Three-dimensional stress field inversion method and system based on numerical simulation

Abstract

The present application relates to the technical field of data processing, in particular to a three-dimensional ground stress field inversion method and system based on numerical simulation. The method comprises: obtaining basic data of a research area, and performing trial disturbance on boundary loads of a three-dimensional numerical model to obtain a candidate correction direction; dividing the measuring points into background measuring points and target measuring points based on the advantage structure surface data; judging whether the candidate correction direction forms an effective regional response according to the background measuring point convergence ratio and the drop amplitude of the background measuring points under the candidate correction direction; when the effective regional response is formed, obtaining a regional background response direction by using the principal stress direction response vector and its deviation drop amount of the background measuring points before and after the trial disturbance; taking the target measuring points which change with the regional background response direction and have a direction deviation drop as effective correction measuring points, and then driving the next round of boundary load correction to obtain the inverted three-dimensional ground stress field. The present application improves the reliability of the inversion result of the three-dimensional ground stress field.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and more specifically to a method and system for inverting three-dimensional geostress fields based on numerical simulation. Background Technology

[0002] Three-dimensional geostress field is an important basic parameter in underground engineering excavation, tunnel layout, slope stability analysis, tunnel support design, and deep resource development. Because the geostress field is affected by various factors such as regional tectonic movements, topography, rock mass burial depth, rock strata attitude, fault joint development, and differences in rock mass mechanical parameters, it is usually difficult to obtain a complete three-dimensional geostress distribution in a region directly from a small number of field test points in actual engineering. Therefore, existing methods generally combine field measurements with numerical simulations to invert the regional geostress field. The commonly used approach is to first obtain geostress state parameters such as the magnitude, direction, or stress tensor of principal stress at several test points through field testing methods such as borehole stress relief, hydraulic fracturing, or acoustic emission. Then, a three-dimensional numerical model is established that includes the topography, rock strata, excavation object, and surrounding rock range of the engineering area, for example, using FLAC3D to establish a regional rock mass calculation model. Finally, by adjusting the model boundary conditions, lateral loads, vertical loads, tectonic stress directions, and load ratios in different directions, the stress state at the test points calculated by the model is gradually made closer to the field measurement results.

[0003] In existing numerical simulation-based three-dimensional geostress field inversion methods, the principal stress magnitude and direction at several measuring points are typically obtained using the hole stress relief method, and initial boundary loads are set in the FLAC3D model. After each round of inversion calculation, the initial correction direction for the boundary load direction in the next round is formed based on the angular deviation between the calculated principal stress direction and the measured principal stress direction. This initial correction direction mainly reflects the numerical correspondence between the principal stress direction error of the measuring point and the boundary load direction, or reflects the decrease in the measuring point direction error after adjusting the boundary load in a certain direction. It cannot determine whether the principal stress direction deviation of the target measuring point forms a consistent boundary load response chain along the boundary load application direction, the background measuring point direction response, and the target measuring point direction deviation. This leads to the measuring points within the control range of the dominant structural surface having their local principal stress reversal caused by the structural surface orientation constraint incorrectly treated as the regional boundary load direction deviation in the next round of correction. This causes the boundary load direction to be erroneously pulled by the measuring points controlled by the local structure, resulting in low reliability of the three-dimensional geostress field inversion results. Summary of the Invention

[0004] To address the issue of low reliability in inversion results of existing methods for three-dimensional geostress field inversion, the present invention aims to provide a three-dimensional geostress field inversion method and system based on numerical simulation. The specific technical solution adopted is as follows: In a first aspect, the present invention provides a three-dimensional geostress field inversion method based on numerical simulation, the method comprising the following steps: Acquire basic data of the study area, including the location of measuring points, dominant structural surface data, and three-dimensional numerical model; The boundary load of the three-dimensional numerical model is subjected to trial calculation perturbation to obtain candidate correction directions; the measuring points are divided into background measuring points and target measuring points based on the dominant structural surface data; based on the convergence ratio and average decrease of the background measuring points under the candidate correction directions, it is determined whether the candidate correction directions form an effective regional response in the background measuring points. When forming an effective regional response, the principal stress direction response vectors of the background measurement points before and after the disturbance and their respective deviation decreases are used to obtain the regional background response direction; the target measurement points that change with the regional background response direction and whose direction deviation decreases are used as effective correction measurement points. The effective correction measurement points are used to drive the next round of boundary load correction to obtain the inverted three-dimensional geostress field.

[0005] Preferably, the step of performing trial perturbations on the boundary loads of the three-dimensional numerical model to obtain candidate correction directions includes: Apply initial boundary loads to the FLAC3D model, run initial inversion calculations, and obtain the calculated maximum principal stress direction for each measuring point; Establish a candidate perturbation set in the direction of the boundary load; For each candidate disturbance in the candidate disturbance set of the boundary load direction, the change in directional deviation of each measuring point before and after the disturbance is calculated based on the angle deviation between the calculated maximum principal stress direction and the measured maximum principal stress direction of each measuring point before and after the disturbance; measuring points whose change in directional deviation is greater than the directional deviation change threshold are regarded as measuring points with effective deviation reduction, and the number of measuring points with effective deviation reduction is counted; the basic data also includes the measured maximum principal stress direction. The boundary load direction adopted by the candidate disturbance with the largest number of measurement points that effectively reduce the deviation is selected as the candidate correction direction.

[0006] Preferably, the step of dividing the measurement points into background measurement points and target measurement points based on the advantageous structural surface data includes: Dominant structural surfaces of the same type that are spatially adjacent and whose rock strata orientations differ within a preset angular tolerance are classified into the same group of dominant structural surfaces. The dominant structural surface data includes the spatial location of the dominant structural surface and the width of its control influence. Based on the location of each measuring point and the spatial location of the dominant structural surfaces, calculate the shortest distance between each measuring point and each group of dominant structural surfaces; For any measuring point, if the shortest distance between any measuring point and all dominant structural surfaces of the group is greater than the control influence width of the corresponding group, then any measuring point is designated as a background measuring point; if the shortest distance between any measuring point and all dominant structural surfaces of the group is less than or equal to the control influence width of the corresponding group, then any measuring point is designated as a target measuring point.

[0007] Preferably, determining whether the candidate correction direction forms an effective region response in the background measurement points based on the convergence ratio and average decrease of the background measurement points under the candidate correction direction includes: For the perturbation corresponding to the candidate correction direction: When the disturbance corresponding to the candidate correction direction meets the preset first condition, it is determined that the candidate correction direction forms an effective region response; when the disturbance corresponding to the candidate correction direction does not meet the preset first condition, it is determined that the candidate correction direction does not form an effective region response. Wherein, the convergence ratio of background measurement points corresponding to the disturbance of the candidate correction direction is the proportion of the number of background measurement points among the measurement points where the deviation has effectively decreased before and after the disturbance of the candidate correction direction to the total number of all background measurement points; the average decrease of the disturbance of the candidate correction direction is the average change in directional deviation of all background measurement points among the measurement points where the deviation has effectively decreased before and after the disturbance of the candidate correction direction. The preset first condition is: the convergence ratio of background measurement points is greater than the background consistency ratio threshold, and the change in average directional deviation is greater than the directional deviation change threshold.

[0008] Preferably, obtaining the regional background response direction by utilizing the principal stress direction response vectors of the background measuring points before and after the disturbance and their respective deviation decreases includes: Obtain the principal stress direction response vector of each background measuring point in the measuring points where the deviation before and after the disturbance is effectively reduced, corresponding to the candidate correction direction; The change in directional deviation of each background measuring point in the measuring points where the deviation effectively decreases before and after the disturbance corresponding to the candidate correction direction is used as a weight. The principal stress direction response vector of the corresponding background measuring points is weighted, summed, and normalized to obtain the regional background response direction corresponding to the disturbance of the candidate correction direction.

[0009] Preferably, determining whether the target measuring point changes with the background response direction of the region includes: Obtain the principal stress direction response vector of the target measurement point before and after the disturbance corresponding to the candidate correction direction; denot the angle between the principal stress direction response vector of the target measurement point and the background response direction of the region as the first angle; if the first angle is less than or equal to the corresponding response angle threshold, and the change in direction deviation of the target measurement point before and after the disturbance corresponding to the candidate correction direction is greater than the effective identification threshold of direction deviation, then it is determined that the target measurement point changes with the background response direction of the region. The target measurement point to be analyzed can be any target measurement point.

[0010] Preferably, if the first included angle is greater than the threshold of the accompanying response angle, and / or the change in the direction deviation of the target measurement point to be analyzed before and after the disturbance corresponding to the candidate correction direction is less than or equal to the effective identification threshold of the direction deviation, then it is determined that the target measurement point to be analyzed does not change with the background response direction of the region.

[0011] Preferably, if the target measurement point to be analyzed does not change with the background response direction of the region, it is determined whether the target measurement point to be analyzed meets the preset second condition. If it does, it is determined that the target measurement point to be analyzed belongs to the structural control measurement point; if it does not, it is determined that the target measurement point to be analyzed is a measurement point to be reviewed. The data on the advantageous structural surfaces also includes the strike of the rock strata; The preset second condition is: the target measurement point to be analyzed is located within the control range of the dominant structural surface, and the direction of the measured maximum principal stress is consistent with the direction of the rock strata strike of the dominant structural surface.

[0012] Preferably, the step of using the effective correction measuring points to drive the next round of boundary load correction to obtain the inverted three-dimensional geostress field includes: The effective corrected measuring points are used as the basis for the correction of the boundary load in the next round. The boundary load is corrected, and the three-dimensional numerical model is run again to update the calculated maximum principal stress direction of the measuring points until the inversion termination condition is met, and the inverted three-dimensional geostress field is output.

[0013] Secondly, the present invention provides a three-dimensional geostress field inversion system based on numerical simulation, the system comprising a memory and a processor, the processor executing a computer program stored in the memory to implement the method of the first aspect described above.

[0014] The present invention has at least the following beneficial effects: This invention obtains candidate correction directions by perturbing the boundary loads of a three-dimensional numerical model. Based on the dominant structural surface data, the measuring points are divided into background measuring points and target measuring points. Furthermore, based on the convergence ratio and average decrease of the background measuring points under the candidate correction direction, a comprehensive judgment is made as to whether the candidate correction direction forms an effective regional response in the background measuring points. From the perspective of the overall regional stress field response, this objectively assesses whether the candidate correction direction truly acts on the background region rather than local anomalies, thus effectively eliminating false correction directions and ensuring that the direction used for subsequent inversion correction has regional representativeness and statistical reliability. This guarantees the reliability and stability of the three-dimensional geostress field inversion iteration process from the source. Under the premise of confirming that the candidate correction direction forms an effective regional response, the principal stress of the background measuring points before and after the perturbation is further utilized. By analyzing the force direction response vector and its respective deviation decrease, the regional background response direction reflecting the true stress response trend of the region is extracted. Target measuring points whose directional deviation decreases along with the regional background response direction are used as effective correction measuring points. This method can accurately distinguish whether the directional deviation of the measuring points originates from the regional boundary load direction error or from the stress reversal caused by the control of local dominant structural surfaces. This ensures that only measuring points that truly follow the coordinated response of the regional background are used to drive the next round of boundary load correction, avoiding the erroneous inclusion of target measuring points within the control range of structural surfaces as regional boundary load direction deviations due to local principal stress reversals. The resulting three-dimensional geostress field satisfies the regional tectonic stress distribution law and is not distorted by abnormal deviations of local measuring points, exhibiting higher spatial consistency and engineering practical value across the entire field. The method provided by this invention fundamentally solves the technical problem in existing inversion methods where the boundary load direction is erroneously guided due to the inability to distinguish between regional boundary load response and local structural control response, thus improving the reliability of the three-dimensional geostress field inversion results. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating the three-dimensional geostress field inversion method based on numerical simulation provided in an embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of the three-dimensional geostress field inversion method and system based on numerical simulation proposed in accordance with the present invention is provided in conjunction with the accompanying drawings and preferred embodiments.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details the specific scheme of the numerical simulation-based three-dimensional geostress field inversion method and system provided by this invention.

[0020] Example of a three-dimensional geostress field inversion method based on numerical simulation: This embodiment proposes a three-dimensional geostress field inversion method based on numerical simulation, such as... Figure 1 As shown, the three-dimensional geostress field inversion method based on numerical simulation in this embodiment includes the following steps: Step S1: Obtain basic data of the study area, including the location of measuring points, dominant structural surface data, and three-dimensional numerical model.

[0021] When performing a three-dimensional inversion of the geostress field in the study area, it is necessary to first collect basic data for the inversion within the study area, ensuring that the borehole stress relief method measuring points, dominant structural surfaces, and the FLAC3D numerical model are in the same spatial coordinate system. The basic data includes the locations of the measuring points, measured geostress data, dominant structural surface data, and the three-dimensional numerical model, which includes initial boundary load data. The measuring points are borehole stress relief method measuring points deployed within the study area, with a minimum of four points, typically ranging from six to twenty. In this embodiment, sixteen measuring points are used, evenly distributed throughout the study area. Dominant structural surface data includes the spatial location, control influence width, strike, and dip angle of the dominant structural surface. The control influence width can be obtained from geological exploration data, and its value typically ranges from 5m to 20m. The measured in-situ stress data includes the measured principal stress direction and the measured principal stress magnitude. The measured in-situ stress data is obtained by collecting strain release data at the measuring point through the borehole stress relief method and using the existing in-situ stress back calculation method. The specific acquisition method is existing technology and will not be elaborated on here.

[0022] A FLAC3D three-dimensional numerical model was established, with the model boundary set at 3 to 5 times the characteristic scale outside the engineering disturbance range. Locally refined meshes were used near measuring points and dominant structural surfaces, with mesh sizes ranging from 1m to 5m near measuring points and from 10m to 50m in the far-field region. The model was input with parameters including rock mass density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, equivalent stiffness of structural surfaces, and anisotropy parameters. Initial vertical stresses were set based on burial depth and rock mass density, while horizontal boundary loads were set based on regional tectonic direction and lateral pressure coefficients. The lateral pressure coefficients were initially selected within the range of 0.5 to 2.0 based on historical inversion data or pre-inversion trial calculations for the same region.

[0023] Step S2: Perform trial calculations to disturb the boundary loads of the three-dimensional numerical model to obtain candidate correction directions; divide the measurement points into background measurement points and target measurement points based on the dominant structural surface data; determine whether the candidate correction direction forms an effective regional response in the background measurement points according to the convergence ratio and average decrease of the background measurement points under the candidate correction direction.

[0024] If the boundary load in a certain direction is not set properly, the calculated maximum principal stress direction at multiple measuring points in the model will deviate systematically from the measured principal stress direction. Therefore, this step follows the existing inversion approach and obtains candidate correction directions that can reduce the measurement point direction error through small trial calculations and perturbations.

[0025] Specifically, an initial boundary load is applied to the FLAC3D model, and an initial inversion calculation is run to obtain the calculated maximum principal stress direction at each measuring point. Then, the angle between the calculated maximum principal stress direction and the measured maximum principal stress direction at each measuring point is calculated. This angle is recorded as the deviation between the calculated maximum principal stress direction and the measured maximum principal stress direction. The larger the value, the more obvious the deviation between the maximum principal stress direction calculated by the FLAC3D model at that measuring point and the measured direction by the hole stress relief method. This indicates that the current boundary load settings, local rock mass parameters, or structural surface expressions do not adequately constrain the state of the measuring point's direction.

[0026] Furthermore, a candidate perturbation set is established in the direction of the boundary load. Specifically, this set consists of multiple perturbation angles, each being an azimuth deflection angle representing a planar torsion around the vertical axis in the direction of maximum horizontal stress. The difference between two adjacent perturbation angles is... The number of elements in the candidate perturbation set can be set by the implementer according to the specific situation, for example, the number can be set to 10.

[0027] For each candidate perturbation in the candidate perturbation set along the boundary load direction, the change in directional deviation at each measuring point before and after the perturbation is calculated based on the angular deviation between the calculated and measured maximum principal stress directions. Specifically, for each measuring point, the angular deviation between the calculated and measured maximum principal stress directions before the perturbation is subtracted from the angular deviation after the perturbation. This difference is used as the change in directional deviation at the measuring point before and after the perturbation. A change in directional deviation greater than 0 indicates that the measuring point moves closer to the measured maximum principal stress direction after the perturbation; a change in directional deviation less than or equal to 0 indicates that the measuring point has not achieved effective convergence with the perturbation; a change in directional deviation close to 0 indicates that the perturbation does not significantly improve the directional error at the measuring point. This method allows for the determination of the change in directional deviation at each measuring point before and after each candidate perturbation.

[0028] For each candidate disturbance, the measurement points whose change in directional deviation exceeds the directional deviation change threshold before and after the disturbance are considered as measurement points with effective deviation reduction, and the number of measurement points with effective deviation reduction is counted. Using this method, the number of measurement points with effective deviation reduction corresponding to each candidate disturbance can be obtained. The boundary load direction adopted by the candidate disturbance with the largest number of measurement points with effective deviation reduction is selected as the candidate correction direction. Specifically, if there is more than one candidate disturbance with the largest number of measurement points with effective deviation reduction, the difference between two adjacent disturbance angles is halved, and the disturbance set of the untried interval is reconstructed. The upper limit for retry is set to 3 times. If this is still not satisfied, the boundary load direction adopted by the candidate disturbance with the largest average reduction magnitude is forcibly selected as the candidate correction direction.

[0029] Since the candidate correction direction obtained in the above steps only reflects the decrease in error value, it cannot be concluded that the deviation of the target measuring point necessarily originates from the error in the direction of the boundary load in the region. Therefore, it is necessary to determine whether the candidate correction direction forms a real boundary load response chain through subsequent steps.

[0030] After the boundary load is applied to the model, a consistent principal stress direction response should first be formed in the background measuring points far from the control of the local structure. Only if the target measuring point changes synchronously with the background response of the region can it be said that its directional deviation belongs to the direction error of the boundary load. If the target measuring point does not change with the background response, but its directional change is closer to the direction controlled by the adjacent dominant structural surface, it indicates that the deviation belongs to the direction of local structural control and should not participate in the correction of the boundary load direction in the next round. Therefore, the measuring points are first divided into background measuring points and target measuring points based on the dominant structural surface data.

[0031] Specifically, firstly, dominant structural surfaces of the same type that are spatially adjacent and whose strike differences are within a preset angle tolerance are grouped into the same group of dominant structural surfaces, meaning that all dominant structural surfaces can be divided into multiple groups. The preset angle tolerance can be set to 15 degrees.

[0032] Based on the location of each measuring point and the spatial location of the dominant structural surfaces, calculate the shortest distance between each measuring point and each group of dominant structural surfaces.

[0033] For any measurement point, obtain the shortest distance between the measurement point and each group of dominant structural surfaces. If the shortest distance between the measurement point and all groups of dominant structural surfaces is greater than the control influence width of the corresponding group, then the measurement point is used as a background measurement point. If the shortest distance between the measurement point and all groups of dominant structural surfaces is less than or equal to the control influence width of the corresponding group, then the measurement point is used as a target measurement point.

[0034] Background measuring points serve as reference points to reflect the response of the boundary load in the region. It is only meaningful to determine whether the target measuring point will respond accordingly after confirming that the candidate boundary load direction can produce an effective response in the background measuring points. If the candidate correction direction cannot achieve uniform convergence in the background measuring points, it indicates that the candidate correction direction itself is unreliable, and the deviation of the target measuring point should not be used to further correct that direction.

[0035] For the perturbation corresponding to the candidate correction direction: The proportion of background measuring points among those whose deviations effectively decreased before and after the disturbance to the total number of background measuring points is taken as the background measuring point convergence ratio. A larger background measuring point convergence ratio indicates that under the candidate disturbance, more background measuring points have their calculated principal stress directions closer to the measured direction, and the more likely the boundary load direction is to have a real regulating effect on the regional background stress field. Considering that simply counting the convergence number is insufficient to indicate that background measuring points have formed a stable response (as there may be a few background measuring points with significant error reduction while others show weak changes), it is necessary to further calculate the average decrease in the background measuring points. Specifically, the average change in directional deviation among all background measuring points whose deviations effectively decreased before and after the candidate disturbance is taken as the average decrease in the disturbance. A larger average decrease indicates that the background measuring points not only converge in number but also have a more significant average improvement, and the regulating effect of the candidate boundary load direction on the regional background stress field is more stable. A smaller average decrease indicates that although some background measuring points meet the convergence condition, the overall improvement is limited and may not be sufficient to support the candidate direction as a reliable regional boundary load correction direction. When the disturbance meets a preset first condition, the candidate correction direction is determined to form an effective regional response; when the disturbance does not meet the preset first condition, the candidate correction direction is determined not to form an effective regional response. At this point, a new candidate disturbance set is constructed, and the candidate correction direction is redefined. The preset first condition is: the background measurement point convergence ratio is greater than the background consistency ratio threshold, and the average direction deviation change is greater than the direction deviation change threshold. The background consistency ratio threshold can be 60%, and the direction deviation change threshold can be 1 degree.

[0036] Step S3: When forming an effective regional response, the regional background response direction is obtained by using the principal stress direction response vectors of the background measuring points before and after the disturbance and their respective deviation decreases; the target measuring points that change with the regional background response direction and whose direction deviation decreases are taken as effective correction measuring points.

[0037] When the candidate correction direction forms an effective regional response in the background measuring points, it is necessary to extract the regional background response direction. Considering that after the boundary load is introduced into the complex rock mass, it will be affected by the rock strata, structural surfaces and boundary constraints. The actual movement direction of the principal stress direction of the internal measuring points may not be consistent with the direction of the external load. Therefore, this embodiment does not directly equate the direction of the boundary load application with the direction of the response inside the model. This embodiment needs to determine the angle between the vectors of the calculated maximum principal stress direction before and after the disturbance.

[0038] For the perturbation corresponding to the candidate correction direction: Any target measurement point is designated as the target measurement point to be analyzed. The dot product of the calculated maximum principal stress direction vectors of the target measurement point before and after the disturbance is obtained. If the dot product is less than 0, the inverse of the calculated maximum principal stress direction vector of the target measurement point after the disturbance is designated as the first eigenvector of the target measurement point to be analyzed, so as to eliminate the jump caused by the equivalent positive and negative directions of the principal stress axis. If the dot product is greater than or equal to 0, the calculated maximum principal stress direction vector of the target measurement point after the candidate disturbance is directly designated as the first eigenvector of the target measurement point to be analyzed.

[0039] After obtaining the first eigenvector of the target measurement point to be analyzed, and combining the first eigenvector of the target measurement point to be analyzed with the calculated maximum principal stress direction vector of the target measurement point before the disturbance, the principal stress direction response vector of the target measurement point to be analyzed is determined. The principal stress direction response vector of the target measurement point before and after the disturbance corresponding to the candidate correction direction can be expressed as: in, This represents the principal stress direction response vector of the target measurement point before and after the disturbance, corresponding to the candidate correction direction. This represents the first eigenvector of the target measurement point to be analyzed after perturbation, corresponding to the candidate correction direction. This represents the direction vector of the calculated maximum principal stress at the target measurement point before the disturbance. Indicates the length of the modulus.

[0040] Specifically, when calculating the principal stress direction response vector using the above formula, if the following occurs... equal If the target measurement point does not form a directional response to the disturbance, its principal stress direction response vector is set to zero and it is removed when calculating the average response direction or the regional background response direction.

[0041] The principal stress direction response vectors of the target measurement points before and after the disturbance corresponding to the candidate correction direction are used to characterize the movement direction of the principal stress direction of the target measurement points after the disturbance corresponding to the candidate correction direction. If the principal stress direction response vectors of multiple background measurement points have high consistency, it indicates that the corresponding boundary load disturbance has formed a relatively stable regional direction response within the model.

[0042] Using the above method, we can obtain the principal stress direction response vector of each target measuring point before and after the disturbance corresponding to the candidate correction direction. Similarly, by replacing the target measuring point with the background measuring point, we can obtain the principal stress direction response vector of each background measuring point before and after the disturbance corresponding to the candidate correction direction using the above method.

[0043] In step S2 of this embodiment, the measurement points with effective reduction in deviation before and after disturbance corresponding to the candidate correction direction have been selected, that is, the principal stress direction response vector of each background measurement point in the measurement points with effective reduction in deviation before and after disturbance corresponding to the candidate correction direction can be obtained.

[0044] For the disturbance corresponding to the candidate correction direction, the change in directional deviation of each background measuring point among the measuring points where the deviation effectively decreases before and after the disturbance corresponding to the candidate correction direction is used as a weight. The principal stress direction response vectors of the corresponding background measuring points are then weighted, summed, and normalized to obtain the regional background response direction corresponding to the disturbance corresponding to the candidate correction direction. The regional background response direction corresponding to the disturbance corresponding to the candidate correction direction can be expressed as: in, This indicates the region background response direction corresponding to the perturbation corresponding to the candidate correction direction. This indicates the number of background measurement points among the measurement points where the deviation before and after the disturbance effectively decreased according to the candidate correction direction. This represents the change in directional deviation of the j-th background measuring point among the measuring points where the deviation effectively decreases before and after the disturbance, corresponding to the candidate correction direction. This represents the principal stress direction response vector of the j-th background measuring point among the measuring points where the deviation before and after the disturbance effectively decreases, corresponding to the candidate correction direction.

[0045] In this embodiment, the change in directional deviation is used as a weight because background measurement points with a more significant decrease in directional deviation are better able to reflect the effective adjustment effect of the boundary load direction on the regional background stress field. Therefore, the regional background response direction is not the direction of the external boundary load itself, but rather the actual response reference formed by the boundary load within the model.

[0046] Specifically, if the magnitude of the vector after weighted summation is 0, that is... If the value is 0, it is determined that the candidate perturbation has not formed a valid response with the same direction in the background region. The current perturbation is skipped, and a new candidate correction direction is selected.

[0047] After obtaining the regional background response direction corresponding to the disturbance of the candidate correction direction, for the target measurement point to be analyzed, the angle between the principal stress direction response vector of the target measurement point before and after the disturbance corresponding to the candidate correction direction and the regional background response direction corresponding to the disturbance corresponding to the candidate correction direction is denoted as the first angle. The smaller the first angle, the closer the direction change of the target measurement point is to the regional background response direction, and the more likely the target measurement point is to form a response in the same direction as the candidate boundary load disturbance. The larger the first angle, the more the direction response of the target measurement point deviates from the regional background response direction, and the more likely the change in the principal stress direction of the target measurement point is to be controlled by the local structure. Based on this, if the first angle is less than or equal to the response angle threshold, and the change in the direction deviation of the target measurement point before and after the disturbance corresponding to the candidate correction direction is greater than the effective identification threshold of the direction deviation, it is determined that the target measurement point changes with the regional background response direction. At this time, the target measurement point effectively converges towards the measured direction under the disturbance and is consistent with the regional background response direction; otherwise, it is determined that the target measurement point does not change with the regional background response direction. Among them, the threshold for the accompanying response angle can be 15 degrees, and the effective recognition threshold for the direction deviation can be 0.5 degrees.

[0048] If the change in directional deviation of the target measurement point to be analyzed is greater than the aforementioned effective directional deviation identification threshold, then the target measurement point to be analyzed is determined to be a target measurement point with decreasing directional deviation. The target structural surface corresponding to the target measurement point to be analyzed is the dominant structural surface that is closest to the target measurement point.

[0049] Using the above method, target measurement points that change with the direction of the background response in the same area and whose direction deviation decreases can be selected as effective correction measurement points.

[0050] The following explanation uses the target measurement point to be analyzed as an example. When the target measurement point does not change with the background response direction of the same area, it is determined whether the target measurement point meets the preset second condition. If it does, the target measurement point is determined to be a structural control measurement point; if it does not, the target measurement point is determined to be a verification measurement point. The preset second condition is: the target measurement point is located within the control range of the dominant structural plane, and the direction of the measured maximum principal stress is consistent with the strike direction of the rock strata of the dominant structural plane.

[0051] Whether the target measurement point to be analyzed is located within the control range of the dominant structural surface can be determined in the following way: the dominant structural surface closest to the target measurement point to be analyzed is denoted as the target structural surface corresponding to the target measurement point to be analyzed. The distance between the target measurement point to be analyzed and its corresponding target structural surface is obtained. If the distance is less than or equal to the control influence width of the target structural surface corresponding to the target measurement point to be analyzed, it is determined that the target measurement point to be analyzed is located within the control range of the dominant structural surface; if the distance is greater than the control influence width of the target structural surface corresponding to the target measurement point to be analyzed, it is determined that the target measurement point to be analyzed is not located within the control range of the dominant structural surface.

[0052] Whether the direction of the measured maximum principal stress at the target measurement point is consistent with the strike direction of the dominant structural plane can be determined as follows: If the angle between the direction of the measured maximum principal stress at the target measurement point and the strike direction of the corresponding target structural plane is less than or equal to a preset second angle threshold, then the direction of the measured maximum principal stress at the target measurement point is determined to be consistent with the strike direction of the dominant structural plane; if the angle between the direction of the measured maximum principal stress at the target measurement point and the strike direction of the corresponding target structural plane is greater than the preset second angle threshold, then the direction of the measured maximum principal stress at the target measurement point is determined to be inconsistent with the strike direction of the dominant structural plane. The preset second angle threshold can be 15 degrees.

[0053] The measuring points to be verified will not participate in the boundary load direction correction in this round, and will be re-evaluated after the candidate correction direction changes in the next round. The principal stress direction deviation of the structural control measuring points will no longer be used to correct the boundary load direction of the region, but will only serve as a reference for the correction of the equivalent stiffness, anisotropic modulus or contact parameters of the local structural surface. The local parameter correction range in a single round is determined based on the parameter sensitivity test of the historical model, and is usually controlled within 5% to 15% of the original parameter, for example, it can be 5%.

[0054] Step S4: Use the effective correction measuring points to drive the next round of boundary load correction to obtain the inverted three-dimensional geostress field.

[0055] The above steps identified effective correction measurement points, which serve as the basis for the next round of boundary load direction correction. The boundary load is adjusted preferentially along the direction that further reduces the average directional deviation of the effective correction measurement points, thus correcting the boundary load in the FLAC3D model. The single-round correction angle for the boundary load direction is determined based on the change range of the candidate directions in two consecutive rounds, and is typically set to... to For example, it can be Specifically, when determining the correction parameters for the next round, the candidate correction direction determined in the current round is used as the reference direction. Then, the average principal stress direction response vector of the effective correction measurement points is projected onto the horizontal plane to obtain the corresponding horizontal projection vector. The average principal stress direction response vector of the effective correction measurement points can be obtained as follows: obtain the principal stress direction response vectors of all effective correction measurement points, sum them arithmetically, and then divide the summed vector by its own modulus for normalization to obtain the average principal stress direction response vector of the effective correction measurement points. Next, the plane deflection rotation direction of the above-mentioned horizontal projection vector relative to the above-mentioned reference direction is calculated. Finally, based on the plane deflection rotation direction, the azimuth angle of the above-mentioned reference direction is superimposed with the corresponding single-round correction angle (for example, when the deflection rotation direction is clockwise, a negative single-round correction angle is superimposed; when the deflection rotation direction is counterclockwise, a positive single-round correction angle is superimposed). The updated direction obtained after this angle superposition is directly used as the boundary load application direction of the next round of the FLAC3D model. Specifically, when performing the first inversion calculation and lacking two consecutive rounds of historical comparison data, the first round correction angle for the boundary load direction is uniformly assigned a preset angle (e.g., 3 degrees). The average principal stress of the effective correction measurement points is compared with the measured principal stress. If the magnitude is too small, the vertical and horizontal boundary loads are increased proportionally according to the single-round correction ratio; if the magnitude is too large, the magnitudes are decreased.

[0056] After completing the correction, FLAC3D is rerun to obtain the updated principal stress magnitude, direction, and regional stress distribution at the measurement points. Steps S2 and S3 are then repeated to update the effective correction measurement points until the inversion termination condition is met. The inverted three-dimensional geostress field is output, including the magnitude and direction of the maximum and minimum principal stresses for each grid element, the direction and magnitude of the boundary loads, the set of effective correction measurement points, the set of structural control measurement points, and the set of measurement points to be verified. The inversion termination condition is that the deviation between the average calculated maximum principal stress direction and the measured maximum principal stress direction of the effective correction measurement points is less than 5 degrees, or the preset maximum number of inversion iterations is reached. The preset maximum number of inversion iterations can be 30.

[0057] Thus, the method described in this embodiment has been used to invert the three-dimensional geostress field of the study area.

[0058] This embodiment obtains candidate correction directions by performing trial perturbations on the boundary loads of the three-dimensional numerical model. Based on the dominant structural surface data, the measuring points are divided into background measuring points and target measuring points. Furthermore, based on the convergence ratio and average decrease of the background measuring points under the candidate correction directions, a comprehensive judgment is made as to whether the candidate correction direction forms an effective regional response in the background measuring points. From the perspective of the overall regional stress field response, it objectively evaluates whether the candidate correction direction truly acts on the background region rather than local anomalies, thereby effectively eliminating false correction directions and ensuring that the directions used for subsequent inversion corrections have regional representativeness and statistical reliability. This ensures the reliability and stability of the three-dimensional geostress field inversion iteration process from the source. Under the premise that the candidate correction direction forms an effective regional response, the principal components of the background measuring points before and after the trial perturbation are further utilized... By analyzing the stress direction response vector and its respective deviation decrease, the regional background response direction reflecting the true stress response trend of the region is extracted. Target measuring points whose directional deviation decreases along with the regional background response direction are used as effective correction measuring points. This method can accurately distinguish whether the directional deviation of the measuring points originates from the regional boundary load direction error or from the stress reversal caused by the control of local dominant structural surfaces. This ensures that only measuring points that truly follow the coordinated response of the regional background are used to drive the next round of boundary load correction, avoiding the erroneous inclusion of target measuring points within the structural surface control range as regional boundary load direction deviations due to local principal stress reversals. The resulting three-dimensional geostress field satisfies the regional tectonic stress distribution law and is not distorted by abnormal deviations of local measuring points, exhibiting higher spatial consistency and engineering practical value across the entire field. The method provided in this embodiment fundamentally solves the technical problem in existing inversion methods where the boundary load direction is erroneously pulled due to the inability to distinguish between regional boundary load response and local structural control response, thus improving the reliability of the three-dimensional geostress field inversion results.

[0059] Example of a three-dimensional geostress field inversion system based on numerical simulation: The numerical simulation-based three-dimensional geostress field inversion system of this embodiment includes a memory and a processor. The processor executes the computer program stored in the memory to implement the numerical simulation-based three-dimensional geostress field inversion method described above.

[0060] Since the numerical simulation-based three-dimensional geostress field inversion method has already been described in the embodiment of the numerical simulation-based three-dimensional geostress field inversion method, this embodiment will not repeat the numerical simulation-based three-dimensional geostress field inversion method.

[0061] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for inverting a three-dimensional geostress field based on numerical simulation, characterized in that, The method includes the following steps: Acquire basic data of the study area, including the location of measuring points, dominant structural surface data, and three-dimensional numerical model; The boundary load of the three-dimensional numerical model is subjected to trial calculation perturbation to obtain candidate correction directions; the measuring points are divided into background measuring points and target measuring points based on the dominant structural surface data; based on the convergence ratio and average decrease of the background measuring points under the candidate correction directions, it is determined whether the candidate correction directions form an effective regional response in the background measuring points. When forming an effective regional response, the principal stress direction response vectors of the background measurement points before and after the disturbance and their respective deviation decreases are used to obtain the regional background response direction; the target measurement points that change with the regional background response direction and whose direction deviation decreases are used as effective correction measurement points. The effective correction measurement points are used to drive the next round of boundary load correction to obtain the inverted three-dimensional geostress field.

2. The three-dimensional geostress field inversion method based on numerical simulation according to claim 1, characterized in that, The step of performing trial perturbations on the boundary loads of the three-dimensional numerical model to obtain candidate correction directions includes: Apply initial boundary loads to the FLAC3D model, run initial inversion calculations, and obtain the calculated maximum principal stress direction for each measuring point; Establish a candidate perturbation set in the direction of the boundary load; For each candidate disturbance in the candidate disturbance set of the boundary load direction, the change in directional deviation of each measuring point before and after the disturbance is calculated based on the angle deviation between the calculated maximum principal stress direction and the measured maximum principal stress direction of each measuring point before and after the disturbance; measuring points whose change in directional deviation is greater than the directional deviation change threshold are regarded as measuring points with effective deviation reduction, and the number of measuring points with effective deviation reduction is counted; the basic data also includes the measured maximum principal stress direction. The boundary load direction adopted by the candidate disturbance with the largest number of measurement points that effectively reduce the deviation is selected as the candidate correction direction.

3. The three-dimensional geostress field inversion method based on numerical simulation according to claim 1, characterized in that, The process of dividing the measurement points into background measurement points and target measurement points based on the advantageous structural surface data includes: Dominant structural surfaces of the same type that are spatially adjacent and whose rock strata orientations differ within a preset angular tolerance are classified into the same group of dominant structural surfaces. The dominant structural surface data includes the spatial location of the dominant structural surface and the width of its control influence. Based on the location of each measuring point and the spatial location of the dominant structural surfaces, calculate the shortest distance between each measuring point and each group of dominant structural surfaces; For any measuring point, if the shortest distance between any measuring point and all dominant structural surfaces of the group is greater than the control influence width of the corresponding group, then any measuring point is designated as a background measuring point; if the shortest distance between any measuring point and all dominant structural surfaces of the group is less than or equal to the control influence width of the corresponding group, then any measuring point is designated as a target measuring point.

4. The three-dimensional geostress field inversion method based on numerical simulation according to claim 2, characterized in that, The step of determining whether the candidate correction direction forms an effective region response in the background measurement points based on the convergence ratio and average decrease of the background measurement points under the candidate correction direction includes: For the perturbation corresponding to the candidate correction direction: When the disturbance corresponding to the candidate correction direction meets the preset first condition, it is determined that the candidate correction direction forms an effective region response; when the disturbance corresponding to the candidate correction direction does not meet the preset first condition, it is determined that the candidate correction direction does not form an effective region response. Wherein, the convergence ratio of background measurement points corresponding to the disturbance of the candidate correction direction is the proportion of the number of background measurement points among the measurement points where the deviation has effectively decreased before and after the disturbance of the candidate correction direction to the total number of all background measurement points; the average decrease of the disturbance of the candidate correction direction is the average change in directional deviation of all background measurement points among the measurement points where the deviation has effectively decreased before and after the disturbance of the candidate correction direction. The preset first condition is: the convergence ratio of background measurement points is greater than the background consistency ratio threshold, and the change in average directional deviation is greater than the directional deviation change threshold.

5. The three-dimensional geostress field inversion method based on numerical simulation according to claim 2, characterized in that, The method of obtaining the regional background response direction by utilizing the principal stress direction response vectors of background measurement points before and after the disturbance and their respective deviation decreases includes: Obtain the principal stress direction response vector of each background measuring point in the measuring points where the deviation before and after the disturbance is effectively reduced, corresponding to the candidate correction direction; The change in directional deviation of each background measuring point in the measuring points where the deviation effectively decreases before and after the disturbance corresponding to the candidate correction direction is used as a weight. The principal stress direction response vector of the corresponding background measuring points is weighted, summed, and normalized to obtain the regional background response direction corresponding to the disturbance of the candidate correction direction.

6. The three-dimensional geostress field inversion method based on numerical simulation according to claim 5, characterized in that, Determining whether the target measurement point changes with the background response direction of the area includes: Obtain the principal stress direction response vector of the target measurement point before and after the disturbance corresponding to the candidate correction direction; denot the angle between the principal stress direction response vector of the target measurement point and the background response direction of the region as the first angle; if the first angle is less than or equal to the corresponding response angle threshold, and the change in direction deviation of the target measurement point before and after the disturbance corresponding to the candidate correction direction is greater than the effective identification threshold of direction deviation, then it is determined that the target measurement point changes with the background response direction of the region. The target measurement point to be analyzed can be any target measurement point.

7. The three-dimensional geostress field inversion method based on numerical simulation according to claim 6, characterized in that, If the first included angle is greater than the threshold of the accompanying response angle, and / or the change in the direction deviation of the target measurement point to be analyzed before and after the disturbance corresponding to the candidate correction direction is less than or equal to the effective identification threshold of the direction deviation, then it is determined that the target measurement point to be analyzed does not change with the background response direction of the region.

8. The three-dimensional geostress field inversion method based on numerical simulation according to claim 7, characterized in that, If the target measurement point to be analyzed does not change with the background response direction of the area, it is determined whether the target measurement point to be analyzed meets the preset second condition. If it does, it is determined that the target measurement point to be analyzed belongs to the structural control measurement point; if it does not, it is determined that the target measurement point to be analyzed is a measurement point to be reviewed. The data on the advantageous structural surfaces also includes the strike of the rock strata; The preset second condition is: the target measurement point to be analyzed is located within the control range of the dominant structural surface, and the direction of the measured maximum principal stress is consistent with the direction of the rock strata strike of the dominant structural surface.

9. The three-dimensional geostress field inversion method based on numerical simulation according to claim 1, characterized in that, The process of using the effective correction measuring points to drive the next round of boundary load correction to obtain the inverted three-dimensional geostress field includes: The effective corrected measuring points are used as the basis for the correction of the boundary load in the next round. The boundary load is corrected, and the three-dimensional numerical model is run again to update the calculated maximum principal stress direction of the measuring points until the inversion termination condition is met, and the inverted three-dimensional geostress field is output.

10. A three-dimensional geostress field inversion system based on numerical simulation, the system comprising a memory and a processor, characterized in that, The processor executes the computer program stored in the memory to implement the method of claim 1.

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