Rough single fracture seepage simulation and method based on 3D printing

Abstract

The invention belongs to the technical field of geotechnical engineering, and discloses a rough single fracture seepage simulation method based on 3D printing, and the method comprises the following specific steps: step 1, drawing a fracture profile curve: a model required by a test is a rough curved surface digital model, and according to a ten-level standard roughness profile curve proposed by Barton, a rough single fracture seepage simulation model is obtained; the method comprises the following steps: acquiring specific data of 10 ten-level standard roughness profile curves, and performing two-dimensional reconstruction on the specific data in AutoCAD software; on the basis of ten standard roughness profile curves proposed by Barton, the profiles are accurately reproduced through the 3D printing technology, the comprehensiveness and accuracy of the test are ensured, in addition, the crack opening degree and roughness are adjusted, a corresponding model is printed in a 3D mode, the roughness characteristics of the crack can be accurately copied, and the test precision is improved. The roughness and the opening degree of the fractures can be flexibly adjusted, so that different test requirements can be met, and a powerful tool is provided for deeply researching the seepage characteristics of fractured rock mass.

Description

Technical Field

[0001] The present invention belongs to the field of geotechnical engineering technology, and specifically relates to a rough single fracture seepage simulation and method based on 3D printing. Background Art

[0002] In nature, most rock masses are hidden deep beneath the surface, and the environment they are in is complex and changeable. There are a large number of cracks with different occurrences, properties and scales in these rock masses. Studying the seepage characteristics of these fractured rock masses is a difficult problem in many fields such as geotechnical engineering, geological engineering, mining and unconventional natural gas extraction. A single rough fracture is the basic unit of the natural fracture network of the rock mass, and its permeability characteristics are crucial to understanding the overall seepage mechanism. The permeability laws of these fractures are the basis for describing the seepage behavior of fractured rock masses. However, under actual conditions, there are almost no absolutely smooth and completely parallel fractures in nature. The roughness and irregularity of the fracture surface will significantly affect the fluid flow characteristics. Therefore, traditional methods (such as assuming that the fracture surface is smooth and parallel) are often difficult to accurately simulate the actual seepage behavior.

[0003] At present, there are two main methods for generating rough fracture surfaces. One is the rough fracture modeling method based on fractal theory, and the other is the Fourier transform modeling method based on spatial frequency distribution. In terms of seepage, researchers have proposed nonlinear rough fracture seepage models such as the Forchheimer equation, the Izbash equation, the hypercube law and the local cubic law based on indoor test results. However, due to the limitation of the number of rough fracture surfaces produced indoors, the study of rough fracture seepage has problems such as a small number of experiments and poor experimental repeatability, which limits the use conditions of the descriptive model and has certain deviations from actual engineering. At the same time, there is a lack of experimental methods for the correlation between fracture aperture and fracture roughness. Summary of the Invention

[0004] The purpose of the present invention is to provide a rough single fracture seepage simulation and method based on 3D printing to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a rough single fracture seepage simulation and method based on 3D printing, the specific steps are as follows:

[0006] Step 1: Draw the crack contour curve

[0007] The model required for the test is a digital model of a rough surface. According to the ten-level standard roughness profile curve proposed by Barton, the specific data of 10 ten-level standard roughness profile curves are obtained and reconstructed in two dimensions in AutoCAD software to obtain 10 10mm two-dimensional roughness curves.

[0008] Step 2: Create a 3D model of the fracture

[0009] A 10mm long standard contour curve was proportionally enlarged 10 times to 100mm. The accuracy of the enlarged standard contour curve remained unchanged, and 10 two-dimensional surfaces of cracks with different roughness were obtained. The height coordinates of each point were input into the Rhino software according to the enlarged roughness contour curve data to draw each standard contour curve. Then, according to the 10 two-dimensional roughness curves, the peak-to-valley height, spacing and shape of the contour curve were adjusted. The direction perpendicular to the crack surface was selected for non-proportional scaling to change the crack opening. By inputting different scaling ratios, a crack model with adjustable opening can be obtained, which was then created into a semi-cylindrical crack three-dimensional model with a diameter of 100mm, a height of 100mm and a crack of ten levels of roughness.

[0010] Step 3: 3D printing to make a crack model

[0011] Import the semi-cylindrical crack 3D model created in step 2 into the 3D printing software, set the printing parameters, and make cylindrical models with different roughness. Import the set printing parameters into the 3D printer, return the nozzle and the hot bed to the origin and preheat them to the required printing temperature, then put the PLA material into the printer for printing to complete the model preparation. After the model preparation is completed, prepare the cylindrical wall surface;

[0012] Step 4: Casting the crack specimen mold

[0013] Cement was used as the raw material, 40% of an anti-seepage agent was added, and the materials were stirred evenly before casting the specimens. After casting, the specimens were cured in a ventilated place at room temperature and then demolded. The two semi-cylinders were combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness. The above operation was repeated to prepare 10 single-crack specimens with different roughness at the same opening and 10 single-crack specimens with the same roughness at different openings. The former were the first experimental group, and the latter were the second experimental group.

[0014] Step 5: Conduct the experiment

[0015] Seepage tests were carried out on the single-crack specimens in the two experimental groups in turn.

[0016] As a preferred technical solution of the present invention, the roughness of the roughness profile curve in step 1 is controlled to be 0-20, and its calculation formula is:

[0017] JRC=(2sinθ) 2 / 3 d 1 / 3

[0018] Where θ is the slope angle of the structural surface (in radians), and d is the actual width of the structural surface (in meters).

[0019] As a preferred technical solution of the present invention, the model required for the test in step 1 needs to be prepared as a rough curved surface digital model with a length of 100 mm and a width of 100 mm.

[0020] As a preferred technical solution of the present invention, when using the Rhino software described in step 2, it is necessary to check the three-dimensional fracture model after it is created to determine the quality of the model.

[0021] As a preferred technical solution of the present invention, the 3D printing software described in step three adopts Cura software, the required temperature of the 3D printer nozzle described in step two is 210°C, and the required temperature of the hot bed is 60°C.

[0022] As a preferred technical solution of the present invention, the specific preparation method of the cylindrical wall surface described in step three is: using Rhino software to create a hollow cylindrical wall surface with an inner diameter of 100 mm and a thickness of 2 mm; importing the created model into the 3D printing software Cura, and setting the printing parameters according to predetermined parameters; importing the set parameters into the 3D printer, returning the nozzle and the hot bed to the origin and preheating them to the required printing temperature, and placing the PLA material into the printer for printing.

[0023] As a preferred technical solution of the present invention, the cement described in step 4 is 42.5R Portland cement with a water-cement ratio of 0.3.

[0024] As a preferred technical solution of the present invention, the specific method for preparing the specimen described in step four is: use 42.5R silicate cement to cast the specimen, add 40% of the anti-seepage agent, and the water-cement ratio is 0.3. The material is stirred evenly and the specimen is cast; after the specimen is cast, it is demolded after curing in a ventilated place at room temperature for 72 hours, and the semi-cylinder mold is taken out. The two parts of the semi-cylinder are combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness, and fixed with tape. After the above operations, 10 single-crack specimens with different roughness are prepared.

[0025] As a preferred technical solution of the present invention, the specific method of the specimen experiment described in step 5 is as follows: open the upper cover of the pressure chamber of the rock permeability analyzer, confirm that the central glue seal is intact, screw on the bottom layer cover, place the lower permeable plate, then place the prepared single-crack cement specimen, place the second layer of sealing ring, place the upper permeable device, screw on the upper cover, tighten the cover screws, and place it in the standard position of the permeability analyzer;

[0026] Connect one end of the outlet pipe on the main unit to the connection of the water permeable device hole on the upper cover with a plastic water pipe, and connect the other end to the water tank of the permeation analyzer to ensure that the water inlet pipe is unobstructed and water flows in normally;

[0027] Connect a hose to the water outlet at the bottom of the main unit and connect it to the two buckets to ensure that there is no water leakage at the water outlet;

[0028] Before starting the test, manually load the confining pressure to 5-7MPa, check whether the oil pressure inside the pressure chamber is stable and there is no oil leakage, ensure that there is sufficient water in the water tank, start the hydraulic pump to apply water pressure, and keep the flow adjustment knob open to fill the pressure chamber with water pressure, and confirm that water flows out of the connecting pipe;

[0029] According to the experimental design, confining pressure and water pressure were applied to single-crack cement specimens with different roughness in sequence. The test time was 520s, and the seepage rate of single-crack cement specimens with different roughness was recorded during the test time.

[0030] After the test, first unload the water pressure, then unload the confining pressure, turn the zero-pressure valve to unload the remaining confining pressure in the pressure chamber, open the upper cover, take out the test piece, and then replace it with a new one. Repeat the above steps and conduct seepage tests on 10 test pieces in sequence.

[0031] Study the correlation between crack opening and crack roughness;

[0032] Based on the experimental data obtained, a scatter plot is drawn with crack opening as the horizontal axis and roughness as the vertical axis to visually observe the distribution trend between the two.

[0033] The Pearson correlation coefficient is used to calculate the correlation between crack roughness and opening, and to determine the strength and direction of the correlation between the two. The specific calculation method is:

[0034]

[0035] In the formula, r is the Pearson correlation coefficient, which ranges from -1 to 1, and x i 、y i represent the experimental values of crack roughness and opening, represent the average values of crack roughness and opening, respectively, and n is the sample size;

[0036] Determination of correlation strength and direction:

[0037] When |r| approaches 1, it indicates that there is a strong linear correlation between crack roughness and aperture. When r approaches 1, it is a strong positive correlation, that is, when the crack roughness increases, the aperture also increases; when r approaches -1, it is a strong negative correlation, that is, when the crack roughness increases, the aperture decreases.

[0038] When 0.7<|r|<1, it indicates that there is a strong correlation between the two;

[0039] When 0.3<|r|<0.7, it indicates that there is a moderate correlation between the two;

[0040] When 0<|r|<0.3, it indicates that there is a weak correlation between the two;

[0041] When |r|≈0, it indicates that there is almost no linear relationship between the two.

[0042] The beneficial effects of the present invention are as follows:

[0043] This paper is based on the ten standard roughness profile curves proposed by Barton. These profiles are accurately reproduced through 3D printing technology, ensuring the comprehensiveness and accuracy of the test. In addition, by adjusting the fracture aperture and roughness and 3D printing the corresponding model, it is possible not only to accurately replicate the roughness characteristics of the fracture, but also to flexibly adjust the roughness and aperture of the fracture to meet different test requirements, providing a powerful tool for in-depth research on the seepage characteristics of fractured rock masses. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the Barton rock structural surface joint roughness contour curve of the present invention;

[0045] Figure 2 This is an enlarged scale schematic diagram of a casting mold for a crack specimen of the present invention;

[0046] Figure 3 This is a schematic diagram of the three-dimensional model of the crack curve of the present invention;

[0047] Figure 4 Schematic diagram of the structure of the crack specimen of the present invention. DETAILED DESCRIPTION

[0048] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] like Figures 1 to 4 As shown, the embodiment of the present invention provides a rough single fracture seepage simulation and method based on 3D printing, and the specific steps are as follows:

[0050] Step 1: Draw the crack contour curve

[0051] The model required for the test is a digital model of a rough surface. According to the ten-level standard roughness profile curve proposed by Barton, the specific data of 10 ten-level standard roughness profile curves are obtained and reconstructed in two dimensions in AutoCAD software to obtain 10 10mm two-dimensional roughness curves.

[0052] Step 2: Create a 3D model of the fracture

[0053] Ten 10mm long standard contour curves were equally scaled 10 times to 100mm in Rhino software. The accuracy of the scaled standard contour curves remained unchanged, and 10 two-dimensional surfaces of cracks with different roughness were obtained. The height coordinates of each point were input into Rhino software according to the scaled roughness contour curve data to draw each standard contour curve. Then, according to the 10 two-dimensional roughness curves, the peak-to-valley height, spacing and shape of the contour curve were adjusted. The direction perpendicular to the crack surface was selected for non-proportional scaling to change the crack opening. By inputting different scaling ratios, a crack model with adjustable opening can be obtained, which was then created into a semi-cylindrical crack three-dimensional model with a diameter of 100mm, a height of 100mm and a crack of ten levels of roughness.

[0054] Step 3: 3D printing to make a crack model

[0055] Import the semi-cylindrical crack 3D model created in step 2 into the 3D printing software, set the printing parameters, and make cylindrical models with different roughness. Import the set printing parameters into the 3D printer, return the nozzle and the hot bed to the origin and preheat them to the required printing temperature, then put the PLA material into the printer for printing to complete the model preparation. After the model preparation is completed, prepare the cylindrical wall surface;

[0056] Step 4: Casting the crack specimen mold

[0057] Cement was used as the raw material, 40% of an anti-seepage agent was added, and the materials were stirred evenly before casting the specimens. After casting, the specimens were cured in a ventilated place at room temperature and then demolded. The two semi-cylinders were combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness. The above operation was repeated to prepare 10 single-crack specimens with different roughness at the same opening and 10 single-crack specimens with the same roughness at different openings. The former were the first experimental group, and the latter were the second experimental group.

[0058] Step 5: Conduct the experiment

[0059] Seepage tests were carried out on the single-crack specimens in the two experimental groups in turn.

[0060] By amplifying the ten standard roughness profile curves proposed by Barton, a three-dimensional fracture model was produced. 3D printing technology was used to produce a fracture model that conformed to the roughness profile line. Then, silicate cement was cast according to the fracture model. This provides a rough single fracture production method that is simple to produce, convenient to experiment, easy to adjust the fracture roughness and opening, and can more realistically reflect the impact of different fractures on seepage. The method has simple procedures, short production period, high cost-effectiveness, high precision, and strong adaptability.

[0061] The roughness of the roughness profile curve in step 1 is controlled to be 0-20, and its calculation formula is:

[0062] JRC=(2sinθ) 2 / 3 d 1 / 3

[0063] Where θ is the slope angle of the structural surface (in radians), and d is the actual width of the structural surface (in meters).

[0064] Roughness profile curve Roughness refers to the curve characteristics and related parameters obtained through measurement and data processing by specific instruments, which are used to describe the degree of microscopic unevenness of an object's surface. It involves two key concepts, namely surface roughness and profile curve: surface roughness refers to the unevenness of small spacing and tiny peaks and valleys on the machined surface, which belongs to the microscopic geometric shape error; the profile curve is the trajectory curve obtained by scanning the stylus of the roughness measuring instrument within a certain length on the workpiece surface during roughness measurement.

[0065] The model required for the test in step 1 needs to be prepared as a rough surface digital model with a length of 100 mm and a width of 100 mm.

[0066] The digital model of rough surfaces is a tool for digitally characterizing and analyzing actual rough surfaces. I usually use parameters to describe the roughness of the surface. These parameters can be extracted from the digital model and used to evaluate the surface roughness.

[0067] When using the Rhino software in step 2, the three-dimensional fracture model needs to be checked after it is created to determine the quality of the model.

[0068] Use Rhino's analysis tools, such as "ShowEdges" to check whether the model's edges are complete and continuous, and use the "Analyze" tool to check whether the model has overlapping faces, non-manifold edges, and other problems. Fix any problems found in a timely manner to ensure the accuracy and usability of the model.

[0069] The 3D printing software in step 3 uses Cura software, the required temperature of the 3D printer nozzle in step 2 is 210°C, and the required temperature of the hot bed is 60°C.

[0070] Cura software is an open source 3D printing slicing software developed by Ultimaker. It is widely used in the 3D printing field. Its core functions include model processing, slice generation and printer control. It has the advantages of efficient slicing, real-time parameter adjustment, multi-material support, strong compatibility and open source ecology.

[0071] Among them, the specific preparation method of the cylindrical wall in step three is: use Rhino software to create a hollow cylindrical wall with an inner diameter of 100mm and a thickness of 2mm; import the created model into the 3D printing software Cura, and set the printing parameters according to the predetermined parameters; import the set parameters into the 3D printer, return the nozzle and the hot bed to the origin and preheat them to the required printing temperature, and place the PLA material into the printer for printing.

[0072] A 3D printer is a device based on additive manufacturing technology. It converts digital models into physical objects by stacking materials layer by layer. It has the advantages of high customization, flexibility and efficiency, and is widely used in industrial manufacturing, medical care, aerospace, art design and other fields.

[0073] Among them, the cement in step 4 is 42.5R silicate cement with a water-cement ratio of 0.3.

[0074] Portland cement refers to a hydraulic cementitious material made by grinding Portland cement clinker, 0-5% limestone or granulated blast furnace slag, and an appropriate amount of gypsum. It has the characteristics of rapid setting and hardening, high strength, good frost resistance, good wear resistance, and small shrinkage during drying.

[0075] Among them, the specific method for preparing the specimen in step four is: use 42.5R silicate cement to cast the specimen, add 40% of the anti-seepage agent, and the water-cement ratio is 0.3. The material is stirred evenly and the specimen is cast; after the specimen is cast, it is cured in a ventilated place at room temperature for 72 hours and then demolded. The semi-cylinder mold is taken out, and the two parts of the semi-cylinder are combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness, and fixed with tape. After the above operations, 10 single-crack specimens with different roughness are prepared.

[0076] The JRC of single crack specimens is 0-20. During the casting process of the specimen, the position of the cylindrical mold must not change. When pouring the cement material, pay attention to the speed and pour it slowly to avoid the generation of bubbles inside and the formation of pores.

[0077] The specific method of the specimen experiment in step 5 is as follows: open the upper cover of the rock permeability analyzer pressure chamber, make sure the central seal is intact, screw on the bottom cover, put the lower permeable plate on, then put the prepared single-crack cement specimen in, put in the second layer of sealing ring, put in the upper permeable device, screw on the upper cover, tighten the cover screws, and place it in the standard position of the permeability analyzer;

[0078] Connect one end of the outlet pipe on the main unit to the connection of the water permeable device hole on the upper cover with a plastic water pipe, and connect the other end to the water tank of the permeation analyzer to ensure that the water inlet pipe is unobstructed and water flows in normally;

[0079] Connect a hose to the water outlet at the bottom of the main unit and connect it to the two buckets to ensure that there is no water leakage at the water outlet;

[0080] Before starting the test, manually load the confining pressure to 5-7MPa, check whether the oil pressure inside the pressure chamber is stable and there is no oil leakage, ensure that there is sufficient water in the water tank, start the hydraulic pump to apply water pressure, and keep the flow adjustment knob open to fill the pressure chamber with water pressure, and confirm that water flows out of the connecting pipe;

[0081] According to the experimental design, confining pressure and water pressure were applied to single-crack cement specimens with different roughness in sequence. The test time was 520s, and the seepage rate of single-crack cement specimens with different roughness was recorded during the test time.

[0082] After the test, first unload the water pressure, then unload the confining pressure, turn the zero-pressure valve to unload the remaining confining pressure in the pressure chamber, open the upper cover, take out the test piece, and then replace it with a new one. Repeat the above steps and conduct seepage tests on 10 test pieces in sequence.

[0083] Study the correlation between crack opening and crack roughness;

[0084] Based on the experimental data obtained, a scatter plot is drawn with crack opening as the horizontal axis and roughness as the vertical axis to visually observe the distribution trend between the two.

[0085] The Pearson correlation coefficient is used to calculate the correlation between crack roughness and opening, and to determine the strength and direction of the correlation between the two. The specific calculation method is:

[0086]

[0087] In the formula, r is the Pearson correlation coefficient, which ranges from -1 to 1, and x i 、y i represent the experimental values of crack roughness and opening, represent the average values of crack roughness and opening, respectively, and n is the sample size;

[0088] Determination of correlation strength and direction:

[0089] When |r| approaches 1, it indicates that there is a strong linear correlation between crack roughness and aperture. When r approaches 1, it is a strong positive correlation, that is, when the crack roughness increases, the aperture also increases; when r approaches -1, it is a strong negative correlation, that is, when the crack roughness increases, the aperture decreases.

[0090] When 0.7<|r|<1, it indicates that there is a strong correlation between the two;

[0091] When 0.3<|r|<0.7, it indicates that there is a moderate correlation between the two;

[0092] When 0<|r|<0.3, it indicates that there is a weak correlation between the two;

[0093] When |r|≈0, it indicates that there is almost no linear relationship between the two.

[0094] In order to study the seepage characteristics of single fractures with different roughness under different water pressures and confining pressures and avoid the influence of other factors on the test results, no axial load is applied. Under normal circumstances, when the burial depth is 100m, the formation pressure is 0.98MPa, which is approximately equal to 1MPa. Therefore, the confining pressure is selected from 1MPa and gradually increases with 1MPa to 8MPa. The confining pressure values are 1.0MPa, 2.0MPa, 3.0MPa, 4.0MPa, 5.0MPa, 6.0MPa, 7.0MPa, 8.0MPa; water pressure, as the osmotic pressure affecting the inside of the fracture, should not be too large at the beginning of the test. According to the accuracy of the test instrument, 0.4MPa was selected as the initial water pressure, and the water pressure was gradually increased by 0.2MPa. The water pressure values were 0.4MPa, 0.6MPa, 0.8MPa, 1.0MPa, and 1.2MPa. The fracture seepage under different confining pressure and water pressure conditions were measured, and the seepage flowing through the fracture per unit time was obtained.

[0095] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0096] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A rough single fracture seepage simulation and method based on 3D printing, characterized in that: The specific steps are as follows: Step 1: Draw the crack contour curve The model required for the test is a digital model of a rough surface. According to the ten-level standard roughness profile curve proposed by Barton, the specific data of 10 ten-level standard roughness profile curves are obtained and reconstructed in two dimensions in AutoCAD software to obtain 10 10mm two-dimensional roughness curves. Step 2: Create a 3D model of the fracture Ten 10mm long standard contour curves were equally scaled 10 times to 100mm in Rhino software. The accuracy of the scaled standard contour curves remained unchanged, and 10 two-dimensional surfaces of cracks with different roughness were obtained. The height coordinates of each point were input into Rhino software according to the scaled roughness contour curve data to draw each standard contour curve. Then, according to the 10 two-dimensional roughness curves, the peak-to-valley height, spacing and shape of the contour curve were adjusted. The direction perpendicular to the crack surface was selected for non-proportional scaling to change the crack opening. By inputting different scaling ratios, a crack model with adjustable opening can be obtained, which was then created into a semi-cylindrical crack three-dimensional model with a diameter of 100mm, a height of 100mm and a crack of ten levels of roughness. Step 3: 3D printing to make a crack model Import the semi-cylindrical crack 3D model created in step 2 into the 3D printing software, set the printing parameters, and make cylindrical models with different roughness. Import the set printing parameters into the 3D printer, return the nozzle and the hot bed to the origin and preheat them to the required printing temperature, then put the PLA material into the printer for printing to complete the model preparation. After the model preparation is completed, prepare the cylindrical wall surface; Step 4: Casting the crack specimen mold Cement was used as the raw material, 40% of an anti-seepage agent was added, and the materials were stirred evenly before casting the specimens. After casting, the specimens were cured in a ventilated place at room temperature and then demolded. The two semi-cylinders were combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness. The above operation was repeated to prepare 10 single-crack specimens with different roughness at the same opening and 10 single-crack specimens with the same roughness at different openings. The former were the first experimental group, and the latter were the second experimental group. Step 5: Conduct the experiment Seepage tests were carried out on the single-crack specimens in the two experimental groups in turn.

2. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The roughness of the roughness profile curve described in step 1 is controlled to be 0-20, and its calculation formula is: JRC=(2sinθ) 2 / 3 d 1 / 3 Where θ is the slope angle of the structural surface (in radians), and d is the actual width of the structural surface (in meters).

3. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The model required for the test described in step 1 needs to be prepared as a rough surface digital model with a length of 100 mm and a width of 100 mm.

4. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: When using the Rhino software described in step 2, it is necessary to check the fracture 3D model after it is created to determine the quality of the model.

5. The method for rough single fracture seepage simulation based on 3D printing according to claim 1, characterized in that: The 3D printing software described in step 3 is Cura software. The required temperature of the 3D printer nozzle described in step 2 is 210°C, and the required temperature of the hot bed is 60°C.

6. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The specific preparation method of the cylindrical wall described in step 3 is as follows: use Rhino software to create a hollow cylindrical wall with an inner diameter of 100 mm and a thickness of 2 mm; import the created model into the 3D printing software Cura, and set the printing parameters according to the predetermined parameters; import the set parameters into the 3D printer, return the nozzle and the hot bed to the origin and preheat them to the required printing temperature, and place the PLA material into the printer for printing.

7. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The cement described in step 4 is 42.5R Portland cement with a water-cement ratio of 0.

3.

8. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The specific method for preparing the specimen described in step four is: use 42.5R silicate cement to cast the specimen, add 40% of the anti-seepage agent, and the water-cement ratio is 0.

3. Stir the materials evenly and cast the specimen; after the specimen is cast, it is demoulded after curing in a ventilated place at room temperature for 72 hours, and the semi-cylinder mold is taken out. The two parts of the semi-cylinder are combined into a complete cylindrical specimen with a diameter of 100 mm and a height of 100 mm according to the roughness, and fixed with tape. After the above operations, 10 single-crack specimens with different roughness are prepared.

9. The method for simulating seepage in a rough single fracture based on 3D printing according to claim 1, characterized in that: The specific method of the specimen experiment described in step 5 is as follows: open the upper cover of the rock permeability analyzer pressure chamber, make sure the central glue seal is intact, screw on the bottom cover and then put the lower permeable plate on, then put the prepared single-crack cement specimen in, put in the second layer of sealing ring, put in the upper permeable device, screw on the upper cover, tighten the cover screws, and place it in the standard position of the permeability analyzer; Connect one end of the outlet pipe on the main unit to the connection of the water permeable device hole on the upper cover with a plastic water pipe, and connect the other end to the water tank of the permeation analyzer to ensure that the water inlet pipe is unobstructed and water flows in normally; Connect a hose to the water outlet at the bottom of the main unit and connect it to the two buckets to ensure that there is no water leakage at the water outlet; Before starting the test, manually load the confining pressure to 5-7MPa, check whether the oil pressure inside the pressure chamber is stable and there is no oil leakage, ensure that there is sufficient water in the water tank, start the hydraulic pump to apply water pressure, and keep the flow adjustment knob open to fill the pressure chamber with water pressure, and confirm that water flows out of the connecting pipe; According to the experimental design, confining pressure and water pressure were applied to single-crack cement specimens with different roughness in sequence. The test time was 520s, and the seepage rate of single-crack cement specimens with different roughness was recorded during the test time. After the test, the water pressure was first unloaded, followed by the confining pressure. The zero-pressure valve was turned to unload the remaining confining pressure in the pressure chamber. The upper cover was opened, the specimen was taken out, and a new specimen was replaced. The above steps were repeated. Seepage tests were carried out on 10 specimens in the two experimental groups in turn to study the correlation between fracture aperture and fracture roughness. Based on the experimental data obtained, a scatter plot is drawn with crack opening as the horizontal axis and roughness as the vertical axis to visually observe the distribution trend between the two. The Pearson correlation coefficient is used to calculate the correlation between crack roughness and opening, and to determine the strength and direction of the correlation between the two. The specific calculation method is: In the formula, r is the Pearson correlation coefficient, which ranges from -1 to 1, and x i 、y i represent the experimental values of crack roughness and opening, represent the average values of crack roughness and opening, respectively, and n is the sample size; Determination of correlation strength and direction: When |r| approaches 1, it indicates that there is a strong linear correlation between crack roughness and aperture. When r approaches 1, it is a strong positive correlation, that is, when the crack roughness increases, the aperture also increases; when r approaches -1, it is a strong negative correlation, that is, when the crack roughness increases, the aperture decreases. When 0.7<|r|<1, it indicates that there is a strong correlation between the two; When 0.3<|r|<0.7, it indicates that there is a moderate correlation between the two; When 0<|r|<0.3, it indicates that there is a weak correlation between the two; When |r|≈0, it indicates that there is almost no linear relationship between the two.

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