Three-dimensional finite element modeling method of multi-fault geologic body based on BIM

Abstract

The application provides a three-dimensional finite element modeling method of a multi-fault geologic body based on BIM, and based on the defects and deficiencies of the prior art, the application fully utilizes existing observation data, and a three-dimensional multi-fault geomechanical model is established based on a BIM modeling software Rhino. Then, the HyperMesh software is used for meshing, and then the mesh model is imported into a finite element program for calculation, so that the regional seismic risk can be better evaluated.

Description

Technical Field

[0001] This invention relates to the fields of BIM modeling, finite element modeling, and numerical simulation technology, and in particular to a three-dimensional finite element modeling method for multi-fault geological bodies based on BIM. Background Technology

[0002] Tectonic earthquakes occur when rock strata accumulate stress under the influence of tectonic forces, reaching a limit state and subsequently fracturing and shifting at relatively weak points. Faults are formed at these points. By fully utilizing existing geological and geophysical observation data, a three-dimensional numerical model incorporating a complex regional fault system can be constructed to simulate the spatiotemporal evolution of earthquake sequences, explore the controlling factors and dynamic processes of earthquake gestation and occurrence, and assess the future seismic hazard of the region.

[0003] Existing numerical models of fault zones in the Earth's crust and lithosphere are gradually being developed and improved. However, two-dimensional models neglect the dip angle and its variations deep within the faults; some three-dimensional models use fixed fault dip angles, which similarly ignore the geometric complexity deep within the faults. As existing observational data continues to accumulate and the modeling foundation is constantly updated, existing numerical models are also gradually being developed and improved.

[0004] Existing technology 1 A Three-Dimensional Viscoelastic Modeling Method with Fractures Based on a Public Lithosphere Database - CN113298942A Existing technology 2: A method for modeling rock mechanical properties within fracture zones of shale reservoirs - CN114218790A Existing technology three A Three-Dimensional Geological Modeling Method for Multiple Complex Faults Applicable to Finite Element Numerical Simulation - CN115688506A Disadvantages of existing technology 1: 1. The geometry of the faults considered is too simple, and the strike and dip information of the faults are oversimplified, which will affect the accuracy of the simulation results of ground stress and earthquake sequence. 2. The constructed model can only be divided into tetrahedral mesh elements, not hexahedral elements, which may not be suitable for some finite element simulation programs; Disadvantages of existing technology 2: 1. Single fault modeling lacks understanding of the mutual influence between multiple faults; 2. It is not a systematic geological model; the fault model alone does not include surrounding rock and sedimentary strata. The disadvantages of existing technology three: 1. Fault completion methods are complex.

[0005] 2. The fault is constructed as a model of triangular facets, not a whole model, and the subsequent fusion of triangular facet meshes is time-consuming. Summary of the Invention

[0006] The technical problems to be solved by this invention include: 1. Fault models are constructed using geological and geophysical observation data (e.g., the three-dimensional fault model of the China Earthquake Science Experimental Field), making the fault geometry closer to the real situation.

[0007] 2. Modeling based on BIM software improves modeling speed and fault model accuracy, and allows for efficient optimization and adjustment of existing models according to requirements, thus overcoming the complexity of building complex fault system models using general-purpose finite element software such as Abaqus and Ansys.

[0008] 3. Mesh generation is based on HyperMesh software, resulting in high-quality meshes. It can also solve the problem of difficult mesh reconstruction for the same model when different computational accuracy requirements are needed.

[0009] Addressing the shortcomings and deficiencies of existing technologies, this invention fully utilizes existing observation data and establishes a three-dimensional multi-fault geomechanical model based on the BIM modeling software Rhino. Then, HyperMesh software is used for mesh generation, and the mesh model is imported into a finite element program for calculation to better assess regional seismic hazard.

[0010] The present invention specifically adopts the following technical solution: A three-dimensional finite element modeling method for multi-fault geological bodies based on BIM is characterized by: establishing a three-dimensional multi-fault geomechanical model using the BIM modeling software Rhino, then using HyperMesh software for mesh generation, and finally importing the mesh model into the finite element program for calculation to better assess the regional seismic hazard.

[0011] Furthermore, the actual observed three-dimensional spatial coordinate point set data of the fault is converted and imported into Rhino software to establish its geometric model; to ensure the accuracy of the fault geometry and to enable mesh generation, the fault surface is optimized; when the faults have contact relationships in space, the faults are subjected to operations including completion, extension, and trimming according to their geological significance. For complex faults, geometric modifications are made near the low angle of the fault by surface cutting. For faults with gaps, the tensile repair method is used to fill the gaps in the fault. When repairing, the properties of the fault, including strike and dip, are taken into account, as well as ensuring the integrity and wholeness of the entire fault zone.

[0012] Furthermore, the specific steps include: Step S1: Convert the data format of the three-dimensional spatial data point set of the fault from the UTM coordinate system WGS84 to latitude and longitude coordinates or rectangular coordinates; Step S2: Import the converted fault 3D spatial data point set into Rhino software, and construct fault planes using the matte function in the software; Step S3: Adjust and optimize the fault model in Rhino software, including: deleting abnormal data points, trimming the constructed fault plane, trimming the fault plane according to the data points so that the fault plane is within the range of the data points, and then making local corrections to the fault plane so that it matches the geometric outer edge of the fault obtained by actual measurement. Step S4: Check in Rhino software whether the established fault model is closed and complete; the fault is represented by the fault plane or by a fault zone of a certain thickness; Step S5: Determine the latitude and longitude range of the regional geological bodies in Rhino software; establish a three-dimensional geomechanical geometric model of the region; and, based on the theory of active blocks, divide the different blocks in the model on the horizontal layer. Step S6: Perform Boolean operations on the model in Rhino software; perform Boolean operations on the geological bodies at the fault locations to establish a three-dimensional geomechanical geometric model containing the complex regional fault system; Step S7: In Rhino software, export the created 3D geometric model as an igs format data file; Step S8: Import the igs type data file into HyperMesh; Step S9: Mesh the 3D geometric model in HyperMesh software. Use the Mesh control function to set up seeds for different regions to obtain the 3D finite element mesh of the geometric model. Step S10: Adjust the mesh in HyperMesh software for different computational analysis needs; Step S11: In HyperMesh software, convert the mesh model into a format that the finite element software can recognize; Step S12: Import the converted mesh model file into the finite element analysis software for calculation and analysis.

[0013] Furthermore, in step S3, the fault surface is smoothed.

[0014] Further, in step S6 or step S9, the operation of hollowing out the geological body model so that the fault model and the geological body model are embedded together is performed.

[0015] Compared to existing technologies, the key design features of this invention and its preferred embodiments include: 1. Convert the actual observed fault three-dimensional spatial coordinate point set data and import it into Rhino software to establish its geometric model; 2. To ensure the accuracy of the fault geometry and to enable mesh generation, the fault surface needs to be optimized; 4. When faults are in contact with each other in space, the faults should be supplemented, extended, or trimmed according to their geological significance. 5. For complex faults, geometric modifications should be made near the low angle of the fault. Appropriate surface cutting is beneficial for successful mesh generation and the generation of high-quality finite element elements. 6. For faults with gaps, the gaps in the fault should be filled (using the tension filling method). When filling, the properties of the fault (such as strike and dip angle) should be considered. The filled fault should ensure the integrity and completeness of the entire fault zone. 7. When meshing, use HyperMesh software, which is specifically designed for meshing, to mesh the geometric model; Its main advantages include: 1. Reduce modeling time. Currently, the commonly used modeling method for numerical calculations is still in general-purpose finite element software (such as Abaqus and Ansys). These software programs have relatively simple geometric modeling functions but are complex to use, and the tedious modeling steps require a significant amount of time. Utilizing Rhino's parametric modeling significantly reduces the time spent on modeling and improves modeling efficiency.

[0016] 2. Improve modeling accuracy. Currently, the commonly used modeling method in numerical calculations is still in general-purpose finite element software. These general-purpose software can only roughly outline the three-dimensional geometry of the fault, resulting in a large error compared to actual observations. Using the Rhino modeling software in this solution, the three-dimensional spatial coordinates of the actual observed fault can be directly imported and optimized. The model established is basically consistent with the actual observed fault geometry, greatly improving modeling accuracy.

[0017] 3. Adjusting fault models is much easier. Currently, numerical calculations commonly use general-purpose finite element software for modeling. If errors occur during the modeling process in these software programs, subsequent adjustments require a significant amount of time and effort to remodel. Using Rhino software makes model adjustments much easier, allowing for direct fine-tuning of areas with errors. The modification steps are explained above, and the modification method is very convenient.

[0018] 4. More flexible and detailed mesh generation. Using specialized mesh generation software like HyperMesh to generate meshes from the established geometric model results in more flexible mesh generation and higher mesh quality. Attached Figure Description

[0019] The following detailed description of this embodiment, in conjunction with the accompanying drawings and specific implementation details, is as follows: Figure 1 This is the set of measured three-dimensional spatial coordinate points of the fault in an embodiment of the present invention; Figure 2 This is a cross-sectional diagram of importing a data point set into Rhino software according to an embodiment of the present invention. Figure 3 This is a fault plane model diagram created in Rhino software based on data points according to an embodiment of the present invention; Figure 4 This is a diagram of the overall fault plane model integrated in Rhino software for all fault planes in this embodiment of the invention; Figure 5 This is a three-dimensional geological model diagram of a complex regional fault system created in Rhino software according to an embodiment of the present invention; Figure 6 A hexahedral mesh model drawn using HyperMesh software in an embodiment of the present invention. Figure 7 This is a flowchart illustrating the process from BIM software Rhino, mesh drawing software HyperMesh, to finite element analysis software (such as Abaqus) in an embodiment of the present invention. Detailed Implementation

[0020] To make the features and advantages of this patent more apparent and understandable, specific embodiments are provided below, along with accompanying drawings, for detailed explanation: like Figures 1-7 As shown, the specific steps of the method provided in this embodiment of the invention are as follows: 1. Convert the data format of the three-dimensional spatial data point set of the fault from the UTM coordinate system WGS84 to latitude and longitude coordinates or rectangular coordinates.

[0021] 2. Import the converted fault 3D spatial data point set into Rhino software, and use the matte function in the software to construct fault planes from the imported data points.

[0022] 3. Adjust and optimize the fault model in Rhino software. This includes deleting outlier data points and trimming the constructed fault planes (since some geometry in the mosaic model may exceed the range of data points, trimming makes the model fit the actual observed data points better). Simultaneously, trim the fault planes according to the data points to ensure they are within the data point range, and then perform local corrections to make them conform to the outer edge of the measured fault geometry. This results in a more accurate and realistic fault model. Additionally, the fault surface can be smoothed to facilitate subsequent finite element calculations.

[0023] 4. Check in Rhino software whether the established fault model is closed and complete. Faults can be represented by fault planes or fault zones of a certain thickness.

[0024] 5. Determine the latitude and longitude range of the regional geological bodies in Rhino software; the depth can be stretched based on CRUST1.0 data, or the stretching range can be defined manually (e.g., 20 km deep in the upper crust, 80 km deep in the middle and lower crust and upper mantle), and establish a three-dimensional geomechanical geometric model of the region. At the same time, according to the theory of active blocks, the different blocks in the model are divided on the horizontal layers.

[0025] 6. Perform Boolean operations on the model in Rhino software. Perform Boolean operations on the geological bodies at the fault locations to hollow out the geological body model so that the fault model and the geological body model are embedded together (this step can also be done in HyperMesh), and establish a three-dimensional geomechanical geometric model containing the complex fault system in the region.

[0026] 7. In Rhino software, export the created 3D geometric model as an igs format data file.

[0027] 8. Import igs type data files into HyperMesh.

[0028] 9. If step 6 was not performed in Rhino, it can be performed in HyperMesh.

[0029] 10. In HyperMesh software, mesh the 3D geometric model. Use the Mesh control function to set seeds for different regions to obtain the 3D finite element mesh of the geometric model. The mesh can be tetrahedral or hexahedral.

[0030] 11. For different computational analysis needs, the mesh can be adjusted in HyperMesh software.

[0031] 12. In HyperMesh software, convert the mesh model into a format that finite element software can recognize, such as the inp file format that Abaqus can recognize.

[0032] 13. Import the converted mesh model file into the finite element analysis software for calculation and analysis.

[0033] This patent is not limited to the above-described preferred embodiment. Anyone can derive other forms of BIM-based three-dimensional finite element modeling methods for multi-fault geological bodies under the guidance of this patent. All equivalent changes and modifications made within the scope of the patent application based on this embodiment shall fall within the scope of this patent.

Claims

1. A three-dimensional finite element modeling method for multi-fault geological bodies based on BIM, characterized in that: A three-dimensional multi-fault geomechanical model was established using the BIM modeling software Rhino. Then, HyperMesh software was used for mesh generation. Finally, the mesh model was imported into a finite element program for calculation to assess regional seismic hazard. The calculation process specifically included: Step S1: Convert the data format of the three-dimensional spatial data point set of the fault from the UTM coordinate system WGS84 to latitude and longitude coordinates or rectangular coordinates; Step S2: Import the converted fault 3D spatial data point set into Rhino software, and construct fault planes using the matte function in the software; Step S3: Adjust and optimize the fault model in Rhino software, including: deleting abnormal data points, trimming the constructed fault plane, trimming the fault plane according to the data points so that the fault plane is within the range of the data points, and then making local corrections to the fault plane so that it matches the geometric outer edge of the fault obtained by actual measurement. Step S4: Check in Rhino software whether the established fault model is closed and complete; the fault is represented by the fault plane or by a fault zone of a certain thickness; Step S5: Determine the latitude and longitude range of the regional geological bodies in Rhino software; establish a three-dimensional geomechanical geometric model of the region; and, based on the theory of active blocks, divide the different blocks in the model on the horizontal layer. Step S6: Perform Boolean operations on the model in Rhino software; perform Boolean operations on the geological bodies at the fault locations to establish a three-dimensional geomechanical geometric model containing the complex regional fault system; Step S7: In Rhino software, export the created 3D geometric model as an igs format data file; Step S8: Import the igs type data file into HyperMesh; Step S9: Mesh the 3D geometric model in HyperMesh software. Use the Mesh control function to set up seeds for different regions to obtain the 3D finite element mesh of the geometric model. Step S10: Adjust the mesh in HyperMesh software for different computational analysis needs; Step S11: In HyperMesh software, convert the mesh model into a format that the finite element software can recognize; Step S12: Import the converted mesh model file into the finite element analysis software for calculation and analysis.

2. The three-dimensional finite element modeling method for multi-fault geological bodies based on BIM according to claim 1, characterized in that: The actual observed fault three-dimensional spatial coordinate point set data is converted and imported into Rhino software to establish its geometric model; to ensure the accuracy of fault geometry and to enable mesh generation, the fault surface is optimized; when faults have contact relationships in space, the faults are subjected to operations including completion, extension, and trimming according to their geological significance. For complex faults, geometric modifications are made near the low angle of the fault by surface cutting. For faults with gaps, the tensile repair method is used to fill the gaps in the fault. When repairing, the properties of the fault, including strike and dip, are taken into account, as well as ensuring the integrity and wholeness of the entire fault zone.

3. The three-dimensional finite element modeling method for multi-fault geological bodies based on BIM according to claim 1, characterized in that: In step S3, the fault surface is smoothed.

4. The three-dimensional finite element modeling method for multi-fault geological bodies based on BIM according to claim 1, characterized in that: Perform the following operation in step S6 or step S9: hollow out the geological body model so that the fault model and the geological body model are embedded together.

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