Method and device for evaluating stability of tunnel face rock mass based on three-dimensional reconstruction

Abstract

The invention provides a tunnel face rock mass stability evaluation method and device based on three-dimensional reconstruction, and relates to the technical field of underground civil engineering, the tunnel face of a rock mass to be evaluated is divided through a three-dimensional grid, points to be measured are arranged in each evaluation area, the maximum horizontal stress, the minimum horizontal stress and the vertical stress of each point to be measured are calculated, and the stability of the tunnel face rock mass is evaluated. Calculating a stress value of a central point of a to-be-evaluated area according to the data, comprehensively generating primary rock stress of the to-be-evaluated area of the rock mass tunnel face, monitoring mining-induced stress, decomposing the stress into axial stress, circumferential stress and radial stress, further generating a stress threshold value, and calculating the stress value of the to-be-evaluated area by setting a safety threshold value and counting the number of the areas with the stress exceeding or not exceeding the threshold value. And calculating a safety coefficient, and judging whether the tunnel face rock mass is stable or not. Through the three-dimensional reconstruction technology and the stress contact method, accurate evaluation and safety judgment of the stability of the rock tunnel face are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of underground civil engineering, and in particular to a method and a device for evaluating the stability of a tunnel face rock mass based on three-dimensional reconstruction. Background Art

[0002] The stability assessment of the face rock mass is a crucial link in underground engineering, especially in the fields of tunnel excavation, mining and geological disaster prediction. Traditional rock mass stability assessment methods mostly rely on two-dimensional data and static analysis, which is difficult to fully reflect the complex mechanical behavior of the rock mass during the actual construction process. With the development of three-dimensional reconstruction technology and computer vision technology, combined with laser scanning, geological radar and other means, high-precision three-dimensional data of the face rock mass can be obtained. These data provide more accurate spatial information for rock mass stability assessment, enabling more comprehensive and detailed stress analysis, thereby effectively preventing safety hazards in construction.

[0003] In recent years, the application of 3D reconstruction technology in rock mass stability assessment has developed rapidly. By combining 3D modeling with mechanical analysis, researchers can more accurately simulate the stress distribution of the face rock mass and improve the prediction accuracy of rock mass stability. In addition, with the improvement of computing power and the development of sensing technology, real-time monitoring and data feedback mechanisms are gradually being applied to rock mass stability monitoring. Based on real-time analysis of mining stress sensor data, the stress state of the face rock mass can be dynamically evaluated, further improving the intelligence and precision of rock mass stability management.

[0004] In the current existing technologies, simplified models or traditional evaluation methods are usually relied on, which usually focus on single-dimensional stress analysis and calculation methods, and cannot accurately consider various stress states in complex geological conditions. In addition, the current existing technologies only focus on the stress conditions of local measuring points, ignoring the overall stress distribution of the region, and cannot accurately evaluate the stress conditions of the entire construction area; In addition, in traditional rock mass stability assessment, many methods can only assess the stability of local areas and cannot fully reflect the condition of the entire rock mass. This limitation makes it easy to ignore certain potential risk areas when assessing complex projects such as tunnels and mines. Traditional methods often assume uniform geological conditions in simplified models, but in actual projects, rock masses usually have a high degree of heterogeneity, such as different layers, structural surfaces, and fracture zones. This simplified model will lead to an inaccurate assessment of rock mass stability. Most existing technologies are based on static stress analysis and cannot monitor and evaluate the dynamic changes of stress in real time. Especially during the excavation of mines or tunnels, the stress state will fluctuate with the construction progress and changes in external conditions.

[0005] Therefore, it is necessary to provide a method and device for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction to solve the above problem.

[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 and device for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction, so as 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: The method for assessing the stability of the tunnel face rock mass based on three-dimensional reconstruction includes the following specific steps: Step 1: Obtain the three-dimensional data of the tunnel face of the rock mass to be evaluated, divide the tunnel face of the rock mass to be evaluated into three-dimensional grids based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be tested in the areas to be evaluated. Calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be tested based on the stress contact method; Step 2: Based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated are calculated, and the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated are used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; Step 3: According to the calculation, the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated are obtained, and the original rock stress of the area to be evaluated at the rock face is comprehensively generated; Step 4: A high-precision, long-term three-dimensional mining stress monitoring sensor is buried at the center point of the area to be evaluated on the face to collect the mining stress, and the mining stress is decomposed to generate axial stress, annular stress and radial stress. Based on the axial stress, annular stress and radial stress, the stress threshold of the area to be evaluated on the face is comprehensively generated; Step 5: Establish a safety threshold and count the number of areas to be assessed on the face where the original rock stress exceeds the stress threshold and where the original rock stress does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

[0009] Furthermore, the maximum horizontal stress, minimum horizontal stress and vertical stress of the test point are determined and calculated based on the stress contact method, and the method is as follows: Using hydraulic fracturing, drilling is performed at the interface between the excavation working surface and the unexcavated rock mass, i.e., the face of the rock mass. Water is injected into the borehole to increase the pressure in the hole until the rock mass breaks. The breaking pressure is related to the ground stress. The initial breaking pressure, pore pressure, and closing pressure of the rock at the test point are recorded to calculate the maximum horizontal stress, minimum horizontal stress, and vertical stress. The formula is: ; ; ; in, , , Respectively represent the maximum horizontal stress, minimum horizontal stress, and vertical stress of the test point. represents the initial fracture pressure of rock, Indicates the closing pressure, is the pore pressure, represents the surrounding rock density, Indicates the drilling depth, Indicates the deadweight of the rock.

[0010] Furthermore, based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated are calculated according to the following method: Determine the coordinates of the center point of the area to be evaluated and mark it as , the first The coordinates of the points to be measured are calibrated as , represents the index of the point to be measured in the area to be evaluated, and , is the number of test points in the area to be evaluated. Based on the stress data of each test point in the area to be evaluated and the distance between the test point and the center point, the maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated, and used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated. The maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated based on the following formula: ; ; ; ; in, , , Respectively at the center point The maximum horizontal stress, minimum horizontal stress and vertical stress at , , Respectively represent the points to be tested The maximum horizontal stress, minimum horizontal stress and vertical stress at Indicates the center point to The distance to the point to be measured.

[0011] Furthermore, according to the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated obtained by the calculation, the original rock stress of the area to be evaluated at the rock face is comprehensively generated, and the formula based on it is: ; in, Indicates the original rock stress in the area to be evaluated at the rock face. , , are the weight ratios corresponding to the maximum horizontal stress, minimum horizontal stress and vertical stress, respectively. , and satisfy .

[0012] Furthermore, the mining stress is decomposed to generate axial stress, hoop stress and radial stress according to the following method: The polar coordinate method is used to decompose the dynamic stress at the center point into Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to The dynamic stress of the plane, the axial stress is along the axis direction, directly using the measured perpendicular to Dynamic stress expression of plane; to calculate hoop stress and radial stress, the position angle must be determined and the comprehensive The shear stress on a plane is based on the formula: ; ; ; in, , , They represent axial stress, hoop stress, and radial stress respectively. , , Respectively expressed in Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in a plane, express Shear stress in the plane, Represents the position angle in polar coordinates.

[0013] Furthermore, based on the axial stress, hoop stress and radial stress, the stress threshold of the area to be evaluated on the tunnel face is comprehensively generated, and the formula is as follows: ; in, represents the stress threshold of the area to be evaluated on the tunnel face, , , Respectively represent the weight ratios of axial stress, hoop stress, and radial stress, and .

[0014] Furthermore, the number of areas to be evaluated in the tunnel face where the original rock stress exceeds the stress threshold and the number of areas where the original rock stress does not exceed the stress threshold are counted to calculate the safety factor. The method used is: The ratio of the total stress of the original rock that does not exceed the stress threshold to the total stress of the original rock that exceeds the stress threshold is used as the safety factor, and the formula is as follows: ; in, represents the safety factor, is the total stress of the original rock that does not exceed the stress threshold, is the total original rock stress exceeding the stress threshold.

[0015] Furthermore, a safety threshold is established to determine the relationship between the safety factor and the safety threshold, and to determine whether the rock mass at the tunnel face is stable. The logical formula is as follows: ; in, Indicates the logical value for judging whether the rock mass at the tunnel face is stable. When the safety factor is less than the established safety threshold, it means that the face rock mass is stable and the next excavation operation can be carried out; when When the safety factor is greater than or equal to the established safety threshold, it means that the rock mass at the tunnel face is unstable and the tunnel face of the rock mass needs to be reselected.

[0016] The present invention also provides a tunnel face rock mass stability assessment device based on three-dimensional reconstruction, the assessment device is used to execute the above-mentioned tunnel face rock mass stability assessment method based on three-dimensional reconstruction, comprising: A three-dimensional mesh division and stress calculation module, which is used to obtain three-dimensional data of the tunnel face of the rock mass to be evaluated, perform three-dimensional mesh division on the tunnel face of the rock mass to be evaluated based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be measured in the areas to be evaluated, and calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be measured based on the stress contact method; A stress center calculation module for the area to be evaluated, wherein the stress center calculation module for the area to be evaluated is used to calculate the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, and use the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; An original rock stress comprehensive generation module, the original rock stress comprehensive generation module is used to comprehensively generate the original rock stress of the area to be evaluated in the rock face according to the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated obtained by the calculation; A mining stress monitoring and decomposition module, wherein the mining stress monitoring and decomposition module is used to bury a high-precision, long-lasting three-way mining stress monitoring sensor at the center point of the area to be evaluated on the face to collect its mining stress, decompose the mining stress to generate axial stress, annular stress and radial stress, and comprehensively generate stress thresholds of the area to be evaluated on the face based on the axial stress, annular stress and radial stress; The stability determination module is used to establish a safety threshold and to count the number of areas to be evaluated on the face where the original rock stress exceeds the stress threshold and does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention can obtain more detailed stress distribution data by accurately dividing the three-dimensional grid of the rock face and setting multiple test points, thereby improving the accuracy of rock stability assessment. In addition, based on the stress contact method and dynamic stress monitoring technology, the present invention can reflect the stress changes of the rock mass during the excavation process in real time, provide timely and accurate data support for engineering construction, and greatly improve the scientificity and practicality of the assessment; Secondly, the present invention decomposes the mining stress to generate axial stress, annular stress and radial stress, and comprehensively generates stress thresholds, so that the rock stability assessment is more comprehensive and detailed, and can fully consider the stress effects in all directions, so as to more accurately predict the risk of rock damage. In addition, by establishing a safety threshold and calculating the safety factor, a quantifiable risk assessment standard is provided for excavation operations, which helps to effectively control risks during the construction process, ensure the safety and stability of the rock mass, and reduce the probability of engineering safety accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall method flow of the present invention.

[0019] Figure 2 It is a schematic diagram of the system module flow of the present invention. DETAILED DESCRIPTION

[0020] 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.

[0021] 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.

[0022] Example: See also Figure 1 , a method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction, the specific steps include: Step 1: Obtain the three-dimensional data of the tunnel face of the rock mass to be evaluated, divide the tunnel face of the rock mass to be evaluated into three-dimensional grids based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be tested in the areas to be evaluated. Calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be tested based on the stress contact method; Step 2: Based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated are calculated, and the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated are used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; Step 3: According to the calculation, the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated are obtained, and the original rock stress of the area to be evaluated at the rock face is comprehensively generated; Step 4: A high-precision, long-term three-dimensional mining stress monitoring sensor is buried at the center point of the area to be evaluated on the face to collect the mining stress, and the mining stress is decomposed to generate axial stress, annular stress and radial stress. Based on the axial stress, annular stress and radial stress, the stress threshold of the area to be evaluated on the face is comprehensively generated; Step 5: Establish a safety threshold and count the number of areas to be assessed on the face where the original rock stress exceeds the stress threshold and where the original rock stress does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

[0023] It should be noted that by applying pressure through drilling operations and water injection, the initial fracture pressure, pore pressure and closure pressure related to rock mass fracture can be effectively obtained, thereby calculating the stress values ​​in various directions. This process not only provides a reliable basis for the implementation of the stress contact method, but also reflects the mechanical behavior of the rock mass under different pressure conditions, ensures a comprehensive assessment of the rock mass stability, helps risk prediction and safety assurance in engineering construction, and improves the accuracy and reliability of rock mass stability analysis.

[0024] Therefore, it is necessary to determine and calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the test point based on the stress contact method. The method is as follows: Using hydraulic fracturing, drilling is performed at the interface between the excavation working surface and the unexcavated rock mass, i.e., the face of the rock mass. Water is injected into the borehole to increase the pressure in the hole until the rock mass breaks. The breaking pressure is related to the ground stress. The initial breaking pressure, pore pressure, and closing pressure of the rock at the test point are recorded to calculate the maximum horizontal stress, minimum horizontal stress, and vertical stress. The formula is: ; ; ; in, , , Respectively represent the maximum horizontal stress, minimum horizontal stress, and vertical stress of the test point. represents the initial fracture pressure of rock, Indicates the closing pressure, is the pore pressure, represents the surrounding rock density, Indicates the drilling depth, Indicates the deadweight of the rock.

[0025] It should be noted that the maximum horizontal stress, minimum horizontal stress and vertical stress of the center point of the area to be evaluated are calculated by weighted average method. Based on the stress data of the test point and its spatial distance from the center point, the stress distribution characteristics of the entire area can be accurately reflected. This weighted calculation method takes into account the relationship between the stress influence of each test point and its distance, thereby avoiding the deviation of over-reliance on the data of a single test point and providing the overall stress status of the region.

[0026] Therefore, it is necessary to calculate the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point. The method used is: Determine the coordinates of the center point of the area to be evaluated and mark it as , the first The coordinates of the points to be measured are calibrated as , represents the index of the point to be measured in the area to be evaluated, and , is the number of test points in the area to be evaluated. Based on the stress data of each test point in the area to be evaluated and the distance between the test point and the center point, the maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated, and used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated. The maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated based on the following formula: ; ; ; ; in, , , Respectively at the center point The maximum horizontal stress, minimum horizontal stress and vertical stress at , , Respectively represent the points to be tested The maximum horizontal stress, minimum horizontal stress and vertical stress at Indicates the center point to The distance to the point to be measured.

[0027] It should be noted that the original rock stress of the area to be evaluated at the rock face is calculated by taking the weighted average of the maximum horizontal stress, the minimum horizontal stress and the vertical stress. This weighting method makes the calculation results more consistent with the actual geological conditions according to the relative importance of stress, and can more accurately reflect the overall stress state of the rock mass. Through this method, the comprehensive influence of stresses in different directions on the stability of the rock mass can be effectively considered, providing a more scientific and reliable original rock stress basis for underground engineering design, mining operations and risk assessment.

[0028] Therefore, it is necessary to obtain the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated according to the calculation, and comprehensively generate the original rock stress of the area to be evaluated at the rock face, based on the formula: ; in, Indicates the original rock stress in the area to be evaluated at the rock face. , , are the weight ratios corresponding to the maximum horizontal stress, minimum horizontal stress and vertical stress, respectively. , and satisfy ; In the above formula, the reason why the weight size is set to This is because the maximum horizontal stress is usually the main factor causing rock mass rupture, sliding or deformation. In most underground engineering or mining operations, the maximum horizontal stress is often closely related to rock mass failure mechanisms such as crack expansion and fault activity. Therefore, when comprehensively considering the original stress of the rock mass, the maximum horizontal stress has the greatest impact on the stability of the rock mass, so it should be given the greatest weight. Small horizontal stress usually has little effect on the stability of rock mass, especially in most cases, the rupture and deformation of rock mass are mainly dominated by the maximum horizontal stress. Although the minimum horizontal stress may also affect the stress state of rock mass under certain conditions, such as inducing lateral slip or stress concentration, its influence is usually weak, so it is given the second weight. ; Vertical stress usually has a relatively simple effect under geological conditions, mainly related to gravity, and its destructive effect on rock mass is relatively small. Vertical stress usually works under the compression state of rock mass, but its influence on the overall stability of rock mass is smaller than that of horizontal stress. Therefore, the weight of vertical stress should be the smallest and is set to .

[0029] It should be noted that in underground engineering or rock mechanics, it is very critical to decompose mining stress and obtain axial stress, hoop stress and radial stress, because these stress components directly affect the deformation, fracture and stability of the rock mass. By using the polar coordinate method to decompose dynamic stress, the distribution of stress in different directions can be more accurately described, especially in complex three-dimensional stress fields. Axial stress, hoop stress and radial stress are the core parameters that describe the mechanical behavior of rock mass, which reflect the stress distribution along the axis, hoop and radial directions respectively. By calculating these stress components, the failure mode and deformation characteristics of the rock mass under different conditions can be better predicted, thereby providing a scientific basis for engineering design, mining strategy formulation and rock stability assessment; The reason why mining stress is decomposed and regenerated into stress threshold is that mining stress is the key factor in stress redistribution of rock mass during engineering construction, and its change directly affects the mechanical state of rock mass. When rock mass is subjected to external disturbance, the original rock stress field will change, resulting in a new stress balance. Therefore, mining stress as a threshold can better reflect the stable state of rock mass during actual construction. Compared with the traditional static original rock stress assessment method, mining stress can reflect the stress condition of rock mass in real time. For example, in the process of tunnel excavation and mining, as the excavation progresses, the stress field in front of and around the face is constantly changing. Taking mining stress as a threshold can capture the stress evolution process of rock mass and provide more targeted safety assessment.

[0030] Therefore, it is necessary to decompose the mining stress to generate axial stress, hoop stress and radial stress, based on the following method: The polar coordinate method is used to decompose the dynamic stress at the center point into Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to The dynamic stress of the plane, the axial stress is along the axis direction, directly using the measured perpendicular to Dynamic stress expression of plane; to calculate hoop stress and radial stress, the position angle must be determined and the comprehensive The shear stress on a plane is based on the formula: ; ; ; in, , , They represent axial stress, hoop stress, and radial stress respectively. , , Respectively expressed in Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in a plane, express Shear stress in the plane, Represents the position angle in polar coordinates.

[0031] It should be noted that the three stresses are combined through a formula to form a comprehensive stress threshold, which is crucial for evaluating the stability of the face area. Axial stress, hoop stress and radial stress represent the stress distribution in different directions, which can accurately reflect the stress state of the stratum or structure during the excavation process. The weight setting ensures that different stress components contribute to the stress threshold in different proportions, so that the stress safety of the face area can be accurately evaluated according to the actual working conditions and the safety requirements of the structure. This threshold not only provides a scientific basis for construction safety, but also provides important data support for predicting possible geological disasters and damage.

[0032] Therefore, it is necessary to comprehensively generate the stress threshold of the area to be evaluated on the tunnel face based on the axial stress, hoop stress and radial stress. The formula is as follows: ; in, represents the stress threshold of the area to be evaluated on the tunnel face, , , Respectively represent the weight ratios of axial stress, hoop stress, and radial stress, and In the above formula, more attention should be paid to the annular and radial stresses because the stresses in these two directions are more likely to cause damage and deformation of the structure, while the axial stress has a more indirect effect on the tunnel face area and usually does not directly endanger stability like the annular stress and radial stress. Therefore, the axial stress is given the lowest weight ratio. , giving equal weights to the hoop stress and radial stress , .

[0033] It should be noted that the safety factor obtained by calculating the ratio of the total stress of the original rock that does not exceed the stress threshold to that of the original rock that exceeds the stress threshold is crucial for evaluating the stability of the face area. This method can quantify the bearing capacity and safety of the original rock under different stress states and help identify potential risk areas. A higher safety factor indicates that most of the face area is within the safe stress range, otherwise it indicates that there may be a risk of structural instability. The calculation of this safety factor can not only provide real-time risk assessment during the excavation process, but also provide a scientific basis for engineering design and construction decisions, ensuring the safe operation of underground projects.

[0034] Therefore, it is necessary to count the number of areas to be evaluated where the original rock stress exceeds the stress threshold and the number of areas where the original rock stress does not exceed the stress threshold to calculate the safety factor. The method used is: The ratio of the total stress of the original rock that does not exceed the stress threshold to the total stress of the original rock that exceeds the stress threshold is used as the safety factor, and the formula is as follows: ; in, represents the safety factor, is the total stress of the original rock that does not exceed the stress threshold, is the total original rock stress exceeding the stress threshold.

[0035] It should be noted that by setting a safety threshold and comparing it with the safety factor, the stability of the rock mass at the tunnel face can be effectively judged. This judgment mechanism provides a clear decision-making basis for underground engineering construction. When the safety factor is lower than the set threshold, it indicates that the rock mass is within a safe range and operations can continue; when the safety factor is higher than the threshold, it warns that there is a potential risk of instability in the rock mass, and it is necessary to adjust the operation strategy or reselect the tunnel face in time. This method not only ensures construction safety, but also effectively prevents potential engineering accidents, ensuring the smooth progress of the project and the safety of personnel.

[0036] Therefore, it is necessary to establish a safety threshold, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass at the tunnel face is stable. The logical formula is: ; in, Indicates the logical value for judging whether the rock mass at the tunnel face is stable. When the safety factor is less than the established safety threshold, it means that the face rock mass is stable and the next excavation operation can be carried out; when When the safety factor is greater than or equal to the established safety threshold, it means that the rock mass at the tunnel face is unstable and the tunnel face of the rock mass needs to be reselected.

[0037] See also Figure 2The present invention also provides a tunnel face rock mass stability assessment device based on three-dimensional reconstruction, the assessment device is used to execute the above-mentioned tunnel face rock mass stability assessment method based on three-dimensional reconstruction, comprising: A three-dimensional mesh division and stress calculation module, which is used to obtain three-dimensional data of the tunnel face of the rock mass to be evaluated, perform three-dimensional mesh division on the tunnel face of the rock mass to be evaluated based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be measured in the areas to be evaluated, and calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be measured based on the stress contact method; A stress center calculation module for the area to be evaluated, wherein the stress center calculation module for the area to be evaluated is used to calculate the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, and use the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; An original rock stress comprehensive generation module, the original rock stress comprehensive generation module is used to comprehensively generate the original rock stress of the area to be evaluated in the rock face according to the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated obtained by the calculation; A mining stress monitoring and decomposition module, wherein the mining stress monitoring and decomposition module is used to bury a high-precision, long-lasting three-way mining stress monitoring sensor at the center point of the area to be evaluated on the face to collect its mining stress, decompose the mining stress to generate axial stress, annular stress and radial stress, and comprehensively generate stress thresholds of the area to be evaluated on the face based on the axial stress, annular stress and radial stress; The stability determination module is used to establish a safety threshold and to count the number of areas to be evaluated on the face where the original rock stress exceeds the stress threshold and does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction, characterized in that: The specific steps include: Step 1: Obtain the three-dimensional data of the tunnel face of the rock mass to be evaluated, divide the tunnel face of the rock mass to be evaluated into three-dimensional grids based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be tested in the areas to be evaluated. Calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be tested based on the stress contact method; Step 2: Based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated are calculated, and the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated are used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; Step 3: According to the calculation, the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated are obtained, and the original rock stress of the area to be evaluated at the rock face is comprehensively generated; Step 4: A high-precision, long-term three-dimensional mining stress monitoring sensor is buried at the center point of the area to be evaluated on the face to collect the mining stress, and the mining stress is decomposed to generate axial stress, annular stress and radial stress. Based on the axial stress, annular stress and radial stress, the stress threshold of the area to be evaluated on the face is comprehensively generated; Step 5: Establish a safety threshold and count the number of areas to be assessed on the face where the original rock stress exceeds the stress threshold and where the original rock stress does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

2. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: The maximum horizontal stress, minimum horizontal stress and vertical stress of the test point are determined and calculated based on the stress contact method. The method is as follows: Using hydraulic fracturing, drilling is performed at the interface between the excavation working surface and the unexcavated rock mass, i.e., the face of the rock mass. Water is injected into the borehole to increase the pressure in the hole until the rock mass breaks. The breaking pressure is related to the ground stress. The initial breaking pressure, pore pressure, and closing pressure of the rock at the test point are recorded to calculate the maximum horizontal stress, minimum horizontal stress, and vertical stress. The formula is: ； ； ； in, , , Respectively represent the maximum horizontal stress, minimum horizontal stress, and vertical stress of the test point. represents the initial fracture pressure of rock, Indicates the closing pressure, is the pore pressure, represents the surrounding rock density, Indicates the drilling depth, Indicates the deadweight of the rock.

3. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 2, characterized in that: Based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated are calculated according to the following method: Determine the coordinates of the center point of the area to be evaluated and mark it as , the first The coordinates of the points to be measured are calibrated as , represents the index of the point to be measured in the area to be evaluated, and , is the number of test points in the area to be evaluated. Based on the stress data of each test point in the area to be evaluated and the distance between the test point and the center point, the maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated, and used as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated. The maximum horizontal stress, minimum horizontal stress and vertical stress of the center point are calculated according to the following formula: ； ； ； ； in, , , Respectively at the center point The maximum horizontal stress, minimum horizontal stress and vertical stress at , , Respectively represent the points to be tested The maximum horizontal stress, minimum horizontal stress and vertical stress at Indicates the center point to The distance to the point to be measured.

4. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: According to the calculation, the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated are obtained, and the original rock stress of the area to be evaluated in the rock face is comprehensively generated, and the formula based on it is: ； in, Indicates the original rock stress in the area to be evaluated at the rock face. , , are the weight ratios corresponding to the maximum horizontal stress, minimum horizontal stress and vertical stress, respectively. , and satisfy .

5. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: The mining stresses are decomposed to generate axial stress, hoop stress and radial stress according to the following method: The polar coordinate method is used to decompose the dynamic stress at the center point into Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to The dynamic stress of the plane, the axial stress is along the axis direction, directly using the measured perpendicular to Dynamic stress representation of a plane; To calculate the hoop stress and radial stress, the position angle must be determined and the The shear stress on a plane is based on the formula: ； ； ； in, , , They represent axial stress, hoop stress, and radial stress respectively. , , Respectively expressed in Direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in the plane, Axis direction perpendicular to Dynamic stress in a plane, express Shear stress in the plane, Represents the position angle in polar coordinates.

6. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: Based on the axial stress, hoop stress and radial stress, the stress threshold of the area to be evaluated in the tunnel face is comprehensively generated according to the formula: ； in, represents the stress threshold of the area to be evaluated on the tunnel face, , , They represent the weight ratios of axial stress, hoop stress, and radial stress, respectively, and .

7. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: The number of areas to be evaluated in the tunnel face where the original rock stress exceeds the stress threshold and the number of areas where the original rock stress does not exceed the stress threshold are counted to calculate the safety factor. The method used is: The ratio of the total stress of the original rock that does not exceed the stress threshold to the total stress of the original rock that exceeds the stress threshold is used as the safety factor, and the formula is as follows: ； in, represents the safety factor, is the sum of the original rock stress in all areas that do not exceed the stress threshold, It is the sum of the original rock stress in all areas exceeding the stress threshold.

8. The method for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction according to claim 1, characterized in that: The safety threshold is established, the relationship between the safety factor and the safety threshold is determined, and whether the rock mass at the tunnel face is stable is determined based on the following logical formula: ； in, Indicates the logical value for judging whether the rock mass at the tunnel face is stable. When the safety factor is less than the established safety threshold, it means that the face rock mass is stable and the next excavation operation can be carried out; when When the safety factor is greater than or equal to the established safety threshold, it means that the rock mass at the tunnel face is unstable and the tunnel face of the rock mass needs to be reselected.

9. A device for assessing the stability of a tunnel face rock mass based on three-dimensional reconstruction, characterized in that: The evaluation device is used to execute the method for evaluating the stability of a tunnel face rock mass based on three-dimensional reconstruction according to any one of claims 1 to 8, comprising: A three-dimensional mesh division and stress calculation module, which is used to obtain three-dimensional data of the tunnel face of the rock mass to be evaluated, perform three-dimensional mesh division on the tunnel face of the rock mass to be evaluated based on the three-dimensional reconstruction technology, divide the tunnel face of the rock mass to be evaluated into multiple areas to be evaluated, and set multiple points to be measured in the areas to be evaluated, and calculate the maximum horizontal stress, minimum horizontal stress and vertical stress of the points to be measured based on the stress contact method; A stress center calculation module for the area to be evaluated, wherein the stress center calculation module for the area to be evaluated is used to calculate the maximum horizontal stress, minimum horizontal stress and vertical stress at the center point of the area to be evaluated based on the calculated maximum horizontal stress, minimum horizontal stress and vertical stress of each test point, and use the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated as the maximum horizontal stress, minimum horizontal stress and vertical stress of the area to be evaluated; An original rock stress comprehensive generation module, the original rock stress comprehensive generation module is used to comprehensively generate the original rock stress of the area to be evaluated in the rock face according to the maximum horizontal stress, the minimum horizontal stress and the vertical stress of the area to be evaluated obtained by the calculation; A mining stress monitoring and decomposition module, wherein the mining stress monitoring and decomposition module is used to bury a high-precision, long-lasting three-way mining stress monitoring sensor at the center point of the area to be evaluated on the face to collect its mining stress, decompose the mining stress to generate axial stress, annular stress and radial stress, and comprehensively generate stress thresholds of the area to be evaluated on the face based on the axial stress, annular stress and radial stress; The stability determination module is used to establish a safety threshold and to count the number of areas to be evaluated on the face where the original rock stress exceeds the stress threshold and does not exceed the stress threshold, so as to calculate the safety factor, determine the relationship between the safety factor and the safety threshold, and determine whether the rock mass on the face is stable.

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