Water-heat-force quantitative analysis method for regulating and controlling freezing and thawing cycle process of soil body by wicking geotextile

Abstract

The invention belongs to the technical field of quantitative analysis of special soil, and provides a water-heat-force quantitative analysis method for regulating and controlling the freeze-thaw cycle process of a soil body by a wicking geotextile, and the method comprises the following specific steps: carrying out a triaxial shear test of the soil under the freeze-thaw cycle condition to obtain a soil body cohesive force degradation equation under the water-heat condition; the control equations of the temperature field and the water field are converted into theoretical equations with saturation S as an independent variable, and two-field coupling is achieved; establishing a coupling relationship between the wicking geotextile and the moisture field; and writing calculation methods of the stress field, the temperature field, the moisture field and the wicking geotextile into numerical simulation software for full coupling. According to the method, indoor tests are combined with calculation theory derivation and establishment, the regulation and control effect of the wicking geotextile on the roadbed water content is effectively simulated, the optimal laying position and laying method of the wicking geotextile in the roadbed drainage regulation and control process are determined, the roadbed water content regulation and control efficiency of the wicking geotextile is improved, and the construction cost is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of special soil quantitative analysis, and relates to a water-heat-force quantitative analysis method for regulating water-heat-force in a freezing-thawing cycle process of soil by wicking geotextile. BACKGROUND

[0002] Under the background of global warming, the unstable permafrost range of seasonal freezing and thawing in permafrost regions increases year by year. The strong capillary action and temperature gradient drive the water migration and accumulation in the roadbed, which leads to the phenomena of melting settlement, mud boiling, local instability and collapse in high-cold regions, resulting in the service life of roads of all grades being far lower than the design life, and the annual maintenance cost being huge. One of the effective measures for preventing and controlling roadbed frost damage is to prevent water from flowing to the freezing front. However, due to the influence of the excess pore water pressure of the soil body, the existing drainage design method is mainly used for processing gravity water and cannot effectively drain the capillary water from the roadbed structure.

[0003] At present, in the field of frozen soil, the method of coupling of water field, stress field and temperature field is usually used to study the related problems in the field. However, since the wicking geotextile is a humidity control material, there is a fundamental difference between the wicking geotextile and the soil, which makes the current water migration theory of the wicking geotextile not yet completely constructed, resulting in no water-heat-force calculation method based on the wicking geotextile regulating the water content of the soil body. Therefore, in the engineering application, it is difficult to find the best laying position and laying method of the wicking geotextile in the roadbed, and it is difficult to effectively characterize the regulation effect of the wicking geotextile on the frost heaving and thawing settlement of the soil body, which is easy to cause the waste of resources. SUMMARY

[0004] The application provides a water-heat-force quantitative analysis method for regulating a freezing-thawing cycle process of a soil body by wicking geotextile, which characterizes the regulation effect of the wicking geotextile on the frost heaving and thawing settlement of the soil body from the quantitative point of view, and reveals the action mechanism of the wicking geotextile on the water migration, temperature regulation and settlement evolution of the soil body, thereby providing theoretical and technical support for the prevention and control of the frost damage of the high-cold roadbed in the frozen soil region and the long-term service performance maintenance.

[0005] In order to achieve the above purpose, the technical scheme adopted by the application is as follows.

[0006] S1, triaxial shear tests of the soil body under the freezing-thawing cycle condition are carried out for the engineering region, the saturation, the freezing-thawing cycle number and the freezing temperature are taken as the independent variables, and the soil body cohesion degradation equation under the water-heat condition is obtained through polynomial fitting;

[0007] S2. Based on the theoretical expressions of unfrozen water content and initial moisture content, the temperature field control equation and the moisture field control equation are transformed into theoretical equations with saturation S as the independent variable, thereby realizing the coupling of the temperature field and the moisture field.

[0008] S3. Conduct indoor wicking geotextile-soil column tests to establish the relationship between soil saturation and the water conductivity of wicking geotextile, determine the boundary conditions for the moisture control effect of wicking geotextile, and establish the coupling relationship between wicking geotextile and water field.

[0009] S4. The calculation methods of stress field, temperature field, moisture field and wicking geotextile in S1, S2 and S3 are written into COMSOL Multiphysics software and fully coupled to realize the quantitative analysis of the regulatory effect of wicking geotextile on subgrade deformation, temperature and humidity under different conditions.

[0010] Preferably, S1 specifically includes the following steps:

[0011] S11. Prepare triaxial test soil samples. Based on the environmental conditions and basic parameters of the actual project, determine the soil saturation, freezing temperature and number of freeze-thaw cycles. Conduct consolidated undrained triaxial tests to obtain the stress-strain relationship and strength parameter variation law of the soil under different conditions.

[0012] S12. Based on the obtained stress-strain relationship, according to the Mohr-Coulomb strength theory, the relationships between cohesion-saturation, cohesion-cycle number, and cohesion-freezing temperature are established respectively, and the influence characteristics and trends of each factor on cohesion are obtained.

[0013] S13. By using the decision tree model in the supervised machine learning algorithm, analyze the influence weights of different saturation, number of cycles, and freezing temperature on cohesion, and obtain the most significant factors affecting soil cohesion.

[0014] S14. The cohesion degradation equation obtained through polynomial coupling is c=y(S, T, n), where S is the degree of saturation, T is the temperature, and n is the number of cycles.

[0015] Preferably, S2 specifically includes the following steps:

[0016] S21. The theoretical expression for the relationship between unfrozen water content and initial moisture content is: In the formula, T is the temperature, ω0 is the water content of the unfrozen water at the freezing temperature T, and ω u Let T be the initial mass moisture content of the soil, B be an empirical coefficient related to the solid-liquid ratio, and T be the initial mass moisture content of the soil. f The freezing temperature of the soil;

[0017] S22. The temperature field governing equation is transformed into an equation with saturation S as the independent variable: In the formula, C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio;

[0018] S23. The governing equation for the moisture field is transformed into an equation with saturation S as the independent variable: , In the formula, q represents the flow rate. For the matric suction of the soil, k(h) m ) is the permeability coefficient function, h is the matrix suction head, and α is a parameter related to the air intake value in the geotechnical engineering VG model.

[0019] As a preferred option, S3 specifically includes the following steps:

[0020] S31. Before the test, the basic properties of the soil were measured;

[0021] S32. Prepare test specimens. Prepare three parallel standard specimens for each moisture content sample. To obtain the initial state of the soil column, set up a test specimen for each moisture content sample. Place all test specimens in a curing chamber at 20℃ and 30% humidity. Place all test specimens on a mass sensor with an accuracy of 0.1g and monitor the mass change of the test specimens in real time. When the mass of the test specimens decreases to a stable level, the soil column and air humidity reach equilibrium.

[0022] S33. Conduct the experiment. At the same time every day, take out each group of samples from the curing box in sequence, record the mass with an electronic scale, and then quickly put them back into the curing box.

[0023] S34. Based on the changes in the mass of soil columns with different moisture contents over time obtained from monitoring, calculate the daily volumetric moisture content of different soils. In the curve of the change in volumetric moisture content of soil over time, the line connecting the start and end points is regarded as the average drainage rate of the core-absorbing geotextile, and then it is converted into the matrix suction head.

[0024] S35. According to the basic soil property formula, the soil moisture content is converted into saturation. This yields the average water conductivity of the wicking geotextile corresponding to soils with different initial moisture contents. Through nonlinear fitting, the relationship between the soil moisture content and the wicking geotextile water conductivity is obtained, establishing the relationship between soil saturation and the wicking geotextile water conductivity. .

[0025] As a preferred option, the basic properties of the soil in S31 include the liquid limit, plastic limit, optimum moisture content, maximum dry density, mineral composition, saturated moisture content, residual moisture content, and soil-water characteristic curve.

[0026] Preferably, S4 specifically includes the following steps:

[0027] S41. Four-field coupling is achieved through the PDEs custom coefficient type partial differential equation module and solid mechanics module.

[0028] S42. In a solid mechanics field, considering the soil as an elastoplastic model, the formula for frost heave force is: In the formula, E is Young's modulus and μ is Poisson's ratio. In response, In the formula: η(θ) i The frost heave coefficient is affected by the volumetric ice content in the soil. A semi-empirical formula for determining its value is: ;

[0029] S43. Parameter settings for the solid mechanics field: the top boundary is set as a free end, and the other boundaries are fixed constraints, to observe the deformation of the soil at the top during frost heave and thaw settlement; the cohesion is assigned to the soil cohesion degradation equation in S1, and the internal friction angle is taken as the average value of all triaxial shear test results in S1; when embedding the cohesion equation, the saturation S in the cohesion formula is the result of real-time calculation of the moisture field.

[0030] S44. In a moisture field, the moisture field equation is: In the formula: z is the gravitational potential. ρ is the matrix potential, k is the permeability coefficient, and ρ is the matrix potential. i It is the density of ice, ρ ω It is the density of water, θ u This refers to the unfrozen water content; the outer perimeter of the soil column is a zero flux boundary. When simulating continuous water replenishment, the bottom boundary is set as a Dirichlet boundary, and the saturation S is set to a constant value of 0.99. When simulating closed conditions, the bottom boundary is also set as a zero flux boundary.

[0031] S45. In a temperature field, the governing equation of the temperature field is: In the formula: C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio is used. During the construction of the temperature field, a freeze-thaw cycle temperature condition T is applied to the top boundary and the two sides with a length of 2 cm to simulate the effect of the top of the soil column having a certain thickness of upper temperature control plate. The heating and cooling rate is 2℃ / h, and the other boundaries are at a constant temperature of 10℃.

[0032] The governing equation for S46, the wicking geotextile field, is: This equation was obtained through coupling of wicking geotextile and soil column tests.

[0033] S47. In the water-thermal-mechanical coupling calculation process of COMSOL, the volumetric ice content is converted into the frost heave coefficient using the built-in IF function. The deformation coefficient is then input into the expansion coefficient in COMSOL. The transient solver is used to realize the numerical simulation of the frost heave and thawing settlement process of unsaturated frozen soil.

[0034] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0035] This invention provides a quantitative analysis method for the water-thermal-mechanical processes of soil freeze-thaw cycles using wicking geotextiles. This method enables multi-field coupling of wicking geotextiles with water, heat, and mechanical forces in roadbeds in high-altitude permafrost regions. The coupling method is derived using a combination of indoor experiments and computational theory. This invention makes the physical structure of the model more realistic, with high accuracy and fast calculation speed. It can effectively simulate the effect of wicking geotextiles on the moisture content of roadbeds. This invention can determine the optimal laying position and method of wicking geotextiles in regulating roadbed drainage, thereby improving the efficiency of wicking geotextiles in regulating roadbed moisture and reducing project costs. This invention is not only applicable to high-altitude permafrost roadbeds, but also, based on parameter setting and calibration, to other soil roadbeds, making it widely applicable. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 A flowchart of the steps of a water-thermal-mechanical calculation method for regulating soil moisture content changes using wicking geotextiles;

[0038] Figure 2 A theoretical schematic diagram of the wicking geotextile-water-thermal-mechanical multi-field coupling method provided in the embodiment;

[0039] Figure 3 A schematic diagram of the wicking geotextile-soil column test provided for the embodiments;

[0040] Figure 4 A flowchart illustrating the theoretical process of wicking geotextile soil column testing and calculation for an example embodiment;

[0041] Figure 5 The time-history curves showing the maximum frost heave of the MWG roadbed at different locations;

[0042] Figure 6 This is a schematic diagram illustrating the variation of the maximum freezing depth Z.

[0043] Figure 7 This is a schematic diagram illustrating the variation of the total frost heave z.

[0044] Figure 8 This is a schematic diagram illustrating the variation of the average frost heave η. Detailed Implementation

[0045] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" appearing below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0046] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0047] Examples, such as Figures 1-4 As shown, the present invention provides a quantitative water-thermal-mechanical analysis method for regulating the freeze-thaw cycle process of soil using wicking geotextiles, comprising the following specific steps:

[0048] S1. Conduct triaxial shear tests on soil under freeze-thaw cycles. Using saturation, number of freeze-thaw cycles, and freezing temperature as independent variables, obtain the soil cohesion degradation equation under water-thermal conditions through polynomial fitting, and obtain the method for calculating the stress field.

[0049] S2. Based on the theoretical expressions of unfrozen water content and initial moisture content, the temperature field control equation and the moisture field control equation are transformed into theoretical equations with saturation S as the independent variable, thereby realizing the coupling of the temperature field and the moisture field and obtaining the calculation methods of the temperature field and the moisture field.

[0050] S3. Conduct indoor wicking geotextile-soil column tests to establish the relationship between soil saturation and the water conductivity of wicking geotextile, determine the boundary conditions for the moisture control effect of wicking geotextile, establish the coupling relationship between wicking geotextile and water field, and obtain the calculation method for wicking geotextile.

[0051] S4. The calculation methods of stress field, temperature field, moisture field and wicking geotextile in S1, S2 and S3 are written into COMSOL Multiphysics software and fully coupled to realize the quantitative analysis of the regulatory effect of wicking geotextile on subgrade deformation, temperature and humidity under different conditions.

[0052] S1 specifically includes the following steps:

[0053] S11. Prepare triaxial test soil samples. According to the specifications, prepare standard triaxial test soil samples with a diameter of 39.1 mm and a height of 80 mm using the static compaction method. Based on the environmental conditions and basic parameters of the actual project, determine the saturation, freezing temperature and number of freeze-thaw cycles of the soil. Conduct consolidated undrained triaxial tests to obtain the stress-strain relationship and strength parameter variation law of the soil under different conditions.

[0054] S12. Based on the obtained stress-strain relationship, according to the Mohr-Coulomb strength theory, the relationships between cohesion-saturation, cohesion-cycle number, and cohesion-freezing temperature are established respectively, and the influence characteristics and trends of each factor on cohesion are obtained.

[0055] S13. The machine learning algorithm used mainly utilizes the decision tree model in supervised machine learning algorithms to analyze the influence weights of different saturation levels, number of cycles, and freezing temperatures on cohesion, thereby obtaining the most significant factors affecting soil cohesion.

[0056] S14. The cohesion degradation equation obtained through polynomial coupling is c=y(S, T, n), where S is the degree of saturation, T is the temperature, and n is the number of cycles. These three are independent variables.

[0057] S2 specifically includes the following steps:

[0058] S21. The theoretical expression for the relationship between unfrozen water content and initial moisture content is: In the formula, T is the temperature (°C), ω0 is the water content (%) of the unfrozen water at freezing temperature T, and ω u Let T be the initial mass moisture content of the soil (%), B be an empirical coefficient related to the solid-liquid ratio, and T be the initial mass moisture content of the soil (%). f The freezing temperature of the soil (°C);

[0059] S22. The temperature field governing equation is transformed into an equation with saturation S as the independent variable: In the formula, C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio;

[0060] S23. The governing equation for the moisture field is transformed into an equation with saturation S as the independent variable: , In the formula, q represents the flow rate. For the matric suction of the soil, k(h) m ) is the permeability coefficient function, h is the matrix suction head, and α is a parameter related to the air intake value in the geotechnical engineering VG model.

[0061] S3 specifically includes the following steps:

[0062] S31. Before the test, i.e. before conducting the indoor wicking geotextile water migration test, refer to the "Standard for Geotechnical Testing Methods" (GB / T 50123-2019) to measure the basic properties of the soil. The basic properties of the soil include the liquid limit, plastic limit, optimum moisture content, maximum dry density, mineral composition, saturated moisture content, residual moisture content, and soil-water characteristic curves, etc.

[0063] S32. Prepare test specimens. Prepare three parallel standard specimens for each moisture content sample. To obtain the initial state of the soil column, set up a test specimen for each moisture content sample. Place all test specimens in a curing chamber at 20℃ and 30% humidity. Place all test specimens on a mass sensor with an accuracy of 0.1g and monitor the mass change of the test specimens in real time. If the mass of the test specimens drops to a stable level, the soil column and air humidity have reached equilibrium.

[0064] S33. Conduct the experiment by taking out each group of samples from the curing box at the same time every day, recording the mass with an electronic scale, and then quickly putting them back into the curing box to reduce the influence of the measurement environment on the moisture migration process.

[0065] S34. Based on the changes in the mass of soil columns with different moisture contents over time obtained from monitoring, calculate the daily volumetric moisture content of different soils. In the curve of the change in volumetric moisture content of soil over time, the line connecting the start and end points is regarded as the average drainage rate of the core-absorbing geotextile, and then it is converted into the matrix suction head.

[0066] S35. According to the basic soil property formula, the soil moisture content is converted into saturation. This yields the average water conductivity of the wicking geotextile corresponding to soils with different initial moisture contents. Through nonlinear fitting, the relationship between the soil moisture content and the wicking geotextile water conductivity is obtained, establishing the relationship between soil saturation and the wicking geotextile water conductivity. .

[0067] S4 specifically includes the following steps:

[0068] S41. Implement four-field coupling through the PDEs custom coefficient type partial differential equation module and solid mechanics module; during the four-field coupling process, the model size, boundary conditions and the arrangement of monitoring points should be consistent with the experiment.

[0069] S42. In a solid mechanics field, considering the soil as an elastoplastic model, the formula for frost heave force is: In the formula, E is Young's modulus and μ is Poisson's ratio. In response, The formula is: In the formula: η(θ) i The frost heave coefficient is affected by the volumetric ice content in the soil. A semi-empirical formula for determining its value is: ;

[0070] S43. Parameter settings for the solid mechanics field: the top boundary is set as a free end, and the other boundaries are fixed constraints, to observe the deformation of the soil at the top during frost heave and thaw settlement; the cohesion is assigned to the soil cohesion degradation equation in S1, and the internal friction angle is taken as the average value of all triaxial shear test results in S1; when embedding the cohesion equation, the saturation S in the cohesion formula is the result of real-time calculation of the moisture field.

[0071] S44. In a moisture field, the moisture field equation is: In the formula: z is the gravitational potential. ρ is the matrix potential, k is the permeability coefficient, and ρ is the matrix potential. i It is the density of ice, ρ ω It is the density of water, θ u This refers to the unfrozen water content; the outer perimeter of the soil column is a zero flux boundary. When simulating continuous water replenishment, the bottom boundary is set as a Dirichlet boundary, and the saturation S is set to a constant value of 0.99. When simulating closed conditions, the bottom boundary is also set as a zero flux boundary.

[0072] S45. In a temperature field, the governing equation of the temperature field is: In the equation: C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio is used. During the construction of the temperature field, a freeze-thaw cycle temperature condition T is applied to the top boundary and the two sides with a length of 2 cm to simulate the effect of the top of the soil column having a certain thickness of upper temperature control plate. The heating and cooling rate is 2℃ / h, and the other boundaries are at a constant temperature of 10℃.

[0073] The governing equation for S46, the wicking geotextile field, is: This equation was obtained through coupling of wicking geotextile and soil column tests; its specific equation expression should be adjusted accordingly based on the results of the designed test.

[0074] S47. In the water-thermal-mechanical coupling calculation process of COMSOL, the volumetric ice content is converted into the frost heave coefficient using the built-in IF function. The deformation coefficient is then input into the expansion coefficient in COMSOL. The transient solver is used to realize the numerical simulation of the frost heave and thawing settlement process of unsaturated frozen soil.

[0075] Based on the different frost heave levels corresponding to different η values ​​defined in the design specifications, subgrades under different working conditions are divided into five levels: non-frost heave (Level I), weak frost heave (Level II), frost heave (Level III), strong frost heave (Level IV), and extremely strong frost heave (Level V). Taking Level III subgrade as an example, numerical simulation tests of the maximum frost heave (MWG) at different locations revealed that the location of the MWG significantly affects the variation of the maximum frost heave. The vertical distance from the MWG to the top pavement boundary is defined as H (m), and H = 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 (m) are selected. The time-history waterfall plots of the frost heave variation for each group are shown below. Figure 5 As shown in the figure, the condition with a distance of 0 represents the control group without MWG application. The figure shows that MWG significantly reduces the maximum frost heave of the roadbed, and the reduction in maximum frost heave controlled by MWG increases with the number of freeze-thaw cycles. Projecting the maximum frost heave of each condition onto the plane coordinates of frost heave and H reveals that when H ≤ 4.5m, the maximum frost heave gradually decreases with increasing H, and the rate of decrease becomes increasingly smaller. This is because the capillary barrier of MWG is more effective in intercepting rising capillary water as the burial depth increases. However, when H > 4.5m, the maximum frost heave shows a reverse trend, increasing with increasing H. This is attributed to the excessive burial depth of MWG causing the capillary barrier to leave the active freezing front zone, weakening its inhibitory effect on ice lens growth. Nevertheless, the frost heave values ​​of all experimental groups are still significantly lower than the control group, demonstrating the overall effectiveness of MWG in controlling roadbed frost heave, with H = 4.5m being the optimal solution for engineering.

[0076] Based on this, the MWG (Mean Wound Gauge) prevention and control effects were analyzed for roadbeds of Class II, III, IV, and V with H=3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 (m), respectively. Curves showing the variation of η, z, and Z with H for different safety levels were plotted, as shown below. Figures 6-8 As shown, the mathematical expressions for the three can be expressed as follows: In the formula, z represents the total frost heave of the soil (m), and Z represents the corresponding maximum freezing depth (m), excluding frost heave. As can be seen from the figure, Z decreases first and then increases slowly with increasing H, while z decreases first and then remains stable with increasing H. The variation pattern is not obvious for Class 2 roadbeds due to their low baseline. Finally, the variation pattern of η calculated based on S42 is shown in the figure. Figure 8 The decrease in η was greatest when the MWG was laid to a distance of 4.5-5m from the top of the road surface. It can also be seen that the frost heave level of all roadbeds can be reduced by one level when H=4.5-5m. For Class 2 roadbeds, the frost damage prevention requirements are met, so H=4.5m is taken. However, for other roadbed levels, one layer of MWG is insufficient for prevention, necessitating analysis of subsequent multi-layer MWG laying conditions.

[0077] The effectiveness of frost heave fabric (MWG) in controlling frost heave was analyzed for subgrades under the most unfavorable working conditions at each safety level. Priority was given to the control effect of a single layer of MWG at the optimal laying position, followed by the control effect of two layers of MWG at the optimal laying position and spacing. The following optimal construction parameters were ultimately obtained to meet all safety requirements of frost heave subgrades: No control measures are required for Class 1 subgrades; for Class 2 subgrades, a single layer of MWG is laid 4.5m from the road surface; for Class 3-4 subgrades, two layers of MWG are laid, with the top layer 3.5m from the road surface and a 2m spacing between the two layers; for Class 5 subgrades, two layers of MWG are laid, with the top layer 3m from the road surface and a 2.5m spacing between the two layers.

[0078] This invention discloses a quantitative analysis method for water-thermal-mechanical coupling of wicking geotextiles to regulate soil moisture content. This method enables multi-field coupling of wicking geotextiles with water, heat, and force in roadbeds in high-altitude permafrost regions. The coupling method is derived using a combination of indoor experiments and computational theory, making the physical structure of the model more realistic. This invention offers high accuracy and fast calculation speed, effectively simulating the effect of wicking geotextiles on roadbed moisture content regulation. This method can determine the optimal laying position and method of wicking geotextiles in regulating roadbed drainage, thereby improving the efficiency of wicking geotextiles in regulating roadbed moisture and reducing project costs. This invention is not only applicable to high-altitude permafrost roadbeds, but also, based on parameter setting and calibration, to other soil roadbeds, thus expanding the model's applicability.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A quantitative water-thermal-mechanical analysis method for regulating the freeze-thaw cycle process of soil using wicking geotextiles, characterized in that, The specific steps include the following: S1. Conduct triaxial shear tests on soil under freeze-thaw cycles. Using saturation, number of freeze-thaw cycles, and freezing temperature as independent variables, obtain the soil cohesion degradation equation under water-thermal conditions through polynomial fitting. S2. Based on the theoretical expressions of unfrozen water content and initial moisture content, the temperature field control equation and the moisture field control equation are transformed into theoretical equations with saturation S as the independent variable, thereby realizing the coupling of the temperature field and the moisture field. S3. Conduct indoor wicking geotextile-soil column tests to establish the relationship between soil saturation and the water conductivity of wicking geotextile, determine the boundary conditions for the moisture control effect of wicking geotextile, and establish the coupling relationship between wicking geotextile and water field. S4. The calculation methods of stress field, temperature field, moisture field and wicking geotextile in S1, S2 and S3 are written into COMSOL Multiphysics software and fully coupled to realize the quantitative analysis of the regulatory effect of wicking geotextile on subgrade deformation, temperature and humidity under different conditions.

2. The method for quantitative analysis of water-thermal-mechanical processes in regulating soil freeze-thaw cycles using wicking geotextiles according to claim 1, characterized in that, S1 specifically includes the following steps: S11. Prepare triaxial test soil samples. Based on the environmental conditions and basic parameters of the actual project, determine the soil saturation, freezing temperature and number of freeze-thaw cycles. Conduct consolidated undrained triaxial tests to obtain the stress-strain relationship and strength parameter variation law of the soil under different conditions. S12. Based on the obtained stress-strain relationship, according to the Mohr-Coulomb strength theory, the relationships between cohesion-saturation, cohesion-cycle number, and cohesion-freezing temperature are established respectively, and the influence characteristics and trends of each factor on cohesion are obtained. S13. By using the decision tree model in the supervised machine learning algorithm, analyze the influence weights of different saturation, number of cycles, and freezing temperature on cohesion, and obtain the most significant factors affecting soil cohesion. S14. The cohesion degradation equation obtained through polynomial coupling is c=y(S, T, n), where S is the degree of saturation, T is the temperature, and n is the number of cycles.

3. The method for quantitative analysis of water-thermal-mechanical processes in regulating soil freeze-thaw cycles using wicking geotextiles according to claim 2, characterized in that, S2 specifically includes the following steps: S21. The theoretical expression for the relationship between unfrozen water content and initial moisture content is: In the formula, T is the temperature, ω0 is the water content of the unfrozen water at the freezing temperature T, and ω u Let T be the initial mass moisture content of the soil, B be an empirical coefficient related to the solid-liquid ratio, and T be the initial mass moisture content of the soil. f The freezing temperature of the soil; S22. The temperature field governing equation is transformed into an equation with saturation S as the independent variable: In the formula, C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio; S23. The governing equation for the moisture field is transformed into an equation with saturation S as the independent variable: , In the formula, q represents the flow rate. For the matric suction of the soil, k(h) m ) is the permeability coefficient function, h is the matrix suction head, and α is a parameter related to the air intake value in the geotechnical engineering VG model.

4. The method for quantitative analysis of water-thermal-mechanical processes in regulating soil freeze-thaw cycles using wicking geotextiles according to claim 3, characterized in that, S3 specifically includes the following steps: S31. Before the test, the basic properties of the soil were measured; S32. Prepare test specimens. Prepare three parallel standard specimens for each moisture content sample. To obtain the initial state of the soil column, set up a test specimen for each moisture content sample. Place all test specimens in a curing chamber at 20℃ and 30% humidity. Place all test specimens on a mass sensor with an accuracy of 0.1g and monitor the mass change of the test specimens in real time. When the mass of the test specimens decreases to a stable level, the soil column and air humidity reach equilibrium. S33. Conduct the experiment. At the same time every day, take out each group of samples from the curing box in sequence, record the mass with an electronic scale, and then quickly put them back into the curing box. S34. Based on the changes in the mass of soil columns with different moisture contents over time obtained from monitoring, calculate the daily volumetric moisture content of different soils. In the curve of the change in volumetric moisture content of soil over time, the line connecting the start and end points is regarded as the average drainage rate of the core-absorbing geotextile, and then it is converted into the matrix suction head. S35. According to the basic soil property formula, the soil moisture content is converted into saturation. This yields the average water conductivity of the wicking geotextile corresponding to soils with different initial moisture contents. Through nonlinear fitting, the relationship between the soil moisture content and the wicking geotextile water conductivity is obtained, establishing the relationship between soil saturation and the wicking geotextile water conductivity. .

5. The method for quantitative analysis of water-thermal-mechanical processes in regulating soil freeze-thaw cycles using wicking geotextiles according to claim 4, characterized in that, The basic properties of soil in S31 include the liquid limit, plastic limit, optimum moisture content, maximum dry density, mineral composition, saturated moisture content, residual moisture content, and soil-water characteristic curve.

6. The method for quantitative analysis of water-thermal-mechanical processes in regulating soil freeze-thaw cycles using wicking geotextiles according to claim 5, characterized in that, S4 specifically includes the following steps: S41. Four-field coupling is achieved through the PDEs custom coefficient type partial differential equation module and solid mechanics module. S42. In a solid mechanics field, considering the soil as an elastoplastic model, the formula for frost heave force is: In the formula, E is Young's modulus and μ is Poisson's ratio. In response, In the formula: η(θ) i The frost heave coefficient is affected by the volumetric ice content in the soil. A semi-empirical formula for determining its value is: ; S43. Parameter settings for the solid mechanics field: the top boundary is set as a free end, and the other boundaries are fixed constraints, to observe the deformation of the soil at the top during frost heave and thaw settlement; the cohesion is assigned to the soil cohesion degradation equation in S1, and the internal friction angle is taken as the average value of all triaxial shear test results in S1; when embedding the cohesion equation, the saturation S in the cohesion formula is the result of real-time calculation of the moisture field. S44. In a moisture field, the moisture field equation is: In the formula: z is the gravitational potential. ρ is the matrix potential, k is the permeability coefficient, and ρ is the matrix potential. i It is the density of ice, ρ ω It is the density of water, θ u This refers to the unfrozen water content; the outer perimeter of the soil column is a zero flux boundary. When simulating continuous water replenishment, the bottom boundary is set as a Dirichlet boundary, and the saturation S is set to a constant value of 0.

99. When simulating closed conditions, the bottom boundary is also set as a zero flux boundary. S45. In a temperature field, the governing equation of the temperature field is: In the formula: C is the volumetric specific heat capacity, ρ i Where S is the density of ice, S is the degree of saturation, and θ is the density of ice. s and θ r Let T and λ represent the saturated moisture content and residual moisture content, respectively, where T is the temperature, λ is the thermal conductivity, and B is the thermal conductivity. i The solid-liquid ratio is used. During the construction of the temperature field, a freeze-thaw cycle temperature condition T is applied to the top boundary and the two sides with a length of 2 cm to simulate the effect of the top of the soil column having a certain thickness of upper temperature control plate. The heating and cooling rate is 2℃ / h, and the other boundaries are at a constant temperature of 10℃. The governing equation for S46, the wicking geotextile field, is: This equation was obtained through coupling of wicking geotextile and soil column tests. S47. In the water-thermal-mechanical coupling calculation process of COMSOL, the volumetric ice content is converted into the frost heave coefficient using the built-in IF function. The deformation coefficient is then input into the expansion coefficient in COMSOL. The transient solver is used to realize the numerical simulation of the frost heave and thawing settlement process of unsaturated frozen soil.

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