Method and system for identifying soil particle size distribution characteristics of soil skeleton deformation induced by underground erosion

Abstract

The application discloses a method and system for judging the particle size distribution characteristics of soil body capable of inducing soil skeleton deformation caused by incipient corrosion, and applies to the technical field of hydraulic geotechnical engineering. f And a coarse-grained particle characteristic particle size ratio D' 15 / d' 85 characterize the particle size distribution characteristics of the internal unstable soil body; S2, determining a coarse-fine particle boundary particle size D cr according to the particle size distribution curve of the internal unstable soil body; S3, determining a fine particle content F f and the coarse-grained particle characteristic particle size ratio D' 15 / d' 85 according to the coarse-fine particle boundary particle size D cr and the particle size distribution curve of the internal unstable soil body; S4, plotting the corresponding F f and D' 15 / d' 85 of the internal unstable soil body on a D' 15 / d' 85 -F f scatter diagram, and evaluating whether the soil body can induce obvious skeleton deformation after incipient corrosion according to the position of the scatter diagram. The application can evaluate whether the internal unstable soil body can induce obvious skeleton deformation after incipient corrosion, and provides a theoretical basis for scientifically evaluating the incipient corrosion hazard and the design of dam body and dam foundation seepage prevention.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydraulic geotechnical, more particularly to a method and system for identifying the particle size distribution characteristics of soil that induces soil skeleton deformation caused by potential erosion. BACKGROUND

[0002] Potential erosion refers to the phenomenon that fine particles in an internal unstable soil are carried by seepage and migrate and lose in the skeleton pores formed by coarse particles, gradually forming a phenomenon of local hollowing and local filling in the foundation. The so-called internal unstable soil refers to a soil in which the characteristic particle size of coarse and fine materials that make up the soil does not meet the self-filtering condition, and the fine materials can move freely in the pores formed by the coarse materials. Generally speaking, the intermittent graded soil and the wide graded soil with a gentle tail of the grading curve are typical internal unstable soils. After potential erosion occurs, with the continuous loss of a large number of fine particles, the local hollowed area may induce significant skeleton deformation, and further induce uneven settlement of the foundation, which may eventually damage the impervious system such as the core wall or the cutoff wall of the dam, and threaten the safety of the dam. The potential erosion that occurred in the Tarbela Dam in Pakistan caused 362 collapse pits in the upstream impervious blanket, among which the largest pit had a diameter of 12.2 m and a depth of 4.0 m, and the downstream seepage flow rate was as high as 9.4 m 3 / s, and the reservoir was forced to be emptied; the potential erosion that occurred in the ice-marginal soil core wall of the WAC Bennett Dam in Canada caused two collapse pits in the upstream abutment, and the core wall of the dam was locally severely damaged. Therefore, it is of great theoretical significance and practical value to explore whether potential erosion can induce significant soil skeleton deformation after it occurs, for the scientific evaluation of the impact of potential erosion and the protection of dam safety.

[0003] According to existing literature reports, some internal unstable soils will deform significantly after a large amount of fine particles are lost, while some internal unstable soils do not deform significantly during the entire process of fine particle loss. For example, Chang and Zhang conducted a potential erosion test study on intermittent graded soil under different stress states, and found that the outflow of a large amount of fine particles would induce significant deformation of the skeleton. Moffat et al. studied the potential erosion process of four wide graded soils taken from the WAC Bennett Dam, and found that two of the soils did not deform at all during the entire process of fine particle outflow, while the other two soils deformed significantly. It can be seen that whether potential erosion can induce significant soil skeleton deformation after it occurs is closely related to the particle size distribution of the internal unstable soil.

[0004] Current research on potential erosion focuses on "what kind of particle size distribution characteristics of soil is internal unstable soil", and pays little attention to "what kind of particle size distribution characteristics of internal unstable soil can induce significant skeleton deformation after potential erosion occurs". For example, Kezdi (1979) proposed that when the ratio of the particle size of the coarse particles to the particle size of the fine particles D' 15 / d' 85>4.0, the soil body is an internally unstable soil body, wherein D' 15 represents the particle size corresponding to the cumulative mass fraction of 15% of coarse particles, d' 85 represents the particle size corresponding to the cumulative mass fraction of 85% of fine particles. Kenney and Lau (1985) established a method for discriminating the internal stability of soil bodies based on the H / F ratio of each point on the particle size distribution curve, wherein F is the cumulative mass fraction corresponding to any particle size d in the soil body, and H is the difference between the cumulative mass fractions of d and 4d. Burenkova et al. (1993), Wan and Fell (2008) established different methods for discriminating the internal stability of soil bodies according to the characteristic particle sizes d 15 , d 60 , and d 90 of the internally unstable soil bodies of the intermittently graded and widely graded sandy soil. Li and Fannin (2008) further established a method for discriminating the internal stability of soil bodies by dividing the range of the mass fraction F corresponding to any particle size on the particle size distribution curve and using the H / F ratio of the particle size distribution curve. Inndraratna et al. (2011) compared the ratio of the characteristic pore diameter D c35 corresponding to the cumulative mass fraction of 35% of coarse particles and the representative particle size df 85 corresponding to the cumulative mass fraction of 85% of fine particles to discriminate the internal stability of soil bodies. Chang and Zhang (2013) combined the two indicators of the content of fine particles with particle sizes less than 0.063 mm in the particle size distribution of soil bodies and the ratio of H / F to establish a method for discriminating the internal stability of soil bodies. However, the existing researches cannot answer the question of what kind of particle size distribution characteristics of the internally unstable soil bodies will induce significant deformation of the soil skeleton after the continuous loss of fine particles, which is related to the safety of hydropower projects.

[0005] Therefore, it is an urgent problem for those skilled in the art to propose a method and system for discriminating the particle size distribution characteristics of soil bodies that induce deformation of the soil skeleton due to potential erosion to solve the problems in the prior art. SUMMARY

[0006] Therefore, the present application provides a method and system for discriminating the particle size distribution characteristics of soil bodies that induce deformation of the soil skeleton due to potential erosion, which can predict whether the internally unstable soil bodies will induce significant uneven settlement of the dam foundation after potential erosion and scientifically evaluate the hazards after potential erosion, thereby providing an important theoretical basis for the design of the dam foundation seepage prevention and the safety evaluation of the dam of a hydropower project.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] The method for discriminating the particle size distribution characteristics of soil bodies that induce deformation of the soil skeleton due to potential erosion comprises the following steps:

[0009] S1. Establishing the criterion of obvious deformation of soil skeleton, selecting the fine particle content F f and the ratio of coarse particle characteristic size D′ 15 / d′ 85 to represent the characteristics of the internal unstable soil particle gradation;

[0010] S2. According to the particle gradation curve of the internal unstable soil, determining the coarse-fine particle boundary size D cr ;

[0011] S3. According to the coarse-fine particle boundary size D cr and the particle gradation curve of the unstable soil, determining the fine particle content F f and the ratio of coarse particle characteristic size D′ 15 / d′ 85 ;

[0012] S4. Plotting the corresponding F f and D′ 15 / d′ 85 of the internal unstable soil on the D′ 15 / d′ 85 -F f scatter diagram, and evaluating whether the soil can induce obvious skeleton deformation after the occurrence of potential erosion according to the position of the scatter.

[0013] Optionally, the criterion of obvious deformation of soil skeleton in S1 is specifically: selecting the volume strain as the evaluation index of the obvious deformation of soil skeleton, and taking the volume strain of the induced sample reaching or exceeding 1% during the particle loss process as the criterion of the obvious deformation of soil skeleton.

[0014] Optionally, the specific method of determining the coarse-fine particle boundary size D cr in S2 is: when F≤40%, for the internal unstable soil with wide gradation, the particle size corresponding to (H / F) min is the boundary size D cr ; for the internal unstable soil with intermittent gradation, the minimum particle size of the platform part of the gradation curve is the boundary size D cr .

[0015] Optionally, F is the mass percentage content corresponding to any particle size d in the gradation curve of the internal unstable soil, and H is the difference between the mass percentage contents of particle size d and 4d in the gradation curve of the internal unstable soil.

[0016] Optionally, the specific method of determining F f and D′ 15 / d′ 85 in S3 is:

[0017] S31. The cumulative mass percentage content corresponding to D cr is the fine particle content Ff ;

[0018] S32. When the cumulative mass percentage content is 0.85F f , the corresponding particle size is d' 85 , when the cumulative mass percentage content is 15+0.85F f , the corresponding particle size is D' 15 ;

[0019] S33. The particle size corresponding to the two percentage contents in S32 is divided to obtain D' 15 / d' 85 .

[0020] The soil particle size grading feature discrimination system for inducing soil skeleton deformation by hidden corrosion applies the soil particle size grading feature discrimination method for inducing soil skeleton deformation by hidden corrosion, and comprises, in sequence, a skeleton deformation criterion establishing module, a limit particle size determining module, a F f and D' 15 / d' 85 determining module, and a skeleton deformation determining module; wherein,

[0021] The skeleton deformation criterion establishing module establishes a criterion for obvious deformation of the soil skeleton, selects the fine particle content F f and the coarse particle characteristic particle size ratio D' 15 / d' 85 to represent the internal unstable soil particle size grading feature;

[0022] The limit particle size determining module determines the coarse and fine particle limit particle size D cr according to the particle size grading curve of the internal unstable soil;

[0023] The F f and D' 15 / d' 85 determining module determines the fine particle content F cr and the coarse particle characteristic particle size ratio D' f / d' 15 according to the coarse and fine particle limit particle size D 85 ;

[0024] The skeleton deformation determining module plots the F 15 and D' 85 / d' f of the internal unstable soil on the D' f / d' 15 -F 85 scatter diagram, and evaluates whether the soil can induce obvious skeleton deformation after hidden corrosion according to the position of the scatter points.

[0025] Via the technical solutions, compared with the prior art, the application provides a soil particle grading feature discrimination method and system for soil skeleton deformation induced by latent corrosion, which has the beneficial effects that: it can preliminarily evaluate whether any internal unstable soil can induce obvious soil skeleton deformation after latent corrosion, thereby providing an important theoretical basis for scientifically evaluating the hazard after latent corrosion, for dam body and dam foundation seepage prevention design, and dam safety evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only the embodiments of the application, and for those skilled in the art, other drawings can be obtained without creative labor based on the provided drawings.

[0027] Figure 1 The flow chart of the soil particle grading feature discrimination method for soil skeleton deformation induced by latent corrosion provided by the application;

[0028] Figure 2 The structure diagram of the soil particle grading feature discrimination system for soil skeleton deformation induced by latent corrosion provided by the application;

[0029] Figure 3 The determination diagram of the wide grading internal unstable soil D cr provided by the application;

[0030] Figure 4 The determination diagram of the intermittent grading internal unstable soil D cr provided by the application;

[0031] Figure 5 The determination method diagram of the wide grading internal unstable soil D' 15 / d' 85 provided by the application;

[0032] Figure 6 The determination method diagram of the intermittent grading internal unstable soil D' 15 / d' 85 provided by the application;

[0033] Figure 7 The scatter diagram of the internal unstable soil D' 15 / d' 85 and F f provided by the application. DETAILED DESCRIPTION

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] See Figure 1 As shown, this invention discloses a method for identifying soil particle size distribution characteristics in soil skeleton deformation induced by erosion, comprising the following steps:

[0036] S1. Establish criteria for significant deformation of the soil skeleton, selecting the fine particle content F f The ratio of coarse particle characteristic size D′ 15 / d′ 85 Characterizes the particle size distribution of internally unstable soil masses;

[0037] S2. Determine the boundary size D between coarse and fine particles based on the particle size distribution curve of the internally unstable soil. cr ;

[0038] S3. Based on the boundary particle size D of coarse and fine particles cr Particle size distribution curves of unstable soils were used to determine the fine particle content F. f The ratio of coarse particle characteristic size D′ 15 / d′ 85 ;

[0039] S4. At D′ 15 / d′ 85 -F f Plotting the F values ​​corresponding to internally unstable soil on a scatter plot f and D′ 15 / d′ 85 The location of the scatter points is used to evaluate whether the soil erosion can induce significant skeletal deformation.

[0040] Optionally, the criterion for establishing significant deformation of the soil skeleton in S1 is as follows: volumetric strain is selected as the evaluation index for significant deformation of the soil skeleton, and the volumetric strain of the sample induced during particle loss reaches or exceeds 1% as the criterion for significant deformation of the soil skeleton.

[0041] Furthermore, the boundary particle size D between coarse and fine particles is determined in S2. cr The specific method is as follows: See Figure 3 As shown, when F ≤ 40%, for wide-gradation internally unstable soils, (H / F) min The corresponding particle size is the boundary particle size D. cr See also Figure 3As shown, for the discontinuous graded soil, the minimum particle size of the platform part of the grading curve is the limit particle size D cr , see Figure 4 .

[0042] Further, F is the mass percentage content corresponding to any particle size d in the internal unstable soil body grading curve, and H is the difference between the mass percentage contents of particle sizes d and 4d in the internal unstable soil body grading curve.

[0043] Further, see Figure 5 and Figure 6 , the specific method for determining F f and D′ 15 / d′ 85 in S3 is:

[0044] S31. D cr corresponding to the cumulative mass percentage content, that is, the fine particle content F f .

[0045] S32. When the cumulative mass percentage content is 0.85F f , the corresponding particle size is d′ 85 , and when the cumulative mass percentage content is 15+0.85F f , the corresponding particle size is D′ 15 .

[0046] S33. The particle sizes corresponding to the two percentage contents in S32 are divided to obtain D′ 15 / d′ 85 .

[0047] Corresponding to the method described in Figure 1 , the present application also provides a soil particle grading feature discrimination system for latent corrosion-induced soil skeleton deformation, which is used for specific implementation of the method in Figure 1 , and a structure diagram thereof is shown in Figure 2 , which comprises, in sequence, a skeleton deformation criterion establishing module, a limit particle size determining module, a F f and D′ 15 / d′ 85 module, and a skeleton deformation determining module; wherein,

[0048] The skeleton deformation criterion establishing module: establishes the criterion for the occurrence of obvious deformation of the soil skeleton, selects the fine particle content F f and the coarse particle characteristic particle size ratio D′ 15 / d′ 85 to represent the internal unstable soil body particle grading feature;

[0049] The limit particle size determining module: determines the coarse and fine particle limit particle size D according to the particle grading curve of the internal unstable soil body.cr ;

[0050] Determine F f and D′ 15 / d′ 85 Module: Based on the boundary particle size D between coarse and fine particles cr Particle size distribution curves of unstable soils were used to determine the fine particle content F. f The ratio of coarse particle characteristic size D′ 15 / d′ 85 ;

[0051] Determine the skeleton deformation module: at D′ 15 / d′ 85 -F f Plotting the F values ​​corresponding to internally unstable soil on a scatter plot f and D′ 15 / d′ 85 The location of the scatter points is used to evaluate whether the soil erosion can induce significant skeletal deformation.

[0052] Specifically, to establish criteria for determining whether significant deformation of the soil skeleton has occurred, the applicant compiled a total of 65 burrowing test results from various literature sources, as shown in Table 1. The "Whether Significant Skeletal Deformation Occurred" column in the table presents different scholars' judgments on whether significant deformation of the soil skeleton has occurred. The table lists two types of permeability tests: unconfined triaxial permeability tests, which provide the axial strain and volumetric strain monitoring results of the samples; and confined tests, which provide the axial strain of the samples, in which case the axial strain equals the volumetric strain. Slangen and Fannin (2017) found that, compared to axial strain, volumetric strain better reflects the overall skeleton deformation of the sample. For example, for sample 6.5GB35-100 in Table 1, the axial strain and volumetric strain induced by the loss of fine particles were 0.04% and 1.68%, respectively. Similar situations occurred with three other samples: 6.0GB35-100, 6.0GB35-100(R), and 6.5GB35-50. The experimental results of Prasomsri and Takahashi (2020) also illustrate this point. Considering the experimental results in Table 1, volumetric strain was chosen as the evaluation index for significant deformation of the soil skeleton. From the extensive experimental data in Table 1, it can be seen that when the cumulative volumetric strain induced during the entire process of fine particle loss is greater than or equal to 1%, most studies consider that significant skeletal deformation of the soil has occurred. Therefore, the criterion for significant deformation of the soil skeleton is that the volumetric strain induced in the sample during particle loss reaches or exceeds 1%. In other words, if the cumulative volumetric strain of the sample reaches or exceeds 1% during the entire process of burrowing, it indicates that significant deformation of the soil skeleton has occurred.

[0053] Table 1: Statistics of the results of erosion tests in some relevant literature

[0054]

[0055]

[0056]

[0057]

[0058] The existing literature published 88 kinds of internal unstable soil potential erosion test or numerical simulation results, including 129 groups of discontinuous graded soil potential erosion data, 65 groups of wide graded soil potential erosion results, see Table 2. Through repeated analysis and research, finally determine the selection: fine particle content F f And the ratio of coarse and fine particle characteristic particle size D' 15 / d' 85 Two important parameters can well characterize the internal unstable soil particle size distribution characteristics, wherein D' 15 Refers to the cumulative mass fraction of 15% of the coarse particles in the internal unstable soil, d' 85 Refers to the cumulative mass fraction of 85% of the fine particles in the internal unstable soil. For any kind of internal unstable soil particle size distribution curve, to determine F f And D' 15 / d' 85 , need to first determine the coarse and fine limit particle size D cr , the particle size of the soil greater than D cr , that is, the coarse particles, the particle size less than or equal to D cr , that is, the fine particles.

[0059] Table 2: Statistics of part of the test results in the existing literature

[0060]

[0061]

[0062]

[0063]

[0064] Using the data in Table 2, according to the determination method of fine particle content F f And D' 15 / d' 85 , determine the F f And D' 15 / d' 85Based on the criterion of significant deformation of the soil skeleton, the evaluation of whether significant skeleton deformation occurred in the samples after burial was carried out, as shown in Table 2. D′ values ​​for each internally unstable soil mass were plotted using Table 2. 15 / d′ 85 With F f Scatter plot.

[0065] See Figure 7 As shown, the scatter plot can be divided into four regions: ① to ④. These four regions have different particle size distribution characteristics, which also determine whether significant skeletal deformation can be induced after undercutting. The fine particle content F in region ①... f Sufficiently high, between 35% and 40%, the pores formed by coarse particles are basically filled by fine particles. In this case, coarse and fine particles share the external load. Therefore, the unstable soil in zone ① will experience significant skeletal deformation after erosion. The fine particle content F in zone ④... f Too little, less than 22%, means that the pores formed by coarse particles have a large amount of space that is not yet filled by fine particles. In this case, fine particles rarely participate in force transmission. Therefore, the unstable soil in zone ④ will not induce significant skeletal deformation after erosion. The fine particle content F in zones ② and ③ is also low. f Moderate, between 22% and 35%, at this point, F f and D′ 15 / d′ 85 The relative relationship between the two parameters determines the degree to which pores are filled with fine particles and the ratio of stress distribution between coarse and fine materials within the soil, and also determines whether skeletal deformation can be induced after undercutting occurs. For example, F f When = 22%, D′ 15 / d′ 85 Between 4 and 7 o'clock, D′ 15 / d′ 85 With F f The corresponding point falls in region ②, where the pores are basically filled with fine particles. The coarse and fine materials share the external load, and undercutting will induce skeleton deformation; while when D′ 15 / d′ 85 When it is greater than 7, D′ 15 / d′ 85 With F f The corresponding point falls in zone ③. At this time, there is still a lot of space in the pores that has not been filled. Fine particles rarely participate in force transmission, and no obvious skeletal deformation will be induced after the undercut occurs.

[0066] The greatest innovation of this application lies in: (1) proposing a criterion for soil skeleton deformation, using the volumetric strain of the sample induced during particle loss reaching or exceeding 1% as the criterion for significant deformation of the soil skeleton; (2) scientifically determining the fine particle content F, a parameter characterizing the particle gradation characteristics of internally unstable soil. fD' = D / d 15 D' = D / d 85 (3) Based on (1) and (2), and combined with the data in Table 2, the scatter diagram for discrimination is determined, see Fig. 3. Figure 7

[0067] The various embodiments described in the specification are presented for the purpose of illustration and description. Each of the embodiments focuses on the differences from other embodiments, and the same or similar parts among the embodiments can be mutually referred to. For the modules disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part.

[0068] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.​

Claims

1. A method for identifying soil particle size distribution characteristics in soil skeleton deformation induced by erosion, characterized in that, Includes the following steps: S1. Establish criteria for significant deformation of the soil skeleton, selecting the fine particle content F f The ratio of coarse particle characteristic size D′ 15 / d′ 85 Characterizes the particle size distribution of internally unstable soil masses; S2. Determine the boundary size D between coarse and fine particles based on the particle size distribution curve of the internally unstable soil. cr ; S3. Based on the boundary particle size D of coarse and fine particles cr Particle size distribution curves of unstable soils were used to determine the fine particle content F. f The ratio of coarse particle characteristic size D′ 15 / d′ 85 ; S4. At D′ 15 / d′ 85 -F f Plotting the F values ​​corresponding to internally unstable soil on a scatter plot f and D′ 15 / d′ 85 And based on the location of the scatter points, evaluate whether the soil erosion can induce significant skeletal deformation after it occurs; In S2, the boundary particle size D between coarse and fine particles is determined. cr The specific method is as follows: When F≤40%, for wide-gradation internally unstable soils, (H / F) min The corresponding particle size is the boundary particle size D. cr For discontinuously graded soils, the minimum particle size of the plateau portion of the gradation curve is the limiting particle size D. cr ; F represents the mass percentage of any particle size d in the gradation curve of internally unstable soil, and H represents the difference in mass percentage between particle size d and 4d in the gradation curve of internally unstable soil. F is determined in S3 f and D′ 15 / d′ 85 The specific method is as follows: S31.D cr The corresponding cumulative mass percentage content is the fine particle content F. f ; S32. When the cumulative mass percentage content is 0.85F f When the particle size is d′, the corresponding particle size is d′. 85 When the cumulative mass percentage content is 15 + 0.85F f When the particle size is D′, the corresponding particle size is D′. 15 ; Dividing the particle size corresponding to the two percentage contents in S33 and S32 yields D′. 15 / d′ 85 ; The scatter plot is divided into regions ① to ④. The fine particle content F in region ① is... f Between 35% and 40%, the fine particulate content F in zone ④ f Less than 22%, fine particulate content F in zones ② and ③ f Between 22% and 35%, F f and D′ 15 / d′ 85 The relative relationship between the two parameters determines whether skeletal deformation can be induced after erosion occurs.

2. The method for determining soil particle size distribution characteristics in erosion-induced soil skeleton deformation according to claim 1, characterized in that, The specific criteria for establishing significant deformation of the soil skeleton in S1 are as follows: volumetric strain is selected as the evaluation index for significant deformation of the soil skeleton, and the volumetric strain of the sample induced during particle loss reaches or exceeds 1% as the criterion for significant deformation of the soil skeleton.

3. A soil particle size distribution characteristic discrimination system for soil skeleton deformation induced by erosion, characterized in that... The method for determining soil particle size distribution characteristics in the context of erosion-induced soil skeleton deformation according to any one of claims 1-2 includes, in sequence, a module for establishing skeleton deformation criteria, a module for determining the limit particle size, and a module for determining F. f and D′ 15 / d′ 85 Module, determining the skeleton deformation module; among which, Establish a soil skeleton deformation criterion module: Establish criteria for significant deformation of the soil skeleton, selecting the fine particle content F f The ratio of coarse particle characteristic size D′ 15 / d′ 85 Characterizes the particle size distribution of internally unstable soil masses; The module for determining the limiting particle size: Based on the particle size distribution curve of the internally unstable soil, the limiting particle size D of coarse and fine particles is determined. cr ; Determine F f and D′ 15 / d′ 85 Module: Based on the boundary particle size D between coarse and fine particles cr Particle size distribution curves of unstable soils were used to determine the fine particle content F. f The ratio of coarse particle characteristic size D′ 15 / d′ 85 ; Determine the skeleton deformation module: at D′ 15 / d′ 85 -F f Plotting the F values ​​corresponding to internally unstable soil on a scatter plot f and D′ 15 / d′ 85 The location of the scatter points is used to evaluate whether the soil erosion can induce significant skeletal deformation.

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