Core fracture surface short-distance measuring device and measuring method thereof

Abstract

The invention relates to a rock core fissure surface short-distance measuring device and a measuring method thereof, the rock core fissure surface short-distance measuring device comprises a mounting seat and a frame body arranged on the mounting seat, a guide rail is arranged on the frame body, and a camera and a line laser projector are slidably arranged on the guide rail; a rotary table for bearing a rock core is arranged in the mounting seat, racks driven by a gear are arranged above the rotary table, the racks are symmetrically arranged on the two sides of the rock core, and a wire contact type roughness measuring instrument is also arranged in the mounting seat. According to the invention, a continuous morphology curve obtained by a high-precision contact probe is used as a space reference, and combined registration and system external parameter self-calibration are carried out on multi-angle discrete point clouds obtained through linear laser rotation scanning. According to the method, geometric prior constraints are introduced, so that the problems of accumulative drifting and splicing dislocation caused by mechanical errors in traditional rotary scanning are solved, and integrated and high-precision synchronous measurement of the three-dimensional shape, the inclination angle and the roughness of the rock core fracture surface is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geological exploration and geotechnical engineering, and more particularly to a core fracture surface near distance measuring device and a measuring method thereof. BACKGROUND

[0002] In the field of municipal, traffic, water conservancy and other geotechnological engineering investigation, the drilling core as a direct carrier reflecting the characteristics of underground rock mass, the geological information contained therein plays a decisive role in engineering design and safety evaluation. Among them, the properties of core fracture surface (such as dip angle, surface morphology, etc.) are the key basis for analyzing rock mass structure, judging rock mass integrity and special geological phenomena (such as karst development). The source of core fracture surface is complex and diverse, covering natural structural planes of rock mass (such as bedding, joints, dissolution fractures, stress release, etc.) and artificially formed fracture surfaces (such as fracture surfaces generated by mechanical impact during drilling). The characteristics of fracture surfaces of different sources are directly related to the core evaluation indexes such as rock mass mechanical properties and karst development degree. However, in the current engineering investigation practice, the geological information of core fracture surface has not been fully collected and utilized. On the one hand, the engineering investigation drilling scene has the characteristics of strong mobility and complex field conditions, and generally lacks the conditions for long-term storage of cores for subsequent laboratory testing, resulting in the loss of a large amount of fracture surface information due to improper transportation and storage of cores after drilling; on the other hand, traditional core evaluation focuses on qualitative description of integrity (such as RQD value calculation), and the collection means for quantitative parameters such as dip angle and roughness of fracture surface are limited, which is difficult to meet the needs of high-precision geotechnological engineering evaluation.

[0003] Accurate judgment of rock mass integrity and extraction of special information such as dissolution fractures rely on fine classification and quantitative analysis of core fracture surface. For example, the irregular morphology and high roughness of dissolution fracture surface are important signs for identifying karst development area, and the dip angle distribution of joint surface directly affects the stability evaluation of rock mass.

[0004] Therefore, to realize efficient and high-precision collection of core fracture surface dip angle and surface characteristics on the drilling site is a key link to improve the quality of geotechnological engineering investigation and ensure engineering safety, and a non-contact and automated measuring technology that can adapt to field conditions is urgently needed to break through the limitations of traditional methods.

[0005] Although some three-dimensional scanning technologies (such as laser scanning and photogrammetry) have begun to be applied to the macroscopic morphology reconstruction of rock mass or core surface, these technologies often focus on large-scale three-dimensional modeling, and there are obvious deficiencies in the integrated and automated solution of synchronously acquiring the accurate inclination of the core fracture surface and the micro surface roughness at a close distance and high precision, and effectively fusing the two data to intelligently identify the fracture type. In particular, there is still a lack of mature equipment and methods on how to use macroscopic three-dimensional visual information to accurately guide micro contact measurement.

[0006] Therefore, it is of important engineering application value and technical development demand to develop an automatic device and method capable of quickly, accurately and objectively measuring the multi-dimensional parameters of the core fracture surface and assisting in judging the fracture properties. SUMMARY

[0007] The present application provides a core fracture surface close-range measurement device, which realizes the automatic and high-precision measurement of the inclination and roughness of the cylindrical core fracture surface by fusing line laser triangulation and high-precision line contact roughness measurement, and provides data support for distinguishing the fracture surface type, so as to solve the problems of strong subjectivity, low precision, low efficiency and difficulty in comprehensive analysis of the core fracture surface parameter measurement in the prior art.

[0008] According to one aspect of the present application, a core fracture surface close-range measurement device is provided, characterized in that it comprises a mounting seat and a frame body mounted on the mounting seat, a guide rail is arranged on the frame body, and a camera and a line laser projector are slidably mounted on the guide rail; a rotating table for carrying a core is arranged in the mounting seat, a gear-driven rack is arranged above the rotating table, the rack is symmetrically arranged on both sides of the core, and a line contact roughness measuring instrument is also mounted in the mounting seat.

[0009] Preferably, on the basis of the above-mentioned scheme, the rotating table comprises a motor-driven bevel gear and a bearing plate, the bottom of the bearing plate is provided with a helical tooth engaged with the bevel gear, and the bearing plate is mounted on the bottom of the mounting seat through a rotating shaft.

[0010] Preferably, on the basis of the above-mentioned scheme, the rack is symmetrically arranged on both sides of the core with the center line of the rotating shaft as the center, and a bevel gear corresponding to the rack is arranged on the side plate of the mounting seat.

[0011] The present application also provides a core fracture surface close-range measurement method, which is operated by using the above-mentioned core fracture surface close-range measurement device and comprises the following steps: Step 1: calibrate the internal and external parameters of the industrial camera and the line laser projector, adjust the pose of the line contact roughness measuring instrument and calibrate it, calibrate the position of the rotating table, and clamp the core; Step 2: Control and adjust the positions of the camera and line laser projector on the guide rail, and drive the rotary table in fixed angular increments. Step-by-step rotation to acquire current images and photographs of the core; Step 3: Move the control line contact roughness measuring instrument to the set position, so that the probe is at at least two different heights on the core fracture surface. The system continuously scans and records the changes in its three-dimensional coordinates to form a continuous spatial curve. Step 4: Correct the actual rotation angle of the rotary table according to the continuous space curve. From a theoretical perspective There is an error Joint registration and 3D model reconstruction based on geometric priors; Specifically, the process includes: first, based on the theoretical rotation angle and the rotation axis information obtained from calibration, performing an initial rigid body transformation on the local point clouds of each frame to obtain coarse registration results; then, using the continuous topography curve obtained by the probe as a geometric prior, constructing a cost function for the distance from the point cloud to the curve, and solving the correction transformation of each frame through iterative optimization to perform fine registration on the point clouds of each frame; finally, fusing the finely registered point clouds and using Poisson surface reconstruction to generate a three-dimensional digital model of the fracture surface. Step 5: Based on the 3D model and probe data, parameter calculations are performed to obtain the dip angle and roughness of the core sample. Specifically: RANSAC and PCA are used to extract the principal plane of the fracture from the 3D model and calculate its normal vector; the dip angle of the fracture surface is then obtained according to the formula given in the manual. Simultaneously, the roughness parameters such as Ra and Rq are calculated using the probe morphology curves obtained in Step 3. Based on the above scheme, in step 2, the positions of the camera and the line laser projector on the guide rail are controlled and adjusted, and the rotary table is driven in fixed angular increments. Step-by-step rotation to acquire current images and photographs of the core, specifically including: Control the rotary table in fixed angular increments Stepping rotation, at each angle Below, and A line laser projector projects a laser line onto the fracture surface of the rock core, while a camera simultaneously acquires images. For each pixel on the laser line in the image Based on the calibration parameters of the camera and the line laser, its three-dimensional coordinates in the world coordinate system are calculated using the principle of triangulation. All these points constitute the local point cloud Pi at that angle. Repeating this process yields a set of discrete point cloud sequences. .

[0012] Based on the above scheme, preferably, in step 3, the line contact roughness measuring instrument is moved to a set position so that the probe is at at least two different heights on the core fracture surface. The system continuously scans and records the changes in its three-dimensional coordinates to form a continuous spatial curve, specifically including: Control the line contact roughness measuring instrument so that its probe is at at least two different heights on the fracture surface of the core. The core is continuously scanned along its axial or circumferential direction. The probe records its three-dimensional coordinate changes in real time during its movement, forming a set of continuous spatial curves. These continuous spatial curves will serve as the "geometric prior" or "spatial reference" for subsequent point cloud stitching.

[0013] Based on the above scheme, step 4 specifically includes: Step 41, for each frame of local point cloud According to its theoretical rotation angle and the calibrated rotation axis information Construct an initial rigid body transformation matrix. Apply this initial transformation to the local point cloud Each point in The point cloud after coarse registration is obtained. ; Step 42, point cloud after coarse registration for each frame Find a tiny correction transformation To compensate for rotational errors ; Step 43, local point cloud for each frame The final, precise pose is determined by the final transformation matrix. The description describes how to apply the final transformation to all local point clouds and fuse them into a single, dense global point cloud. ; Step 44, process the global point cloud By applying the Poisson surface reconstruction algorithm, a watertight mesh model is generated using the normal vector information of the point cloud, which is the final three-dimensional digital model of the core fracture surface. .

[0014] A method for close-range measurement of core fracture surfaces as described in claim 7, characterized in that step 41 specifically includes: Let the unit direction vector of the rotary table axis in the world coordinate system be... ,in These are the components of the axis in the X, Y, and Z directions; Let be a 4x4 homogeneous transformation matrix, in the form of: ; in, The rotation matrix is ​​calculated using Rodriguez's rotation formula: , Here, I is a 3x3 identity matrix. It is a direction vector Antisymmetric matrix: .

[0015] Based on the above scheme, step 42 specifically includes: Step 421, construct a cost function Let represent the degree of mismatch between the point cloud and the topography curve after correction transformation. Find the value that minimizes this cost function. ; , in: It is a rough-matched accurate point cloud. One of the points, It is the 4x4 correction transformation matrix to be solved. Indicates the corrected point To the topography curve set The shortest distance, It is calculated as the minimum distance from that point to all points on all topographic curves: , in, It is a topographic curve The point on, It is a weighting function; Step 422: Solve iteratively using the Iterative Closest Point (ICP) algorithm. : .

[0016] Based on the above scheme, in step 5, the calculation of the dip angle value of the rock core includes the following details: Step 51, Model In the point cloud data, the Random Sample Consensus (RANSAC) algorithm is applied to identify and segment the point cloud subset that constitutes the principal plane of the fracture. ; Step 52, for the segmented planar point cloud subset The normal vector is accurately calculated using principal component analysis (PCA). ; , Wherein A, B, C respectively represent the normal vector in the world coordinate system X, Y, Z direction component, namely three coordinate axis direction direction cosine; Step 53, set the Z axis of the world coordinate system For the direction of gravity, the dip angle of the fracture surface Defined as the angle between the fracture surface and the horizontal plane, that is, the dip angle of the fracture surface Equivalent to the normal vector of the fracture surface And the vertical vector The angle between them The complementary angle of the angle: ; Dip angle : .

[0017] On the basis of the above scheme, preferably, in the step 5, the roughness calculation in detail includes: (1) calculate the center line of the profile: ; (2) profile arithmetic average deviation Indicates the arithmetic mean value of the absolute value of the profile deviation distance within the sampling length, the formula for calculating : ; Wherein, is the sampling length, is the number of sampling points, is the height value of the first Point, The average height of the profile within the sampling length; (3) profile root mean square deviation Indicates the square root of the arithmetic mean value of the square of the profile deviation distance within the sampling length, the formula for calculating : ; Wherein, is the sampling length, is the number of sampling points, is the height value of the first Point, The average height of the profile within the sampling length.

[0018] This invention discloses a near-range measurement device for core fracture surfaces. It uses a continuous morphology curve acquired by a high-precision contact probe as a spatial reference to perform joint registration and system extrinsic parameter self-calibration on multi-angle discrete point clouds obtained through line laser rotational scanning. This method, by introducing geometric prior constraints, fundamentally solves the problems of cumulative drift and splicing misalignment caused by mechanical errors in traditional rotational scanning. This device integrates line laser triangulation and contact contour measurement, achieving integrated, high-precision, synchronous measurement of the three-dimensional morphology, dip angle, and roughness of the core fracture surface, significantly improving the reconstruction accuracy of the fracture edge region and the accuracy of dip angle assessment. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the structure of the core fracture surface close-range measurement device of the present invention; Figure 2 This is a left-side view of the core fracture surface close-range measurement device of the present invention; Figure 3 For the present invention Figure 2 BB cross-sectional view; Figure 4 For the present invention Figure 2 AA section view; Figure 5 This is a flowchart of the method for close-range measurement of rock core fracture surfaces according to the present invention; Explanation of icon numbers: The components include: 1. Line laser projector; 2. Camera; 3. Core sample; 4. Line contact surface roughness measuring instrument; 5. Stepper motor; 6. Support frame; 7. Servo motor; 8. Ball screw; 9. Linear guide rail; 10. Slide; 11. Display touch screen; 12. Rotary table; 13. Rotary platform stepper motor; 14. Bevel gear; 15. Hydraulic telescopic device; 16. Rack; 17. Gear; 18. Embedded computing unit; 19. Motor control board; 20. Motor cable; 21. Camera cable. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] It should be understood that the term "include" as used in this specification and the following claims indicates the presence of the described features, integers, steps, operations, elements, and / or components but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] For the sake of simplicity, only the parts related to the present application are shown in the drawings, which do not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the components with the same structure or function is shown schematically, or only one of them is marked. In this document, "one" not only means "only one", but also means "more than one" situation.

[0023] It should be further understood that the term "and / or" used in the present application specification and the following claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0024] In addition, in the description of the present application, the terms "first", "second", etc. are only used for differentiation, and cannot be understood as indicating or implying relative importance.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor, and other embodiments can also be obtained.

[0026] Please refer to Figure 1 , and in combination with Figure 2 and Figure 3 , a core 3 fracture surface near distance measuring device of the present application is shown, which comprises a mounting seat and a frame body, the frame body is vertically erected on the mounting seat, and a linear guide rail 9 and a ball screw are arranged on the frame body for supporting and driving the lifting of the visual measurement module.

[0027] Among them, the linear guide rail 9 is slidably provided with a slide seat 10 for mounting a line laser projector 1 and a camera 2 for visual measurement collection, the camera 2 and the camera head are mounted on the slide seat 10 through a support frame 6, the slide seat 10 is provided with a rudder 7 for adjusting the angle between the support frame 6 and the slide seat 10, so as to adjust the pitch angle of the line laser projector 1 and the camera 2 to adapt to the observation of cores 3 of different sizes. Among them, the lifting of the slide seat 10 is realized by driving the ball screw 8 through the double-step motor 5 to realize the precise lifting of the visual platform.

[0028] The mounting seat is a working platform area, and the core to be measured 3 is centrally arranged; the line contact roughness measuring instrument 4 is arranged on one side of the mounting seat of the core 3 and used for contact measurement of the surface of the core 3.

[0029] The mounting seat is provided with a rotating table 12 for bearing the core 3, and a rack 16 driven by a gear 17 is arranged above the rotating table 12, the rack 16 is symmetrically arranged on the two sides of the core 3, and relative and opposite movements of the rack 16 are controlled, so that the core 3 can be clamped or released.

[0030] The rotating table 12 comprises a motor-driven bevel gear 14 and a bearing plate, the bottom of the bearing plate is provided with a bevel gear 14 engaged with the bevel gear 14, when the motor drives the bevel gear 14 to rotate, the rotating table 12 can be driven to rotate, so that the core 3 can rotate relative to the line contact roughness measuring instrument 4, and different angle measurements can be realized.

[0031] The bearing plate is arranged at the bottom of the mounting seat through a rotating shaft, the rack 16 is symmetrically arranged on the two sides of the core 3 with the center line of the rotating shaft as the center, and the mounting seat is provided with the gear 17 corresponding to the rack 16 on the side plate.

[0032] The application further provides a core fracture surface close-range measurement method, and the device is used for operation, and the method comprises the following steps. Step 1, the industrial camera 2 and the line laser projector 1 are calibrated by using internal parameters and external parameters, the pose of the line contact roughness measuring instrument 4 is adjusted and calibrated, the position of the rotating table 12 is calibrated, and the core 3 is clamped; the calibration parameters are stored and used as a basis for subsequent three-dimensional reconstruction and measurement.

[0033] Step 2, multi-angle discrete point cloud sequence acquisition. The core 3 to be measured is placed on the rotating table 12, the gear 17 and the rack 16 mechanism are automatically and stably clamped to the core 3 by driving the clamping motor through the display touch screen control system, the positions of the camera 2 and the line laser projector 1 on the guide rail are controlled and adjusted, the height of the Z axis of the vision platform and the pitch angle of the industrial camera 2 are adjusted, so that the line laser projector 1 and the industrial camera 2 can best cover the fracture area to be measured.

[0034] Synchronous scanning and data acquisition, the line laser projector 1 emits a linear laser to the surface of the core 3. The industrial camera 2 starts to shoot the image of the irradiated core 3. The rotating table 12 is controlled by the stepping motor 5 to rotate at a fixed angle increment Step-by-step rotation. At each angle , the line laser projector projects a laser line to the core fracture surface, and the camera synchronously collects images. For each pixel point in the image, the line laser projector projects a laser line to the core fracture surface, and the camera synchronously collects images. For each pixel point According to the calibration parameters of the camera and the line laser, the three-dimensional coordinates of the probe in the world coordinate system can be calculated by the principle of triangulation . All these points constitute a local point cloud at this angle . Repeat this process to obtain a sequence of discrete point clouds .

[0035] Step 3, multi-height continuous profile curve acquisition. Control the line contact roughness tester to make the probe continuously scan along the axial or circumferential direction of the core 3 at least two different heights of the core fracture surface. The probe records the change of its three-dimensional coordinates in real time during the movement, forming a set of (for example, two) continuous spatial curves (profile curves) with extremely high precision . These curves will serve as the "geometric prior" or "spatial reference" for subsequent point cloud stitching.

[0036] Step 4, correction of the actual rotation angle of the rotary table 12 of the rotary table and the theoretical angle . There is an error between the actual rotation angle of the rotary table and the theoretical angle. Joint registration and three-dimensional model reconstruction based on geometric prior. Specifically, it includes: first, according to the theoretical rotation angle and the rotation axis information obtained by calibration, an initial rigid body transformation is performed on each frame of local point cloud to obtain a coarse registration result; then, taking the continuous profile curve obtained by the probe as the geometric prior, a cost function of the distance between the point cloud and the curve is constructed, and the correction transformation of each frame is solved by iterative optimization, and the point clouds are accurately registered; finally, the point clouds after precise registration are fused, and a three-dimensional digital model of the core fracture surface is generated by Poisson reconstruction (see steps 41-44 for details); Step 5, after the three-dimensional model is reconstructed, the embedded computing unit 18 calculates the dip angle and roughness of the core 3; that is, based on the three-dimensional model and the probe data, the dip angle and roughness of the core are obtained by parameter calculation. Specifically: the RANSAC and PCA are used to extract the main plane of the fracture and calculate its normal vector from the three-dimensional model, and the dip angle of the fracture surface is obtained; at the same time, the probe profile curve obtained in step 3 is used to calculate the roughness parameters such as Ra and Rq (see steps 51-52 for details).

[0037] The specific technical solutions of the present application will be described in detail below, and step 4 specifically includes: Step 41, coarse registration. For each frame of local point cloud , first, according to its theoretical rotation angle and the rotation axis information calibrated, an initial rigid body transformation matrix is constructed. This transformation describes an ideal rotation process: Let the unit direction vector of the rotation table axis in the world coordinate system be where are the components of the axis in the X, Y, Z directions; is a 4x4 homogeneous transformation matrix of the form , where is the rotation matrix calculated from the Rodrigues' rotation formula: , Here, I is the 3x3 identity matrix, is the skew-symmetric matrix of the direction vector : , Apply this initial transformation to each point in the local point cloud to obtain the coarsely registered point cloud .

[0038] Step 42, fine registration. The goal of this step is to find a small correction transformation for each frame of the coarsely registered point cloud to compensate for the rotational error . This correction transformation is solved by aligning the point cloud with the high-precision topographic curves .

[0039] Construct a cost function that represents the degree of mismatch between the point cloud after the correction transformation and the topographic curves. The goal is to find the that minimizes this cost function.

[0040] , where: is a point in the coarsely registered point cloud , is the 4x4 correction transformation matrix to be solved, represents the shortest distance from the corrected point to the set of topographic curves . This distance can be calculated as the minimum value of the distance from the point to all points on all topographic curves: , where is a point on the topographic curve .

[0041] is a weight function, for example, a point cloud point closer to the distance profile curve can be given a higher weight to enhance the alignment effect.

[0042] To be solved is: , Since the correction amount is usually small, it can be parameterized as a small transformation containing 6 degrees of freedom (3 translations, 3 rotations), and solved iteratively using the Iterative Closest Point (ICP) algorithm, whose iteration process is as follows: (1) Find the corresponding points: for each point in the point cloud , find its nearest point in the profile curve set .

[0043] (2) Calculate the transformation: solve a rigid body transformation , so that the sum of the squared distances between all corresponding point pairs is minimized.

[0044] (3) Apply the transformation: update the point cloud .

[0045] (4) Repeat steps 1-3 until convergence. The final cumulative transformation is .

[0046] Step 43, global fusion and model generation. After fine calibration, the final and accurate pose of each local point cloud is described by the final transformation matrix . Apply the final transformation to all local point clouds to fuse them into a single, dense global point cloud : , Finally, apply the Poisson surface reconstruction algorithm to the global point cloud . This algorithm can generate a smooth, closed and well-topped mesh model using the normal vector information of the point cloud (which can be calculated in the point cloud preprocessing stage), i.e. the final three-dimensional digital model of the core fracture surface .

[0047] Wherein, step 5 specifically comprises: Step 51, fracture surface dip angle calculation, which is calculated according to the high-precision three-dimensional model generated in step 4.

[0048] 1. Plane segmentation, in the model ​​​​RANSAC algorithm is applied to identify and segment the point cloud subset that constitutes the main plane of the fracture . The RANSAC algorithm can stably handle non-planar regions and noise in the model.

[0049] 2. Normal vector calculation: for the segmented plane point cloud subset , its normal vector is accurately calculated by principal component analysis (PCA) . The specific steps are: (1) Calculate the centroid of the point set ; (2) Construct the covariance matrix of the point set ; (3) Perform eigenvalue decomposition on the covariance matrix . The eigenvector associated with the smallest eigenvalue is the best fitting normal vector of the plane .

[0050] 3. Inclination angle solution: set the Z-axis of the world coordinate system as the direction of gravity (vertical direction). The inclination angle of the fracture surface is usually defined as the angle between the fracture surface and the horizontal plane. This is equivalent to the complementary angle of the angle between the normal vector of the fracture surface and the vertical vector .

[0051] , Therefore, the inclination angle : .

[0052] Step 52, fracture surface roughness parameter calculation The roughness parameter is directly calculated from the probe topography curve collected in step 3 . Select a segment of one of the profile lines as the evaluation length . This segment of the profile is represented by a sequence of height values of N discrete points .

[0053] (1) Calculate the center line of the profile (average height): ; (2) The arithmetic mean deviation of the profile represents the arithmetic mean of the absolute values of the profile deviations within the sampling length, and the formula for calculating is:

[0054] where,​ is the sampling length, is the number of sampling points, is the height value of the first point, is the average height of the profile within the sampling length.

[0055] (3) Profile root mean square deviation represents the square root of the arithmetic mean of the square of the profile deviation distance within the sampling length, and is calculated by the formula:

[0056] wherein, is the sampling length, is the number of sampling points, is the height value of the first point, is the average height of the profile within the sampling length.

[0057] The core 3 fissure surface near distance measuring device of the application, by integrating the line laser triangulation system composed of a camera (2) and a line laser projector (1) and a line contact type roughness measuring instrument (4) in one, and combining the automatic clamping and rotating mechanism composed of a rotating table (12), a gear (17) and a rack (16), constructs an automatic multi-modal measurement system. Innovatively, the high-precision continuous topography curve obtained by the probe (4) is used as a spatial reference, and the multi-angle point cloud data obtained by rotating scanning is jointly registered and system calibrated, so that the cumulative drift introduced by mechanical error is fundamentally eliminated. The whole measurement and calculation process is automatically controlled by the embedded computing unit (18), deeply integrates macro three-dimensional topography and micro roughness representation, and finally realizes the integrated and high-precision measurement of the core 3 fissure surface inclination and roughness parameters, providing a reliable and fully digital solution for subsequent intelligent discrimination of fissure type and evaluation of rock mass stability.

[0058] Finally, the method of the present application is only a preferred embodiment, and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.​

Claims

1. A device for close-range measurement of rock core fracture surfaces, characterized in that, The device includes a mounting base and a frame mounted on the mounting base. The frame is equipped with a guide rail, on which a camera and a line laser projector are slidably mounted. The mounting base contains a rotating platform for carrying the rock core, and a gear-driven rack is mounted above the rotating platform. The rack is symmetrically arranged on both sides of the rock core. A line contact roughness measuring instrument is also installed in the mounting base.

2. The core fracture surface close-range measurement device as described in claim 1, characterized in that, The rotary table includes a motor-driven bevel gear and a support plate. The bottom of the support plate is provided with helical teeth that mesh with the bevel gear. The support plate is mounted on the bottom of the mounting base via a rotating shaft.

3. The core fracture surface close-range measurement device as described in claim 2, characterized in that, The rack consists of two racks symmetrically arranged on both sides of the rock core with the center line of the rotating shaft, and the side plate of the mounting base is provided with bevel gears corresponding to the racks.

4. A method for close-range measurement of core fracture surfaces, comprising using a close-range measurement device for core fracture surfaces as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Calibrate the internal and external parameters of the industrial camera and line laser projector, adjust and calibrate the position of the line contact roughness measuring instrument, calibrate the position of the rotary table, and clamp the core. Step 2: Control and adjust the positions of the camera and line laser projector on the guide rail, and drive the rotary table in fixed angular increments. Step-by-step rotation to acquire current images and photographs of the core; Step 3: Move the control line contact roughness measuring instrument to the set position, so that the probe is at at least two different heights on the core fracture surface. The system continuously scans and records the changes in its three-dimensional coordinates to form a continuous spatial curve. Step 4: Correct the actual rotation angle of the rotary table according to the continuous space curve. From a theoretical perspective There is an error Joint registration and 3D model reconstruction based on geometric priors; Step 5: Parameter calculation based on the 3D model and probe data, obtaining the dip angle and roughness of the core through the acquired data.

5. The method for close-range measurement of core fracture surfaces as described in claim 4, characterized in that, In step 2, the positions of the camera and line laser projector on the guide rail are controlled and adjusted, and the rotary table is driven in fixed angular increments. Step-by-step rotation to acquire current images and photographs of the core, specifically including: Control the rotary table in fixed angular increments Stepping rotation, at each angle Below, and A line laser projector projects a laser line onto the fracture surface of the rock core, while a camera simultaneously acquires images. For each pixel on the laser line in the image Based on the calibration parameters of the camera and the line laser, its three-dimensional coordinates in the world coordinate system are calculated using the principle of triangulation. All these points constitute the local point cloud Pi at that angle. Repeating this process yields a set of discrete point cloud sequences. .

6. The method for close-range measurement of core fracture surfaces as described in claim 5, characterized in that, In step 3, the control line contact roughness measuring instrument is moved to a set position, so that the probe is at at least two different heights on the core fracture surface. The system continuously scans and records the changes in its three-dimensional coordinates to form a continuous spatial curve, specifically including: Control the line contact roughness measuring instrument so that its probe is at at least two different heights on the fracture surface of the core. The core is continuously scanned along its axial or circumferential direction. The probe records its three-dimensional coordinate changes in real time during its movement, forming a set of continuous spatial curves. These continuous spatial curves serve as the "geometric prior" or "spatial reference" for subsequent point cloud stitching.

7. The method for close-range measurement of core fracture surfaces as described in claim 6, characterized in that, Step 4 specifically includes: Step 41, for each frame of local point cloud According to its theoretical rotation angle and the calibrated rotation axis information Construct an initial rigid body transformation matrix. Apply this initial transformation to the local point cloud Each point in The point cloud after coarse registration is obtained. ; Step 42, coarsely registered point cloud for each frame Find a correction transform To compensate for rotational errors ; Step 43, local point cloud for each frame The final, precise pose is determined by the final transformation matrix. The description describes how to apply the final transformation to all local point clouds and fuse them into a single, dense global point cloud. ; Step 44, process the global point cloud By applying the Poisson surface reconstruction algorithm, a watertight mesh model is generated using the normal vector information of the point cloud, which is the final three-dimensional digital model of the core fracture surface. .

8. The method for close-range measurement of core fracture surfaces as described in claim 7, characterized in that, Step 41 specifically includes: Let the unit direction vector of the rotary table axis in the world coordinate system be... ,in These are the components of the axis in the X, Y, and Z directions; Let be a 4x4 homogeneous transformation matrix, in the form of: ； in, The rotation matrix is ​​calculated using Rodriguez's rotation formula: ， Where I is a 3x3 identity matrix, It is a direction vector Antisymmetric matrix: 。 9. A method for close-range measurement of core fracture surfaces as described in claim 6, characterized in that, Step 42 specifically includes: Step 421, construct a cost function Let represent the degree of mismatch between the point cloud and the topography curve after correction transformation. Find the value that minimizes this cost function. ; ， in: It is a rough-matched accurate point cloud. One of the points, It is the 4x4 correction transformation matrix to be solved. Indicates the corrected point To the topography curve set The shortest distance, It is calculated as the minimum distance from that point to all points on all topographic curves: ， in, It is a topographic curve The point on, It is a weighting function; Step 422: Solve iteratively using the Iterative Closest Point (ICP) algorithm. : 。 10. A method for close-range measurement of core fracture surfaces as described in claim 6, characterized in that, In step 5, the calculation of the dip angle value of the core sample includes the following details: Step 51, in the model In the point cloud data, the Random Sample Consensus (RANSAC) algorithm is applied to identify and segment the point cloud subset that constitutes the principal plane of the fracture. ; Step 52, for the segmented planar point cloud subset The normal vector is accurately calculated using principal component analysis (PCA). : ， Where A, B, and C represent the components of the normal vector in the X, Y, and Z directions of the world coordinate system, respectively, that is, the direction cosines in the three coordinate axes. Step 53, Set the Z-axis of the world coordinate system The dip angle of the fracture surface is in the direction of gravity. Defined as the angle between the fracture surface and the horizontal plane, i.e., the dip angle of the fracture surface. Equivalent to the normal vector of the fracture surface with the vertical vector Angle between complementary angle: ; inclination : ; Step 5, the roughness calculation includes the following details: (1) Calculate the centerline of the profile: ； (2) Profile arithmetic mean deviation This represents the arithmetic mean of the absolute values ​​of the profile offsets within the sampling length. The formula: ； in, It is the sampling length. It is the number of sampling points. It is the first The height value of each point. It is the average height of the contour within the sampling length; (3) Root mean square deviation of profile This represents the square root of the arithmetic mean of the squared profile offsets within the sampling length. The formula: ; in, It is the sampling length. It is the number of sampling points. It is the first The height value of each point. It is the average height of the inner contour within the sampling length.

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