A rock structure surface reconstruction and carving method based on 3D carving technology

Abstract

The present invention provides a rock structural surface reconstruction and carving method based on 3D carving technology, including acquisition of structural surface point cloud morphological data; generation of reconstructed structural surface carving path; selection of reconstructed structural surface carving parameters, selection of appropriate tools and determination of appropriate carving path spacing, and carving; evaluation of reconstructed structural surface carving accuracy, judging whether the reconstructed structural surface and the original structural surface morphology are highly consistent, if the accuracy is low, the carving parameters can be adjusted until the morphological error between the reconstructed structural surface and the original structural surface is within an allowable threshold. The rock structural surface reconstruction and carving method based on 3D carving technology provided by the present invention can overcome the drawbacks of existing structural surface sampling difficulties, the inability of preparation technology to reproduce the morphological characteristics of natural structural surfaces with high precision, and thus the inability to reflect the anisotropy of shear mechanical behavior of natural rock structural surfaces, and can accurately reconstruct the corresponding rock structural surface.

Description

Technical Field

[0001] The present invention relates to the field of rock mechanics and engineering technology, and in particular to a rock structure surface reconstruction and carving method based on 3D carving technology. Background Art

[0002] In order to better study the roughness and shear mechanical behavior of natural rock structural surfaces, the controlled variable method is generally used in direct shear tests. In particular, a large number of structural surface samples with the same lithology, surface morphology and mechanical properties are required to study the anisotropic characteristics of structural surfaces. Currently, there are four main methods for reconstructing rock structural surfaces in indoor tests: (1) on-site acquisition of structural surfaces; (2) artificial splitting; (3) artificial casting; and (4) 3D printing.

[0003] Among them, on-site sampling can easily cause damage to the surface morphology of the structural surface and poor fit between the upper and lower plates of the structural surface during the sampling process, and its sampling cycle is long and the cost is high, the sampling is difficult, the success rate is low, and it is impossible to obtain a large number of original rock structural surface samples with the same morphology; the artificial splitting method uses the Brazilian splitting method to obtain the structural surface, because its formation mechanical reason is only a single tensile failure, its morphological characteristics are quite different from the natural structural surface, and its roughness range varies little, and it is very different from the natural structural surface in anisotropy, and the operation is cumbersome and the repeatability is poor, and it is impossible to obtain a large number of original rock structural surface samples with the same morphology; in the artificial casting method, the rock matrix is ​​mostly cast with rock-like materials, and its mechanical properties are quite different from those of natural rocks. The test results cannot truly reflect the mechanical properties of natural structural surfaces; the 3D printing method has the disadvantages of high cost, complex operation, significant layered phenomenon, and the mechanical properties of the printed material are quite different from those of natural rocks. Summary of the invention

[0004] The purpose of the present invention is to provide a rock structural surface reconstruction and carving method based on 3D carving technology, which can overcome the difficulties in existing structural surface sampling and preparation technology, the inability to simulate the structural surface morphology characteristics with high precision, and the inability to reflect the mechanical anisotropic properties of natural rock structural surfaces, and can reconstruct natural rock structural surface samples with high precision on natural rocks.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A rock structure surface reconstruction and carving method based on 3D carving technology comprises the following steps:

[0007] Step 1: Acquisition of structural surface point cloud morphology data;

[0008] Step 2: Generate carving path of reconstructed structural surface;

[0009] Step 3: Select the parameters for reconstructing the structural surface engraving, including selecting a suitable tool and determining a suitable engraving path spacing for engraving;

[0010] Step 4: Evaluate the engraving accuracy of the reconstructed structural surface to determine whether the reconstructed structural surface is highly consistent with the original structural surface morphology. If not, jump to step 3 to change the tool and / or path spacing until the error between the reconstructed structural surface and the original structural surface morphology is within the allowable threshold.

[0011] Furthermore, the step 1 specifically includes:

[0012] Step 101, use a brush to gently clean the debris and mud particles on the surface of the rock structure surface to be scanned, to prevent the debris from covering the subtle undulations of the rock structure surface, paste marker points 2 around the scanning area, and realize automatic intelligent splicing of multi-point cloud data. During the scanning process, rotate the scanning angle or perform multiple scans to splice and synthesize a complete structure surface;

[0013] Step 102: After scanning, a large amount of natural rock joint point cloud data is obtained, and the point cloud data is denoised, optimized and meshed through post-processing software.

[0014] Furthermore, the step 2 specifically includes:

[0015] Step 201: intercept the engraving area of ​​the structural surface morphology point cloud data obtained in step 1 according to the test purpose. When intercepting the structural surface, try to select an area that can represent the morphological characteristics of the structural surface, and then perform the best fitting on the intercepted structural surface;

[0016] Step 202: Use engraving path making software to make NC codes that can be recognized by the engraving machine, select the tool path in the engraving process and generate the engraving path.

[0017] Furthermore, the step 3 specifically includes:

[0018] Step 301: During processing, the tool is always set in a vertical direction, and a suitable tool is selected according to the strength and composition of the rock to be engraved, and a suitable tool radius is selected without causing the tool to break;

[0019] Step 302: determine a suitable engraving path spacing, and perform engraving on the structural surface on an engraving machine.

[0020] Furthermore, in step 301, a ball-end tool is selected as a tool for engraving the structural surface, and the ball-end tool includes a handle and a blade arranged in sequence from top to bottom, the bottom of the blade is a tool head, and the tool head is arc-shaped.

[0021] Furthermore, the residual area height h is:

[0022] h≈r-[r 2 -(e / 2) 2 ] 1 / 2 (1)

[0023] Among them, r and e are the tool head radius and path spacing respectively;

[0024] There is usually an overlapping area between adjacent paths, and the overlap rate r overlay The relationship with the path spacing e is as follows:

[0025] e=2r×(1.0-r overlay / 100) (2)

[0026] When the residual area height h is too high, reduce the path spacing; when the overlap rate r overlay Too high, reduce the tool tip radius or increase the path spacing.

[0027] Furthermore, a circle is drawn with the radius of the tool handle as the center of any engraving point in the point cloud data generated by engraving, and the distance D between other engraving points within the circle and the center engraving point is calculated. d , get the height difference h between other engraving points and the central engraving point d , D d With h d After comparison, it is compared with the cone angle of the blade, and the calculation formula is:

[0028] D d / h d ≥AB / BC (3)

[0029] Among them, AB is the difference between the handle radius and the cutter head radius, and BC is the blade length;

[0030] If formula (3) is satisfied, it is considered that there is interference between the two engraving points, and the tool handle radius is reduced or the path spacing is increased. If formula (3) is not satisfied, the two engraving points do not interfere with each other and engraving can be performed.

[0031] Furthermore, two-dimensional contour comparison is used for evaluation, and multiple contours are extracted from the reconstructed structural surface at equal intervals and multiple contours are extracted from the corresponding positions of the original structural surface to perform contour morphology comparison analysis.

[0032] Furthermore, a three-dimensional roughness characterization method is used for evaluation, and the surface morphology of the reconstructed structural surface is quantitatively determined from various directions based on the three-dimensional roughness.

[0033] Furthermore, the three-dimensional roughness parameters proposed by Grasselli and Tatone that can characterize the anisotropy of the roughness of the structural surface are used to calculate the roughness parameters of the original structural surface and the reconstructed structural surface respectively. The specific algorithm is as follows: the Y positive axis direction is the due north direction (90°), the X positive axis direction is the due east direction (0°), and the Z positive axis direction is vertically upward. Multiple shear directions are selected at a certain angle evenly spaced from 0° to 360°, and the roughness values ​​in different shear directions can be calculated.

[0034] The sampling Delaunay triangulation algorithm discretizes the joint surface point cloud data into a large number of triangular joint elements, and approximates the real joint surface through these triangular elements. According to geometric analysis, there is the following relationship between the apparent inclination angle and shear direction of each triangular element:

[0035] tanθ * = -tanθ·cosα (4)

[0036] Among them, α is the azimuth, θ is the inclination angle of the triangle element, and θ * is the apparent inclination angle of the triangle element;

[0037] The following relationship is used to describe the functional relationship between the contact area ratio and the critical apparent inclination angle:

[0038]

[0039] in, is the maximum apparent inclination angle, C is the fitting parameter; The critical apparent inclination angle is θ * A0 is the contact area ratio when the critical apparent inclination angle is 0°;

[0040] By performing definite integration on formula (5), we can obtain:

[0041]

[0042] use It indicates the roughness of the structural surface along the shear direction. Formula (6) can be used as the roughness calculation formula to express the anisotropy of the structural surface roughness.

[0043] The roughness in each shear direction is calculated separately, and the roughness of the engraved structural surface is compared with the roughness of the original structural surface. If the error is within the allowable threshold, it is considered that the engraved structural surface has a high degree of consistency with the original structural surface when evaluated in terms of roughness.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] The present invention provides a rock structural surface reconstruction and carving method based on 3D carving technology, which can process natural rocks, accurately obtain the characteristics of the structural surface by acquiring structural surface point cloud data, generate a reconstructed structural surface carving path according to the structural surface morphology characteristics, select a suitable tool and perform carving, and finally evaluate the carving accuracy of the reconstructed structural surface. The sampling cycle is short, the cost is low, the sampling difficulty is relatively small, the success rate is relatively high, and the natural structural surface samples of the same morphology can be reconstructed in batches on natural rocks. The operation is simple and the repeatability is good. The method can truly reflect the mechanical properties of natural rocks and natural structural surfaces, and can overcome the difficulties in existing structural surface sampling and the shortcomings of the preparation technology that cannot simulate the structural surface morphology characteristics with high precision and cannot reflect the anisotropy of the mechanical properties of the natural rock structural surface, and can reconstruct natural rock structural surface samples with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Reconstruct the flow chart for the structural surface.

[0047] Figure 2 This is a schematic diagram of the structural surface scanning.

[0048] Figure 3 Schematic diagram of the structural surface carving path.

[0049] Figure 4 Schematic diagram of a tapered ball-end cutter.

[0050] Figure 5 Schematic diagram of the relationship between the residual area height and the path spacing.

[0051] Figure 6 Schematic diagram of the relationship between overlap rate and path spacing.

[0052] Figure 7 This is a schematic diagram of the mutual interference of engraving paths when the path spacing is too small.

[0053] Figure 8 Schematic diagram of interference calculation principle.

[0054] Fig. 9 is the three-dimensional roughness parameter of the triangulated structural surface Simplified diagram of the calculation.

[0055] Fig.10 Comparison diagram of the two-dimensional contour lines of the original structural surface and the reconstructed structural surface.

[0056] Fig.11 This is a comparison chart of the three-dimensional roughness of the original structural surface and the reconstructed structural surface.

[0057] Among them, 1. rock structure surface; 2. marking point; 3. starting coordinate axis; 4. engraving path; 5. path spacing; 6. tool handle; 7. blade; 8. tool head; 9. tool; 10. engraving sample. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0059] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0060] A rock structure surface reconstruction and carving method based on 3D carving technology, such as Figure 1-Figure 4 As shown, engraving is performed on the engraving sample 10, including the following steps:

[0061] Step 1, obtaining the structural surface point cloud morphology data of the engraving sample 10;

[0062] Step 2, reconstructing the structural surface engraving path 4 to generate;

[0063] Step 3, reconstructing the structural surface engraving parameter selection, selecting a suitable tool 9 and determining a suitable engraving path spacing 5, and engraving the engraving sample 10;

[0064] Step 4, evaluate the engraving accuracy of the reconstructed structural surface to determine whether the reconstructed structural surface is highly consistent with the original structural surface morphology. If not, jump to step 3 and change the tool 9 and / or path spacing 5 until the error between the reconstructed structural surface and the original structural surface morphology is within the allowable threshold.

[0065] The present invention provides a high-precision reconstruction and engraving method for rock structural surfaces based on 3D engraving technology, which can replicate natural structural surface samples with high precision, obtain natural structural surface point cloud data through a three-dimensional laser scanner, generate a reconstructed structural surface engraving path 4 according to the structural surface point cloud data, select a suitable tool 9 and perform engraving, and finally evaluate the engraving accuracy of the reconstructed structural surface. The method has low cost, can produce a large number of natural structural surface samples with the same morphology, is simple to operate and has good repeatability, can truly reflect the physical and mechanical properties of natural structural surfaces, can overcome the difficulties in sampling existing structural surfaces and the shortcomings of the preparation technology that cannot restore the structural surface morphological characteristics with high precision and cannot reflect the mechanical anisotropic properties of the natural rock structural surface, and can accurately reconstruct the corresponding rock structural surface 1.

[0066] like Figure 1 and Figure 2 As shown, the step 1 specifically includes:

[0067] Step 101, use a brush to gently clean the debris and mud particles on the surface of the rock structure surface 1 to be scanned, so as to prevent the debris from covering the fine undulations of the rock structure surface 1, and paste marker points 2 around the scanning area to realize automatic intelligent splicing of multi-point cloud data. During the scanning process, the scanning angle is rotated or multiple scans are performed to splice and synthesize a complete structure surface;

[0068] Step 102: After scanning, a large amount of point cloud data of natural rock joints is obtained, and the point cloud data is denoised, optimized, and meshed.

[0069] The scanner used is a handheld 3D laser scanner, model Freescan X3, and the post-processing software for denoising, optimizing and mesh repairing point cloud data is Geomagic studio.

[0070] During the marking process of structural surface marking point 2, the spacing between marking points 2 cannot be too large, otherwise the rock structural surface information cannot be accurately obtained. At the same time, the spacing between marking points 2 cannot be too small, otherwise the morphological information of the rock structural surface 1 will be blocked. The spacing between marking points 2 ranges from 10 to 15 cm.

[0071] like Figure 3 As shown, the step 2 specifically includes:

[0072] Step 201: using the structural surface morphology point cloud data obtained in step 1, intercepting a carving area according to the test purpose, when intercepting the carving area, try to select a structural surface that can represent the structural surface morphology characteristics, and then perform best fitting on the intercepted structural surface of the carving area;

[0073] Step 202: Use the engraving path 4 production software to produce an NC code that can be recognized by the engraving machine, select the tool path method in the engraving process and generate the engraving path 4.

[0074] In the embodiment of the present invention, JD Paint is selected as the engraving path 4 production software.

[0075] like Figure 3-Figure 8 As shown, the step 3 specifically includes:

[0076] Step 301: During processing, the tool 9 is always set in a vertical direction. According to the strength and composition of the rock to be engraved, a suitable tool 9 is selected, and a suitable radius of the tool 9 is selected without causing the tool to break;

[0077] Step 302: determine a suitable engraving path spacing 5, start from the starting coordinate axis 3, and perform engraving of the structural surface on the engraving machine.

[0078] Since natural rocks usually have complex structural surfaces and require high carving accuracy, in the present invention, in step 301, a ball-end cutter is selected as the tool 9 for carving the structural surface. The ball-end cutter includes a handle 6 and a blade 7 arranged in sequence from top to bottom. The bottom of the blade 7 is a cutter head 8, and the cutter head 8 is arc-shaped. A suitable radius of the cutter head 8 is selected during processing.

[0079] When the ball end tool is processing, the tool handle 6 is always set in the vertical direction, and a point on the tool head 8 contacts the processing surface without sudden changes. The cutting force changes continuously and steadily, which is conducive to ensuring the surface processing quality. The actual engraving diameter is smaller than the diameter of the tool handle 6, and the contact part of the tool head 8 with the workpiece is smaller than the diameter of the tool head 8. The processing accuracy is high and the surface residue is small.

[0080] In the present invention, CNC numerical control engraving technology is used to control the ball head. CNC numerical control engraving technology integrates computer-aided technology, numerical control technology, image processing technology and precision manufacturing, and has a high degree of integration. Highly automated, driven by a servo motor, the XYZ three-axis ball screw moves along a predetermined engraving path 4, the tool handle 6 in the ball-end tool is fixed on the Z axis by a collet, and the tool handle 6 always moves up and down in the vertical direction, and the direction remains unchanged during the entire cutting path.

[0081] When determining the engraving radius of a ball-end tool, the selection principle is that the tool should not break frequently during the engraving process, such as Figure 4 As shown, the smaller the radius of the tool 9 is, the better without affecting the engraving efficiency, that is, the smaller the radius of the tool head 8 is, the better. In addition, in order to avoid the breakage of the tool 9 and frequent tool changes during the engraving process, a ball-end tool with diamond-grit added to the blade 7 is selected.

[0082] like Figure 5 As shown, in step 302, when the engraving path spacing 5 is large, some rock sample areas cannot be engraved, and the height h of the remaining area is:

[0083] h≈r-[r2 -(e / 2) 2 ] 1 / 2 (1)

[0084] Among them, r and e are the radius of the cutter head 8 and the path spacing 5 respectively;

[0085] like Figure 6 As shown, adjacent paths with a spacing of 5 usually have an overlapping area, and the relationship between the overlap rate and the path spacing 5 is as follows:

[0086] e=2r×(1.0-r overlay / 100) (2)

[0087] Among them, r overlay is the overlap ratio, r is the diameter of the cutter head 8;

[0088] Obtain the overlap rate r based on the radius of the tool head 8 and the path spacing 5 overlay and the residual area height h;

[0089] In principle, the smaller the residual area height and overlap rate, the higher the engraving accuracy. When the residual area height h is too high, the unengraved area between adjacent engraving paths is wider, that is, the path spacing 5 is larger; the overlap rate r overlay When it is too high, it is easy to cause excessive engraving of the adjacent path spacing 5, so it is necessary to select a suitable engraving path parameter combination.

[0090] Therefore, in the present invention, when the residual area height h is too high, the path spacing 5 is reduced; when the overlap rate r overlay Too high, reduce the radius of the cutter head 8 or increase the path spacing 5.

[0091] The path spacing 5 and the overlap rate are interlocked and are mainly used to control the lateral feed amount. The path spacing 5 is numerically equal to the lateral feed amount. The overlap rate indicates the degree of repetition between two adjacent paths. The higher the overlap rate, the smaller the path spacing 5 and the denser the paths.

[0092] Since the path spacing 5 is set, the larger the radius of the cutter head 8, the smaller the height of the uncarved area, and the less time it takes to carve. If the radius of the cutter head 8 is too large, it is impossible to carve fine information on the structural surface. If the radius of the cutter head 8 is smaller, the tool 9 is very easy to break during the engraving process, which seriously reduces the engraving efficiency. Therefore, the smaller the radius of the cutter head 8 is, the better without affecting the engraving efficiency.

[0093] If the path spacing 5 is too small, some problems may occur. When the tool 9 engraves the path 4, if the engraved path spacing 5 is too small, the tool 9 may damage the engraved surface.

[0094] The present invention proposes a method for evaluating the interference of engraving points, which can determine whether two engraving points interfere with each other, and further help select a suitable tool 9 radius and path spacing 5.

[0095] A method for evaluating the interference of engraving points, such as Figure 8 As shown, a circle is drawn with the radius of the handle 6 of the tool 9 as the center of the engraving point in the point cloud data generated by engraving, and the distance D between other engraving points within the circle and the center engraving point is calculated. d , get the height difference h between other engraving points and the central engraving point d , D d With h d After comparison, it is compared with the cone angle of tool 9.

[0096] The comparison calculation formula is:

[0097] D d / h d ≥AB / BC (3)

[0098] Among them, D d is the distance between other engraving points and the central engraving point, h d is the height difference between the other engraving points and the central engraving point, AB is the difference between the radius of the tool handle 6 and the radius of the tool head 8, and BC is the length of the blade 7;

[0099] If formula (3) is satisfied, it is considered that there is interference between the two engraving points, and the radius of the tool handle 6 is reduced or the path spacing 5 is increased. If formula (3) is not satisfied, the two engraving points do not interfere with each other and engraving can be performed.

[0100] In the present invention, the calculation software in the above-mentioned path spacing 5 interference evaluation is Matlab software.

[0101] In step 4, the carving accuracy of the reconstructed structural surface is evaluated. The point cloud data of the surface morphology of the rock three-dimensional structural surface sample reconstructed in step 3 is obtained through three-dimensional laser scanning, and compared with the original structural surface morphology point cloud data obtained in step 1. At the same time, two-dimensional contour line comparison and three-dimensional roughness characterization methods are used to evaluate the carving accuracy of the reconstructed structural surface, and decide whether re-carving is needed based on the test requirements.

[0102] Specifically, a three-dimensional laser scanning system is used to scan and obtain the point cloud data of the carved structure surface. Since the reference coordinate system of each sample point cloud is different, it is necessary to use the point cloud registration method to adjust these point clouds to a common coordinate system, and then use the two-dimensional contour line comparison and three-dimensional roughness characterization method to evaluate the difference between the carved structure surface and the original structure surface.

[0103] In order to avoid the randomness of the extracted contour roughness results during the two-dimensional structural surface contour comparison process, two-dimensional contour comparison is used for evaluation. Multiple contour lines are extracted from the reconstructed structural surface at equal intervals and from the corresponding positions of the original structural surface to perform contour morphology comparison analysis.

[0104] The three-dimensional roughness characterization method is used for evaluation, and the surface morphology of the reconstructed structural surface is quantitatively determined from all directions based on the three-dimensional roughness.

[0105] Specifically, the three-dimensional roughness parameter θ proposed by Grasselli and Tatone can characterize the anisotropy of structural surface roughness. * / (C+1) respectively calculates the roughness parameters of the original structural surface and the engraved reconstructed structural surface. The specific algorithm is: the Y positive axis direction is the due north direction (90°), the X positive axis direction is the due east direction (0°), and the Z positive axis direction is vertically upward. Select multiple shear directions at a certain angle evenly spaced from 0° to 360°, and the roughness values ​​in different shear directions can be calculated.

[0106] like Fig. 9 As shown in the figure, the Delaunay triangulation algorithm is used to discretize the joint surface point cloud data into a large number of triangular joint elements. These triangular elements are used to approximate the real joint surface. According to geometric analysis, there is the following relationship between the apparent inclination angle and the shear direction of each triangular element:

[0107] tanθ * = -tanθ·cosα (4)

[0108] Among them, α is the azimuth, θ is the inclination angle of the triangle element, and θ * is the apparent inclination angle of the triangle element.

[0109] like Fig.10 As shown in the figure, for any given critical apparent inclination angle, the contact area ratio of the joint micro-element whose apparent inclination angle is greater than the critical apparent inclination angle can be calculated. Then, given different critical apparent inclination angles in turn, the corresponding contact area ratio can be obtained. The following relationship is used to describe the functional relationship between the contact area ratio and the critical apparent inclination angle:

[0110]

[0111] in, is the maximum apparent inclination angle, C is the fitting parameter; The critical apparent inclination angle is θ * A0 is the contact area ratio when the critical apparent inclination angle is 0°.

[0112] Then, we perform definite integration on formula (5) to obtain:

[0113]

[0114] use It represents the roughness of the structural surface along the shear direction. Formula (6) can be used as the roughness calculation formula to represent the anisotropy of the structural surface roughness.

[0115] This formula can be used to calculate the roughness in different shear directions, and compare the roughness of the carved structural surface with that of the original structural surface. If the error is within the allowable threshold, it is considered that the carved structural surface has a high degree of consistency with the original structural surface when evaluated in terms of roughness.

[0116] In one embodiment of the present invention, a method for reconstructing a rock structure surface 1 based on 3D engraving technology on a natural rock mass in the wild includes the following specific implementation steps:

[0117] Step 1: Select a structural surface on a natural rock mass in the wild, and use a brush to gently clean the debris and mud particles on the surface of the rock structural surface 1 to be scanned to prevent the debris from covering the subtle undulations of the rock structural surface 1. Then, mark points are placed on the structural surface. The distance between adjacent marking points 2 is about 10 to 15 cm. Use a handheld 3D laser scanner Freescan X3 to scan the structural surface. The scanner sampling interval is 0.20 mm. During the scanning process, slowly move the scanner position until the entire scanning area is scanned. Then import the collected structural surface point cloud data into Geomagic studio to denoise, optimize and mesh the point cloud.

[0118] Step 2: The structural surface morphology point cloud data obtained in step 1 is used to intercept the engraving area according to the test purpose. The intercepted area is a 100mm×100mm square. The area is selected as the center of the scanning area, and then the intercepted structural surface is best fitted. After that, the engraving path 4 production software JD Paint is used to make it into an NC code that can be recognized by the engraving machine. The tool path method in the engraving process is selected and the engraving path 4 is generated.

[0119] Step 3, the rock of the engraved structural surface is sandstone, the main components of which are quartz (~62%), feldspar (~18%) and calcite (~13%), the particle size range is mainly 0.02~0.35mm, the uniaxial compressive strength is 48.37MPa, and the elastic modulus is 13.09GPa. A ball-end cutter is selected as the tool 9 for engraving the structural surface. The taper ball-end cutter length is about 46mm, the frosting length is 16mm, the handle radius is 3.0mm, the tool head 8 radius is 0.30~0.50mm, and the taper angle is about 4°. Tools 9 with tool head 8 radii of 0.30mm, 0.40mm and 0.50mm were used for engraving respectively. The tool head 8 with a radius of 0.3mm often broke during engraving, while the tool head 8 with a radius of 0.40mm did not break during engraving, so the radius of tool 9 was selected to be 0.40mm;

[0120] After the radius of the cutter head 8 is selected as 0.40mm, 8 engraving path spacings 5 ​​are set, which are 0.05mm, 0.08mm, 0.10mm, 0.20mm, 0.30mm, 0.40mm, and 0.50mm. When the path spacing 5 is greater than 0.20mm, there is an unengraved area before the adjacent engraving path 4, so the path spacing 5 cannot be greater than 0.20mm. Then, the path spacing 5 is calculated in Matlab using formula 3 when it is 0.05mm, 0.08mm, and 0.10mm. The results show that when the path spacing 5 is 0.05mm and 0.08mm, interference occurs. Therefore, the path spacing 5 is selected as 0.10mm. Then, the structural surface is engraved on the engraving machine. In this study, a 3-axis CNC machine tool is used, which is mainly composed of a control plane, a spindle, and a workbench. The machine tool is controlled by a servo system and has high X, Y, and Z axis transmission accuracy, high positioning accuracy (0.05mm) and processing accuracy (0.01mm).

[0121] Step 4: Since the point cloud data directly obtained by laser scanning is an irregularly distributed point cloud, the positive direction of the X-axis is 0°, and the profile contour line is intercepted every 30° clockwise (the highest point is set to 0mm). The profile is compared with the same position of the original structural surface. The results show that the reconstructed structural surface can better carve the contour line. Fig.10 As shown;

[0122] Then, the three-dimensional roughness is used to quantitatively evaluate the consistency of the surface morphology of the reconstructed structural surface with the original structural surface from all directions, such as Fig.11 As shown, the roughness of the carved and reconstructed structural surface is consistent with that of the original structural surface, and the reconstructed structural surface is sufficient to represent the original structural surface, indicating that the carving parameter selection method for the carved structural surface proposed in the present invention is accurate and effective, and the reconstructed structural surface has high accuracy and can meet the requirements of indoor experimental research.

[0123] In summary, compared with the prior art, the present invention proposes a rock structural surface reconstruction carving method based on 3D carving technology, and provides a carving point interference evaluation method. The carving parameter evaluation method is simple in calculation and highly efficient, and realizes accurate selection of structural surface reconstruction carving parameters, overcoming the shortcomings of the existing 3D carving technology that cannot effectively determine the carving parameters, resulting in poor carving accuracy of the reconstructed structural surface, so that the subtle undulations contained in the structural surface can be accurately reconstructed, and the surface morphology feature information of the original rock structural surface can be restored to the greatest extent, ensuring the reconstruction accuracy of the structural surface. The method of the present invention clearly proposes a method for selecting the radius of the cutter head 8 and the path spacing 5, avoiding a large number of pre-carving tests when selecting the radius of the cutter head 8 and the path spacing 5, and avoiding frequent replacement of the tool 9 during the carving process, greatly saving the time and economic cost of the structural surface reconstruction process. In addition, according to the method of the present invention, the three-dimensional structural surface of rocks can be quickly and efficiently reconstructed in batches indoors, overcoming the shortcomings of the original structural surface shear test that cannot be repeated due to the destructiveness of the structural surface shear test.

[0124] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A rock structure surface reconstruction and carving method based on 3D carving technology, characterized by: The following steps are involved: Step 1: Acquisition of structural surface point cloud morphology data; Step 101, use a brush to gently clean the debris and mud particles on the surface of the rock structure surface to be scanned, to prevent the debris from covering the subtle undulations of the rock structure surface, paste marker points around the scanning area, and realize automatic intelligent splicing of multi-point cloud data. During the scanning process, rotate the scanning angle or perform multiple scans to splice and synthesize a complete structure surface; Step 102: After scanning, a large amount of natural rock joint point cloud data is obtained, and the point cloud data is denoised, optimized, and meshed by post-processing software; Step 2: Generate carving path of reconstructed structural surface; Step 201: intercepting the engraving area of ​​the structural surface morphology point cloud data obtained in step 1 according to the test purpose, selecting the area representing the morphological characteristics of the structural surface when intercepting the structural surface, and then performing the best fitting on the intercepted structural surface; Step 202: Use engraving path making software to make NC code recognized by the engraving machine, select the tool path in the engraving process and generate the engraving path; Step 3: Select the parameters for reconstructing the structural surface engraving, including selecting a suitable tool and determining a suitable engraving path spacing for engraving; Step 4: Evaluate the carving accuracy of the reconstructed structural surface. The evaluation method is as follows: Evaluation was performed using two-dimensional contour line comparison, where multiple contour lines were extracted from the reconstructed structural surface at equal intervals and multiple contour lines were extracted from the corresponding positions of the original structural surface to conduct contour line morphology comparison analysis; The three-dimensional roughness characterization method is used for evaluation, and the surface morphology of the reconstructed structural surface is quantitatively determined from all directions based on the three-dimensional roughness. Determine whether the reconstructed structural surface and the original structural surface morphology are highly consistent. If not, jump to step 3 to change the tool and / or path spacing until the error between the reconstructed structural surface and the original structural surface morphology is within the allowable threshold.

2. The rock structure surface reconstruction and carving method based on 3D carving technology according to claim 1 is characterized in that: The step 3 specifically includes: Step 301: During processing, the tool is always set in a vertical direction, and a suitable tool is selected according to the strength and composition of the rock to be engraved, and a suitable tool radius is selected without causing the tool to break; Step 302: determine a suitable engraving path spacing, and perform engraving on the structural surface on an engraving machine.

3. The rock structure surface reconstruction and carving method based on 3D carving technology according to claim 2 is characterized by: In step 301, a ball-end tool is selected as a tool for engraving the structural surface. The ball-end tool includes a handle and a blade arranged in sequence from top to bottom. The bottom of the blade is a tool head, and the tool head is arc-shaped.

4. The rock structure surface reconstruction and carving method based on 3D carving technology according to claim 3 is characterized by: The height h of the residual area is: h≈r-[r 2 -(e / 2) 2 ] 1 / 2 (1) Where r and e are the tool head radius and path spacing, respectively; There is an overlapping area between adjacent paths, and the overlap rate r overlay The relationship with the path spacing e is as follows: e＝2r×(1.0-r overlay / 100) (2) When the residual area height h is too high, reduce the path spacing; when the overlap rate r overlay Too high, reduce the tool tip radius or increase the path spacing.

5. The rock structure surface reconstruction and carving method based on 3D carving technology according to claim 4 is characterized by: Take any point in the point cloud data generated by engraving as the center, make a circle with the radius of the tool handle, and calculate the distance D between other engraving points within the circle and the center engraving point d , get the height difference h between other engraving points and the central engraving point d , D d With h d After comparison, it is compared with the cone angle of the blade, and the calculation formula is: D d / h d ≥AB / BC (3) Where AB is the difference between the shank radius and the cutter head radius, and BC is the blade length; If formula (3) is satisfied, it is considered that there is interference between the two engraving points, and the tool handle radius is reduced or the path spacing is increased. If formula (3) is not satisfied, the two engraving points do not interfere with each other and engraving can be performed.

6. The rock structure surface reconstruction and carving method based on 3D carving technology according to claim 1 is characterized by: The roughness parameters of the original structural surface and the reconstructed structural surface are calculated using the three-dimensional roughness parameters proposed by Grasselli and Tatone to characterize the anisotropy of the structural surface roughness. The specific algorithm is as follows: the Y positive axis direction is the due north direction, the X positive axis direction is the due east direction, and the Z positive axis direction is vertically upward. Multiple shear directions are selected at a certain angle evenly spaced from 0° to 360°, and the roughness values ​​in different shear directions can be calculated. The sampling Delaunay triangulation algorithm discretizes the joint surface point cloud data into a large number of triangular joint elements, and approximates the real joint surface through these triangular elements. According to geometric analysis, there is the following relationship between the apparent inclination angle and shear direction of each triangular element: tanθ * =-tanθ·cosα (4) Among them, α is the azimuth, θ is the inclination angle of the triangle element, and θ * is the apparent inclination angle of the triangle element; The following relationship is used to describe the functional relationship between the contact area ratio and the critical apparent inclination angle: in, is the maximum apparent inclination angle, C is the fitting parameter; The critical apparent inclination angle is θ * A0 is the contact area ratio when the critical apparent inclination angle is 0°; By performing definite integration on formula (5), we can obtain: use It indicates the roughness of the structural surface along the shear direction. Formula (6) can be used as the roughness calculation formula to express the anisotropy of the structural surface roughness. The roughness in each shear direction is calculated separately, and the roughness of the engraved structural surface is compared with the roughness of the original structural surface. If the error is within the allowable threshold, it is considered that the engraved structural surface has a high degree of consistency with the original structural surface when evaluated in terms of roughness.

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