as electrical resistance and ultrasonic velocity. These methods struggle to directly identify and quantify the formation and disappearance of specific salt crystals. X-ray diffraction (XRD) is the authoritative method for identifying crystalline substances; however, traditional XRD sample stages struggle to achieve precise control over a wide temperature range (especially negative temperatures), and cannot maintain the required humidity environment for the sample or monitor its internal state during testing. Directly placing soil samples in a low-temperature environment for XRD testing causes surface frost, moisture evaporation, or condensation, severely interfering with the test results and making it impossible to obtain the true internal temperature and humidity parameters of the sample during the phase transition, resulting in an inaccurate correlation between XRD data and the phase transition state.

[0004] Therefore, a method for identifying crystalline substances needs to be designed to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a quantitative analysis method and apparatus for the water-salt phase transition of saline soil.

[0006] This invention is achieved through the following technical solution: A quantitative analysis method for the water-salt phase transition in saline soil includes the following steps: S1. Prepare a saline soil sample and place it in a sample cup to detect the temperature and humidity of the saline soil sample; S2. Cover the outside of the sample cup with an isolation cover and allow the X-rays to pass through the isolation cover and the saline soil sample in sequence; S3. Set the target temperature of the sample cup, and collect the temperature data and humidity data of the saline soil sample, as well as the XRD diffraction pattern, during the temperature change or constant temperature process. S4. Based on the temperature data, humidity data and XRD diffraction patterns of the saline soil samples, establish quantitative relationship models of temperature-humidity-salt crystallization and temperature-humidity-dissolved phases of the saline soil samples. The dissolved phase of saline soil samples includes crystal type, crystallization rate, and amount of crystallization at different temperatures.

[0007] Furthermore, step S3 also includes: The scanning parameters of the X-ray diffractometer were set, and the saline soil sample was scanned by the X-ray diffractometer to generate an XRD diffraction pattern.

[0008] Furthermore, the scanning parameters include a first unit interval, during which the X-ray diffractometer scans the saline soil sample in the sample cup every time the first unit interval changes.

[0009] Furthermore, in step S3, the target temperature of the sample cup includes a first isothermal stage, a variable temperature stage, and a second isothermal stage. After the first isothermal stage, it enters the variable temperature stage, and finally enters the second isothermal stage.

[0010] Furthermore, the temperature of the first isothermal stage is higher than that of the second isothermal stage, and the duration of the first isothermal stage is shorter than that of the second isothermal stage.

[0011] Furthermore, the temperature of the first isothermal stage is set to 8°C to 12°C, and the duration is set to 5 min to 15 min; The temperature change rate during the temperature change phase was set to 0.2℃ / min to 0.8℃ / min, and the duration was set to 40min to 60min. The temperature for the second isothermal stage is set to -10℃ to -20℃, and the duration is set to 50min to 70min.

[0012] Furthermore, during the temperature-changing phase, the temperature inside the sample cup is changed at a constant rate, and the duration of the temperature-changing phase is between the duration of the first isothermal phase and the duration of the second isothermal phase.

[0013] A quantitative analysis device for the water-salt phase transition of saline soil includes: X-ray diffractometer, used to scan saline soil samples to generate XRD diffraction patterns; The sample base has a sample cup on it, and a saline soil sample is placed inside the sample cup. The side wall of the sample cup has an insertion hole, through which the first sensor can enter the sample cup and come into contact with the saline soil sample. The sample base has a temperature control component that can adjust the temperature of the saline soil sample. The sample cup is used to cover the saline soil sample on the sample base.

[0014] Furthermore, the top of the sample cup is provided with a first window for X-ray incident and a second window for X-ray diffraction.

[0015] Furthermore, the inner wall of the sample cup is coated with an anti-condensation coating.

[0016] The advantages and beneficial effects of this invention are as follows: By allowing the first sensor to directly contact the saline soil sample to obtain real temperature and humidity data, and simultaneously combining the temperature and humidity changes with the XRD diffraction patterns during the isothermal process, direct and accurate quantitative analysis of the phase changes of specific salt crystals during the water-salt phase transition of saline soil is achieved. This overcomes the limitations of indirect inference and solves the problem of disconnect between XRD testing and sample temperature and humidity monitoring. It provides direct, systematic and accurate methodological support for revealing the freeze-thaw disease and salt swelling corrosion mechanism of saline soil, and makes up for the core shortcomings of existing technologies in the quantitative study of water-salt phase transition in saline soil. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the quantitative analysis method for water-salt phase transition in saline soil according to the present invention.

[0019] Figure 2 This is a top view of the quantitative analysis device for water-salt phase change in saline soil according to the present invention.

[0020] Figure 3 This is a front view of the quantitative analysis device for water-salt phase change in saline soil according to the present invention.

[0021] In the picture: 1. X-ray diffractometer; 2. Sample base; 21. Sample cup; 22. Temperature control component; 3. First sensor; 4. Isolation cover; 41. First window; 42. Second window; 43. Socket; 44. Sealing interface; 45. Anti-condensation coating; 5. Receiving component; S, saline soil sample. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0023] This embodiment provides a quantitative analysis method for the water-salt phase transition in saline soil, such as... Figures 1-3 As shown, it includes the following steps: S1. Prepare saline soil sample S, and place saline soil sample S into sample cup 21 to detect the temperature and humidity of saline soil sample S; S2. Cover the outside of the sample cup 21 with the isolation cover 4, and let the X-rays pass through the isolation cover 4 and the saline soil sample S in sequence; S3. Set the target temperature of sample cup 21. During the temperature change or constant temperature process, collect the temperature data and humidity data of saline soil sample S, as well as the XRD diffraction pattern. S4. Based on the temperature data, humidity data and XRD diffraction pattern of saline soil sample S, establish a quantitative relationship model of temperature-humidity-salt crystallization and a quantitative relationship model of temperature-humidity-dissolved phase of saline soil sample S. The dissolved phase of saline soil sample S includes crystal type, crystallization rate, and amount of crystallization at different temperatures.

[0024] Understandably, a complete quantitative analysis process for water-salt phase transition in saline soil, integrating temperature and humidity detection, X-ray diffraction scanning, and temperature control, has been constructed. This process directly combines temperature and humidity data with XRD diffraction patterns to establish a phase relationship model, overcoming the limitation of traditional methods that cannot directly correlate phase transition data with crystalline phases. This enables precise quantitative analysis of salt crystallization and dissolution phases in saline soil, providing direct and systematic methodological support for studying the water-salt phase transition mechanism in saline soil.

[0025] Furthermore, in step S2, after covering the sample cup with the isolation cover 4, the sample cup 21 and the isolation cover 4 are sealed.

[0026] Understandably, sealing the sample cup 21 and the isolation cover 4 can effectively maintain the humidity environment around the saline soil sample S, prevent the sample moisture from evaporating and the outside water vapor from entering, and prevent the sample surface from frosting at low temperatures. This eliminates the interference of environmental factors on temperature and humidity detection and XRD scanning, ensuring the authenticity and accuracy of the test data.

[0027] Furthermore, step S3 also includes setting the scanning parameters of the X-ray diffractometer 1 and scanning the saline soil sample S with the X-ray diffractometer 1 to generate an XRD diffraction pattern.

[0028] Understandably, by setting scanning parameters to standardize and control the scanning operation of X-ray diffractometer 1, it is possible to ensure that the XRD diffraction pattern can accurately reflect the crystalline phase changes of saline soil sample S during temperature change / isothermal processes, thus providing a reliable diffraction data basis for the subsequent establishment of phase relationship models.

[0029] Furthermore, the scanning parameters include a first unit interval, and the X-ray diffractometer 1 scans the saline soil sample S in the sample cup 21 every time the first unit interval changes.

[0030] Understandably, by using the first unit interval as the scanning trigger condition, the phased and regular XRD scanning of the saline soil sample S was achieved. This can accurately capture the salt crystallization / dissolution phase characteristics at different nodes during temperature changes, avoid missing key phase transition nodes, and ensure that the diffraction data is highly matched with the temperature change process, thereby improving the accuracy of phase analysis.

[0031] Specifically, the first unit interval can be a temperature interval or a time interval, such as automatically scanning once every 5 minutes or every 1°C change.

[0032] Furthermore, in step S3, the target temperature of the sample cup 21 includes a first isothermal stage, a variable temperature stage, and a second isothermal stage. After the first isothermal stage, it enters the variable temperature stage and finally enters the second isothermal stage.

[0033] Understandably, dividing the target temperature into three stages—"first isothermal, second isothermal, and third isothermal"—allows for the acquisition of phase state and temperature and humidity data of the saline soil sample in a stable state during the isothermal stage, while capturing real-time data of the dynamic phase transition process during the second temperature stage. This achieves full coverage detection of both the stable state and the dynamic phase transition process, making the establishment of the phase relationship model more comprehensive and in line with the temperature change law of saline soil in actual engineering.

[0034] Furthermore, the temperature of the first isothermal stage is higher than that of the second isothermal stage, and the duration of the first isothermal stage is shorter than that of the second isothermal stage.

[0035] Furthermore, the temperature of the first isothermal stage is set to 8℃ to 12℃, and the duration is set to 5min to 15min; the temperature change rate of the variable temperature stage is set to 0.2℃ / min to 0.8℃ / min, and the duration is set to 40min to 60min; the temperature of the second isothermal stage is set to -10℃ to -20℃, and the duration is set to 50min to 70min.

[0036] Understandably, setting the first isothermal stage to a higher temperature and shorter duration allows the saline soil sample S to quickly reach its initial stable state, shortening the time required for preliminary testing. The second isothermal stage to a lower temperature and longer duration allows for the full capture of the stable phase characteristics of salt crystallization in saline soil at low temperatures, adapting to the phase transition law of saline soil in low-temperature environments, and improving the sufficiency and testing efficiency of low-temperature phase detection.

[0037] Furthermore, during the temperature-changing phase, the temperature inside the sample cup 21 is changed at a constant rate of temperature change, and the duration of the temperature-changing phase is between the duration of the first isothermal phase and the duration of the second isothermal phase.

[0038] Understandably, a constant temperature change rate is used in the temperature-changing stage to make the temperature change process of saline soil controllable and reproducible, avoiding distortion of the phase change process caused by sudden temperature changes. At the same time, the duration of the temperature-changing stage is set between the two constant temperature stages, which takes into account the complete capture of the dynamic phase change process and the overall testing efficiency, and ensures the continuity and validity of the phase change process data.

[0039] This embodiment also provides a quantitative analysis device for the water-salt phase transition in saline soil, such as... Figure 2 and Figure 3 As shown, the quantitative analysis device for water-salt phase transition of saline soil includes an X-ray diffractometer 1, a sample base 2, and an isolation cover 4. The X-ray diffractometer 1 is used to scan the saline soil sample S to generate an XRD diffraction pattern. A sample cup 21 is provided on the sample base 2, and the saline soil sample S is placed inside the sample cup 21. An insertion hole 43 is provided on the side wall of the sample cup 21, through which the first sensor 3 can enter the sample cup 21 and contact the saline soil sample S. A temperature control component 22 is provided inside the sample base 2, which can adjust the temperature of the saline soil sample S. The isolation cover 4 can cover the saline soil sample S on the sample base 2.

[0040] Understandably, this device integrates real-time temperature and humidity detection with XRD diffraction scanning. The first sensor 3 can directly contact the sample, ensuring the accuracy of temperature and humidity data acquisition. The sample cup 21 and the isolation cover 4 can effectively fix the sample, solving the problem that traditional XRD sample stages cannot simultaneously achieve temperature and humidity monitoring and sample fixation.

[0041] Specifically, the insertion hole 43 is located at the bottom of the side wall of the sample cup 21, and the probe of the first sensor 3 extends into the center of the saline soil sample S.

[0042] Furthermore, the top of the isolation shield 4 is provided with a first window 41 for X-ray incidence and a second window 42 for X-ray diffraction.

[0043] Understandably, the first window 41 and the second window 42 are opened on the top of the isolation cover 4 to provide dedicated channels for X-ray incident and diffraction, respectively, to ensure that X-rays can smoothly penetrate the sample and complete the diffraction signal acquisition, avoid the shielding and interference of the sample cup 21 shell on X-rays, and ensure the clarity and effectiveness of the XRD diffraction pattern.

[0044] Optionally, the first window 41 and the second window 42 are configured as polyimide films.

[0045] Specifically, the device also includes a receiving component 5, which is used to receive signals from the first sensor 3 and control the working power of the temperature control component 22 through a PID algorithm according to a set program; the receiving component 5 is also equipped with a human-machine interface for setting parameters, displaying curves, and sending trigger signals to the X-ray diffractometer 1 to achieve scanning synchronization.

[0046] Specifically, the device also includes a sealing interface 44, which is used to accommodate sealing elements such as sealing strips between the isolation cover 4 and the sample base 2, ensuring the integrity of the device.

[0047] Furthermore, the inner wall of the isolation cover 4 is provided with an anti-condensation coating 45.

[0048] It is understandable that setting an anti-condensation coating 45 on the inner wall of the isolation cover 4 can effectively prevent water vapor inside the cup from condensing on the wall surface during low-temperature testing, avoid condensation water dripping onto the surface of the saline soil sample S and changing its humidity state and phase state, and at the same time prevent condensation water from interfering with the detection of temperature and humidity sensors and X-ray propagation, further ensuring the stability of the test environment and the accuracy of the test data.

[0049] The following example using Na2SO4 further illustrates this method: 1. Prepare Na2SO4 saline soil according to the actual project conditions, control the moisture content to 15%, and put it into sample cup 21. Insert the first sensor 3 into the center of sample cup 21 and Na2SO4 saline soil through the jack 43. 2. Place the assembled sample cup 21 on the sample base 2, fasten the isolation cover 4, and connect all cables; 3. Set the temperature program, wherein the first constant temperature stage is to maintain 10℃ for 10 minutes, the temperature change stage is to drop to -15℃ at a rate of 0.5℃ / min, and the second constant temperature stage is to maintain -15℃ for 60 minutes.

[0050] 4. Set XRD scanning parameters (you can choose to scan automatically every 5 minutes or every 1°C change).

[0051] 5. Start the experiment, record the temperature and humidity curves simultaneously, and trigger the XRD instrument to scan at the preset point to generate XRD diffraction patterns.

[0052] 6. After the experiment, XRD analysis software was used to perform phase retrieval and quantitative calculation on the obtained series of spectra.

[0053] It is understood that the XRD analysis software in step 6 above can be MDIJade or JADE 6.5, and this embodiment does not make any specific limitation.

[0054] Furthermore, in the above embodiments, it can be observed that as the temperature decreases, the characteristic peak of Na2SO4 gradually weakens, while the characteristic peak of Na2SO4·10H2O (sodium sulfate) gradually strengthens. Combined with synchronous temperature and humidity data (such as humidity changing drastically at a specific temperature point), a quantitative relationship model of temperature-humidity-salt crystallization and a quantitative relationship model of temperature-humidity-dissolved phase of Na2SO4 can be constructed to achieve a quantitative description of water-salt phase transition.

[0055] For ease of explanation, spatial relative terms such as “up,” “down,” “left,” and “right” are used in the embodiments to describe the relationship of one element or feature shown in the figures relative to another element or feature. It should be understood that, in addition to the orientations shown in the figures, spatial terms are intended to include different orientations of the device in use or operation. For example, if the device in the figures is inverted, an element described as being “down” of other elements or features would be positioned “up” of those other elements or features. Therefore, the exemplary term “down” can encompass both up and down orientations. The device may be positioned in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0056] Moreover, relational terms such as “first” and “second” are used merely to distinguish one component from another that has the same name, without necessarily requiring or implying any such actual relationship or order between the components.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A quantitative analysis method for the water-salt phase transition in saline soil, characterized in that, Includes the following steps: S1. Prepare a saline soil sample and place it in a sample cup to detect the temperature and humidity of the saline soil sample; S2. Cover the outside of the sample cup with an isolation cover and allow the X-rays to pass through the isolation cover and the saline soil sample in sequence; S3. Set the target temperature of the sample cup, and collect the temperature data and humidity data of the saline soil sample, as well as the XRD diffraction pattern, during the temperature change or constant temperature process. S4. Based on the temperature data, humidity data and XRD diffraction patterns of the saline soil samples, establish quantitative relationship models of temperature-humidity-salt crystallization and temperature-humidity-dissolved phases of the saline soil samples. The dissolved phase of saline soil samples includes crystal type, crystallization rate, and amount of crystallization at different temperatures.

2. The quantitative analysis method for water-salt phase transition in saline soil according to claim 1, characterized in that, Step S3 also includes: The scanning parameters of the X-ray diffractometer were set, and the saline soil sample was scanned by the X-ray diffractometer to generate an XRD diffraction pattern.

3. The quantitative analysis method for water-salt phase transition in saline soil according to claim 2, characterized in that, The scanning parameters include the first unit interval, and the X-ray diffractometer scans the saline soil sample in the sample cup every time the first unit interval changes.

4. The quantitative analysis method for water-salt phase transition in saline soil according to any one of claims 1-3, characterized in that, In step S3, the target temperature of the sample cup includes a first isothermal stage, a variable temperature stage, and a second isothermal stage. After the first isothermal stage, it enters the variable temperature stage and finally enters the second isothermal stage.

5. The quantitative analysis method for water-salt phase transition in saline soil according to claim 4, characterized in that, The temperature in the first isothermal stage is higher than the temperature in the second isothermal stage, and the duration of the first isothermal stage is shorter than the duration of the second isothermal stage.

6. The quantitative analysis method for water-salt phase transition in saline soil according to any one of claims 4 or 5, characterized in that, The temperature of the first isothermal stage is set to 8°C to 12°C, and the duration is set to 5 min to 15 min. The temperature change rate during the temperature change phase was set to 0.2℃ / min to 0.8℃ / min, and the duration was set to 40min to 60min. The temperature for the second isothermal stage is set to -10℃ to -20℃, and the duration is set to 50min to 70min.

7. The quantitative analysis method for water-salt phase transition in saline soil according to claim 5, characterized in that, During the temperature-changing phase, the temperature inside the sample cup is changed at a constant rate. The duration of the temperature-changing phase is between the duration of the first isothermal phase and the duration of the second isothermal phase.

8. A quantitative analysis device for the water-salt phase transition in saline soil, characterized in that, include: X-ray diffractometer, used to scan saline soil samples to generate XRD diffraction patterns; The sample base has a sample cup on it, and a saline soil sample is placed inside the sample cup. The side wall of the sample cup has an insertion hole, through which the first sensor can enter the sample cup and come into contact with the saline soil sample. The sample base has a temperature control component that can adjust the temperature of the saline soil sample. An isolation cover is used to cover the saline soil sample on the sample base.

9. The quantitative analysis device for water-salt phase transition in saline soil according to claim 8, characterized in that, The top of the isolation shield is provided with a first window for X-ray incidence and a second window for X-ray diffraction.

10. The quantitative analysis device for water-salt phase transition in saline soil according to claim 8, characterized in that, The inner wall of the isolation enclosure is coated with an anti-condensation coating.

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