A 3D geological layer pinch-out processing method based on DSI

Abstract

The present invention provides a method for processing the pinch-out of three-dimensional strata based on DSI, comprising the following steps: establishing a topographic surface by using DSI interpolation technology through the measured data of the research area; selecting the topographic surface as the base surface; generating the stratum surface closest to the base surface; cutting the base surface according to the stratum surface to generate a new base surface; selecting the new base surface generated in step S4, and repeatedly executing steps S3-S5 until all stratum surfaces are generated. The present invention can not only eliminate the errors in establishing the curved surface, but also truly reflect the logical relationship between the strata, providing supporting data for the establishment of the three-dimensional geological model.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering survey, and particularly relates to a three-dimensional ground surface pinch-out processing method based on DSI. Background Technique

[0002] With the increasingly mature development of computer technology, the digitization of geotechnical engineering survey is an inevitable result, which can provide a more reasonable analysis tool, a brand-new display window and stage for engineering survey. As one of the important survey results of geotechnical engineering, the three-dimensional geological model makes the survey results more intuitive, the design means more advanced, the collaborative operation more convenient, the project management more efficient, and the result transfer more standardized.

[0003] The objects studied in power geotechnical engineering survey are mainly soil layers. Soil layers such as nearly horizontal strata, pinch-out layers and lenticular bodies are relatively common, and the thickness between strata is usually relatively thin, which often causes some problems when using limited borehole data for three-dimensional geological modeling. When establishing a three-dimensional geological model, alluvial-proluvial and marine sedimentary soil layers such as nearly horizontal strata, pinch-out layers and lenticular bodies are relatively common, and the thickness between strata is usually relatively thin. Especially in the process of dealing with strata with poor mechanical properties, which plays an important role in engineering. During the process of three-dimensional geological modeling, it must be depicted. However, due to the thin strata and the very close elevation of the top and bottom of the strata, some problems often occur during three-dimensional geological modeling. It often requires the modeler to make repeated local adjustments and modifications, and it is often more difficult to construct cross-layer pinch-out layers. Sometimes, due to the problem of discontinuous strata, the error brought by interpolation itself when constructing a surface is greater than the change of the strata, which will cause the established model to be distorted. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the above background technique, and provide a three-dimensional ground surface pinch-out processing method based on DSI, which can not only eliminate the error of establishing a surface, but also truly reflect the logical relationship between strata, and provide supporting data for the establishment of a three-dimensional geological model.

[0005] The technical solution adopted by the present invention is: a three-dimensional ground surface pinch-out processing method based on DSI, including the following steps:

[0006] S1, through the obtained measurement data of the research area, use DSI interpolation technology to establish a terrain surface;

[0007] S2, select the terrain surface as the base surface;

[0008] S3. Construct real constraint conditions and virtual constraint conditions based on the base surface, the stratigraphic demarcation point of the first stratum below the base surface, and the borehole data in the study area. After the base surface is generated, the stratigraphic demarcation point of the stratum below the base surface can be obtained accordingly.

[0009] S4. Calculate and generate the stratum surface closest to the base surface that is continuously distributed throughout the study area as the stratum surface at a certain stratum depth. There are multiple strata below the base surface, and the stratum surface closest to the base surface is the stratum surface of the first stratum below the base surface.

[0010] S5. Generate a new base surface based on the stratum surface, real constraint conditions, and virtual constraint conditions calculated in step S4.

[0011] S6. Select the new base surface generated in step S5, and loop through steps S3 - S5 until stratum surfaces corresponding to all the exposed stratum depths in the borehole data of the study area are generated.

[0012] In the above technical solution, in step S3, select the stratum surface closest to the base surface as the research object, and determine whether the stratigraphic demarcation point of the first stratum below the base surface appears in each borehole of the research object. If the stratigraphic demarcation point appears in a certain borehole, take the stratigraphic demarcation point that appears in this borehole as the constraint point and use it as the real constraint condition. If the stratigraphic demarcation point does not appear in a certain borehole, set the constraint point above the base surface as the virtual constraint condition. The real constraint condition and the virtual constraint condition together serve as the constraint condition. Through the construction of the virtual constraint condition, the present invention effectively extends the constraint condition to the entire study area.

[0013] In the above technical solution, step S4 specifically includes the following steps:

[0014] Generate an initial surface, repeatedly refine the grid and perform DSI interpolation operations according to the constraint conditions until an initial stratum surface is generated. Then convert the real constraint condition into an exact constraint, and perform DSI interpolation operations on the above - mentioned stratum surface to generate a stratum surface that is continuously distributed throughout the study area. There is no clear standard for the generation of the initial stratum surface. Engineers consider that the smoothness meets the requirements through inspection and then proceed to the next step. This step extends the locally distributed stratum surface to the entire area, establishes a continuously distributed stratum surface, and greatly simplifies the processing difficulty of discontinuous stratum surfaces.

[0015] In the above technical solution, step S5 specifically includes the following steps:

[0016] S5.1, Determine the relationship between the formation plane and the borehole: If the formation plane is missing in some boreholes, the plane constructed by the real constraint condition is below the base plane, the plane constructed by the virtual constraint condition is above the base plane, and the planes constructed by the real and virtual constraint conditions intersect with the base plane, then execute steps S5.2 and S5.3; If the formation plane exists in all boreholes, there is no virtual constraint condition, the plane constructed by the real constraint condition is below the base plane, and this formation plane is used as the new base plane, directly execute step S3;

[0017] S5.2, Trim the formation plane with the base plane: Delete the part above the base plane on this formation plane, and the remaining part is used as the trimmed formation plane. The trimmed formation plane shows a gradual pinch-out to the base plane;

[0018] S5.3, Trim the base plane with the trimmed formation plane: Delete the part above the trimmed formation plane on the base plane, and the remaining part is used as the trimmed base plane. Combine the trimmed base plane and the trimmed formation plane to form a new base plane.

[0019] This step calculates the research formation below the new base plane formed by recombination, improving the control accuracy of establishing subsequent formation planes.

[0020] In the above technical solution, in step S3, if the formation boundary point does not appear in a certain borehole but appears in the adjacent borehole, the constraint point is set above the base plane, and the calculation formula for the distance H between the constraint point and the base plane is as follows:

[0021] H = (1 - a / A) * B;

[0022] Where, a is the thickness of this formation in the adjacent borehole, A is the total formation thickness of the adjacent borehole, and B is the total formation thickness of this borehole;

[0023] If the formation boundary point does not appear in a certain borehole and also does not appear in the adjacent borehole, the constraint point is set at any distance above the base plane.

[0024] The processing method adopted in step S3 can reflect the influence of the thickness of this formation in the borehole on the pinch-out point. The greater the thickness of the formation, or the greater the proportion it occupies, the farther the pinch-out point is from this borehole.

[0025] In the above technical solution, it also includes step S7, using the layer-by-layer local encryption method to encrypt the grid at the pinch-out boundary. Through local encryption, the pinch-out transition can be made more natural and smooth.

[0026] In the above technical solution, if multiple formation boundary points appear in the same borehole, select one of the boundary points as the real constraint condition for constructing the formation plane this time.

[0027] The present invention provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described in the above technical solution are implemented.

[0028] The beneficial effects of the present invention are as follows: According to the characteristics of the soil layers in engineering surveys, a suitable base surface is constructed, and the ground surface layer in the borehole is used as a real constraint condition. Then, by constructing virtual constraint conditions, the locally distributed ground surface layer is extended to a continuously distributed ground surface layer throughout the study area. Compared with the prior art, the present invention is more suitable for the DSI interpolation technology for describing the interface of geological bodies. By establishing a continuous ground surface layer distributed throughout the region, the discontinuous problem is transformed into a continuous problem, greatly reducing the processing difficulty of the pinching out of the ground surface layer. Through the expansion, clipping, deletion, and recombination of the surface, the pinched-out ground surface layer is naturally formed, reducing the difficulty of establishing the three-dimensional ground surface layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic flow chart of the present invention;

[0030] Figure 2 is a schematic diagram of the constraint transfer of fuzzy control constraint points;

[0031] Figure 3 is a schematic diagram of the base surface (reference surface used when constructing the ground surface layer);

[0032] Figure 4 is a schematic diagram of boreholes with outcropping strata (a total of 7);

[0033] Figure 5 is a schematic diagram of boreholes without outcropping of this stratum (a total of 25);

[0034] Figure 6 is a diagram of real constraint points and virtual constraint points (a total of 32);

[0035] Figure 7 is a distribution diagram of continuous constraint conditions in the study area (a total of 32);

[0036] Figure 8 is a schematic diagram of the initial ground surface layer;

[0037] Figure 9 is a schematic diagram of the constraint conditions of the ground surface layer (at this time, it is a fuzzy constraint)

[0038] Figure 10 is a schematic diagram of the generated ground surface layer;

[0039] Figure 11 is a schematic diagram of the clipped ground surface layer;

[0040] Figure 12Schematic diagram of the ground layer after removing the auxiliary part above the base surface;

[0041] Figure 13 Schematic diagram of the finally generated ground layer;

[0042] Figure 14 Schematic diagram of the base surface retained after trimming the ground layer by the layer surface;

[0043] Figure 15 Schematic diagram of the new base surface

[0044] Figure 16 Calculation diagram of the distance of the constraint point set above the base surface Detailed implementation mode

[0045] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which is convenient for clearly understanding the present invention, but they do not constitute a limitation to the present invention.

[0046] The purpose of the present invention is to provide a method for dealing with the stratigraphic pinch-out in the process of establishing a three-dimensional geological model. By adopting the Discrete Smooth Interpolation (DSI) theory and using the corresponding grid technology, with the base surface (generally taking the nearest surface to the proposed formation as the base surface) as a reference, a ground layer adjacent to the base surface is established, which can not only eliminate the errors in establishing the curved surface but also truly reflect the logical relationship between the strata, providing supporting data for the establishment of the three-dimensional geological model. This method mainly includes discrete smooth interpolation, corresponding grid technology, and the construction of virtual geological interfaces, and its main contents are as follows:

[0047] Discrete smooth interpolation is an interpolation theory based on discrete mathematics. The stratigraphic interface is regarded as a discretized discontinuous interface, and measurement points, geological points, and borehole data revealed by geological exploration, etc. are used as constraint conditions. A three-dimensional stratum is established by solving through an iterative algorithm. In fact, it is to obtain the optimized ground layer that meets the constraint conditions by solving the optimal solution of the objective function - the global roughness function under these constraint conditions. The advantage of DSI technology is that it can fit and construct complex geological models according to various constraint conditions and their combinations, such as multi-Z value (fold, lens body), non-continuous (fault, overburden) geological body models, and can be locally modified without having to re-model due to changes in geological exploration data. Its basic principle is as follows:

[0048] Define the three-dimensional geological discrete model M n (Ω, N, C), where Ω is all the nodes that make up the model, N is the set of neighboring points of each node, is the n-order vector attribute function of each node, and C is the constraint of each node.

[0049] Define the function

[0050]

[0051] where is the global roughness function, is the global constraint violation degree function, is the constraint factor, is the balance factor.

[0052] DSI solution actually means to minimize the function i.e., Therefore, we get

[0053]

[0054] where:

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061] where is the constraint coefficient.

[0062] According to the actual constraint situation, the constraint coefficients under different conditions can be obtained, and then the optimal value can be iteratively solved through the above formula, and finally a geometric model that meets the constraint conditions can be fitted. The constraints of DSI can be divided into soft constraints and hard constraints. Soft constraints usually refer to the constraints (approximate equal) with relaxed conditions and fitted by the global least squares sum; hard constraints are the constraints that must be completely fitted by equations or inequalities. Since the DSI method considers the relationship between nodes and neighboring nodes, it can fit very complex models according to the constraint conditions of the actual situation, so it is especially suitable for modeling complex geological layers.

[0063] For a pinched-out formation, the thickness of the formation gradually thins from a certain thickness and finally approaches zero, and the formation disappears, forming a pinched-out formation. In this way, since the thickness of the formation will be very thin, some problems often occur when using less borehole data or profile data for 3D geological modeling, such as unreasonable penetration of the upper and lower layers, and the modeler often needs to make repeated local adjustments and modifications. It is also often more difficult to construct a pinched-out layer that crosses layers. Considering the modeling characteristics of these soil layers, the pinched-out problem of the 3D ground surface is processed by analyzing the characteristics of the pinched-out of the soil formation. Generally, during the modeling process, according to the sedimentary rhythm, and in the modeling order of the large layers first and then the sub-layers in the borehole, the formation is inserted layer by layer.

[0064] As Figure 1 shown, the present invention provides a method for processing the pinched-out of the 3D ground surface based on DSI, which specifically includes the following steps:

[0065] The first step: Through the obtained measurement data, apply the DSI interpolation technology to establish a topographic surface;

[0066] In this embodiment, specifically select the measurement data covering the research area, define a range according to the planar range of the research, combine the survey data to establish an intermediate surface or a median surface as the initial surface, appropriately encrypt the initial surface, and then define the fuzzy control point constraint:

[0067] Assume that T(x(α0), x(α1), x(α2)) is a triangular mesh surface, and the fuzzy control point constraint is: IP attracts a point P on T such that P moves to or approaches IP according to the weight, as Figure 2 shown.

[0068] According to mathematical derivation, the DSI functions and are respectively:

[0069]

[0070]

[0071] where {μ 0 (p), μ 1 (p), μ 2 (p)} are the barycentric coordinates of point P in triangle T.

[0072] This constraint is used in 3D geological modeling software to fit a given point (such as a formation marker or geological point revealed by exploration) with a surface, or to fit geophysical data points with a surface according to the weight.

[0073] This constraint is used in 3D geological modeling software to fit a given point (such as a formation marker or geological point revealed by exploration) with a surface, or to fit geophysical data points with a surface according to the weight.

[0074] Next, perform discrete smooth interpolation on the defined terrain surface. This operation can be repeated multiple times until the generated surface is smooth enough. Repeat the discrete encryption on the plane and then perform smooth interpolation. Finally, convert the fuzzy control constraint points into precise constraint points and perform discrete smooth interpolation until a qualified terrain surface is generated.

[0075] Step 2: Select the terrain surface as the base surface. The base surface and its underlying strata (including pinch-out layers and lenses) all adopt the base surface grid. Using the terrain surface as the reference base surface, the data of the formation boundary points of the boreholes are used as constraints (including real constraint conditions and virtual constraint conditions). There are multiple strata below the base surface. As the base surface is generated, formation boundary points will be correspondingly generated below the base surface.

[0076] Step 3: Generate continuous strata in the entire study area based on the base surface.

[0077] Select the stratum closest to the base surface (i.e., the stratum corresponding to the first stratum below the base surface) as the research object, and determine whether the formation boundary point of the first stratum below the base surface appears in each borehole of the research object. If the formation boundary point appears in a certain borehole, then take the formation boundary point that appears in this borehole as a constraint point and as a real constraint condition; if the formation boundary point does not appear in a certain borehole, then set the constraint point above the base surface as a virtual constraint condition; the real constraint condition and the virtual constraint condition together serve as the constraint conditions. Combine the real constraint condition and the virtual constraint condition, then this stratum is continuously distributed in the entire study area, and then use the DSI interpolation technique to generate continuous strata in the entire study area.

[0078] Among them, the specific distance is determined according to the ratio of the thickness of this stratum in the adjacent boreholes to the total thickness of the strata: If the formation boundary point does not appear in a certain borehole but appears in the adjacent borehole, then set the constraint point above the base surface, and the calculation formula for the distance H between the constraint point and the base surface is as follows:

[0079] H = (1 - a / A) * B;

[0080] Among them, a is the thickness of this stratum in the adjacent boreholes, A is the total thickness of the strata in the adjacent boreholes, and B is the total thickness of the strata in this borehole; as Figure 16 shown.

[0081] If the formation boundary point does not appear in a certain borehole and there is no formation boundary point in the adjacent borehole either, set the constraint point at any distance above the base surface.

[0082] The specific implementation process is as follows:

[0083] (1) Using the terrain surface as the base surface, as Figure 3 shown.

[0084] (2) Select the stratum immediately adjacent to the foundation surface as the research object, and use the borehole stratum demarcation point data as constraints; among the 32 boreholes in the study area, there are stratum demarcation points in 7 boreholes, that is, there is this stratum in 7 boreholes. The stratum demarcation points of the 7 boreholes are set as constraint points, which are called real constraint conditions, as shown in the round frames shown in Figure 4 The other 25 boreholes do not have demarcation points, that is, there is no such stratum.

[0085] (3) If there is no stratum demarcation point of this layer in the borehole and the stratum disappears here, then set the constraint point above the foundation surface, which is called the virtual constraint condition, a total of 25, as shown in Figure 5 As shown, the 25 round frames in the figure represent stratum demarcation points, all of which are set above the foundation surface.

[0086] (4) Combine the real constraint conditions and the virtual constraint conditions, then the stratum is continuously distributed throughout the study area, as shown in Figure 6 、 7 As shown, the dots in the figure represent constraint points. Figure 6 Among them, the ones located on the foundation surface are virtual constraint points, and the ones located below the foundation surface are real constraint points. Figure 7 The larger dots in the figure are real constraint points, and the smaller dots are virtual constraint points.

[0087] (5) Adopt the DSI interpolation technology to generate a stratum that is continuously distributed throughout the study area. The specific steps are as follows:

[0088] A. Generate an initial surface, such as the median surface, as shown in Figure 8 Shown;

[0089] B. Define the constraint conditions for this stratum, and define the determined virtual constraint conditions and real constraint conditions without difference as constraint conditions, as shown in Figure 9 Shown;

[0090] C. Repeatedly refine the grid and use the DSI interpolation operation until a suitable stratum is generated. The suitable criterion is that the engineer believes that the cover surface is relatively smooth by observation, and no clear measurement index is required. Then convert the real constraint conditions into precise constraints, and then perform the DSI interpolation operation to generate the final stratum that is continuously distributed throughout the study area, as shown in Figure 10 Shown. Figure 10 In the figure, the darker part with the network is the generated final stratum, and the lighter part in the middle is the base surface (ground surface). It can be intuitively seen from Figure 10 that at this time, the stratum is distributed throughout the study area. Only the stratum under the real constraint conditions is located below the foundation surface, and this part is the stratum that the present invention wants to establish; the stratum under other virtual constraint conditions is located above the foundation surface and can play an auxiliary role in establishing the stratum.

[0091] If this formation surface is missing in some boreholes, these boreholes constitute virtual constraint conditions. The surfaces constructed by the real constraint conditions are located below the base surface, and the surfaces constructed by the virtual constraint conditions are located above the base surface. The surface between the real constraint conditions and the virtual constraint conditions naturally intersects with the base surface, and continue with the subsequent step D in the third step; if this formation surface exists in all boreholes, there are no virtual constraint conditions, and the constructed formation surfaces are all located below the base surface. Directly generate a formation surface that is continuously distributed in the entire study area (at this time, the formation surface is continuously distributed in the entire study area), skip the subsequent step D in the third step and the fourth step, and directly execute the fifth step. This formation surface can be used as a new base surface, and subsequent calculations can be directly performed using this new base surface.

[0092] D. Use the base surface and the formation surface to perform a cutting operation to form the pinch-out of the formation. The specific method is: cut this formation surface with the base surface, see Figure 11 ; and delete the part above the base surface, so that this formation surface appears to gradually pinch out onto the base surface, see Figure 12 ; obtain the final formation surface, see Figure 13 . Cut this formation surface with the base surface and delete the part of the "virtual geological interface" formed by the virtual constraint conditions above the base surface, forming a formation surface adjacent to the base surface and naturally forming the pinch-out of this formation surface.

[0093] Fourth step: Generate a new base surface. Cut the base surface with this formation surface and delete the part above this formation surface, see Figure 14 , add the cut base surface and the finally generated formation surface to generate a new base surface, see Figure 15 .

[0094] Fifth step: Use the new base surface generated in the third step or the fourth step, repeat the third step and the fourth step, from top to bottom, until formation surfaces corresponding to the depths of all the strata exposed by the borehole data in the study area are generated. Then, use the layer-by-layer local refinement method to refine the grid at the pinch-out boundary for subsequent construction of a three-dimensional geological model.

[0095] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. A three-dimensional strata pinch-out processing method based on DSI, characterized in that: It includes the following steps: S1. Based on the measurement data of the research area obtained, use DSI interpolation technology to establish a terrain surface; S2. Select the terrain surface as the base surface; S3. According to the base surface, the stratigraphic demarcation points of the first stratum below the base surface, and the borehole data of the research area, construct real constraint conditions and virtual constraint conditions; S4. According to the real constraint conditions and virtual constraint conditions, calculate and generate a strata surface closest to the base surface that is continuously distributed throughout the research area as the strata surface at a certain stratum depth; S5. According to the strata surface, real constraint conditions and virtual constraint conditions calculated in step S4, generate a new base surface; S6. Select the new base surface generated in step S5, and loop to execute steps S3 - S5 until strata surfaces corresponding to all exposed stratum depths in the borehole data of the research area are generated; Step S5 specifically includes the following steps: S5.

1. Determine the relationship between the strata surface and the borehole: If the strata surface is missing in some boreholes, the surface constructed by the real constraint conditions is below the base surface, the surface constructed by the virtual constraint conditions is above the base surface, and the surfaces constructed by the real constraint conditions and virtual constraint conditions intersect with the base surface, then execute steps S5.2 and S5.3; If the strata surface exists in all boreholes, there are no virtual constraint conditions, the surface constructed by the real constraint conditions is below the base surface, and use this strata surface as the new base surface and directly execute step S3; S5.

2. Clip the strata surface with the base surface: Delete the part above the base surface on this strata surface, and the remaining part is used as the clipped strata surface. The clipped strata surface shows a gradual pinch-out to the base surface; S5.

3. Clip the base surface with the clipped strata surface: Delete the part above the clipped strata surface on the base surface, and the remaining part is used as the clipped base surface. Combine the clipped base surface and the clipped strata surface to form a new base surface.

2. A three-dimensional strata pinch-out processing method based on DSI according to claim 1, characterized in that: In step S3, select the strata surface closest to the base surface as the research object, and determine whether the stratigraphic demarcation points of the first stratum below the base surface appear in each borehole of the research object; If the stratigraphic demarcation point appears in a certain borehole, then take the stratigraphic demarcation point that appears in this borehole as the constraint point and use it as the real constraint condition; If the stratigraphic demarcation point does not appear in a certain borehole, then set the constraint point above the base surface as the virtual constraint condition; The real constraint conditions and virtual constraint conditions together serve as the constraint conditions.

3. A three-dimensional strata pinch-out processing method based on DSI according to claim 2, characterized in that: Step S4 specifically includes the following steps: Generate an initial surface, repeatedly refine the grid and use DSI interpolation operation according to the constraint conditions until an initial strata surface is generated; Then convert the real constraint conditions into precise constraints, and then perform DSI interpolation operation on the above-mentioned strata surface to generate a strata surface that is continuously distributed throughout the research area.

4. A three-dimensional strata pinch-out processing method based on DSI according to claim 1, characterized in that: In step S3, if a formation boundary point does not appear in a certain borehole but appears in an adjacent borehole, the constraint point is set above the foundation surface, and the calculation formula for the distance H between the constraint point and the foundation surface is as follows: H = (1 - a / A) * B; where a is the thickness of this formation layer in the adjacent borehole, A is the total formation thickness of the adjacent borehole, and B is the total formation thickness of this borehole; If a formation boundary point does not appear in a certain borehole and there is no formation boundary point in the adjacent borehole either, the constraint point is set at any distance above the foundation surface.

5. A three-dimensional formation layer pinch-out processing method based on DSI according to claim 4, characterized in that: It further includes step S7, using the layer-by-layer local encryption method to encrypt the grid at the pinch-out boundary.

6. A three-dimensional formation layer pinch-out processing method based on DSI according to claim 3, characterized in that: If multiple formation boundary points appear in the same borehole for this formation, one of the boundary points is selected as the actual constraint condition for constructing the formation layer this time.

7. A computer-readable storage medium, characterized in that: A computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the steps of the method described in any one of claims 1-6 are implemented.

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