Rock mass initial crustal stress field inversion method and system

Abstract

The invention relates to the technical field of rock mass mechanics, discloses a rock mass initial crustal stress field inversion method and system, and aims to solve the problem of insufficient precision of an existing method. The scheme mainly comprises data collection and modeling, temperature stress field inversion, seepage stress field inversion, tectonic stress extraction and crustal stress field inversion. According to the method, the temperature field and the seepage field are calculated through inversion to peel off the influence of the temperature field and the seepage field on the actually measured crustal stress, non-tectonic stress interference is eliminated, the inversion precision of the initial crustal stress field of the rock mass is improved, and the method is particularly suitable for complex geological environments with high rock temperature, high water pressure and high crustal stress.

Description

Technical Field

[0001] This invention relates to the field of rock mechanics technology, specifically to a method and system for inverting the initial geostress field of rock mass. Background Technology

[0002] In-situ stress is one of the most fundamental and critical parameters in rock mass engineering design and construction, such as in tunnels, mines, slopes, and dam foundations. Rock mass in-situ stress inversion refers to using measured in-situ stress at multiple measuring points to infer the in-situ stress field across the entire region or within the project's influence area. Determining the in-situ stress field through inversion allows for safer and more reliable engineering designs, optimized construction plans, and explanations of anomalies observed during construction or operation.

[0003] Traditional inversion methods for geostress fields typically model based on a single factor: tectonic stress field or self-weight stress field. This means they only consider the influence of these two fields and directly invert the stress based on measured data. However, in deep underground engineering projects such as buried hydraulic tunnels, transportation tunnels, and mine roadways, temperature and seepage fields significantly alter the mechanical response of the rock mass. Thermal expansion stress caused by temperature gradients and seepage pressure caused by seepage can mask the true tectonic stress. In other words, measured geostress values ​​contain significant temperature and seepage stress components. Existing methods that directly invert based on measured stress ignore the effects of thermal stress caused by temperature gradients (e.g., in high rock temperature environments) and fluid-structure interaction stress generated by seepage (e.g., in high water pressure environments). They fail to effectively distinguish and isolate the interference of temperature and seepage stresses on measured geostress, severely distorting the true tectonic stress field distribution. This results in an inaccurate initial geostress field that fails to accurately reflect the true stress state of the rock mass, posing potential risks to engineering design and safety. Summary of the Invention

[0004] This invention aims to solve the problem of insufficient accuracy in existing methods for inverting the initial geostress field of rock masses, and proposes a method and system for inverting the initial geostress field of rock masses.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] In a first aspect, the present invention provides a method for inverting the initial geostress field of a rock mass, the method comprising:

[0007] Acquire basic and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured in-situ stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability.

[0008] Based on the three-dimensional geological model and the corresponding thermal conductivity, a three-dimensional temperature field model is constructed in combination with the defined temperature field boundary conditions. The temperature field is inverted by using the sum of squares of the differences between the measured temperature value and the simulated temperature value as the first objective function through the least squares method to obtain the temperature distribution of the three-dimensional temperature field model. The initial temperature stress field is calculated based on the temperature distribution and the temperature gradient method.

[0009] Based on the three-dimensional geological model and the corresponding permeability coefficient, a three-dimensional seepage field model is constructed in combination with the defined seepage field boundary conditions. The sum of squares of the differences between the measured hydraulic head and the simulated hydraulic head is used as the second objective function to perform seepage field inversion using the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method.

[0010] Subtract the temperature stress component corresponding to the initial temperature stress field and the seepage stress component corresponding to the initial seepage stress field from the measured ground stress values ​​at each stress measuring point to obtain the measured tectonic stress values ​​of the rock mass caused by tectonic activity at each measuring point.

[0011] Based on the measured tectonic stress values, the tectonic stress field is inverted using the least squares method. The inverted tectonic stress field is then superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial geostress field of the rock mass in the engineering area.

[0012] Furthermore, the temperature field boundary conditions include a surface temperature boundary, a surrounding insulating boundary, and a bottom unknown temperature boundary. The surface temperature boundary is determined based on the average air temperature at the corresponding altitude. The surrounding insulating boundary is an adiabatic boundary, and the bottom unknown boundary is an adjustable boundary, which is divided according to the geological structure and surrounding rock characteristics.

[0013] The seepage boundary conditions include a constant water level boundary, a constant water level recharge boundary, and a permeable boundary. The constant water level boundary is a recharged underground river, the constant water level recharge boundary is the river water level, and the permeable boundary is the on-site measured water level.

[0014] Furthermore, the first objective function is as follows:

[0015] ;

[0016] in, Denotes the first objective function. Indicates the first Thermal conductivity at each temperature measuring point Indicates the number of temperature measuring points. Indicates the first Thermal conductivity weighting coefficient for each temperature measuring point Indicates the first Simulated temperature values ​​at each temperature measuring point Indicates the first Measured temperature values ​​at each temperature measuring point;

[0017] The second objective function is as follows:

[0018] ;

[0019] in, Describes the second objective function. Indicates the first The permeability coefficient at each water head measuring point Indicates the number of head measurement points. Indicates the first Seepage weight coefficient at each head measuring point Indicates the first Simulated head values ​​at each head measuring point Indicates the first The measured head values ​​at each head measuring point.

[0020] Furthermore, the formula for calculating the temperature stress of the initial temperature stress field is as follows:

[0021] ;

[0022] in, This indicates the temperature stress in the rock mass. Represents the geothermal gradient. Indicates the coefficient of thermal expansion of the rock mass. Indicates the elastic modulus. Indicates burial depth.

[0023] Furthermore, based on the seepage distribution and the fluid-structure interaction method, the initial seepage stress field is calculated. Specifically, the seepage distribution is transformed into the corresponding mechanical effect distribution through the fluid-structure interaction module of ABAQUS, FLAC3D, or COMSOL to obtain the initial seepage stress field.

[0024] Furthermore, based on the measured tectonic stress values ​​and using the least squares method, the tectonic stress field is inverted, including:

[0025] Based on the aforementioned three-dimensional geological model, a three-dimensional stress field model containing faults is established, and the fault friction coefficient is determined.

[0026] After defining the stress field boundary conditions for the three-dimensional stress field model, the stress is simulated and constructed. The stress field boundary conditions include applying gravitational acceleration throughout the domain and constructing unit normal stress in the X direction, unit normal stress in the Y direction, and shear stress in the XOY plane.

[0027] The NOW coordinates corresponding to the measured structural stress values ​​are converted into XOY coordinates of a three-dimensional stress field model.

[0028] The tectonic stress field is obtained by using the least squares method to invert the tectonic stress field by taking the sum of the squares of the differences between the measured tectonic stress values ​​and the simulated tectonic stress values ​​as the third objective function.

[0029] Furthermore, the formula for calculating the fault friction coefficient is as follows:

[0030] ;

[0031] in, This represents the maximum measured structural stress value. This represents the minimum measured structural stress value. Indicates pore pressure, This represents the fault friction coefficient.

[0032] Furthermore, the third objective function is as follows:

[0033] ;

[0034] in, This represents the third objective function. Indicates the number of ground stress measuring points. This represents 6 stress components. Indicates the first The first geostress measuring point Measured structural stress values ​​of each stress component Indicates the free item, Indicates the first The regression coefficients for each working condition Indicates the first The first geostress measuring point The stress component in the first... Simulated structural stress values ​​for each working condition Indicates the number of operating conditions.

[0035] Furthermore, the method also includes:

[0036] Based on the tectonic stress values ​​obtained from the inversion calculation and the measured tectonic stress values, the complex correlation coefficient test, F test, and t test are performed respectively, and the error of the stress components of all geostress measuring points is calculated. If the verification fails or the error is greater than the error threshold, the stress field boundary conditions are adjusted and the tectonic stress field inversion is performed again.

[0037] Secondly, the present invention provides a rock mass initial geostress field inversion system, the system comprising:

[0038] The data collection and modeling unit is used to acquire basic data and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured in-situ stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability.

[0039] The temperature stress field inversion unit is used to construct a three-dimensional temperature field model based on the three-dimensional geological model and the corresponding thermal conductivity, combined with the defined temperature field boundary conditions. The unit uses the least squares method to take the sum of the squares of the differences between the measured temperature value and the simulated temperature value as the first objective function to perform temperature field inversion, obtain the temperature distribution of the three-dimensional temperature field model, and calculate the initial temperature stress field based on the temperature distribution and the temperature gradient method.

[0040] The seepage stress field inversion unit is used to construct a three-dimensional seepage field model based on the three-dimensional geological model and the corresponding permeability coefficient, combined with the defined seepage field boundary conditions. The seepage field is inverted by using the sum of squares of the differences between the measured hydraulic head and the simulated hydraulic head as the second objective function through the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method.

[0041] The structural stress extraction unit is used to subtract the temperature stress component corresponding to the initial temperature stress field from the measured ground stress value at each stress measuring point, and to subtract the seepage stress component corresponding to the initial seepage stress field, so as to obtain the measured structural stress value of the rock mass caused by tectonic activity at each measuring point.

[0042] The in-situ stress field inversion unit is used to invert the tectonic stress field based on the measured tectonic stress value and the least squares method. The inverted tectonic stress field is superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial in-situ stress field of the rock mass in the engineering area.

[0043] The beneficial effects of the present invention are as follows: The rock mass initial geostress field inversion method and system provided by the present invention can remove the influence of temperature field and seepage field on measured geostress by inverting and calculating temperature field and seepage field, eliminate non-tectonic stress interference, and thus accurately invert tectonic stress field. The total initial geostress field is obtained by coupling and superimposing temperature stress field, seepage stress field and tectonic stress field, thereby improving the inversion accuracy of rock mass initial geostress field. Attached Figure Description

[0044] Figure 1 A schematic flowchart of the rock mass initial geostress field inversion method provided for the embodiment;

[0045] Figure 2 A schematic diagram of the temperature field boundary conditions provided for an embodiment;

[0046] Figure 3 A schematic diagram of the seepage field boundary conditions provided for the embodiment;

[0047] Figure 4 A schematic diagram of the stress field boundary conditions provided for the embodiment;

[0048] Figure 5 A schematic diagram of the structure of the rock mass initial geostress field inversion system provided in the example. Detailed Implementation

[0049] To enable those skilled in the art to better understand the present invention, the technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings.

[0050] In some of the processes described in the specification and accompanying drawings of this invention, multiple operations are included that appear in a specific order. However, it should be clearly understood that these operations may not be executed in the order they appear herein, or may be executed in parallel. The sequence numbers of the operations are merely used to distinguish different operations and do not themselves represent any execution order. Furthermore, these processes may include more or fewer operations, and these operations may be executed sequentially or in parallel.

[0051] The technical solution of this invention is applicable to application scenarios that require initial geostress inversion of rock masses, especially complex geological environments with high rock temperature, high water pressure, and high geostress.

[0052] Current methods for inverting geostress fields typically rely on measured geostress directly, neglecting the effects of thermal stress caused by temperature gradients and fluid-structure interaction stress generated by seepage, resulting in low inversion accuracy.

[0053] Based on this, the technical solution of the present invention is proposed. In the present invention, firstly, basic data and measured data of the engineering area are collected, and a three-dimensional geological model is constructed to provide a spatial framework for subsequent inversion; then, based on the established three-dimensional geological model and parameters, a three-dimensional temperature field model is constructed in combination with temperature field boundary conditions, and the temperature distribution is inverted in combination with measured temperature data, thereby calculating the stress field caused by temperature; similarly, based on the established three-dimensional geological model and parameters, a three-dimensional seepage field model is constructed in combination with seepage field boundary conditions, and the seepage distribution is inverted in combination with measured head data, thereby calculating the stress field caused by seepage; then, at the geostress measuring point, the measured geostress is subtracted from the calculated corresponding temperature stress component and seepage stress component to obtain the measured tectonic stress value caused by tectonic activity; finally, using the measured tectonic stress value, the distribution of the tectonic stress field is inverted through regression analysis, and the tectonic stress field is superimposed with the initial temperature stress field and the initial seepage stress field to obtain the complete initial geostress field. In the above scheme, because the measured geostress values ​​were stripped of tectonic stress before geostress inversion, and pure tectonic stress was used for inversion, and then temperature stress and seepage stress were superimposed after inversion, the influence of thermal stress caused by temperature gradient and fluid-structure coupling stress generated by seepage was eliminated, thus improving the accuracy of geostress inversion.

[0054] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0055] Figure 1 A flowchart illustrating a method for inverting the initial geostress field of a rock mass is shown. Please refer to [link / reference]. Figure 1 The method includes the following steps:

[0056] Step 1, Data Collection and Modeling: Obtain basic and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured ground stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability.

[0057] In practical applications, a three-dimensional geological model is constructed based on collected foundational data. This foundational data includes topographic and geological information such as topographic geology, lithology, structure, and faults, as well as geological structure images including planar, longitudinal, and cross-sectional views. The three-dimensional geological model provides a spatial framework for subsequent inversion by dividing regions and assigning corresponding physical parameters (including thermal conductivity and permeability). Simultaneously, measured data are prepared as the raw input data for the inversion of temperature, seepage, and geostress fields.

[0058] Step 2, Temperature Stress Field Inversion: Based on the three-dimensional geological model and the corresponding thermal conductivity, a three-dimensional temperature field model is constructed in combination with the defined temperature field boundary conditions. The sum of squares of the differences between the measured temperature value and the simulated temperature value is used as the first objective function to perform temperature field inversion using the least squares method to obtain the temperature distribution of the three-dimensional temperature field model. The initial temperature stress field is calculated based on the temperature distribution and the temperature gradient method.

[0059] In practical applications, a three-dimensional temperature field model is constructed based on the three-dimensional geological model and thermal conductivity established in step 1, combined with the temperature field boundary conditions. Please refer to... Figure 2 In this embodiment, the temperature field boundary conditions include a surface temperature boundary, a surrounding insulating boundary, and a bottom unknown temperature boundary. The surface temperature boundary is determined based on the average air temperature at the corresponding altitude. The surrounding insulating boundary is an adiabatic boundary, and the bottom unknown boundary is an adjustable boundary, defined according to geological structure and surrounding rock characteristics. Subsequently, measured temperature data from the on-site rock mass are introduced, and the least squares method is used for inversion to determine the spatial distribution of temperature. If the temperature data revealed on-site does not match the model, the temperature field boundary conditions are adjusted to correct the temperature field. Once the temperature field is verified, the initial temperature stress field within the engineering area can be calculated using the temperature gradient method. The output of this step (temperature stress field) not only describes the contribution of thermal effects to stress but also provides crucial input for subsequent stress stripping.

[0060] In this embodiment, the first objective function is as follows:

[0061] ;

[0062] in, Denotes the first objective function. Indicates the first Thermal conductivity at each temperature measuring point Indicates the number of temperature measuring points. Indicates the first Thermal conductivity weighting coefficient for each temperature measuring point Indicates the first Simulated temperature values ​​at each temperature measuring point Indicates the first The measured temperature values ​​at each temperature measuring point.

[0063] When the initial temperature stress field is obtained based on the temperature distribution and the temperature gradient method, the temperature stress calculation formula is as follows:

[0064] ;

[0065] in, This indicates the temperature stress in the rock mass. Represents the geothermal gradient. Indicates the coefficient of thermal expansion of the rock mass. Indicates the elastic modulus. Indicates burial depth.

[0066] Step 3, seepage stress field inversion: Based on the three-dimensional geological model and the corresponding permeability coefficient, a three-dimensional seepage field model is constructed in combination with the defined seepage field boundary conditions. The sum of the squares of the differences between the measured hydraulic head and the simulated hydraulic head is used as the second objective function to perform seepage field inversion using the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method.

[0067] In practical applications, a three-dimensional seepage field model is constructed based on the three-dimensional geological model and permeability coefficient established in step 1, combined with the seepage field boundary conditions. Please refer to... Figure 3 In this embodiment, the seepage boundary conditions include a constant water level boundary, a constant water level recharge boundary, and a permeable boundary. The constant water level boundary is a recharged underground river, the constant water level recharge boundary is the river channel water level, and the permeable boundary is the on-site measured water level. Figure 3 middle, , , River water level; , , The water level is unknown, and the water level line represents a typical mountain ridge. , , The model uses groundwater depth values ​​around the perimeter of the model, with water levels at other locations obtained through topographic interpolation. Subsequently, measured hydraulic head data from the on-site rock mass are incorporated, and the least squares method is used for inversion to determine the spatial distribution of the hydraulic head. If the on-site hydraulic head data does not match the model, the seepage field boundary conditions are adjusted to correct the seepage field. Once the seepage field is verified, the initial seepage stress field within the engineering area can be calculated using the fluid-structure interaction method. The output of this step (seepage stress field) together with the temperature stress field from step 2 constitutes the non-tectonic stress components, which will be stripped away in the next step to isolate tectonic effects.

[0068] In this embodiment, the second objective function is as follows:

[0069] ;

[0070] in, Describes the second objective function. Indicates the first The permeability coefficient at each water head measuring point Indicates the number of head measurement points. Indicates the first Seepage weight coefficient at each head measuring point Indicates the first Simulated head values ​​at each head measuring point Indicates the first The measured head values ​​at each head measuring point.

[0071] In this embodiment, the initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method. Specifically, the seepage distribution is transformed into a corresponding mechanical effect distribution using the fluid-structure interaction module of ABAQUS, FLAC3D, or COMSOL to obtain the initial seepage stress field. By using the fluid-structure interaction module of commercial software, the seepage field (water pressure) is transformed into mechanical effects (stress), which is essentially a solution to the physical process of water-rock interaction. The software can automate the solution of complex partial differential equations, allowing engineers to focus only on geological modeling, parameter assignment, and result verification, thus improving the calculation efficiency of seepage stress.

[0072] Step 4: Extraction of tectonic stress: Subtract the temperature stress component corresponding to the initial temperature stress field from the measured ground stress value at each stress measuring point, and subtract the seepage stress component corresponding to the initial seepage stress field to obtain the measured tectonic stress value of the rock mass caused by tectonic activity at each measuring point.

[0073] This step is understood to be used to strip away tectonic stresses, isolating their influence. In practical applications, for each geostress measuring point, the temperature stress component calculated in step 2 and the seepage stress component calculated in step 3 are directly used. These components are subtracted from the measured geostress to obtain an equivalent measured tectonic stress value. This value represents the pure tectonic stress component after eliminating temperature and seepage interference. This step reveals hidden tectonic stress signals by removing known non-tectonic stresses, and its output (equivalent tectonic stress value) becomes the direct basis for inverting the tectonic stress field.

[0074] Step 5: Inversion of the geostress field: Based on the measured tectonic stress values, the tectonic stress field is inverted using the least squares method. The inverted tectonic stress field is then superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial geostress field of the rock mass in the engineering area.

[0075] Specifically, this step assumes that tectonic stress varies linearly with burial depth. The measured tectonic stress values ​​from multiple geostress measuring points obtained in step 4 are used as input data. The least squares method is employed for regression calculation to determine the regression coefficients reflecting the spatial distribution of the tectonic stress field. The regression results are used to calculate the initial tectonic stress field of the entire engineering area, thereby obtaining the initial tectonic stress portion of the rock mass after excluding the effects of temperature and seepage.

[0076] In this embodiment, the stress field inversion includes the following steps:

[0077] Step 51: Based on the three-dimensional geological model, establish a three-dimensional stress field model containing faults and determine the fault friction coefficient.

[0078] In practical applications, surfaces are generated through interpolation using SURFER software. The point cloud of these surfaces is then imported into RHINO software to create a 3D geological model. Faults and surrounding rock segmentation surfaces are formed by cutting. The mesh is generated using the GRIDDLE plugin and imported into FLAC3D software to create a 3D stress field model containing faults. Faults are established using INTERFACE elements and assigned a fault friction coefficient. The formula for calculating the fault friction coefficient is as follows:

[0079] ;

[0080] in, This represents the maximum measured structural stress value. This represents the minimum measured structural stress value. Indicates pore pressure, This represents the fault friction coefficient.

[0081] Step 52: Define the stress field boundary conditions for the three-dimensional stress field model and then simulate the stress. The stress field boundary conditions include applying gravitational acceleration throughout the domain and constructing unit normal stress in the X direction, unit normal stress in the Y direction, and shear stress in the XOY plane.

[0082] Please see Figure 4 By applying self-weight stress to simulate self-weight load, gravitational acceleration is applied. ; Structural stress is the unit structural stress in the X direction alone. Unit structural stress in the Y direction 1. Shear boundary in XOY plane (apply forced displacement: y=bcm in Y direction, x=acm in X direction) to simulate structural stress.

[0083] Step 53: Convert the NOW coordinates corresponding to the measured structural stress values ​​into XOY coordinates of the three-dimensional stress field model.

[0084] The coordinate transformation relationship of the measured structural stress values ​​is as follows:

[0085] ;

[0086] in, Represents the stress tensor components in NOW coordinates. Represents the stress tensor components in the XOY coordinates. and Represents the elements of the direction cosine matrix.

[0087] Step 54: Using the least squares method, the sum of the squares of the differences between the measured tectonic stress values ​​and the simulated tectonic stress values ​​is used as the third objective function to invert the tectonic stress field and obtain the tectonic stress field.

[0088] In this embodiment, the third objective function is as follows:

[0089] ;

[0090] in, This represents the third objective function. Indicates the number of ground stress measuring points. This represents 6 stress components. Indicates the first The first geostress measuring point Measured structural stress values ​​of each stress component Indicates the free item, Indicates the first The regression coefficients for each working condition Indicates the first The first geostress measuring point The stress component in the first... Simulated structural stress values ​​for each working condition Indicates the number of operating conditions.

[0091] In this embodiment, it also includes:

[0092] Step 55: Based on the tectonic stress values ​​obtained from the inversion calculation and the measured tectonic stress values, perform the complex correlation coefficient test, F test, and t test respectively, and calculate the error of the stress components of all geostress measuring points. If the verification fails or the error is greater than the error threshold, adjust the stress field boundary conditions and re-perform the tectonic stress field inversion.

[0093] Specifically, the regression effect is evaluated using methods such as the R-squared, F-test, and t-test. If the test fails (e.g., the R-value is too low), the stress field boundary conditions need to be adjusted and the three-dimensional geostress field model needs to be corrected. The regression process is repeated until the accuracy requirements are met. Simultaneously, if the error of the stress components at the geostress measuring points is less than or equal to the error threshold, the result is considered reliable; otherwise, the stress field boundary conditions are adjusted and the three-dimensional geostress field model is corrected, and the regression process is repeated until the requirements are met. The error threshold can be set according to the actual situation, such as 10%.

[0094] After obtaining the tectonic stress field through inversion, the tectonic stress field is superimposed with the initial temperature stress field and the initial seepage stress field to obtain the complete initial geostress field that takes into account tectonic stress, temperature stress and seepage stress.

[0095] In summary, the rock mass initial in-situ stress field inversion method provided in this embodiment has at least the following advantages:

[0096] 1. Improve inversion accuracy: This embodiment effectively eliminates the interference of these two environmental factors on tectonic stress inversion by accurately calculating and separating the influence of temperature stress and seepage stress on measured in-situ stress. This makes the tectonic stress field obtained based on measured data more accurate, thereby significantly improving the inversion accuracy of the entire initial in-situ stress field, which is especially important in complex environments such as high rock temperature and high water pressure.

[0097] 2. Distinguishing stress sources: This embodiment can decompose the total stress of the rock mass into tectonic stress, temperature stress, and seepage stress components, which helps to understand the contribution of different stress sources to the initial stress state of the rock mass and provides more refined stress information for engineering design, stability analysis, and disaster prediction.

[0098] 3. Wide range of applications: This embodiment is particularly suitable for complex geological environments such as high rock temperature, high water pressure, and high ground stress, making up for the shortcomings of traditional methods in these environments where the results are not good;

[0099] 4. Provides a more comprehensive initial geostress field: The final obtained initial geostress field of the rock mass is a superposition of tectonic stress, temperature stress and seepage stress, which more comprehensively reflects the initial stress state of the rock mass in a complex environment, and provides more realistic and reliable initial boundary conditions for subsequent engineering numerical simulations (such as excavation unloading analysis, support design, etc.).

[0100] 5. The method is logically clear and easy to implement: The complex total stress inversion is decomposed into independent temperature field and seepage field calculations, as well as tectonic stress inversion based on stripping stress. The steps are clear and easy to implement by combining with existing temperature field simulation, seepage field simulation and geostress inversion software platforms.

[0101] Based on the above technical solution, this embodiment also proposes an initial geostress field inversion system for rock masses. Please refer to [link to relevant documentation]. Figure 5 The system includes:

[0102] The data collection and modeling unit is used to acquire basic data and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured in-situ stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability.

[0103] The temperature stress field inversion unit is used to construct a three-dimensional temperature field model based on the three-dimensional geological model and the corresponding thermal conductivity, combined with the defined temperature field boundary conditions. The unit uses the least squares method to take the sum of the squares of the differences between the measured temperature value and the simulated temperature value as the first objective function to perform temperature field inversion, obtain the temperature distribution of the three-dimensional temperature field model, and calculate the initial temperature stress field based on the temperature distribution and the temperature gradient method.

[0104] The seepage stress field inversion unit is used to construct a three-dimensional seepage field model based on the three-dimensional geological model and the corresponding permeability coefficient, combined with the defined seepage field boundary conditions. The seepage field is inverted by using the sum of squares of the differences between the measured hydraulic head and the simulated hydraulic head as the second objective function through the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method.

[0105] The structural stress extraction unit is used to subtract the temperature stress component corresponding to the initial temperature stress field from the measured ground stress value at each stress measuring point, and to subtract the seepage stress component corresponding to the initial seepage stress field, so as to obtain the measured structural stress value of the rock mass caused by tectonic activity at each measuring point.

[0106] The in-situ stress field inversion unit is used to invert the tectonic stress field based on the measured tectonic stress value and the least squares method. The inverted tectonic stress field is superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial in-situ stress field of the rock mass in the engineering area.

[0107] It is understood that since the rock mass initial geostress field inversion system described in this embodiment is a system for implementing the rock mass initial geostress field inversion method described in the embodiment, the system disclosed in the embodiment is relatively simple to describe because it corresponds to the method disclosed in the embodiment. For relevant parts, please refer to the description of the method, and it will not be repeated here.

Claims

1. A method for inverting the initial geostress field of a rock mass, characterized in that, The method includes: Acquire basic and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured in-situ stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability. Based on the three-dimensional geological model and the corresponding thermal conductivity, a three-dimensional temperature field model is constructed in combination with the defined temperature field boundary conditions. The temperature field is inverted by using the sum of squares of the differences between the measured temperature value and the simulated temperature value as the first objective function through the least squares method to obtain the temperature distribution of the three-dimensional temperature field model. The initial temperature stress field is calculated based on the temperature distribution and the temperature gradient method. Based on the three-dimensional geological model and the corresponding permeability coefficient, a three-dimensional seepage field model is constructed in combination with the defined seepage field boundary conditions. The sum of squares of the differences between the measured hydraulic head and the simulated hydraulic head is used as the second objective function to perform seepage field inversion using the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method. Subtract the temperature stress component corresponding to the initial temperature stress field and the seepage stress component corresponding to the initial seepage stress field from the measured ground stress values ​​at each stress measuring point to obtain the measured tectonic stress values ​​of the rock mass caused by tectonic activity at each measuring point. Based on the measured tectonic stress values, the tectonic stress field is inverted using the least squares method. The inverted tectonic stress field is then superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial geostress field of the rock mass in the engineering area.

2. The method for inverting the initial geostress field of rock mass according to claim 1, characterized in that, The temperature field boundary conditions include a surface temperature boundary, a surrounding insulating boundary, and a bottom unknown temperature boundary. The surface temperature boundary is determined based on the average air temperature at the corresponding altitude. The surrounding insulating boundary is an adiabatic boundary, and the bottom unknown boundary is an adjustable boundary, which is divided according to the geological structure and surrounding rock characteristics. The seepage boundary conditions include a constant water level boundary, a constant water level recharge boundary, and a permeable boundary. The constant water level boundary is a recharged underground river, the constant water level recharge boundary is the river water level, and the permeable boundary is the on-site measured water level.

3. The method for inverting the initial geostress field of rock mass according to claim 1, characterized in that, The first objective function is as follows: ； in, Denotes the first objective function. Indicates the first Thermal conductivity at each temperature measuring point Indicates the number of temperature measuring points. Indicates the first Thermal conductivity weighting coefficient for each temperature measuring point Indicates the first Simulated temperature values ​​at each temperature measuring point Indicates the first Measured temperature values ​​at each temperature measuring point; The second objective function is as follows: ； in, This represents the second objective function. Indicates the first The permeability coefficient at each water head measuring point Indicates the number of head measurement points. Indicates the first Seepage weight coefficient at each head measuring point Indicates the first Simulated head values ​​at each head measuring point Indicates the first The measured head values ​​at each head measuring point.

4. The method for inverting the initial geostress field of rock mass according to claim 1, characterized in that, The formula for calculating the temperature stress of the initial temperature stress field is as follows: ； in, This indicates the temperature stress in the rock mass. Represents the geothermal gradient. Indicates the coefficient of thermal expansion of the rock mass. Indicates the elastic modulus. Indicates burial depth.

5. The method for inverting the initial geostress field of rock mass according to claim 1, characterized in that, The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method. Specifically, the seepage distribution is transformed into the corresponding mechanical effect distribution through the fluid-structure interaction module of ABAQUS, FLAC3D or COMSOL to obtain the initial seepage stress field.

6. The method for inverting the initial geostress field of rock mass according to claim 1, characterized in that, Based on the measured tectonic stress values, the tectonic stress field is inverted using the least squares method, including: Based on the aforementioned three-dimensional geological model, a three-dimensional stress field model containing faults is established, and the fault friction coefficient is determined. After defining the stress field boundary conditions for the three-dimensional stress field model, the stress is simulated and constructed. The stress field boundary conditions include applying gravitational acceleration throughout the domain and constructing unit normal stress in the X direction, unit normal stress in the Y direction, and shear stress in the XOY plane. The NOW coordinates corresponding to the measured structural stress values ​​are converted into XOY coordinates of a three-dimensional stress field model. The tectonic stress field is obtained by using the least squares method to invert the tectonic stress field by taking the sum of the squares of the differences between the measured tectonic stress values ​​and the simulated tectonic stress values ​​as the third objective function.

7. The method for inverting the initial geostress field of rock mass according to claim 6, characterized in that, The formula for calculating the fault friction coefficient is as follows: ； in, This represents the maximum measured structural stress value. This represents the minimum measured structural stress value. Indicates pore pressure, This represents the fault friction coefficient.

8. The method for inverting the initial geostress field of rock mass according to claim 6, characterized in that, The third objective function is as follows: ； in, This represents the third objective function. Indicates the number of ground stress measuring points. This represents 6 stress components. Indicates the first The first geostress measuring point Measured structural stress values ​​of each stress component. Indicates the free item, Indicates the first The regression coefficients for each working condition Indicates the first The first geostress measuring point The stress component in the first... Simulated structural stress values ​​for each working condition Indicates the number of operating conditions.

9. The method for inverting the initial geostress field of rock mass according to claim 6, characterized in that, The method further includes: Based on the tectonic stress values ​​obtained from the inversion calculation and the measured tectonic stress values, the complex correlation coefficient test, F test, and t test are performed respectively, and the error of the stress components of all geostress measuring points is calculated. If the verification fails or the error is greater than the error threshold, the stress field boundary conditions are adjusted and the tectonic stress field inversion is performed again.

10. A rock mass initial geostress field inversion system, characterized in that, The system includes: The data collection and modeling unit is used to acquire basic data and measured data of the rock mass in the engineering area, construct a three-dimensional geological model based on the basic data, and assign corresponding physical parameters to the three-dimensional geological model. The basic data includes topographic geological data and geological structure images. The measured data includes measured temperature values, measured hydraulic head values, and measured in-situ stress values ​​at multiple measuring points. The physical parameters include thermal conductivity and permeability. The temperature stress field inversion unit is used to construct a three-dimensional temperature field model based on the three-dimensional geological model and the corresponding thermal conductivity, combined with the defined temperature field boundary conditions. The unit uses the least squares method to take the sum of the squares of the differences between the measured temperature value and the simulated temperature value as the first objective function to perform temperature field inversion, obtain the temperature distribution of the three-dimensional temperature field model, and calculate the initial temperature stress field based on the temperature distribution and the temperature gradient method. The seepage stress field inversion unit is used to construct a three-dimensional seepage field model based on the three-dimensional geological model and the corresponding permeability coefficient, combined with the defined seepage field boundary conditions. The seepage field is inverted by using the sum of squares of the differences between the measured hydraulic head and the simulated hydraulic head as the second objective function through the least squares method to obtain the seepage distribution of the three-dimensional seepage field model. The initial seepage stress field is calculated based on the seepage distribution and the fluid-structure interaction method. The structural stress extraction unit is used to subtract the temperature stress component corresponding to the initial temperature stress field from the measured ground stress value at each stress measuring point, and to subtract the seepage stress component corresponding to the initial seepage stress field, so as to obtain the measured structural stress value of the rock mass caused by tectonic activity at each measuring point. The in-situ stress field inversion unit is used to invert the tectonic stress field based on the measured tectonic stress value and the least squares method. The inverted tectonic stress field is superimposed with the initial temperature stress field and the initial seepage stress field to obtain the initial in-situ stress field of the rock mass in the engineering area.

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