A positioning device and method for evaluating rock joint roughness

Abstract

The application discloses a positioning device and implementation method for evaluating rock joint roughness, and belongs to the technical field of rock mechanics. The positioning device comprises a rock positioning plate, wherein the rock positioning plate is provided in a mouth shape, four end points on the surface of the rock positioning plate are respectively provided with positioning points, and three check points are provided side by side on each side of the rock positioning plate, and the three check points on the same side are located between the adjacent two positioning points. The implementation method comprises the following steps: setting convergence method shooting parameters, photographing the rock positioning plate fixed on the rock structure surface to be measured through a camera; establishing a three-dimensional point cloud model of the rock structure surface through a video obtained by shooting around the rock structure surface to be measured, and calculating a two-dimensional precision evaluation index and a three-dimensional precision evaluation index according to the established three-dimensional point cloud model. The application can help to quickly position and zoom the scene, so that the traditional positioning needs to be assisted by a total station, and time and manpower are saved.

Description

Technical Field

[0001] This invention belongs to the field of rock mechanics technology, specifically relating to a positioning device and implementation method for evaluating the roughness of rock joints. Background Technology

[0002] Rock joint roughness has a significant impact on the shear strength, deformation, and permeability of rock discontinuities. Accurately describing rock joint roughness is crucial for stability analysis in rock engineering design. A key parameter representing the surface undulations and roughness of rock is the joint roughness coefficient (JRC). Therefore, measuring and evaluating JRC values ​​is essential for the construction and disaster prevention of rock engineering projects.

[0003] In recent years, photogrammetry has often been used as an alternative method for acquiring three-dimensional models of target rock masses when dealing with engineering problems. It offers advantages such as low cost, portability, ease of use, and the ability to capture millimeter-level high-precision point clouds. Therefore, this method has been widely applied in rock engineering practice. However, in field photogrammetry applications, limitations imposed by terrain or image acquisition settings often prevent the use of recommended optimal shooting parameter combinations, leading to a certain degree of measurement error. Currently, photogrammetry technology is maturely applied in fields such as earth science and computer science, but its application in rock mechanics is relatively limited, and mostly confined to indoor measurements, making it unsuitable for measuring the surface roughness of rock structures in field environments. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a positioning device and implementation method for evaluating the roughness of rock joints, which is applicable not only to indoor measurements but also to the measurement of the roughness of rock structural surfaces in field environments.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a positioning device for evaluating the roughness of rock joints, comprising: a rock positioning plate, the rock positioning plate being orifice-shaped, the four endpoints of the surface of the rock positioning plate being respectively provided with positioning points, and three inspection points being arranged side by side on each side of the rock positioning plate, the three inspection points on the same side being located between two adjacent positioning points.

[0007] Furthermore, the positioning device also includes an elliptical camera positioning ring, the minor diameter of which is greater than the length of the edge of the rock positioning plate. The axis of the rock positioning plate and the axis of the camera positioning ring are on the same straight line. The camera positioning ring is provided with a slide rail, and a slider is slidably mounted on the slide rail. A mounting bracket for mounting the camera is rotatably mounted on the slider. Four first telescopic rods located at the ends of the rock positioning plate are rotatably connected between the rock positioning plate and the camera positioning ring. Each first telescopic rod contains a first spring. A second telescopic rod is fixedly mounted on the camera positioning ring. The axis of the second telescopic rod is parallel to the axis of the camera positioning ring. The end of the second telescopic rod away from the camera positioning ring is used to fix it to the surface of the structure to be measured by bolts.

[0008] Furthermore, the camera positioning ring includes a first positioning ring and a second positioning ring that is slidably mounted on the first positioning ring. The first and second positioning rings can be fixedly connected by a snap-fit. The connection between the first and second positioning rings forms a T-shaped groove for limiting the sliding of the slider. The second telescopic rod includes a second sliding rod fixedly mounted on the first positioning ring and a second sleeve slidably connected to the second sliding rod. The second sliding rod is slidably mounted inside the second sleeve. The second sleeve is used to fix to the surface of the structure to be measured by bolts. The second sliding rod has a cavity that penetrates the first positioning ring. Two symmetrically arranged telescopic rods are provided in the cavity. A positioning rod slides radially along the cavity. The second sliding rod has a through hole that radially penetrates the cavity. The positioning rod has an insert rod that can be moved out of the through hole. A second spring connects the two positioning rods. Multiple positioning grooves that can cooperate with the insert rods are arranged side by side along the axial direction inside the second sleeve. The two positioning rods are moved away from each other so that the insert rod can be moved out of the through hole and inserted into the positioning groove. A connecting rod is provided on the second positioning ring and slidably installed in the cavity. The end of the connecting rod away from the second positioning ring has a tapered part. The end of the positioning rod near the first positioning ring has an inclined part that cooperates with the tapered part. The sliding connecting rod can squeeze the inclined part to make the two positioning rods move away from each other.

[0009] A method for implementing a positioning device for evaluating the roughness of rock joints includes the following steps:

[0010] S1: Set the convergence method shooting parameters. Take pictures of the rock positioning plate fixed on the rock structure surface to be measured with a camera. The shooting range covers the entire rock positioning plate. The shooting parameters include: the initial position of the camera, the shooting distance Z of the camera, the focal length f of the camera, the shooting angle α, the rotation step β, and the shooting angle boundary γ.

[0011] S2: A three-dimensional point cloud model of the rock structure surface is established by taking a video of the rock structure surface under test. When taking the video, the focal length f of the camera satisfies 18mm≤f≤85mm, the shooting angle α=30°, the rotation step β=30°, and the shooting angle boundary γ=30°.

[0012] S3: By perpendicularly intersecting any plane A with the reconstructed 3D point cloud structure model, extract the point cloud coordinates within a preset distance range from the plane. Project the extracted point cloud coordinates perpendicularly onto plane A along the normal direction of plane A to obtain the two-dimensional coordinates of the projection points. Optimize the obtained projection points using linear interpolation. Connect the optimized projection points to obtain the surface roughness profile curve in that direction, and calculate the root mean square and the surface roughness coefficient of the rock structure.

[0013] The formula for calculating the root mean square Z² is:

[0014]

[0015] Where L represents the profile length; N represents the number of midpoints on the rock discontinuity surface; z i x i Let x and z be the x and z coordinates of the i-th point, respectively.

[0016] The formula for calculating the surface roughness coefficient of rock is:

[0017] JRC = 32.2 + 32.47log10Z2.

[0018] S4: Calculate the two-dimensional accuracy evaluation index Error based on the established three-dimensional point cloud model. Reprojection And three-dimensional accuracy evaluation indicators.

[0019] Furthermore, in step S1, the shooting distance Z satisfies:

[0020]

[0021] In the formula, f min The minimum focal length of the camera is m. max For maximum magnification, m min S is the minimum magnification. LOSR This refers to spatial resolution.

[0022] Furthermore, in step S2, the steps for establishing the 3D point cloud model include:

[0023] A1: Input parameters: Input the convergence method shooting parameters and the rock height H into the convergence parameter automatic selection algorithm. The convergence parameter automatic selection algorithm locates and calibrates the image based on the rock positioning plate to obtain the coordinates of the image matching point;

[0024] A2: Generate a 3D point cloud and draw a simplified 3D rock size model: First, based on the coordinates of the matching points in the image, the camera motion is analyzed by the simultaneous localization and mapping (SLAM) algorithm to find the 3D point cloud structure; then, multi-view stereo vision with clustering is used to cluster the 3D point cloud structure and generate a 3D point cloud; finally, based on the 3D point cloud, a simplified 3D rock size model is drawn in MATLAB, while generating target spatial accuracy at different shooting distances from the same shooting angle to help select a suitable shooting distance, and finally drawing a simplified 3D rock size model.

[0025] Furthermore, in step S2, the two-dimensional accuracy evaluation index Error Reprojection Calculated using the following formula:

[0026]

[0027] In the formula, (x' i y' i (x) represents the coordinates on the two-dimensional plane after reprojection transformation. i y i ) represents the coordinates on the two-dimensional plane obtained from actual measurement.

[0028] Furthermore, in step S4, the calculation of the three-dimensional accuracy evaluation index includes:

[0029] B1: Extract the 3D coordinates of 12 checkpoints from the real-scale point cloud.

[0030] B2: Calculate the root mean square error (RMSE) between the coordinates of each checkpoint and the corresponding true 3D coordinates using the following formula.

[0031]

[0032]

[0033]

[0034]

[0035] In the formula, x i(estimation) y i(estimation) z i(estimation) x represents the measured three-dimensional coordinates of a point in the point cloud; i(standard) y i(standard) z i(standard) The values ​​are the actual 3D coordinates. RMSE values ​​within [0,1] are considered high precision, while those within [1,3] are considered low precision. If the calculated RMSE does not meet the low precision requirement, the result is considered unqualified and the image needs to be retaken.

[0036] The beneficial effects of this invention are as follows:

[0037] 1) It can help to quickly locate and zoom the scene, thereby avoiding the need for a total station in traditional positioning, saving time and manpower; 2) The device of this invention plays a guiding role in convergent photography, and the position distribution of 4 positioning points and 12 check points can assist in the shooting of rock surface; 3) This invention can evaluate the accuracy of rock roughness in two dimensions and three dimensions based on the average reprojection error and average root mean square error of the check points, respectively.

[0038] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0039] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0040] Figure 1 This is a schematic diagram of the rock positioning plate structure according to an embodiment of the present invention;

[0041] Figure 2 This is a flowchart illustrating the implementation method of an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the shooting point in an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram showing the connection between the rock positioning plate and the camera positioning ring in an embodiment of the present invention;

[0044] Figure 5 This is a side view of the connection between the rock positioning plate and the camera positioning ring according to an embodiment of the present invention;

[0045] Figure 6 This is a schematic diagram of the second telescopic rod structure according to an embodiment of the present invention;

[0046] Figure 7 This is a side sectional view of the first and second positioning rings in an embodiment of the present invention when they are closed and disengaged.

[0047] The following are the markings in the attached diagram: Rock positioning plate 1, positioning point 2, inspection point 3, camera positioning ring 4, slide rail 401, slider 402, mounting bracket 403, first positioning ring 404, second positioning ring 405, T-slot 406, first telescopic rod 5, first sliding rod 501, first sleeve 502, first spring 503, second telescopic rod 6, second sliding rod 601, second sleeve 602, fixing plate 603, cavity 604, positioning rod 605, insertion rod 606, second spring 607, positioning groove 608, connecting rod 609, tapered part 610, inclined part 611. Detailed Implementation

[0048] Example 1, as Figures 1-3 As shown, the present invention provides a positioning device for evaluating the roughness of rock joints, comprising: a rock positioning plate 1, the rock positioning plate 1 being orifice-shaped, the four endpoints of the surface of the rock positioning plate 1 being respectively provided with positioning points 2, and three inspection points 3 arranged side by side on each side of the rock positioning plate 1, the three inspection points 3 on the same side being located between two adjacent positioning points 2.

[0049] A method for implementing a positioning device for evaluating rock joint roughness includes:

[0050] S1: Determine the convergence method imaging parameters, and take pictures of the rock positioning plate 1 fixed on the surface of the rock structure to be measured using a camera. The imaging range should cover the entire rock positioning plate 1.

[0051] The shooting parameters include: camera shooting distance Z, camera focal length f, shooting angle α, rotation step β, and shooting angle boundary γ;

[0052] The initial camera position is a point directly above the center of the rock structure surface. The camera's shooting distance Z is the distance from the initial camera position to the center of the rock structure surface. The focal length f should satisfy f min =18mm and f max =85mm, the shooting angle α is the angle between the line connecting the initial camera position to the center point of the rock structure surface and the line connecting the center point of the rock structure surface to the camera shooting position, the rotation step β is the angle of the camera rotating around the rock for each shot, and the shooting angle boundary γ is the angle between the camera shooting position and the plane where the rock is located, where α = 30°, β = 30°, and γ = 30°.

[0053] The shooting distance Z satisfies:

[0054]

[0055] In the formula, f min The minimum focal length of the camera is m. max For maximum magnification, m min S is the minimum magnification. LOSRThis refers to spatial resolution.

[0056] The algorithm described above improves the accuracy and convenience of selecting shooting parameters in shooting scenarios with different rock sizes; it also solves the problem of simultaneously selecting focal length and shooting distance, making the selection of focal length and shooting distance more diverse and scientific.

[0057] The determination of magnification and shooting distance: Magnification (m) is defined as the ratio of the camera image sensor size (p×q, length×width) to the field of view (FOV) size (E×F, length×width). It can also be calculated at specific distances and focal lengths, as follows:

[0058]

[0059] In both calculation methods, the obtained magnification values ​​are approximately equal (note that sensor manufacturing errors may cause slight differences). When capturing images of different rock targets, the field of view (FOV) needs to cover the entire rock. However, rock dimensions exhibit irregularities, resulting in the following scenarios: Scenario 1, the rock is very flat, and the length determines the FOV; Scenario 2, the rock is very narrow, and the width determines the FOV. Therefore, in both cases, the maximum magnification m is determined by identifying the minimum field of view and subsequently calculating the focal length. max To achieve the minimum field of view (it is worth noting that due to shooting errors, the minimum FOV of the focal length needs to be a certain range larger than the size of the rocks in the photo; here the algorithm sets this range to 50 mm for both length and width), this is beneficial for calculating the minimum shooting distance when using the minimum focal length.

[0060] When extracting JRC data, the spatial resolution S of the confined object must be manually established based on the ground sampling distance. LOSR This indicates the precision of the discernible rock; the denser the point cloud, the higher the precision. Minimum magnification m min It can be calculated using the following formula

[0061]

[0062] According to optical theory, when considering practical applications, the entire field of view needs to be taken into account, through S LOSR Dividing by three allows for leeway in determining the positional uncertainty within the field of view, enabling the determination of the maximum shooting distance based on the minimum magnification and the maximum focal length.

[0063] When determining the shooting distance range, it is difficult to obtain quantitative values ​​in on-site surveys because the calculated values ​​are not integers. Therefore, the shooting distance range is optimized to be multiples of 50 mm. In summary, the shooting distance and focal length values ​​are sampled at intervals of 20 mm and 1 mm respectively within their respective ranges, and the corresponding camera position points will be automatically obtained according to the algorithm.

[0064] S2: A 3D point cloud model of the rock structure surface is established using video footage captured around the surface to be measured. During filming, the camera's focal length f satisfies 18mm ≤ f ≤ 85mm, the shooting angle α = 30°, the rotation step β = 30°, and the shooting angle boundary γ = 30°. Figure 3 The images were taken around the rock structure to be measured, along the following points: X1 - shooting point 1 (shooting point directly behind the structure), X2 - shooting point 2 (shooting point directly in front of the structure), X3 - shooting point 3 (shooting point directly to the left of the structure), X4 - shooting point 4 (shooting point directly to the right of the structure), X5 - shooting point 5 (shooting point 45° to the left rear of the structure), X6 - shooting point 6 (shooting point 45° to the right front of the structure), X7 - shooting point 7 (shooting point 45° to the left front of the structure), and X8 - shooting point 8 (shooting point 45° to the right rear of the structure).

[0065] The steps for creating a 3D point cloud model include:

[0066] Input parameters: Input the convergence method shooting parameters and the rock height H into the convergence parameter automatic selection algorithm. The convergence parameter automatic selection algorithm locates and calibrates the image based on the rock positioning plate 1 to obtain the coordinates of the image matching point;

[0067] To generate a 3D point cloud and draw a simplified 3D rock dimension model: First, based on the coordinates of matching points in the image, the Simultaneous Localization and Mapping (SLAM) algorithm analyzes camera motion to find the 3D point cloud structure. Then, multi-view stereo vision (MVS) clustering is used to cluster the 3D point cloud structure and generate a 3D point cloud. Finally, based on the 3D point cloud, a simplified 3D rock dimension model is drawn in MATLAB, simultaneously generating target spatial accuracy at different shooting distances from the same shooting angle to help select a suitable shooting distance.

[0068] S3: By perpendicularly intersecting any plane A with the reconstructed 3D point cloud structure model, extract the point cloud coordinates within a preset distance range from the plane. Project the extracted point cloud coordinates perpendicularly onto plane A along the normal direction of plane A to obtain the two-dimensional coordinates of the projection points. Optimize the obtained projection points using linear interpolation. Connect the optimized projection points to obtain the surface roughness profile curve in that direction, and calculate the root mean square and the surface roughness coefficient of the rock structure.

[0069] The formula for calculating the root mean square Z² is:

[0070]

[0071] Where L represents the profile length; N represents the number of midpoints on the rock discontinuity surface; z i x iLet x and z be the x and z coordinates of the i-th point, respectively.

[0072] The formula for calculating the surface roughness coefficient of rock is:

[0073] JRC = 32.2 + 32.47log10Z2.

[0074] S4: Calculate the two-dimensional accuracy evaluation index Error based on the established three-dimensional point cloud model. Reprojection and three-dimensional accuracy evaluation indicators,

[0075] Among them, the two-dimensional accuracy evaluation index Error Reprojection Calculated using the following formula:

[0076]

[0077] In the formula, (x' i y' i (x) represents the coordinates on the two-dimensional plane after reprojection transformation. i y i () represents the coordinates on the two-dimensional plane obtained from actual measurement;

[0078] The calculation of three-dimensional accuracy evaluation indicators includes the following steps:

[0079] The 3D coordinates of 12 checkpoints in the real-scale point cloud were extracted, and the root mean square error (RMSE) between the coordinates of each checkpoint and its corresponding real 3D coordinates was calculated using the following formula.

[0080]

[0081]

[0082]

[0083]

[0084] In the formula, x i(estimation) y i(estimation) z i(estimation) x represents the measured three-dimensional coordinates of a point in the point cloud; i(standard) y i(standard) z i(standard) The values ​​are the actual 3D coordinates. RMSE values ​​within [0,1] are considered high precision, while those within [1,3] are considered low precision. If the calculated RMSE does not meet the low precision requirement, the result is considered unqualified and the image needs to be retaken.

[0085] Example 2, as Figures 4-7As shown, the present invention provides a positioning device for evaluating the roughness of rock joints, comprising: a rock positioning plate 1 and an elliptical camera positioning ring 4. The axis of the rock positioning plate 1 and the axis of the camera positioning ring 4 are on the same straight line. The rock positioning plate 1 is shaped like an opening. Positioning points 2 are respectively provided at the four endpoints of the surface of the rock positioning plate 1. Three inspection points 3 are arranged side by side on each side of the rock positioning plate 1. The three inspection points 3 on the same side are located between two adjacent positioning points 2. A slide rail 401 is provided on the camera positioning ring 4. A slider 402 is slidably mounted on the slide rail 401. A mounting bracket 403 for mounting a camera is rotatably mounted on the slider 402. A first extension is rotatably connected between the rock positioning plate 1 and the elliptical camera positioning ring 4. The first telescopic rod 5 includes a first sliding rod 501 rotatably connected to the rock positioning plate 1 and a first sleeve 502 rotatably connected to the camera positioning ring 4. The first sliding rod 501 is slidably connected within the first sleeve 502. A first spring 503 is connected between the first sliding rod 501 and the inner wall of the first sleeve 502. The four first telescopic rods 5 are respectively rotatably installed at the four ends of the rock positioning plate 1. The rock positioning plate 1 is square. The minor diameter of the camera positioning ring 4 is greater than the length of the side of the rock positioning plate 1. A second telescopic rod 6 is fixedly installed on the camera positioning ring 4. The axis of the second telescopic rod 6 is parallel to the axis of the camera positioning ring 4. The end of the second telescopic rod 6 away from the camera positioning ring 4 is used to fix it to the surface of the structure to be measured by bolts.

[0086] In this scheme, when fixing the positioning device on the rock structure surface to be measured, firstly, the rock positioning plate 1 is placed on the rock structure surface to be measured. Then, after fixing the second telescopic rod 6 on the structure surface to be measured, the distance between the camera positioning ring 4 and the rock positioning plate 1 is adjusted so that the camera's shooting distance Z meets the preset conditions. Then, the range of the second telescopic rod 6 is locked to fix the position of the camera positioning ring 4. At this time, the first spring 503 is in a compressed state. Under the action of the first spring 503, the rock positioning plate 1 is pressed tightly against the rock structure surface to be measured. When taking pictures, the shooting angle α of the camera is adjusted to α = 30°, and the slider 402 is slid along the slide rail 401 to make the camera surround the rock to take pictures. The rotation step β of each shooting position is 30°.

[0087] This solution, through the design of the above structure, ensures that when the camera is shooting around the rock, the height of the rock positioning plate 1 remains constant whether it is placed on a horizontal or inclined rock structure surface. It also facilitates the movement of the camera to the shooting point, reducing the positional error of the camera during manual shooting. By setting the first spring 503, the rock positioning plate 1 can be tightly attached to the rock structure surface, avoiding damage to the rock positioning plate 1 during fixing when it is directly fixed to the rock structure surface. Furthermore, by setting the first telescopic rod 5 and the second telescopic rod 6, it is convenient to adjust the distance between the camera positioning ring 4 and the rock positioning plate 1, that is, to adjust the shooting distance Z of the camera to meet the preset conditions.

[0088] Furthermore, the camera positioning ring 4 includes a first positioning ring 404 and a second positioning ring 405 that is slidably mounted on the first positioning ring 404. The first positioning ring 404 and the second positioning ring 405 can be fixedly connected by a snap-fit. The first positioning ring 404 and the second positioning ring 405 are connected to form a T-shaped groove 406. The T-shaped groove 406 is a slide rail 401 that cooperates with the slider 402. The second telescopic rod 6 includes a second sliding rod 601 fixedly mounted on the first positioning ring 404 and a second sleeve 602 slidably connected to the second sliding rod 601. The second sliding rod 601 is slidably mounted inside the second sleeve 601. The end of the second sleeve 602 away from the first positioning ring 404 is provided with a fixing plate 603. The fixing plate 603 is provided with a through hole for the bolt to pass through. The second sliding rod 601 is provided with a cavity 603 that penetrates the first positioning ring 404. The cavity 604 is symmetrical. Two positioning rods 605 are provided, which can slide radially along the cavity 604. The second sliding rod 601 has a through hole 605 that radially penetrates the cavity 604. The positioning rod 605 has an insertion rod 606 that can be moved out of the through hole 605. A second spring 607 is connected between the two positioning rods 605. Multiple positioning grooves 608 that can cooperate with the insertion rods 606 are arranged side by side along the axial direction inside the second sleeve 602. The two positioning rods 605 are moved away from each other so that the insertion rods 606 can be moved out of the through hole 605 and inserted into the positioning grooves 608. The second positioning ring 405 has a connecting rod 609 that is slidably installed in the cavity 604. The end of the connecting rod 609 away from the second positioning ring 405 has a tapered part 610. The end of the positioning rod 605 near the first positioning ring 404 has an inclined part 611 that cooperates with the tapered part 610. The sliding connecting rod 609 can squeeze the inclined part 611 to make the two positioning rods 605 move away from each other.

[0089] In this scheme, when fixing the second telescopic rod 6, the second sleeve 602 is slid to make the fixing plate 603 on each second sleeve 602 contact the rock structure surface to be measured. The second sleeve 602 is fixed by bolts passing through the through holes in the fixing plate 603 and connecting it to the rock structure surface. Before installing the slider 402, the first positioning ring 404 and the second positioning ring 405 are in a far-away state. At this time, the slider 402 and the camera are not installed on the camera positioning ring 4, so as to facilitate adjusting the distance between the first positioning ring 404 and the second positioning ring 405. The slider 402 with the camera installed is then placed... Within the T-groove 406, the second positioning ring 405 moves towards the first positioning ring 404 so that the T-groove 406 engages with the slider 402, thereby limiting the slider 402. Simultaneously, the connecting rod 609 moves along the cavity 604 and the tapered portion 610 presses against the inclined portion 611, causing the two positioning rods 605 to move away from each other. This drives the insertion rod 606 to move out along the corresponding through hole 605 into the positioning groove 608, thereby locking the second telescopic rod 6. Then, the first positioning ring 404 and the second positioning ring 405 are fixed by a snap-fit ​​connection to ensure the stability of the entire structure.

[0090] Through the design of the above structure, this solution can lock or unlock multiple second telescopic rods 6 simultaneously by sliding the second positioning ring 405 when the extension lengths of the second telescopic rods 6 are inconsistent on the inclined rock surface to be tested. It can also limit or release the slider 402, which facilitates the adjustment of the height of the camera positioning ring 4 and saves manpower.

[0091] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A positioning device for evaluating the roughness of rock joints, comprising: A rock positioning plate, characterized in that: the rock positioning plate is shaped like an opening, and positioning points are respectively provided at the four ends of the surface of the rock positioning plate; three inspection points are arranged side by side on each side of the rock positioning plate, and the three inspection points on the same side are located between two adjacent positioning points; the positioning device further includes an elliptical camera positioning ring, the minor diameter of the camera positioning ring being greater than the length of the side of the rock positioning plate; the axis of the rock positioning plate and the axis of the camera positioning ring are on the same straight line; a slide rail is provided on the camera positioning ring, a slider is slidably mounted on the slide rail, and a mounting bracket for mounting a camera is rotatably mounted on the slider; four first telescopic rods are rotatably connected between the rock positioning plate and the camera positioning ring, each located at one end of the rock positioning plate; a first telescopic rod is provided inside the first telescopic rod; a second telescopic rod is fixedly mounted on the camera positioning ring, the axis of the second telescopic rod being parallel to the axis of the camera positioning ring; the end of the second telescopic rod away from the camera positioning ring is used to fix it to the surface of the structure to be measured by bolts; the camera positioning ring includes a first positioning ring and a second positioning ring that is slidably mounted on the first positioning ring; the first positioning ring... The first positioning ring and the second positioning ring can be fixed by a snap-fit ​​connection. The connection between the first positioning ring and the second positioning ring forms a T-shaped groove for limiting the sliding of the slider. The second telescopic rod includes a second sliding rod fixedly installed on the first positioning ring and a second sleeve slidably connected to the second sliding rod. The second sliding rod is slidably installed in the second sleeve. The second sleeve is used to fix to the surface of the structure to be measured by bolts. The second sliding rod has a cavity that penetrates the first positioning ring. Two positioning rods that can slide radially along the cavity are symmetrically arranged in the cavity. The second sliding rod has a through hole that penetrates the cavity radially. The positioning rod has an insertion rod that can be moved out of the through hole. A second spring is connected between the two positioning rods. The second sleeve has multiple positioning grooves arranged side by side along the axial direction that can cooperate with the insertion rod. The two positioning rods are moved away from each other so that the insertion rod can be moved out of the through hole and inserted into the positioning groove. The second positioning ring has a connecting rod that is slidably installed in the cavity. The end of the connecting rod away from the second positioning ring has a tapered part. The end of the positioning rod near the first positioning ring has an inclined part that cooperates with the tapered part. The sliding connecting rod can squeeze the inclined part to make the two positioning rods move away from each other.

2. The method for implementing the positioning device for evaluating rock joint roughness according to claim 1, characterized in that, Includes the following steps: S1: Set the convergence method shooting parameters. Take pictures of the rock positioning plate fixed on the surface of the rock structure to be measured using a camera. The shooting range covers the entire rock positioning plate. The shooting parameters include: the initial position of the camera and the shooting distance of the camera. Z Camera focal length f Shooting angle Rotation step size Shooting angle boundaries ; S2: A 3D point cloud model of the rock structure surface is constructed using videos captured around the surface to be measured. The camera's focal length during filming is specified. f Meets 18 mm f 85 mm Shooting angle =30°, rotation step size =30°, shooting angle boundary =30°; S3: By perpendicularly intersecting any plane A with the reconstructed 3D point cloud structure model, extract the point cloud coordinates within a preset distance range from the plane. Project the extracted point cloud coordinates perpendicularly onto plane A along the normal direction of plane A to obtain the two-dimensional coordinates of the projection points. Optimize the obtained projection points using linear interpolation. Connect the optimized projection points to obtain the surface roughness profile curve in that direction, and calculate the root mean square and the surface roughness coefficient of the rock structure. Calculate the root mean square The formula is: in Indicates the length of the outline; Indicates the number of midpoints on a rock discontinuity surface; , Represented as the first Pointed Coordinates and coordinate; The formula for calculating the surface roughness coefficient of rock is: JRC=32.2+32.47log10 ; S4: Calculate the two-dimensional accuracy evaluation index based on the established three-dimensional point cloud model. And three-dimensional accuracy evaluation indicators.

3. The method for implementing the positioning device for evaluating rock joint roughness according to claim 2, characterized in that, In step S1, the shooting distance satisfy: In the formula, This is the camera's minimum focal length. At maximum magnification, Minimum magnification This refers to spatial resolution.

4. The method for implementing the positioning device for evaluating rock joint roughness according to claim 3, characterized in that, Step S2, the steps for establishing the 3D point cloud model include: A1: Input parameters: Input the convergence method shooting parameters and the rock height H into the convergence parameter automatic selection algorithm. The convergence parameter automatic selection algorithm locates and calibrates the image based on the rock positioning plate to obtain the coordinates of the image matching point; A2: Generate a 3D point cloud and draw a simplified 3D rock size model: First, based on the coordinates of the matching points in the image, the camera motion is analyzed by the simultaneous localization and mapping (SLAM) algorithm to find the 3D point cloud structure; then, multi-view stereo vision with clustering is used to cluster the 3D point cloud structure and generate a 3D point cloud; finally, based on the 3D point cloud, a simplified 3D rock size model is drawn in MATLAB, while generating target spatial accuracy at different shooting distances from the same shooting angle to help select a suitable shooting distance, and finally drawing a simplified 3D rock size model.

5. The method for implementing the positioning device for evaluating rock joint roughness according to claim 4, characterized in that, In step S2, the two-dimensional accuracy evaluation index Calculated using the following formula: In the formula, The coordinates are on the two-dimensional plane after reprojection transformation. These are the coordinates on the two-dimensional plane obtained from actual measurements.

6. The method for implementing the positioning device for evaluating rock joint roughness according to claim 5, characterized in that, In step S4, the calculation of the three-dimensional accuracy evaluation index includes: B1: Extract the 3D coordinates of 12 checkpoints from the real-scale point cloud. B2: Calculate the root mean square error between the coordinates of each checkpoint and the corresponding true three-dimensional coordinates using the following formula. , In the formula, 、 、 The measured three-dimensional coordinates of a point in the point cloud; 、 、 These are the actual three-dimensional coordinate values, where, High accuracy is achieved within the range [0,1], and low accuracy is achieved within the range [1,3]. If the calculated... If the accuracy requirement is not met, the image is considered unqualified and needs to be reshot.

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