Slope stability evaluation model and method considering vegetation influence

Abstract

The invention provides a slope stability evaluation model construction method considering vegetation influence. The method comprises the following steps: determining vegetation classification; acquiring root morphology of different types of vegetation, and calculating root tensile strength and soil shear strength increment under the action of the root according to the root morphology; obtaining growth speeds of different types of vegetation, and calculating root enhancement factors, soil reinforcement efficiency and vegetation growth cycle influence factors according to the growth speeds; and constructing a slope stability evaluation model according to the root tensile strength, the soil shear strength increment under the action of the root, the root enhancement factor, the soil reinforcement efficiency and the vegetation growth cycle influence factor. By using the model, the slope stability is evaluated by considering the vegetation influence, so that optimization of vegetation selection and configuration is facilitated, the slope protection effect is improved, and the engineering cost is reduced; quantification and refinement of slope stability evaluation can be realized, and a reliable basis is provided for engineering design and construction.

Description

Technical Field

[0001] The present invention relates to the technical field of evaluating slope stability, and in particular to a slope stability evaluation model and method taking into account the influence of vegetation. Background Art

[0002] At present, slope stability assessment focuses on the properties and geometric form of rock and soil, but seriously lacks consideration of the impact of different vegetation on the slope surface. Traditional assessment methods only regard vegetation as a surface cover, while ignoring the complex interaction between vegetation roots and soil, resulting in the inability to accurately assess the effect of vegetation slope protection and select appropriate vegetation types for slope protection in actual projects.

[0003] Different types of vegetation have different root morphological characteristics and growth rates, which have a direct impact on the reinforcement of the soil. However, the existing assessment system lacks accurate quantitative methods and cannot adapt to slopes covered by different vegetation types. As a result, slope protection projects cannot scientifically assess the stability of the slope and formulate protection plans based on the influence of vegetation types. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a slope stability assessment model and method taking into account the influence of vegetation to solve the technical problems existing in the prior art: the existing assessment system lacks an accurate quantitative method and cannot adapt to slopes covered with different vegetation types, resulting in the inability of slope protection projects to scientifically assess the stability of the slope and formulate protection plans based on the influence of vegetation types.

[0005] The technical solution adopted by the present invention is as follows:

[0006] In the first aspect, a method for constructing a slope stability assessment model considering the influence of vegetation is provided, including:

[0007] Determine vegetation classification;

[0008] Obtain the root morphology of different types of vegetation, and calculate the root tensile strength and the soil shear strength increment under the action of the root system based on the root morphology;

[0009] Obtain the growth rates of different types of vegetation, and calculate the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors based on the growth rates;

[0010] A slope stability assessment model was constructed based on the root tensile strength and the increment of soil shear strength under the action of the root system, as well as the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors.

[0011] Furthermore, the vegetation classification is determined based on the vegetation type and growth habit.

[0012] Furthermore, the root morphology includes: average root length, average root diameter, root density and root distribution morphology ratio.

[0013] Furthermore, the root tensile strength is calculated based on the root morphology, including:

[0014] Obtain the breaking force of root samples measured in the tensile strength test;

[0015] The root cross-sectional area was calculated based on the average root diameter;

[0016] The root tensile strength was calculated by dividing the breaking force by the root cross-sectional area.

[0017] Furthermore, the root shear strength is calculated based on the root morphology, including:

[0018] Multiply the root-soil friction coefficient, root tensile strength and root density to obtain the soil shear strength increment under the action of the root system.

[0019] Furthermore, the growth rates of different types of vegetation are obtained, including: measuring the growth amount of vegetation per unit time, wherein the growth amount includes an increase in root length or an increase in biomass.

[0020] Furthermore, a slope stability assessment model is constructed based on the root tensile strength and the soil shear strength increment under the action of the root system, as well as the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors, including:

[0021] The root enhancement factor is introduced to consider the influence of roots on soil cohesion and internal friction angle, and the Mohr-Coulomb model is modified.

[0022] Based on the modified Mohr-Coulomb model, the slope safety factor with the influence of vegetation is calculated.

[0023] Furthermore, the slope stability assessment model considering the influence of vegetation is calculated as follows:

[0024]

[0025] In the formula, F st It represents the comprehensive evaluation value of slope stability under the influence of different types of vegetation;

[0026] F si represents the contribution of the i-th vegetation type to the slope stability, which is obtained through experimental observation and numerical simulation, and reflects the ability of this vegetation type in enhancing the slope stability; w i It represents the weight coefficient of the i-th vegetation type, reflecting the importance and influence of the vegetation type in the slope vegetation coverage, which is determined by the distribution density, growth status and root type of the vegetation; i represents the vegetation type; n represents the total number of vegetation types;

[0027] D rj represents the length of the jth root, σ tj represents the tensile strength of the jth root, A rj represents the cross-sectional area of ​​the jth root system, j represents the root system of a certain vegetation type; m represents the total number of roots of a certain vegetation type;

[0028] ρ r is the root density; P hi and P vi They represent the horizontal root ratio and vertical root ratio of the kth vegetation type, respectively; n represents the total number of vegetation types;

[0029] Δτ is the increment of the root system’s shear strength to the soil, σ t-avg is the average tensile strength of the root system;

[0030] c is soil cohesion, η is root distribution efficiency factor, D avg is the average root diameter;

[0031] E root is the root enhancement factor, E s is the soil reinforcement efficiency under the influence of vegetation, F c is the factor affecting the vegetation growth cycle;

[0032] k1, k2, k3, k4, and k8 are weight coefficients, which are determined by fitting experimental data.

[0033] In a second aspect, a slope stability assessment model considering the influence of vegetation is provided, which is constructed using the slope stability assessment model construction method considering the influence of vegetation provided in the first aspect.

[0034] On the third aspect, a slope stability assessment method is provided, which takes into account the influence of vegetation on the slope and uses the slope stability assessment model provided by the second aspect to assess the slope stability.

[0035] It can be seen from the above technical solution that the beneficial technical effects of the present invention are as follows:

[0036] 1. Based on the soil-fixing effect of different types of vegetation, analyzing the relationship between vegetation root morphology, growth rate and slope stability will help optimize vegetation selection and configuration, improve slope protection effects and reduce project costs.

[0037] 2. Constructing a slope stability assessment method that takes into account the influence of vegetation can achieve quantification and refinement of slope stability assessment and provide a reliable basis for engineering design and construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0039] Figure 1 This is a flow chart of a method for constructing a slope stability assessment model according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0041] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0042] Example

[0043] This embodiment provides a method for constructing a slope stability assessment model taking into account the influence of vegetation. Figure 1 As shown, the following steps are included:

[0044] Step 1: Determine vegetation classification

[0045] When determining vegetation classification, it is classified according to vegetation type (such as herbaceous plants, shrubs, trees, etc.) and growth habits (such as shallow root type, deep root type, fibrous root type, etc.). The classification standards are based on the vegetation classification system or the "Chinese Vegetation" classification standards.

[0046] Step 2: Obtain the root morphology of different types of vegetation, and calculate the root tensile strength and root shear strength based on the root morphology

[0047] For different types of vegetation, the parameters of the slope stability assessment model constructed in the subsequent steps are different. In a specific implementation method, when measuring the root morphology of different types of vegetation, representative vegetation sample points are selected, and their roots are excavated and sampled. The excavation process should try to maintain the integrity of the root system to avoid root damage. For larger root systems, the segmented excavation method is used, and finally the collected root samples are measured using a measuring tool.

[0048] For root morphology, the measured parameters include: average root length, average root diameter, root density and root distribution morphology ratio.

[0049] Average root length Dr: Directly identify the lengths of multiple vegetation roots through image scanning, and then take the average value.

[0050] Average root diameter D avg The calculation is as follows:

[0051]

[0052] Where, d i is the diameter of each root system, and m is the total number of roots. The average root diameter affects the root tensile strength and soil reinforcement effect.

[0053] Root density ρ r The calculation is as follows:

[0054]

[0055] Where M r is the root mass, V s is the soil volume.

[0056] The root distribution forms include horizontal distribution and vertical distribution. The root distribution form ratio is calculated as follows:

[0057]

[0058] Where, L h is the horizontal root length, L v is the vertical root length; P h is the horizontal root ratio, which affects the horizontal reinforcement effect of the root system on the soil; P v It is the vertical root ratio, which affects the vertical reinforcement effect of the roots on the soil.

[0059] According to the percentage of horizontal distribution and vertical distribution in the root distribution pattern, the root distribution efficiency factor η can be determined. The root distribution efficiency factor can be used to analyze the influence of the proportion of roots on the reinforcement efficiency of the soil under the condition of considering the proportion of horizontal and vertical distribution of vegetation.

[0060] The network structure formed by the vegetation root system in the soil can enhance the shear strength and integrity of the soil, and can play a reinforcing role in the soil. The mechanical properties of the vegetation root system determine its ability to reinforce the slope soil. Its tensile strength can reflect the resistance of the root system under tension, and its shear strength can reflect the resistance of the root system under shear. Therefore, the root mechanical performance analysis includes two aspects: tensile strength test and shear strength analysis, as follows:

[0061] Tensile strength test: use a universal material testing machine to test the tensile strength of the root sample, and calculate the tensile strength performance of the root system according to the following formula:

[0062]

[0063] In the formula, F t is the breaking force; A r is the root cross-sectional area, D avg is the average root diameter, Dr is the average root length; σ t is the tensile strength of the root system, which determines the root system's ability to resist external damage; σ t-avg is the average tensile strength of the root system, which represents the average value of the tensile strength of all roots and is used to evaluate the overall reinforcement capacity of the root system. m is the total number of roots.

[0064] Shear strength analysis: The shear test is used to evaluate the effect of roots on soil shear strength enhancement. The soil shear strength increment under the action of roots is:

[0065] Δτ=μ·σ t ·ρ r (Formula 7)

[0066] Where Δτ is the increment of the root system on the soil shear strength, reflecting the root reinforcement effect; μ is the root-soil friction coefficient, which affects the interaction between the root system and the soil; σ t is the root tensile strength; ρ r is the root density.

[0067] Step 3: Obtain the growth rates of different types of vegetation, and calculate the root enhancement factor, soil reinforcement efficiency, and vegetation growth cycle influencing factor based on the growth rate.

[0068] The vegetation growth rate can be determined by measuring the growth of vegetation per unit time. The growth includes the increase in root length or biomass, etc., and is calculated using the following formula:

[0069]

[0070] Where V g is the vegetation growth rate; ΔL root ΔM is the increase in root length, reflecting the change in root length during the evaluation period, and is a direct reflection of the root system enhancing soil stability. b is the increase in biomass; T g is the growth period or time period for evaluation. ΔL root and ΔM b Both are important indicators for evaluating the growth capacity of vegetation. When used in practice, either of them can be selected based on the principle of convenience. In this embodiment, the biomass of vegetation refers to the total amount of dry weight of vegetation actually surviving per unit area at a certain moment.

[0071] The vegetation growth rate has an important influence on the root-solidification effect. The root enhancement factor is used to analyze this influence, reflecting the relationship between vegetation growth rate and root-enhanced soil stability. The following formula is used for calculation:

[0072]

[0073] In the formula, E root is the root enhancement factor; k5 and α are weight coefficients, which are determined by experimental fitting; V g is the vegetation growth rate; V max The maximum growth rate that vegetation can achieve.

[0074] The growth rate of vegetation also has an important impact on its efficiency in strengthening the soil. The magnitude of this impact is calculated using the following formula based on the vegetation growth rate:

[0075]

[0076] In the formula, E s is the soil reinforcement efficiency under the influence of vegetation; k6 and β are weight coefficients, which are determined by fitting experimental data; V g is the vegetation growth rate; V ref As a reference for growth rate, the average growth rate of a certain standard vegetation can be taken.

[0077] Vegetation growth is also subject to periodic restrictions. Vegetation with a short growth cycle may renew its root system more frequently, thus having a more significant impact on soil structure. The vegetation growth cycle influencing factor is introduced and the following formula is used to quantify this impact.

[0078]

[0079] In the formula, F c is the influencing factor of vegetation growth cycle; k7 is the weight coefficient, which is determined by fitting experimental data; T g is the growth cycle or time period for evaluation; T max is the maximum growth period that vegetation can reach. e is a natural constant.

[0080] Step 4: Construct a slope stability assessment model based on root tensile strength and root shear strength, as well as root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors

[0081] The root morphology of different vegetation types has different soil-fixing effects on the slope, and will also change the cohesion and internal friction angle of the soil. The slope stability assessment model should also consider the impact of soil-fixing on the Mohr-Coulomb model. Therefore, the Mohr-Coulomb model needs to be corrected before being used for slope stability assessment, which is more in line with the actual situation of slope engineering.

[0082] First, the Mohr-Coulomb model was modified. On the basis of the traditional Mohr-Coulomb model, the root enhancement factor was introduced to consider the root system's effect on soil cohesion c and internal friction angle. The soil cohesion c and internal friction angle are calculated according to the following formula

[0083] Δc=Δτ·η (Equation 12)

[0084] Where Δc is the cohesion correction value, Δτ is the increment of the root system on the soil shear strength, and η is the root distribution efficiency factor, which takes into account the influence of root distribution on soil reinforcement efficiency.

[0085]

[0086] In the formula, is the correction value of the internal friction angle; μ is the root-soil friction coefficient; ρ r is the root density; D avg is the average root diameter.

[0087] Based on the modified Mohr-Coulomb model, the slope safety factor F with the influence of vegetation is calculated. si .

[0088]

[0089] In the formula, θ is the slope inclination angle.

[0090] Based on the above analysis, a slope stability evaluation model is constructed that comprehensively considers multiple factors such as root structure characteristics, vegetation growth rate, mechanical properties, soil reinforcement mechanism and slope geological conditions. After integrating various factors through weighted summation and product operations, the calculation formula of the evaluation model is as follows:

[0091]

[0092] In the formula, F st It represents the comprehensive evaluation value of slope stability under the influence of different types of vegetation;

[0093] F si represents the contribution of the i-th vegetation type to the slope stability, which is obtained through experimental observation and numerical simulation, and reflects the ability of this vegetation type in enhancing the slope stability; w i It represents the weight coefficient of the i-th vegetation type, reflecting the importance and influence of the vegetation type in the slope vegetation coverage, which is determined by the distribution density, growth status and root type of the vegetation; i represents the vegetation type; n represents the total number of vegetation types;

[0094] D rj represents the length of the jth root, σtj represents the tensile strength of the jth root, A rj represents the cross-sectional area of ​​the jth root system, j represents the root system of a certain vegetation type; m represents the total number of roots of a certain vegetation type;

[0095] ρ r is the root density; P hi and P vi They represent the horizontal root ratio and vertical root ratio of the kth vegetation type, respectively; n represents the total number of vegetation types;

[0096] Δτ is the increment of the root system’s shear strength to the soil, σ t-avg is the average tensile strength of the root system;

[0097] c is soil cohesion, η is root distribution efficiency factor, D avg is the average root diameter;

[0098] E root is the root enhancement factor, E s is the soil reinforcement efficiency under the influence of vegetation, F c is the factor affecting the vegetation growth cycle;

[0099] k1, k2, k3, k4, and k8 are weight coefficients, which are determined by fitting experimental data.

[0100] In some embodiments, a slope stability assessment model considering the influence of vegetation is also provided. The model is constructed using the construction method of the slope stability assessment model considering the influence of vegetation described above. When evaluating the stability of a slope, the model can be used for calculation to obtain a comprehensive assessment value of the slope stability under the influence of different types of vegetation, thereby evaluating the stability of the slope under the influence of vegetation.

[0101] The technical solution provided in this embodiment analyzes the relationship between vegetation root morphology, growth rate and slope stability based on the soil consolidation effect of different types of vegetation, which helps to optimize vegetation selection and configuration, improve slope protection effect and reduce engineering costs. Constructing a slope stability assessment method that takes into account the influence of vegetation can achieve quantification and refinement of slope stability assessment, providing a reliable basis for engineering design and construction.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for constructing a slope stability assessment model considering the influence of vegetation, characterized in that: include: Determine vegetation classification; Obtain the root morphology of different types of vegetation, and calculate the root tensile strength and the soil shear strength increment under the action of the root system based on the root morphology; Obtain the growth rates of different types of vegetation, and calculate the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors based on the growth rates; A slope stability assessment model was constructed based on the root tensile strength and the increment of soil shear strength under the action of the root system, as well as the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors.

2. The method for constructing a slope stability assessment model considering vegetation influence according to claim 1, characterized in that: When determining vegetation classification, it is classified according to vegetation type and growth habit.

3. The method for constructing a slope stability assessment model considering vegetation influence according to claim 1, characterized in that: The root morphology includes: average root length, average root diameter, root density and root distribution morphology ratio.

4. The method for constructing a slope stability assessment model considering vegetation influence according to claim 3 is characterized in that: Calculate the root tensile strength based on the root morphology, including: Obtain the breaking force of root samples measured in the tensile strength test; The root cross-sectional area was calculated based on the average root diameter; The root tensile strength was calculated by dividing the breaking force by the root cross-sectional area.

5. The method for constructing a slope stability assessment model considering vegetation influence according to claim 4, characterized in that: Calculate the root shear strength based on the root morphology, including: Multiply the root-soil friction coefficient, root tensile strength and root density to obtain the soil shear strength increment under the action of the root system.

6. The method for constructing a slope stability assessment model considering vegetation influence according to claim 1, characterized in that: Obtaining the growth rates of different types of vegetation includes: measuring the growth amount of vegetation per unit time, wherein the growth amount includes an increase in root length or an increase in biomass.

7. The method for constructing a slope stability assessment model considering vegetation influence according to claim 1, characterized in that: The slope stability assessment model is constructed based on the root tensile strength and the soil shear strength increment under the action of the root system, as well as the root enhancement factor, soil reinforcement efficiency and vegetation growth cycle influencing factors, including: The root enhancement factor is introduced to consider the influence of roots on soil cohesion and internal friction angle, and the Mohr-Coulomb model is modified. Based on the modified Mohr-Coulomb model, the slope safety factor with the influence of vegetation is calculated.

8. The method for constructing a slope stability assessment model considering vegetation influence according to claim 1, characterized in that: The slope stability assessment model considering the influence of vegetation is calculated as follows: In the formula, F st It represents the comprehensive evaluation value of slope stability under the influence of different types of vegetation; F si represents the contribution of the i-th vegetation type to the slope stability, which is obtained through experimental observation and numerical simulation, and reflects the ability of this vegetation type in enhancing the slope stability; w i It represents the weight coefficient of the i-th vegetation type, reflecting the importance and influence of the vegetation type in the slope vegetation coverage, which is determined by the distribution density, growth status and root type of the vegetation; i represents the vegetation type; n represents the total number of vegetation types; D rj represents the length of the jth root, σ tj represents the tensile strength of the jth root, A rj represents the cross-sectional area of ​​the jth root system, j represents the root system of a certain vegetation type; m represents the total number of roots of a certain vegetation type; ρ r is the root density; P hi and P vi They represent the horizontal root ratio and vertical root ratio of the kth vegetation type, respectively; n represents the total number of vegetation types; Δτ is the increment of the root system’s shear strength to the soil, σ t-avg is the average tensile strength of the root system; c is soil cohesion, η is root distribution efficiency factor, D avg is the average root diameter; E root is the root enhancement factor, E s is the soil reinforcement efficiency under the influence of vegetation, F c is the factor affecting the vegetation growth cycle; k1, k2, k3, k4, and k8 are weight coefficients, which are determined by fitting experimental data.

9. A slope stability assessment model considering the influence of vegetation, characterized in that: The method according to any one of claims 1 to 8 is used to construct the 10. A method for evaluating slope stability, characterized in that: Taking into account the influence of vegetation on the slope, the slope stability assessment model described in claim 9 is used to assess the slope stability.

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