Pre-stressed anchor cable construction arrangement quality evaluation method

Abstract

The invention provides a pre-stressed anchor cable construction arrangement quality evaluation method, and relates to the field of underground engineering, and the method comprises the following steps: S1, model construction: building three-dimensional numerical models of different anchor rod arrangement schemes; s2, simulation calculation and result evaluation, wherein excavation simulation calculation is executed according to the three-dimensional numerical models of different anchor rod arrangement schemes, and numerical simulation calculation results of surrounding rock deformation, stress distribution, damage and fracture area distribution and supporting structure stress are obtained; evaluating numerical simulation calculation results of different anchor rod arrangement schemes to obtain evaluation indexes, and determining an optimal scheme according to the evaluation indexes. Through the cooperation of the above structures, the method has the following beneficial effects: 1, the evaluation accuracy can be comprehensively improved, and the data is converted into a visual and quantitative evaluation result by constructing a comprehensive evaluation system and applying a data analysis model and algorithm; and secondly, by establishing an error correction model, the deviation between numerical simulation and on-site monitoring data can be accurately calibrated.

Description

Technical Field

[0001] The invention relates to the field of underground engineering, and in particular to a method for evaluating the construction layout quality of a prestressed anchor cable. Background Art

[0002] my country will usher in a new round of engineering construction in many fields such as new energy, hydropower, urban construction, national defense security, etc. The development and utilization of underground space resources such as underground caverns in hydropower stations, underground carbon dioxide storage, underground storage of nuclear waste, national defense hangars, and underground oil depots will become more and more common.

[0003] According to different construction needs, the geological environment of underground caverns is complex, and it is gradually developing towards the direction of deep burial, large span, large scale, and high requirements for safety construction. During the construction period and long-term operation of underground caverns, ensuring the dual safety of surrounding rock stability and support structure stress is one of the issues that must be focused on in the safety management of engineering buildings throughout their life cycle.

[0004] At present, in the design of prestressed anchor support for the remaining excavation layer of the main powerhouse of a hydropower station, there is a need to optimize the spacing of prestressed anchor cables. However, there is currently a lack of an effective method to determine the optimal anchor cable arrangement scheme. Therefore, the key technical problem lies in how to effectively evaluate and determine the optimal spacing of prestressed anchor cables to ensure the support effect while reducing surrounding rock deformation and stress concentration, thereby improving construction efficiency and economic benefits. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a method for evaluating the construction layout quality of prestressed anchor cables, which can effectively evaluate and determine the optimal spacing of prestressed anchor cables to ensure the support effect while reducing surrounding rock deformation and stress concentration.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: the present invention provides a method for evaluating the construction layout quality of prestressed anchor cables, comprising the following steps: S1. Basic data preparation: obtain and preprocess the geological survey data of the underground cavern group, and establish a three-dimensional numerical model based on the preprocessed geological survey data; S2. Model basic settings: Determine the surrounding rock types in different regions based on geological survey data, determine rock mass parameters based on the surrounding rock types, and select constitutive models based on the surrounding rock parameters, including elastic-plastic models and stress-crack strain evolution constitutive models; S3. Model characteristics research: obtain the mechanical characteristic parameters of the rock mass through specific test methods, establish the stress-crack strain evolution constitutive model, analyze the crack evolution law, determine the criteria for the surrounding rock relaxation zone, and conduct secondary development of the constitutive model; S4. Engineering construction simulation: simulate the excavation sequence design based on the graded excavation scheme, analyze the anchor support strength, determine the support parameters and evaluate them; S5. Geostress field analysis: The initial geostress multivariate regression method and the geostress field inversion method of the generative adversarial network (GAN) are used to calculate the stress state of the surrounding rock before construction and excavation and determine the mechanical parameters. S6. Scheme optimization decision: Through numerical simulation analysis, the surrounding rock deformation, stress distribution and plastic failure zone distribution characteristics under different anchor cable layout schemes are analyzed to optimize the anchor cable layout scheme.

[0007] In a preferred solution, in step S1, the geological survey data includes physical and mechanical parameters of the rock mass, ground stress measurement data and structural surface characteristics; Among them, the physical and mechanical parameters of rock mass include natural density, deformation modulus, Poisson's ratio, and shear strength; The preprocessing operation is to sort and screen the collected geological survey data, remove abnormal data and normalize them for model input and calculation; A three-dimensional numerical model of the main chambers including the installation room, main and auxiliary powerhouse caverns, main transformer room, and tailwater surge chamber is established based on the pre-processed geological survey data; The three-dimensional numerical model uses three-dimensional 8-node hexahedron isoparametric solid elements and their degenerate elements to simulate rock mass and faults. The overall model has 91479 solid element nodes, 181231 solid elements, 51803 anchor element nodes, and 26089 anchor elements.

[0008] In a preferred solution, in step S2, the physical and mechanical parameters of the rock mass are calculated according to empirical formulas to obtain rock mass parameters, and the calculated rock mass parameters are corrected in combination with engineering experience and on-site monitoring data; Among them, the elastic-plastic model determines the cracking conditions of rock materials through macroscopic strength, and determines that the rock mass enters the plastic state based on the Druker-Prager criterion; When the constitutive model is applied to the three-dimensional numerical model, the deformation, stress distribution and failure characteristics of the surrounding rock are analyzed by setting the parameters of the constitutive model and the boundary conditions of the three-dimensional numerical model and performing numerical simulation calculations using specific methods; Among them, the parameter settings of the constitutive model include the yield stress and hardening parameters of the elastic-plastic model and the crack closure and expansion parameters of the stress-crack-strain evolution constitutive model.

[0009] In the preferred solution, in step S3, the mechanical property parameters of the rock mass include peak stress, elastic modulus, and Poisson's ratio, and the specific test method is selected as a triaxial compression test. Through rock sample preparation and test loading, the stress-strain curve, threshold stress, elastic modulus and Poisson's ratio, stress-crack strain evolution constitutive model, crack evolution law, and surrounding rock relaxation zone criterion are analyzed, and the constitutive model code is compiled and verified in FLAC3D. The specific steps are as follows: Collect rock samples and use a rock triaxial testing machine; And the peak stress is , confining pressure , confining pressure The value range of is: MPa, and MPa, loading rate is confining pressure Loading was performed at 0.05 MPa / s, and the axial load was increased at 0.5 MPa / s until the rock sample failed; Peak stress With confining pressure Increases and increases, the peak stress Confining pressure The relationship between is expressed by the formula as follows: ; Assume that the threshold stresses are the crack closure stress , crack initiation stress , crack damage stress ; The relationship between the ratio of threshold stress to peak strength Rcc d, Rci d and Rcd d and the confining pressure can be fitted by the following formula: ; Among them, a, b, c, and d are fitting parameters; In the preferred solution, the rock sample test data under multiple confining pressures are fitted, and the different confining pressures The corresponding peak stress They are 114.72MPa, 139.65MPa, 157.22MPa, 182.97MPa, 216.30MPa, 345.73MPa and 374.63MPa respectively; Through different confining pressure Lower crack closure stress , crack initiation stress , crack damage stress Different from the ratio of the peak intensity, the values ​​of Rcc d, Rci d and Rcd d are 0.22 respectively. , 0.41 and 0.78 , and with the confining pressure Increase and gradually decrease.

[0010] In the preferred scheme, in step S3, the specific test method is selected as the creep test, and the multi-step loading method is adopted. The creep strain, stress and instantaneous strain, the constitutive relationship of creep strain, long-term strength and creep strain rate are analyzed by setting the rock sample parameters and the test method, and the Nishihara creep model is improved to verify the correctness of the initial parameters. The specific steps are as follows: Confining pressure The value is MPa, the axial stress value is 0.55-1.00 times the peak strength; The axial creep strain increases with time and is more obvious at high deviatoric stress levels. The total strain consists of instantaneous strain and creep strain. The creep strain includes viscoelastic creep strain and viscoplastic creep strain. By analyzing the creep strain data under different confining pressures and deviatoric stresses, the instantaneous strain and deviatoric stress-peak strength ratio The relationship can be expressed as: ; Viscoelastic creep strain and The relationship can be expressed as: ; Viscoplastic creep strain Confining pressure The relationship can be expressed as: ; in, , , , is a variable.

[0011] In a preferred solution, in step S4, the hierarchical excavation scheme includes excavation sequence, anchor support strength analysis, support parameters and evaluation; Among them, the excavation sequence is simulated according to the actual construction process, the anchor support strength analysis is based on the indoor test results and field monitoring data, and the support parameters and evaluation are combined with theoretical analysis and numerical simulation results; The cohesion increment of the surrounding rock of the prestressed anchor cable support is calculated and compared with the value calculated by the empirical formula to determine whether the support strength is sufficient.

[0012] In a preferred solution, in step S6, the following steps are also included: S61. Deformation characteristics of surrounding rock: Obtain the deformation of each part of the cave body during each level of excavation, and analyze the changing trend of the deformation under each level of excavation and the deformation differences of different parts; S62, stress distribution characteristics: determine the stress concentration area of ​​the main cavern after each level of excavation, and compare the stress extreme value changes of the stress concentration area of ​​different schemes; S63, distribution characteristics of plastic failure zone: obtain the depth of plastic failure zone of surrounding rock of each unit; S64. Determine the three-dimensional numerical model under different anchor cable arrangement schemes according to the deformation characteristics, stress distribution characteristics and plastic failure zone distribution characteristics of the surrounding rock, and perform excavation simulation calculation based on the three-dimensional numerical model under different anchor cable arrangement schemes to obtain the surrounding rock deformation results, stress distribution results and plastic failure zone results.

[0013] In a preferred solution, in step S64, the surrounding rock stability under different anchor cable arrangement schemes is determined according to the surrounding rock deformation results, stress distribution results and plastic failure zone results, and the optimal solution is determined according to the surrounding rock stability under different anchor cable arrangement schemes.

[0014] In the preferred solution, the deformation, stress distribution and damage zone conditions monitored on site are obtained; The surrounding rock deformation results, stress distribution results and plastic failure zone results are compared with the deformation, stress distribution and failure zone conditions monitored on site, and the statistical analysis method is used for quantitative evaluation to obtain the comparison results; Wherein, the statistical analysis method is one of the root mean square error or correlation coefficient; According to the comparison results, an error correction model of the evaluation method is established to pre-adjust the parameters under different anchor cable layout schemes.

[0015] The present invention provides a method for evaluating the quality of prestressed anchor cable construction arrangement, which has the following beneficial effects through the cooperation between the above structures: First, it can achieve accurate simulation and analysis of the construction process of underground caverns. By obtaining detailed geological survey data and establishing accurate three-dimensional numerical models, combined with a variety of advanced constitutive models and experimental research results, it can accurately reflect the mechanical properties and geological conditions of the rock mass, provide a scientific basis for the formulation of construction plans, and effectively reduce uncertainties and risks in the construction process. Second, optimize the anchor cable layout plan and improve the support effect. By systematically analyzing the deformation, stress distribution and plastic failure zone characteristics of the surrounding rock under different anchor cable layout plans, the optimal anchor cable layout parameters can be determined, so that the anchor cables can fully play their role in reinforcing the surrounding rock, effectively control the deformation of the surrounding rock, reduce the degree of stress concentration, and reduce the scope of the plastic failure zone, thereby enhancing the stability and safety of the underground cavern group and extending its service life.

[0016] Third, to improve the accuracy and reliability of engineering quality assessment, a variety of methods and data are used in the entire assessment process, including field monitoring data, indoor test data and numerical simulation results, which verify and supplement each other, and the accuracy of the assessment results is ensured through strict logical steps and scientific calculation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is a calculation range diagram of the underground powerhouse in the present invention; Figure 2 It is a typical geological profile of the underground powerhouse of the present invention; Figure 3 It is the overall three-dimensional finite element simulation model of the present invention; Figure 4 The present invention C 3. Time-dependent variation trend diagram; Figure 5 It is a time-dependent displacement cloud diagram of the displacement of the surrounding rock at the 1# unit in the first-level excavation under the support working condition of the present invention; Figure 6 It is a time-dependent displacement cloud diagram of the surrounding rock displacement at the 4# unit in the first-level excavation under the support working condition of the present invention; Figure 7 It is the contour map of the first-level excavation displacement Uz of the installation room of the present invention; Figure 8 It is the contour map of the first-level excavation displacement Uy of the installation room of the present invention. DETAILED DESCRIPTION

[0018] In order to better understand the purpose, structure and function of the present invention, the embodiments and features in the embodiments of the present application can be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] Example 1 like Figures 1 to 8 As shown, this embodiment provides a method for evaluating the quality of prestressed anchor cable construction arrangement, comprising the following steps: S1. Basic data preparation: obtain and preprocess the geological survey data of the underground cavern group, and establish a three-dimensional numerical model based on the preprocessed geological survey data; In a preferred solution, in step S1, the geological survey data includes physical and mechanical parameters of the rock mass, ground stress measurement data and structural surface characteristics; Among them, the physical and mechanical parameters of rock mass include natural density, deformation modulus, Poisson's ratio, and shear strength; Specifically, the physical and mechanical parameters of the rock mass are obtained by using a variety of geological survey methods, such as on-site sampling tests, geophysical exploration, etc., to obtain key physical and mechanical parameters such as the natural density, deformation modulus, Poisson's ratio, and shear strength of the rock mass. These parameters reflect the basic mechanical properties of the rock mass. For example, in the granite rock mass of the Shuangjiangkou Hydropower Station, the natural density of the Class II surrounding rock mass is 2.6g / cm³, the deformation modulus is 32.5GPa, and the Poisson's ratio is 0.25. These data provide a basis for subsequent analysis; The geostress measurement data uses professional measurement methods such as stress relief method and hydraulic fracturing method to determine the geostress distribution in the area where the underground cavern group is located, including the size, direction and distribution law of geostress. Geostress is an important factor affecting the stability of rock mass, and its measurement results are crucial for accurately simulating the mechanical response of rock mass during excavation; Detailed investigation of the location, occurrence, spacing, filling properties and other characteristics of faults, joints and fissures in the rock mass. The existence of these structural surfaces will significantly weaken the strength and integrity of the rock mass. For example, in some areas, the existence of faults may cause a sudden change in the mechanical properties of the rock mass, so it is necessary to accurately record relevant information during the data acquisition process.

[0020] The preprocessing operation is to sort and screen the collected geological survey data, remove abnormal data and normalize them for model input and calculation; Specifically, the large amount of geological survey data collected is systematically sorted, and the obviously abnormal data is identified and removed based on professional geological knowledge and statistical analysis methods. Furthermore, if a group of rock mass strength data differs too much from the data in the surrounding area and does not conform to geological laws, it may be an outlier caused by test errors or special geological conditions, and it needs to be eliminated to ensure the reliability and accuracy of the data; Adopt appropriate normalization method, i.e. linear normalization or standardization, to unify geological survey data of different magnitudes and units into a reasonable numerical range, which is convenient for input and calculation of subsequent models. Furthermore, for stress data, the formula can be used: Perform normalization processing; in, is the normalized parameter value, is the original parameter value, and are the minimum and maximum values ​​of the parameters, respectively, so that all stress data can be analyzed and compared in the range of 0 to 1.

[0021] A three-dimensional numerical model of the main chambers including the installation room, main and auxiliary powerhouse caverns, main transformer room, and tailwater surge chamber is established based on the pre-processed geological survey data; The three-dimensional numerical model uses three-dimensional 8-node hexahedron isoparametric solid elements and their degenerate elements to simulate rock mass and faults. Specifically, if Figure 1 , 2 As shown, the calculation range of the three-dimensional numerical model is determined according to the actual layout of the underground cavern group and engineering requirements; Furthermore, along the axis of the plant building in the x-axis direction, from unit 1 to unit 4, the intercept length is 275.7m (from 0-098.82 on the horizontal axis to 0+176.88 on the horizontal axis); The y-axis horizontally points from the main powerhouse to the tail adjustment room, with a cut length of 300.0m; The z-axis is vertically upward, with the bottom at an elevation of ▽2170.0m and the top extending to the surface of the mountain top, ensuring that the model can cover the key geological areas of the main caverns such as the installation room, main and auxiliary powerhouse caverns, main transformer room, tailwater surge chamber and their surrounding areas, and fully reflect the relationship between geological conditions and engineering structures, as shown in Table 1 below: Table 1 Typical cross-sectional locations of Shuangjiangkou underground powerhouse

[0022] Three-dimensional 8-node hexahedral isoparametric solid elements and their degenerate elements are used to simulate rock masses and faults. This unit type can better adapt to complex geological shapes and mechanical behaviors. Through reasonable grid division, a three-dimensional numerical model with 91479 solid unit nodes, 181231 solid units, 51803 anchor unit nodes and 26089 anchor units is constructed, providing an accurate geometric and physical model basis for subsequent numerical simulations.

[0023] S2. Model basic settings: Determine the surrounding rock types in different regions based on geological survey data, determine rock mass parameters based on the surrounding rock types, and select constitutive models based on the surrounding rock parameters, including elastic-plastic models and stress-crack strain evolution constitutive models; In a preferred solution, in step S2, the physical and mechanical parameters of the rock mass are calculated according to empirical formulas to obtain rock mass parameters, and the calculated rock mass parameters are corrected in combination with engineering experience and on-site monitoring data; Specifically, first, according to the type of surrounding rock, the relevant empirical formulas are used to calculate the physical and mechanical parameters of the rock mass. For example, for different types of granite, the deformation modulus, shear strength and other parameters can be calculated by referring to the existing empirical formulas. However, there may be certain errors in the calculation results of these empirical formulas, so they need to be corrected in combination with engineering experience and field monitoring data. By analyzing the data of surrounding rock deformation, stress changes and other data monitored on site, and referring to the actual experience of similar projects, the calculated rock mass parameters are reasonably adjusted to make them more in line with the actual engineering situation. For example, if field monitoring finds that the deformation of the surrounding rock in a certain area exceeds expectations, it may be necessary to appropriately reduce the calculated rock mass strength parameters to more accurately reflect the actual mechanical properties of the rock mass in that area.

[0024] Among them, the elastoplastic model determines the cracking conditions of rock materials through macroscopic strength, and determines that the rock enters the plastic state based on the Druker-Prager criterion. The elastoplastic model can better describe the plastic deformation and yield behavior of the rock in the stress process, while the stress-crack strain evolution constitutive model focuses more on considering the influence of the generation, expansion and closure of cracks in the rock on the mechanical properties of the rock, and is especially suitable for rock with developed cracks under high ground stress conditions; When the constitutive model is applied to the three-dimensional numerical model, the deformation, stress distribution and failure characteristics of the surrounding rock are analyzed by setting the parameters of the constitutive model and the boundary conditions of the three-dimensional numerical model and performing numerical simulation calculations using specific methods; Specifically, Figure 3 As shown in the figure, when the constitutive model is applied to the three-dimensional numerical model, a series of model parameters need to be set, including the yield stress and hardening parameters of the elastic-plastic model and the crack closure and expansion parameters of the stress-crack-strain evolution constitutive model. The values ​​of these parameters directly affect the simulation accuracy of the model on the mechanical behavior of the rock mass. Furthermore, for the elastic-plastic model, according to the rock mass strength parameters determined by indoor tests and field monitoring data, combined with the Druker-Prager criterion, reasonable yield stress and hardening parameters are set to accurately simulate the conditions and process of the rock mass entering the plastic state. At the same time, by setting the boundary conditions of the three-dimensional numerical model, such as displacement constraints and stress boundary conditions, the boundary stress conditions of the rock mass in the actual project are simulated, and then a specific numerical calculation method (such as the finite element method) is used to perform numerical simulation calculations, and the deformation, stress distribution and failure characteristics of the surrounding rock during excavation and support are analyzed, providing a theoretical basis for subsequent engineering construction simulation and scheme optimization.

[0025] Among them, the parameter settings of the constitutive model include the yield stress and hardening parameters of the elastic-plastic model and the crack closure and expansion parameters of the stress-crack-strain evolution constitutive model.

[0026] S3. Model characteristics research: obtain the mechanical characteristic parameters of the rock mass through specific test methods, establish the stress-crack strain evolution constitutive model, analyze the crack evolution law, determine the criteria for the surrounding rock relaxation zone, and conduct secondary development of the constitutive model; In the preferred solution, in step S3, the mechanical property parameters of the rock mass include peak stress, elastic modulus, and Poisson's ratio, and the specific test method is selected as a triaxial compression test. Through rock sample preparation and test loading, the stress-strain curve, threshold stress, elastic modulus and Poisson's ratio, stress-crack strain evolution constitutive model, crack evolution law, and surrounding rock relaxation zone criterion are analyzed, and the constitutive model code is compiled and verified in FLAC3D. The specific steps are as follows: Specifically, representative rock samples are collected from the project site and processed into φ50×100mm cylindrical standard specimens according to strict standards to ensure that the diameter, height-to-diameter ratio, end face parallelism and other parameters of the rock samples meet the test requirements. For example, the diameter needs to be controlled between 48-52mm, the height-to-diameter ratio is controlled between 1.9-2.1, and the parallelism error of the two end faces should be less than 5×10⁻²mm to ensure the accuracy and comparability of the test results. The advanced MTS815FlexTestGT rock triaxial testing machine is used for the test, and the instrument is accurately calibrated before the test to ensure that the load and deformation measurement accuracy meets the test requirements.

[0027] And the peak stress is , confining pressure , confining pressure The value range of is: MPa, and MPa, loading rate is confining pressure Loading was performed at 0.05 MPa / s, and the axial load was increased at 0.5 MPa / s until the rock sample failed; During the test, the stress and strain data of the rock samples are collected in real time, including axial stress, radial stress, axial strain, radial strain, etc., and the mechanical response of the rock samples at different loading stages is recorded.

[0028] Peak stress With confining pressure Increases and increases, the peak stress Confining pressure The relationship between is expressed by the formula as follows: ; The experimental data of granite samples from Shuangjiangkou Hydropower Station were fitted to obtain the results under different confining pressures. , peak stress They are 114.72 MPa, 139.65 MPa, 157.22 MPa, 182.97 MPa, 216.30 MPa, 345.73 MPa, and 374.63 MPa respectively; Let the threshold stresses be the crack closure stress , the crack initiation stress , and the crack damage stress ; The relationships between the ratios Rcc d, Rci d, and Rcd d of the threshold stress to the peak strength and the confining pressure can be fitted by the following formulas: ; where a, b, c, and d are fitting parameters; Through the crack closure stress , the crack initiation stress , and the crack damage stress under different confining pressures , the ratios to the peak strength are different, and the values of Rcc d, Rci d, and Rcd d are 0.22 , 0.41 , and 0.78 respectively, and gradually decrease with the increase of the confining pressure .

[0029] Elastic modulus and Poisson's ratio: The elastic modulus and Poisson's ratio have an exponential relationship with the confining pressure and tend to a constant value when the confining pressure increases.

[0030] Stress-crack strain evolution constitutive model: Use quasi-viscous and plastic elements to represent the relationship between the axial and radial crack strains and the ratio Rd of the deviator stress to the peak strength in the crack development stage, and determine the crack strain expressions and related parameters in each stage, such as the quasi-viscosity coefficient in the crack closure stage, stable growth stage, unstable growth stage, and post-peak stage.

[0031] Crack evolution law: When MPa, analyze the variation laws of the crack closure degree and under different , as well as the ratios of the axial and radial crack strains to the total strain in the unstable growth stage and post-peak stage of the crack under high, medium, and low confining pressures, indicating that the radial crack expansion is the main cause of rock failure, specifically as follows: As Figure 4 shown, when Mpa, in the stable growth stage (Rcc d < R d < Rcd d), the crack evolution is slow, and the crack closure degree C gradually decreases to 0; while in the unstable growth stage of the crack (Rcd d < R d<1), the crack expansion speed gradually increases, and the crack closure degree C 3 Follow R d decreases rapidly with the increase of R d = 1 o'clock, C 3 = -17.71, the rock begins to break and enters the softening stage. R d Reduced, while C 3 continued to decrease to -28.0, and the rock completely disintegrated. Under the action of time, the tangential and radial stresses of the cave wall will gradually release, and the setting of anchor cables and anchor rods provides radial compressive stress for the surrounding rock, compensating for the radial stress released by the surrounding rock itself, making the difference between tangential stress and radial stress smaller than that of the unsupported working condition, thereby making the crack closure degree of the rock mass C 3 is in the non-destructive stage.

[0032] The criteria for the surrounding rock relaxation zone are shown in the following table: Table 2 Relaxation failure zones of surrounding rock

[0033] According to the degree of crack closure The surrounding rock unloading relaxation zone is divided into the destruction zone (C3<-25), the strong relaxation zone (-25≤ <-17), weak relaxation zone (-17≤ <-2), stress disturbance area (-2≤ <0) and protolith area ( ≥0) and give the corresponding wave velocity and apparent deformation modulus partition index; Furthermore, in step S3, the specific test method is selected as the creep test, and the multi-step loading method is adopted. Through the rock sample parameters and the test method setting, the creep strain, stress and instantaneous strain, the constitutive relationship of creep strain, long-term strength and creep strain rate are analyzed, and the Nishihara creep model is improved to verify the correctness of the initial parameters. The specific steps are as follows: Confining pressure The value is MPa, the axial stress value is 0.55-1.00 times the peak strength; Analysis of the test data shows that the axial creep strain increases with time, especially at high deviatoric stress levels. The total strain consists of instantaneous strain and creep strain, and the creep strain includes viscoelastic creep strain and viscoplastic creep strain. By fitting and analyzing the creep strain data under different confining pressures and deviatoric stresses, the instantaneous strain and deviatoric stress-peak strength ratio The relationship can be expressed as: ; Viscoelastic creep strain and The relationship can be expressed as: ; Viscoplastic creep strain Confining pressure The relationship can be expressed as: ; in, , , , is a variable.

[0034] According to the relationship between viscoelastic creep strain and viscoplastic creep strain, the traditional Nishihara creep model is improved by taking the confining pressure and Introduce into the model and determine the instantaneous elastic modulus in the improved model , Kelvin elastic modulus , viscosity coefficient and The isoparametric expressions can more accurately describe the time-dependent behavior of rock mass, including decay creep and steady-state creep stages.

[0035] Further, if Figure 5 , 6 As shown, initial parameter determination and verification: Determine the initial parameters of the improved Nishihara creep model: , , ), the correctness of the initial parameters was verified by comparing the numerical calculation of the time-dependent deformation after the first level of excavation under the supported excavation condition with the on-site monitoring data. Furthermore, the calculation results of the time-dependent displacement cloud map of the surrounding rock at the No. 1 unit of the main powerhouse were compared with the on-site monitoring data. The calculated values ​​were close to the monitored values ​​and had the same deformation trend, indicating that the determined initial parameters can reasonably reflect the creep characteristics of the rock mass and provide a reliable parameter basis for subsequent engineering analysis and prediction.

[0036] S4. Engineering construction simulation: simulate the excavation sequence design based on the graded excavation scheme, analyze the anchor support strength, determine the support parameters and evaluate them; In a preferred solution, in step S4, the hierarchical excavation scheme includes excavation sequence, anchor support strength analysis, support parameters and evaluation; Among them, the excavation sequence is simulated according to the actual construction process, the anchor support strength analysis is based on the indoor test results and field monitoring data, and the support parameters and evaluation are combined with theoretical analysis and numerical simulation results; The cohesion increment of the surrounding rock of the prestressed anchor cable support is calculated and compared with the value calculated by the empirical formula to determine whether the support strength is sufficient.

[0037] Specifically, according to the actual construction process and geological conditions of the project, a detailed hierarchical excavation plan is formulated. For example, for the main powerhouse of Shuangjiangkou Hydropower Station, excavation is carried out from layer A to layer H in sequence, and support is carried out in time after each layer is excavated, and the starting and ending elevation ranges of each layer of excavation and support are clearly defined. For example, the starting and ending elevations of excavation and support of layer A of the main powerhouse are 2282.32 to 2273.32m. During the excavation process, full consideration is given to factors such as changes in geological conditions, mutual influence between caverns, and construction safety, and the excavation sequence and progress are reasonably arranged to minimize disturbance to the surrounding rock and ensure the stability of the construction process, as shown in the following table: Table 3 Layered excavation characteristics of the powerhouse on the left bank of Shuangjiangkou

[0038] Analysis based on test and monitoring data: Anchor support strength analysis is based on indoor test results and field monitoring data. Through the analysis of a large number of indoor triaxial compression test and creep test data, combined with the surrounding rock deformation, stress changes and anchor force conditions monitored on site, the support effect of anchor cables under different geological conditions and construction stages is studied in depth. For example, based on the rock mass mechanical parameters obtained from the test and the anchoring performance of the anchor cable, the force distribution and deformation characteristics of the anchor cable when subjected to surrounding rock pressure are analyzed to determine the maximum support force and effective support range that the anchor cable can provide.

[0039] Calculation and comparison of empirical formulas: Through statistical analysis of underground powerhouse data of 20 domestic hydropower projects, empirical formulas for anchor support strength, strength-stress ratio, and excavation span are proposed. Through analysis of data from 12 domestic large and medium-sized hydropower stations, empirical formulas for anchor support strength, strength-stress ratio, and powerhouse span are obtained. Furthermore, the relationship formula between the cohesion increment of surrounding rock reinforced by anchor cables and the strength-stress ratio is obtained. According to the specific geological conditions and engineering parameters of the Shuangjiangkou Hydropower Station, the theoretical support strength of the anchor cable is calculated. At the same time, the cohesion increment of the surrounding rock of the actual designed anchor cable support is calculated and compared with the calculated value of the empirical formula to evaluate whether the anchor cable support meets the strength standard required by the project. By defining a dimensionless anchor cable support index, the anchor cable support strength is quantitatively evaluated to judge its effectiveness and reliability in the project: ; Determination of support parameters: Based on theoretical analysis, numerical simulation results, and on-site monitoring data, combined with engineering experience, the detailed layout parameters of anchor cables and anchor rods in various parts such as the main powerhouse, main transformer room, and tail adjustment room are determined, including anchor cable position, pile number, elevation, anchor cable internal force, length, spacing, angle, etc., as well as anchor rod type, length, spacing, etc. For example, the anchor cable T=2000kN, L=20m, and spacing parameters at the upstream arch foot of the main and auxiliary powerhouses are reasonably designed according to the mechanical properties of the surrounding rock and the structural form of the cavern to ensure that the support structure can effectively restrain the deformation of the surrounding rock and improve the stability of the cavern.

[0040] Support effect evaluation: The support effect of the determined support parameters is evaluated. The deformation, stress distribution and plastic failure zone of the surrounding rock under different support parameters are calculated through numerical simulation, and compared with the situation without support or with other support parameters. For example, the deformation and stress concentration of the surrounding rock of the side wall of the main powerhouse of Shuangjiangkou Hydropower Station under different anchor spacing and length are calculated to evaluate the improvement effect of the anchor on the stability of the surrounding rock; for prestressed anchor cables, the adjustment effect on the stress state of the surrounding rock and the suppression effect on the plastic failure zone under different prestress levels are analyzed. According to the evaluation results, the support parameters are optimized and adjusted to achieve the best support effect, and at the same time, factors such as construction cost and construction period are considered to achieve comprehensive optimization of the support scheme.

[0041] S5. Geostress field analysis: The initial geostress multivariate regression method and the geostress field inversion method of the generative adversarial network (GAN) are used to calculate the stress state of the surrounding rock before construction and excavation and determine the mechanical parameters. Specifically, the geostress regression calculation adopts the fitting idea of ​​the combined effect of self-weight stress and boundary load, and uses the multivariate linear regression method. The geostress regression calculation value is used as the dependent variable, and the stress calculation value under each working condition of the finite element calculation is used as the independent variable. The multivariate regression coefficient matrix is ​​determined by the principle of least squares method, and then the regression initial stress of any point is obtained. In the calculation process, the influence of geological structure, rock mechanical properties, topography and other factors on the geostress distribution is fully considered. Through statistical analysis of a large amount of on-site geostress measurement data and finite element calculation results, the mathematical relationship between geostress and various influencing factors is established to achieve accurate inversion of the initial geostress field.

[0042] The distribution of the geostress field obtained by multivariate regression calculation is compared and verified with the measured geostress data on site. For example, the error between the measured geostress value and the fitted value at each measuring point is calculated to evaluate the fitting effect. In the geostress field inversion of Shuangjiangkou Hydropower Station, the geostress inversion analysis is performed based on the measured geostress, and the measuring points far from the calculation range are ignored to obtain the fitted geostress distribution map before construction excavation. After calculation, the maximum fitting error occurs at the measuring point The second principal stress component of SPD3-1 The difference is 1.794MPa. The fitted geostress field retains the characteristics of the measured geostress field, and the fitting complex correlation coefficient reaches 0.9024, indicating that the fitting effect is good and provides reliable initial geostress conditions for subsequent construction simulation and scheme optimization.

[0043] Inversion method of geostress field using generative adversarial network (GAN): Inversion of paleo-geostress field based on lateral stress coefficient: The paleo-geostress field is inverted using the lateral stress coefficient. The relationship between the lateral stress coefficient and the burial depth is determined according to the relevant formula. The approximate lateral stress coefficient is obtained through the measured geostress value, and then the approximate paleo-geostress field is constructed. This method is based on the basic principles of rock mechanics, takes into account the evolution of geostress in the geological history, and infers the magnitude and direction of paleo-geostress by analyzing the lateral stress coefficients of different burial depths, providing an important basis for the geomechanical history of the study area.

[0044] Based on the inversion of the present geostress field by GAN, GAN is introduced to optimize the present geostress field. GAN consists of a generator and a discriminator. They reach Nash equilibrium through mutual competition. The range of regression factor values ​​is determined based on uniform design experiments. Training samples are constructed and input into GAN training to obtain the optimized paleo-geostress field regression factor, thereby obtaining the optimized paleo-geostress field and the present geostress field. In this process, GAN can effectively learn the complex nonlinear relationship between the geostress field and geological parameters, continuously optimize the model through a large number of training samples, and improve the accuracy of geostress field inversion. Compared with the BP neural network, when GAN inverts the geostress field, the relative error of the stress component of the measuring point is smaller. For example, the maximum relative error of the GAN measuring point is 17.46%. The distribution law of the geostress field is more reasonable, which can more accurately reflect the distribution of the actual geostress, and provide more accurate geostress data support for engineering design and construction.

[0045] Equivalent mechanical parameters of faults and weak structural surfaces: Simplify the composite unit containing rock mass and faults into a layered transversely isotropic equivalent unit, determine the deformation and stress relationship of the equivalent unit in different directions, and the calculation formulas for parameters such as equivalent elastic modulus and Poisson's ratio. This step takes into account the significant influence of adverse geological bodies such as faults and weak structural surfaces on the mechanical properties of rock mass. Through the calculation of equivalent parameters, the mechanical behavior of these special geological structures can be more reasonably simulated in the numerical model, reducing the difficulty of numerical model modeling and calculation time, while improving the accuracy and reliability of the calculation results, making the analysis results of the geostress field closer to the actual engineering situation.

[0046] S6. Scheme optimization decision: Through numerical simulation analysis, the surrounding rock deformation, stress distribution and plastic failure zone distribution characteristics under different anchor cable layout schemes are analyzed to optimize the anchor cable layout scheme.

[0047] In a preferred solution, in step S6, the following steps are also included: S61. Deformation characteristics of surrounding rock: Using professional numerical simulation software FLAC3D, based on the accurate three-dimensional numerical model established in the early stage, the excavation process at all levels was simulated, and monitoring points were set at key parts of the model, including the top arch, bottom plate, and side wall, to accurately obtain the deformation data of each part. Furthermore, in the excavation of each level under working condition 1 (excavation without support): like Figure 7 and Figure 8 As shown in the figure, in the first level of excavation, the top arch of the installation section sinks 16.66mm. To calculate the total subsidence, follow these steps: Design calculation step number , the sinking increment of the top arch in each calculation step The average value is 0.1666mm, so the total sinking is 16.66mm.

[0048] in, is the sinking increment of the top arch within each calculation step, To calculate the total number of steps; The bottom plate is lifted by 15.54 mm, and the displacement change is calculated according to the corresponding cumulative formula.

[0049] The main building arch of the 1# unit section sank by 18.59 mm. Through statistical analysis of the displacement of each node in the model, it was found that the bottom plate was lifted by 18.29 mm, which was calculated based on the displacement vector of the corresponding node in the model.

[0050] The top arch of the main powerhouse of unit 2# sank by 21.26mm, which was obtained by accumulating the displacement data of each node of the top arch during the simulation process, and the bottom plate rose by 17.74mm, which was obtained by calculating the displacement of the bottom plate nodes.

[0051] The top arch of the main building of the 3# unit section sank 18.23mm, which was calculated based on the displacement of the top arch node of the model, and the bottom plate rose 19.52mm, which was obtained based on the statistical displacement changes of the bottom plate nodes.

[0052] The top arch of the main building of the 4# unit section sank 16.22mm. Through the analysis and calculation of the displacement of the top arch nodes, the bottom plate rose 22.05mm, which was calculated based on the displacement data of the bottom plate nodes.

[0053] As the excavation level increases, the deformation trend is analyzed in depth; Assume the excavation level is , the deformation is , by fitting the deformation data under different excavation levels, the quadratic function relationship determined by the least squares method is: ; Among them, multiple sets of arch sinking data with different excavation levels were fitted, and the parameters were determined by the least squares method. , , and study its relationship with excavation depth; but:

[0054] Considering the influence of rock mass mechanical properties on deformation, according to the previously determined rock mass parameters, including elastic modulus , Poisson's ratio , combined with the theory of elasticity, the relationship between deformation and mechanical properties of rock mass follows the formula: ; in, is the deformation amount, For external force, is the length, is the cross-sectional area; Furthermore, for a specific rock mass area, the external forces ,length , cross-sectional area And elastic modulus , Poisson's ratio , through the formula Calculate and analyze the deformation, then: ; As for the impact of ground stress release, the relationship between ground stress release and deformation is analyzed based on ground stress measurement data and stress changes in numerical simulations; Assume that the ground stress release is , there is a linear relationship between the deformation and the release of ground stress: ; Furthermore, the parameters were determined by statistically analyzing the monitoring data of the stress release and corresponding deformation in different regions. and , we get: ; In the preferred solution, the deformation differences of different parts are compared, for example, the deformation of some areas of the main plant upstream is greater than that of the downstream; Assume the upstream deformation is , the downstream deformation is , calculate the deformation difference: ; By comparing and analyzing the displacement data of corresponding upstream and downstream nodes in the model, the areas with large deformation differences are determined; The displacement of the downstream side wall of the auxiliary powerhouse is affected by the lamprophyre vein, and the elastic modulus of the vein is ,According to the displacement data of the side wall nodes in the numerical simulation, the influence of the dyke on the side wall deformation is analyzed. Due to the existence of the dyke, the side wall displacement increases by 5mm; Furthermore, due to the low elastic modulus of the dyke, the deformation coordination conditions of the surrounding rock mass change, thereby increasing the displacement of the side wall. By analyzing these deformation differences, we can gain a deep understanding of the influence of the rock mass heterogeneity and geological structure on the deformation of the surrounding rock, so that targeted measures can be taken during the scheme optimization process, such as adjusting the layout and direction of the anchor cables, and strengthening the support strength of the areas with larger deformation, so as to reduce the deformation difference and improve the overall stability of the surrounding rock.

[0055] S62, stress distribution characteristics: determine the stress concentration area of ​​the main cavern after each level of excavation, and compare the stress extreme value changes of the stress concentration area of ​​different schemes; In the preferred solution, the stress concentration area of ​​the main cavern after each level of excavation is determined by setting the stress threshold using the stress cloud map and data in the numerical simulation results; Furthermore, for the two arch ends of the main powerhouse, the arch ends of the tail adjustment room and the bottom corners of the cavern side walls, the stress value threshold is set. , these areas are identified as stress concentration areas. By screening and analyzing the stress data of each node in the model, the location and range of these stress concentration areas are clearly displayed, providing clear target areas for subsequent stress analysis and solution optimization.

[0056] Under the original anchor cable arrangement scheme, through statistical analysis of the numerical simulation results, it was determined that the stress concentration degree at the upstream arch end of the installation room was greater than that at the downstream arch end, with an extreme value of about 50 to 55 MPa; Assume that the maximum principal stress at the upstream arch end is , the minimum principal stress is , according to the calculation formula of stress concentration degree: , calculate the stress concentration degree; After optimizing the anchor cable layout, the numerical simulation calculation is re-performed by adjusting the anchor cable spacing, length, prestress and other parameters; Assuming that the stress extreme value of the upstream arch end of the installation room is reduced to about 48MPa after optimization, the change of stress concentration is analyzed according to the above stress concentration calculation formula. ; At the same time, by comparing the changes in the range of stress concentration areas, and through comparative analysis of stress extremes and concentration area ranges under different schemes, the improvement effects of different schemes on stress distribution can be intuitively evaluated, providing a key basis for selecting the optimal scheme.

[0057] S63, distribution characteristics of plastic failure zone: obtain the depth of plastic failure zone of surrounding rock of each unit; Extract the depth data of the plastic failure zone of surrounding rock of each unit from the numerical simulation results; Furthermore, the depth of the plastic failure zone of the top arch of the installation room section is about 1.85m shallow plastic failure zone; For the main building of the 2# unit section affected by fault f1, the depth of the plastic failure zone at the top arch is about 2.29m. According to the location and mechanical properties of the fault and the distribution of plastic strain in the numerical simulation, the depth of the plastic failure zone near the fault is determined. Similarly, the depth of the plastic failure zone at the top arch of the main powerhouse of Unit 3 is about 6.61m, which reflects the degree and scope of damage to the surrounding rock during the excavation process, and is of great significance for evaluating the stability of the surrounding rock and the effectiveness of the support scheme.

[0058] Analyze the relationship between the range of the plastic failure zone and the stability of the surrounding rock. According to rock mechanics theory, the expansion of the plastic failure zone will lead to a decrease in the strength of the surrounding rock and a deterioration in stability. Assume that the range of plastic failure zone is The surrounding rock stability index is , through statistical analysis of the range of plastic failure zone and surrounding rock stability index under different schemes, a negative correlation is obtained: ; Among them, the range data of plastic failure zone and the corresponding surrounding rock stability index data under multiple different schemes are obtained, and the parameters are determined by fitting analysis of the data. ; Generally speaking, the smaller the plastic failure zone is, the higher the stability of the surrounding rock is. By comparing the changes in the plastic failure zone under different schemes, such as in the optimization scheme, the depth and range of the plastic failure zone can be effectively controlled by reasonably arranging anchor cables, thereby improving the stability of the surrounding rock and providing an important reference for determining the optimal scheme.

[0059] S64, scheme determination and verification: determine the three-dimensional numerical model under different anchor cable arrangement schemes according to the surrounding rock deformation characteristics, stress distribution characteristics and plastic failure zone distribution characteristics, and perform excavation simulation calculation based on the three-dimensional numerical model under different anchor cable arrangement schemes to obtain surrounding rock deformation results, stress distribution results and plastic failure zone results; Taking all the above factors into consideration, an evaluation index system for surrounding rock stability is established; Furthermore, the weighted average method is used, and the deformation weight is set to , the stress weight is , the weight of the plastic failure zone is ; in, It can be determined based on the ratio of deformation to allowable deformation, and the formula is as follows: ; In the anchor cable arrangement scheme, the actual deformation is obtained by monitoring , the allowable deformation determined according to engineering specifications and experience ,but .

[0060] It can be determined based on the ratio of stress concentration to allowable stress concentration. The formula is as follows: ; In a certain area, the actual stress concentration , the allowable stress concentration level determined based on rock mass strength theory and engineering experience ,but .

[0061] It can be determined based on the ratio of the plastic failure zone range to the allowable plastic failure zone range. The formula is as follows: ; Assume that the actual plastic failure zone range , the allowable plastic failure zone range determined according to engineering specifications and experience ,but .

[0062] Substitute the above calculation results into the surrounding rock stability index formula: ; We can get: .

[0063] Through different schemes Compare the values ​​and determine the best solution; Specifically, different anchor cable layout schemes are calculated to obtain their respective Value, further, the first option , Option 2 , Option 3 .

[0064] By comparison, select The solution with the largest value is the optimal solution, namely Solution 3. At the same time, the specific layout parameters of the anchor cables in the optimal solution are clarified, including the anchor cable spacing of 3m, length of 25m, angle of 25°, and layout position at the arch foot of the main factory building.

[0065] Verification and feedback: Obtain the deformation, stress distribution and damage zone of on-site monitoring. By arranging monitoring instruments at the project site, including multi-point displacement meters, stress meters, and ultrasonic detectors, the actual deformation, stress and damage data of the surrounding rock can be obtained in real time.

[0066] Compare the surrounding rock deformation results, stress distribution results and plastic failure zone results with the deformation, stress distribution and failure zone conditions monitored on site; The root mean square error (RMSE) formula is used to calculate the error between the two. Assume that the deformation data sequence obtained by simulation is ,in, is the number of data points, and the deformation data sequence obtained by monitoring is , the stress value data series is and ,in, is the number of stress data points, and the data series of the depth of the plastic failure zone is and ,in, is the number of data points in the plastic failure zone.

[0067] Multi-point displacement meters, stress meters, acoustic wave detectors and other monitoring instruments are arranged at the project site to obtain the actual deformation, stress and damage data of the surrounding rock in real time. In a certain period of time, the deformation data sequence monitored by the multi-point displacement meter is (Unit: mm), the stress value data sequence monitored by the strain gauge is (Unit: MPa), the data sequence of the depth of the plastic failure zone monitored by the acoustic wave detector is (Unit: m).

[0068] Calculate the root mean square error of the deformation: ; The deformation data sequence obtained by numerical simulation is Substituting in, then: ; Calculate the RMS error of stress: ; The deformation data sequence obtained by numerical simulation is Substituting in, then: ; Calculate the root mean square error of the plastic failure zone depth: ; The deformation data sequence obtained by numerical simulation is Substituting in, then: ; Taking these three RMS error values ​​into consideration, a total RMS error can be obtained by weighted average method. ; Assume that the weights of deformation, stress, and depth of plastic failure zone are , and satisfies , then according to the root mean square error formula , we can get: ; According to the comparison results, an error correction model of the evaluation method is established. If it is large, it means that there is a large deviation between the simulation results and the actual situation, and the parameters in the numerical model need to be adjusted.

[0069] Suppose the parameters to be adjusted are , in order to determine and , collect multiple sets of different parameter values The corresponding The data is shown in the following table: Table 4

[0070] The least squares method is used to fit and The value of , and according to the principle of least squares, establish the equation system: ; in, is the number of data sets, substitute the data in Table 1,

[0071] ; in, , we can get: ; The calculation can be obtained: ; ; ; Substituting the above values ​​into the equations, we get: ; Solving the system of equations yields: From the first equation in the system of equations, we can get , and substitute it into the second equation in the system: ; ; ; ; ; Will Substitution , we can get: ; When a simulation is obtained According to the established linear relationship: , the parameters can be inferred The correction amount : ; in, Get the value of the current parameter; If the current parameter When, according to the formula: , we can get:

[0072] The parameters Adjusted to: , again conduct numerical simulation and compare with the field monitoring data; Repeat the above process and continuously optimize the parameters until the error index of the root mean square error meets the accuracy range required by the project.

[0073] In addition, the influence of different parameters on the error can be further analyzed, and the error change rate corresponding to each parameter value can be calculated, that is: , to determine the impact of parameter adjustment on the error. If the change of a certain parameter has a greater impact on the error, more attention should be paid to the adjustment of this parameter in the subsequent optimization process, so as to achieve continuous improvement and perfection of the evaluation method and anchor cable layout plan, improve the quality and safety of engineering construction, and ensure the long-term stable operation of the underground cavern group.

Claims

1. A method for evaluating the quality of prestressed anchor cable construction layout, characterized in that: The following steps are involved: S1. Basic data preparation: obtain and preprocess the geological survey data of the underground cavern group, and establish a three-dimensional numerical model based on the preprocessed geological survey data; S2. Model basic setting: determine the surrounding rock types in different areas according to geological survey data, determine the rock mass parameters based on the surrounding rock types, and select the constitutive model according to the surrounding rock parameters, including the elastic-plastic model and the stress-crack strain evolution constitutive model; S3. Model characteristics research: obtain the mechanical characteristic parameters of the rock mass through specific test methods, establish the stress-crack strain evolution constitutive model, analyze the crack evolution law, determine the criteria for the surrounding rock relaxation zone, and conduct secondary development of the constitutive model; S4. Engineering construction simulation: simulate the excavation sequence design based on the graded excavation scheme, analyze the anchor support strength, determine the support parameters and evaluate them; S5. Geostress field analysis: The initial geostress multivariate regression method and the geostress field inversion method of the generative adversarial network (GAN) are used to calculate the stress state of the surrounding rock before construction and excavation and determine the mechanical parameters. S6. Scheme optimization decision: Through numerical simulation analysis, the surrounding rock deformation, stress distribution and plastic failure zone distribution characteristics under different anchor cable layout schemes are analyzed to optimize the anchor cable layout scheme.

2. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 1, characterized in that: In step S1, the geological survey data includes physical and mechanical parameters of the rock mass, ground stress measurement data, and structural surface characteristics; Among them, the physical and mechanical parameters of rock mass include natural density, deformation modulus, Poisson's ratio, and shear strength; The preprocessing operation is to sort and screen the collected geological survey data, remove abnormal data and normalize them for model input and calculation; A three-dimensional numerical model of the main chambers including the installation room, main and auxiliary powerhouse caverns, main transformer room, and tailwater surge chamber is established based on the pre-processed geological survey data; The three-dimensional numerical model uses three-dimensional 8-node hexahedron isoparametric solid elements and their degenerate elements to simulate rock mass and faults. The overall model has 91479 solid element nodes, 181231 solid elements, 51803 anchor element nodes, and 26089 anchor elements.

3. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 2, characterized in that: In step S2, the physical and mechanical parameters of the rock mass are calculated according to the empirical formula to obtain the rock mass parameters, and the calculated rock mass parameters are corrected in combination with engineering experience and field monitoring data; Among them, the elastic-plastic model determines the cracking conditions of rock materials through macroscopic strength, and determines that the rock mass enters the plastic state based on the Druker-Prager criterion; When the constitutive model is applied to the three-dimensional numerical model, the deformation, stress distribution and failure characteristics of the surrounding rock are analyzed by setting the parameters of the constitutive model and the boundary conditions of the three-dimensional numerical model and performing numerical simulation calculations using specific methods; Among them, the parameter settings of the constitutive model include the yield stress and hardening parameters of the elastic-plastic model and the crack closure and expansion parameters of the stress-crack-strain evolution constitutive model.

4. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 1, characterized in that: In step S3, the mechanical property parameters of the rock mass include peak stress, elastic modulus, and Poisson's ratio, and the specific test method is selected as a triaxial compression test. Through rock sample preparation and test loading, the stress-strain curve, threshold stress, elastic modulus and Poisson's ratio, stress-crack strain evolution constitutive model, crack evolution law, and surrounding rock relaxation zone criterion are analyzed, and the constitutive model code is compiled and verified in FLAC3D. The specific steps are as follows: Collect rock samples and use a rock triaxial testing machine; And the peak stress is , confining pressure , confining pressure The value range of is: MPa, and MPa, loading rate is confining pressure Loading was performed at 0.05 MPa / s, and the axial load was increased at 0.5 MPa / s until the rock sample failed; Peak stress With confining pressure Increases and increases, the peak stress Confining pressure The relationship between is expressed by the formula as follows: ； Assume that the threshold stresses are the crack closure stress , crack initiation stress , crack damage stress ; The relationship between the ratio of threshold stress to peak strength Rcc d, Rci d and Rcd d and the confining pressure can be fitted by the following formula: ； Among them, a, b, c, and d are fitting parameters.

5. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 4, characterized in that: By fitting the rock sample test data under multiple confining pressures, different confining pressures The corresponding peak stress They are 114.72MPa, 139.65MPa, 157.22MPa, 182.97MPa, 216.30MPa, 345.73MPa and 374.63MPa respectively; Through different confining pressure Lower crack closure stress , crack initiation stress , crack damage stress Different from the ratio of the peak intensity, the values ​​of Rcc d, Rci d and Rcd d are 0.22 respectively. , 0.41 and 0.78 , and with the confining pressure Increase and gradually decrease.

6. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 5, characterized in that: In step S3, the specific test method is selected as the creep test, and the multi-step loading method is adopted. Through the rock sample parameters and the test method settings, the creep strain, stress and instantaneous strain, the constitutive relationship of creep strain, long-term strength and creep strain rate are analyzed, and the Nishihara creep model is improved to verify the correctness of the initial parameters. The specific steps are as follows: Confining pressure The value is MPa, the axial stress value is 0.55-1.00 times the peak strength; The axial creep strain increases with time and is more obvious at high deviatoric stress levels. The total strain consists of instantaneous strain and creep strain. The creep strain includes viscoelastic creep strain and viscoplastic creep strain. By analyzing the creep strain data under different confining pressures and deviatoric stresses, the instantaneous strain and deviatoric stress-peak strength ratio The relationship can be expressed as: ； Viscoelastic creep strain and The relationship can be expressed as: ； Viscoplastic creep strain Confining pressure The relationship can be expressed as: ； in, , , , is a variable.

7. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 6, characterized in that: In step S4, the hierarchical excavation plan includes excavation sequence, anchor support strength analysis, support parameters and evaluation; Among them, the excavation sequence is simulated according to the actual construction process, the anchor support strength analysis is based on the indoor test results and field monitoring data, and the support parameters and evaluation are combined with theoretical analysis and numerical simulation results; The cohesion increment of the surrounding rock of the prestressed anchor cable support is calculated and compared with the value calculated by the empirical formula to determine whether the support strength is sufficient.

8. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 7, characterized in that: In step S6, the following steps are also included: S61. Deformation characteristics of surrounding rock: Obtain the deformation of each part of the cave body during each level of excavation, and analyze the changing trend of the deformation under each level of excavation and the deformation differences of different parts; S62, stress distribution characteristics: determine the stress concentration area of ​​the main cavern after each level of excavation, and compare the stress extreme value changes of the stress concentration area of ​​different schemes; S63, distribution characteristics of plastic failure zone: obtain the depth of plastic failure zone of surrounding rock of each unit; S64. Determine the three-dimensional numerical model under different anchor cable arrangement schemes according to the deformation characteristics, stress distribution characteristics and plastic failure zone distribution characteristics of the surrounding rock, and perform excavation simulation calculation based on the three-dimensional numerical model under different anchor cable arrangement schemes to obtain the surrounding rock deformation results, stress distribution results and plastic failure zone results.

9. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 8, characterized in that: In step S64, the surrounding rock stability under different anchor cable arrangement schemes is determined according to the surrounding rock deformation results, stress distribution results and plastic failure zone results, and the optimal scheme is determined according to the surrounding rock stability under different anchor cable arrangement schemes.

10. The method for evaluating the construction layout quality of prestressed anchor cables according to claim 9, characterized in that: Obtain deformation, stress distribution and damage zone conditions from on-site monitoring; The surrounding rock deformation results, stress distribution results and plastic failure zone results are compared with the deformation, stress distribution and failure zone conditions monitored on site, and the statistical analysis method is used for quantitative evaluation to obtain the comparison results; Wherein, the statistical analysis method is one of the root mean square error or correlation coefficient; An error correction model of the evaluation method is established based on the comparison results, which is used to pre-adjust the parameters under different anchor cable layout schemes.

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