Modeling method of three-dimensional rock mesoscopic model based on random putting algorithm

Abstract

The invention discloses a modeling method of a three-dimensional rock mesoscopic model based on a random putting algorithm. The modeling method comprises the following steps: pre-establishing a three-dimensional model space with a certain size; pre-determining the particle size and content of each mineral particle of the rock model; pre-determining the internal pore size and porosity of the built rock sample model; generating polyhedral mineral particles and pore particles according to the determined particle size of the mineral particles and the pore size in the rock; according to the determined internal porosity of the rock model, the polyhedral pore particles are put in the three-dimensional model space based on a random putting algorithm; and putting and filling polyhedral mineral particles in the residual three-dimensional model space based on a random putting algorithm according to the determined mineral components and contents of the rock model. According to the method, the problems of inaccuracy, complexity and the like in the existing rock mesoscopic modeling are solved, and a basis is provided for analyzing the characteristics of different rock materials.

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] In the construction of traditional three-dimensional finite element models of rocks, rocks are usually regarded as a single homogeneous material, and the mechanical parameters measured by experiments are given to them. However, this modeling method ignores the mesoscopic structure and internal mineral components of rocks. Rocks are typical discontinuous, inhomogeneous, and anisotropic materials, which contain a variety of different mineral particles and primary pores, all of which have a great impact on the mechanical properties of rocks, resulting in a large difference between the simulation results and the indoor tests, and the change of the internal structure during the rock failure process cannot be reflected. Therefore, how to reflect the mesoscopic structure of rocks is the key to accurately establishing a three-dimensional finite element model of rocks, which is related to the accuracy of subsequent simulation calculation results. Based on this, the present invention proposes a modeling method for a three-dimensional rock mesoscopic model based on a random placement algorithm. 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 object, 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) Pre-determine the particle size and content of each mineral particle of the rock model;

[0008] c) Pre-determine the internal pore size and porosity of the established rock specimen model;

[0009] d) Generate polyhedral mineral particles and pore particles according to the determined particle size of the mineral particles and the internal pore size of the rock;

[0010] e) Based on the determined porosity of the internal pores of the rock model, randomly place the polyhedral pore particles in the three-dimensional model space according to the random placement algorithm;

[0011] f) Based on the determined composition and content of each mineral component of the rock model, randomly place and fill the polyhedral mineral particles in the remaining three-dimensional model space according to the random placement algorithm.

[0012] Preferably, the specific implementation method of step a) adopted in the present invention is: pre-establishing a three-dimensional model space of a certain size and shape as a rock model for subsequent placement of rock mineral particles and the like.

[0013] Preferably, the specific implementation method of step b) adopted in the present invention is: select rock samples of the same type, scan them using CT equipment, and obtain the mineral composition, content and mineral particle size of the pre-selected rock samples through grayscale recognition.

[0014] Preferably, the specific implementation method of step c) adopted in the present invention is: select rock samples of the same type, scan them using CT equipment, identify the pores in the rock, and obtain the pore size and content of the pre-selected rock sample.

[0015] Preferably, the specific implementation method of step d) adopted in the present invention is: constructing rock mineral particles and porous particles. In order to fully reflect the diversity, randomness and irregularity of the particles, a single mineral particle and a porous particle are a polyhedral structure, and the shape is controlled by setting the minimum circumscribed circle radius of the polyhedral structure and the number of polyhedral vertices. The specific construction steps are as follows:

[0016] ① Let D be the particle size to be generated, let R = 0.5D, first generate a sphere with a radius of R in the three-dimensional model space;

[0017] ② Randomly select four non-coplanar points on the sphere to form a tetrahedron;

[0018] ③ Randomly add points on the sphere. Every time a new point is added, the polyhedron is re-judged and the face of the polyhedron closest to the point is deleted;

[0019] ④ Connect each vertex of the deleted face to the point to form a new polyhedron;

[0020] ⑤Add points until the number of faces of the polyhedron meets the requirements.

[0021] Preferably, the specific implementation method of step e) adopted in the present invention is: according to the porosity requirement of the rock model, the number of porous particles of different particle sizes is determined, and then the polyhedral porous particles of different particle sizes are sequentially placed into the three-dimensional model space according to the random placement algorithm until the porosity requirement is met. The specific construction steps are as follows:

[0022] ① Taking the center coordinates of the spherical matrix of the polyhedral porous particle as the placement point, according to the principle of random distribution of spatial position, the first spatial random coordinate point is generated in the placement area space as the placement point of the first porous particle to be placed, and the boundary judgment is performed to ensure that the polyhedral porous particle does not exceed the placement boundary;

[0023] ② Place the Nth polyhedral pore particle, generate a random spatial placement point, and perform boundary determination; subsequently, sequentially determine whether there is intrusion between the Nth polyhedral pore particle and the previously placed (N + 1) particles. If there is intrusion, regenerate the placement point;

[0024] ③ During the placement of polyhedral pore particles, continuously calculate the placed porosity. If the content requirement is met, stop the placement.

[0025] Preferably, the specific implementation manner of step f) adopted in the present invention is: according to the content of each mineral component and the requirements of the mineral particle size of the rock model, determine the number of mineral particles of different components and different particle sizes. Subsequently, according to the random placement algorithm, sequentially put polyhedral mineral particles of different components and different particle sizes into the three-dimensional model space. Finally, directly fill the last type of mineral particles in the remaining three-dimensional model space to form a three-dimensional mesoscopic rock model. The specific construction steps are as follows:

[0026] ① The placement order of polyhedral mineral particles is carried out in ascending order according to the content of mineral components;

[0027] ② Take the spherical matrix center coordinates of the polyhedral mineral particle as the placement point. According to the principle of random spatial distribution, generate the first random spatial coordinate point in the placement area space as the placement point of the first polyhedral mineral particle, and perform boundary determination and intrusion determination to ensure that the polyhedral mineral particle does not exceed the placement boundary and does not intrude with the pore particle;

[0028] ③ Continue to place mineral particles in order. After each placement, perform boundary determination, and then determine whether there is intrusion with the previously placed mineral particles and pore particles. If there is intrusion, regenerate the placement point;

[0029] ④ When placing the last mineral component, directly fill it in the remaining three-dimensional model space to form a complete three-dimensional mesoscopic rock model.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The object of the present invention is to provide a method for modeling a three-dimensional model of the mesoscopic structure of rocks, which can clearly characterize the mineral composition and particle morphology of minerals inside rocks, and perform modeling according to the predetermined rock mineral composition, content, mineral particle morphology, porosity, and pore particle morphology. The present invention can control the particle shape based on the vertex positions and numbers of polyhedral particle models; control the porosity and mineral content based on different particle sizes and numbers; and control the spatial distribution of particles based on different particle placement areas. The technical solution of the present invention solves the problems of inaccuracy and excessive complexity existing in current rock mesoscopic modeling, can realize parametric modeling of the rock mesoscopic structure, and can accurately simulate the discontinuity, heterogeneity, and anisotropy characteristics of rock-like materials by controlling the composition of internal particles, providing a basis for analyzing the characteristics of different rock materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of a method for modeling a three-dimensional model of the mesoscopic structure of rocks provided by the present invention;

[0033] Figure 2 is an example of scanning a rock specimen;

[0034] Figure 3 is a schematic diagram of polyhedral particles constructed by the present invention;

[0035] Figure 4 is a diagram of pore particle placement;

[0036] Figure 5 is a diagram of mineral particle placement (except for the mineral with the highest content);

[0037] Figure 6 is a diagram of mineral particle placement (when all minerals are placed); DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] As Figures 1-6 shown, the present invention provides a method for modeling a three-dimensional rock mesoscopic model based on a random placement algorithm, and the method includes the following steps:

[0040] a) Obtain the mineral composition, content, and porosity through CT scanning. Taking the rock specimen shown in Figure 2 as an example, its main constituent minerals are feldspar, quartz, biotite, etc.

[0041] b) Establish a three-dimensional model space of a certain size in advance;

[0042] c) Construct rock mineral particles and porous particles. In order to fully reflect the diversity, randomness and irregularity of particles, single mineral particles and porous particles are polyhedral structures. The shape is controlled by setting the minimum circumscribed circle radius of the polyhedral structure and the number of polyhedral vertices, such as Figure 3 The specific construction steps are as follows:

[0043] ① Let D be the particle size to be generated, let R = 0.5D, first generate a sphere with a radius of R in the three-dimensional model space;

[0044] ② Randomly select four non-coplanar points on the sphere to form a tetrahedron;

[0045] ③ Randomly add points on the sphere. Every time a new point is added, the polyhedron is re-judged and the face of the polyhedron closest to the point is deleted;

[0046] ④ Connect each vertex of the deleted face to the point to form a new polyhedron;

[0047] ⑤Add points until the number of faces of the polyhedron meets the requirements.

[0048] e) According to the porosity requirements of the rock model, the number of porous particles of different particle sizes is determined, and then the polyhedral porous particles of different particle sizes are sequentially placed into the three-dimensional model space according to the random placement algorithm until the porosity requirements are met. The specific construction steps are as follows:

[0049] ① Taking the center coordinates of the spherical matrix of the polyhedral porous particle as the placement point, according to the principle of random distribution of spatial position, the first spatial random coordinate point (x 1 ,y 1 , z 1 ) is used as the placement point of the first porous particle, and the coordinate point value x 1 ,y 1 , z 1 The Monte Carlo random algorithm is used to obtain the coordinate point value, and the coordinate point value is set not to exceed the three-dimensional model space. After the coordinates of the placement point are determined, the porous particles are placed, and the boundaries of all vertices of the polyhedral porous particles are determined to ensure that all vertices are located in the three-dimensional model space. If not, the placement is repeated.

[0050] ② Place the Nth polyhedral porous particle, generate random placement points in space through Monte Carlo random algorithm, and perform boundary judgment on the polyhedral porous particles to ensure that the porous particles are all located in the three-dimensional model space. If not, re-place them; then determine in turn whether there is any invasion between the Nth polyhedral porous particle and the first (N+1) particles that have been placed, that is, whether all faces of the placed polyhedral particles are in contact with the remaining polyhedrons. If there is any invasion, regenerate the placement point;

[0051] ③ During the process of placing polyhedral porous particles, the porosity of the particles is continuously calculated. If the content requirement is reached, the placement is stopped. Figure 4 shown.

[0052] f) According to the requirements of the content of each mineral component and the particle size of the mineral particles of the rock model, the number of mineral particles of different components and different particle sizes is determined, and then the polyhedral mineral particles of different components and different particle sizes are sequentially placed into the three-dimensional model space according to the random placement algorithm. Finally, the last type of mineral particles are directly filled in the remaining three-dimensional model space to form a rock microscopic three-dimensional model. The specific construction steps are as follows:

[0053] ① The order of placing polyhedral mineral particles is determined by the content of different mineral components, and the specific order is from low to high;

[0054] ② First, place the mineral particles with the lowest content. When placing, the center coordinates of the spherical matrix of the polyhedral mineral particles are used as the placement point. According to the principle of random distribution of spatial position, the first spatial random coordinate point (x 1 ,y 1 , z 1 ) as the placement point for placing mineral particles, the coordinate point value x 1 ,y 1 , z 1 It is obtained through Monte Carlo random algorithm, and the coordinate point value is set not to exceed the three-dimensional model space. After the coordinates of the placement point are determined, the mineral particles are placed, and the boundary judgment is performed on all vertices of the polyhedral mineral particles to ensure that all vertices are located in the three-dimensional model space. If not satisfied, the placement is repeated, and then the mineral particles are subjected to invasion judgment to ensure that all faces of the mineral particles are not in contact with the porous particles and mineral particles. If not satisfied, the placement is repeated until the content requirements of this type of mineral are met;

[0055] ③ Continue to place the next type of mineral particles in order. The placement method of each type of mineral particles is the same. After each placement is completed, boundary judgment and intrusion judgment are performed. If the conditions are not met, a new placement point is generated;

[0056] ④When the last type of mineral components is added, such asFigure 5 The last type of mineral components (minerals with the highest content) are no longer placed in the form of mineral particles, but are directly filled in the remaining three-dimensional model space to form a complete rock microscopic three-dimensional model, as shown in Figure 6 shown.

Claims

1. A modeling method for a three-dimensional rock mesoscopic model based on a random placement algorithm, characterized in that: include: a) Establish a three-dimensional model space of a certain size in advance; b) Predetermine the particle size and content of each mineral particle in the rock model; c) predetermine the internal pore size and porosity of the constructed rock sample model; d) generating polyhedral mineral particles and porous particles according to the determined mineral particle size and the pore size inside the rock; e) placing polyhedral porous particles in the three-dimensional model space based on a random placement algorithm according to the determined internal porosity of the rock model; f) According to the determined mineral components and contents of the rock model, polyhedral mineral particles are placed and filled in the remaining three-dimensional model space based on a random placement algorithm.

2. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step a) is: pre-establishing a three-dimensional model space of a certain size and shape as a rock model for subsequent placement of rock mineral particles.

3. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step b) is: select rock samples of the same type, scan them using CT equipment, and obtain the mineral composition, content and mineral particle size of the pre-selected rock samples through grayscale recognition.

4. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step c) is: select rock samples of the same type, scan them using CT equipment, identify the pores in the rocks, and obtain the pore size and content of the pre-selected rock samples.

5. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step d) is: construct rock mineral particles and porous particles. In order to fully reflect the diversity, randomness and irregularity of the particles, the single mineral particles and porous particles are polyhedral structures, and their morphology is controlled by setting the minimum circumscribed circle radius of the polyhedral structure and the number of polyhedral vertices. The specific construction steps are as follows: ① Let D be the particle size to be generated, let R = 0.5D, first generate a sphere with a radius of R in the three-dimensional model space; ② Randomly select four non-coplanar points on the sphere to form a tetrahedron; ③ Randomly add points on the sphere. Every time a new point is added, the polyhedron is re-judged and the face of the polyhedron closest to the point is deleted; ④ Connect each vertex of the deleted face to the point to form a new polyhedron; ⑤Add points until the number of faces of the polyhedron meets the requirements.

6. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step e) is: according to the porosity requirements of the rock model, the number of porous particles of different particle sizes is determined, and then the polyhedral porous particles of different particle sizes are sequentially placed into the three-dimensional model space according to the random placement algorithm until the porosity requirements are met. The specific construction steps are as follows: ① Taking the center coordinates of the spherical matrix of the polyhedral porous particle as the placement point, according to the principle of random distribution of spatial position, the first spatial random coordinate point is generated in the placement area space as the placement point of the first porous particle to be placed, and the boundary judgment is performed to ensure that the polyhedral porous particle does not exceed the placement boundary; ② Place the Nth polyhedral porous particle, generate a random placement point in space, and perform boundary judgment; then determine in turn whether there is an invasion between the Nth polyhedral porous particle and the first (N+1) particles that have been placed. If there is an invasion, regenerate the placement point; ③ During the process of adding polyhedral porous particles, the porosity of the particles is continuously calculated. If the content requirement is met, the addition is stopped.

7. The modeling method of a three-dimensional rock mesoscopic model based on a random placement algorithm according to claim 1 is characterized in that: The specific implementation method of step f) is: according to the requirements of the content of each mineral component and the particle size of the mineral particles of the rock model, the number of mineral particles of different components and different particle sizes is determined, and then the polyhedral mineral particles of different components and different particle sizes are sequentially placed into the three-dimensional model space according to the random placement algorithm, and finally the last type of mineral particles are directly filled in the remaining three-dimensional model space to form a rock microscopic three-dimensional model. The specific construction steps are as follows: ① The order of placing polyhedral mineral particles is from low to high in terms of the content of mineral components; ② Taking the center coordinates of the spherical matrix of the polyhedral mineral particles as the placement point, according to the principle of random distribution of spatial position, in the space of the placement area, generate the first spatial random coordinate point as the placement point of the first polyhedral mineral particle, and perform boundary judgment and intrusion judgment to ensure that the polyhedral mineral particles do not exceed the placement boundary and do not invade the porous particles; ③ Continue to place mineral particles in sequence. After each placement, perform boundary determination, and then determine whether there is invasion with the already placed mineral particles and porous particles. If there is invasion, regenerate the placement point; ④ When the last mineral component is added, it is directly filled in the remaining three-dimensional model space to form a complete rock microscopic three-dimensional model.

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