Method and system for evaluating internal permeability stability of natural foundation

Abstract

The invention discloses a natural foundation internal permeability stability evaluation method and system, and belongs to the technical field of water conservancy and hydropower. The method comprises the following steps: acquiring and preprocessing soil body parameters, proposing soil body internal permeability stability evaluation indexes integrating soil body grading, accumulation state and overburden pressure factors, calculating the internal permeability stability of a soil sample in a target foundation area, constructing a multi-stage index threshold system, and judging the internal permeability stability of a natural foundation by combining probability evaluation. The system comprises a data acquisition module, a calculation module and a comprehensive evaluation module. The method breaks through the limitation of single factor evaluation, improves the evaluation accuracy, establishes a multi-level index threshold system to provide probability basis, guarantees the engineering safety, and meets the actual demands.

Description

Technical Field

[0001] The present application relates to the field of water conservancy and hydropower technology, and more specifically to a method and system for evaluating the internal seepage stability of a natural foundation. Background Art

[0002] In the field of water conservancy projects, the natural foundations of key facilities such as dams and levees are generally characterized by complex composition, significant structural differences, and variable sedimentary sequences. Their particle grading spans a large range and exhibits strong heterogeneity. The internal seepage stability of natural foundations is a key scientific issue to ensure the long-term safe operation of water conservancy projects such as dams and levees. Internal seepage stability refers to the ability of soil to effectively prevent the movement and loss of particles and maintain the integrity of its own structure under the action of seepage. Relevant studies have shown that foundations with poor internal seepage stability are prone to internal erosion under the action of seepage, which can cause reservoir water leakage, uneven settlement of the dam body, and even serious consequences such as dam failure, posing a huge threat to people's lives and property safety and the ecological environment.

[0003] Existing methods for evaluating the internal seepage stability of soils are primarily based on soil gradation analysis, neglecting the effects of soil accumulation and overburden pressure on the internal seepage stability. In practical engineering, soil accumulation directly influences the interaction between particles, while overburden pressure alters the stress state of particles, jointly influencing the internal seepage stability of the soil. However, the single analytical framework of existing evaluation methods fails to capture the interactions of multiple factors, potentially leading to deviations between the evaluation results and the actual seepage response of the soil. Furthermore, the seepage stability of natural foundations is essentially the result of the synergistic interaction of multiple soil components. Existing methods for evaluating the internal seepage stability of soils are limited to analyzing a single soil gradation and fail to integrate the synergistic mechanism of the multi-soil gradation system in natural foundations. Consequently, their evaluation results fail to reflect the internal seepage stability of the foundation. Therefore, developing a method and system for evaluating the internal seepage stability of natural foundations that can comprehensively consider multiple factors is of great practical significance. Summary of the Invention

[0004] In view of this, the present invention provides a method and system for evaluating the internal seepage stability of a natural foundation, aiming to solve the problem that the existing method for evaluating the internal seepage stability of soil is difficult to integrate multiple factors and cannot comprehensively judge the overall internal seepage stability of the natural foundation.

[0005] One of the present inventions is achieved through the following technical solutions:

[0006] A method and system for evaluating the internal seepage stability of a natural foundation, characterized by comprising the following steps:

[0007] S1. Obtain soil parameters at different locations and depths of the target natural foundation, perform preprocessing, and generate preliminary results of the internal seepage stability of the soil sample;

[0008] S2. Taking into account the soil gradation, accumulation state and overburden pressure factors, a calculation method for evaluating the internal seepage stability index of the soil is proposed, and the internal seepage stability of the soil sample in the target foundation area is calculated;

[0009] S3. Based on the internal seepage stability evaluation results of all soil samples in the target foundation area, combined with the mean μ and standard deviation σ of the evaluation index values, and considering the critical values ​​of "mean μ" and "mean μ-standard deviation σ", a multi-level index threshold system for internal seepage stability of natural foundations is constructed to complete the preliminary classification of the internal seepage stability of natural foundations;

[0010] S4. Considering different confidence intervals and assurance rates, uncertainty analysis is performed on the grading results of the internal seepage stability of the target foundation to achieve a probabilistic assessment of the internal seepage stability of the natural foundation.

[0011] Furthermore, the soil parameters and factors include particle size parameters, porosity, accumulation state and overburden pressure.

[0012] Furthermore, the pre-processing includes:

[0013] S1. Use sieving method or laser particle size analyzer method to carry out particle size distribution analysis, obtain soil gradation curve, and generate preliminary results of soil sample internal permeability stability;

[0014] S2. Analyze the soil accumulation state through relative density Dr, D r =(e max -e) / (e max -e min ), where e is the natural porosity; e max is the porosity ratio of the soil in the loosest state; e min is the void ratio of the soil in its most dense state;

[0015] S3. Calculate the overburden pressure of the soil and define the overburden pressure coefficient. The formula is: σ * =σ v / (γ′H max ), where σv is the overburden pressure at the depth of the soil, γ′ is the effective density of the soil, and Hmax is the reference depth.

[0016] Furthermore, when obtaining the overburden pressure data of soil at different depths, if only a small number of depth points are missing, the data can be filled by linear interpolation. According to the overburden pressure values ​​of known depth points, linear calculation is performed according to the depth ratio to obtain the estimated overburden pressure values ​​of the missing points.

[0017] Furthermore, the calculation formula of the evaluation index is:

[0018] SF=SFb ·SF p ·SF s

[0019] Among them, SF b is a grading item, which is the basic item of evaluation index; SF p is the accumulation state correction term, which corrects the influence of soil accumulation structure differences; SF s is the overburden pressure suppression term, which characterizes the stress suppression effect of the overburden pressure on the particles.

[0020] Furthermore, the basic item SF in the evaluation index b , calculated according to the Kenney-Lau criterion, the formula is:

[0021] SF b =(H / F) min

[0022] Where H is the mass percentage corresponding to any particle size d; F is the mass percentage corresponding to particles with any particle size between d and 4d.

[0023] Further, determine the accumulation state correction term SF in the evaluation index p and the overburden pressure suppression term SF s , the formula is:

[0024]

[0025] Among them, k1 is the coefficient obtained by fitting, which is used to adjust the influence of the stacking state on the internal permeation stability; D r is the relative density, which characterizes the soil accumulation state; D r0 is the reference value of relative density; k2 is the coefficient used to adjust the influence of overburden pressure; f c is the fine particle content; σ * is the overburden pressure coefficient.

[0026] Furthermore, the multi-level index threshold system for internal seepage stability of natural foundations includes: dividing the internal seepage stability of soil into four levels: "stable", "relatively stable", "basic stable", and "unstable"; constructing a multi-level internal seepage stability threshold system for natural foundations based on the mean μ and standard deviation σ, which is initially divided into "Level I (safe)", "Level II (mild)", "Level III (moderate)", and "Level IV (high risk)".

[0027] The second aspect of the present invention is achieved through the following technical solutions:

[0028] A natural foundation internal seepage stability evaluation system, characterized by comprising:

[0029] The data acquisition module is used to obtain soil sample parameters in the target foundation area, perform preprocessing, and generate preliminary results on the internal seepage stability of the soil;

[0030] A data calculation module is used to propose a calculation method for evaluating the internal seepage stability of soil based on a comprehensive consideration of soil gradation, accumulation state, and overburden pressure factors, quantify the internal seepage stability of the soil sample in the target foundation area, and output the quantitative results of the internal seepage stability of the soil sample;

[0031] The comprehensive evaluation module is used to generate the internal seepage stability evaluation results of all soil samples in the target foundation area based on the soil internal seepage stability calculation model, and obtain the comprehensive evaluation results of the internal seepage stability of the target natural foundation through statistical analysis.

[0032] Furthermore, the comprehensive evaluation module includes:

[0033] Data statistical calculation unit, used to calculate the mean and standard deviation of the internal seepage stability of soil samples;

[0034] A threshold system construction unit is used to construct a multi-level index threshold system for internal seepage stability of natural foundations based on mean and standard deviation;

[0035] The comprehensive probability assessment unit is used to select appropriate confidence intervals and assurance rates, conduct uncertainty analysis on the internal seepage stability classification results of the target foundation, and realize the probabilistic assessment of the internal seepage stability of the natural foundation.

[0036] The beneficial effects of the present invention are:

[0037] 1. Comprehensive multi-factor evaluation breaks through the limitations of traditional single-factor evaluation, making the evaluation of soil internal seepage stability more scientific and reasonable, and significantly improving the accuracy of soil internal seepage stability evaluation;

[0038] 2. Establish a multi-level index threshold system for the internal seepage stability of natural foundations, introduce confidence intervals and assurance rates, conduct uncertainty analysis on the internal seepage stability grading results of the target foundation, provide a traceable probabilistic basis for decision-making, ensure project safety, and meet the actual needs of the project. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of a natural foundation internal seepage stability evaluation system according to an embodiment of the present application;

[0040] Figure 2 This is a natural foundation soil gradation curve diagram of an embodiment of the present application;

[0041] Figure 3 This is a logic diagram of the internal seepage stability evaluation of a natural foundation according to one embodiment of the present application;

[0042] Figure 4 It is a structural diagram of a comprehensive evaluation module of a natural foundation internal seepage stability evaluation system according to an embodiment of the present application. DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0045] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0046] In the above description of the present invention, it should be noted that the terms "one side," "the other side," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and the like are used solely for distinction and should not be construed as indicating or implying relative importance.

[0047] Furthermore, the term "identical" and similar terms do not necessarily require that the components be absolutely identical; slight variations are permitted. The term "perpendicular" simply refers to the positional relationship between components being more perpendicular than "parallel," not that the structure must be perfectly vertical; rather, it can be slightly tilted.

[0048] The following describes a method and apparatus for comprehensively evaluating the internal seepage stability of natural foundations according to an embodiment of the present application with reference to the accompanying drawings. With respect to the related technologies mentioned in the background art, the current technical field lacks an effective means for comprehensively evaluating the internal seepage stability of natural foundations. This situation makes it difficult to conduct targeted analysis when facing foundations with poor internal seepage stability, seriously threatening the safety of stable operation of water conservancy projects. The present application provides a method for evaluating the internal seepage stability of natural foundations. In this method, based on existing seepage stability criteria, a preliminary judgment is made on the internal seepage stability of the soil. The soil gradation, stacking state, and overburden pressure factors are incorporated into the soil internal seepage stability evaluation index, overcoming the limitations of traditional single-factor evaluation and comprehensively and accurately reflecting the internal seepage stability of the soil. Based on the mean μ and standard deviation σ, a multi-level index threshold system for the internal seepage stability of natural foundations is constructed to complete the preliminary classification of the internal seepage stability of the foundation. Different confidence intervals (e.g., 90%, 95%) and guarantee rates are further introduced to perform uncertainty analysis on the internal seepage stability classification results of the target foundation, thereby achieving a probabilistic assessment of the internal seepage stability of the natural foundation.

[0049] Example 1

[0050] like Figure 1 As shown, the embodiment of the present application discloses a method for evaluating the internal seepage stability of a natural foundation, comprising:

[0051] S1: Obtain soil parameters at different locations and depths of the target natural foundation and perform preprocessing;

[0052] In the embodiment of the present application, the soil sample parameters required include d1, d5, d 10 d 20 d 30 d 40 d 60 d 90 . Among them: d i is the particle size corresponding to mass percentage i; H is the mass percentage corresponding to any particle size d; F is the mass percentage corresponding to particles with any particle size between d and 4d; e is the natural porosity ratio; e max is the porosity ratio of the soil in the loosest state; e min is the void ratio of the soil in its most dense state.

[0053] In the actual implementation process, it is necessary to analyze the particle gradation of the collected soil samples and draw the soil gradation curve, such as Figure 2 As shown in the figure, a preliminary judgment on the internal seepage stability of the soil sample is made based on the Kenney-Lau criterion, and the formula is:

[0054] SF b =(H / F) min

[0055] Among them, SF b It is the grading item of the internal seepage stability of the soil.

[0056] In the embodiment of the present application, the internal permeability stability of the soil is affected by the accumulation state and the overburden pressure factors. The definitions and calculation formulas of the factors are as follows:

[0057] The soil accumulation state is determined by using the relative density D r Characterization is used to reflect the density and structural characteristics of soil under natural or specific conditions. The formula is:

[0058] D r =(e max -e) / (e max -e min )

[0059] Where, e is the natural porosity ratio; e max is the porosity ratio of the soil in the loosest state; e min is the void ratio of the soil in its most dense state.

[0060] Overburden pressure refers to the vertical pressure borne by the soil from the soil above it or other loads. Its existence will change the stress state of the particles. The overburden pressure coefficient σ is defined as * , the formula is:

[0061] σ * =σ v / (γ′H max )

[0062] Among them, σ v is the overburden pressure at the depth of the soil, which usually increases with the increase of burial depth; γ′ is the effective weight of the soil; H max is the reference depth.

[0063] Preferably, in this embodiment, the test results of the internal seepage stability of a natural foundation of a certain project are shown in Table 1:

[0064] Table 1: Test results of internal seepage stability of natural foundation

[0065]

[0066]

[0067] S2: Taking into account the soil gradation, accumulation state and overburden pressure factors, a calculation method for the soil internal seepage stability evaluation index is proposed to calculate the soil internal seepage stability;

[0068] Specifically, soil gradation primarily refers to geometric conditions, while the accumulation state influences the interactions between particles, and overburden pressure alters the stress state of the soil. Evaluation indicators must comprehensively consider the geometric conditions, the influence of the modified soil accumulation state, and the stress-suppressing effect of overburden pressure. By combining the effects of soil gradation, accumulation state, and overburden pressure, a more scientific comprehensive evaluation model for soil internal permeability stability can be constructed. This model can reflect the impact of soil gradation, accumulation state, and overburden pressure at different burial depths on the internal permeability stability of soil samples.

[0069] As a preferred embodiment of the above, the calculation formula of the evaluation index is:

[0070] SF=SF b ·SF p ·SF s

[0071] Among them, SF b is a grading item, which is the basic item of evaluation index; SF p is the accumulation state correction term, which corrects the influence of soil accumulation structure differences; SF s is the overburden pressure suppression term, which characterizes the stress suppression effect of the overburden pressure on the particles.

[0072] Furthermore, the accumulation state correction term SF is determined p The influence of is:

[0073]

[0074] Among them, k1 is the coefficient obtained by fitting, which is used to adjust the influence of the stacking state on the internal permeation stability; D r is the relative density, which characterizes the soil accumulation state; D r0 To calibrate the relative density.

[0075] Furthermore, the overburden pressure suppression term SF is determined s , the formula is

[0076]

[0077] Among them, k2 is a coefficient used to adjust the influence of fine particle content and overburden pressure; f c is the fine particle content; σ * is the overburden pressure coefficient.

[0078] Overall, the soil internal seepage stability formula SF comprehensively considers the effects of soil gradation, stacking state, and overburden pressure, and can establish a more scientific and comprehensive evaluation system. This greatly improves the accuracy of the soil internal seepage stability assessment and provides a solid and reliable basis for the subsequent judgment of the overall internal seepage stability of natural foundations.

[0079] S3: Based on the internal seepage stability data of all soil samples of the target natural foundation after statistical analysis, a multi-level index threshold evaluation system for the internal seepage stability of the natural foundation is constructed;

[0080] Specifically, based on the internal seepage stability data of all soil samples of the target natural foundation after statistical analysis, and based on the critical values ​​of "mean" and "mean-standard deviation", a multi-level indicator threshold evaluation system for the internal seepage stability of the natural foundation is constructed to complete the preliminary classification of the internal seepage stability of the target natural foundation.

[0081] The method for determining the preliminary evaluation results of the internal seepage stability of natural foundation is as follows:

[0082] S31. Calculate each soil sample based on the soil internal permeability evaluation index formula to obtain the corresponding internal permeability stability value. Pre-set evaluation criteria divide the soil internal permeability stability into "stable," "relatively stable," "basically stable," and "unstable" levels, as shown in Table 2. Based on the internal permeability stability values ​​of all soil samples, generate internal permeability stability evaluation results for all soil samples.

[0083] Table 2 Classification of soil internal seepage stability

[0084] category Qualitative description Numerical range Stablize The particles inside the soil are arranged tightly and orderly, and the constraints between particles are strong. SF≥1.2 relatively stable The particles inside the soil are arranged relatively tightly, and the overall structure is relatively complete. 0.9≤SF<1.2 basically stable The internal particle constraint of the soil is relatively weak, and there are pore defects 0.6≤SF<0.9 Unstable The particles inside the soil are loose and have almost no effective restraint SF<0.6

[0085] S32. Summarize and statistically analyze the internal seepage stability evaluation results of the soil samples according to step S31, calculate their mean μ and standard deviation σ, and construct a multi-level index threshold system for internal seepage stability of natural foundations based on the critical values ​​of "mean" and "mean-standard deviation", which are divided into "Level I (safe)", "Level II (mild)", "Level III (moderate)", and "Level IV (high risk)", as shown in Table 3;

[0086] Table 3 Multi-level index threshold system for internal seepage stability of natural foundation

[0087]

[0088] The mean value of the internal seepage stability in step S32 represents the average level of the internal seepage stability of all soil samples in the natural foundation, and the standard deviation measures the degree of dispersion of the internal seepage stability. The formula is:

[0089]

[0090] Among them, the larger the standard deviation σ is, the higher the degree of dispersion of the internal seepage stability of the soil sample is, which in turn reflects that the spatial distribution of the internal seepage stability of the foundation is more uneven.

[0091] S33. Preliminarily determine the internal seepage stability of the target foundation based on the number and proportion of soil samples of different evaluation levels, as well as the trend and dispersion of the internal seepage stability of the soil samples as reflected by the mean and standard deviation;

[0092] S4: Considering different confidence intervals and assurance rates, uncertainty analysis is performed on the internal seepage stability classification results of the target foundation to achieve a probabilistic assessment of the internal seepage stability of the natural foundation.

[0093] Specifically, based on the construction of a multi-level indicator threshold system for the internal seepage stability of natural foundations, appropriate confidence intervals (such as 90%, 95%, 99%) and guarantee rates are selected, and uncertainty analysis is performed on the internal seepage stability grading results of the target foundation to achieve a probabilistic assessment of the internal seepage stability of the natural foundation and output the internal seepage stability results of the target natural foundation.

[0094] Figure 3 This is a logical diagram of the internal seepage stability evaluation of a natural foundation according to one embodiment of the present application.

[0095] like Figure 3 As shown, the evaluation target is the internal seepage stability of the natural foundation. By obtaining the soil parameters of the target natural foundation at different positions and depths, data preprocessing is performed, and preliminary results of the soil internal seepage stability are generated through analysis. Then, considering the soil gradation, stacking state and overburden pressure factors, a calculation method for the soil internal seepage stability evaluation index is proposed, and the internal seepage stability of the soil samples in the target foundation area is calculated. Based on the internal seepage stability evaluation results of all soil samples in the target foundation area, the mean and standard deviation of the evaluation index values ​​are statistically analyzed. Considering the "mean" and "mean-standard deviation" critical values, a multi-level indicator threshold system for the internal seepage stability of the natural foundation is constructed, and different confidence intervals and guarantee rates are introduced to carry out a probabilistic evaluation of the target natural foundation, and finally the internal seepage stability result of the target natural foundation is output.

[0096] Example 2

[0097] Based on the same concept as the method for comprehensive evaluation of internal seepage stability of a natural foundation in the aforementioned embodiment, the present application further provides a system for comprehensive evaluation of internal seepage stability of a natural foundation, the system comprising:

[0098] The data acquisition module is used to obtain the parameters of the target natural foundation soil, perform preprocessing, and generate preliminary results of the internal seepage stability of the soil sample;

[0099] The data calculation module is used to comprehensively consider soil gradation, accumulation state and overburden pressure factors, propose a calculation method for soil internal seepage stability evaluation index, and calculate the internal seepage stability of collected soil samples;

[0100] Comprehensive evaluation module, used to statistically analyze the internal seepage stability data of all soil samples and determine the internal seepage stability of natural foundations through the construction of a multi-level index threshold system;

[0101] The above-mentioned evaluation system in this application can effectively realize the comprehensive evaluation method of internal seepage stability of natural foundations. The technical effects that can be achieved are as described in the above-mentioned embodiments and will not be repeated here.

[0102] Furthermore, the comprehensive evaluation module includes, for example Figure 4 As shown:

[0103] The data statistics calculation unit is responsible for calculating the mean and standard deviation of the relevant data of the internal seepage stability of all soil samples;

[0104] The threshold system construction unit constructs a multi-level index threshold system for internal seepage stability of natural foundations based on the mean and standard deviation obtained by the data statistics calculation unit, and makes a preliminary assessment of the internal seepage stability of natural foundations;

[0105] The comprehensive probabilistic assessment unit selects appropriate confidence intervals and assurance rates based on the established multi-level index threshold system for internal seepage stability of natural foundations according to the actual project needs, data characteristics, and relevant regulatory requirements. It then conducts uncertainty analysis on the internal seepage stability grading results of the target foundation, thereby realizing a probabilistic assessment of the internal seepage stability of natural foundations.

[0106] Similarly, the above-mentioned optimization schemes for the system can also respectively achieve the corresponding optimization effects of the method in Example 1, which will not be repeated here.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for evaluating the internal seepage stability of a natural foundation, characterized in that: The following steps are involved: S1. Obtain soil parameters at different locations and depths of the target natural foundation, perform preprocessing, and generate preliminary results of the internal seepage stability of the soil sample; S2. Taking into account the soil gradation, accumulation state and overburden pressure factors, a calculation method for evaluating the internal seepage stability index of the soil is proposed, and the internal seepage stability of the soil sample in the target foundation area is calculated; S3. Based on the internal seepage stability evaluation results of all soil samples in the target foundation area, combined with the mean μ and standard deviation σ of the evaluation indicators, and considering the critical values ​​of "mean μ" and "mean μ-standard deviation σ", a multi-level indicator threshold system for internal seepage stability of natural foundations is constructed; S4. Considering different confidence intervals and assurance rates, uncertainty analysis is performed on the internal seepage stability classification results of the target foundation to achieve a probabilistic assessment of the internal seepage stability of the natural foundation.

2. The method according to claim 1, characterized in that The soil parameters and factors include particle size parameters, porosity, accumulation state and overburden pressure.

3. The method according to claim 1, characterized in that The pretreatment includes: S1. Use sieving method or laser particle size analyzer method to carry out particle size distribution analysis, obtain soil gradation curve, and generate preliminary results of soil sample internal permeability stability; S2. Analyze the soil accumulation state through relative density Dr, D r =(e max -e) / (e max -e min ), where e is the natural porosity; e max is the porosity ratio of the soil in the loosest state; e min is the void ratio of the soil in its most dense state; S3. Calculate the overburden pressure of the soil, which is determined by the overburden pressure coefficient. The formula is: σ * =σ v / (γ′H max ), where σv is the overburden pressure at the depth of the soil, Y′ is the effective weight of the soil, and Hmax is the reference depth.

4. The method according to claim 3, characterized in that When obtaining soil overburden pressure data at different depths, if only a small number of depth points are missing, the data can be filled in using linear interpolation. Based on the overburden pressure values ​​at known depth points, linear calculations are performed according to the depth ratio to obtain the estimated overburden pressure values ​​at the missing points.

5. The method according to claim 1, wherein The calculation formula of the evaluation index is: SF=SF b ·SF p ·SF s Among them, SF b is a grading item, which is the basic item of evaluation index; SF p is the accumulation state correction term, which corrects the influence of soil accumulation structure differences; SF s is the overburden pressure suppression term, which characterizes the stress suppression effect of the overburden pressure on the particles.

6. The method according to claim 5, characterized in that The basic item SF in the evaluation index b The formula is: SF b =(H / F) min Where H is the mass percentage corresponding to any particle size d; F is the mass percentage corresponding to particles with any particle size between d and 4d.

7. The method according to claim 5, characterized in that Determine the accumulation state correction term and overburden pressure suppression term using the following formula: Among them, k1 is the coefficient obtained by fitting, which is used to adjust the influence of soil accumulation state on internal seepage stability; D r is the relative density, which characterizes the soil accumulation state; D r0 is the reference value of relative density; k2 is the coefficient used to adjust the influence of overburden pressure; f c is the fine particle content; σ * is the overburden pressure coefficient.

8. The method according to claim 1, characterized in that The multi-level indicator threshold system for internal seepage stability of natural foundations includes: dividing the internal seepage stability of soil into "stable", "relatively stable", "basic stable", and "unstable" levels; and constructing a multi-level indicator threshold system of "Level I (safe)", "Level II (mild)", "Level III (moderate)", and "Level IV (high risk)" based on the mean μ and standard deviation σ.

9. A natural foundation internal seepage stability evaluation system, characterized in that: include: The data acquisition module is used to obtain soil parameters in the target foundation area, perform preprocessing, and generate preliminary results on the internal seepage stability of the soil sample; A data calculation module is used to comprehensively consider soil gradation, accumulation state and overburden pressure factors, propose a calculation method for soil internal seepage stability evaluation index, calculate the internal seepage stability of the soil sample in the target foundation area, and output the soil sample internal seepage stability result; The comprehensive evaluation module is used to generate the internal seepage stability evaluation results of all soil samples in the target foundation area based on the soil internal seepage stability calculation model, and obtain the comprehensive evaluation results of the internal seepage stability of the target natural foundation through statistical analysis.

10. The system according to claim 9, characterized in that The comprehensive evaluation module includes: A data statistics calculation unit, used to calculate the mean and standard deviation of the internal seepage stability of all soil samples of the natural foundation; A threshold system construction unit is used to construct a multi-level index threshold system for internal seepage stability of natural foundations based on mean and standard deviation; The comprehensive probability assessment unit is used to select appropriate confidence intervals and assurance rates to conduct a probabilistic assessment of the internal seepage stability of natural foundations.

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