Method for three-dimensional reconstruction and compliance evaluation of open pit based on CAD design drawing

Abstract

This invention discloses a method for 3D reconstruction and compliance assessment of open-pit mines based on CAD design drawings, belonging to the field of open-pit mine image processing technology. It is used for 3D reconstruction and compliance assessment of open-pit mines, including data preprocessing based on CAD design drawings, including map sheet division and data registration; constructing a primitive recognition rule base and identifying and extracting key primitives, including expanding the rule recognition base and identifying and extracting key primitives based on geometric features; performing topological checks and corrections on the identified primitives; 3D reconstruction of the mine design drawings, including sorting and assigning values ​​to step lines, processing and assigning values ​​to entrance and exit trenches, and generating 3D regions based on improved Delaunay triangulation; and mine compliance assessment based on the design model. Compared with existing technologies, this invention fills the gap in the field of 3D reconstruction of mine design drawings, providing intuitive and visually appealing design model data, and improving the accuracy of mine compliance construction.

Description

Technical Field

[0001] This invention discloses a method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings, belonging to the field of open-pit mine image processing technology. Background Technology

[0002] 3D Model Construction and Parameter Extraction of Open-Pit Mines Based on CAD Design Drawings: Design parameter extraction is another fundamental task for compliance inspection. However, mine design data is stored in two-dimensional data in DWG format, i.e., the mine design model. This format has poor visibility, making it difficult to intuitively analyze and check mining parameters. To more clearly demonstrate the actual structure and mining process of the mine, and to provide more intuitive data support for mine supervision, 3D reconstruction based on the mine design model is particularly important.

[0003] Slope morphology is a crucial factor in compliance testing, directly impacting the stability and safety of a mine. Slopes that are too steep or too shallow can lead to geological disasters such as landslides and collapses, posing a serious threat to mining operations and personnel safety. Therefore, a reasonable slope morphology safety assessment is a vital aspect of mine safety management. This invention employs a quantitative approach to slope morphology safety assessment: based on actual mine data and design data, a mathematical model is used to quantitatively analyze the stability of the slope morphology. This aims to accurately calculate the safety factor of the slope morphology, providing a reliable basis for mine safety assessments. Summary of the Invention

[0004] The purpose of this invention is to provide a method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings, in order to solve the problems in the existing technology that traditional mine design model data is not intuitive and has poor visibility, and that existing methods cannot quantitatively analyze the compliance construction status of mines.

[0005] Methods for 3D reconstruction and compliance assessment of open-pit mines based on CAD design drawings include:

[0006] Step 1. Data preprocessing based on CAD design drawings, including map sheet division and data registration;

[0007] Step 2. Construct a primitive recognition rule base and perform key primitive recognition and extraction, including the expansion of the rule recognition base and key primitive recognition and extraction based on geometric features;

[0008] Step 3. Perform topological checks and corrections on the identified primitives;

[0009] Step 4. 3D reconstruction of the mine design drawing, including sorting and assigning values ​​to the step lines, processing and assigning values ​​to the entrance and exit trenches, and generating 3D regions based on the improved Delaunay triangulation.

[0010] Step 5. Mine compliance assessment based on design model.

[0011] Step 1 includes: Step 1.1. Obtaining the mine CAD design drawings and performing data preprocessing, dividing the CAD design drawings into sheets, and generating the mine's top view and cross-sectional view;

[0012] Step 1.2. Geographic registration is performed based on the feature points of the mine's top view and cross-section to ensure that the spatial positions of the drawings are consistent. Feature points include mine road exits and corner points of different platforms.

[0013] Step 2 includes, Step 2.1. In the top view of the design model, the graphic elements are divided into two categories: one category is the graphic elements necessary for automatic modeling, including the slope bottom line, slope top line, entrance and exit ditch, and elevation information; the other category is the graphic elements that do not need to be identified, including the slope indication line.

[0014] Step 2.2. Based on the expansion of the rule recognition library, identify the text information in the top view as elevation information and remove the plus sign and unit;

[0015] Step 2.3. Based on the expansion of the rule recognition library, identify non-closed polylines in the top view as step lines and closed polylines as inlet / outlet ditches;

[0016] Step 2.4. Distinguish between the top and bottom slopes of the step line. Take any step line and find any segment of the slope line that intersects with the step line. Obtain the vertex Q outside the intersection point of the slope line and the step line. Connect the starting vertex of the step line to close the step line. Determine the spatial relationship between the closed plane and Q. If point Q is in the closed plane, the step line is the top slope line; otherwise, it is the bottom slope line.

[0017] Step 3 includes identifying and correcting dangling nodes, spurious nodes, overlapping and intersecting segments;

[0018] Step 3.1. Identifying and correcting dangling nodes includes identifying and traversing the structure of primitive objects, abstracting primitive objects into graph structures, the structure of primitive objects including vertices and edges, treating vertices as nodes in the graph structure, and treating edges as the connection relationships between nodes;

[0019] Determine the number of nodes connected to each node in the graph structure. The number of nodes is equal to the degree of the node. If the degree is 3, it is a topology error caused by a dangling node.

[0020] Step 3.2. Identifying and correcting pseudo-nodes includes identifying pseudo-nodes as endpoints of line segments and points of contact between two line segments. Extracting all basic primitives in the design drawing, including points and line segments, and constructing the graph structure; traversing all nodes with a degree of 1, identifying duplicate nodes as pseudo-nodes; obtaining the nodes connected to the pseudo-nodes and determining whether the pseudo-nodes are redundant. According to the Douglas-Puk algorithm, if the distance from the pseudo-node to the line is less than a threshold, it is a redundant node, deleted, and the nodes at both ends of the pseudo-node are connected; otherwise, the pseudo-node is connected to the original line segment.

[0021] Step 3.3. Identifying and correcting overlapping and intersecting line segments includes checking whether the projections of two line segments on the x-axis and y-axis overlap. Specifically, it involves determining whether the larger endpoint of one line segment's x-coordinate is smaller than the smaller endpoint of the other line segment's x-coordinate; if so, the two line segments do not overlap on the x-axis. Similarly, it involves determining whether the larger endpoint of one line segment's y-coordinate is smaller than the smaller endpoint of the other line segment's y-coordinate; if so, the two line segments do not overlap on the y-axis. If the two line segments do not overlap on either the x-axis or y-axis, they cannot intersect.

[0022] If line segments AB and CD satisfy If the line segments intersect, then they are intersecting; otherwise, they do not intersect. Let A and B be two endpoints of one line segment, and C and D be two endpoints of another line segment.

[0023] If line segments AB and CD satisfy If the two line segments are aligned, they coincide; otherwise, they do not.

[0024] Step 4 includes, Step 4.1. Sorting and assigning values ​​to the step lines, which includes sorting the graphic elements corresponding to the platform from the outside to the inside, sorting them according to the minimum distance from the step line to the centroid, and assigning elevation values ​​in sequence according to the sorted results.

[0025] Calculate the area of ​​the closed figure enclosed by all nodes of each step line. And find the minimum area. The formula for calculating the corresponding step line is:

[0026] ;

[0027] In the formula, For the first Node coordinates The total number of nodes. , ;

[0028] Calculate the minimum area The centroid of the closed figure enclosed by the nodes of the corresponding step lines :

[0029] ;

[0030] ;

[0031] In the formula, Center of mass Coordinates divide the closed figure into There are n triangles, and the number of triangles is equal to the total number of nodes. The centroid of the triangle is The area is ;

[0032] No. The formula for calculating the centroid of a triangle is:

[0033] ;

[0034] ;

[0035] In the formula, , , The coordinates of the triangle vertices;

[0036] Calculate the maximum and minimum distances from the step line to the centroid P. Extract the step lines corresponding to the maximum and minimum distances and use them as the outermost step lines. Continue to calculate the maximum and minimum distances from the remaining step lines to the centroid P. Repeat the extraction of step lines until all step lines are sorted.

[0037] Step 4 includes step 4.2. separating the closed polyline into two non-intersecting polylines, the steps of which are as follows:

[0038] For each closed polyline, construct a constrained Delaunay triangulation, treating all nodes as a set of vertices and all edges as a set of constrained edges, and use a point-by-point insertion algorithm to obtain the constrained Delaunay triangulation.

[0039] Construct the skeleton lines and find the Delaunay triangle with the largest area. Calculate the centroid M and add M to the skeleton line; search Adjacent triangles and will and Add the skeleton line to the midpoint N of the adjacent edge; search For other adjacent triangles, excluding those already included, repeat the search. Adjacent triangles Until no new adjacent triangles exist;

[0040] For each polyline, calculate and search for segments that intersect with the polyline skeleton and delete them.

[0041] Step 4 includes step 4.3. Based on the characteristics of different areas, the 3D reconstructed area is divided into four categories: bottom surface, steps, sidewalls, and access trenches. The steps are as follows:

[0042] Add nodes to sparse areas and reduce nodes in dense areas;

[0043] The triangulation network is generated by point-by-point insertion. The step line is used as a constraint condition. The triangle is checked to see if the triangle uses the line segment of the step line as the edge. If not, the triangle is changed and the optimal triangle is rechecked.

[0044] The added rule is that if the projection of the center of a triangle onto the XOY plane is not on the two step lines but on the plane enclosed by the XOY plane, then it is deleted; the three points of a triangle cannot be on the same plane, and if they are on the same plane, they can exchange their common side with any adjacent triangle.

[0045] Based on the side wall, new nodes and constraints are added, and the nodes entering and exiting the trench are added as new nodes;

[0046] An improved point-by-point insertion algorithm is adopted to traverse and select the triangles whose endpoints are projected into the XOY plane and then projected into the XOY plane of the inlet and outlet trench.

[0047] The starting node connecting the inlet and outlet trenches is considered as a straight line L, and the tangent plane passing through line L and perpendicular to the XOY plane is... If the entry / exit node is on the plane The projection of the triangle falls on the triangle. If the projection is inside the triangle, insert and construct a new triangle and check for optimality;

[0048] The entry and exit segments of the trench are added to the triangulation network as constraints.

[0049] Step 5 includes dividing the mine into multiple evaluation units, classifying risk levels and calculating weights based on the differences between current mining parameters and design parameters within each evaluation unit, and proposing a compliance assessment index (CAM). By scoring and weighting the risk components, the overall slope morphology safety rating is calculated by comprehensively evaluating the sub-item scores. The calculation formula is as follows:

[0050] ;

[0051] In the formula, Indicates the first The risk factor in the first Scores on each assessment or evaluation unit; Indicates the first The weights corresponding to each risk element; Iterate from 1 to 4. Traverse from 1 to , To examine the total number of units that received evaluation.

[0052] Compared with the prior art, the present invention has the following beneficial effects: it makes up for the shortcomings in mine design. Figure 3 Filling a gap in the field of mine reconstruction, the design model data is intuitive and highly visible, improving the accuracy of mine compliance construction. Attached Figure Description

[0053] Figure 1 This is a technical flowchart of the present invention.

[0054] Figure 2 It is a top view of the mine generated after the CAD design drawing of the mine is divided into sheets.

[0055] Figure 3 The CAD design drawings for the mine are divided into sheets to generate cross-sectional views of the mine.

[0056] Figure 4 It is a topology error graph of the suspended node type.

[0057] Figure 5 This is a diagram of a pseudo-node.

[0058] Figure 6 This is a schematic diagram showing the result after assigning values ​​to the step lines.

[0059] Figure 7 This is a schematic diagram of the constrained Delaunay triangulation result of constructing the ramp.

[0060] Figure 8 This is the result of skeleton line extraction.

[0061] Figure 9 This is a diagram showing the results of the input / output ditch assignment.

[0062] Figure 10 This is a 3D reconstruction result based on the improved Delaunay triangulation.

[0063] Figure 11 This is a diagram showing the results of a mine compliance assessment based on a design model. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0065] Methods for 3D reconstruction and compliance assessment of open-pit mines based on CAD design drawings include:

[0066] Step 1. Data preprocessing based on CAD design drawings, including map sheet division and data registration;

[0067] Step 2. Construct a primitive recognition rule base and perform key primitive recognition and extraction, including the expansion of the rule recognition base and key primitive recognition and extraction based on geometric features;

[0068] Step 3. Perform topological checks and corrections on the identified primitives;

[0069] Step 4. 3D reconstruction of the mine design drawing, including sorting and assigning values ​​to the step lines, processing and assigning values ​​to the entrance and exit trenches, and generating 3D regions based on the improved Delaunay triangulation.

[0070] Step 5. Mine compliance assessment based on design model.

[0071] Step 1 includes: Step 1.1. Obtaining the mine CAD design drawings and performing data preprocessing, dividing the CAD design drawings into sheets, and generating the mine's top view and cross-sectional view;

[0072] Step 1.2. Geographic registration is performed based on the feature points of the mine's top view and cross-section to ensure that the spatial positions of the drawings are consistent. Feature points include mine road exits and corner points of different platforms.

[0073] Step 2 includes, Step 2.1. In the top view of the design model, the graphic elements are divided into two categories: one category is the graphic elements necessary for automatic modeling, including the slope bottom line, slope top line, entrance and exit ditch, and elevation information; the other category is the graphic elements that do not need to be identified, including the slope indication line.

[0074] Step 2.2. Based on the expansion of the rule recognition library, identify the text information in the top view as elevation information and remove the plus sign and unit;

[0075] Step 2.3. Based on the expansion of the rule recognition library, identify non-closed polylines in the top view as step lines and closed polylines as inlet / outlet ditches;

[0076] Step 2.4. Distinguish between the top and bottom slopes of the step line. Take any step line and find any segment of the slope line that intersects with the step line. Obtain the vertex Q outside the intersection point of the slope line and the step line. Connect the starting vertex of the step line to close the step line. Determine the spatial relationship between the closed plane and Q. If point Q is in the closed plane, the step line is the top slope line; otherwise, it is the bottom slope line.

[0077] Step 3 includes identifying and correcting dangling nodes, spurious nodes, overlapping and intersecting segments;

[0078] Step 3.1. Identifying and correcting dangling nodes includes identifying and traversing the structure of primitive objects, abstracting primitive objects into graph structures, the structure of primitive objects including vertices and edges, treating vertices as nodes in the graph structure, and treating edges as the connection relationships between nodes;

[0079] Determine the number of nodes connected to each node in the graph structure. The number of nodes is equal to the degree of the node. If the degree is 3, it is a topology error caused by a dangling node.

[0080] Step 3.2. Identifying and correcting pseudo-nodes includes identifying pseudo-nodes as endpoints of line segments and points of contact between two line segments. Extracting all basic primitives in the design drawing, including points and line segments, and constructing the graph structure; traversing all nodes with a degree of 1, identifying duplicate nodes as pseudo-nodes; obtaining the nodes connected to the pseudo-nodes and determining whether the pseudo-nodes are redundant. According to the Douglas-Puk algorithm, if the distance from the pseudo-node to the line is less than a threshold, it is a redundant node, deleted, and the nodes at both ends of the pseudo-node are connected; otherwise, the pseudo-node is connected to the original line segment.

[0081] Step 3.3. Identifying and correcting overlapping and intersecting line segments includes checking whether the projections of two line segments on the x-axis and y-axis overlap. Specifically, it involves determining whether the larger endpoint of one line segment's x-coordinate is smaller than the smaller endpoint of the other line segment's x-coordinate; if so, the two line segments do not overlap on the x-axis. Similarly, it involves determining whether the larger endpoint of one line segment's y-coordinate is smaller than the smaller endpoint of the other line segment's y-coordinate; if so, the two line segments do not overlap on the y-axis. If the two line segments do not overlap on either the x-axis or y-axis, they cannot intersect.

[0082] If line segments AB and CD satisfy If the line segments intersect, then they are intersecting; otherwise, they do not intersect. Let A and B be two endpoints of one line segment, and C and D be two endpoints of another line segment.

[0083] If line segments AB and CD satisfy If the two line segments are aligned, they coincide; otherwise, they do not.

[0084] Step 4 includes, Step 4.1. Sorting and assigning values ​​to the step lines, which includes sorting the graphic elements corresponding to the platform from the outside to the inside, sorting them according to the minimum distance from the step line to the centroid, and assigning elevation values ​​in sequence according to the sorted results.

[0085] Calculate the area of ​​the closed figure enclosed by all nodes of each step line. And find the minimum area. The formula for calculating the corresponding step line is:

[0086] ;

[0087] In the formula, For the first Node coordinates The total number of nodes. , ;

[0088] Calculate the minimum area The centroid of the closed figure enclosed by the nodes of the corresponding step lines :

[0089] ;

[0090] ;

[0091] In the formula, Center of mass Coordinates divide the closed figure into There are n triangles, and the number of triangles is equal to the total number of nodes. The centroid of the triangle is The area is ;

[0092] No. The formula for calculating the centroid of a triangle is:

[0093] ;

[0094] ;

[0095] In the formula, , , The coordinates of the triangle vertices;

[0096] Calculate the maximum and minimum distances from the step line to the centroid P. Extract the step lines corresponding to the maximum and minimum distances and use them as the outermost step lines. Continue to calculate the maximum and minimum distances from the remaining step lines to the centroid P. Repeat the extraction of step lines until all step lines are sorted.

[0097] Step 4 includes step 4.2. separating the closed polyline into two non-intersecting polylines, the steps of which are as follows:

[0098] For each closed polyline, construct a constrained Delaunay triangulation, treating all nodes as a set of vertices and all edges as a set of constrained edges, and use a point-by-point insertion algorithm to obtain the constrained Delaunay triangulation.

[0099] Construct the skeleton lines and find the Delaunay triangle with the largest area. Calculate the centroid M and add M to the skeleton line; search Adjacent triangles and will and Add the skeleton line to the midpoint N of the adjacent edge; search For other adjacent triangles, excluding those already included, repeat the search. Adjacent triangles Until no new adjacent triangles exist;

[0100] For each polyline, calculate and search for segments that intersect with the polyline skeleton and delete them.

[0101] Step 4 includes step 4.3. Based on the characteristics of different areas, the 3D reconstructed area is divided into four categories: bottom surface, steps, sidewalls, and access trenches. The steps are as follows:

[0102] Add nodes to sparse areas and reduce nodes in dense areas;

[0103] The triangulation network is generated by point-by-point insertion. The step line is used as a constraint condition. The triangle is checked to see if the triangle uses the line segment of the step line as the edge. If not, the triangle is changed and the optimal triangle is rechecked.

[0104] The added rule is that if the projection of the center of a triangle onto the XOY plane is not on the two step lines but on the plane enclosed by the XOY plane, then it is deleted; the three points of a triangle cannot be on the same plane, and if they are on the same plane, they can exchange their common side with any adjacent triangle.

[0105] Based on the side wall, new nodes and constraints are added, and the nodes entering and exiting the trench are added as new nodes;

[0106] An improved point-by-point insertion algorithm is adopted to traverse and select the triangles whose endpoints are projected into the XOY plane and then projected into the XOY plane of the inlet and outlet trench.

[0107] The starting node connecting the inlet and outlet trenches is considered as a straight line L, and the tangent plane passing through line L and perpendicular to the XOY plane is... If the entry / exit node is on the plane The projection of the triangle falls on the triangle. If the projection is inside the triangle, insert and construct a new triangle and check for optimality;

[0108] The entry and exit segments of the trench are added to the triangulation network as constraints.

[0109] Step 5 includes dividing the mine into multiple evaluation units, classifying risk levels and calculating weights based on the differences between current mining parameters and design parameters within each evaluation unit, and proposing a compliance assessment index (CAM). By scoring and weighting the risk components, the overall slope morphology safety rating is calculated by comprehensively evaluating the sub-item scores. The calculation formula is as follows:

[0110] ;

[0111] In the formula, Indicates the first The risk factor in the first Scores on each assessment or evaluation unit; Indicates the first The weights corresponding to each risk element; Iterate from 1 to 4. Traverse from 1 to , To examine the total number of units that received evaluation.

[0112] In the top view of the design model, the graphic elements can be divided into two main categories: (1) graphic elements necessary for automatic modeling, including slope bottom line, slope top line, entrance and exit ditch, and elevation information. (2) graphic elements that do not need to be identified, including slope indication lines. However, because the elevation information is incomplete, the elevation information in the profile view is needed as a supplement.

[0113] Overhanging nodes in CAD drawings are usually caused by insufficient drawing precision, inaccurate connection of endpoints during manual drawing, or misalignment of endpoints during drawing modification and automatic drawing generation. These nodes may be difficult to detect visually, but they can have a serious impact on automated data analysis and model reconstruction.

[0114] A pseudo node is a point where the endpoints of a line segment are merely the contact points between two line segments. The point where two line segments intersect is the contact point between their endpoints, and a pseudo node exists there. Pseudo nodes are usually formed when line segments are not drawn all at once during the production process, but are drawn in multiple or segmented steps.

[0115] During the drafting process, operators may unintentionally copy and paste certain line segment elements, causing one line segment to become multiple overlapping line segments; or, when drawing a graphic, if vertices are not created correctly, two line segments that should intersect at the vertices may intersect across line segments.

[0116] In mine design drawings, access trenches are usually represented as independent layers. During their creation, the two ends of the same platform are often connected to form closed polylines. However, in subsequent graphic processing (such as elevation assignment and surface generation), these closed polylines need to be separated into two non-intersecting polylines for further analysis and processing. Due to the uneven distribution of step line nodes in the design drawings, it is necessary to ensure the smoothness and accuracy of the subsequent model.

[0117] The technical flowchart of this invention is as follows: Figure 1As shown, the steps include data preprocessing based on CAD design drawings, including map sheet division and data registration; constructing a rule base for graphic element recognition and identifying and extracting key graphic elements, including expanding the rule recognition base and identifying and extracting key graphic elements based on geometric features; performing topological checks and corrections on the identified graphic elements; 3D reconstruction of the mine design drawings, including sorting and assigning values ​​to step lines, processing and assigning values ​​to entrance and exit trenches, and generating 3D regions based on improved Delaunay triangulation; and mine compliance assessment based on the design model.

[0118] After the mine CAD design drawings are divided into sheets, a top view of the mine is generated, as shown below. Figure 2 As shown, the pink line segment is the slope baseline, the cyan line segment is the roof breaking line, the short black line is the slope indication line, the red characters represent the elevation data of the area shown, and the red line segment represents the inclined slope; the mine profile is shown below. Figure 3 As shown; the topology error diagram for dangling node type is as follows. Figure 4 As shown, point A is the dangling node that needs to be identified and corrected; a schematic diagram of the pseudo-node is shown below. Figure 5 As shown, adjacent intersections of line segment AB are pseudo-nodes; the result after assigning values ​​to the step line is illustrated. Figure 6 As shown, the gap is a ramp; the extracted skeleton lines are shown in the following figure. Figure 7 , Figure 8 As shown in the figure; the result of the inlet and outlet ditch assignment is shown in the figure. Figure 9 As shown; the 3D reconstruction result based on the improved Delaunay triangulation is shown in the figure. Figure 10 As shown; the mine compliance assessment diagram based on the design model is as follows. Figure 11 As shown, the risks include platform width, slope angle, and final edge angle. These problems are mainly distributed on the west side of the ore body, with higher risk values ​​in the northwest direction, indicating significant risks in this area.

[0119] The above 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 with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings, characterized in that: include: Step 1. Data preprocessing based on CAD design drawings, including map sheet division and data registration; Step 2. Construct a primitive recognition rule base and perform key primitive recognition and extraction, including the expansion of the rule recognition base and key primitive recognition and extraction based on geometric features; Step 3. Perform topological checks and corrections on the identified primitives; Step 4. 3D reconstruction of the mine design drawing, including sorting and assigning values ​​to the step lines, processing and assigning values ​​to the entrance and exit trenches, and generating 3D regions based on the improved Delaunay triangulation. Step 5. Mine compliance assessment based on design model; Step 2 includes, Step 2.

1. In the top view of the design model, the graphic elements are divided into two categories: one category is the graphic elements necessary for automatic modeling, including the slope bottom line, slope top line, entrance and exit ditch, and elevation information; the other category is the graphic elements that do not need to be identified, including the slope indication line. Step 2.

2. Based on the expansion of the rule recognition library, identify the text information in the top view as elevation information and remove the plus sign and unit; Step 2.

3. Based on the expansion of the rule recognition library, identify non-closed polylines in the top view as step lines and closed polylines as inlet / outlet ditches; Step 2.

4. Distinguish between the top and bottom slopes of the step line. Take any step line and find any segment of the slope line that intersects with the step line. Obtain the vertex Q other than the intersection of the slope line and the step line. Connect the starting vertex of the step line to close the step line. Determine the spatial relationship between the closed plane and Q. If point Q is in the closed plane, the step line is the top slope line; otherwise, it is the bottom slope line. Step 5 includes dividing the mine into multiple evaluation units, classifying risk levels and calculating weights based on the differences between current mining parameters and design parameters within each evaluation unit, and proposing a compliance assessment index (CAM). By scoring and weighting the risk components, the overall slope morphology safety rating is calculated by comprehensively evaluating the sub-item scores. The calculation formula is as follows: ； In the formula, Indicates the first The risk factor in the first Scores on each assessment or evaluation unit; Indicates the first The weights corresponding to each risk element; Iterate from 1 to 4. Traverse from 1 to , To examine the total number of units that received evaluation.

2. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 1, characterized in that, Step 1 This includes step 1.

1. Obtaining the mine's CAD design drawings and performing data preprocessing, dividing the CAD design drawings into sheets, and generating the mine's top view and cross-sectional view; Step 1.

2. Geographic registration is performed based on the feature points of the mine's top view and cross-section to ensure that the spatial positions of the drawings are consistent. Feature points include mine road exits and corner points of different platforms.

3. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 2, characterized in that, Step 3 includes identifying and correcting dangling nodes, spurious nodes, overlapping and intersecting segments; Step 3.

1. Identifying and correcting dangling nodes includes identifying and traversing the structure of primitive objects, abstracting primitive objects into graph structures, the structure of primitive objects including vertices and edges, treating vertices as nodes in the graph structure, and treating edges as the connection relationships between nodes; Determine the number of nodes connected to each node in the graph structure. The number of nodes is equal to the degree of the node. If the degree is 3, it is a topology error caused by a dangling node.

4. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 3, characterized in that, Step 3.

2. Identifying and correcting pseudo-nodes includes identifying the endpoints of line segments and the contact points between two line segments, extracting all basic graphic elements in the design drawing, including points and line segments, and constructing the graph structure. Iterate through all nodes with a degree of 1. If there are duplicate nodes, they are pseudo nodes. Collect the nodes connected to the pseudo nodes and determine whether the pseudo nodes are redundant. According to the Douglas-Puk algorithm, if the distance from the pseudo node to the line is less than the threshold, it is a redundant node. Delete it and connect the nodes at both ends of the pseudo node. Otherwise, connect the pseudo node to the original line segment.

5. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 4, characterized in that, Step 3.

3. Identifying and correcting overlapping and intersecting line segments includes checking whether the projections of two line segments on the x-axis and y-axis overlap. Specifically, it involves determining whether the larger endpoint of one line segment's x-coordinate is smaller than the smaller endpoint of the other line segment's x-coordinate; if so, the two line segments do not overlap on the x-axis. Similarly, it involves determining whether the larger endpoint of one line segment's y-coordinate is smaller than the smaller endpoint of the other line segment's y-coordinate; if so, the two line segments do not overlap on the y-axis. If the two line segments do not overlap on either the x-axis or y-axis, they cannot intersect. If line segments AB and CD satisfy If the line segments intersect, then they are intersecting; otherwise, they do not intersect. Let A and B be two endpoints of one line segment, and C and D be two endpoints of another line segment. If line segments AB and CD satisfy If the two line segments are aligned, they coincide; otherwise, they do not.

6. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 5, characterized in that, Step 4 includes, Step 4.

1. Sorting and assigning values ​​to the step lines, which includes sorting the graphic elements corresponding to the platform from the outside to the inside, sorting them according to the minimum distance from the step line to the centroid, and assigning elevation values ​​in sequence according to the sorted results. Calculate the area of ​​the closed figure enclosed by all nodes of each step line. And find the minimum area. The formula for calculating the corresponding step line is: ； In the formula, For the first Node coordinates The total number of nodes. , ; Calculate the minimum area The centroid of the closed figure enclosed by the nodes of the corresponding step lines : ； ； In the formula, Center of mass Coordinates divide the closed figure into There are n triangles, and the number of triangles is equal to the total number of nodes. The centroid of the triangle is The area is ; No. The formula for calculating the centroid of a triangle is: ； ； In the formula, , , The coordinates of the triangle vertices; Calculate the maximum and minimum distances from the step line to the centroid P. Extract the step lines corresponding to the maximum and minimum distances and use them as the outermost step lines. Continue to calculate the maximum and minimum distances from the remaining step lines to the centroid P. Repeat the extraction of step lines until all step lines are sorted.

7. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings according to claim 6, characterized in that, Step 4 includes step 4.

2. separating the closed polyline into two non-intersecting polylines, the steps of which are as follows: For each closed polyline, construct a constrained Delaunay triangulation, treating all nodes as a set of vertices and all edges as a set of constrained edges, and use a point-by-point insertion algorithm to obtain the constrained Delaunay triangulation. Construct the skeleton lines and find the Delaunay triangle with the largest area. Calculate the centroid M and add M to the skeleton line; search Adjacent triangles and will and Add the skeleton line to the midpoint N of the adjacent edge; search For other adjacent triangles, excluding those already included, repeat the search. Adjacent triangles Until no new adjacent triangles exist; For each polyline, calculate and search for segments that intersect with the polyline skeleton and delete them.

8. The method for three-dimensional reconstruction and compliance assessment of open-pit mines based on CAD design drawings as described in claim 7, characterized in that, Step 4 includes step 4.

3. Based on the characteristics of different areas, the 3D reconstructed area is divided into four categories: bottom surface, steps, sidewalls, and access trenches. The steps are as follows: Add nodes to sparse areas and reduce nodes in dense areas; The triangulation network is generated by point-by-point insertion. The step line is used as a constraint condition. The triangle is checked to see if the triangle uses the line segment of the step line as the edge. If not, the triangle is changed and the optimal triangle is rechecked. The added rule is that if the projection of the center of a triangle onto the XOY plane is not on the two step lines but on the plane enclosed by the XOY plane, then it is deleted; the three points of a triangle cannot be on the same plane, and if they are on the same plane, they can exchange their common side with any adjacent triangle. Based on the side wall, new nodes and constraints are added, and the nodes entering and exiting the trench are added as new nodes; An improved point-by-point insertion algorithm is adopted to traverse and select the triangles whose endpoints are projected into the XOY plane and then projected into the XOY plane of the inlet and outlet trench. The starting node connecting the inlet and outlet trenches is considered as a straight line L, and the tangent plane passing through line L and perpendicular to the XOY plane is... If the entry / exit node is on the plane The projection of the triangle falls on the triangle. If the projection is inside the triangle, insert and construct a new triangle and check for optimality; The entry and exit segments of the trench are added to the triangulation network as constraints.

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