Geological structure elastic wave reverse time three-dimensional structure imaging algorithm applied to surface mine exploration

Abstract

The invention discloses a geologic structure elastic wave reverse time three-dimensional structure imaging algorithm applied to surface mine exploration, and the algorithm comprises the following steps: elastic wave reverse time reconstruction: carrying out the reverse time propagation based on elastic wave field data recorded by a station according to a preset speed model, and reconstructing a wave field propagation path; longitudinal wave and transverse wave decoupling separation: separating the elastic wave field subjected to inverse time reconstruction into a longitudinal wave field and a transverse wave field through a Helmholtz decomposition method; grouping imaging conditions: dividing the stations into a plurality of groups, and performing zero-delay cross-correlation calculation on the decoupled longitudinal wave field and transverse wave field of each group. Through elastic wave inverse-time reconstruction, the discontinuous structure of the underground medium is finely described, the resolution limit of a traditional method is broken through, longitudinal and transverse waves are decoupled and separated, the wave field characteristics are accurately distinguished, and the imaging precision is improved; the energy focusing degree is improved under the grouping imaging condition, the tolerance to sparse stations is high, data noise and imaging noise are effectively suppressed, the signal-to-noise ratio is improved, and the method adapts to the complex environment of the surface mine.

Description

Technical Field

[0001] The present invention relates to the technical field, and in particular to a geological structure elastic wave reverse time three-dimensional structure imaging algorithm applied to open-pit mine exploration. Background Art

[0002] At present, for geological structures, abnormal water-bearing bodies, etc. in front of blasting operations, mainly the advanced drilling technology, direct current method for advanced detection, transient electromagnetic method for advanced detection, and traditional seismic method for advanced detection are used for roadway advanced detection and prediction.

[0003] In open-pit mine mining, the accurate detection of geological structures is the core link to ensure blasting safety and optimize the mining plan. At present, although the existing advanced drilling method can directly obtain information such as lithology and structure, the detection range is limited to the area around the drill hole (a one-hole view), and production operations need to be stopped, with high costs and low efficiency; the direct current method relies on resistivity measurement, is easily interfered by metals, and the inversion result can only determine the combined value of the thickness and resistivity of the abnormal body, with insufficient resolution; the transient electromagnetic method is sensitive to low-resistivity bodies, but is affected by volume effects and turn-off time, there are detection blind spots, and the full-space effect leads to fuzzy positioning of the abnormal body; the traditional seismic reflection wave method is restricted by the roadway space and the data processing is complex; the Rayleigh wave method has a short detection distance and is difficult to meet the needs of deep engineering. In addition, passive-source seismic imaging relies on natural earthquake data, the source information is inaccurate and the stations are sparse, resulting in large errors in the imaging results. Although active-source seismic exploration can provide clear signals, it requires artificial excitation of the source, with high costs and affecting the production progress. Summary of the Invention

[0004] In order to solve the problems of small detection range, low resolution, and need for production suspension in traditional methods for open-pit mine exploration, the present invention provides a geological structure elastic wave reverse time three-dimensional structure imaging algorithm applied to open-pit mine exploration.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A geological structure elastic wave reverse time three-dimensional structure imaging algorithm applied to open-pit mine exploration, including the following steps:

[0006] Elastic wave reverse time reconstruction: Based on the elastic wave field data recorded by the stations, perform reverse time propagation according to the preset velocity model to reconstruct the wave field propagation path;

[0007] Longitudinal wave and transverse wave decoupling separation: Separate the elastic wave field reconstructed by reverse time into a longitudinal wave field and a transverse wave field through the Helmholtz decomposition method;

[0008] Group imaging condition: Divide the stations into multiple groups, perform zero-delay cross-correlation calculation on the decoupled longitudinal wave field and transverse wave field of each group to generate a three-dimensional geological structure imaging result.

[0009] Preferably, the elastic wave reverse time reconstruction adopts a second-order time and fourth-order space finite difference method based on a staggered grid to solve the elastic wave field in the reverse time direction.

[0010] Preferably, in the Helmholtz decomposition method, the longitudinal wave field is obtained by calculating the divergence of the wave field, and the transverse wave field is obtained by calculating the curl of the wave field.

[0011] Preferably, the finite difference method adopts an adaptive grid division strategy in the reverse time reconstruction process and dynamically adjusts the grid density according to the rock mass velocity model.

[0012] Preferably, the specific implementation manner of the grouped imaging condition is as follows:

[0013] The stations are divided into at least two groups;

[0014] The cross-group coherence of the decoupled longitudinal wave field and transverse wave field of each group is calculated to generate a stacked imaging result;

[0015] Energy focusing is achieved through the formula I = ∑gi∑gj∫Pgi(t)⋅Sgj(t) dt, where gi and gj are different station groups.

[0016] Preferably, the grouped imaging condition further includes imposing a wave velocity ratio consistency constraint on the imaging result. By jointly inverting the longitudinal wave velocity (Vp) and transverse wave velocity (Vs), the Vp / Vs model is optimized to improve the lithology identification accuracy.

[0017] Preferably, the algorithm is applicable to the joint processing of open-pit mine blasting signals and background noise data, and suppresses noise interference through phase-weighted stacking technology.

[0018] Preferably, the basis for station grouping is the spatial distribution density or signal reception quality, and the number of stations in each group is not less than 3.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. By leveraging the elastic wave reverse time reconstruction technology, the present invention uses the elastic wave field collected by a dense seismic array as the data basis, accurately solves the Green's function, and finely restores the wave field propagation trajectory in the reverse time direction. Compared with the limitation of traditional seismic travel time imaging that can only obtain smooth structure information, this technology can capture the subtle wave field changes at the discontinuities of underground media (such as micro fractures and thin-layer faults), enabling refined characterization of geological structures. For example, it can clearly distinguish small geological anomalies that are difficult to identify by traditional methods, improving the resolution to a new level, providing more accurate three-dimensional geological structure data for open-pit mine exploration, and facilitating precise blasting design and geological analysis.

[0021] 2. By adopting the Helmholtz decomposition method, the longitudinal wave and the transverse wave are accurately separated from the complex elastic wave field. The longitudinal wave (scalar potential) is sensitive to the change of medium density, and the transverse wave (vector potential) is sensitive to the shear property of the medium. After separation, the two wave field characteristics can be analyzed independently. For example, when identifying water-bearing bodies or fractured zones, the longitudinal wave field can reflect the compression characteristics of the medium, and the transverse wave field can reflect the shear deformation characteristics, avoiding imaging interference caused by wave field mixing, improving the judgment accuracy of the geological structure properties (such as the degree of fracture development, fault type), and making the imaging results more accurately reflect the true underground structure.

[0022] 3. Through the grouped imaging condition, by grouping seismic stations and using the coherence of the back-propagating wave fields of different groups of stations for imaging. This method significantly improves the energy focusing degree of the wave field at the discontinuity (conversion point) of the underground medium. Even in the open-pit mine environment with irregular and sparse station layout, the imaging quality can be guaranteed. At the same time, the mechanism of multiplying the wave fields of stations can effectively suppress the environmental noise in the data acquisition stage (such as the interference of mine equipment operation, natural vibration noise) and the noise in the imaging process. For example, in the open-pit mining area with dense metal equipment, the metal interference can be excluded, the geological structure can be clearly presented, adapting to the complex environment of the open-pit mine, ensuring the reliability of the imaging results, and providing a stable basis for safety monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 It is a schematic diagram of the overall algorithm flow of the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0026] Embodiment: Refer to Figure 1 , the elastic wave reverse time three-dimensional structure imaging algorithm for geological structure applied to open-pit mine exploration includes the following steps:

[0027] Elastic wave reverse time reconstruction: Based on the elastic wave field data recorded by the stations, perform reverse time propagation according to the preset velocity model to reconstruct the wave field propagation path;

[0028] Decoupling and separation of longitudinal wave and transverse wave: By using the Helmholtz decomposition method, separate the elastic wave field reconstructed by reverse time into a longitudinal wave field and a transverse wave field;

[0029] Group imaging condition: The stations are divided into multiple groups, and zero-delay cross-correlation calculations are performed on the decoupled P-wave field and S-wave field of each group to generate a three-dimensional geological structure imaging result.

[0030] In the present invention, elastic wave reverse-time reconstruction uses a second-order time and fourth-order space finite-difference method based on a staggered grid to solve the elastic wave field in the reverse time direction.

[0031] In the present invention, in the Helmholtz decomposition method, the P-wave field is obtained by calculating the divergence of the wave field, and the S-wave field is obtained by calculating the curl of the wave field.

[0032] In the present invention, the finite-difference method adopts an adaptive grid division strategy during the reverse-time reconstruction process, and dynamically adjusts the grid density according to the rock mass velocity model.

[0033] In the present invention, the specific implementation method of the group imaging condition is as follows:

[0034] The stations are divided into at least two groups. The basis for station grouping is spatial distribution density or signal reception quality, and the number of stations in each group is not less than 3;

[0035] Cross-group coherence calculations are performed on the decoupled P-wave field and S-wave field of each group to generate a stacked imaging result;

[0036] Energy focusing is achieved through the formula I = ∑gi∑gj∫Pgi(t)⋅Sgj(t) dt, where gi and gj are different station groups.

[0037] In the present invention, the group imaging condition also includes imposing a wave velocity ratio consistency constraint on the imaging result. By jointly inverting the P-wave velocity (Vp) and S-wave velocity (Vs), the Vp / Vs model is optimized to improve the lithology identification accuracy.

[0038] In the present invention, the algorithm is applicable to the joint processing of open-pit mine blasting signals and background noise data, and suppresses noise interference through phase-weighted stacking technology.

[0039] Working principle: In this embodiment, the present invention also proposes a method for using a geological structure elastic wave reverse-time three-dimensional structure imaging algorithm applied to open-pit mine exploration, including the following steps:

[0040] Step 1, elastic wave field recording and reverse-time reconstruction:

[0041] First, deploy a dense seismic array reasonably on the surface or in the roadway of an open-pit mine to collect elastic wave field data generated by blasting, geological activities, etc. in real time. Using the wave field recorded by the stations as the initial condition, apply the fourth-order in space and second-order in time finite-difference time domain method based on the staggered grid format to accurately solve the Green's function, calculate the elastic wave field from the maximum time to the minimum time direction, propagate the wave field recorded by the stations in the reverse time direction, and inversely reconstruct the wave field propagation path to accurately locate the position of the discontinuous structure of the underground medium, providing basic data for subsequent imaging;

[0042] Step two, decouple and separate the P-wave and S-wave:

[0043] For the elastic wave field after inverse time reconstruction, based on the Helmholtz decomposition principle, decompose it into divergence (P-wave field) and curl (S-wave field), perform decoupling operations at each time step, and extract the P-wave and S-wave fields separately. For example, the P-wave field characterizes the compression and expansion characteristics of the medium, and the S-wave field reflects the shear deformation characteristics of the medium. By separating the two wave fields, a pure and independent data source is provided for subsequent imaging processing of different wave fields;

[0044] Step three, implement the grouped imaging condition:

[0045] Divide the seismic stations into multiple groups, perform zero-delay cross-correlation imaging on the decoupled P-wave and S-wave fields of each group of stations, and use the formula I ps (X)=∑t∏iPgi(X,t)Sgi (X,t) to make the back-propagating wave fields of different groups of stations generate energy superposition at the discontinuous points (conversion points) of the underground medium, enhancing the imaging effect of the conversion points. At the same time, the multiplication operation of the station wave fields suppresses the noise signal, and finally generates a high-precision three-dimensional geological structure image, clearly showing the structures such as faults, solution cavities, and fractures in the advanced rock mass of the open-pit mine, providing detailed geological structure information for blasting design, and supporting safety monitoring and hazard warning work.

[0046] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. Geological structure elastic wave reverse time three-dimensional structure imaging algorithm applied to open-pit mine exploration, characterized in that, Including the following steps: Elastic wave reverse-time reconstruction: Based on the elastic wave field data recorded by stations, perform reverse-time propagation according to a preset velocity model to reconstruct the wave field propagation path; P-wave and S-wave decoupling separation: Separate the elastic wave field reconstructed by reverse-time into a P-wave field and an S-wave field through the Helmholtz decomposition method; Grouped imaging condition: Divide the stations into multiple groups, perform zero-delay cross-correlation calculations on the decoupled P-wave field and S-wave field of each group to generate a three-dimensional geological structure imaging result.

2. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, characterized in that: The elastic wave reverse-time reconstruction adopts a second-order time and fourth-order space finite-difference method based on a staggered grid to solve the elastic wave field in the reverse time direction.

3. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, wherein: In the Helmholtz decomposition method, the P-wave field is obtained by calculating the divergence of the wave field, and the S-wave field is obtained by calculating the curl of the wave field.

4. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, wherein: The finite-difference method adopts an adaptive grid division strategy during the reverse-time reconstruction process and dynamically adjusts the grid density according to the rock mass velocity model.

5. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, characterized in that, The specific implementation method of the grouped imaging condition is: Divide the stations into at least two groups; Perform cross-group coherence calculations on the decoupled P-wave field and S-wave field of each group to generate a stacked imaging result; Realize energy focusing through the formula I = ∑gi∑gj∫Pgi(t)⋅Sgj(t) dt, where gi and gj are different station groups.

6. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, characterized in that: The grouped imaging condition also includes imposing a wave velocity ratio consistency constraint on the imaging result. By jointly inverting the P-wave velocity (Vp) and the S-wave velocity (Vs), optimize the Vp / Vs model to improve the lithology identification accuracy.

7. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 1, characterized in that: The algorithm is applicable to the joint processing of open-pit mine blasting signals and background noise data, and suppresses noise interference through the phase-weighted stacking technique.

8. The elastic wave reverse time three-dimensional structural imaging algorithm for open-pit mine exploration according to claim 5, characterized in that: The basis for grouping the stations is the spatial distribution density or the signal reception quality, and the number of stations in each group is not less than 3.

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