A method for identifying and locating three-dimensional karst boundaries

Abstract

The present invention discloses a method for identifying and locating three-dimensional karst boundaries. Due to the complexity of karst development conditions and the limitations of human cognitive level, the three-dimensional karst identification methods and technologies are still imperfect. Existing three-dimensional karst boundary identification methods are mostly based on geophysical data. On the basis of comprehensive analysis of multiple geophysical information, the boundaries of underground karst are predicted and evaluated. The above methods are limited by geophysical methods and interpretation theories, and are greatly interfered by human factors, with a large workload and low efficiency. The present invention proposes a method for automatically identifying three-dimensional karst boundaries based on geological drilling information. According to objective drilling information and combined with spatial logic algorithms, the three-dimensional karst boundaries can be automatically identified, and the interference of human factors can be completely eliminated. The efficiency is high and the needs of large-scale applications can be met.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration, and in particular to a method for identifying and locating a three-dimensional karst boundary. Background Art

[0002] Three-dimensional spatial modeling of karst is a technology that uses computer technology to combine the spatial information of karst with visualization tools in a three-dimensional environment for karst analysis.

[0003] Due to the complexity of karst development conditions and the limitations of human cognition, the three-dimensional identification methods and technologies of karst are still imperfect. The existing three-dimensional karst boundary identification methods are mostly based on geophysical data. Based on the comprehensive analysis of multiple geophysical information, the boundaries of underground karst are predicted and evaluated. The above methods are limited by geophysical methods and interpretation theories, and are greatly interfered by human factors, with large workload and low efficiency.

[0004] Through public search, the following related patents were found:

[0005] CN111007578A discloses a comprehensive detection method and system for embankment karst and goaf, which uses seismic wave method and controlled source method to survey large-scale and deep embankment karst and goaf, and conducts long-distance rough detection; uses ground penetrating radar method, transient electromagnetic method, cross-hole high-density electrical method and surface high-density electrical method to conduct close-range fine detection; uses the detection results of the above detection methods as prior information to perform constrained inversion; then verifies the inversion results through drilling; expands the borehole diameter, and inserts a three-dimensional laser scanner to scan the karst and goaf; the invention realizes the comprehensive detection of embankment karst and goaf by multiple geophysical methods, adds prior constrained inversion, reduces the multi-solution of inversion, improves the inversion accuracy, and scans the karst and goaf through a three-dimensional laser borehole scanner, thereby realizing the precise positioning of embankment karst and goaf, and the detection of the size and filling of the goaf.

[0006] CN111161415A discloses a three-dimensional spatial simulation method for groundwater karst development channels in karst areas, which sequentially includes the following steps: 1) conducting geological surveys on the karst area to obtain the geological, foundation and groundwater exploration parameters of the karst area, and establishing a geological structure model of the karst development channel based on the exploration parameters to obtain a geological structure map; 2) using a digital elevation model DEM to generate an artificial light source image with a positive stereoscopic visual effect, and through spectral fidelity fusion processing, the artificial light source image and the geological map are fused to form a visual stereoscopic geological map. This method quickly and efficiently simulates the three-dimensional space of the groundwater karst development channel in the karst area, builds a model, and presents it in a direct manner.

[0007] Upon analysis, it is found that the above two patents have significant differences in the steps of identifying and locating the boundaries of karst zones composed of a single karst and multiple single karsts, and the results of identifying and locating their boundaries are also different, so it does not affect the novelty of the present application. Summary of the invention

[0008] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for identifying and locating three-dimensional karst boundaries. The method automatically identifies the three-dimensional karst boundaries based on geological drilling information. The method can automatically identify the three-dimensional karst boundaries based on objective drilling information and combined with spatial logic algorithms, completely eliminating interference from human factors, with high efficiency, and meeting the needs of large-scale exploration applications.

[0009] A method for identifying and locating a three-dimensional karst boundary comprises the following steps:

[0010] S1. Basic data preparation: Drilling data collation, mainly including mesh drilling information in the karst area, including the top and bottom elevations of the karst layer, etc.

[0011] S2. Karst space information labeling: define the karst space and ordinary stratum stratification nodes, find the location of the karst stratum in each geological borehole, and find the boundary points between its top and bottom and ordinary stratum; organize the above boundary points according to the naming principle with borehole number, karst section number and position number;

[0012] S3, karst top and bottom boundary identification: starting from any borehole, with the karst boundary point of the borehole as the center, a cylinder of a specific size is generated, and other karst boundary points contained in the area and with the same position number as the central karst boundary point are identified as belonging to the top or bottom of the same karst boundary surface;

[0013] S4. Automatic generation of karst three-dimensional boundary: After completing the point set search of the karst boundary surface, the top and bottom surfaces of the karst area are generated using the triangular topology principle. At this time, the horizontal projections of the top and bottom surfaces of the karst boundary surface coincide with each other. Assume that this projection plane is M, which is located between the top and bottom surfaces. The top and bottom surfaces of the karst area are stretched vertically toward the M surface respectively, and finally a closed space is synthesized, that is, the karst three-dimensional space is generated.

[0014] S5. Identification of regional karst zone boundaries: According to steps S1 to S4, the three-dimensional boundaries of a single karst space can be obtained. Multiple karst spaces are combined to form a karst zone. The method for determining the three-dimensional space boundary of the karst zone is as follows:

[0015] S5.1. According to step S4, a projection plane M in each independent karst space can be obtained. Assuming that there are n karst spaces in total, there are n projection planes including M1, M2, ..., Mn-1, Mn. Let the centroid of each M plane be the spatial point P1, P2, ..., Pn-1, Pn. Connect all the P points in pairs to form several spatial straight lines D. Let the farthest distance from each P point to the edge of its own karst space be K. If a certain D is less than or equal to 1.5 times the sum of the K values ​​of the two connected karst spaces, then the two karst spaces belong to the same karst zone. And so on, until all the karst spaces belonging to the same karst zone are found.

[0016] S5.2. Using the rectangular coordinate system of the spatial plane as the standard, find the maximum and minimum values ​​of all karst spaces in the above-mentioned karst zone in the three-dimensional coordinate system, and use these extreme values ​​as the boundaries to form a cubic karst zone boundary, and then finally determine the boundary range of the karst zone.

[0017] Moreover, during the mesh drilling process in the karst area in step S1, the average drilling spacing is 10-12 m.

[0018] Moreover, step S3 also includes the following sub-steps:

[0019] S3.1. Each karst boundary interface found in step S3 continues to generate a cylinder of a specific size with itself as the center and searches outward until no karst boundary point meeting the above requirements can be found;

[0020] S3.2. Continue the above process using the undetermined karst boundary points in turn until the karst interfaces to which all karst boundary points belong are found; and then complete the identification of the top and bottom surfaces of all karst cavities.

[0021] The advantages and technical effects of the present invention are:

[0022] The present invention provides a three-dimensional karst boundary identification and positioning method, and aims at the three-dimensional karst boundary identification problem. It proposes a method for automatically identifying the three-dimensional karst boundary according to geological drilling information. The method can automatically identify single three-dimensional karst and the boundary of the three-dimensional karst zone according to objective drilling information and combined with spatial logic algorithm, and completely eliminates interference from human factors. The method is highly efficient and meets the application requirements of large-scale karst assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1a , 1b Schematic diagram of the cylindrical region in step S3 of the present invention (1a is a top view, 1b is a three-dimensional schematic diagram of a single cylinder);

[0024] Figure 2a , 2bSchematic diagram of karst zone identification in step S5 of the present invention, (2a is a planar distribution diagram of karst space, 2b is a three-dimensional schematic diagram of karst space integration into karst zone);

[0025] Figure 3 It is a schematic diagram of the implementation process of the present invention;

[0026] In the figure: L1-L7: are the lines connecting the center of a borehole and the centers of other boreholes in the plane direction; H, r: are the height and radius of the cylinder used to search for the karst boundary point; S1, S2: are the thickness of the strata immediately above and below the karst section; h: is the thickness of the karst section. DETAILED DESCRIPTION

[0027] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings. It should be noted that the embodiments are illustrative, not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0028] A three-dimensional karst boundary identification method, as shown in FIG1 , includes the following steps:

[0029] S1. Basic data preparation

[0030] The compilation of drilling data mainly includes the mesh drilling information in the karst area (average drilling spacing 10-12m), and the information content includes the elevation of the top and bottom of the karst layer.

[0031] S2. Karst spatial information labeling

[0032] Define the karst space and ordinary stratum stratification nodes, find the location of the karst stratum in each geological borehole, and find the boundary points between its top and bottom and ordinary strata. Arrange the above boundary points according to the principle of borehole number + karst section number + location.

[0033] (1) Drilling number: the serial number of the drilling hole, used to express the uniqueness of the drilling hole.

[0034] (2) Karst section number: It is used to express the spatial position of the section to which the karst boundary point belongs on the borehole. For example, three sections of karst are drilled out of a borehole. In the order from the surface downward, the corresponding karst sections can be numbered 1, 2, and 3 respectively.

[0035] (3) Position number: After determining the borehole and karst section where the karst boundary point is located, the position number is used to finally determine its spatial position. 1 represents the karst top point, and 2 represents the karst bottom point. For example, the top point in the second karst section of a borehole Z1 can be defined as Z1-2-1.

[0036] S3. Karst top and bottom boundary identification

[0037] Starting from a certain borehole, a cylinder of a specific size is generated with the karst dividing point of the borehole as the center. Other karst dividing points contained in the area and whose position numbers are consistent with the central karst dividing point are identified as belonging to the same karst boundary surface (top or bottom surface).

[0038] The above-searched karst boundary surfaces each continue to generate a disk of a specific size with themselves as the center and search outward until no karst boundary points that meet the above requirements can be found.

[0039] Subsequently, the above process is continued using the undetermined karst boundary points in turn until the karst interfaces to which all karst boundary points belong are found, thereby completing the identification of the top and bottom surfaces of all karst cavities.

[0040] The dimensions of the cylindrical area are determined as follows:

[0041] (1) With a certain karst boundary point as the center, draw a circle with a certain radius to obtain a planar circular area in space. The radius is determined by drawing straight lines from the center of the circle to the center points of the remaining boreholes. Assume that a total of n straight lines can be drawn (n ≥ 2), that is, there are a total of n+1 boreholes. The lengths of the n straight lines are L1, L2, ..., Ln-1, Ln. The median La is taken as the radius.

[0042] (2) Taking the above-mentioned plane circle as a reference, extend vertically upward to a certain height, the value is H1=(h+s1) / 2, extend vertically downward to a certain height, the value is H2=(h+s2) / 2, H=H1+H2.

[0043] Among them, h represents the thickness of the karst space belonging to this karst boundary point on the borehole; s1 represents the thickness of the borehole stratum located above the karst section; s2 represents the thickness of the borehole stratum located below the karst section, and H represents the height of the cylinder.

[0044] S4. Automatic generation of karst 3D boundaries

[0045] After completing the point set search of the karst boundary surface, the top and bottom surfaces of the karst area are generated using the principle of triangular topology. At this time, the horizontal projections of the top and bottom surfaces coincide. Assume that this projection is a spatial plane M, located between the top and bottom surfaces of the karst. The top and bottom planes of the karst area are stretched vertically toward the M surface, and finally a closed space is synthesized, that is, the karst three-dimensional space is generated.

[0046] S5. Identification of regional karst zone boundaries

[0047] According to the steps S1-S4, the three-dimensional boundary of a single karst space can be obtained. In the karst development area, there is also such a phenomenon that there are a large number of small karst cavities in a spatial area, and these cavities are gathered together to form a karst belt.

[0048] The method for determining the three-dimensional spatial boundary of the karst zone is as follows.

[0049] (1) According to step S4, a plane M can be obtained in each independent karst space. Assuming that there are n karst spaces in total, there are n M planes (M1, M2, ... Mn-1, Mn). Let the centroid of each M plane be a spatial point P (P1, P2, ... Pn-1, Pn). Connect all P points in pairs to form several spatial lines D (assuming that the spatial line between karst spaces a and b is named Da-b). Let the farthest distance from each P point to the edge of its own karst space be K (K1, K2, ... Kn-1, Kn), and the value of K is equivalent to the maximum radius from the P point to the edge of its own karst space.

[0050] Assume that we first determine the two karst spaces a and b. If Da-b≤1.5(Ka+Kb), the two karst spaces a and b belong to the same karst zone. Then we continue to determine the relationship between the karst spaces b and c, and so on, until all the karst spaces belonging to the same karst zone are found.

[0051] (2) Using the rectangular coordinate system of the spatial plane as the standard, find the maximum and minimum values ​​of all karst spaces in the above-mentioned karst zone in the three-dimensional coordinate system, and use these extreme values ​​as the boundaries to form a cubic karst zone boundary, thereby ultimately determining the scope of the karst zone.

[0052] In addition, the spatial logic algorithm combined with the present invention adopts mature technical means in the prior art.

[0053] Finally, all the parts not described in the present invention adopt mature products and mature technical means in the prior art.

[0054] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for identifying and locating a three-dimensional karst boundary, characterized in that: The following steps are involved: S1. Basic data preparation: Drilling data collation, mainly including mesh drilling information in the karst area, including the top and bottom elevations of the karst layer; S2. Karst space information labeling: define the karst space and ordinary stratum stratification nodes, find the location of the karst stratum in each geological borehole, and find the boundary points between its top and bottom and ordinary stratum; organize the above boundary points according to the naming principle with borehole number, karst section number and position number; S3, karst top and bottom boundary identification: starting from any borehole, with the karst boundary point of the borehole as the center, a cylinder of a specific size is generated, and other karst boundary points contained in the area and with the same position number as the central karst boundary point are identified as belonging to the top or bottom of the same karst boundary surface; S4. Automatic generation of karst three-dimensional boundary: After completing the point set search of the karst boundary surface, the top and bottom surfaces of the karst area are generated using the triangular topology principle. At this time, the horizontal projections of the top and bottom surfaces of the karst boundary surface coincide with each other. Assume that this projection plane is M, which is located between the top and bottom surfaces. The top and bottom surfaces of the karst area are stretched vertically toward the M surface respectively, and finally a closed space is synthesized, that is, the karst three-dimensional space is generated. S5. Identification of regional karst zone boundaries: According to steps S1 to S4, the three-dimensional boundaries of a single karst space are obtained. Multiple karst spaces are combined to form a karst zone. The method for determining the three-dimensional space boundary of the karst zone is as follows: S5.

1. According to step S4, a projection plane M in each independent karst space can be obtained. Assuming that there are n karst spaces in total, there are n projection planes including M1, M2, ..., Mn-1, Mn. Let the centroid of each M plane be the spatial point P1, P2, ..., Pn-1, Pn. Connect all the P points in pairs to form several spatial straight lines D. Let the farthest distance from each P point to the edge of its own karst space be K. If a certain D is less than or equal to 1.5 times the sum of the K values ​​of the two connected karst spaces, then the two karst spaces belong to the same karst zone. And so on, until all the karst spaces belonging to the same karst zone are found. S5.

2. Using the rectangular coordinate system of the spatial plane as the standard, find the maximum and minimum values ​​of all karst spaces in the above-mentioned karst zone in the three-dimensional coordinate system, and use these extreme values ​​as the boundaries to form a cubic karst zone boundary, and then finally determine the boundary range of the karst zone.

2. A three-dimensional karst boundary identification and positioning method according to claim 1, characterized in that: During the mesh drilling process in the karst area in step S1, the average drilling spacing is 10-12 m.

3. A three-dimensional karst boundary identification and positioning method according to claim 1, characterized in that: The step S3 also includes the following sub-steps: S3.

1. Each karst boundary interface found in step S3 continues to generate a cylinder of a specific size with itself as the center and searches outward until no karst boundary point meeting the above requirements can be found; S3.

2. Continue the above process using the undetermined karst boundary points in turn until the karst interfaces to which all karst boundary points belong are found; and then complete the identification of the top and bottom surfaces of all karst cavities.

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