Method and system for predicting the absolute permeability coefficient of unsaturated soils

Abstract

The application discloses a prediction method and system for absolute permeability coefficient of unsaturated soil. The method can ensure the reliability of a unified model of unsaturated relative permeability coefficient by performing data analysis on at least two unsaturated relative permeability coefficient models and performing unified processing, and can further iteratively process the unified model of unsaturated relative permeability coefficient based on air entry suction value and saturated permeability coefficient, construct a quantitative relationship model of absolute permeability coefficient of unsaturated soil, realize quick acquisition of the absolute permeability coefficient of the to-be-tested soil material, and accurately predict unsaturated hydraulic characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, and particularly relates to a method and system for predicting absolute permeability coefficient of unsaturated soil. BACKGROUND

[0002] The unsaturated permeability coefficient is an important parameter in the research of rainfall infiltration of slope, migration of pollutants and the like. There are many factors influencing the size of the permeability coefficient, including the shape, size, non-uniformity coefficient of soil particles and viscosity of water, and it is difficult to establish an accurate theoretical formula for calculating the permeability coefficient.

[0003] However, the existing determination methods of the unsaturated permeability coefficient are divided into direct measurement method and indirect prediction method. The direct measurement method mainly directly measures through transient profile method, wetting peak advancing method and the like, and the test workload is large and the time consumption is long; the indirect prediction method mainly predicts through experience model, macro model and statistical model, wherein the experience model and the macro model aim to predict using a simple mathematical model, and a large amount of data is required to obtain the model parameters; and the statistical model prediction is based on the soil-water characteristic curve test which consumes a long time and has a large calculation workload.

[0004] Therefore, there is a problem that it is difficult to accurately predict the unsaturated hydraulic characteristics in the prior art. SUMMARY

[0005] Therefore, it is necessary to provide a method and system for predicting absolute permeability coefficient of unsaturated soil to solve the problem that it is difficult to accurately predict the unsaturated hydraulic characteristics.

[0006] In order to solve the above problems, the present application provides a method for predicting absolute permeability coefficient of unsaturated soil, comprising:

[0007] obtaining a mass fractal dimension of a to-be-tested soil material;

[0008] obtaining a soil-water characteristic curve fractal model, and substituting the mass fractal dimension into the soil-water characteristic curve fractal model to obtain a saturation degree calculation formula of the to-be-tested soil material;

[0009] obtaining expressions of at least two unsaturated relative permeability coefficient models, combining the saturation degree calculation formula to obtain an unsaturated relative permeability coefficient unified model;

[0010] obtaining an air entry suction value of the to-be-tested soil material;

[0011] substituting the air entry suction value into the unsaturated relative permeability coefficient unified model, and combining a saturated permeability coefficient to determine an unsaturated absolute permeability coefficient of the to-be-tested soil material.

[0012] Further, the mass fractal dimension of the to-be-tested soil material is obtained, comprising:

[0013] Obtaining the clay mass content and the first ratio of the to-be-tested soil material;

[0014] According to the clay mass content and the first ratio, determining the mass fractal dimension of the to-be-tested soil material based on a mass fractal dimension calculation formula;

[0015] The first ratio is the ratio of the upper limit of the clay particle size to the maximum particle size.

[0016] Further, the mass fractal dimension calculation formula is:

[0017]

[0018] The D is the mass fractal dimension, K M is the clay mass content, K R is the first ratio.

[0019] Further, the soil-water characteristic curve fractal model is represented as:

[0020]

[0021] The calculation formula of the saturation of the to-be-tested soil material is:

[0022]

[0023] The θ is the volume water content of the unsaturated soil, θ s is the volume water content of the saturated soil, ψ is the matric suction of the unsaturated soil, ψ a is the air entry suction value of the unsaturated soil, and Sr is the saturation of the to-be-tested soil material.

[0024] Further, the unsaturated relative permeability coefficient model includes the Burdine model, the Mualem model and the T-K model; obtaining expressions of at least two unsaturated relative permeability coefficient models, combining the saturation calculation formula to obtain an unsaturated relative permeability coefficient unified model;

[0025] Deriving the saturation calculation formula to obtain a volume water content reciprocal formula;

[0026] Substituting the volume water content reciprocal formula into the at least two unsaturated relative permeability coefficient models and performing data derivation to obtain the unsaturated relative permeability coefficient unified model.

[0027] Further, the unsaturated relative permeability coefficient unified model is represented as:

[0028]

[0029] The k r is the unsaturated relative permeability coefficient, and β is a parameter related to the fractal dimension of the soil.

[0030] Further, the air entry suction value of the soil to be measured is obtained, comprising:

[0031] The saturated permeability coefficient of the soil to be measured is obtained.

[0032] According to the saturated permeability coefficient, the air entry suction value is calculated based on the air entry suction value calculation formula.

[0033] Further, the air entry suction value calculation formula is:

[0034]

[0035] Wherein, k s is the saturated permeability coefficient of the soil, and k0 is the model proportion constant.

[0036] Further, the non-saturated absolute permeability coefficient calculation formula of the soil to be measured is:

[0037]

[0038] Wherein, k(ψ) is the non-saturated absolute permeability coefficient of the soil to be measured.

[0039] In order to solve the above problems, the application also provides a non-saturated soil absolute permeability coefficient prediction system, comprising:

[0040] The mass fractal dimension acquisition module is used for obtaining the mass fractal dimension of the soil to be measured.

[0041] The saturation calculation module is used for obtaining the soil-water characteristic curve fractal model, and substituting the mass fractal dimension into the soil-water characteristic curve fractal model to obtain the saturation calculation formula of the soil to be measured.

[0042] The non-saturated relative permeability coefficient unified model acquisition module is used for obtaining the expressions of at least two non-saturated relative permeability coefficient models, and combining the saturation calculation formula to obtain the non-saturated relative permeability coefficient unified model.

[0043] The air entry suction value acquisition module is used for obtaining the air entry suction value of the soil to be measured.

[0044] The non-saturated absolute permeability coefficient determination module is used for substituting the air entry suction value into the non-saturated relative permeability coefficient unified model to determine the non-saturated absolute permeability coefficient of the soil to be measured.

[0045] The beneficial effects of the above embodiment are: the application provides a prediction method and system for the absolute permeability coefficient of unsaturated soil, the method can ensure the reliability of the unified model of the unsaturated relative permeability coefficient by analyzing and uniformly processing data of at least two unsaturated relative permeability coefficient models to obtain the unified model of the unsaturated relative permeability coefficient; then, based on the air entry suction value and the saturated permeability coefficient, the unified model of the unsaturated relative permeability coefficient is further iteratively processed to construct a quantitative relationship model of the absolute permeability coefficient of unsaturated soil, so that the absolute permeability coefficient of the to-be-tested soil material is quickly obtained, and the unsaturated hydraulic characteristics are accurately predicted. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 The flowchart of an embodiment of the prediction method for the absolute permeability coefficient of unsaturated soil provided by the application is shown in the figure.

[0047] Figure 2 The flowchart of an embodiment of the method for obtaining the mass fractal dimension of the to-be-tested soil material provided by the application is shown in the figure.

[0048] Figure 3 The flowchart of an embodiment of the method for obtaining the unified model of the unsaturated relative permeability coefficient provided by the application is shown in the figure.

[0049] Figure 4 The comparison chart of the measured value of the absolute permeability coefficient of Reinhausen Pelosol silty clay and the prediction result of the application is provided in the figure.

[0050] Figure 5 The comparison chart of the measured value of the absolute permeability coefficient of sandy loam soil 1 and the prediction result of the application is provided in the figure.

[0051] Figure 6 The comparison chart of the measured value of the absolute permeability coefficient of Weld Aridic Paleustoll fine sandy loam soil and the prediction result of the application is provided in the figure.

[0052] Figure 7 The comparison chart of the measured value of the absolute permeability coefficient of sandy loam soil 2 and the prediction result of the application is provided in the figure.

[0053] Figure 8 The comparison chart of the measured value of the absolute permeability coefficient of Seelow crumbly loam soil and the prediction result of the application is provided in the figure.

[0054] Figure 9 The comparison chart of the measured value of the absolute permeability coefficient of Seelow polyeder loam soil and the prediction result of the application is provided in the figure.

[0055] Figure 10A comparison chart of measured values of the unsaturated absolute permeability coefficient of Schachen sandy soil provided for the present application and the prediction results of the present application is shown in the following table:

[0056] Figure 11 A comparison chart of measured values of the unsaturated absolute permeability coefficient of Buchberg loam soil provided for the present application and the prediction results of the present application is shown in the following table:

[0057] Figure 12 A structure schematic diagram of an embodiment of the prediction system of the unsaturated soil absolute permeability coefficient provided by the present application is shown in the following table: DETAILED DESCRIPTION

[0058] The preferred embodiments of the present application will be specifically described below in conjunction with the accompanying drawings, wherein the drawings form a part of the present application and are used to explain the principles of the embodiments of the present application, but are not used to limit the scope of the present application.

[0059] Before the embodiments are stated, the soil-water characteristic curve is described:

[0060] The soil-water characteristic curve (SWCC) is a curve of the change of the matric potential (or soil water suction) of soil water with the soil water content, which reflects the relationship between the soil water energy and quantity, is an important basis for predicting the shear strength, permeability coefficient, volumetric strain of unsaturated soil, and the distribution of water above the groundwater level, and has important significance in production practice. The soil-water characteristic curve essentially reflects the distribution rule of pore volume (mass) - pore size.

[0061] The unsaturated permeability coefficient is an important parameter in the research of rainfall infiltration of slope, pollutant migration, etc. There are many factors that affect the size of the permeability coefficient, including the shape, size, non-uniformity coefficient of soil particles, and viscosity of water, etc., and it is difficult to establish an accurate theoretical formula for calculating the permeability coefficient.

[0062] However, the existing determination methods of the unsaturated permeability coefficient are divided into direct measurement method and indirect prediction method. The direct measurement method mainly directly measures through transient profile method, wetting front advance method, etc., and the test workload is large and the time-consuming is long; the indirect prediction method mainly predicts through empirical model, macro model and statistical model, wherein the empirical model and macro model aim to predict using a simple mathematical model, and a large amount of data is needed to obtain the model parameters; and the statistical model prediction work is based on the soil-water characteristic curve test which takes a long time and has a large amount of calculation work, which leads to difficulty in accurately predicting the unsaturated hydraulic characteristics.

[0063] Therefore, there is a problem of difficulty in accurately predicting the unsaturated hydraulic characteristics in the prior art.

[0064] The absolute permeability coefficient of the unsaturated soil is a parameter for describing the fluid permeability in the unsaturated medium. The absolute permeability coefficient is a characteristic inherent to the medium itself, and represents the permeability of the fluid through the medium in a fully saturated state. The unsaturated hydraulic characteristics can also be represented by the absolute permeability coefficient of the unsaturated soil, so as to accurately predict the unsaturated hydraulic characteristics.

[0065] To solve the above problems, the present application provides a method and system for predicting the absolute permeability coefficient of unsaturated soil, which are described in detail below.

[0066] As shown in Figure 1 , the flowchart of an embodiment of the method for predicting the absolute permeability coefficient of unsaturated soil provided by the present application comprises the following steps. Figure 1

[0067] Step S101: obtaining the mass fractal dimension of the soil to be measured.

[0068] Step S102: obtaining the soil-water characteristic curve fractal model, and substituting the mass fractal dimension into the soil-water characteristic curve fractal model to obtain a saturation calculation formula of the soil to be measured.

[0069] Step S103: obtaining the expression of at least two unsaturated relative permeability coefficient models, and combining the saturation calculation formula to obtain a unified model of the unsaturated relative permeability coefficient.

[0070] Step S104: obtaining the air entry suction value of the soil to be measured.

[0071] Step S105: substituting the air entry suction value into the unified model of the unsaturated relative permeability coefficient, and combining the saturated permeability coefficient to determine the absolute permeability coefficient of the unsaturated soil to be measured.

[0072] In this embodiment, first, the mass fractal dimension of the soil to be measured and the soil-water characteristic curve fractal model are obtained, and the mass fractal dimension is substituted into the soil-water characteristic curve fractal model to obtain a saturation calculation formula of the soil to be measured. Then, the expression of at least two unsaturated relative permeability coefficient models is obtained, and the saturation calculation formula is combined to obtain a unified model of the unsaturated relative permeability coefficient. Finally, the air entry suction value of the soil to be measured is obtained, and the air entry suction value is substituted into the unified model of the unsaturated relative permeability coefficient, and the saturated permeability coefficient is combined to determine the absolute permeability coefficient of the unsaturated soil to be measured.

[0073] ​In the embodiment, the unified model of the unsaturated relative permeability coefficient is obtained by analyzing and uniformly processing data of at least two unsaturated relative permeability coefficient models, so that the reliability of the unified model of the unsaturated relative permeability coefficient can be ensured; then, the unified model of the unsaturated relative permeability coefficient is further iteratively processed based on the air intake suction value and the saturated permeability coefficient, so that the quantitative relationship model of the absolute permeability coefficient of the unsaturated soil is constructed, the absolute permeability coefficient of the to-be-tested soil material is quickly obtained, and the unsaturated hydraulic characteristics are accurately predicted.

[0074] As a preferred embodiment, in step S101, in order to obtain the mass fractal dimension of the to-be-tested soil material, the mass fractal dimension of the to-be-tested soil material is determined based on the mass fractal dimension calculation formula. Figure 2 Figure 2 The flowchart of the embodiment for obtaining the mass fractal dimension of the to-be-tested soil material provided by the application comprises:

[0075] Step S111: obtaining the clay mass content and the first ratio of the to-be-tested soil material;

[0076] Step S112: determining the mass fractal dimension of the to-be-tested soil material based on the mass fractal dimension calculation formula according to the clay mass content and the first ratio.

[0077] The first ratio is the ratio of the upper limit of the clay particle size to the maximum particle size.

[0078] As a preferred embodiment, in step S111, in order to obtain the clay mass content of the to-be-tested soil material, first, the to-be-tested soil sample is obtained, and the mass of the sample is denoted as M T ; then, the particles with a particle size less than R are defined as clay, and the clay content is denoted as M; finally, the clay mass content is determined according to the clay mass content formula.

[0079] The calculation formula of the clay mass content K M is as follows:

[0080] K M = M / M T

[0081] Further, in order to obtain the first ratio, the maximum particle size R max is obtained on the basis of the upper limit of the clay particle size R, and then the ratio of the two is determined as the first ratio, wherein the calculation formula of the first ratio K R is as follows:

[0082] K R = R / R max

[0083] In a specific embodiment, the upper limit of the clay particle size R is 0.002 mm.

[0084] ​In a preferred embodiment, in step S112, based on determining the clay content and the first ratio, it is also necessary to determine the mass fractal dimension of the soil to be tested based on the mass fractal dimension calculation formula.

[0085] In one specific embodiment, the formula for calculating the mass fractal dimension is:

[0086]

[0087] Where D is the mass fractal dimension, K M K represents the mass content of clay particles. R This is the first ratio.

[0088] It should be noted that the formula for calculating the mass fractal dimension is based on the assumption that the minimum particle size is 0, and the calculation error decreases as the minimum particle size decreases.

[0089] In a preferred embodiment, in step S102, in order to obtain the saturation calculation formula for the soil to be tested, firstly, the fractal model of the soil-water characteristic curve (SWCC) of unsaturated soil established by Bird et al. based on the pore-soil-fractal (PSF) model is obtained, wherein the soil-water characteristic curve fractal model is expressed as:

[0090]

[0091] Where θ is the volumetric water content of the unsaturated soil, θ s Let ψ be the volumetric water content of saturated soil, and ψ be the matric suction of unsaturated soil. a This represents the air intake suction value for unsaturated soil.

[0092] Next, in order to obtain the relationship between the particle mass fractal dimension and the soil-water characteristic curve, equation (1) is substituted into equation (2) to obtain the following formula for calculating the saturation of the soil to be tested:

[0093]

[0094] Wherein, Sr represents the saturation of the soil material being tested.

[0095] In a preferred embodiment, in step S103, in order to obtain a unified model for the unsaturated relative permeability coefficient and achieve unified processing of the unsaturated relative permeability coefficient, such as... Figure 3 As shown, Figure 3 A schematic flowchart illustrating an embodiment of the unified model for obtaining unsaturated relative permeability coefficients provided by the present invention includes:

[0096] Step S131: Differentiate the saturation calculation formula to obtain the reciprocal formula for volumetric water content;

[0097] Step S132: substituting the volumetric water content reciprocal formula into at least two unsaturated relative permeability coefficient models, and performing data derivation to obtain an unsaturated relative permeability coefficient unified model.

[0098] As a preferred embodiment, in step S131, the calculation formula of the volumetric water content reciprocal formula is obtained by deriving both ends of formula (3) as follows:

[0099]

[0100] As a preferred embodiment, in step S132, the unsaturated relative permeability coefficient model includes a Burdine model, a Mualem model, and a T-K model.

[0101] Among them, Burdine deduces the formula for calculating the relative permeability from the pore size distribution data according to the basic law of fluid flow in porous media, and the expression is as follows:

[0102]

[0103] Among them, k r (θ) is the unsaturated relative permeability coefficient.

[0104] Mualem proposed a simple analytical model for predicting the unsaturated hydraulic conductivity curve using the measured values of water content-capillary water head curve and saturated hydraulic conductivity, and the expression is as follows:

[0105]

[0106] Tao proposed a new unsaturated permeability coefficient model based on micro-pore channels, and the expression is as follows:

[0107]

[0108] After obtaining the above expressions (5)-(7), the volumetric water content reciprocal formula needs to be substituted into the unsaturated relative permeability coefficient model to obtain the relationship between the unsaturated permeability coefficient and the matrix suction.

[0109] Taking the Burdine model as an example, substituting formula (4) into formula (5) to obtain:

[0110]

[0111] Among them, ψ max is the maximum suction value, and ψ max >> ψ.

[0112] The residual water content can be considered as a part of the particle, and it can be approximately considered that S e =S r .

[0113] Tao gives the fractal form of the soil-water characteristic curve expressed by saturation, when ψ≥ψ a , Sr=(ψ a / ψ) 3-D , combined with equation (1), equation (8) will be converted to:

[0114]

[0115] Through the above operation, the process of obtaining the unsaturated relative permeability coefficient can be simplified, which is conducive to accurately predicting the unsaturated hydraulic characteristics.

[0116] Further, by substituting equation (4) into equations (6) and (7), respectively, we obtain:

[0117]

[0118]

[0119] In order to unify the form of the unsaturated relative permeability coefficient, by fusing equations (9), (10) and (11), the unified model of the unsaturated relative permeability coefficient is obtained, which is expressed as:

[0120]

[0121] where k r is the unsaturated relative permeability coefficient, and β is a parameter related to the fractal dimension of the soil.

[0122] In the process of simplifying the unified model, the corresponding relationship under three different conditions is summarized. Obviously, in the Burdine model, β=3; in the Mualem model, β=2.5; and in the T-K model, β=1.

[0123] In a specific embodiment, the value of β can also be adaptively adjusted as needed to improve the reliability of the unsaturated relative permeability coefficient obtained finally.

[0124] After obtaining the unified model of the unsaturated relative permeability coefficient, in order to obtain the unsaturated absolute permeability coefficient, further conversion is needed.

[0125] It should be noted that the non-saturated relative permeability coefficient is a parameter describing the fluid permeability in the non-saturated medium. In the non-saturated state, the pores in the medium contain both gas and liquid. The relative permeability coefficient is used to represent the size of the absolute permeability of various fluids (usually liquid) in the non-saturated medium relative to the saturated state. The relative permeability coefficient is a dimensionless value between 0 and 1, where 0 represents that the corresponding phase has no permeability in the medium, and 1 represents that the corresponding phase completely permeates the medium.

[0126] The non-saturated absolute permeability coefficient is a parameter describing the fluid permeability in the non-saturated medium. The absolute permeability coefficient is a characteristic inherent to the medium itself, representing the permeability of the fluid through the medium in the completely saturated state.

[0127] The non-saturated relative permeability coefficient is a function of the non-saturated absolute permeability coefficient, and the value of the non-saturated relative permeability coefficient can be calculated or estimated according to the medium properties in the non-saturated state and the absolute permeability coefficient in the saturated state. The relationship between the two is usually obtained by experimental measurement and can be represented by an empirical formula or a mathematical model. In hydrogeology research, one of the commonly used models is the Van Genuchten model, which represents the non-saturated relative permeability coefficient as a function of the saturation and uses some parameters to describe the permeability of the medium.

[0128] Specifically, the non-saturated absolute permeability coefficient = non-saturated relative permeability coefficient * saturated permeability coefficient.

[0129] Therefore, the saturated permeability coefficient needs to be obtained to represent the non-saturated absolute permeability coefficient.

[0130] As a preferred embodiment, in step S104, since the air-entry value is an important parameter for applying various methods to predict the non-saturated relative permeability coefficient, the air-entry value is included in the non-saturated relative permeability coefficient unified model. However, the prediction of the air-entry value is mostly obtained by fitting the classical model (such as the VG model, the Fredlund-Xing model, etc.) of the soil-water characteristic curve, and then using a simple mapping method or an empirical formula, which is time-consuming and laborious in the test process, and the model calculation is relatively complex and cumbersome. In comparison, the test measurement of the saturated permeability coefficient is more rapid and convenient, therefore, the saturated permeability coefficient is obtained by a simplified relationship model of the soil saturated permeability coefficient and the air-entry value, and the specific expression is as follows:

[0131] k s = k0ψ a -2 (13)

[0132] where k sis the saturated permeability coefficient of soil, k0 is a model constant.

[0133] It is to be noted that k s It can be quickly obtained by test methods such as variable head method, and k0 is a model constant, and for different soils, respectively: k0 = 0.03051 for sandy soil; k0 = 0.001878 for clay; k0 = 0.001426 for loam; k0 = 0.009301 for sandy loam; and k0 = 0.0007055 for silty clay loam.

[0134] Further, in order to reduce the number of variables in the data processing process, the air entry suction value is inversely solved and substituted into equation (12), so as to determine the unsaturated absolute permeability coefficient.

[0135] The calculation formula of the air entry suction value is:

[0136]

[0137] The calculation formula of the unsaturated absolute permeability coefficient is:

[0138]

[0139] Wherein, k(ψ) is the unsaturated absolute permeability coefficient of the soil to be measured.

[0140] In summary, through analysis and processing of data, the relationship between the unsaturated absolute permeability coefficient and the matric suction of unsaturated soil is obtained, and the unsaturated absolute permeability coefficient of unsaturated soil can be quickly obtained, so as to accurately predict the unsaturated hydraulic characteristics.

[0141] In order to verify the reliability of the above method, through experimental comparison, respectively as Figure 4 shown, Figure 4 is a comparison chart of the measured value and the prediction result of the unsaturated absolute permeability coefficient of Reinhausen Pelosol silty clay loam provided by the application; as Figure 5 shown, Figure 5 is a comparison chart of the measured value and the prediction result of the unsaturated absolute permeability coefficient of sandy loam 1 provided by the application; as Figure 6 shown, Figure 6 is a comparison chart of the measured value and the prediction result of the unsaturated absolute permeability coefficient of Weld Aridic Paleustoll fine sandy loam provided by the application; as Figure 7 shown, Figure 7 is a comparison chart of the measured value and the prediction result of the unsaturated absolute permeability coefficient of sandy loam 2 provided by the application; as Figure 8 shown, Figure 8A comparison chart of measured values and prediction results of the absolute unsaturated permeability coefficient of Seelow crumbly loam provided by the present application is shown in FIG. Figure 9 Figure 9 A comparison chart of measured values and prediction results of the absolute unsaturated permeability coefficient of Seelow polyeder loam provided by the present application is shown in FIG. Figure 10 Figure 11 A comparison chart of measured values and prediction results of the absolute unsaturated permeability coefficient of Schachen sandy soil provided by the present application is shown in FIG. Figure 11

[0142] In the above manner, the unified model of the unsaturated relative permeability coefficient is obtained by data analysis and unified processing of at least two unsaturated relative permeability coefficient models, so as to ensure the reliability of the unified model of the unsaturated relative permeability coefficient. Then, the quantitative relationship model of the absolute permeability coefficient of unsaturated soil is constructed by further iterative processing of the unified model of the unsaturated relative permeability coefficient based on the air entry suction value and the saturated permeability coefficient, so as to quickly obtain the absolute permeability coefficient of the to-be-tested soil, thereby accurately predicting the unsaturated hydraulic characteristics.

[0143] To solve the above problems, the present application further provides a prediction system for the absolute permeability coefficient of unsaturated soil, as shown in FIG. Figure 12 Figure 12 A structure schematic diagram of an embodiment of the prediction system for the absolute permeability coefficient of unsaturated soil provided by the present application, the prediction system 1200 for the absolute permeability coefficient of unsaturated soil comprises:

[0144] The mass fractal dimension acquisition module 1201 is configured to acquire the mass fractal dimension of the to-be-tested soil;

[0145] The saturation calculation module 1202 is configured to acquire the soil-water characteristic curve fractal model, and substitute the mass fractal dimension into the soil-water characteristic curve fractal model to obtain a saturation calculation formula of the to-be-tested soil;

[0146] The unified model of the unsaturated relative permeability coefficient acquisition module 1203 is configured to acquire the expressions of at least two unsaturated relative permeability coefficient models, and obtain the unified model of the unsaturated relative permeability coefficient in combination with the saturation calculation formula;

[0147] The air entry suction value acquisition module 1204 is configured to acquire the air entry suction value of the to-be-tested soil;

[0148] The unsaturated absolute permeability coefficient determination module 1205 is configured to substitute the air entry suction value into the unified model of the unsaturated relative permeability coefficient to determine the absolute permeability coefficient of the to-be-tested soil. ​​​​

[0149] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application.

Claims

1. A method for predicting the absolute permeability coefficient of unsaturated soil, characterized in that, include: Obtaining the mass fractal dimension of the soil sample to be tested includes: obtaining the clay content and a first ratio of the clay content and the first ratio of the soil sample to be tested; determining the mass fractal dimension of the soil sample to be tested based on the mass fractal dimension calculation formula, according to the clay content and the first ratio; wherein, the first ratio is the ratio of the upper limit of the clay particle size to the maximum particle size. Obtain the fractal model of the soil-water characteristic curve, and substitute the mass fractal dimension into the fractal model to obtain the saturation calculation formula for the soil to be tested. The formula for calculating the mass fractal dimension is as follows: Where D is the mass fractal dimension, K M K represents the mass content of the clay particles. R The first ratio is given; the fractal model of the soil-water characteristic curve is expressed as: The formula for calculating the saturation of the soil sample to be tested is as follows: Where θ is the volumetric water content of the unsaturated soil, θ s Let ψ be the volumetric water content of the saturated soil, and ψ be the matrix suction of the unsaturated soil. a Sr is the air intake suction value of the unsaturated soil, and Sr is the degree of saturation of the soil to be tested. Obtain expressions for at least two unsaturated relative permeability coefficient models, and combine them with the saturation calculation formula to obtain a unified unsaturated relative permeability coefficient model, which is expressed as: in, β is the unsaturated relative permeability coefficient, and β is a parameter related to the fractal dimension of the soil. Obtaining the air intake suction value of the soil sample to be tested includes: obtaining the saturated permeability coefficient of the soil sample to be tested; and, based on the saturated permeability coefficient and an air intake suction value calculation formula, obtaining the air intake suction value, wherein the air intake suction value calculation formula is as follows: Where, k s K is the saturated permeability coefficient of the soil, and k0 is the model proportionality constant; The formula for calculating the unsaturated absolute permeability coefficient of the soil sample to be tested is as follows: in, The unsaturated absolute permeability coefficient of the soil to be tested; Substitute the intake suction value into the unified model of unsaturated relative permeability coefficient, and combine it with the saturated permeability coefficient to determine the unsaturated absolute permeability coefficient of the soil to be tested.

2. The method for predicting the absolute permeability coefficient of unsaturated soil according to claim 1, characterized in that, The unsaturated relative permeability coefficient models include the Burdine model, the Mualem model, and the TK model; by obtaining the expressions of at least two unsaturated relative permeability coefficient models and combining them with the saturation calculation formula, a unified unsaturated relative permeability coefficient model is obtained. Differentiating the saturation calculation formula yields the volumetric water content derivative formula; Substituting the inverse formula of volumetric water content into the at least two unsaturated relative permeability coefficient models and performing data derivation, a unified model of unsaturated relative permeability coefficient is obtained.

3. A system for predicting the absolute permeability coefficient of unsaturated soil, used to execute the method for predicting the absolute permeability coefficient of unsaturated soil as described in any one of claims 1-2, characterized in that, include: The mass fractal dimension acquisition module is used to obtain the mass fractal dimension of the soil material to be tested. The saturation calculation module is used to obtain the fractal model of the soil-water characteristic curve, and substitute the mass fractal dimension into the fractal model of the soil-water characteristic curve to obtain the saturation calculation formula of the soil to be tested. The module for obtaining a unified model of unsaturated relative permeability coefficient is used to obtain the expressions of at least two unsaturated relative permeability coefficient models, and combine them with the saturation calculation formula to obtain a unified model of unsaturated relative permeability coefficient. The air intake suction value acquisition module is used to acquire the air intake suction value of the soil to be tested; The unsaturated absolute permeability coefficient determination module is used to substitute the air intake suction value into the unsaturated relative permeability coefficient unified model to determine the unsaturated absolute permeability coefficient of the soil to be tested.

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