Fracture slope stability evaluation method based on fracture random expansion algorithm

Abstract

The invention discloses a crack slope stability evaluation method based on a crack random expansion algorithm. The method comprises the following steps: determining a minimum enclosing rectangle according to the size of a slope model to be modeled; on the basis of a fracture random expansion algorithm, generating a random fracture model within the range of the minimum bounding rectangle by setting parameters such as fracture length, width and quantity; assigning the fracture model to the slope model area to generate a fracture slope model; importing the fracture slope model into finite element calculation software, dividing grids and setting boundary conditions and load steps; a strength reduction method is adopted for calculation, and the failure mode and the safety coefficient of the fractured slope are obtained. According to the method, the fracture random expansion algorithm and the slope stability evaluation method are combined, the problem that in a traditional fracture slope model, the fracture form is simplified through manual hand drawing or random cross straight lines is solved, and the authenticity of fracture slope modeling is improved.

Description

Technical Field

[0001] The invention relates to the technical field of crack slope stability analysis, and in particular to a crack slope stability evaluation method based on a crack random expansion algorithm. Background Art

[0002] The stability of the slope is directly related to the safety and economic benefits of the project. Due to the complexity and uncertainty of the geological environment, slope instability problems occur from time to time, which brings great challenges to engineering construction. Fissure slopes are widely present in rock or soil slopes in nature, and their development degree and spatial distribution characteristics have a significant impact on the mechanical properties and stability of the slope. At present, the main methods for slope stability evaluation include limit equilibrium method, finite element method, discrete element method, etc. These methods have achieved certain results in slope stability analysis, but there are still some limitations. Especially for the modeling and calculation of fissure slopes, uniform or randomly distributed straight lines are often used for simplification. This method is simple and easy, but it is difficult to accurately characterize the failure mode and safety factor of the real fissure slope. Therefore, how to simulate the true form of cracks in the slope and perform stability calculations is a problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to provide a fracture slope stability analysis method capable of simulating the real fracture morphology in view of the shortcomings of the existing methods.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A method for evaluating the stability of a fractured slope based on a fracture random expansion algorithm, characterized in that it comprises the following steps:

[0006] Step 1: According to the actual situation of the slope, determine the maximum width and depth of the structural fissures in the slope, and determine the length L of its minimum circumscribed rectangle according to the range of the fissures to be generated. r and width W r , the rectangular area is the crack simulation area;

[0007] Step 2: Divide the crack simulation area into grids. The grid form is regular triangle, and the grid side length is l t ;

[0008] Step 3: According to the actual direction of the structural cracks of the slope, set two weight parameters α in the horizontal and vertical directions. x and α y ;

[0009] Step 4: Determine the number of cracks n in the slope according to the actual situation of the slope c , average width w ac and the maximum length lmc ;

[0010] Step 5: Extract the node coordinates of each grid and use random uniform distribution to determine n in the area. c The initial point is used as the starting point for the development of the fissure;

[0011] Step 6: Perform iterative calculation based on the initial point, with the number of iteration steps being n i , when the crack extends to the edge of the simulation area or reaches a predetermined number of iterations, the crack will stop developing;

[0012] Step 7, import the coordinates of the slope contour nodes, that is, the coordinates of the vertices of the regular triangle mesh on the slope contour, delete the mesh outside the contour, extract the edge contour, and export the model file format that can be used for numerical calculation;

[0013] Step 8: Import the model file into the finite element numerical calculation software, and assign values ​​to the materials of the slope and the crack area according to the actual conditions of the slope;

[0014] Step 9: Mesh the slope model and calculate it using the strength reduction method;

[0015] Step 10: After the calculation is completed, extract the slope safety factor and sliding surface shape for stability evaluation.

[0016] Furthermore, in step 1, if it is intended to generate structural fractures in the entire slope area, the fracture simulation area is the minimum circumscribed rectangle of the slope model.

[0017] Furthermore, in step 3, the weight parameter is defined as the probability of the crack developing in the corresponding direction at each step. The parameter value range is [0,1], and the sum of the two is 1; the two extreme cases are: if α x =1 and α y = 0, the cracks develop only in the horizontal direction; if α x = 0 and α y =1, the cracks only develop along the vertical direction.

[0018] Furthermore, in step 6, the calculation formula for the number of iteration steps is:

[0019] Furthermore, in step 6, the crack is formed by splitting the mesh vertices, and the mesh at the center of the crack is split into two in the horizontal or vertical direction. The direction of the crack development is calculated by the weight parameter, and the direction of the crack tip can be determined from the six vertices around the center of the crack.

[0020] Furthermore, in step 7, an edge detection algorithm is used to identify the boundaries of the crack and slope model and extract the edge contour.

[0021] Furthermore, in step 7, the algorithm selected to identify the boundaries of the crack and slope model and extract the edge contour should meet the four requirements of graphics denoising, edge detection, shape simplification and model export.

[0022] Furthermore, in step 8, in order to avoid the non-convergence problem of finite element calculation caused by the complex shape of the crack, the material is assigned to the crack; if the crack is considered to be a weak interlayer, the material parameters of the weak zone are assigned to the crack area; if the crack is considered to be a cavity, the cohesion is assigned to 0.001 kPa and the internal friction angle is assigned to 0°.

[0023] Furthermore, in step 9, considering that the density of the mesh inside the crack is very high and the crack distribution is the main factor affecting the shape of the sliding surface of the crack slope, in order to improve the calculation efficiency, the mesh of the non-crack slope area does not need to be refined.

[0024] The present invention realizes the acquisition of the failure mode of the fracture slope and the calculation of the safety factor by combining the random crack expansion algorithm with the finite element numerical calculation method. The method includes the following steps: determining its minimum circumscribed rectangle according to the size of the slope model to be modeled; generating a random fracture model within the above minimum circumscribed rectangle by setting parameters such as fracture length, width, and number based on the random crack expansion algorithm; assigning the fracture model to the slope model area to generate a fracture slope model; importing the fracture slope model into the finite element calculation software, dividing the grid and setting boundary conditions and load steps; using the strength reduction method for calculation to obtain the failure mode and safety factor of the fracture slope. The present invention overcomes the problem of simplifying the fracture morphology by hand-drawing or random cross straight lines in the traditional fracture slope model by combining the random crack expansion algorithm with the slope stability evaluation method, and improves the authenticity of the fracture slope modeling.

[0025] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The method of the present invention can model a fracture slope with a real fracture morphology;

[0027] (2) The present invention provides a meshing method and a parameter assignment method for finite element analysis of fractured slopes, thereby improving the efficiency and convergence of model calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The present invention is a flow chart of the method for evaluating the stability of a fissure slope. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] In this embodiment, taking a common soil slope as an example, the specific values ​​of the following parameters are respectively preferred parameters for evaluating a slope with a similar actual situation to the slope using the present invention.

[0031] like Figure 1 As shown in FIG. 1 , the fracture slope stability evaluation method based on the fracture random expansion algorithm includes the following steps:

[0032] (1) For the slope of this embodiment, the length L of the minimum circumscribed rectangle of the crack range to be generated is r and width W r Set to 15m and 6m respectively;

[0033] (2) Divide the fracture simulation area into grids. The grid form is an equilateral triangle with a grid side length of l t Set to 0.1m;

[0034] (3) Set two weight parameters α in the horizontal and vertical directions x and α y Both are 0.5;

[0035] (4) Set the number of cracks n in the slope c is 5, the average width w ac 0.2m, maximum length l mc 20m;

[0036] (5) Extract the node coordinates of each grid and determine five initial points as the starting points of crack development by randomly and evenly distributing them in the region;

[0037] (6) Perform iterative calculation based on the initial point, with the number of iteration steps n i When the crack extends to the edge of the simulation area or reaches the predetermined number of iterations, the crack will stop developing.

[0038] (7) Import the node coordinates of the slope contour, delete the grid outside the contour, use the edge detection algorithm to identify the boundaries of the crack and slope model, extract the edge contour, and export the model file format that can be used for numerical calculation;

[0039] (8) The model file was imported into the finite element numerical calculation software, and the cohesion of other areas of the slope and the crack area was set to 20 kPa and 2 kPa, respectively, and the internal friction angle was set to 30° and 10°, respectively;

[0040] (9) The slope model is divided into free grids and then calculated using the strength reduction method;

[0041] (10) After the calculation is completed, the slope safety factor and sliding surface shape are extracted, where the safety factor is 1.15.

[0042] It should be noted that the above embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

Claims

1. A fracture slope stability evaluation method based on a fracture random expansion algorithm is characterized by: The following steps are involved: Step 1: According to the actual situation of the slope, determine the maximum width and depth of the structural fissures in the slope, and determine the length L of its minimum circumscribed rectangle according to the range of the fissures to be generated. r and width W r , the rectangular area is the crack simulation area; Step 2: Divide the crack simulation area into grids. The grid form is regular triangle, and the grid side length is l t ; Step 3: According to the actual direction of the structural cracks of the slope, set two weight parameters α in the horizontal and vertical directions. x and α y ; Step 4: Determine the number of cracks n in the slope according to the actual situation of the slope c , average width w ac and the maximum length l mc ; Step 5: Extract the node coordinates of each grid and use random uniform distribution to determine n in the area. c The initial point is used as the starting point for the development of the fissure; Step 6: Perform iterative calculation based on the initial point, with the number of iteration steps being n i , when the crack extends to the edge of the simulation area or reaches a predetermined number of iterations, the crack will stop developing; Step 7, import the coordinates of the slope contour nodes, that is, the coordinates of the vertices of the regular triangle mesh on the slope contour, delete the mesh outside the contour, extract the edge contour, and export the model file format that can be used for numerical calculation; Step 8: Import the model file into the finite element numerical calculation software, and assign values ​​to the materials of the slope and the crack area according to the actual conditions of the slope; Step 9: Mesh the slope model and calculate it using the strength reduction method; Step 10: After the calculation is completed, extract the slope safety factor and sliding surface shape for stability evaluation.

2. The method for evaluating the stability of a fracture slope using a fracture random expansion algorithm according to claim 1, characterized in that: In step 1, if structural fractures are to be generated in the entire slope area, the fracture simulation area is the minimum circumscribed rectangle of the slope model.

3. The method for evaluating the stability of a fracture slope using a fracture random expansion algorithm according to claim 1, characterized in that: In step 3, the weight parameter is defined as the probability of the crack developing in the corresponding direction at each step. The parameter value range is [0,1], and the sum of the two is 1; the two extreme cases are: if α x =1 and α y = 0, the cracks develop only in the horizontal direction; if α x = 0 and α y =1, the cracks develop only along the vertical direction.

4. The method for evaluating the stability of a fracture slope using a fracture random expansion algorithm according to claim 1, characterized in that: In step 6, the calculation formula for the number of iterations is:

5. The method for evaluating the stability of a fracture slope using a fracture random expansion algorithm according to claim 1, characterized in that: In step 6, the crack is formed by splitting the mesh vertices. The mesh at the center of the crack is split into two in the horizontal or vertical direction. The direction of the crack development is calculated by the weight parameter, and the direction of the crack tip can be determined from the six vertices around the center of the crack.

6. The method for evaluating the stability of a fracture slope using a random fracture extension algorithm according to claim 1, characterized in that: In step 7, an edge detection algorithm is used to identify the boundaries of the crack and slope model and extract the edge contour.

7. The method for evaluating the stability of a fracture slope using a random fracture extension algorithm according to claim 1, characterized in that: In step 7, the algorithm selected to identify the boundaries of the crack and slope model and extract the edge contour should meet the four requirements of graphics denoising, edge detection, shape simplification and model export.

8. The method for evaluating the stability of a fracture slope using a random fracture extension algorithm according to claim 1, characterized in that: In step 8, in order to avoid the non-convergence problem of finite element calculation caused by the complex shape of the crack, the material is assigned to the crack; if the crack is considered to be a weak interlayer, the material parameters of the weak zone are assigned to the crack area; if the crack is considered to be a cavity, the cohesion is assigned to 0.001 kPa and the internal friction angle is assigned to 0°.

9. The method for evaluating the stability of a fracture slope using a random fracture extension algorithm according to claim 1, characterized in that: In step 9, considering that the density of the mesh inside the crack is very high and the crack distribution is the main factor affecting the shape of the sliding surface of the crack slope, in order to improve the calculation efficiency, the mesh of the non-crack slope area does not need to be refined.

Images