Method and system for determining shear strength parameter reduction relationship in slope stability evaluation

Abstract

This invention discloses a method and system for determining the reduction relationship of shear strength parameters in slope stability evaluation, belonging to the technical field of slope stability evaluation. It solves the problem of poor application effect caused by the use of proportional reduction in existing strength reduction methods. The method includes: S1, acquiring geological survey data of the slope area to be analyzed, and classifying the slope soil and rock mass into multiple weathering grades according to the degree of weathering based on the geological survey data; S2, acquiring multiple shear strength parameters of the soil and rock mass for each weathering grade, and calculating the numerical ratio of the same shear strength parameter between two adjacent weathering grades, denoted as the adjacent grade reduction ratio; S3, determining the final reduction relationship between different shear strength parameters based on the adjacent grade reduction ratios of different shear strength parameters. This invention is used for slope stability evaluation.

Description

Technical Field

[0001] This invention relates to a method and system for determining the reduction relationship of shear strength parameters in slope stability evaluation, belonging to the technical field of slope stability evaluation. Background Technology

[0002] The strength reduction method is a method for calculating the stability coefficient of slope stability using the finite element method. Its principle can be simply summarized as follows: in the calculation, the safety factor of the slope is continuously reduced, and the reduced parameters are repeatedly substituted into the model for repeated calculations until the model reaches its limit and failure occurs. The value before failure is the safety factor of the slope.

[0003] The key theoretical point of the strength reduction method is to reduce the cohesion (c) and friction coefficient in the shear strength parameters of the slope soil. ( The ratio of the internal friction angle (the angle of friction) to the reduction factor Fs is c′=c / F. s1 , Two new soil shear strength parameters c′ and are obtained. Then, substitute this new set of soil shear strength parameters into the calculation, and reduce the soil shear strength parameters according to the calculation results. Repeat the trial calculation and adjust the reduction coefficient Fsi continuously until the slope is in critical equilibrium, and then it becomes unstable and fails. Analyze and obtain the most dangerous sliding surface of the slope. The average value of the reduction coefficient Fs corresponding to this sliding surface is the equivalent safety factor of the slope.

[0004] In existing slope stability analyses, the strength reduction method uses a proportional reduction (reduction c, ...). The safety factor is calculated using the method described above. However, in actual engineering projects, the shear strength parameters of the soil on slopes are often not reduced proportionally. For example, when conducting rock shear strength degradation tests on sandy rocks and muddy rocks, it was found that the friction coefficient of the former decreased more significantly, while the cohesion decreased less, and the latter showed the opposite. This makes the existing strength reduction method less effective. The specific reduction gradient of the shear strength parameters of various rock masses is closely related to their rock quality, lithology, rock mass type, weathering degree, and geological conditions. Using the same proportional reduction is inconsistent with the actual engineering geological conditions and cannot guide engineering construction. Summary of the Invention

[0005] This invention provides a method and system for determining the reduction relationship of shear strength parameters in slope stability evaluation, which can solve the problem of poor application effect caused by the use of proportional reduction in existing strength reduction methods.

[0006] On the one hand, the present invention provides a method for determining the reduction relationship of shear strength parameters in slope stability evaluation, the method comprising:

[0007] S1. Obtain geological survey data of the slope area to be analyzed, and classify the slope rock and soil into multiple weathering levels according to the degree of weathering based on the geological survey data;

[0008] S2. Obtain multiple shear strength parameters of the soil and rock mass for each weathering grade, and calculate the numerical ratio of the same shear strength parameter between two adjacent weathering grades, which is recorded as the reduction ratio between adjacent grades.

[0009] S3. Determine the final reduction relationship between different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters.

[0010] Optionally, S3 specifically includes:

[0011] S31. Determine the reduction relationship between adjacent grades of different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters;

[0012] S32. Based on the adjacent grade reduction relationship, determine the final reduction relationship across grades between different shear strength parameters.

[0013] Optionally, S31 specifically includes:

[0014] Calculate the ratio of the reduction ratio of adjacent grades for different shear strength parameters, and record it as the reduction relationship between adjacent grades for different shear strength parameters.

[0015] Optionally, S32 specifically includes:

[0016] Calculate the average value of the reduction relationships between multiple adjacent levels of different shear strength parameters, and record it as the final reduction relationship between different shear strength parameters.

[0017] Optionally, the weathering level includes strong weathering, weak weathering, and slight weathering.

[0018] Optionally, the shear strength parameters include cohesion parameters and friction coefficients.

[0019] Optionally, the shear strength parameter includes both natural state parameter values ​​and saturated state parameter values.

[0020] On the other hand, the present invention provides a system for determining the reduction relationship of shear strength parameters in slope stability evaluation, the system comprising:

[0021] The acquisition unit is used to acquire geological survey data of the slope area to be analyzed, and to classify the slope rock and soil into multiple weathering levels according to the degree of weathering based on the geological survey data.

[0022] The calculation unit is used to obtain multiple shear strength parameters of soil and rock for each weathering grade, and to calculate the numerical ratio of the same shear strength parameter between two adjacent weathering grades, which is recorded as the reduction ratio between adjacent grades.

[0023] The determination unit is used to determine the final reduction relationship between different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters.

[0024] Optionally, the determining unit is specifically used for:

[0025] The reduction relationship between adjacent grades of different shear strength parameters is determined based on the reduction ratio between adjacent grades of different shear strength parameters;

[0026] Based on the adjacent grade reduction relationship, the final reduction relationship across grades between different shear strength parameters is determined.

[0027] Optionally, the determining unit is specifically used for:

[0028] Calculate the ratio of the reduction ratio of adjacent grades for different shear strength parameters, and record it as the reduction relationship between adjacent grades of different shear strength parameters;

[0029] Calculate the average value of the reduction relationships between multiple adjacent levels of different shear strength parameters, and record it as the final reduction relationship between different shear strength parameters.

[0030] The beneficial effects that this invention can produce include:

[0031] The method for determining the reduction relationship of shear strength parameters in slope stability evaluation provided by this invention calculates different reduction ratios of shear strength parameters c and tanφ based on the weathering grade of the soil and rock mass, thus obtaining the final reduction relationship between the shear strength parameters c and tanφ. Because the method provided by this invention fully considers the non-uniform reduction of soil shear strength parameters in actual engineering projects, it conforms to the weathering characteristics of rock mass and the reduction rules based on rock lithology, rock quality, and type. This improves the application effect of the strength reduction method, making the method more accurate, scientific, and reasonable. Attached Figure Description

[0032] Figure 1 A schematic diagram of the strength reduction method provided for existing technologies;

[0033] Figure 2 The flowchart of the method for determining the reduction relationship of shear strength parameters in slope stability evaluation provided by the embodiments of the present invention Figure 1 ;

[0034] Figure 3 The flowchart of the method for determining the reduction relationship of shear strength parameters in slope stability evaluation provided by the embodiments of the present invention Figure 2 . Detailed Implementation

[0035] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0036] The strength reduction method is one of the methods used in the finite element method for calculating the safety factor of slope stability. To make the theory of the strength reduction method more intuitive and easier to understand, this paper combines... Figure 1 Let's explain the principle of the strength reduction method in detail. Figure 1 This diagram illustrates the positional relationship between the Mohr stress circle and the strength parameter envelope during the strength reduction method. The circle on the horizontal axis is the Mohr circle, and its two intersection points σ1 and σ3 represent the maximum and minimum principal stresses of the stressed body, respectively. Any location in the soil can be represented by the Mohr circle, and the straight line in the diagram represents the strength envelope. The strength reduction process can generally be divided into three stages: 1) Initial stage: The strength parameter envelope is furthest from the Mohr stress circle, indicating that the slope is in a stable state; 2) Transition stage: The slope strength parameters are gradually reduced, and the strength parameter envelope slowly approaches the Mohr stress circle, with a decreasing slope, indicating that the stability of the slope has decreased after reduction; 3) Equilibrium stage: The reduction factor increases to Fs, and the reduced strength parameter envelope is exactly tangent to the Mohr stress circle, indicating that the slope is in a critical state, and the corresponding shear strength and shear stress are in a limit equilibrium state. The reduction factor Fs at this point is the slope safety factor.

[0037] Therefore, it can be concluded that the strength reduction method is the process of finding the strength envelope that is exactly tangent to the Mohr circle by adjusting the reduction coefficient.

[0038] In numerical analysis of slope stability, the strength reduction method often uses the proportional reduction (reduction of c and tanφ) method to calculate the safety factor. However, in actual engineering, the shear strength parameters of soil and rock are often not reduced proportionally. Therefore, this invention proposes a non-proportional method for obtaining strength reduction in numerical analysis of slope stability, which mainly calculates different reduction ratios of shear strength parameters c and tanφ based on the weathering degree of soil and rock.

[0039] Specifically, embodiments of the present invention provide a method for determining the reduction relationship of shear strength parameters in slope stability evaluation, such as... Figure 2 As shown, the method includes:

[0040] S1. Obtain geological survey data of the slope area to be analyzed, and classify the slope rock and soil into multiple weathering levels according to the degree of weathering based on the geological survey data.

[0041] This invention does not limit the number of weathering grades for different rock and soil masses; those skilled in the art can make the classifications according to actual conditions. Generally, slope rock and soil masses can be classified into three weathering grades: strongly weathered, weakly weathered, and slightly weathered.

[0042] S2. Obtain multiple shear strength parameters of the soil and rock mass for each weathering grade, and calculate the numerical ratio of the same shear strength parameter between two adjacent weathering grades, which is recorded as the reduction ratio between adjacent grades.

[0043] The shear strength parameters may include the cohesion parameter c and the friction coefficient tanφ. Generally, the values ​​of shear strength parameters in geological survey data include natural state parameters and saturated state parameters. This invention provides specific physical and mechanical parameter values ​​for a slope soil mass, as shown in Table 1.

[0044] Table 1 Physical and mechanical parameters of slope soil and rock mass

[0045]

[0046] Referring to Table 1, for natural parameters, from slightly weathered to weakly weathered, the reduction ratio of adjacent grades of cohesion parameter c is 350 / 600 = 0.583, and the coefficient of friction... The reduction ratio between adjacent weathering grades is tan35° / tan42°=0.778; from weakly weathered to strongly weathered, the reduction ratio between adjacent weathering grades of cohesion parameter c is 150 / 350=0.429, and the coefficient of friction... The reduction ratio for adjacent grades is tan26.6° / tan35°=0.715.

[0047] S3. Determine the final reduction relationship between different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters.

[0048] Specifically, it includes:

[0049] S31. Determine the reduction relationship between adjacent grades of different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters.

[0050] Specifically, the ratio of the reduction ratios of adjacent grades of different shear strength parameters is calculated and recorded as the reduction relationship between adjacent grades of different shear strength parameters.

[0051] For example, referring to Table 1, for natural parameters, from slightly weathered to weakly weathered, the cohesion parameter c and the coefficient of friction are... The reduction relationship between adjacent weathering levels is 0.583 / 0.778 = 0.749; from weakly weathered to strongly weathered, the cohesion parameter c and the friction coefficient... The reduction relationship between adjacent grades is 0.429 / 0.715 = 0.6.

[0052] S32. Based on the reduction relationship between adjacent grades, determine the final reduction relationship between different shear strength parameters across grades.

[0053] Specifically, the average value of the reduction relationships between multiple adjacent levels of different shear strength parameters is calculated and recorded as the final reduction relationship between different shear strength parameters.

[0054] For example, as shown in Table 1, for natural parameters, the cohesion parameter c and the friction coefficient change as the soil mass changes from slightly weathered to weakly weathered to strongly weathered. The final reduction relationship is (0.749+0.6) / 2=0.675.

[0055] Based on this reduction relationship, the cohesive parameter c and the friction coefficient are calculated. A non-proportional reduction can achieve a better reduction effect.

[0056] Another embodiment of the present invention provides a system for determining the reduction relationship of shear strength parameters in slope stability evaluation, the system comprising:

[0057] The acquisition unit is used to acquire geological survey data of the slope area to be analyzed, and to classify the slope rock and soil into multiple weathering levels according to the degree of weathering based on the geological survey data;

[0058] The calculation unit is used to obtain multiple shear strength parameters of soil and rock for each weathering grade, and to calculate the numerical ratio of the same shear strength parameter between two adjacent weathering grades, which is recorded as the reduction ratio between adjacent grades.

[0059] The determination unit is used to determine the final reduction relationship between different shear strength parameters based on the reduction ratio of adjacent grades of different shear strength parameters.

[0060] Furthermore, the specific use of the unit is as follows:

[0061] The reduction relationship between adjacent grades of different shear strength parameters is determined based on the reduction ratio between adjacent grades of different shear strength parameters;

[0062] Based on the reduction relationship between adjacent grades, the final reduction relationship across grades for different shear strength parameters is determined.

[0063] Furthermore, the specific use of the unit is as follows:

[0064] Calculate the ratio of the reduction ratio of adjacent grades for different shear strength parameters, and record it as the reduction relationship between adjacent grades of different shear strength parameters;

[0065] Calculate the average value of the reduction relationships between multiple adjacent levels of different shear strength parameters, and record it as the final reduction relationship between different shear strength parameters.

[0066] The specific description of each unit in the above-mentioned determination system can be found in the description of each step in the determination method, and will not be repeated here. The above-mentioned determination system can achieve the same function as the determination method.

[0067] This invention calculates different reduction ratios of the shear strength parameters c and tanφ based on the weathering grade of the soil and rock mass, thus obtaining the final reduction relationship between c and tanφ. Because the method provided by this invention fully considers the non-uniform reduction of the soil shear strength parameters in actual engineering slopes, it conforms to the weathering characteristics of rock mass and the reduction rules based on rock lithology, quality, and type. This improves the application effect of the strength reduction method, making it more accurate, scientific, and reasonable.

[0068] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for determining a reduction relationship of a shear strength parameter in slope stability evaluation, characterized in that, The method comprises: S1, obtaining geological exploration data of a to-be-analyzed slope area, and dividing the slope rock-soil mass into a plurality of weathering grades according to the weathering degree of the geological exploration data; S2, obtaining a plurality of shear strength parameters of the rock-soil mass of each weathering grade, and calculating a value ratio of the same shear strength parameter of two adjacent weathering grades, denoted as an adjacent grade reduction ratio; S3, determining a final reduction relationship between different shear strength parameters according to the adjacent grade reduction ratios of different shear strength parameters; The S3 specifically comprises: S31, calculating a ratio of the adjacent grade reduction ratios of different shear strength parameters, denoted as an adjacent grade reduction relationship between different shear strength parameters; S32, calculating an average value of a plurality of adjacent grade reduction relationships between different shear strength parameters, denoted as a final reduction relationship between different shear strength parameters.

2. The method of claim 1, wherein, The weathering grade includes strong weathering, weak weathering, and slight weathering.

3. The method of claim 1, wherein, The shear strength parameter includes a cohesion parameter and a friction coefficient.

4. The method according to claim 1 or 3, characterized in that, The value of the shear strength parameter includes a natural state parameter value and a saturated state parameter value.

5. A system for determining a reduction relationship of a shear strength parameter in a slope stability evaluation, characterized by, The system comprises: An acquisition unit configured to obtain geological exploration data of a to-be-analyzed slope area, and divide the slope rock-soil mass into a plurality of weathering grades according to the weathering degree of the geological exploration data; A calculation unit configured to obtain a plurality of shear strength parameters of the rock-soil mass of each weathering grade, and calculate a value ratio of the same shear strength parameter of two adjacent weathering grades, denoted as an adjacent grade reduction ratio; A determination unit configured to calculate a ratio of the adjacent grade reduction ratios of different shear strength parameters, denoted as an adjacent grade reduction relationship between different shear strength parameters, and calculate an average value of a plurality of adjacent grade reduction relationships between different shear strength parameters, denoted as a final reduction relationship between different shear strength parameters.

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