A method for identifying the critical state of supercooling jump of saline soil based on crystallization kinetics

Abstract

The application relates to a salted soil supercooling jump critical state discrimination method based on crystallization kinetics, which comprises the following steps: performing a soil pore diameter analysis test to obtain a pore diameter distribution curve of a test soil sample; performing a soil salt analysis test to obtain a soil salt type and a salt content; obtaining a limit nucleation rate of the soil sample frozen supercooling jump through the calculation method of the application to discriminate the supercooling jump critical state. The application starts from the occurrence environment of the soil pore solution, fully considers the influence of crystal nucleus generation, solution cooling, ice-water interface and soil-water interface on the system free energy, introduces a classical nucleation theory to deduce and establish a soil pore solution nucleation model, firstly determines the thermodynamic critical condition of the soil supercooling jump, and finally obtains a theoretical model of the limit nucleation rate of the salted soil taking the soil salt type, the salt content and the pore diameter distribution characteristics as the independent variables.

Description

Technical Field

[0001] This invention relates to the field of frozen soil engineering technology, and in particular to a method for defining supercooled vibration of saline soil based on crystallization kinetics. Background Technology

[0002] Unfrozen water refers to soil moisture that remains in liquid form in frozen soil at sub-zero temperatures. It is a key factor determining the mechanical, permeability, and heat transfer properties of frozen soil. Saline soils and frozen soil regions are widely distributed globally and in my country, and many national strategic engineering projects pass through these areas. Under normal freezing conditions, changes in unfrozen water will produce soil effects such as frost heave and thaw settlement, and water and salt transport. The resulting uneven settlement, nutrient loss, and other engineering and agricultural problems will seriously affect and even endanger national strategic security and the well-being of residents. Therefore, research related to unfrozen water is often designated as a key topic for agriculture and engineering construction in cold regions. Many scholars have dedicated themselves to establishing Freezing Characteristic Curve (SFCC) models to study the water, heat, and mechanical properties of soil, as well as the characteristics of water and salt transport and dispersion. However, current models do not adequately consider the supercooling effect of soil pore water in the early stages of freezing. Experimental studies indicate that for soils with higher salt content and smaller average pore size, the error between the SFCC model established by ignoring the supercooling effect and actual experiments is greater. Therefore, in-depth research into the supercooling mechanism of soil pore water crystallization under normal freezing conditions and exploring the supercooling characteristics of unfrozen water will help to further establish a high-precision SFCC model, and also lay a more complete theoretical foundation for numerical calculations. Thus, the above research is of great significance for guiding engineering construction in cold regions and strengthening ecological environment governance. Among these, clarifying the critical conditions for supercooling shock is one of the core issues in studying the supercooling mechanism of soil pore water crystallization under normal freezing conditions. Essentially, the existence of unfrozen water (supercooled soil water) stems from the supercooling effect produced by the combined effects of external pressure, the electrolyte action of the pore solution, soil-water interfacial tension, water-air interfacial tension, and soil particle adsorption. Studying the volume change of unfrozen water based on thermodynamic energy conservation cannot provide a deep understanding of the supercooling mechanism of soil pore water crystallization. Over the years, the development and application of nucleation theory and crystallization kinetics in atmospheric, materials, and food fields have provided a new perspective for revealing the supercooling mechanism of soil pore water crystallization and its critical state. Summary of the Invention

[0003] The technical problem this invention aims to solve is to provide an analytical method for the critical state of supercooling shock in normally frozen soil, considering soil properties such as pore size and salinity. Starting from the occurrence environment of the soil pore solution, this invention fully considers the influence of nucleation, solution cooling, ice-water interface, and soil-water interface on the system's free energy. It introduces classical nucleation theory to derive a soil pore solution nucleation model, and for the first time determines the thermodynamic critical conditions for soil supercooling shock. Finally, it obtains a theoretical model for the boundary nucleation rate of saline soil, with soil salt type, salt content, and pore size distribution characteristics as independent variables. This invention fully considers soil properties such as pore size and salinity, with clear influencing factors and explicit physical meaning. It can be used to analyze and calculate the critical conditions for supercooling shock in any conventional saline and non-saline soil, contributing to the further development of a high-precision SFCC model applicable to both saline and non-saline soils. It also provides a more comprehensive theoretical basis for related numerical calculations of water and salt transport.

[0004] The critical state analysis method for supercooled shock of saline soil based on crystallization kinetics described in this invention includes the following steps:

[0005] (1) Conduct soil pore size analysis tests to obtain the pore size distribution curve of the test soil sample.

[0006] (2) Chemical analysis of soil salinity was performed to obtain the soil salinity type and content.

[0007] (3) The limit nucleation rate of the supercooling shock of the soil sample is obtained by the calculation method of the present invention, and the critical state of supercooling shock is determined.

[0008] The function of the change in free energy of the system during the freezing and nucleation process is ΔG. k Divided into the change of solution free energy ΔG sln Free energy change ΔG caused by crystal nucleation V Surface tension free energy of crystal nuclei ΔG S The free energy variable ΔG of the interfacial tension between soil and water l-s Four parts:

[0009] ΔG k =AG sln +ΔG V +AG S +AC l-s (I)

[0010] To further determine the system's free energy variables during the phase transition process, two boundary states are defined. State a refers to the initial state (no ice-water phase transition) with an instantaneous temperature of T0. At this point, the solution consists of water molecules and solute molecules, with the following molecular numbers: n w With n y The chemical potentials are μ w，1 With μ y，1State b refers to the critical nucleation state, with an instantaneous temperature of T. sc At this point, the pores contain crystal nucleus molecules, water molecules, and solute molecules, and the number of molecules can be expressed as: n germ 、(n w -n germ ) and n y Chemical potential is expressed as μ i μ w，1 With μ y，1 .

[0011] Therefore, the change in solution free energy ΔG during nucleation in equation (1) sln It can be calculated using the following formula:

[0012] ΔG sln =n w (μ w，1 -μ w，0 )+n y (μ y，1 -μ y，0 (2)

[0013] The crystallization process causes changes in the molar composition of the liquid phase and a loss of entropy in the system, so equation (2) can be expressed as:

[0014]

[0015] In equation (3), n germ This represents the total number of crystal nuclei. Considering that the critical nucleation radius is much smaller than the pore size, and the changes in temperature and pore solution concentration are minimal, the solution activity can be approximated as unchanged before and after crystallization. That is, a w ≈a w，0 a y ≈a y，0 Therefore, equation (3) can be further simplified to:

[0016]

[0017] In equation (4), v i The average lattice volume occupied by ice molecules can be calculated using the Zobrist equation:

[0018]

[0019] In equation (5), N a Refers to Avogadro's constant, ρ i0 The density of ice at zero degrees Celsius can be represented by ρ. i0 =0.9167g / cm 3 In addition, relative temperature (T0 is 0 degrees Celsius, T is the actual temperature).

[0020] Similarly, the change in free energy ΔG caused by nucleus formation during nucleation... V It can be represented as:

[0021]

[0022] In equation (6), S li This represents the steady-state vapor pressure ratio of the solution and ice crystals under the same temperature and pressure. For the solution-ice crystal system, applying Raoult's law to the porous solution (a non-ideal dilute solution) yields:

[0023]

[0024] In the formula, S i The steady vapor pressure ratio of water and ice crystals under the same temperature and pressure can be calculated using the following formula:

[0025] lnS i ≈(-210368-131.438T+3.32373×10 6 / T+41729.1lnT) / (RT) (8)

[0027] In addition, the surface tension free energy ΔG of the crystal nucleus S The free energy variable ΔG of the interfacial tension between soil and water l-s They can be represented as:

[0028]

[0029] ΔG l-s =[σ l-s (T)-σ l-s (T0)]·S sum (10)

[0030] From equations (2)-(10), the final expression for the change in the system's free energy during nucleation can be obtained:

[0031]

[0032] Combining critical nucleation conditions System critical nucleation radius r * With critical nucleation work ΔG * It can be represented as:

[0033]

[0034]

[0035] Using the classical nucleation theory framework, the expression for the critical nucleation rate can be obtained as follows:

[0036]

[0037] Among them, Planck's constant h≈6.62607×10 -34 J·s, Boltzmann constant k B ≈1.380649×10 -23 J / K, T sc The critical nucleation temperature; N1 represents the number density of liquid water molecules, which can be taken as N1 = 3.33 × 10⁻⁶. 28 m -3 ;n T This represents the number of molecules in contact per unit surface area of ​​the crystal nucleus, which can be taken as n. T =10 19 m -2 ;σ iw The interfacial tension between ice and water can be calculated using the following formula:

[0038] σ iw [J·m -2 ] = 28 × 10 3 +T c ×0.25×10 -3 (15)

[0039] The thermodynamic critical condition for preventing supercooling shock is: T sc =T f At this point, the critical nucleation rate of the system is equal to the threshold nucleation rate at which supercooling jumps occur. Its physical meaning is the minimum nucleation rate theoretically required for supercooling jumps to occur. This cleverly avoids multivariate coupling and quantitatively finds the theoretically non-supercooling jump critical state. That is:

[0040]

[0041] Where T f The equilibrium freezing temperature can be calculated using the following formula:

[0042]

[0043] In the formula, r is the pore radius; γ il To represent the ice-water interfacial energy, we can take γ. il =0.0409 + 3.9 × 10 -4 T; θ is the soil-water contact angle; for saturated soil, θ ≡ 180°; ΔS m This is the entropy difference between ice and water; for simplicity of calculation, ΔS can be used. m =1.2MPa / K; V i * It is the molar volume of the ice crystal, assuming the density of ice is fixed at 0.917 g / cm³. 3 At that time, V i *=19.63cm 3 / mol. Furthermore, a w Water activity refers to the water activity, which can be calculated using the Pizter ion model.

[0044] When the pore solution volume is V w At this point, the limiting heat release power P can be further determined. L * :

[0045]

[0046] In the formula Δh f (T f () represents the latent heat of phase transition released when each water molecule transforms into ice.

[0047]

[0048] Based on the freezing process analysis above, when the effective power P of the system absorbs cold energy... L The heat release power P below this limit L * When this condition is met, no significant temperature-time curve jumps will occur. This limit condition can be expressed by formula (20):

[0049]

[0050] This invention, based on the microstructure of soil pore solution crystallization and combined with classical nucleation theory, derives the free energy function of the phase transition process of soil pore solution. Based on the critical nucleation condition, it determines the critical nucleation work and critical nucleation energy of soil pore solution. Furthermore, when the equilibrium freezing temperature equals the spontaneous nucleation temperature, it determines the boundary nucleation rate and boundary exothermic power of soil pore solution. The soil sample physical parameters required for this invention include pore size distribution curves, soil salt types and salt content. All objective influencing factors are comprehensively considered, and their physical meaning is clear, resulting in a theoretical formula for the critical condition of supercooling shock in soil pore solution. This invention can be used to clarify the critical state and nucleation microstructure of supercooling shock in soil solution, and provides theoretical reserves for improving the freezing characteristic curve model and studying the freeze-thaw hysteresis effect.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] 1. This invention starts from the occurrence environment of soil pore solution, fully considering the influence of crystal nucleation, solution cooling, ice-water interface, and soil-water interface on the system's free energy. It introduces classical nucleation theory to derive and establish a soil pore solution nucleation model, and for the first time determines the thermodynamic critical conditions for soil supercooling shock. This invention ultimately yields a theoretical model of the boundary nucleation rate of saline soil, with soil salt type, salt content, and pore size distribution as independent variables.

[0053] 2. This invention can be used to analyze and calculate the critical conditions of supercooling shock in any conventional saline and non-saline soils, fully considering soil properties such as pore size and salinity, with clear influencing factors and explicit physical meaning. Attached Figure Description

[0054] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0055] Figure 1 This is a microscopic schematic diagram of the nucleation process in soil pore solution.

[0056] Figure 2 This is a graph showing the freezing process and its characteristic temperatures.

[0057] Figure 3 This is a diagram showing the pore size distribution of the test soil sample.

[0058] Figure 4 This is a temperature monitoring graph for the freezing process of the test soil sample.

[0059] Figure 5 The diagram shows the boundary nucleation rate and boundary exothermic power of the soil sample.

[0060] Detailed Implementation Instructions

[0061] A method for defining the supercooled shock of saline soil based on crystallization kinetics includes the following steps:

[0062] (1) Conduct soil pore size analysis tests to obtain the pore size distribution curve of the test soil sample.

[0063] (2) Chemical analysis of soil salinity was performed to obtain the soil salinity type and content.

[0064] (3) The limit nucleation rate of the supercooling shock of the soil sample is obtained by the calculation method of the present invention, and the critical state of supercooling shock is determined.

[0065] Figure 1 This is a model diagram of soil pore solution freezing and nucleation, where the system's free energy change function ΔG k This can be further subdivided into the change in solution free energy ΔG sln Free energy change ΔG caused by crystal nucleation V Surface tension free energy of crystal nuclei ΔG S The free energy variable ΔG of the interfacial tension between soil and water l-s Four parts:

[0066] ΔG k =ΔG sln +ΔG V +ΔG S +ΔG l-s (1)

[0067] To further determine the system's free energy variable during the phase transition process, two boundary states are defined: State a refers to the initial state (no ice-water phase transition) with an instantaneous temperature of T0. At this point, the solution consists of water molecules and solute molecules, with the following molecular numbers: n w With n y The chemical potentials are μ w，1 With μ y，1 State b refers to the critical nucleation state, with an instantaneous temperature of T. sc At this point, the pores contain crystal nucleus molecules, water molecules, and solute molecules, and the number of molecules can be expressed as: n germ 、(n w -n germ ) and n y Chemical potential is expressed as μ i μ w，1 With μ y，1 .

[0068] Therefore, the change in solution free energy ΔG during nucleation in equation (1) sln It can be calculated using the following formula:

[0069] ΔG sln =n w (μ w，1 -μ w，0 )+n y (μ y，1 -μ y，0 (2)

[0070] The crystallization process causes changes in the molar composition of the liquid phase and a loss of entropy in the system, so equation (2) can be expressed as:

[0071]

[0072] In equation (3), n germ This represents the total number of crystal nuclei. Figure 1 The diagram highlights the ice crystal nucleation process and microstructure, but the actual critical nucleation radius is often much smaller than the pore size. Furthermore, the changes in temperature and pore solution concentration during nucleation are relatively small; therefore, the solution activity can be approximated as unchanged before and after crystallization in calculations. That is, a w ≈a w，0 a y ≈a y，0 Therefore, equation (3) can be further simplified to:

[0073]

[0074] In equation (4), v i The average lattice volume occupied by ice molecules can be calculated using the Zobrist equation:

[0075]

[0076] In equation (5), N a Refers to Avogadro's constant, ρ i0 The density of ice at zero degrees Celsius can be represented by ρ. i0 =0.9167g / cm 3 In addition, relative temperature (T0 is 0 degrees Celsius, T is the actual temperature).

[0077] Similarly, the change in free energy ΔG caused by nucleus formation during nucleation... V It can be represented as:

[0078]

[0079] In equation (6), S li This represents the steady-state vapor pressure ratio of the solution and ice crystals under the same temperature and pressure. For the solution-ice crystal system, applying Raoult's law to the porous solution (a non-ideal dilute solution) yields:

[0080]

[0081] In the formula, S i The steady vapor pressure ratio of water and ice crystals under the same temperature and pressure can be calculated using the following formula:

[0082] lnS i ≈(-210368-131.438T+3.32373×10 6 / T+41729.1lnT) / (RT) (8)

[0084] In addition, the surface tension free energy ΔG of the crystal nucleus S The free energy variable ΔG of the interfacial tension between soil and water l-s They can be represented as:

[0085]

[0086] ΔG l-s =[σ l-s (T)-σ l-s (T0)]·S sum (10)

[0087] From equations (2)-(10), the final expression for the change in the system's free energy during nucleation can be obtained:

[0088]

[0089] Combining critical nucleation conditions System critical nucleation radius r *With critical nucleation work ΔG * It can be represented as:

[0090]

[0091]

[0092] Using the classical nucleation theory framework, the expression for the critical nucleation rate can be obtained as follows:

[0093]

[0094] Among them, Planck's constant h≈6.62607×10 -34 J·s, Boltzmann constant k B ≈1.380649×10 -23 J / K, T sc The critical nucleation temperature; N1 represents the number density of liquid water molecules, which can be taken as N1 = 3.33 × 10⁻⁶. 28 m -3 ;n T This represents the number of molecules in contact per unit surface area of ​​the crystal nucleus, which can be taken as n. T =10 19 m -2 ;σ iw The interfacial tension between ice and water can be calculated using the following formula:

[0095] σ iw [J·m -2 ] = 28 × 10 3 +T c ×0.25×10 -3 (15)

[0096] like Figure 2 As shown, the thermodynamic critical condition for the equilibrium freezing temperature and critical nucleation temperature to avoid supercooling jumps is: T sc =T f In this critical state, the critical nucleation rate of the system is equal to the threshold nucleation rate at which supercooling jumps occur. This "threshold nucleation rate" is the minimum nucleation rate theoretically required for supercooling jumps to occur. This cleverly avoids multivariate coupling and quantitatively identifies the theoretically non-supercooling jump critical state. That is:

[0097]

[0098] Among them, the equilibrium freezing temperature T f It can be calculated using the following formula:

[0099]

[0100] In the formula, r is the pore radius, which can be obtained by selecting a representative value from the pore size distribution of the soil sample; γil To represent the ice-water interfacial energy, we can take γ. il =0.0409 + 3.9 × 10 -4 T; θ is the soil-water contact angle; for saturated soil, θ = 180°; ΔS m This is the entropy difference between ice and water; for simplicity of calculation, ΔS can be used. m =1.2MPa / K; V i * It is the molar volume of the ice crystal, assuming the density of ice is fixed at 0.917 g / cm³. 3 At that time, V i * =19.63cm 3 / mol. Furthermore, a w Water activity refers to the same as in equation (14), which can be calculated based on the Pizter ion model according to the actual analysis results of the salt types and salt content of the saline soil sample.

[0101] When the pore solution volume is V w At this point, the limiting heat release power P can be further determined. L * :

[0102]

[0103] In the formula Δh f (T f () represents the latent heat of phase transition released when each water molecule transforms into ice.

[0104]

[0105] Based on the freezing process analysis above, when the effective power P of the system absorbs cold energy... L The heat release power P below this limit L * When this condition is met, no significant temperature-time curve jumps will occur. This limit condition can be expressed by formula (20):

[0106]

[0107] Example 1

[0108] The soil used in the test for this invention patent was taken from Delingha, China (37°22'N, 97°21'E). Saline soils are widely distributed in these areas. The pore size distribution of the soil sample can be obtained by mercury intrusion porosimetry as follows: Figure 3As shown. The test scheme was designed based on the actual water and salinity of the field site, with salinity (the ratio of NaCl salt crystals to dry soil mass) set at 0%, 0.4%, and 0.8%, respectively. The initial water content was 12%. During sample preparation, a specified amount of solute was mixed with deionized water to obtain the required water and salinity. To ensure a more uniform distribution of salt ions and water in the sample, the sample was placed in a plastic bag, stored in a constant temperature chamber, and kept at 20℃ for 24 hours. Before the freeze-thaw cycle test, the uniformly mixed soil sample was packed into a specially made iron box with a diameter of 3.3 cm and a height of 3.8 cm and sealed. The sample was then compacted in layers to obtain a soil sample with uniform density. The filling height of the soil sample was 3.8 cm, and the dry density was controlled at 1.86–1.90 g / cm³. 3 .

[0109] By conducting freeze-thaw cycles on three groups of soil samples with salt contents of 0%, 0.4%, and 0.8% according to the experimental protocol, their temperature monitoring curves can be obtained as follows: Figure 4 As shown in the figure, by comparing the three curves, it was found that during the freezing stage, the temperature at which the supercooling bounce occurs decreases with increasing concentration, and the amplitude of the supercooling bounce gradually weakens with increasing concentration until no obvious supercooling bounce occurs. During the thawing stage, the average thawing temperature decreases with increasing ion concentration. More water molecules prematurely transform from ice to supercooled water at sub-zero temperatures, resulting in relatively less pore water completing the phase transition near the ideal thawing temperature. This leads to the phenomenon in the soil temperature monitoring curve where "the thawing plateau of the temperature curve continuously weakens with increasing pore concentration."

[0110] Through aperture Figure 3 It is known that over 90% of the mass percentage of particles in the soil sample has a diameter between 1 and 100 micrometers, and the average pore size is approximately 10 micrometers. Therefore, it is estimated that the equivalent radius of most pores within the experimental soil sample is between 100 and 1 micrometer. In conclusion, this paper argues that using 10 micrometers as the simulated pore radius has good theoretical representativeness. The nucleation rate diagram of the 10-micrometer saturated pore boundary obtained based on the framework of this paper (e.g.) Figure 5 (As shown).

[0111] With P L * The higher the salt content, the more difficult it is theoretically for supercooling to occur. On the one hand, Figure (5) shows that the higher the salt content, the more difficult it is for supercooling to occur. When the salt content is zero, the threshold nucleation rate also tends to zero. Subsequently, It will increase rapidly with increasing concentration. When the salt content is 0.4%, Jump to 10 32 m -3 s -1 But PL * Still below 0.1W. When the salt content is 0.8%, Reached 10 36 m -3 s -1 P L * Since the pore size is already greater than 100 W, supercooling shock is extremely difficult to occur. On the other hand, under the same salinity conditions, a smaller pore radius also makes supercooling shock less likely. Therefore, pores with r < 10 μm under the same salinity conditions... Relatively higher, with pore sizes r>10μm under the same salinity conditions The temperature is relatively lower. In the experiment, the temperature monitoring curve measured by the equipment is for all pores in the soil sample. With the increase of salt concentration, the supercooling jump phenomenon in small pores disappears earlier than in large pores. In other words, under the same experimental conditions, the number of pores capable of supercooling jump decreases with increasing salt concentration. Therefore, in the measured curve, the amplitude of supercooling jump will decrease with increasing salt concentration until no obvious supercooling jump occurs. In summary, the measured curves of freezing tests on three sets of soil samples with different salt contents can well demonstrate the effectiveness of this invention in defining the critical state of supercooling jump in saline soil.

Claims

1. A method for determining the critical state of supercooled shock in saline soil based on crystallization kinetics, characterized in that, The following steps are required: (1) Conduct soil pore size analysis tests to obtain the pore size distribution curve of the test soil sample; (2) Chemical analysis of soil salinity was performed to obtain the types and amounts of soil salinity; (3) The critical nucleation rate of the supercooling shock of the soil sample was obtained by calculation, and the critical state of supercooling shock was determined. By analyzing the nucleation process in the initial stage of freezing of soil pore solution, the change in free energy of the system during the freezing nucleation process is expressed as a function. Divided into changes in solution free energy Free energy variable caused by crystal nucleation Nucleus surface tension free energy Interfacial tension free energy variable between soil and water Four parts: (1) To further determine the system's free energy variables during the phase transition process, two boundary states are defined, where state a refers to the initial state and the instantaneous temperature is... At this point, the solution consists of water molecules and solute molecules, with the following molecular numbers: Chemical potentials are respectively with State b refers to the critical nucleation state, with an instantaneous temperature of At this point, the pores contain ice crystal molecules, water molecules, and solute molecules, with the number of molecules represented as follows: Chemical potentials are expressed as follows: ; Therefore, the change in solution free energy during the nucleation stage Calculated using the following formula: （2） The crystallization process causes changes in the molar composition of the liquid phase and a loss of entropy in the system, so equation (2) can also be expressed as: (3) In formula (3) This represents the total number of crystal nuclei. Considering that the critical nucleation radius is much smaller than the pore size, and that the changes in temperature and pore solution concentration are minimal, the solution activity is assumed to remain unchanged before and after crystallization in the calculation. Therefore, equation (3) can be further simplified to: （4） In equation (4), The average lattice volume occupied by ice molecules is calculated using the Zobrist equation: In equation (5), Refers to Avogadro's constant. The density of ice at zero degrees Celsius. In addition, relative temperature , 0℃, T is the actual temperature. Similarly, the change in free energy caused by nucleus formation during nucleation. Represented as: In equation (6), This represents the stable vapor pressure ratio of the solution and ice crystals under the same temperature and pressure. For the solution-ice crystal system, applying Raoult's law to the pore solution yields: In the formula, The steady-state vapor pressure ratio of water and ice crystals under the same temperature and pressure is calculated using the following formula: In addition, the surface tension free energy of the crystal nucleus Interfacial tension free energy variable between soil and water They are represented as follows: From (2)-(10), we obtain the final expression for the change in the system's free energy during nucleation: Combining critical nucleation conditions Critical nucleation radius of the system With critical nucleation work Represented as: The expression for the critical nucleation rate, derived from the classical nucleation theory framework, is as follows: Among them, Planck's constant Boltzmann constant , It is the critical nucleation temperature; Represents the number density of liquid water molecules, taken as . ; The number of molecules in contact per unit surface area of ​​the crystal nucleus is taken as . ; The interfacial tension between ice and water is calculated using the following formula: The thermodynamic critical condition for preventing supercooling shock is: At this point, the critical nucleation rate of the system is equal to the threshold nucleation rate at which supercooling jump occurs. This is the minimum nucleation rate theoretically required for the supercooling jump phenomenon to occur. By avoiding multivariate coupling, the critical state at which supercooling jump theoretically does not occur can be quantitatively found, i.e. In the formula, r is the pore radius; This represents the ice-water interfacial energy, taken as... ; It is soil-water contact, for saturated soil. ; This is the entropy difference between ice and water, which is used for calculation simplicity. =1.2MPa / K; It is the molar volume of the ice crystal, assuming the density of ice is constant. hour, ,also, Water activity refers to the same as in equation (14), calculated using the Pizter ion model; When the pore solution volume is At that time, to further determine the limit of heat release power : In the formula This represents the latent heat of phase transition released when each water molecule transforms into ice. Based on the freezing process analysis above, when the system absorbs the effective power of cold energy... Heat release power below this limit When this condition is met, no significant temperature-time curve jumps will occur. This limit condition is expressed by formula (20): 。 2. The method for determining the critical state of supercooled shock in saline soil based on crystallization kinetics according to claim 1, characterized in that: By using a microscopic model of nucleation and crystallization in the early stage of freezing of soil pore solution, the Gibbs free energy function of the system in this process is obtained, the spontaneous nucleation rate expression is obtained, and the nucleation rate of the discrimination index is obtained under the temperature condition of the supercooled shock critical state.

3. The method for determining the critical state of supercooled shock in saline soil based on crystallization kinetics according to claim 1, characterized in that: The initial state of state a is a state without ice-water phase transition.

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