Main power house anchor rod construction arrangement quality evaluation method

Abstract

The invention provides a main power house anchor rod 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 through comprehensive integration of geological survey data, deep analysis of surrounding rock lithology, joint fissure trend and ground stress distribution, comprehensive consideration of the physical characteristics of the anchor rod, and close combination of key indexes of construction links;

Description

Technical Field

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

[0002] In the construction of large-scale underground projects, such as the excavation of the underground powerhouse of Shuangjiangkou Hydropower Station, support design is crucial to ensuring the safety and economy of the project. The support design of the remaining excavation layer of the main powerhouse directly affects the progress, cost and stability of the entire project. Among them, the system anchor is one of the main support means, and the selection of its length needs to comprehensively consider multiple factors.

[0003] At present, with the advancement of the project, the overall stability of the surrounding rock is good, which provides certain conditions for optimizing the support design. However, under the premise of ensuring the safety of the project, there is currently a lack of systematic and accurate quality assessment methods for the assessment of the quality of the anchor construction layout of the main powerhouse. It is difficult to comprehensively and scientifically judge whether the anchor layout is reasonable and whether it can effectively ensure the safety and stability of the main powerhouse. Summary of the invention

[0004] 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 quality of anchor rod construction layout in the main factory building, which can evaluate the layout quality of anchor rods at different construction stages in real time, and effectively solve the problems of insufficient consideration of construction process factors and difficulty in dynamic evaluation in the existing methods.

[0005] 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 quality of anchor bolt construction arrangement of a main plant, comprising the following steps: S1. Model construction: Establish three-dimensional numerical models of different anchor arrangement schemes; S2. Simulation calculation and result evaluation: Perform excavation simulation calculation based on the three-dimensional numerical model of different anchor arrangement schemes to obtain the numerical simulation calculation results of surrounding rock deformation, stress distribution, damage and rupture zone distribution and support structure stress; Evaluate the numerical simulation results of different anchor arrangement schemes, obtain evaluation indicators, and determine the optimal scheme based on the evaluation indicators; S3. Error value analysis: Compare the numerical simulation calculation results with the on-site monitoring data according to the optimal solution to obtain the comparison results, and calculate the error rate of each evaluation index based on the comparison results; S4. Establish a comparison model: establish an error correction model for the evaluation method based on the comparison results, and adjust the parameters in the numerical model based on the deviation between the numerical simulation calculation results and the field monitoring data.

[0006] In a preferred solution, in step S2, the deformation of the surrounding rock under different anchor arrangement schemes, including the top arch settlement and side wall displacement, is compared to evaluate the deformation control effect.

[0007] Analyze the stress state of the surrounding rock under different anchor arrangement schemes, including the degree of stress concentration and uniformity of stress distribution, and evaluate the improvement of the stress state; Analyze the distribution characteristics of the surrounding rock damage and fracture zones under different bolt arrangement schemes, including the location, size and shape of the damage zone and the range of the strong relaxation zone and the weak relaxation zone, and evaluate the control effect of the expansion of the surrounding rock damage and fracture zones; Analyze the internal force distribution of anchor rods under different anchor rod arrangement schemes, including the maximum internal force of anchor rods and the law of internal force distribution, and evaluate the internal force distribution of anchor rods.

[0008] In a preferred solution, in step S3, the numerical simulation calculation results are compared with the on-site monitoring data to verify the accuracy and reliability of the evaluation method. The specific comparison content includes: Deformation comparison: Compare the surrounding rock deformation under the action of anchor bolts calculated by numerical simulation with the deformation monitored on site, including deformation at different locations and different excavation levels; Stress comparison: Compare the surrounding rock stress distribution under the action of anchor bolts calculated by numerical simulation with the stress distribution monitored on site to verify the accuracy of stress calculation; Comparison of damage zones: Compare the distribution of surrounding rock damage zones under the action of anchor bolts calculated by numerical simulation with the damage zones monitored on site to evaluate the accuracy of damage zone prediction.

[0009] In the preferred solution, the error rate formulas for deformation comparison, stress comparison and damage zone comparison are expressed as follows: The deformation error calculation formula is: ; The deformation error rate calculation formula is: ; The stress error calculation formula is: ; The stress error rate calculation formula is: ; The error calculation formula is: ; The error rate calculation formula is: ; The deformation error rate calculation formula, stress error rate calculation formula and depth error rate calculation formula can be used to quantify the difference between the simulation calculation results and the on-site monitoring data. By calculating the difference, the degree of numerical deviation between the simulation value and the monitoring value can be obtained.

[0010] In a preferred solution, in step S4, the following steps are also included: S41, analyzing the deformation error rate, stress error rate and depth error rate under different anchor arrangement schemes, and adjusting the parameters in the three-dimensional numerical model; Among them, if the deformation calculated by simulation is large as a whole, it means that the value of rock mass deformation modulus is too high and the deformation modulus parameter should be reduced; If the stress calculation error is large, it means re-evaluating the initial geostress field parameters or the parameters of the interaction between the anchor and the rock mass; S42. Establish an error correction model by analyzing data from multiple monitoring points and different excavation stages.

[0011] In a preferred solution, in step S42, the specific steps of establishing the deformation error correction model are as follows: Assume that the deformation value of the on-site monitoring is The simulated deformation value is , the correction formula is obtained by data fitting: ; in, and is the fitting coefficient; Calculated based on data from multiple monitoring points and The value of is fitted by the least square method, so that The deformation correction model is obtained by substituting the simulation calculation results into the deformation correction model to obtain the corrected deformation value, and the deviation between the simulation calculation value and the on-site monitoring deformation value is corrected according to the corrected deformation value.

[0012] In a preferred solution, in step S42, the specific steps of establishing the stress error correction model are as follows: The stress value monitored on site is The simulated stress value is , the correction formula is obtained by data fitting: ; in, and is the fitting coefficient; Collect stress data from multiple monitoring points and calculate them using the least squares fitting method. The present invention provides a method for minimizing the deviation between the simulated calculation value and the on-site monitored stress value by substituting the simulation calculation result into the stress correction model to obtain a corrected stress value.

[0013] The present invention provides a method for evaluating the quality of anchor bolt construction arrangement in a main plant, which has the following beneficial effects through the cooperation between the above structures: First, it can comprehensively improve the accuracy of the assessment by integrating geological survey data in all aspects, deeply analyzing the lithology of the surrounding rock, the direction of joints and fissures, and the distribution of ground stress, and comprehensively considering the physical properties of the anchor rods themselves. It is closely combined with the key indicators of the construction process, and a comprehensive assessment system is constructed. Data analysis models and algorithms are used to convert the data into intuitive and quantitative assessment results.

[0014] Second, by establishing an error correction model, the deviation between numerical simulation and on-site monitoring data can be accurately calibrated, providing a reliable basis for optimizing the anchor support scheme and ensuring the stability of the surrounding rock of the main plant, effectively improving the scientificity and accuracy of engineering design and construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 It is the contour map of the first-level excavation displacement Uz of the installation room of the present invention; Figure 2 It is the contour map of the first-level excavation displacement Uy of the installation room of the present invention; Figure 3 It is the contour map of the first-level excavation stress σ1 of the installation room of the present invention; Figure 4 It is the contour map of the first-level excavation stress σ3 of the installation room of the present invention; Figure 5 This is a diagram of the damage mode of the surrounding rock of the first-level excavation of the installation room of the present invention; Figure 6 The present invention is the first stage under different confining pressure C 1. C 3 and R d The relationship curve diagram of Figure 7 is a schematic diagram of the pseudo-viscous unit of stage I of the present invention; Figure 8 The crack closure degree under σ3 = 1MPa of the present invention is R d The relationship curve diagram between ; Fig. 9 is a graph showing the relationship between the four types of stress thresholds and the confining pressure of the present invention; Fig.10 It is a relationship curve diagram of Rcc d, Rci d, Rcd d and confining pressure of the present invention. DETAILED DESCRIPTION

[0016] 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.

[0017] Example like Figures 1 to 10 As shown, this embodiment provides a method for evaluating the quality of anchor bolt construction arrangement in a main plant, comprising the following steps: S1. Model construction: Establish a three-dimensional numerical model of different anchor arrangement schemes. The specific steps are as follows: S11. According to the actual situation of the underground powerhouse of Shuangjiangkou Hydropower Station, the following different anchor arrangement schemes are designed for numerical model construction: Option A: Anchor spacing: 1.2m×1.2m (longitudinal×transverse).

[0018] Layout position: Evenly arranged from the top arch to the bottom of the side wall.

[0019] Anchor rod internal force: The internal force of the prestressed anchor rod is 100kN, and the diameter of the ordinary mortar anchor rod is 28mm.

[0020] Option B: Anchor spacing: 1.5m×1.5m (longitudinal×transverse).

[0021] Layout position: The top arch is arranged densely, the middle part of the side wall is appropriately sparse, and the bottom is densely arranged.

[0022] Anchor rod internal force: The internal force of the prestressed anchor rod is 120kN, and the diameter of the ordinary mortar anchor rod is 32mm.

[0023] Option C: Anchor spacing: 1.8m×1.8m (longitudinal×lateral).

[0024] Layout position: The top arch and the bottom of the side walls are densely packed, and the middle part is evenly arranged.

[0025] Anchor rod internal force: The internal force of the prestressed anchor rod is 150kN, and the diameter of the ordinary mortar anchor rod is 36mm.

[0026] S12. Model parameter setting Effect of deformation modulus and Poisson's ratio According to the elastic theory, the relationship between the deformation and stress of the rock mass can be expressed by the elastic modulus. and Poisson's ratio To describe. In FLAC 3D When performing simulation calculations in software such as , these parameters are important factors affecting rock deformation and stress distribution.

[0027] According to the following table 1, the physical and mechanical parameters of the rock mass corresponding to different surrounding rock types are obtained, such as the natural density of slightly fresh granite intercalated with granite fine crystals, pegmatite veins, massive and sub-massive rock mass. , deformation modulus , Poisson's ratio , the initial geostress field data are obtained by inversion using the multivariate regression method or the GAN method, such as the major principal stress in the installation area is about 28.0-30.0MPa, and the minor principal stress is about 12.0-14.0MPa. Using FLAC 3D The software builds a three-dimensional numerical model; Table 1 Recommended values ​​of physical and mechanical properties of surrounding rock in underground caverns

[0028] In the numerical model, the material properties of the rock mass are set according to these parameters and used to calculate the deformation and stress response of the rock mass during excavation.

[0029] Through model calculation, the deformation and stress distribution of the rock mass after excavation under different anchor arrangement schemes can be obtained. These results are compared with the field monitoring data to evaluate the accuracy of the model.

[0030] Initial geostress field: The geostress field data obtained by inversion using the multivariate regression method or the GAN method are used. For example, the major principal stress in the installation area is about 28.030.0MPa, and the minor principal stress is about 12.014.0MPa.

[0031] Specifically, the calculation steps of the multiple regression method are as follows: When the initial geostress field is inverted using the multivariate regression method, the geostress regression calculation value As the dependent variable, the stress calculation value corresponding to the measured point under various working conditions (self-weight stress calculation, boundary load, etc.) obtained by finite element calculation is used. As the independent variable, the regression stress It can be regarded as a linear combination of stress calculations of various working conditions, and the formula is: ; in, is the multiple regression coefficient; For the least squares residual sum of squares , and its calculation formula is: ; in, is the total number of observation points, is the observation point number, is the total number of working conditions, To calculate the number of operating conditions, is the number of stress components, For the Observation point The regression calculation value of the ground stress component is For the Observation point Measured values ​​of the ground stress components.

[0032] According to the principle of multiple regression method, representative ground stress measurement points are selected for finite element calculation to obtain the stress calculation values ​​under various working conditions. .

[0033] Using the least squares method, the residual sum of squares is the minimum value, by solving the equation: ; in, is the design matrix, is the multivariate regression coefficient matrix, is the observed value vector, and the multivariate regression coefficient matrix is ​​obtained .

[0034] Any point The regression initial stress is: ; The distribution characteristics of the initial geostress field obtained by inversion are basically consistent with the measured geostress field. The extreme value of the first principal stress at each measuring point basically increases with the increase of burial depth, and the value fluctuates between 14.88MPa and 37.82MPa.

[0035] The GAN inversion method is used to calculate the paleo-stress field based on the lateral stress coefficient. The specific steps are as follows: Lateral stress factor and stress components The relationship is: ; in, For the stress components, is the volume density, For burial depth.

[0036] However, the current geostress field is affected by the terrain undulation and the physical and mechanical properties of the rock mass, resulting in large variations in the geostress coefficient at different locations. However, the topography and landforms in ancient times were small and the geological structure was not complex. Therefore, it is more appropriate to use the lateral stress coefficient to invert the ancient geostress field.

[0037] The lateral stress coefficient at each location in the rock mass is a fixed value, which means that the stress component increases linearly with the increase of burial depth. However, for deep buried projects, the lateral stress coefficient is not linearly related to the burial depth. Brown and Hoek found that the relationship between the lateral stress coefficient and the burial depth is: ; in, , and They are the maximum principal stress, minimum principal stress and vertical principal stress in the horizontal plane respectively.

[0038] Through statistical analysis of the lateral stress coefficients of different rock masses, it is found that for deep buried projects, the relationship between the lateral stress coefficient and the burial depth is: ; in, and is the regression factor.

[0039] From the field survey data, the stress values ​​of the measured points are statistically analyzed, and effective measuring points are selected to determine the approximate lateral stress coefficient according to the above formula. .

[0040] Based on uniform design experiments, and Set the floating range and design multiple and The paleo-stress field of the value.

[0041] According to multiple paleo-stress fields, FLAC 3D Excavation of the strata is carried out to obtain multiple present initial stress fields, from which the lateral stress coefficient at the present burial depth is determined.

[0042] Inversion of current geostress field based on GAN The objective function of GAN is: ; in, Represents the discriminator for the real data The probability of discrimination, Represents the data generated by the discriminator to the generator The probability of discrimination, is the actual data distribution, is a random variable distribution.

[0043] The measurement points in the underground cavern and its surroundings, as well as the measurement points near the boundary of the numerical model, were selected as samples to determine the formula The floating range of the regression factors in .

[0044] Each regressor or The value range of is between 0.5 and 1.5 times of itself. 12 regression factors are taken as factors of uniform design test. Different regression factor values ​​are regarded as different levels. According to the principle of uniform design, the regression factor has 13 levels. Then, the 1st to 13th levels correspond to the regression factor 0.52, 0.60, 0.68, 0.76, 0.84, 0.92, 1.00, 1.08, 1.16, 1.24, 1.32, 1.40, 1.48 times, as shown in Table 2. The regression factors of each test can be substituted into the formula and Calculate the stress components of each element and import them into FLAC 3D Calculations are performed. In each test, the calculated stress components and lateral stress coefficients of the measured points can be obtained. There are 8 valid measurement points, so 8 training samples can be created for each test, for a total of 13×8=104 samples.

[0045] Table 2 Different level factors in U13 uniform design experiment

[0046] Use real data to train samples. After training, enter the x and y coordinates, enter the current burial depth and lateral stress coefficient of the measuring point in the current stress field of the measuring point, and you can get the regression factor of the paleostress field. After GAN training, you can predict the regression factor of the optimized paleostress field and get the optimized and value, and then optimize the ancient geostress field, and obtain the optimized current geostress field through excavation.

[0047] Table 3 Regression factors of paleo-stress field obtained using GAN and BP neural network

[0048] Table 4 Stress component values ​​of each measuring point based on GAN and BP neural network

[0049] The regression factors and calculated stress values ​​of the measuring points are listed in Tables 3 and 4. It can be calculated as: ; in, is the calculated stress component, is the measured stress component, is the 2-norm.

[0050] For a composite unit with both rock mass and fault, the deformation and stress relationship of the equivalent unit in the z' direction is: ; in, and are the equivalent elastic moduli of rock mass and fault in z' direction, and are the thickness of the rock mass and fault, respectively. and are the stresses applied on the equivalent element, rock mass and fault in the z´ direction, respectively.

[0051] Equivalent elastic modulus in z´ direction for: ; in, and are the equivalent Poisson's ratios of the rock mass and fault, respectively.

[0052] Equivalent Poisson's ratio It can be expressed as: ; Divide the rock mass into hexahedral units, and for the units cut by faults, determine the relevant parameters of the rock mass and faults, such as layer thickness and , elastic modulus and , Poisson's ratio and wait.

[0053] According to the above formula, the equivalent elastic modulus of the equivalent unit in the z' direction is calculated and the equivalent Poisson's ratio .

[0054] The distribution law of the current geostress field obtained by the GAN inversion method is reasonable, and the fitting effect is good with the measured geostress field, and the fitting complex correlation coefficient reaches 0.9024.

[0055] S13. Model building Using FLAC 3D The software establishes a three-dimensional numerical model. The model range and typical geological profiles are in accordance with the relevant provisions of Chapter 2 of the document. For example, the calculation range has a total length of 275.7m in the X direction (from 0098.82 on the factory horizontal axis to 0+176.88 on the factory horizontal axis), a total length of 300.0m in the Y direction, and 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.

[0056] S2. Simulation calculation and result evaluation: Perform excavation simulation calculation based on the three-dimensional numerical model of different anchor arrangement schemes to obtain the numerical simulation calculation results of surrounding rock deformation, stress distribution, damage and rupture zone distribution and support structure stress; Evaluate the numerical simulation results of different anchor arrangement schemes, obtain evaluation indicators, and determine the optimal scheme based on the evaluation indicators; The preferred solution is Figures 1 to 4 As shown, the simulation is carried out according to the excavation sequence of the underground powerhouse in Table 5. For example, the first level of excavation is carried out first, i.e., the excavation of the A layer of the main powerhouse, the excavation of the a and b layers of the tail adjustment room, etc., and then the subsequent levels of excavation are carried out in sequence until the designed excavation state is reached.

[0057] Table 5 Graded excavation table of Shuangjiangkou underground powerhouse

[0058] Calculation result acquisition: During and after the excavation process, obtain the surrounding rock deformation, stress distribution and other results. Furthermore, record the cave displacement contour map, principal stress distribution information and surrounding rock plastic failure mode map at different excavation levels under each scheme, similar to the relevant data display in the calculation results of each excavation level of Working Condition 1 in Chapter 6 of the document.

[0059] S21. Deformation index evaluation Comparison of top arch sinking: Plan A: After the first level of excavation, the average settlement of the main powerhouse arch is about 18 mm (according to the value range of the simulation results). As the excavation level increases, after the fifth level of excavation, the arch settlement increases to 25 mm.

[0060] Plan B: After the first level of excavation, the average settlement of the main factory building arch is about 16mm, and after the fifth level of excavation, it increases to 23mm.

[0061] Plan C: After the first level of excavation, the average settlement of the main factory building arch is about 20mm, and after the fifth level of excavation, it increases to 27mm.

[0062] Assuming that the arch subsidence is obtained through the displacement data statistics of the monitoring points, multiple monitoring points are set in the model, and the vertical displacement values ​​of each monitoring point at different excavation stages under different schemes are recorded, and the average value is taken to obtain the above results.

[0063] Side wall displacement comparison: Plan A: After the first level of excavation, the upstream side wall of the main power building displaced into the tunnel by an average of about 15 mm, and the downstream side wall displaced by about 12 mm. After the fifth level of excavation, the displacement of the upstream side wall increased to 30 mm, and the downstream side wall increased to 25 mm.

[0064] Plan B: The side wall displacements at the corresponding positions are approximately 13mm and 10mm respectively. After the 5th level of excavation, the displacement of the upstream side wall increases to 28mm, and the downstream side wall increases to 23mm.

[0065] Scheme C: The side wall displacements are approximately 18 mm and 14 mm respectively. After the fifth level of excavation, the displacement of the upstream side wall increases to 35 mm, and that of the downstream side wall increases to 30 mm.

[0066] By monitoring the horizontal displacement monitoring points at different positions of the side wall, the displacement data of each monitoring point under different schemes were counted to obtain the average value. By comparison, it can be seen that Scheme B is relatively good in controlling the top arch sinking and side wall displacement.

[0067] S22. Stress Index Evaluation Stress concentration degree: Plan A: After the first level of excavation, the stress concentration at the arch end of the main powerhouse is relatively high, and the stress in the local area reaches about 45MPa (based on the value range of the simulation results).

[0068] Scheme B: The stress concentration at the arch end is relatively low, and the maximum stress value is about 42MPa.

[0069] Plan C: The stress concentration at the arch end is relatively high, with the local stress reaching about 48MPa.

[0070] As the excavation progresses, the stress concentration area changes, but Scheme B always maintains a relatively low stress concentration level.

[0071] Extract the stress values ​​of the key units at the arch end of the main powerhouse in the model, analyze the stress distribution, and determine the stress concentration area and extreme value. Stress calculation is based on the mechanical equilibrium equation and material constitutive relationship of the model, and is performed in FLAC 3D Automatically calculated in the software.

[0072] The stress distribution uniformity can be quantitatively evaluated by using indicators such as stress variation coefficient. ; in, is the stress standard deviation, To obtain the average stress, calculate the stress variation coefficient under different schemes and compare their sizes. The smaller the coefficient, the more uniform the stress distribution.

[0073] By analyzing the uniformity of surrounding rock stress distribution under different schemes, it is found that the stress distribution of scheme B is relatively uniform, while schemes A and C have stress mutation phenomena in some parts.

[0074] S23. Distribution characteristics of damage and rupture zone Failure mode: Figure 5 As shown in the figure, during the excavation process, the failure modes of the surrounding rock under different schemes are different; In scheme A, the depth of the plastic failure zone of the top arch is relatively shallow, and it is mainly superficial plastic failure; In Scheme B, the damage to the top arch and side walls is relatively concentrated, but the degree is relatively light; In Scheme C, the failure zone is deeper and obvious shear failure occurs in some parts.

[0075] As the excavation level increases, the damage range of each scheme gradually expands. Scheme B is relatively good in controlling the damage range and can effectively reduce the damage degree of the surrounding rock. The specific steps are as follows: Criteria for surrounding rock relaxation zone Criteria based on crack closure: radial crack expansion is the main cause of rock volume expansion. It can reflect the characteristics of the volume expansion of the rock mass in the radial direction. According to the document content, the surrounding rock unloading relaxation zone is based on The values ​​are divided into five zones, namely the destruction zone, strong relaxation zone, weak relaxation zone, stress disturbance zone and original rock zone. The specific criteria are as follows: when When the surrounding rock is damaged, it needs to be supported immediately.

[0076] for The surrounding rock allows the tangential and radial stresses of the rock mass to be further released. The inflection point is determined by the change curve of the value and is regarded as the optimal support time.

[0077] Combined with the actual engineering support method, the surrounding rock is divided into three areas: the arch, the upstream side wall, and the downstream side wall. If there is rock mass that needs to be supported at a certain level of excavation in a certain area, the surrounding rock at that level in this area will be fully supported.

[0078] Calculation process In conventional triaxial tests, the crack closure stress under different confining pressures is determined by analyzing the stress-strain curve of the rock specimen. , crack initiation stress , crack damage stress and peak stress , further, at a confining pressure of When the , , .

[0079] Introducing the deviatoric stress peak intensity ratio To analyze the test data: ; in, is the deviatoric stress, is the peak intensity, i.e. Deviatoric stress .

[0080] like Fig. 9 , 10As shown in the figure, the four different threshold stresses increase linearly with the increase of confining pressure, indicating that confining pressure has a great influence on the threshold stress. The crack closure stress is (0.15-0.23) , crack initiation stress is (0.3-0.7) , crack damage stress is (0.7-0.85) In this embodiment, the ratios of the crack closure stress, crack initiation stress, crack damage stress and peak strength are expressed as Rcc d, Rci d and Rcd d respectively. Table 6 below summarizes the ratios of the three threshold stresses and peak strength of granite. For granite, under uniaxial compression, Rcc d, Rci d and Rcd d are approximately 0.22 , 0.41 and 0.78 , and gradually decreases with the increase of confining pressure, indicating that there is a functional relationship between confining pressure and the values ​​of Rcc d, Rci d and Rcd d.

[0081] Table 6 Summary of Rcc d, Rci d, and Rcd d of granite

[0082] Relationship between Rcc d, Rci d and Rcd d and confining pressure. With the increase of confining pressure, Rcc d, Rci d and Rcd d gradually decrease. According to the fitting curve, Rcc d, Rci d and Rcd d finally approach 0.1978, 0.3778 and 0.7066 respectively. Under low confining pressure, it gradually decreases with the increase of confining pressure, but tends to a constant value with the increase of confining pressure, indicating that the expansion of cracks is limited by the confining pressure, but this limiting capacity will gradually stabilize with the increase of confining pressure.

[0083] according to The value of is used to determine the evolution stage of the crack and then calculate the crack closure degree. , under a certain confining pressure, different The axial and radial crack strains at The specific calculation process is as follows: like Figure 6 As shown in the figure, based on the experimental data under different confining pressures, the crack closure degree is plotted. and Through this curve, we can clearly see the changing law of crack closure under different confining pressures and the evolution of cracks at different stress stages.

[0084] The crack strain is exponentially related to the confining pressure. Gradually reduced to 0.0462×10-3 ,but It increases with the increase of confining pressure. This shows that confining pressure can affect the axial crack strain of rock, but the influence gradually weakens with the increase of confining pressure. In the crack closure stage of rock, the crack gradually closes with the increase of axial stress and is completely closed at Rcc d. In order to facilitate the evaluation of the crack closure degree, the axial and radial crack closure degrees are introduced. and : ; in, yes The increment of the peak , post-peak stage .

[0085] when hour, , corresponding to the natural unclosed state of the rock. Department, , corresponding to the complete closure of the rock. In the crack closure stage, under different confining pressures and and An exponential relationship such as Figure 6 As shown in The pseudo-viscous unit can be used to describe the different The crack strain under Figure 7 As shown, this unit can be used to describe The exponential relationship between the crack strain and the crack strain. The mechanical mechanism of this unit is and Gradually tends to 0, and the crack closure degree increases with R d Increases towards 1, according to the formula , Figure 7 The expression of the unit can be written as: ; in, and is the pseudo viscosity coefficient of the crack in the closing stage, Figure 6 From the fitting formula, we can see that the pseudo-viscosity coefficients are 0.08433 and 0.05029 respectively. In actual engineering, the corresponding The value is used to determine the type of relaxation zone in which the surrounding rock is located. For example, at a certain excavation stage, the stress state of the surrounding rock is obtained by monitoring and the is 0.8, according to Figure 8 It can be seen that the surrounding rock is in the weak relaxation zone at this time.

[0086] Extension law of damage rupture zone Numerical simulation analysis: Through numerical simulation software such as FLAC3D, the surrounding rock damage and rupture zones under different anchor arrangement schemes are simulated and analyzed. During the simulation process, the stress and strain distribution of the surrounding rock is calculated according to the constitutive model and failure criterion of the rock to determine whether the surrounding rock is damaged.

[0087] Destruction criteria The low tensile elastic-plastic model is used to analyze the failure behavior of the surrounding rock, and the cracking conditions of the rock material are described by macroscopic strength: ; in, Characterize the three principal stresses of the stress tensor, For tensile strength.

[0088] Whether the rock mass enters the plastic state is determined by the Druker-Prager criterion: ; in, and are the first invariant of the stress tensor and the second invariant of the stress deviator, respectively. is a constant related to rock mass material, is the tensile strength (yield limit).

[0089] A three-dimensional numerical model is established, and parameters such as rock mass parameters, initial geostress field data, and anchor arrangement scheme are input.

[0090] Carry out excavation simulation calculations to obtain the distribution of stress, strain and displacement of surrounding rock at different excavation stages.

[0091] According to the failure criteria, determine whether the surrounding rock has been damaged and determine the scope and shape of the damaged area.

[0092] Calculation results The distribution characteristics of the surrounding rock damage and fracture zones under different anchor arrangement schemes are obtained, such as the location, size and shape of the damage zone, the range of the strong relaxation zone and the weak relaxation zone, etc. For example, in a certain excavation stage, the damage zone of scheme A is mainly concentrated in the top arch part, and the damage depth is deep; the damage zone of scheme B is relatively small and the distribution is relatively concentrated; the damage zone of scheme C is larger, and obvious shear failure occurs in some parts.

[0093] The control effect of different anchor arrangement schemes on the expansion of surrounding rock damage and rupture zone is analyzed to provide a basis for optimizing the anchor arrangement scheme.

[0094] S24. Internal force of anchor rods under support structure: The internal force distribution of anchor rods is also different under different schemes; In scheme A, the internal force of the anchor rod may have a large stress concentration in some parts; The internal force distribution of the anchor in Scheme B is relatively reasonable, and can better play the supporting role; In Scheme C, the internal force of the anchor rod may exceed its design bearing capacity in some parts, resulting in reduced safety of the support structure. The specific steps are as follows: In the numerical model, the internal force of the anchor is calculated by analyzing the force of the anchor unit. The internal force of the anchor includes axial force and shear force, and its calculation method is based on the interaction principle between the anchor and the surrounding rock.

[0095] formula For prestressed anchor rods, the internal force calculation formula is: ; in, is the internal force of the anchor, is the prestress value, is the elastic modulus of the anchor, is the cross-sectional area of ​​the anchor rod, is the strain of the anchor rod.

[0096] The strain of the anchor can be calculated by numerical model or determined based on experimental test data.

[0097] Calculation process In the numerical model, the anchor element is set and coupled with the surrounding rock element.

[0098] Carry out excavation simulation calculation to obtain the strain distribution of the anchor rod.

[0099] Calculate the internal force of the anchor rod according to the internal force calculation formula of the anchor rod.

[0100] Calculation results The internal force distribution of anchor rods under different anchor rod arrangement schemes is obtained, such as the maximum internal force of anchor rods, the internal force distribution law, etc. Furthermore, in a certain excavation stage, the internal force of some anchor rods in scheme A may exceed their design bearing capacity, while the internal force distribution of anchor rods in scheme B is relatively reasonable and can meet the support requirements.

[0101] Comprehensive comparison and optimization suggestions Comprehensive evaluation: Taking into account factors such as deformation, stress, distribution of damage and rupture zones and stress on the support structure, Scheme B performs better in controlling surrounding rock deformation, stress concentration and damage and rupture, and is the relatively optimal anchor arrangement scheme.

[0102] Optimization direction: Further optimize the anchor arrangement: Based on Scheme B, the spacing and arrangement of anchors can be further optimized to make them more consistent with the mechanical properties and deformation laws of the surrounding rock.

[0103] Strengthen the design of support structure: According to the actual situation of surrounding rock, reasonably adjust the parameters of support structure, such as increasing support strength, adopting new support materials, etc., to improve the overall performance of support structure.

[0104] Focus on construction process control: During the construction process, strictly follow the design requirements, strengthen the monitoring and control of the surrounding rock, and adjust the support measures in time to ensure the safety and stability of the project.

[0105] S25. Judging from the deformation and stress results: Scheme B performs better in controlling the deformation and stress of the surrounding rock, so its effect on improving the stability of the surrounding rock is relatively obvious. Scheme A has a decent effect in controlling deformation and stress in some areas, but is not as good as Scheme B overall; Scheme C has certain characteristics in some aspects, but its overall stability control effect is not as good as Scheme B.

[0106] Comprehensive evaluation to determine the optimal solution: Taking into account deformation, stress and stability factors, it is preliminarily determined that Solution B is the relatively optimal anchor arrangement solution.

[0107] S3. Error value analysis: According to the optimal solution, the numerical simulation calculation results are compared with the on-site monitoring data to obtain the comparison results, and the error rate of each evaluation index is calculated based on the comparison results. The specific steps are as follows: S31, deformation comparison Error analysis: Based on the comparison results of numerical simulation and field monitoring data, the error values ​​of various evaluation indicators (such as deformation, stress, etc.) are calculated, and the causes of the errors are analyzed, such as model simplification, inaccurate parameter values, etc.

[0108] The deformation error calculation formula is: ; This formula is used to calculate the absolute difference between the deformation value obtained by simulation and the deformation value actually monitored on site. The larger the difference, the greater the deviation between the simulation and the actual monitoring; The deformation error rate calculation formula is: ; This formula obtains the relative value of the deformation error by dividing the deformation error by the on-site monitoring value and multiplying it by 100%, so as to more intuitively reflect the degree of deviation between the simulation results and the actual monitoring results; Comparison of arch sinking: Taking the arch of unit 1 in the main powerhouse as an example, the arch sinking of Scheme B after the first level of excavation calculated by numerical simulation is 16mm, while the on-site monitoring data shows that the arch sinking of this part is 15.5mm. , the error rate is .

[0109] As the excavation progresses, for example, after the fifth level of excavation, the simulated settlement is 23 mm, while the on-site monitoring is 22 mm, with an error of , the error rate is .

[0110] Comparison of side wall displacement: For the upstream side wall of the main powerhouse, the numerical simulation scheme B shows that the side wall is displaced 13 mm into the hole after the first level of excavation, while the on-site monitoring value is 12.5 mm, with an error of , the error rate is .

[0111] After the fifth level of excavation, the simulation value is 28mm, and the on-site monitoring value is 27mm, with an error of , the error rate is .

[0112] S32, stress comparison: compare the surrounding rock stress distribution under the action of anchor bolts calculated by numerical simulation with the stress distribution monitored on site to verify the accuracy of stress calculation; The stress error calculation formula is: ; This formula is used to calculate the absolute difference between the simulated stress value and the field monitored stress value to evaluate the accuracy of the stress calculation; The stress error rate calculation formula is: ; This formula divides the deformation error by the field monitoring value and multiplies it by 100% to obtain the relative value of the stress error, which helps evaluate the accuracy of the stress calculation. Select key locations to monitor stress: Arrange monitoring points at key locations such as the arch ends of the main powerhouse, and compare the stress values ​​calculated by numerical simulation with the stress values ​​monitored on site.

[0113] Comparative analysis of results: For example, at a certain monitoring point, the numerical simulation results The stress value is 42MPa, the on-site monitoring value is 40MPa, and the error is , the error rate is ; The stress simulation value is 12MPa, the on-site monitoring value is 11MPa, and the error is , the error rate is The overall stress comparison results show that the stress distribution trend calculated by numerical simulation is basically consistent with the on-site monitoring, and the error is within an acceptable range.

[0114] Comparison of damage zones: Compare the distribution of surrounding rock damage zones under the action of anchor bolts calculated by numerical simulation with the damage zones monitored on site to evaluate the accuracy of damage zone prediction.

[0115] The error calculation formula is: ; The error rate calculation formula is: ; Comparison between simulated damage zone range and monitoring: The range of surrounding rock plastic damage zone obtained through numerical simulation is compared with the damage zone monitored on site (such as monitoring through geological radar and other means).

[0116] Result verification: If the simulation results show that there is a certain depth of plastic failure zone in a certain area, and the on-site monitoring also finds signs of rock failure in the corresponding area, and the depth and range of the failure zone are roughly consistent, the accuracy of the prediction of the failure zone is verified. For example, the simulation shows that the depth of the plastic failure zone in a certain part is 2m, and the on-site monitoring shows that the integrity of the rock mass in this part is poor. The geological radar detection estimates that the failure depth is between 1.8 and 2.2m, which is basically consistent.

[0117] S4. Establish a comparison model: establish an error correction model for the evaluation method based on the comparison results, and adjust the parameters in the numerical model based on the deviation between the numerical simulation calculation results and the field monitoring data.

[0118] S41. Error analysis: Based on the comparison results of numerical simulation and field monitoring data, calculate the error value of each evaluation index (such as deformation, stress, etc.), and analyze the causes of the error, such as model simplification, inaccurate parameter values, etc.

[0119] Based on the error analysis, the parameters in the numerical model are adjusted. Furthermore, if the deformation calculated by simulation is too large overall, the value of the rock mass deformation modulus is too high, and the deformation modulus parameter is appropriately reduced; If the stress calculation error is large, it is necessary to re-evaluate the initial geostress field parameters or the interaction parameters between the anchor and the rock mass.

[0120] S42. Establish an error correction model: By analyzing the data of multiple monitoring points and different excavation stages, an error correction model is established to make the numerical simulation results closer to the actual situation, improve the accuracy and reliability of the evaluation method, and provide a more scientific basis for the design and evaluation of anchor support schemes for subsequent similar projects; The specific steps to establish the deformation error correction model are as follows: Assume that the deformation value of on-site monitoring is The simulated deformation value is , the correction formula is obtained by data fitting: ; in, and For the fitting coefficient, a linear relationship is found through data fitting to correct the deviation between the simulated calculated value and the on-site monitoring value; Calculated based on data from multiple monitoring points and The value of is fitted by the least square method, so that Minimum, among which is the number of monitoring points, a deformation correction model is obtained, the simulation calculation results are substituted into the deformation correction model to obtain the corrected deformation value, and the deviation between the simulation calculation value and the on-site monitoring deformation value is corrected according to the corrected deformation value.

[0121] Calculation process Collect deformation data from multiple monitoring points, including on-site monitoring values And the corresponding simulation value .

[0122] Substitute the data into the formula In, get an and function.

[0123] By taking derivatives or other optimization algorithms, find the function that minimizes the function. and The values ​​are shown in Table 4 below: Table 7

[0124] Substituting the data in Table 7 into the formula We can get:

[0125] right and Calculate the partial derivatives respectively and set them equal to 0 to obtain the system of equations:

[0126] Solving the system of equations yields and Assuming that the solution is , , then the correction formula is .

[0127] Substitute the simulation calculation results into the correction model to obtain the corrected deformation value, making it closer to the actual monitoring value. Furthermore, for a certain monitoring point, the simulation calculation deformation value is , then the corrected deformation value is .

[0128] The specific steps to establish the stress error correction model are as follows: The stress value monitored on site is The simulated stress value is , the correction formula is obtained by data fitting: ; in, and is the fitting coefficient; Collect stress data from multiple monitoring points and calculate them using the least squares fitting method. The stress correction model is obtained by substituting the simulation calculation results into the stress correction model to obtain the corrected stress value, and the deviation between the simulation calculation value and the on-site monitoring stress value is corrected according to the corrected stress value.

[0129] Collect stress data from multiple monitoring points and perform similar least squares fitting calculations to find and The values ​​are shown in Table 8 below: Table 8

[0130] Substituting the data in Table 5 into the formula We can get:

[0131] right and Calculate the partial derivatives respectively and set them equal to 0 to obtain the system of equations:

[0132] Solving the system of equations yields and The value of , , then the correction formula is: .

[0133] Substitute the simulated stress value into the revised model to obtain the revised stress value to improve the accuracy of stress calculation.

[0134] By establishing an error correction model, the relationship between numerical simulation and field monitoring data can be better fitted, the accuracy and reliability of the evaluation method can be improved, and a more scientific basis can be provided for the design and optimization of subsequent anchor support schemes.

[0135] In order to make the technical personnel in the technical field better understand the scheme of the present invention, the above-mentioned embodiments are only the preferred technical schemes of the present invention and should not be regarded as limitations of the present invention. The protection scope of the present invention should be the technical schemes recorded in the claims, including the equivalent replacement schemes of the technical features in the technical schemes recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

[0136] It should also be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein.

Claims

1. A method for evaluating the quality of anchor bolt construction layout in a main powerhouse, characterized in that: The following steps are involved: S1. Model construction: Establish three-dimensional numerical models of different anchor arrangement schemes; S2. Simulation calculation and result evaluation: Perform excavation simulation calculation based on the three-dimensional numerical model of different anchor arrangement schemes to obtain the numerical simulation calculation results of surrounding rock deformation, stress distribution, damage and rupture zone distribution and support structure stress; Evaluate the numerical simulation results of different anchor arrangement schemes, obtain evaluation indicators, and determine the optimal scheme based on the evaluation indicators; S3. Error value analysis: Compare the numerical simulation calculation results with the on-site monitoring data according to the optimal solution to obtain the comparison results, and calculate the error rate of each evaluation index based on the comparison results; S4. Establish a comparison model: establish an error correction model for the evaluation method based on the comparison results, and adjust the parameters in the numerical model based on the deviation between the numerical simulation calculation results and the field monitoring data.

2. The main plant anchor bolt construction layout quality assessment method according to claim 1 is characterized in that: In step S2, the deformation of the surrounding rock under different anchor arrangement schemes, including the top arch settlement and side wall displacement, is compared to evaluate the deformation control effect. Analyze the stress state of the surrounding rock under different anchor arrangement schemes, including the degree of stress concentration and uniformity of stress distribution, and evaluate the improvement of the stress state; Analyze the distribution characteristics of the surrounding rock damage and fracture zones under different bolt arrangement schemes, including the location, size and shape of the damage zone and the range of the strong relaxation zone and the weak relaxation zone, and evaluate the control effect of the expansion of the surrounding rock damage and fracture zones; Analyze the internal force distribution of anchor rods under different anchor rod arrangement schemes, including the maximum internal force of anchor rods and the law of internal force distribution, and evaluate the internal force distribution of anchor rods.

3. The main plant anchor bolt construction layout quality assessment method according to claim 1 is characterized in that: In step S3, the numerical simulation results are compared with the field monitoring data to verify the accuracy and reliability of the evaluation method. The specific comparison contents include: Deformation comparison: Compare the surrounding rock deformation under the action of anchor bolts calculated by numerical simulation with the deformation monitored on site, including deformation at different locations and different excavation levels; Stress comparison: Compare the surrounding rock stress distribution under the action of anchor bolts calculated by numerical simulation with the stress distribution monitored on site to verify the accuracy of stress calculation; Comparison of damage zones: Compare the distribution of surrounding rock damage zones under the action of anchor bolts calculated by numerical simulation with the damage zones monitored on site to evaluate the accuracy of damage zone prediction.

4. The main plant anchor bolt construction layout quality assessment method according to claim 3 is characterized in that: The error rate formula for deformation comparison, stress comparison and damage zone comparison is as follows: The deformation error calculation formula is: ; The deformation error rate calculation formula is: ; The stress error calculation formula is: ; The stress error rate calculation formula is: ; The error calculation formula is: ; The error rate calculation formula is: ; The deformation error rate calculation formula, stress error rate calculation formula and depth error rate calculation formula can be used to quantify the difference between the simulation calculation results and the on-site monitoring data. By calculating the difference, the degree of numerical deviation between the simulation value and the monitoring value can be obtained.

5. The main plant anchor construction layout quality assessment method according to claim 1 is characterized in that: In step S4, the following steps are also included: S41, analyzing the deformation error rate, stress error rate and depth error rate under different anchor arrangement schemes, and adjusting the parameters in the three-dimensional numerical model; Among them, if the deformation calculated by simulation is large as a whole, it means that the value of rock deformation modulus is too high and the deformation modulus parameter should be reduced; If the stress calculation error is large, it means re-evaluating the initial geostress field parameters or the parameters of the interaction between the anchor and the rock mass; S42. Establish an error correction model by analyzing data from multiple monitoring points and different excavation stages.

6. The main plant anchor bolt construction layout quality assessment method according to claim 5 is characterized in that: In step S42, the specific steps of establishing the deformation error correction model are as follows: Assume that the deformation value of on-site monitoring is The simulated deformation value is , the correction formula is obtained by data fitting: ； in, and is the fitting coefficient; Calculated based on data from multiple monitoring points and The value of is fitted by the least square method, so that The deformation correction model is obtained by substituting the simulation calculation results into the deformation correction model to obtain the corrected deformation value, and the deviation between the simulation calculation value and the on-site monitoring deformation value is corrected according to the corrected deformation value.

7. The method for evaluating the quality of anchor bolt construction arrangement in the main powerhouse according to claim 6 is characterized in that: In step S42, the specific steps of establishing the stress error correction model are as follows: The stress value monitored on site is The simulated stress value is , the correction formula is obtained by data fitting: ； in, and is the fitting coefficient; Collect stress data from multiple monitoring points and calculate them using the least squares fitting method. The stress correction model is obtained by substituting the simulation calculation results into the stress correction model to obtain the corrected stress value, and the deviation between the simulation calculation value and the on-site monitoring stress value is corrected according to the corrected stress value.

Images