A method for visualizing three-dimensional geostress field under complex geological conditions

Abstract

The present invention discloses a method for visualizing and constructing a three-dimensional geostress field under complex geological structural conditions, and the present invention relates to the technical field of geostress field analysis. The method comprises: obtaining characteristic data such as density and Poisson's ratio of surface rock and soil layers, sedimentary layers, parent material layers and bedrock layers by drilling in the area to be analyzed. Applying seismic waves and using seismic detectors to obtain the longitudinal and transverse wave velocities of each rock and soil layer, and calculating the shear modulus and bulk modulus. Establishing a finite element model to analyze the strain tensor under load, and calculating the stress tensor in combination with the modulus. Calculating the pore water pressure, and correcting the stress tensor to obtain the effective stress. Obtaining fault characteristic information through a geological report, and further correcting the stress tensor to obtain accurate effective stress. Constructing a three-dimensional geological model and dividing the grid, mapping the accurate effective stress to each grid unit, and using visualization software to complete the visualization construction of the geostress field. Effectively improving safety and economic benefits, and reducing risks caused by geological factors.

Description

Technical Field

[0001] The present invention relates to the technical field of geostress field analysis, and in particular to a method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions. Background Art

[0002] Accurate calculation and evaluation of geostress fields are key factors in solving the major challenges associated with the design, construction and operation of underground engineering projects (such as mining, civil and petroleum engineering). At the same time, accurate understanding of the distribution law of geostress fields is also indispensable for geoscience research such as plate driving mechanism, tectonic evolution, earthquake mechanism and prediction, fault activity, etc. With the vigorous development of underground projects such as exploration and development of underground energy resources, nuclear waste disposal and geological storage of carbon dioxide, complex geological structural conditions have brought great challenges to the analysis of geostress. Using geostress measurement methods such as stress relief method, hydraulic fracturing method, borehole collapse method and geophysical method, the measured stress data are often highly random, highly discrete, and have a small sample size, which cannot fully and accurately reflect the complex three-dimensional geostress state of a certain area, especially in the case of alternating multiple layers of soil and rock. These methods can usually only provide local "point" stress information, lack a full understanding of the geostress field of the entire region, and are difficult to meet the needs of underground engineering construction and geoscience research.

[0003] There are many deficiencies in existing technical means when dealing with complex geological structural features. First, the influence of the physical properties of the strata (such as density, Poisson's ratio, etc.) on the wave velocity has not been fully considered. The propagation speed of seismic waves in different rock and soil layers varies depending on the physical properties of each layer. If there is a lack of accurate characteristic data, the shear modulus and bulk modulus of each rock and soil layer cannot be effectively calculated, but this calculation is crucial to understanding the deformation and stress distribution of the rock strata under external loads. Secondly, traditional finite element analysis methods often rely on simplified assumptions and fail to fully consider the interaction between rock and soil layers and the influence of pore water pressure on the distribution state of ground stress. Pore water pressure plays an important role in many geological environments. Its changes directly affect the effective stress of the rock mass, and then affect the strength and deformation characteristics of the rock mass.

[0004] In addition, the existence of geological structures such as faults makes the construction of the geostress field more complicated. Fault characteristics, such as dip, strike angle, length, depth and width, will significantly affect the stress distribution in the surrounding rock and soil layers. The existing technology does not analyze the impact of faults in depth, resulting in an incomplete and inaccurate understanding of the stress field under complex geological conditions. The above factors together lead to huge challenges in the visualization and accurate construction of the geostress field under actual geological conditions, and an innovative technical method is urgently needed to solve these problems.

[0005] In the existing technology, the publication number CN118260982A discloses a method and device for determining the characteristics of a three-dimensional geostress field, including the following steps: collecting regional geological data and drilling data of the research area; constructing a three-dimensional geological model of the research area according to the regional geological data, drilling data and three-dimensional visualization modeling technology; establishing a three-dimensional rock mechanics parameter model of the research area corresponding to the three-dimensional geological model according to the drilling data; determining the model boundary conditions according to the simulated geostress values ​​of the three-dimensional geological model at the preset well points and the measured geostress values ​​of the well points; performing finite element simulation calculations based on the three-dimensional geological model, the three-dimensional rock mechanics parameter model and the model boundary conditions to obtain the geostress field characteristics of the research area. However, in this scheme, the construction of a three-dimensional geological model and a three-dimensional rock mechanics parameter model requires comprehensive consideration of multiple factors, such as the heterogeneity of rock and soil layers, the interaction between layers, pore water pressure, etc. These factors were not fully considered during the model construction process, resulting in an over-simplification of the model, which could not truly reflect the actual geological structure. In addition, the three-dimensional modeling and calculation have problems such as too many iterations, slow convergence speed, and easy to fall into local minimum values. Moreover, the dynamic factors and nonlinear behavior of the rock mass are not fully considered, which limits the accuracy of the stress field analysis and reduces the accuracy and effectiveness of the three-dimensional geostress field characteristic determination method.

[0006] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute the prior art that is already known to one of ordinary skill in the art. Summary of the invention

[0007] The purpose of the present invention is to provide a method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions, comprising the following specific steps:

[0010] Acquire characteristic data of different rock and soil layers in the area to be analyzed, wherein the different rock and soil layers include a surface rock and soil layer, a sedimentary layer, a parent material layer and a bedrock layer, and the characteristic data of the rock and soil layers include different densities and Poisson's ratios of the rock and soil layers;

[0011] Apply seismic waves to the area to be analyzed, and receive the reflected waves through the seismic detector to obtain the velocity of the longitudinal and transverse waves of each rock and soil layer, and calculate its shear modulus and bulk modulus based on the characteristic data of the rock and soil layer and the velocity data of the longitudinal and transverse waves of each layer;

[0012] Establish a finite element model of rock and soil layer displacement, set the load mass on the ground, analyze the strain tensor of each rock and soil layer under the set load mass through the finite element model of rock and soil layer displacement, and calculate the stress tensor of each layer based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer;

[0013] Based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer.

[0014] By conducting geological surveys on the area to be analyzed, fault characteristic information of each rock and soil layer is obtained, and based on the acquired fault characteristic information of each rock and soil layer, the effective stress tensor of each layer is corrected to obtain the accurate effective stress tensor of each layer under the geological conditions, wherein the fault characteristic information of the rock and soil layer includes the dip angle of the fault, the strike angle of the fault, the length of the fault, the depth of the fault and the width of the fault;

[0015] Based on the accurate effective stress tensors of each rock and soil layer, a three-dimensional geological model containing each rock and soil layer is constructed. The three-dimensional geological model is divided into multiple grid units, each grid unit corresponds to an accurate effective stress tensor, and the accurate effective stress tensor is mapped to each grid unit of the three-dimensional model using visualization software to complete the construction of a visualized three-dimensional geostress field.

[0016] Furthermore, based on the existing geological map and historical data, the drilling location is selected, the drilling is carried out according to the preset depth, and the sampling is carried out in each rock and soil layer to obtain the characteristic data of the corresponding rock and soil layer, wherein the different densities and Poisson's ratios of each rock and soil layer are measured by indoor experiments. The different rock and soil layers include the surface rock and soil layer and the sedimentary layer, the parent material layer and the bedrock layer, wherein the specific division logic is: the depth range is The rock and soil layer at the depth is marked as the surface rock and soil layer, and the depth range is The rock and soil layer at the location is marked as the sedimentary layer, and the depth range is The rock and soil layer at the depth is marked as the parent material layer, and the depth range is The rock and soil layer at the location is calibrated as the bedrock layer. Multiple sampling is carried out in each rock and soil layer by drilling, and the density and Poisson's ratio of the samples are determined experimentally. The mean density and Poisson's ratio of the samples in the same rock and soil layer are taken as the rock and soil layer density and Poisson's ratio of the rock and soil layer, respectively.

[0017] Furthermore, seismic waves are applied to the area to be analyzed, and the reflected waves are received by the seismic detector. The shear modulus and bulk modulus of each layer are calculated based on the characteristic data of the rock and soil layers and the velocity data of the longitudinal and shear waves of each rock and soil layer. The formulas for calculating the shear modulus and bulk modulus are:

[0018] ;

[0019] ;

[0020] In the formula, and Respectively Shear modulus and bulk modulus of the soil layer, For the The shear wave velocity of the rock and soil layer, For the The density of the rock layer, For the The longitudinal wave velocity of the rock and soil layer, For the Poisson's ratio of rock and soil layers.

[0021] Furthermore, the strain tensor of each rock and soil layer under the set load mass is analyzed by the rock and soil layer displacement finite element model. The logic for determining the strain tensor of each rock and soil layer is as follows: first, a three-dimensional geological coordinate system is established, with the vertical direction pointing to the sky as z The positive direction of the axis is perpendicular to z The horizontal line of the axis is x axis, and the north direction is x The positive direction of the axis is determined by the right-hand rule y Axis direction, thus establishing a three-dimensional geological coordinate system, in the established rock and soil layer displacement finite element model, input the characteristic data of each rock and soil layer, and at the same time set a number of unit nodes in each rock and soil layer, and record the position coordinates of each unit node, by applying the set load on the surface of the model, recording the position coordinates of each unit node after the load is applied, and obtaining the displacement information of the unit node, the displacement information includes the displacement component on the x-axis ,exist y Displacement component on the axis and in z Displacement component on the axis ;

[0022] The strain tensor of each rock and soil layer is calculated based on the displacement information of the unit node, where the strain tensor calculation is based on the formula:

[0023] ;

[0024] In the formula, For the i In the rock and soil layer, j The strain tensor of the element nodes is j is the index of the unit node, , is the total number of unit nodes set in each rock and soil layer, , and Respectively i In the rock and soil layer, j Unit nodes along x , y , z The normal strain in the axial direction is Indicates i In the rock and soil layer, j Unit nodes along x and y The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along x and z The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along y and z The shear strain in the direction of , , ; Strain tensor of soil layer The specific formula for calculating the elements in the formula is:

[0025] ;

[0026] ;

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] In the formula, represents the symbol for partial derivative, , and Respectively expressed in i The first layer of rock and soil j Unit nodes in x The displacement component on the axis, y The displacement components on the axis and z The displacement component on the axis.

[0032] Furthermore, the stress tensor of each rock and soil layer is calculated based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer, wherein the formula for calculating the stress tensor of the rock and soil layer is:

[0033] ;

[0034] In the formula, For the i The first layer of rock and soil j The stress tensor at each element node is represents the trace of the strain tensor, i.e., the sum of the diagonal elements of the strain tensor, Represents a 3×3 identity matrix in three-dimensional space.

[0035] Furthermore, based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated, wherein the formula for calculating the pore water head data of each rock and soil layer is:

[0036] ;

[0037] In the formula, is the permeability coefficient, Indicates water head, is the water storage coefficient, represents a vector operator, represents the gradient of the water head, represents the divergence of the flow;

[0038] By solving the formula, the pore water head data of each rock and soil layer is obtained. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The formula for calculating the pore water pressure is:

[0039] ;

[0040] In the formula, For the i Soil pore saturation of the rock layer, For the i The pressure of the gas in the soil pores of the rock layer, For the i The pore water pressure of the rock and soil layers, is the unit weight of water, is the height of the pore;

[0041] The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer. The formula for calculating the effective stress tensor of each rock and soil layer is:

[0042] ;

[0043] In the formula, For the i The first layer of rock and soil jThe effective stress tensor at each element node.

[0044] Furthermore, based on the acquired fault characteristic information of each rock and soil layer, the effective stress tensor of each rock and soil layer is corrected to obtain the accurate effective stress tensor of each rock and soil layer under the geological conditions, wherein the formula for calculating the accurate effective stress tensor is:

[0045] ;

[0046] In the formula, For the i The first layer of rock and soil j The exact effective stress tensor at each element node, is the adjustment item for geological conditions, among which the adjustment item for geological conditions The specific formula is:

[0047] ;

[0048] In the formula, is the fault dip, is the strike angle of the fault, represents the length of the fault, is the depth of the fault, is the width of the fault, Indicates the reference feature width.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] First, by obtaining the drilling data of the area to be tested, especially the physical property data of different rock and soil layers, such as density, Poisson's ratio, etc., combined with the propagation characteristics of seismic waves, the longitudinal and transverse wave velocities of each rock and soil layer can be obtained. This process not only improves the understanding of the physical properties of the rock and soil layer, but also lays a solid foundation for the subsequent calculation of the shear modulus and bulk modulus. Through this method, a comprehensive analysis of complex strata can be achieved to ensure that the actual characteristics of each rock and soil layer are taken into account when calculating stress. Secondly, based on the established rock and soil layer displacement finite element model, after applying external loads, the strain tensor of each rock and soil layer can be analyzed in detail, and the stress tensor can be calculated accordingly. The real behavior of the rock and soil layer under the action of external loads is simulated, and the interaction between the rock and soil layers can be effectively identified. In particular, by combining the fluid flow equation of Darcy's law, the influence of pore water pressure on the stress state is calculated, and a more accurate effective stress tensor can be obtained. The assessment accuracy of the stress state of the rock and soil layer is improved. Moreover, by further correcting the effective stress tensor of each rock and soil layer, considering the fault characteristic information provided in the geological report, an accurate analysis of the stress state under complex geological conditions is achieved. Finally, based on the accurate effective stress tensors of each rock and soil layer, the constructed three-dimensional geological model is divided into small grids, and the effective stress tensors are mapped to each grid unit of the model through visualization software. This visualization process allows the complex stress distribution to be presented intuitively, which not only facilitates on-site evaluation and design decisions of geotechnical engineering, improves safety and economic benefits, reduces the risk of disasters caused by geological factors, but also provides more detailed geological information for earth science research. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the overall method flow of the present invention;

[0052] Figure 2 A schematic diagram of a process for calculating shear modulus and bulk modulus according to the present invention;

[0053] Figure 3 It is a schematic diagram of the process of calculating the stress tensor of each rock and soil layer in the present invention. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0055] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0056] Example:

[0057] See also Figure 1 , the present invention provides a technical solution:

[0058] A method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions, specifically comprising:

[0059] Step 1: Acquire characteristic data of different rock and soil layers in the area to be analyzed, wherein the different rock and soil layers include a surface rock and soil layer, a sedimentary layer, a parent material layer and a bedrock layer, and the characteristic data of the rock and soil layers include different rock and soil layer densities and Poisson's ratios of the rock and soil layers;

[0060] Based on the existing geological map and historical data, the drilling location is selected, and drilling is carried out according to the preset depth. Samples are taken in each rock and soil layer to obtain the characteristic data of the corresponding rock and soil layer. The density and Poisson's ratio of different rock and soil layers are determined experimentally. The different rock and soil layers include the surface rock and soil layer, the sedimentary layer, the parent material layer and the bedrock layer. The specific division logic is: the depth range is within The rock and soil layer at the depth is marked as the surface rock and soil layer, and the depth range is The rock and soil layer at the location is marked as the sedimentary layer, and the depth range is The rock and soil layer at the depth is marked as the parent material layer, and the depth range is The rock layer at the bottom is marked as the bedrock layer. The division of each rock layer varies due to different terrain and geological structures. Here we only give a general range division method. Multiple sampling is carried out in each rock layer through drilling, and the density and Poisson's ratio of the samples are measured experimentally. The mean density and Poisson's ratio of the samples in the same rock layer are used as the rock layer density and Poisson's ratio of the rock layer, respectively.

[0061] The density and Poisson's ratio of different rock and soil layers are determined experimentally. Specifically, suitable drilling equipment (such as mechanical drilling rigs or manual drilling) is selected for on-site operations. Rotary drilling or impact drilling is usually selected. Drilling is carried out according to the pre-set depth, and the parent material layer or bedrock layer is reached as much as possible. Soil samples of each rock and soil layer are collected and the density of the rock and soil layer is calculated using the drying method or the Archimedean method. The saturated soil samples are subjected to triaxial compression tests in the laboratory, and the relationship between strain and stress is recorded to calculate the Poisson's ratio.

[0062] The surface rock and soil layer usually includes topsoil, humus soil, etc., and the density and Poisson's ratio are usually low. Sedimentary layer: usually includes clay, sand, sandstone, etc. This layer contains a large amount of soil and rock formed by sedimentation, which may include sediments of different particle sizes. The density and Poisson's ratio are between the surface layer and the parent material layer. Parent material layer: usually an unconsolidated rock and soil layer, commonly found deep underground, may contain uncompacted sediments or rock fragments, with a high density, and the Poisson's ratio depends on the actual soil quality. Bedrock layer: usually hard rock, a hard rock layer, usually consolidated rock, such as granite, basalt, limestone, etc. The density and Poisson's ratio are generally high.

[0063] Step 2: Apply seismic waves to the area to be analyzed, and receive the reflected waves through the seismic detector to obtain the velocity of the longitudinal and transverse waves of each rock and soil layer, and calculate the shear modulus and bulk modulus of each layer based on the characteristic data of the rock and soil layer and the velocity data of the longitudinal and transverse waves of each rock and soil layer;

[0064] The specific scheme for receiving the reflected waves by the seismic detector to obtain the velocity of the longitudinal and transverse waves of each rock and soil layer is as follows: by applying seismic waves and recording the arrival time of the reflected waves, the reflection method can be used to estimate the velocity of each rock and soil layer. The relationship between reflection time, layer thickness and wave velocity can be expressed by the following formula:

[0065] ;

[0066] In the formula, is the arrival time of the reflected wave, is the thickness of the rock layer, is the shear wave velocity of the rock and soil layer. The calculation of the longitudinal wave velocity of the rock and soil layer is the same.

[0067] Seismic waves are applied to the area to be analyzed, and the reflected waves are received by the seismic detector. The shear modulus and bulk modulus of each layer are calculated based on the characteristic data of the rock and soil layers and the velocity data of the longitudinal and shear waves of each rock and soil layer. The formulas for calculating the shear modulus and bulk modulus are:

[0068] ;

[0069] ;

[0070] In the formula, and Respectively Shear modulus and bulk modulus of the soil layer, For the The shear wave velocity of the rock and soil layer, For the The density of the rock layer, For the The longitudinal wave velocity of the rock and soil layer, For the Poisson's ratio of rock and soil layers.

[0071] Step 3: Establish a finite element model of rock and soil layer displacement, set the load mass on the ground, analyze the strain tensor of each rock and soil layer under the set load mass through the finite element model of rock and soil layer displacement, and calculate the stress tensor of each rock and soil layer based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer;

[0072] In the selected finite element software, you first need to create a geometric model of the geotechnical layer and define the material properties of the model, such as density, shear modulus, and bulk modulus. Fixed boundary conditions mean that no displacement or rotation of the nodes is allowed on the boundary. In the geotechnical layer model, fixed boundary conditions (such as no displacement) are usually applied at the bottom to simulate the support of the foundation or soil, and the sides can use free boundaries or apply constraints. Apply loads on the ground, which can be set as concentrated forces or uniformly distributed loads. Define the load size and application location according to the engineering requirements, and export the results to external files (such as CSV, TXT, etc.) according to the output of the model for further processing and analysis. Make sure that the exported data includes the node displacement information of each unit.

[0073] The strain tensor of each rock and soil layer under the set load mass is analyzed by the rock and soil layer displacement finite element model. The logic for determining the strain tensor of each rock and soil layer is as follows: first, a three-dimensional geological coordinate system is established, with the vertical direction pointing to the sky as the z The positive direction of the axis is perpendicular to z The horizontal line of the axis is x axis, and the north direction is x The positive direction of the axis is determined by the right-hand rule y Axis direction, thus establishing a three-dimensional geological coordinate system, in the established rock and soil layer displacement finite element model, input the characteristic data of each rock and soil layer, set unit nodes in each rock and soil layer, and record the position coordinates of each unit node, by applying the set load on the surface of the model, record the position coordinates of each unit node after the load is applied, and obtain the displacement information of the unit node, the displacement information includes the displacement component on the x-axis , the displacement component on the y-axis and in z Displacement component on the axis ;

[0074] The strain tensor of each rock and soil layer is calculated based on the displacement information of the unit node, where the strain tensor calculation is based on the formula:

[0075] ;

[0076] In the formula, For the i In the rock and soil layer, j The strain tensor of the element nodes is j is the index of the unit node, , is the total number of unit nodes set in each rock and soil layer, , and Respectively i In the rock and soil layer, j Unit nodes along x , y , z The normal strain in the axial direction is Indicates i In the rock and soil layer, j Unit nodes along x and y The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along x and z The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along y and z The shear strain in the direction of , , ; Strain tensor of soil layer The specific formula for calculating the elements in the formula is:

[0077] ;

[0078] ;

[0079] ;

[0080] ;

[0081] ;

[0082] ;

[0083] In the formula, represents the symbol for partial derivative, , and Respectively expressed in i The first layer of rock and soil j Unit nodes in x The displacement component on the axis, y The displacement components on the axis and z The displacement component on the axis.

[0084] The stress tensor of each rock and soil layer is calculated based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer. The formula for calculating the stress tensor of the rock and soil layer is:

[0085] ;

[0086] In the formula, For the i The first layer of rock and soil j The stress tensor at each element node is represents the trace of the strain tensor, i.e., the sum of the diagonal elements of the strain tensor, Represents a 3×3 identity matrix in three-dimensional space.

[0087] Step 4: Based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer;

[0088] Based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated. The formula for calculating the pore water head data of each rock and soil layer is:

[0089] ;

[0090] In the formula, is the permeability coefficient, Indicates water head, is the water storage coefficient, represents a vector operator, represents the gradient of the water head, represents the divergence of the flow;

[0091] By solving the formula, the pore water head data of each rock and soil layer is obtained. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The formula for calculating the pore water pressure is:

[0092] ;

[0093] In the formula, For the i Soil pore saturation of the rock layer, For the i The pressure of the gas in the soil pores of the rock layer, For the i The pore water pressure of the rock and soil layers, is the unit weight of water, is the height of the pore;

[0094] The soil pore saturation The calculation is based on the formula:

[0095] ;

[0096] In the formula, is the volume of water in the soil sample, is the total pore volume of the soil sample; the soil moisture content and porosity can be measured experimentally, and the volume of water in the soil sample and the total pore volume of the soil sample can be specifically calculated based on the soil moisture content and porosity. The specific calculation process belongs to conventional technical means and will not be elaborated here.

[0097] The pressure of the gas in the soil pores The calculation is based on the formula:

[0098] ;

[0099] In the formula, is the number of moles of gas, is the gas constant, generally 8.314 J / (mol·K), is the absolute temperature of the soil sample (in Kelvin). The mole number of the gas can be directly measured by the gas detector equipped in modern laboratories to determine the mole fraction or concentration of the gas, and then the mole number can be calculated based on the volume of the gas.

[0100] The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer. The formula for calculating the effective stress tensor of each rock and soil layer is:

[0101] ;

[0102] In the formula, For the i The first layer of rock and soil j The effective stress tensor at each element node.

[0103] Step 5: Obtain fault characteristic information of each rock and soil layer through the geological report of the area to be analyzed, and correct the effective stress tensor of each rock and soil layer based on the acquired fault characteristic information of each rock and soil layer to obtain the accurate effective stress tensor of each rock and soil layer under the geological conditions, wherein the fault characteristic information of the rock and soil layer includes the dip angle of the fault, the strike angle of the fault, the length of the fault, the depth of the fault and the width of the fault;

[0104] Based on the acquired fault characteristic information of each rock and soil layer, the effective stress tensor of each rock and soil layer is corrected to obtain the accurate effective stress tensor of each rock and soil layer under the geological conditions. The formula for calculating the accurate effective stress tensor is:

[0105] ;

[0106] In the formula, For the i The first layer of rock and soil j The exact effective stress tensor at each element node, is the adjustment item for geological conditions, among which the adjustment item for geological conditions The specific formula is:

[0107] ;

[0108] In the formula, is the fault dip, is the strike angle of the fault, represents the length of the fault, is the depth of the fault, is the width of the fault, Indicates the reference feature width.

[0109] Among them, the dip of the fault can be measured directly in the outcrop or exploration well using a geological compass to measure the inclination angle of the fault plane relative to the horizontal plane. The strike angle of the fault is measured by using a geological compass at the outcrop to measure the angle between the fault plane and the true north direction, or by using satellite images or high-resolution topographic maps to identify the direction of the fault line. The length of the fault, the depth of the fault and the width of the fault are determined through a geological report involving a detailed fault survey, which usually contains information on the length of the fault in the survey area, an estimate of the vertical extension of the fault and the width of the fault zone. In particular, if the fault has obvious outcrops on the surface, the report may describe its extension in detail.

[0110] The dip and strike angles of a fault determine the direction and tilt of the fault in three-dimensional space. The dip and strike angles affect how the fault plane redistributes the surrounding stress field. Generally speaking, the dip affects the position of the fault plane in the gravity field, while the strike angle determines the direction parallel to the surface. and It is to reflect the contribution of stress components projected in different directions to the total stress field.

[0111] The length and depth of a fault determine its range of influence. Longer and deeper faults may affect a larger range of stress fields. Longer and deeper faults usually lead to stress redistribution and concentration over a larger range, through It is expressed in proportion, reflecting the influence of the geometric size of the fault on the local stress field.

[0112] Fault width refers to the thickness of the fault zone, which may affect its sliding behavior and energy release. A wider fault zone may reduce the stress concentration effect because the energy release is distributed over a wider area. An exponential decay function is used. to describe the nonlinear reduction in the effect of width on stress, since wider faults gradually reduce the effect.

[0113] Step 6: Based on the accurate effective stress tensors of each rock and soil layer, a three-dimensional geological model containing each rock and soil layer is constructed. The three-dimensional geological model is divided into multiple grid units, each grid unit corresponds to an accurate effective stress tensor, and the accurate effective stress tensor is mapped to each grid unit of the three-dimensional model using visualization software to complete the construction of a visualized three-dimensional geostress field.

[0114] Use geological modeling software (such as Petrel or Leapfrog Geo) to build a 3D geological model based on geological exploration data. This model should be refined to each rock and soil layer to ensure that the boundaries and thickness of each rock and soil layer are accurately reflected in the model. Import stratigraphic sections and drillhole data, use contour lines and fault planes to construct 3D stratigraphic boundaries, and generate a comprehensive 3D geological model based on stratigraphic boundaries.

[0115] The 3D geological model is divided into multiple grid cells using the finite difference or finite element method. Unstructured grid division technology is used to adapt to complex geological conditions, and the grid is refined at the interface between faults and rock and soil layers to capture stress concentration phenomena.

[0116] Map the collected precise effective stress tensors of each unit node of each geotechnical layer to the corresponding grid unit one by one. Use bilinear or cubic interpolation methods to map discrete stress data to grid nodes. For each grid unit, assign the appropriate effective stress tensor to the unit according to the geological unit to which it belongs. Use visualization software (such as ParaView or Tecplot) to visualize the three-dimensional geostress field. Import the meshing results and stress tensor data into the visualization software, render the three-dimensional model, and generate an interactive visualization image of the geostress field.

[0117] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0118] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0119] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0120] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for visualizing a three-dimensional geostress field under complex geological conditions, characterized in that: Specifically include: Acquire characteristic data of different rock and soil layers in the area to be analyzed, wherein the different rock and soil layers include a surface rock and soil layer, a sedimentary layer, a parent material layer and a bedrock layer, and the characteristic data of the rock and soil layers include different rock and soil layer densities and Poisson's ratios of the rock and soil layers; Apply seismic waves to the area to be analyzed, and receive the reflected waves through the seismic detector to obtain the velocity of the longitudinal wave and the transverse wave of each rock and soil layer, and calculate the shear modulus and bulk modulus of each layer based on the characteristic data of the rock and soil layer and the velocity data of the longitudinal wave and the transverse wave of each rock and soil layer; Establish a finite element model of rock and soil layer displacement, set the load mass on the ground, analyze the strain tensor of each rock and soil layer under the set load mass through the finite element model of rock and soil layer displacement, and calculate the stress tensor of each rock and soil layer based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer; Based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer. By conducting geological survey on the area to be analyzed, fault characteristic information of each rock and soil layer is obtained, and based on the acquired fault characteristic information of each rock and soil layer, the effective stress tensor of each rock and soil layer is corrected to obtain the accurate effective stress tensor of each rock and soil layer under the geological conditions, wherein the fault characteristic information of the rock and soil layer includes the dip angle of the fault, the strike angle of the fault, the length of the fault, the depth of the fault and the width of the fault; Based on the accurate effective stress tensors of each rock and soil layer, a three-dimensional geological model containing each rock and soil layer is constructed. The three-dimensional geological model is divided into multiple grid units, each grid unit corresponds to an accurate effective stress tensor, and the accurate effective stress tensor is mapped to each grid unit of the three-dimensional model using visualization software to complete the construction of a visualized three-dimensional geostress field.

2. The method for visualizing a three-dimensional geostress field under complex geological structure conditions according to claim 1, characterized in that: Based on the existing geological map and historical data, the drilling location is selected, and drilling is carried out according to the preset depth. Samples are taken in each rock and soil layer to obtain the characteristic data of the corresponding rock and soil layer. The density and Poisson's ratio of different rock and soil layers are determined experimentally. The different rock and soil layers include the surface rock and soil layer, the sedimentary layer, the parent material layer and the bedrock layer. The specific division logic is: the depth range is within The rock and soil layer at the depth is marked as the surface rock and soil layer, and the depth range is The rock and soil layer at the location is marked as the sedimentary layer, and the depth range is The rock and soil layer at the depth is marked as the parent material layer, and the depth range is The rock and soil layer at the location is calibrated as the bedrock layer. Multiple sampling is carried out in each rock and soil layer by drilling, and the density and Poisson's ratio of the samples are determined experimentally. The mean density and Poisson's ratio of the samples in the same rock and soil layer are taken as the rock and soil layer density and Poisson's ratio of the rock and soil layer, respectively.

3. The method for visualizing a three-dimensional geostress field under complex geological structure conditions according to claim 1, characterized in that: Seismic waves are applied to the area to be analyzed, and the reflected waves are received by the seismic detector to obtain the velocity of the longitudinal and transverse waves of each rock and soil layer. The shear modulus and bulk modulus of each layer are calculated based on the characteristic data of the rock and soil layer and the velocity data of the longitudinal and transverse waves of each rock and soil layer. The formulas for calculating the shear modulus and bulk modulus are: ； ； In the formula, and Respectively Shear modulus and bulk modulus of the soil layer, For the The shear wave velocity of the rock and soil layer, For the The density of the rock layer, For the The longitudinal wave velocity of the rock and soil layer, For the Poisson's ratio of the rock and soil layers, is the index of the rock and soil layer, and .

4. The method for visualizing a three-dimensional geostress field under complex geological structure conditions according to claim 1, characterized in that: The strain tensor of each rock and soil layer under the set load mass is analyzed by the finite element model of rock and soil layer displacement. The logic for determining the strain tensor of each rock and soil layer is as follows: first, a three-dimensional geological coordinate system is established, with the z-axis pointing vertically to the sky as the positive direction and the z-axis pointing vertically to the sky as the positive direction. z The horizontal line of the axis is x axis, and the north direction is x The positive direction of the axis is determined by the right-hand rule y Axis direction, thus establishing a three-dimensional geological coordinate system, in the established rock and soil layer displacement finite element model, input the characteristic data of each rock and soil layer, and at the same time set a number of unit nodes in each rock and soil layer, and record the position coordinates of each unit node, by applying the set load on the surface of the model, recording the position coordinates of each unit node after the load is applied, and obtaining the displacement information of the unit node, the displacement information is included in x Displacement components on the axis ,exist y Displacement component on the axis and in z Displacement component on the axis ; The strain tensor of each rock and soil layer is calculated based on the displacement information of the unit node, where the strain tensor calculation is based on the formula: ； In the formula, For the i In the rock and soil layer, j The strain tensor of the element node, where j is the index of the element node, , is the total number of unit nodes set in each rock and soil layer, , and Respectively i In the rock and soil layer, j Unit nodes along x , y , z The normal strain in the axial direction is Indicates i In the rock and soil layer, j Unit nodes along x and y The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along x and z The shear strain in the direction Indicates i In the rock and soil layer, j Unit nodes along y and z The shear strain in the direction of , , ; Strain tensor of soil layer The specific formula for calculating the elements in the formula is: ； ； ； ； ； ； In the formula, represents the symbol for partial derivative, , and Respectively expressed in i The first layer of rock and soil j Unit nodes in x The displacement component on the axis, y The displacement components on the axis and z The displacement component on the axis.

5. The method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions according to claim 4, characterized in that: The stress tensor of each rock and soil layer is calculated based on the strain tensor combined with the shear modulus and bulk modulus of each rock and soil layer. The formula for calculating the stress tensor of the rock and soil layer is: ； In the formula, For the i The first layer of rock and soil j The stress tensor at each element node is represents the trace of the strain tensor, i.e., the sum of the diagonal elements of the strain tensor, Represents a 3×3 identity matrix in three-dimensional space.

6. The method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions according to claim 5, characterized in that: Based on the fluid flow equation of Darcy's law, the pore water head data of each rock and soil layer is calculated. The formula for calculating the pore water head data of each rock and soil layer is: ； In the formula, is the permeability coefficient, Indicates water head, is the water storage coefficient, represents a vector operator, represents the gradient of the water head, represents the divergence of the flow; By solving the formula, the pore water head data of each rock and soil layer is obtained. The pore water pressure is calculated based on the obtained water head data combined with the pore depth. The formula for calculating the pore water pressure is: ； In the formula, For the i Soil pore saturation of the rock layer, For the i The pressure of the gas in the soil pores of the rock layer, For the i The pore water pressure of the rock and soil layers, is the unit weight of water, is the height of the pore; The stress tensor of each rock and soil layer is corrected by the pore water pressure to obtain the effective stress tensor of each rock and soil layer. The formula for calculating the effective stress tensor of each rock and soil layer is: ； In the formula, For the i The first layer of rock and soil j The effective stress tensor at each element node.

7. The method for visualizing and constructing a three-dimensional geostress field under complex geological structure conditions according to claim 6, characterized in that: Based on the acquired fault characteristic information of each rock and soil layer, the effective stress tensor of each rock and soil layer is corrected to obtain the accurate effective stress tensor of each rock and soil layer under the geological conditions. The formula for calculating the accurate effective stress tensor is: ； In the formula, For the i The first layer of rock and soil j The exact effective stress tensor at each element node, is the adjustment item for geological conditions, among which the adjustment item for geological conditions The specific formula is: ； In the formula, is the fault dip, is the strike angle of the fault, represents the length of the fault, is the depth of the fault, is the width of the fault, Indicates the reference feature width.

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