A tunnel blasting quality assessment method based on 3D point cloud information

Abstract

The present invention discloses a method for assessing the quality of tunnel blasting based on three-dimensional point cloud information, comprising obtaining three-dimensional point cloud data of the tunnel before blasting, extracting information about the tunnel's central axis, and fitting a three-dimensional model of the blasting area before blasting; obtaining three-dimensional point cloud data of the tunnel after blasting, performing thinning and triangulation processing, and obtaining a three-dimensional model of the blasting area after blasting; performing Boolean operations on the three-dimensional models before and after blasting, and applying the simplex method to the three-dimensional model calculation to obtain over-break and under-break data information at various locations; introducing a comprehensive integrated weighting method weight model of multiple theoretical models to quantitatively analyze various blasting indicators and obtain tunnel blasting quality assessment results. The present invention establishes three-dimensional models of the tunnel blasting area before and after blasting using tunnel point cloud data and compares them, which can intuitively display the over-break and under-break status at various locations and comprehensively, effectively, objectively, and quantitatively assess the blasting quality of the tunnel.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel blasting, and in particular to a tunnel blasting quality assessment method based on three-dimensional point cloud information. Background Art

[0002] The drilling and blasting method currently plays a crucial role in tunnel construction. Overbreak and underbreak are inevitable during tunnel blasting. When overbreak occurs, fiber concrete needs to be sprayed promptly. In more severe cases, not only does the steel frame need to be fabricated, but it also requires the installation of special-shaped steel frames and the addition of reinforced mesh. Underbreak requires either manual mechanical chiseling or secondary blasting, depending on the situation. The quality of tunnel blasting plays a crucial role in the progress of tunnel construction, the economic efficiency of explosive charging, and the workload of workers. A comprehensive, comprehensive, and objective tunnel blasting quality assessment report not only provides a profound summary of the current blasting operation but also provides sufficient data support and plan selection for the next tunnel blasting operation.

[0003] A drawback of existing technologies is that tunnel blasting quality assessment is often based on the subjective experience of on-site construction personnel. These qualitative analyses lack reliable theoretical support and corresponding measurement methods, inevitably leading to cognitive biases in tunnel blasting quality. Furthermore, tunnel blasting quality evaluation indicators and results reports are typically presented in two-dimensional graphs, which fail to visually demonstrate changes in tunnel blasting surrounding rock overbreak and underbreak volumes over time, and thus provide limited feedback on tunnel blasting quality. Therefore, it is urgent to develop a three-dimensional visualization model to display overbreak and underbreak information before and after tunnel blasting, as well as a quantitative method for evaluating tunnel blasting quality. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology. To achieve the above purpose, a tunnel blasting quality assessment method based on three-dimensional point cloud information is adopted to solve the problems raised in the above background technology.

[0005] A tunnel blasting quality assessment method based on three-dimensional point cloud information, comprising the following steps:

[0006] Obtain 3D point cloud data of the tunnel lining surface and the front pre-support section before blasting, extract the tunnel centerline, and combine the location information of the tunnel centerline with the tunnel design contour line to fit the 3D model of the blasting area before blasting;

[0007] Obtain the 3D point cloud data of the tunnel after blasting, and perform thinning and triangulation on the 3D point cloud data to obtain a 3D model of the blasting area after blasting;

[0008] Perform Boolean operations on the 3D models before and after blasting, and apply the simplex method to the 3D model calculation to obtain over-excavation and under-excavation data at each location;

[0009] The weight model of comprehensive integrated weighting method of multi-theoretical models is introduced to quantitatively analyze various blasting indicators and obtain the blasting quality assessment results of the tunnel.

[0010] As a further solution of the present invention, the specific steps of obtaining the three-dimensional point cloud data of the tunnel lining surface and the front pre-support section before blasting, extracting the tunnel centerline, and fitting the three-dimensional model of the blasting area before blasting by combining the position information of the tunnel centerline and the tunnel design contour line include:

[0011] First, before blasting, the current tunnel section is scanned using a 3D scanner to obtain 3D point cloud data of the current tunnel lining surface and the front pre-support section;

[0012] Based on the 3D point cloud data, the coordinate system of the lining surface of the current tunnel is established, and the central axis corresponding to the current tunnel lining section is obtained by linear mean fitting based on the coordinate data;

[0013] Then, based on the position information of the central axis and the tunnel design contour line, cyclic footage and stretching are performed to obtain a three-dimensional model of the blasting area before blasting.

[0014] As a further solution of the present invention, the specific steps of obtaining the three-dimensional point cloud data of the tunnel after blasting, and performing thinning and triangulation processing on the three-dimensional point cloud data to obtain the three-dimensional model of the blasting area after blasting include:

[0015] Place the 3D scanner at the same position as before blasting to scan the blasting surface and obtain 3D point cloud data;

[0016] Read the point cloud coordinate data in the 3D point cloud data, set the origin position and update the progressive point cloud as the reference point, delete the point cloud whose distance from the reference point is less than the preset threshold R, perform thinning processing and save;

[0017] The three adjacent point clouds after thinning are triangulated to obtain a three-dimensional model of the blasting area after blasting.

[0018] As a further solution of the present invention, the specific steps of performing Boolean operations on the three-dimensional models before and after blasting and applying the simplex method to the three-dimensional model calculation to obtain overbreak and underbreak data information at various positions include:

[0019] Perform Boolean operations based on the obtained three-dimensional models of the blasting area before and after blasting;

[0020] The simplex method is used to obtain the centroid, surface area, volume and centroid information of the triangular elements on the outer surface of each model;

[0021] Locate the over-excavation and under-excavation points, and obtain the tunnel over-excavation and under-excavation area, over-excavation and under-excavation volume, and average over-excavation and under-excavation information.

[0022] As a further solution of the present invention, the specific steps of introducing a comprehensive integrated weighting method weight model of multiple theoretical models to quantitatively analyze various blasting indicators and obtain the tunnel blasting quality assessment results include:

[0023] First, evaluation indicators are obtained, including maximum overbreak, average linear overbreak, maximum underbreak, maximum step size between two blastholes, overbreak area, measured cross-sectional area, overbreak rate, overbreak volume, and blasthole utilization rate;

[0024] Based on the multi-theoretical model, a comprehensive integrated empowerment weight model is established;

[0025] The design parameters of the blasting surface and the Boolean operation results of the three-dimensional model before and after blasting are input into the solution formula of the blasting quality score of the comprehensive integrated weighted model to obtain the evaluation results.

[0026] As a further solution of the present invention: the solution formula for the blasting mass fraction is:

[0027]

[0028] Among them, X i is the weight coefficient of the evaluation index, Y i is the evaluation score of the evaluation index.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] Using this technical solution, 3D point cloud data of the tunnel blasting area before and after blasting is collected to generate 3D models. Comparing the 3D data models before and after blasting visually demonstrates the over- and under-break conditions at various locations. Boolean operations are performed on the 3D models, and model information is statistically analyzed using the simplex method. Finally, a comprehensive integrated weighting model based on multiple theoretical models is used for integrated calculations to obtain the final evaluation results. This method enables a comprehensive, effective, objective, and quantitative assessment of tunnel blasting quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings:

[0032] Figure 1 A schematic diagram of the steps of a tunnel blasting quality assessment method according to some embodiments disclosed in this application;

[0033] Figure 2 A flowchart of three-dimensional visual quantitative evaluation of tunnel blasting quality according to some embodiments disclosed in this application;

[0034] Figure 3 This is a schematic diagram of the tunnel blasting area according to some embodiments disclosed in this application. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Please refer to Figure 1 and Figure 2 In an embodiment of the present invention, a method for evaluating tunnel blasting quality based on three-dimensional point cloud information comprises the following steps:

[0037] Step S1: Obtain 3D point cloud data of the tunnel lining surface and the front pre-support section before blasting, extract the tunnel centerline, and combine the position information of the tunnel centerline and the tunnel design contour line to obtain a 3D model of the blasting area before blasting. The specific steps include:

[0038] First, before blasting, the current tunnel section is scanned using a 3D scanner to obtain 3D point cloud data of the current tunnel lining surface and the front pre-support section;

[0039] Based on the 3D point cloud data, the coordinate system of the lining surface of the current tunnel is established, and the central axis corresponding to the current tunnel lining section is obtained by linear mean fitting based on the coordinate data;

[0040] Then, based on the position information of the central axis and the tunnel design contour line, cyclic footage and stretching are performed to obtain a three-dimensional model of the blasting area before blasting.

[0041] In this embodiment, a three-dimensional model of the tunnel blasting area before blasting is first established;

[0042] (1) Scanning tunnel cross section

[0043] like Figure 3 The figure shows a schematic diagram of various areas of the tunnel before blasting. Before blasting, a 3D scanner is used to scan the current tunnel section to obtain 3D point cloud data of the current lining tunnel surface and the front pre-support section.

[0044] (2) Extracting the tunnel axis

[0045] The tunnel centerline contains information about the tunnel's posture and direction, so the geometry of the tunnel section at any location can be determined based on the information about the centerline. The method for determining the tunnel centerline is as follows:

[0046] 1. Open the collected 3D point cloud data of the tunnel lining surface in CAD. In this work, the Y-axis is the tunnel footage direction. Project the 3D point cloud data onto the XOY and YOZ planes. This can be achieved by opening the 2D XOY and YOZ interfaces in CAD. Next, extract the boundary point data of the tunnel lining section on the XOY and YOZ projection surfaces.

[0047] 2. The quadratic curve equation is used to fit the data points on the lining section boundary, and the parameters required for fitting the curve equation are obtained using the random sampling consensus algorithm (RANSAC).

[0048] 3. Extract the central axis of the tunnel lining section projected in the XOY and YOZ coordinate systems. The specific processing method is as follows:

[0049] Taking the projection surface in the XOY coordinate system as an example, based on the curve equation of one boundary, data points are collected at a certain frequency from the starting point to the end point in the curve equation. This is called point set A. Next, the intersection of each data point in point set A with the other boundary in the normal direction is determined, which is called point set B. The midpoint coordinates of the corresponding data points in point sets A and point set B are determined. The line connecting the midpoint coordinates is the central axis of the projection surface in this coordinate system.

[0050] This method can be further used to obtain the central axis of the projection surface in the YOZ coordinate system. The coordinate data of the central axis of the projection surface in the two coordinate systems can be extracted at equal intervals according to a certain frequency. Finally, the two central axes of the above projection surfaces are linearly mean fitted to obtain the central axis corresponding to the current tunnel lining section.

[0051] (3) 3D geometry fitting of blasting area

[0052] Each tunnel blast is typically conducted using a laser alignment device, with each blast typically lasting 1 to 3 meters. Therefore, the central axis of the blasting area adjacent to the tunnel lining generally aligns with the central axis determined above. Based on the design parameters of the tunnel profile and the location of the central axis of the blasting area, the 2D tunnel profile can be extruded along the central axis in CAD to form a 3D geometry. This geometry represents the 3D appearance of the tunnel under ideal blasting conditions, and is then saved as an STL file. This is because STL files are 3D models composed of triangular meshes, a simple and widely used format that facilitates comparison and calculations with the 3D tunnel model after blasting.

[0053] Step S2: Acquire the three-dimensional point cloud data of the tunnel after blasting, and perform thinning and triangulation processing on the three-dimensional point cloud data to obtain a three-dimensional model of the blasting area after blasting. The specific steps include:

[0054] Place the 3D scanner at the same position as before blasting to scan the blasting surface and obtain 3D point cloud data;

[0055] Read the point cloud coordinate data in the 3D point cloud data, set the origin position and update the progressive point cloud as the reference point, delete the point cloud whose distance from the reference point is less than the preset threshold R, perform thinning processing and save;

[0056] The three adjacent point clouds after thinning are triangulated to obtain a three-dimensional model of the blasting area after blasting.

[0057] In this embodiment, a three-dimensional model of the tunnel blasting area after blasting is established;

[0058] (1) Tunnel blasting surface scanning

[0059] To reduce the complexity of later data processing and facilitate comparison of tunnel geometry before and after blasting, a 3D scanner was placed in the same position to scan the blasting surface, thereby creating a 3D point cloud model of the tunnel blasting area. Because 3D point cloud data consists of discrete data points, the resulting 3D point cloud model is inconvenient for vector calculations and Boolean operations. Therefore, special processing is required to convert the 3D point cloud model into a continuous 3D geometry. Here, it is converted into a continuous model represented by triangular faces, also known as the STL file format.

[0060] (2) Point cloud thinning processing

[0061] Point cloud data has millimeter-level spatial resolution, and the amount of data collected per scan is typically measured in the billions. Converting this massive amount of point cloud data into a continuous model is not only time-consuming but can even render personal computers inoperable. Therefore, it is necessary to thin out the collected point cloud data. This process can be performed in MATLAB, and the main ideas are as follows:

[0062] The first step is to read the point cloud coordinate file and store its three-dimensional coordinates into three arrays X, Y, and Z in a certain order;

[0063] The second step is to read the point cloud coordinate data from the origin position in the storage order. First, the origin point cloud is used as reference point 1. The point cloud with a distance less than R from the reference point is deleted until the next point cloud data that does not meet the condition appears. At this time, it is set as the new reference point 2. All data are processed in this way in sequence.

[0064] The third step is to save the coordinate data of all reference points, which is the thinned point cloud data. Since the point cloud has millimeter-level accuracy, R can be determined based on the collected point cloud density and the accuracy requirements of the model.

[0065] (3) Point cloud triangulation processing

[0066] Based on the thinned point cloud coordinate data, three adjacent point clouds are triangulated in MATLAB to form continuous triangular faces. The remaining data points are then triangulated using this method, ultimately forming the envelope of the tunnel blasting surface—the 3D model of the tunnel blasting area. This process can be implemented in MATLAB using the Stlwrite function. Alternatively, using the reverse engineering software Imagewaresurface, the point cloud data can be directly converted into an STL file.

[0067] Step S3: Perform Boolean operations on the three-dimensional model before and after blasting, and apply the simplex method to the three-dimensional model calculation to obtain overbreak and underbreak data information at various locations. The specific steps include:

[0068] Perform Boolean operations based on the obtained three-dimensional models of the blasting area before and after blasting;

[0069] The simplex method is used to obtain the centroid, surface area, volume and centroid information of the triangular elements on the outer surface of each model;

[0070] Locate the over-excavation and under-excavation points, and obtain the tunnel over-excavation and under-excavation area, over-excavation and under-excavation volume, and average over-excavation and under-excavation information.

[0071] In this embodiment, the Boolean operation of the tunnel blasting model before and after is specifically implemented as follows:

[0072] By importing the 3D models before and after blasting into CAD, assigning them different colors and adjusting their transparency, the blasting quality and over- and under-excavation status at various locations in the tunnel can be intuitively displayed. By performing Boolean operations on the models before and after blasting, model files with over- and under-excavation at various locations can be obtained. Since the model files are geometric bodies formed by the envelope of triangular units, the simplex method is used to obtain information such as the center of mass, surface area, volume, and centroid of the triangular units on the outer surface of each model. Taking volume as an example, the simplex method for solving the volume V of a three-dimensional block is as follows: each triangle on the outer surface of the geometric body can form a tetrahedron with the coordinates of the geometric body's center. To calculate the volume of a geometric body, the volume of all tetrahedrons formed by the triangles and the geometric body's center can be calculated and then summed. The result of calculating the volume using this method can be positive or negative; the actual volume is the cumulative volume of all tetrahedrons of the geometric body.

[0073]

[0074] Where N represents the total number of triangle vertices that make up the model, p i ,p i+1 ,p i+2 represents the vertex coordinates of the triangular element. The simplex method effectively locates overbreak and underbreak points and obtains information such as the tunnel overbreak area, overbreak volume, and average overbreak under the current blasting scheme. In summary, the established 3D digital model before and after blasting displays overbreak and underbreak data at various locations in the tunnel, recreating the true structural characteristics of tunnel blasting overbreak and underbreak.

[0075] Step S4: Introducing a comprehensive integrated weighting method weight model of multiple theoretical models to quantitatively analyze each blasting index and obtain the tunnel blasting quality assessment result. The specific steps include:

[0076] First, evaluation indicators are obtained, including maximum overbreak, average linear overbreak, maximum underbreak, maximum step size between two blastholes, overbreak area, measured cross-sectional area, overbreak rate, overbreak volume, and blasthole utilization rate;

[0077] Based on the multi-theoretical model, a comprehensive integrated empowerment weight model is established;

[0078] The design parameters of the blasting surface and the Boolean operation results of the three-dimensional model before and after blasting are input into the solution formula of the blasting quality score of the comprehensive integrated weighted model to obtain the evaluation results.

[0079] Specifically, the solution formula for the blasting mass fraction is:

[0080]

[0081] Among them, X i is the weight coefficient of the evaluation index, Y i is the evaluation score of the evaluation index.

[0082] The quality of tunnel blasting is typically assessed qualitatively based on subjective experience or blasting specifications. This approach fails to accurately reflect the true structural characteristics of tunnel overbreak and underbreak, nor does it provide a quantitative analysis method for evaluating tunnel blasting quality. Numerous factors influence blasting quality, and each factor has varying degrees of importance.

[0083] In this example, by comparing various evaluation models proposed by researchers, this work employed a comprehensive integrated weighting model. This model can quantitatively and comprehensively analyze the impact of various post-blasting parameters on blasting quality, effectively avoiding the use of single objective weighting methods or subjective weighting methods to evaluate blasting quality. The required evaluation indices are as follows: maximum overbreak, average linear overbreak, maximum underbreak, maximum step size between two blasts, overbreak area, measured cross-sectional area, overbreak ratio, overbreak volume, and blasthole utilization rate. Based on the design parameters of the blasting surface and the integrated results of Boolean operations on the three-dimensional model before and after blasting, this evaluation model can effectively perform a quantitative assessment of tunnel blasting quality.

[0084] The formula for calculating the blasting mass fraction is as follows:

[0085]

[0086] Among them, as shown in Table 1 below, X i is the weight coefficient of the evaluation index; Y i The evaluation score for each evaluation indicator is 100 points, with the optimal score for each evaluation indicator being 10 points, and the worst score being 10 points. This indicator is typically scored by experts and engineers. Tunnel blasting quality is evaluated at five levels: a score less than 45 points is considered extremely poor; 45 to 60 points is considered poor; 60 to 75 points is considered passing; 75 to 90 points is considered good; and a score greater than 90 points is considered excellent. In summary, based on the blasting information provided by the 3D tunnel blasting model, an evaluation model using a comprehensive integrated weighting method can comprehensively, effectively, objectively, and quantitatively assess tunnel blasting quality.

[0087] Table 1 Weight coefficients of comprehensive integrated weighting method

[0088] Evaluation indicators Comprehensive integrated weighting method coefficient Maximum overexcavation 0.151 Average linear overbreak 0.170 Maximum undercut 0.116 Maximum size of the steps between two guns 0.212 Over-excavation area 0.073 Measuring cross-sectional area 0.041 Over-excavation rate 0.065 Over-excavation volume 0.092 Blasthole utilization rate 0.080

[0089] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents, and all should be included within the scope of protection of the present invention.

Claims

1. A tunnel blasting quality assessment method based on three-dimensional point cloud information, characterized in that: The specific steps include: S1. Obtain 3D point cloud data of the tunnel lining surface and the front pre-support section before blasting, extract the tunnel centerline, and combine the position information of the tunnel centerline and the tunnel design contour line to obtain a 3D model of the blasting area before blasting; S2. Obtaining the three-dimensional point cloud data of the tunnel after blasting, and performing thinning and triangulation processing on the three-dimensional point cloud data to obtain a three-dimensional model of the blasting area after blasting. The specific steps include: Place the 3D scanner at the same position as before blasting to scan the blasting surface and obtain 3D point cloud data; Read the point cloud coordinate data in the 3D point cloud data, set the origin position and update the progressive point cloud as the reference point, delete the point cloud whose distance from the reference point is less than the preset threshold R, perform thinning processing and save; The three adjacent point clouds after thinning are triangulated to obtain a three-dimensional model of the blasting area after blasting. S3. Performing Boolean operations on the three-dimensional model before and after blasting, and applying the simplex method to the three-dimensional model calculation to obtain over-excavation and under-excavation data information at various locations. The specific steps include: Perform Boolean operations based on the obtained three-dimensional models of the blasting area before and after blasting; The simplex method is used to obtain the centroid, surface area, volume and centroid information of the triangular elements on the outer surface of each model; Locate overbreak and underbreak points, and obtain tunnel overbreak and underbreak area, overbreak and underbreak volume, and average overbreak and underbreak information; S4. Introducing a comprehensive integrated weighting model of multiple theoretical models to quantitatively analyze various blasting indicators and obtain the tunnel blasting quality assessment results; Among them, the solution formula for the blasting mass fraction is: Among them, X i is the weight coefficient of the evaluation index, Y i is the evaluation score of the evaluation index.

2. The tunnel blasting quality assessment method based on three-dimensional point cloud information according to claim 1, characterized in that: The specific steps of obtaining the three-dimensional point cloud data of the tunnel lining surface and the front pre-support section before blasting, extracting the tunnel centerline, and fitting the three-dimensional model of the blasting area before blasting by combining the position information of the tunnel centerline and the tunnel design contour line include: First, before blasting, the current tunnel section is scanned using a 3D scanner to obtain 3D point cloud data of the current tunnel lining surface and the front pre-support section; Based on the 3D point cloud data, the coordinate system of the lining surface of the current tunnel is established, and the central axis corresponding to the current tunnel lining section is obtained by linear mean fitting based on the coordinate data; Then, based on the position information of the central axis and the tunnel design contour line, cyclic footage and stretching are performed to obtain a three-dimensional model of the blasting area before blasting.

3. The tunnel blasting quality assessment method based on three-dimensional point cloud information according to claim 1, characterized in that: The specific steps of introducing the weight model of the comprehensive integrated weighting method of the multi-theoretical model to quantitatively analyze each blasting index and obtain the tunnel blasting quality assessment result include: First, evaluation indicators are obtained, including maximum overbreak, average linear overbreak, maximum underbreak, maximum step size between two blastholes, overbreak area, measured cross-sectional area, overbreak rate, overbreak volume, and blasthole utilization rate; Based on the multi-theoretical model, a comprehensive integrated empowerment weight model is established; The design parameters of the blasting surface and the Boolean operation results of the three-dimensional model before and after blasting are input into the solution formula of the blasting quality score of the comprehensive integrated weighted model to obtain the evaluation results.

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