Modeling method of three-dimensional rock mesoscopic model capable of controlling shape of internal fracture surface

Abstract

The invention discloses modeling of a three-dimensional rock mesoscopic model capable of controlling the shape of an internal fissure surface. The modeling comprises the following steps: pre-establishing a three-dimensional model space with a certain size; randomly arranging nucleation points according to certain distance parameters in the space area of the three-dimensional model; generating a Voronoi model by taking any nucleating point as a center; the generated Voronoi model is cut, only hole walls between polyhedrons are reserved, and the shape of a fracture surface is controlled through selective deletion; and filling the remaining part in the three-dimensional model space. The method can truly reflect the morphological structure of the fissure surface in the rock, and directly realizes the morphological control of the fissure surface based on the random selection of the hole walls among the polyhedrons. The problems that in the current three-dimensional microscopic modeling process of the fractured rock, the fracture surface form cannot be truly reflected, and the fracture surface is difficult to control during generation are solved, parameterized modeling of the fractured rock is achieved, and a basis is provided for analyzing the influence of the internal fracture structure of the rock on the macromechanical property of the rock and a microscopic failure model.

Description

Technical Field

[0001] The present invention relates to the field of numerical simulation of rock mechanics, and particularly to a three-dimensional modeling method for the mesoscopic structure of rocks. Background Art

[0002] Rock is a natural heterogeneous, discontinuous, and anisotropic material, which is composed of various mineral components and initial defects inside. These are distributed interactively inside the rock, and the distribution pattern shows great randomness. The initial defects inside the rock include pores and fracture surfaces. Among them, the fracture surfaces are extremely irregular and discontinuous, which have a great impact on the mesoscopic mechanical properties and macroscopic failure modes of the rock. Currently, when studying the influence and failure mechanism of internal fractures of rocks during failure, the numerical simulation method is the most important means, and the accuracy of the numerical simulation results mainly depends on whether the established model can characterize the structural characteristics of the fractures. Therefore, how to establish a model of the rock fracture surface at the mesoscopic level is crucial for studying the mechanical properties of rocks. Based on this, the present invention proposes a modeling method for a three-dimensional rock mesoscopic model with controllable internal fracture surface morphology. Summary of the Invention

[0003] The purpose of the present invention is to provide a modeling method for a three-dimensional model of the mesoscopic structure of rocks, so as to be able to effectively perform finite element modeling of rock materials.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A three-dimensional modeling method for the mesoscopic structure of rocks, comprising:

[0006] a) Pre-establish a three-dimensional model space of a certain size;

[0007] b) Randomly arrange nucleation points in the three-dimensional model space area according to certain distance parameters;

[0008] c) Generate a Voronoi model with any nucleation point as the center;

[0009] d) Cut the generated Voronoi model, only retain the pore walls between the polyhedra, and control the morphology of the fracture surface by selective deletion;

[0010] e) Fill the remaining part in the three-dimensional model space.

[0011] Preferably, the specific implementation manner of step a) adopted by the present invention is: pre-establish a three-dimensional model space with a certain spatial form as the rock model, and the generation of internal fractures of the rock is carried out in the three-dimensional model space.

[0012] Preferably, the specific implementation of step b) adopted in the present invention is as follows: The Monte Carlo method is used to generate randomly distributed spatial coordinate points in the three-dimensional model space, and these points are used as nucleation points. The specific construction steps are as follows:

[0013] ① Establish a spatial coordinate system for the three-dimensional model space;

[0014] ② Let the coordinates of the nucleation point be (x n , y n , z n ). The Monte Carlo method is used to generate random numbers as x n , y n , z n . When generating, it is necessary to limit the magnitudes of x n , y n , z n to avoid the generated nucleation points exceeding the three-dimensional model space.

[0015] ③ When setting the number of nucleation points, it is necessary to consider the size of the Voronoi polyhedron. Each nucleation point corresponds to the center of the Voronoi polyhedron. Assuming that the shape of the Voronoi polyhedron during formation is spherical and the corresponding average pore diameter is d, then the number of nucleation points N can be calculated according to the following formula:

[0016] In the formula, V is the size of the space corresponding to the specimen.

[0017] ④ During the random generation process, the minimum distance between any two nucleation points is set as δ. The smaller the minimum distance δ, the smaller the size of the generated single polyhedron and the denser the distribution. Through this parameter, the size and density of the polyhedron represented by the generated Voronoi structure can be reflected. In addition, by defining the parameter irregularity k to characterize the irregular degree of the generated model, the morphological characteristics of the polyhedron can be controlled, thereby indirectly controlling the morphology of the fracture surface.

[0018] In the formula, δ 0 is the minimum distance between adjacent nucleation points determined according to the number of polyhedra and the model size when the shape of the generated polyhedron is a regular polyhedron.

[0019] Preferably, the specific implementation of step c) adopted in the present invention is as follows: After randomly generating nucleation points, Delaunay triangulation is performed between adjacent nucleation points, and the Voronoi polyhedron structure can be obtained. The specific construction steps are as follows:

[0020] ① Connect any nucleation point with adjacent points in the space;

[0021] ②Construct a perpendicular bisecting plane for the line connecting two points;

[0022] ③Connect the perpendicular bisecting planes formed by the nucleation points in space. After connecting the perpendicular bisecting planes, remove the redundant parts according to the intersection points to obtain the Voronoi polyhedron structure;

[0023] ④Finally, generate the Voronoi polyhedron structures of all nucleation points in space.

[0024] Preferably, the specific implementation manner of step d) adopted in the present invention is: delete all the polyhedrons in the Voronoi polyhedron structure, only retain the pore walls between the polyhedrons, and finally form the rock fracture surface by adjusting the pore walls. The specific construction steps are as follows:

[0025] ①Through Boolean operation, combine all the polyhedrons in the Voronoi polyhedron structure into a whole, and the pore walls between the polyhedrons are still divided into separate individuals according to different formation processes;

[0026] ②Delete all the polyhedrons in the three-dimensional model space;

[0027] ③The pore walls can be selected for deletion by setting the number of fracture surfaces in the rock until the requirements of the number of fracture surfaces or the volume content are met, and finally the fracture surface inside the rock is formed.

[0028] Preferably, the specific implementation manner of step e) adopted in the present invention is: fill the remaining part in the three-dimensional model space with rock materials, and finally form a complete rock model with fracture surfaces in the three-dimensional model space.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The purpose of the present invention is to provide a modeling method for a three-dimensional mesoscopic rock model with controllable internal fracture surface morphology, which can truly reflect the morphological structure of the internal fracture surface of the rock and realizes the control of the fracture surface. The present invention can control the size and distribution of polyhedrons based on the minimum distance between nucleation points, indirectly control the fracture surface spacing; control the morphology of polyhedrons based on the irregularity of polyhedrons, indirectly control the fracture surface morphology; directly control the fracture surface morphology based on the random selection of pore walls between polyhedrons. The technical solution of the present invention solves the problems that the morphological structure of the fracture surface cannot be truly reflected and it is difficult to control the generation of the fracture surface in the current three-dimensional mesoscopic modeling process of fractured rocks. By setting the minimum distance between nucleation points, the irregularity of polyhedrons, the pore wall thickness between polyhedrons, the number of fracture surfaces and the random deletion position, the parametric modeling of fractured rocks is realized, providing a basis for analyzing the influence of the internal fracture structure of rocks on the macroscopic mechanical properties and mesoscopic failure models of rocks. Description of the Drawings

[0031] Figure 1 It is a flow chart of a modeling method of a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology provided by the present invention;

[0032] Figure 2 It is a schematic diagram of the Voronoi polyhedron structure generation process;

[0033] Figure 3 It is a schematic diagram of the crack generation process;

[0034] Figure 4 This is the effect diagram of rock with cracks; DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] like Figures 1 - 4 As shown, the present invention provides a modeling method for a three-dimensional rock mesoscopic model capable of controlling the morphology of internal fracture surfaces, the method comprising the following steps:

[0037] a) A three-dimensional model space with a certain spatial form is pre-established as a rock model, and the generation of internal cracks in the rock is carried out in the three-dimensional model space;

[0038] b) Using the Monte Carlo method to generate randomly distributed spatial coordinate points in the three-dimensional model space, which are used as nucleation points. The specific construction steps are as follows:

[0039] ① Establish a spatial coordinate system for the three-dimensional model space;

[0040] ② Let the coordinates of the nucleation point be (x n ,y n , z n ), using the Monte Carlo method to generate random numbers as x n ,y n , z n , x must be limited when generating n ,y n , z n The size of is set to avoid the generated nucleation points exceeding the 3D model space.

[0041] ③ When setting the number of nucleation points, the size of the Voronoi polyhedron needs to be considered. Each nucleation point corresponds to the center of the Voronoi polyhedron. Assuming that the shape of the Voronoi polyhedron is spherical during the formation process and the corresponding average pore diameter is d, then the number of nucleation points N can be calculated according to the following formula:

[0042] In the formula, V is the size of the space corresponding to the specimen.

[0043] ④ During the random generation process, the minimum distance between any two nucleation points is set to δ. The smaller the minimum distance δ, the smaller the size of the individual polyhedron generated and the denser the distribution. This parameter can reflect the size and density distribution of the polyhedrons represented by the generated Voronoi structure. In addition, by defining the parameter irregularity k to characterize the irregularity of the generated model, the morphological characteristics of the polyhedron can be controlled, thereby indirectly controlling the morphology of the fracture surface.

[0044] In the formula, δ 0 is the minimum distance between adjacent nucleation points determined according to the number of polyhedrons and the model size when the shape of the generated polyhedron is a regular polyhedron.

[0045] c) After randomly generating nucleation points, perform Delaunay triangulation between adjacent nucleation points to obtain the Voronoi polyhedron structure, as Figure 2 shown. The specific construction steps are as follows:

[0046] ① Connect any nucleation point with adjacent points in the space;

[0047] ② Make a perpendicular bisecting plane for the connection between two points;

[0048] ③ Connect the perpendicular bisecting planes formed by the nucleation points in the space. After connecting the perpendicular bisecting planes, remove the redundant parts according to the intersection points to obtain the Voronoi polyhedron structure;

[0049] ④ Finally, generate the Voronoi polyhedron structure of all nucleation points in the space.

[0050] d) Delete all the polyhedrons in the Voronoi polyhedron structure, only retain the pore walls between the polyhedrons, and finally form the rock fracture surface by adjusting the pore walls, as Figure 3 shown. The specific construction steps are as follows:

[0051] ① Through Boolean operation, combine all the polyhedrons in the Voronoi polyhedron structure into a whole. The pore walls between the polyhedrons are still divided into separate individuals according to the different formation processes;

[0052] ②Delete all polyhedra in the three-dimensional model space, and only retain the pore walls between the polyhedra;

[0053] ③Randomly delete the faces of the pore walls between the polyhedra. Each time a face is deleted, immediately calculate the porosity. When the predetermined porosity or the number of pore wall faces is reached, stop deleting.

[0054] e) Fill the remaining part in the three-dimensional model space with rock materials, and finally form a complete rock model with fracture surfaces in the three-dimensional model space, as Figure 4 shown.

Claims

1. A method for modeling a three-dimensional rock mesoscopic model capable of controlling the morphology of internal fracture surfaces, characterized in that: include: A) Establish a 3D model space of a certain size in advance; b) randomly arranging the core points in the three-dimensional model space according to a certain distance parameter; c) Generate a Voronoi model with any nucleation point as the center; d) cutting the generated Voronoi model to retain only the hole walls between the polyhedrons, and controlling the morphology of the crack surface by selective deletion; e) Fill the remaining part of the three-dimensional model space.

2. The method for modeling a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology according to claim 1, characterized in that: The specific implementation method of step a) is: pre-establishing a three-dimensional model space with a certain spatial form as a rock model, and generating internal cracks in the rock in the three-dimensional model space.

3. The method for modeling a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology according to claim 1, characterized in that: The specific implementation method of step b) is: using the Monte Carlo method to generate randomly distributed spatial coordinate points in the three-dimensional model space, and using them as nucleation points. The specific construction steps are as follows: ① Establish a spatial coordinate system for the three-dimensional model space; ② Let the coordinates of the nucleation point be (x n ,y n , z n ), using the Monte Carlo method to generate random numbers as x n ,y n , z n , x must be limited when generating n ,y n , z n The size of the nucleation points is prevented from exceeding the three-dimensional model space. ③ When setting the number of nucleation points, the size of the Voronoi polyhedron needs to be considered. Each nucleation point corresponds to the center of the Voronoi polyhedron. Assuming that the shape of the Voronoi polyhedron during the formation process is spherical and the corresponding average pore size is d, the number of nucleation points N can be calculated according to the following formula: In the formula, V is the size of the space corresponding to the specimen; ④ In the random generation process, the minimum distance between any two nucleation points is set to δ, and the parameter irregularity k is defined to characterize the irregularity of the generated model, so as to control the morphological characteristics of the polyhedron and indirectly control the morphology of the crack surface; Where δ0 is the minimum distance between adjacent nucleation points determined by the number of polyhedrons and the model size when the generated polyhedron is a regular polyhedron.

4. The method for modeling a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology according to claim 1, characterized in that: The specific implementation method of step c) is: after randomly generating nucleation points, Delaunay partitioning is performed between adjacent nucleation points to obtain a Voronoi polyhedron structure. The specific construction steps are as follows: ① Connect any nucleation point with adjacent points in space; ② Make a perpendicular bisector of the line between the two points; ③ Connect the perpendicular bisectors formed by the nucleation points in the space. After connecting the perpendicular bisectors, remove the excess parts according to the intersection points to obtain the Voronoi polyhedron structure. ④Finally, the Voronoi polyhedron structure of all nucleation points in the space is generated.

5. The method for modeling a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology according to claim 1, characterized in that: The specific implementation method of step d) is: all polyhedrons in the Voronoi polyhedron structure are deleted, only the hole walls between the polyhedrons are retained, and the rock fracture surface is finally formed by adjusting the hole walls. The specific construction steps are as follows: ① Through Boolean operations, all polyhedrons in the Voronoi polyhedron structure are combined into a whole, and the hole walls between the polyhedrons are still divided into separate individuals according to the different formation processes; ② Delete all polyhedrons in the 3D model space; ③ By setting the number of fracture surfaces in the rock, the hole wall is selected for deletion until the number of fracture surfaces or the volume content requirement is met, and finally the fracture surface inside the rock is formed.

6. The method for modeling a three-dimensional rock mesoscopic model capable of controlling the internal fracture surface morphology according to claim 1, characterized in that: The specific implementation method of step e) is: fill the remaining part in the three-dimensional model space with rock materials, and finally form a complete rock model containing fracture surfaces in the three-dimensional model space.

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