Reservoir bank dangerous rock stability analysis method based on directional progressive degradation

Abstract

The invention discloses a reservoir bank dangerous rock stability analysis method based on directional progressive degradation, and relates to the technical field of geological disaster prevention and control. The method comprises the following steps: determining physical and mechanical properties and boundary conditions of reservoir bank dangerous rocks, and constructing a geological model of the reservoir bank dangerous rocks; based on the determined physical and mechanical properties, establishing a reservoir bank dangerous rock model by using FLAC3D software, and performing grid division; mechanical parameters are given to rock mass units in the model according to a directional progressive degradation principle; based on the established reservoir bank dangerous rock model and the given mechanical parameters, FLAC3D is used for stability analysis, and stress distribution, strain distribution and displacement are obtained; and verifying the analysis result and outputting a treatment suggestion. According to the method, the basic geological information and the physical and mechanical parameters are collected in a refined mode, the degradation hierarchy division of directional layering is combined, accurate simulation of the dangerous rock degradation process is achieved, and the defect that according to an existing method, homogenization parameter assignment cannot reflect degradation directivity and hierarchy is overcome.

Description

Technical Field

[0001] This invention belongs to the field of geological disaster prevention and control technology, and in particular relates to a method for analyzing the stability of unstable reservoir bank rocks based on directional progressive deterioration. Background Technology

[0002] During the construction and operation of water conservancy projects, the stability of unstable reservoir bank rocks has always been a crucial consideration for project safety. Unstable reservoir bank rocks refer to reservoir bank rock masses that are in a critical state of instability, formed under the influence of factors such as reservoir water level fluctuations, geological tectonic activity, and long-term weathering. Their presence not only weakens the overall stability of the reservoir bank but may also induce rock mass cracking, deformation, and even collapse, leading to problems such as soil erosion and waterway blockage. In severe cases, it can even cause geological disasters, resulting in significant economic losses and casualties.

[0003] Currently, research and management of unstable rockfalls along reservoir banks mainly focus on stability analysis and reinforcement measures. However, these efforts are largely based on assessments of the existing conditions and passive protection, lacking in-depth exploration of the rockfall degradation process and proactive intervention. This limits our understanding of the true state of the unstable rockfalls and makes it difficult to accurately assess their long-term stability.

[0004] With the development of geomechanics and materials science, the academic community has begun to pay attention to the problem of unstable rockfall. However, most related studies are limited to natural degradation processes and have not yet systematically characterized the directionality and control mechanisms of degradation. This deficiency leads to significant uncertainty in the assessment of the stability of unstable rockfalls along reservoir banks.

[0005] To address the aforementioned issues, this invention proposes a method for analyzing the stability of reservoir bank boulders based on directional progressive deterioration. By actively setting and controlling the deterioration evolution process of the boulders, the simulation results are made closer to the actual deterioration mechanism, thereby improving the accuracy and reliability of reservoir bank boulder stability analysis. Summary of the Invention

[0006] The purpose of this invention is to provide a method for analyzing the stability of reservoir bank unstable rocks based on directional progressive deterioration. By collecting basic geological information and physical and mechanical parameters in a refined manner, and combining it with directional and stratified deterioration level division, the method achieves accurate simulation of the unstable rock deterioration process, thus solving the problems of insufficient accuracy and limited understanding in existing reservoir bank unstable rock stability analysis.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0008] This invention relates to a stability analysis method for reservoir bank boulders based on directional progressive deterioration, comprising the following steps:

[0009] Step S1: Determine the physical and mechanical properties and boundary conditions of the unstable rocks on the reservoir bank, and construct a geological model of the unstable rocks on the reservoir bank;

[0010] Step S2: Based on the determined physical and mechanical properties, a model of the unstable rock on the reservoir bank is established using FLAC3D software, and the mesh is generated.

[0011] Step S3: Assign mechanical parameters to the rock mass units in the model according to the principle of directional progressive deterioration. The mechanical parameters change gradually with the layers to simulate the degree of deterioration of different parts of the dangerous rock.

[0012] Step S4: Based on the established reservoir bank boulders model and the assigned mechanical parameters, use FLAC3D to perform stability analysis and obtain stress distribution, strain distribution and displacement.

[0013] As a preferred technical solution, in step S1, basic geological information such as topography, geological structure, lithological distribution, fracture development characteristics (including fracture orientation, dip angle, density, and opening), bedding plane distribution, and thickness of the weathering zone near the water is obtained by combining UAV aerial survey, ground geological mapping, and borehole exploration. At the same time, historical water level change data, meteorological data (rainfall and temperature changes), and historical geological disaster records of the reservoir area are collected to establish a complete geological information database.

[0014] As a preferred technical solution, the specific process of establishing a reservoir bank dangerous rock model using FLAC3D software in step S2, based on the basic geological information of the dangerous rocks on the reservoir bank, is as follows:

[0015] Step S21: Select the necessary parameters for FLAC3D modeling from the physical and mechanical parameters obtained from the field survey and indoor tests, including density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and tensile strength. Clarify the parameter attenuation coefficients for different deterioration levels and create a mapping table for the selected parameters according to the input format requirements of FLAC3D software.

[0016] Step S22: Start FLAC3D software, create a new project and set the calculation accuracy, initial time step value and constitutive model; establish a geodetic coordinate system with a point on the bedrock stability interface at the bottom of the dangerous rocks on the reservoir bank as the origin (0,0,0); the X-axis is along the direction of the reservoir bank, the Y-axis is perpendicular to the reservoir bank and points towards the reservoir area, and the Z-axis is perpendicular to the ground and points upward, to ensure that the coordinate system is consistent with the coordinate system of the previous geological survey and borehole data, and to avoid subsequent data matching deviations;

[0017] Step S23: Import the topographic data of the dangerous rocks on the reservoir bank obtained in the early stage through UAV aerial survey and ground geological mapping into FLAC3D in DXF format to generate the surface outline of the dangerous rocks and the interface line of the bedrock; using the Block module of FLAC3D, based on the imported outline, construct a three-dimensional geometric model through stretching, cutting and merging operations.

[0018] Step S24: Determine the mesh reference size, refine the mesh in the deterioration-sensitive area, execute the Mesh command to generate the initial mesh, and use the mesh quality inspection tool built into FLAC3D to calculate the element distortion rate and aspect ratio to adjust the mesh shape;

[0019] Step S25: Compare the mesh model with the original geological data, check the mesh matching degree of the deterioration layer interface and fracture location, calculate the mesh density difference of different unit groups, and adjust the mesh size;

[0020] Step S26: Based on the mapping table created in step S21, use the Property command in FLAC3D to batch assign the physical and mechanical parameters of different degradation levels to the corresponding unit groups.

[0021] As a preferred technical solution, the specific process for generating the surface outline of the dangerous rock and the interface line of the bedrock in step S23 is as follows:

[0022] Step S231: Standardize the topographic data of the dangerous rocks on the reservoir bank, and adjust and correct the UAV aerial survey elevation data based on the reservoir area leveling points.

[0023] Step S232: Perform three-dimensional processing on the fracture data. Based on the fracture orientation and dip angle mapped from the ground, expand the two-dimensional fracture lines (X, Y) into three-dimensional spatial lines (X, Y, Z) using a spatial coordinate transformation formula. The specific formula is as follows:

[0024] ;

[0025] In the formula, The elevation of the fracture initiation point. The angle of the fracture dip. The angle of fracture orientation. The coordinates of the fracture initiation point;

[0026] Step S233: Set the elevation threshold, construct the surface triangulation network using the Delaunay triangulation algorithm, extract the boundary of the triangulation network as the initial contour line, smooth the initial contour line, and generate the final surface contour line.

[0027] Step S234: Extract the burial depth of the top surface of the bedrock from the borehole data, combine it with the contour lines of the bedrock interface obtained by geophysical inversion, generate a discrete point set of the bedrock interface, use the Kriging interpolation algorithm to interpolate the discrete point set, generate a continuous bedrock interface surface equation, and cut the intersection line of the bedrock interface and the dangerous rock range as the bedrock interface line.

[0028] Step S235: Based on the 3D fracture data, generate attributed feature lines in the DXF file according to the "fracture ID-direction-dip angle-length" attribute. Key fractures with a length > 5m are marked separately as critical boundaries for subsequent cutting. Based on the thickness of the deteriorated layer revealed by the borehole, and combined with the distribution pattern of "thicker near water and thinner far water," a linear gradient model is used to generate the deteriorated layer interface line. The specific formula is as follows:

[0029] ;

[0030] In the formula, The thickness of the deteriorated layer at a distance Y from the water-side is given. The initial thickness on the near-water side. This is the attenuation coefficient.

[0031] As a preferred technical solution, in step S25, the deteriorated layer interface is pressed... Sampling points are set up in the grid to extract the interface elevation between the grid model and the borehole data. For each main control fracture, a check point is taken every 2m along the strike. Multiple sampling points are evenly selected on the terrain contour line by the number of penetration units of the fracture line in the grid. The elevation difference between the grid ground and the DSM is extracted. The interface offset, fracture penetration and terrain conformity are calculated and compared with the threshold to determine whether the area is a geometric anomaly area and start the correction process.

[0032] As a preferred technical solution, in step S3, the deterioration layer division adopts a vertical stratification and horizontal partitioning method; wherein, the vertical stratification extends from the surface of the unstable rock to its depth, and is divided into strongly weathered, moderately weathered, weakly weathered, and slightly weathered layers according to the degree of weathering. The thickness of each layer is determined based on borehole exploration data and weathering zone detection results, and the thickness range is [missing information]. ;

[0033] The transverse partitions, extending from the near-water side to the far-water side, are divided into severely deteriorated, moderately deteriorated, slightly deteriorated, and undeteriorated zones according to their degree of degradation. The partition boundaries are determined based on the thickness of the weathering zone and the density of fissures on the near-water side. The width of each partition is [missing information]. .

[0034] As a preferred technical solution, in step S3, the mechanical parameters are assigned values ​​to rock mass units of different degradation levels and zones according to the principle of directional progressive degradation, which decreases from the near-water side to the far-water side and from the surface to the deep layer. The specific parameter assignments are as follows:

[0035] Complete rock mass mechanical parameters for the undeteriorated zone were obtained using laboratory tests.

[0036] The cohesion and internal friction angle of the mildly deteriorated zone are assigned 80%-90% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 85%-95% of the parameters of the undeteriorated zone.

[0037] The cohesion and internal friction angle of the moderately deteriorated zone are assigned 60%-80% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 70%-85% of the parameters of the undeteriorated zone.

[0038] The cohesion and internal friction angle of the severely deteriorated zone are assigned 40%-60% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 50%-70% of the parameters of the undeteriorated zone.

[0039] Based on the degree of fracture development, the cohesion and internal friction angle of the special deteriorated sublayer are reduced by 10%-30% from the parameters of the severely deteriorated zone, and the influence of the fracture permeability coefficient on the deterioration is also considered. During the assignment process, the parameters of adjacent layers and zones adopt a linear transition method to avoid simulation distortion caused by abrupt parameter changes.

[0040] As a preferred technical solution, the specific process of FLAC3D performing stability analysis in step S4 is as follows:

[0041] Step S41: In the built-in constitutive model of FLAC3D software (select the Mohr-Coulomb constitutive model or the jointed rock mass constitutive model according to the characteristics of the dangerous rock), input the assigned mechanical parameters, and verify the rationality of the model parameters by comparing them with the stress and displacement data monitored in the field.

[0042] Step S42: Use the strength reduction method combined with time step iteration to simulate the directional gradual deterioration process of the unstable rock. Set the iteration time step (determined according to the deterioration rate, ranging from 0.1 to 1 year / time step). For each iteration time step, update the mechanical parameters of each level and zone according to the preset deterioration rate.

[0043] Step S43: Perform stress distribution analysis, extract stress cloud map for each time step, analyze the distribution characteristics of principal stress, shear stress and tensile stress inside the unstable rock, identify stress concentration areas, and determine the potential failure initiation location;

[0044] Step S44: Perform strain and displacement analysis, monitor the strain and displacement changes of key parts of the dangerous rock (surface near water, fracture development zone, near bedding plane), plot displacement-time curves and strain-time curves, analyze deformation rate and deformation trend, and determine the maximum displacement value and displacement concentration area.

[0045] Step S45: Perform failure mode identification. By judging the stress state of the elements during the simulation (when the shear stress of an element exceeds the shear strength or the tensile stress exceeds the tensile strength, it is determined to be element failure), and combined with the crack propagation trajectory (followed and drawn by the FLAC3D discrete element module), identify the failure mode of the unstable rock (such as sliding failure, tensile failure, toppling failure or combined failure).

[0046] Step S46: Calculate the stability coefficient. Use the strength reduction method to calculate the stability coefficient for each time step (stability coefficient = shear strength / shear stress). When the stability coefficient is ≤1.0, the unstable rock is determined to be in an unstable state. Record the critical time of instability and the corresponding degree of deterioration.

[0047] As a preferred technical solution, in step S5, the stability analysis results are verified by combining on-site monitoring data (stress monitoring, displacement monitoring), historical geological disaster cases, and model inversion analysis. If the simulated stress and displacement values ​​deviate from the on-site monitoring values ​​by more than 10%, or the predicted failure mode does not match the actual situation, it is necessary to return to step S1 to adjust the parameters or model settings and re-perform the simulation analysis. Based on the stability analysis results, the stability status (stable, basically stable, understability, unstable), potential failure area, instability risk level, and critical triggering conditions (such as specific water level combinations, heavy rainfall) of the unstable rock are identified. Targeted treatment suggestions are proposed for the deterioration characteristics and stability status of different areas, including: grouting reinforcement schemes for severely deteriorated areas near the water, slope reduction and load reduction schemes for surface weathering zones, anti-slide pile installation schemes for potential sliding surfaces, crack sealing treatment schemes for fracture development areas, and layout suggestions for reservoir bank protection projects (such as breakwaters and revetments).

[0048] As a preferred technical solution, in step S6, a long-term monitoring system for the stability of unstable rocks on the reservoir bank is established, and stress sensors, displacement sensors, water level sensors and crack monitoring instruments are deployed to collect data on the mechanical response and environmental parameters of the unstable rocks in real time. The monitoring data is periodically (every 1-2 years) input into the model constructed in step S4 to update the mechanical parameters and boundary conditions, conduct dynamic stability verification, and adjust the treatment plan according to the verification results to achieve closed-loop management of "monitoring-simulation-treatment".

[0049] The present invention has the following beneficial effects:

[0050] (1) This invention achieves accurate simulation of the deterioration process of dangerous rocks by collecting basic geological information and physical and mechanical parameters in a refined manner and combining them with the directional and stratified deterioration layer division. It overcomes the shortcomings of existing methods that cannot reflect the directionality and hierarchy of deterioration by homogenizing parameter assignment, and makes the stability analysis results closer to the actual working conditions.

[0051] (2) This invention adopts a technical approach that combines “experiment-simulation-monitoring”, establishes a quantitative relationship between the degree of deterioration and mechanical parameters, clarifies the mechanical response characteristics and failure modes of dangerous rocks at different stages, provides precise technical targets for the treatment of dangerous rocks on the reservoir bank, and improves the pertinence and effectiveness of the treatment plan.

[0052] (3) The present invention introduces a dynamic update and long-term monitoring linkage mechanism, realizing the transformation of stability analysis from "static assessment" to "dynamic early warning", which can capture the dynamic changes of the deterioration and evolution of dangerous rocks in a timely manner and provide continuous technical support for long-term safety prevention and control.

[0053] (4) This invention is applicable to the stability analysis of dangerous rocks on the reservoir bank in different lithologies and reservoir environments. It has strong universality and engineering application value and can be widely used in water conservancy projects, hydropower projects and reservoir geological disaster prevention and control.

[0054] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0055] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a flowchart of the method described in an embodiment of the present invention;

[0057] Figure 2 This is a diagram illustrating the stability analysis model of reservoir bank dangerous rocks based on directional progressive deterioration, as implemented in this invention.

[0058] Figure 3-5 Displacement, strain, and stress diagrams were generated for the stability analysis of the mean value model of unstable rocks on the reservoir bank at a water level of 175m in this invention.

[0059] Figure 6-8 This invention provides displacement, strain, and stress diagrams for the stability analysis of unstable reservoir bank rocks with spatial variability at a reservoir water level of 175m.

[0060] Figure 9-11 The present invention provides displacement, strain, and stress diagrams for the stability analysis of unstable reservoir bank rocks based on directional progressive deterioration at a reservoir water level of 175m. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0062] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0063] Before introducing the embodiments of this application, the dangerous rocks on the reservoir bank will be explained first.

[0064] Dangerous rock masses on reservoir banks refer to rock formations that, after a reservoir is filled, may become unstable and collapse due to factors such as periodic rises and falls in water level, wave erosion, and changes in the physical properties of the rock mass. This type of geological hazard is common in high and steep canyon-type reservoirs (such as the Three Gorges Reservoir area).

[0065] Geological conditions: Steep terrain (slope > 45°), hard and brittle rock masses (such as limestone and dolomite), and well-developed tectonic fissures are fundamental. For example, the Jialingjiang Formation limestone in the Three Gorges Reservoir area has formed unstable rock masses under long-term unloading.

[0066] Triggering factors: Fluctuations in reservoir water levels lead to alternating wet and dry conditions in the rock mass, softening of structural surfaces, wave erosion at the slope toe, and accelerated damage caused by earthquakes and rainfall.

[0067] To make the purpose, technical solution, and advantages of this application clearer, the following description is provided in conjunction with the appendix. Figure 1-11 The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the application.

[0068] Please see Figure 1 As shown, this invention is a method for analyzing the stability of unstable reservoir bank rocks based on directional progressive deterioration, comprising the following steps:

[0069] Step S1: Determine the physical and mechanical properties and boundary conditions of the unstable rocks on the reservoir bank, and construct a geological model of the unstable rocks on the reservoir bank;

[0070] Step S2: Based on the determined physical and mechanical properties, a model of the unstable rock on the reservoir bank is established using FLAC3D software, and the mesh is generated.

[0071] Step S3: Assign mechanical parameters to the rock mass units in the model according to the principle of directional progressive deterioration. The mechanical parameters change gradually with the layers to simulate the degree of deterioration of different parts of the dangerous rock.

[0072] Step S4: Based on the established reservoir bank boulders model and the assigned mechanical parameters, use FLAC3D to perform stability analysis and obtain stress distribution, strain distribution and displacement.

[0073] In step S1, basic geological information such as topography, geological structure, lithology distribution, fracture development characteristics (including fracture orientation, dip angle, density, and opening), bedding plane distribution, and thickness of the weathering zone on the near-water side of the dangerous rocks on the reservoir bank is obtained by combining UAV aerial survey, ground geological mapping, and borehole exploration. At the same time, historical water level change data, meteorological data (rainfall and temperature changes), and historical geological disaster records of the reservoir area are collected to establish a complete geological information database.

[0074] The physical and mechanical properties of the unstable reservoir bank rocks were obtained through both field and laboratory tests. Specifically, field tests involved selecting representative rock samples from different areas of the unstable bank rocks (near-water side, far-water side, surface, and deep layers) and conducting point load tests and shear tests to obtain parameters such as in-situ compressive strength and in-situ shear strength. Stress monitoring sensors were also installed to acquire in-situ geostress data. Laboratory tests involved collecting rock samples from different areas and conducting tests including uniaxial compression tests, triaxial compression tests, tensile tests, water absorption tests, and durability tests (simulating wet-dry cycle tests based on water level fluctuations and freeze-thaw cycle tests based on weathering). These tests determined the rock's cohesion, internal friction angle, elastic modulus, Poisson's ratio, compressive strength, tensile strength, density, and water absorption rate. For degradation-sensitive parameters (cohesion and internal friction angle), comparative tests at different degrees of degradation were conducted to establish a quantitative relationship model between the degree of degradation and parameter attenuation.

[0075] Boundary conditions include mechanical boundary conditions, environmental boundary conditions, and load boundary conditions;

[0076] The mechanical boundary conditions include the geostress boundary (based on the in-situ geostress data obtained from the physical and mechanical property tests of the aforementioned unstable rocks on the reservoir bank, the magnitude and distribution of horizontal and vertical geostress are determined) and the constraint boundary (based on the contact relationship between the unstable rocks and the bedrock, the fixed constraint and sliding constraint areas are determined).

[0077] Environmental boundary conditions include reservoir water level boundary (based on historical water level data, setting normal storage water level, dead water level, flood season water level and water level rise and fall rate), rainfall boundary (based on meteorological data, setting rainfall intensity, rainfall duration and rainfall infiltration coefficient), and temperature boundary (setting seasonal temperature variation range and diurnal temperature difference).

[0078] The load boundary conditions take into account the self-weight of the unstable rock, the seismic load (determined according to the seismic intensity level of the reservoir area), and possible additional loads (such as the weight of vegetation cover and the load of local deposits).

[0079] Various boundary conditions are transformed into quantitative parameters that can be identified by numerical simulation. For example, reservoir water level changes are input in the form of time-water level curves, rainfall infiltration is achieved by setting the spatial distribution of rock mass permeability coefficient, and geostress is applied to the model boundary in the form of uniformly distributed load.

[0080] In step S2, the specific process for establishing a model of the dangerous rocks on the reservoir bank using FLAC3D software based on the basic geological information of the dangerous rocks is as follows:

[0081] Step S21: Based on the physical and mechanical parameters obtained from on-site surveys and indoor tests, select the necessary parameters for FLAC3D modeling, including density. Elastic modulus Poisson's ratio Cohesion internal friction angle ,tensile strength Determine the parameter attenuation coefficients for different degradation levels (e.g., inlet / outlet, surface / deep). (such as severely deteriorated areas) Undeteriorated area ), and create a mapping table for the filtered parameters according to the input format requirements of FLAC3D software;

[0082] Specifically, a mapping table of "unit group - parameter name - parameter value" is used to link "surface unit of severely deteriorated zone near water" with " , , , , "The association lays the foundation for subsequent parameter assignment."

[0083] Step S22: Launch FLAC3D software, create a new project and set the initial values ​​for calculation accuracy and time step ( The constitutive model (the Mohr-Coulomb constitutive model is selected based on the characteristics of the unstable rock, which can accurately describe the shear failure characteristics of the rock and is consistent with the instability mechanism of the unstable rock on the reservoir bank); a geodetic coordinate system is established with a certain point on the bedrock stability interface at the bottom of the unstable rock on the reservoir bank as the origin (0,0,0); the X-axis is along the direction of the reservoir bank, the Y-axis is perpendicular to the reservoir bank and points to the reservoir area, and the Z-axis is perpendicular to the ground and points upward, to ensure that the coordinate system is consistent with the coordinate system of the previous geological mapping and borehole data, and to avoid subsequent data matching deviations;

[0084] Step S23: Import the topographic data of the dangerous rocks on the reservoir bank (such as contour lines, slope, and fissure distribution vector maps) obtained in the early stage through UAV aerial survey and ground geological mapping into FLAC3D in DXF format to generate the surface outline of the dangerous rocks and the interface line of the bedrock; using the Block module of FLAC3D, based on the imported outline, construct a three-dimensional geometric model through stretching, cutting, and merging operations.

[0085] Specifically, during the stretching process, the surface outline is stretched along the X-axis (the direction of the reservoir bank), and the length is determined according to the actual study area (e.g., 50-100m) to form the initial entity of the dangerous rock.

[0086] During cutting, based on the distribution of deterioration layers revealed by the borehole (e.g., a strong weathered layer with a thickness of 2m and a moderate weathered layer with a thickness of 3m), horizontal cutting surfaces (Z=2m, Z=5m) are created using the "Plane" command to divide the entity into surface, middle, and deep unit groups; at the same time, along the Y-axis (near-water to far-water direction), vertical cutting surfaces (Y=4m, Y=9m, Y=15m) are used to divide the severely deteriorated area, moderately deteriorated area, lightly deteriorated area, and undeteriorated area, achieving a geometric division of "vertical layering + horizontal partitioning";

[0087] During merging, a topology check is performed on adjacent unit groups after the cut, and overlapping surfaces and redundant nodes are deleted to ensure the continuity and integrity of the geometric model.

[0088] Step S24: Determine the grid reference dimensions (e.g., crack width) The baseline mesh size is determined according to the principle that "mesh size ≤ 1 / 5 of the minimum feature size". (e.g., when the crack width is 0.5m,) For areas sensitive to degradation (such as severely degraded areas near the water or areas with developed fractures), the mesh should be finer, and a fineness coefficient should be set. Encrypted size An amplification factor is set for the deep, undeteriorated zone (with stable mechanical properties). Enlarged size Balancing computational accuracy and efficiency; encryption coefficients Dynamically adjusted according to the degree of degradation (severe degradation area) Moderately deteriorated area By dynamically adjusting the density coefficient, the computational accuracy is improved in the deterioration-sensitive area, and the mesh density is reduced in the stable area, thus achieving a balance between accuracy and efficiency.

[0089] The initial mesh is generated by executing the Mesh command. The mesh shape is adjusted by calculating the element distortion rate and aspect ratio using FLAC3D's built-in mesh quality inspection tool. Specifically, elements with a distortion rate > 0.8 (out of 1.0) and an aspect ratio > 5 are optimized by using "node smoothing" and "element splitting" operations to adjust the mesh shape, ensuring that the quality of all elements meets the calculation requirements (distortion rate ≥ 0.6, aspect ratio ≤ 3).

[0090] FLAC3D uses the tetrahedral element distortion rate D to evaluate mesh quality, reflecting the degree of deviation between the elements and the ideal regular tetrahedron. The specific formula is as follows:

[0091] ;

[0092] In the formula, The lengths of the three edges of the tetrahedron. For distortion rate, The volume is that of a tetrahedral element. This formula quantifies the rationality of the mesh shape through the distortion rate, avoiding difficulties in computational convergence or distortion of results due to excessive element distortion.

[0093] To ensure that the grid accurately captures the microscopic features of dangerous rocks (such as fractures and deteriorated interfaces), the baseline grid size is... Minimum characteristic size required for dangerous rock The matching formula is as follows:

[0094] ;

[0095] In the formula, As the baseline grid size, The minimum feature size of the unstable rock is preferably the crack width or the thickness of the deteriorated layer interface. This formula, by limiting the proportional relationship between the mesh size and the microscopic features, avoids smoothing out key information such as gaps and cracked layers due to excessively large mesh sizes, ensuring that the model can reflect the true structure of the unstable rock.

[0096] Step S25: Compare the mesh model with the original geological data, check the mesh matching degree of the deterioration layer interface and fracture location, calculate the mesh density difference of different unit groups, and adjust the mesh size;

[0097] Specifically, the quality of the mesh is verified for geometric consistency: the mesh model is compared with the original geological data (such as borehole columnar sections and topographic profiles) to check the mesh matching degree of the deterioration layer interface and fracture location. If the interface offset is >0.1m, the mesh is corrected by adjusting the coordinates of the cutting plane. The mesh is also verified for mechanical compatibility: the mesh density difference between different unit groups is calculated to ensure that the mesh size transition coefficient between adjacent unit groups (such as severely deteriorated areas and moderately deteriorated areas) is ≤2, to avoid stress concentration simulation distortion caused by abrupt size changes; if the transition coefficient is >2, a transition layer unit group is inserted, and the mesh size is gradually adjusted.

[0098] Step S26: Based on the mapping table created in step S21, use the Property command of FLAC3D to batch assign the physical and mechanical parameters of different degradation levels to the corresponding unit groups.

[0099] Specifically, firstly, density values ​​are assigned to the unit groups, and a uniform value is assigned to all unit groups. (Determined by lithology, such as sandstone) );

[0100] Mechanical parameter assignment: Based on the principle of directional progressive degradation, values ​​are assigned to the unit groups in the severely degraded region. Assigning values ​​to moderately degraded areas Assigning values ​​to areas with mild degradation Assigning values ​​to undegraded areas This enables targeted, hierarchical assignment of parameters.

[0101] Based on the principle of directional progressive degradation (parameters increasing from near-water to far-water and from surface to depth), a linear interpolation formula is used to achieve parameter transitions in different degradation zones, thereby enhancing cohesion. For example, the formula is as follows:

[0102] ;

[0103] In the formula, Indicates the first Layer (vertical) Cohesion (Pa) of the transverse unit. This represents the maximum cohesion (Pa) in the undeteriorated region. The minimum cohesion (Pa) in the severely deteriorated zone. The horizontal distance between the severely degraded area near the water and the undegraded area far from the water. For the first Layer (vertical) The horizontal distance from the boundary of the (lateral) zone unit to the severely deteriorated zone; the smooth transition of parameters is achieved through linear interpolation, avoiding stress concentration simulation errors caused by parameter abrupt changes, and better reflecting the actual deterioration process of dangerous rocks.

[0104] FLAC3D uses the Mohr-Coulomb constitutive model to describe the mechanical response of unstable rocks, and its failure criterion formula is as follows:

[0105] ;

[0106] In the formula, For the element shear strength, For element normal stress, For cohesion, It is the internal friction angle.

[0107] In practice, step 1: parameter preprocessing, filtering core parameters and organizing them into a mapping table, such as " , (Surface layer of severely deteriorated area) Corresponding parameters: .

[0108] Step 2: Establish coordinate system, with the center point of the bedrock interface ( With the origin at ( ), the X-axis runs along the reservoir bank ( ). The Y-axis points to the warehouse area ( Z-axis upward ( ).

[0109] Step 3: Geometric modeling, importing DXF format terrain outlines, extending 60m along the X-axis to form an initial solid; cutting the solid with horizontal planes of Z=2m and Z=5m to divide it into 3 vertical layers; using... The solid is cut with a vertical plane, divided into 3 horizontal regions, and finally formed 3×3=9 unit groups.

[0110] Step 4: Mesh generation, datum size calculation, and... ,have to ;

[0111] Encryption settings: Severely degraded area , Moderately deteriorated area Slightly deteriorated area ;

[0112] Mesh generation: Executing the Mesh command generates approximately 120,000 cells in total; based on distortion rate calculations, 98% of the cells... The percentage of qualified units meets the requirements.

[0113] Step 5: Parameter assignment: Calculate the cohesion of each unit group based on the linear interpolation formula.

[0114] Moderately deteriorated area ( ): , , ,have to Place , Place ;

[0115] Mildly deteriorated area : ,have to Place The parameters of the vertical layers are assigned values ​​according to the same logic to complete the parameter mapping of all unit groups.

[0116] The constructed FLAC3D model can clearly reflect the differences in geometric boundaries and mechanical parameters of the nine deteriorated unit groups, and the mesh distortion rate meets the calculation requirements; subsequent stability simulations show that the severely deteriorated zone near the water ( Significant stress concentration (maximum shear stress) occurs. The model perfectly matched the deformation area of ​​the dangerous rock detected on-site, verifying the effectiveness of the model construction process and algorithm.

[0117] In step S23, the specific process for generating the surface outline of the dangerous rock and the interface line of the bedrock is as follows:

[0118] Step S231: Standardize the topographic data of the dangerous rocks on the reservoir bank, and adjust and correct the UAV aerial survey elevation data based on the reservoir area leveling points.

[0119] The specific standardization process mainly involves processing data sources including 1:500 high-precision DSM (Digital Surface Model) generated by UAV aerial surveys, fracture attitude data (strike and dip / density) obtained from ground geological mapping, borehole exploration data (core photos, thickness of deteriorated layers), and bedrock interface depth data inverted from geophysical exploration (seismic wave CT).

[0120] The format conversion process involves converting DSM data to FLAC3D-compatible ASCII format elevation point cloud (including X, Y, and Z coordinates); converting fracture distribution vector map (CAD format) to DXF format, retaining attributes such as fracture endpoint coordinates, strike angle, and length; and organizing borehole data into a "hole number-depth-lithology-deterioration level" data table, where the deterioration level is coded as "non-deteriorated / slightly deteriorated / moderately deteriorated / severely deteriorated" (0-3).

[0121] Step S232: Perform three-dimensional processing on the fracture data. Based on the fracture orientation and dip angle mapped from the ground, expand the two-dimensional fracture lines (X, Y) into three-dimensional spatial lines (X, Y, Z) using a spatial coordinate transformation formula. The specific formula is as follows:

[0122] ;

[0123] In the formula, The elevation of the fracture initiation point. The angle of the fracture dip. The angle of fracture orientation. The coordinates of the fracture initiation point are used; the ICP (Iterative Closest Point) algorithm is used to register the borehole data and the aerial survey data to correct the deviation between the depth of the deteriorated layer revealed by the borehole and the topographic data from the aerial survey. To ensure the consistency of geological data;

[0124] Step S233: Set the elevation threshold, construct the surface triangulation network using the Delaunay triangulation algorithm, extract the boundary of the triangulation network as the initial contour line, smooth the initial contour line, and generate the final surface contour line.

[0125] Specifically, the elevation point cloud data was processed using Python scripts, and the surface contour of the dangerous rock was extracted through the following steps: setting an elevation threshold (areas above the reservoir water level of 145m and with a slope greater than 30° were identified as dangerous rock areas); constructing a surface triangulation network using the Delaunay triangulation algorithm, and extracting the boundary of the triangulation network as the initial contour line; smoothing the initial contour line (removing burrs and retaining corners with a curvature radius greater than 0.5m) to generate the final surface contour line (DXF format).

[0126] Step S234: Extract the bedrock top surface burial depth from the borehole data (e.g., in borehole 1: the bedrock burial depth is 5m at X=100m, Y=50m). Combine this with the bedrock interface contour lines obtained from geophysical inversion to generate a discrete point set for the bedrock interface. Use the Kriging interpolation algorithm to interpolate the discrete point set to generate a continuous bedrock interface surface equation. The equation is: In the formula, This represents the elevation of the bedrock interface. All are interpolation coefficients (determined by least squares fitting); the intersection line between the bedrock interface and the dangerous rock range is taken as the bedrock interface line;

[0127] Step S235: Based on the 3D fracture data, generate attributed feature lines in the DXF file according to the "fracture ID-direction-dip angle-length" attribute. Key fractures with a length > 5m are marked separately as critical boundaries for subsequent cutting. Based on the thickness of the deteriorated layer revealed by the borehole, and combined with the distribution pattern of "thicker near water and thinner far water," a linear gradient model is used to generate the deteriorated layer interface line. The specific formula is as follows:

[0128] ;

[0129] In the formula, The thickness of the deteriorated layer at a distance Y from the water-side is given. The initial thickness on the near-water side. This is the attenuation coefficient.

[0130] In practice, the surface contour line is imported by executing the command "import dxf "surface_contour.dxf" in FLAC3D. The contour line is then mapped to the geodetic coordinate system defined in step S22 (X: reservoir bank direction, Y: near-water to far-water direction, Z: elevation) using the translate and rotate commands, ensuring that the origin of the contour line coincides with the borehole reference point (deviation ≤ 0.05m). Similarly, the bedrock interface line, fracture feature line, and deteriorated layer interface line are imported to form a two-dimensional basic model with "multi-layer feature line superposition".

[0131] The stretching operation is performed based on constraints. The surface outline is used as the cross section, and the initial three-dimensional solid is generated by stretching along the X-axis (the direction of the reservoir bank). The stretching length is determined by the actual distribution range of the unstable rock. During stretching, the "fracture feature line constraint" is enabled. When the stretching path intersects with the main control fracture line, an internal node is automatically generated at the intersection point to ensure that the fracture is completely preserved in the three-dimensional solid (solving the problem of fracture being truncated in traditional stretching).

[0132] When stretching, "crack feature line constraint" is enabled. When the stretching path intersects with the main crack line, an internal node is automatically generated at the intersection point to ensure that the crack is completely preserved in the three-dimensional solid (solving the problem of crack being truncated in traditional stretching).

[0133] When performing longitudinal layer cutting (z direction), based on the interface line of the deteriorated layer, a horizontal cutting surface is generated in FLAC3D (e.g., the top surface of the strongly weathered layer Z=150m, the bottom surface Z=145m), and the cutting command is executed; after cutting, longitudinal unit groups such as strongly weathered layer (Z=150-145m) and moderately weathered layer (Z=145-140m) are formed, and each unit group automatically inherits the attribute tags of the corresponding deteriorated layer;

[0134] When performing transverse partitioning (Y direction), partitions are created based on the degree of degradation from the near-water side to the far-water side, generating vertical cutting surfaces (e.g., the boundary between severely degraded and moderately degraded areas, Y=20m). Intelligent cutting is then performed in conjunction with fracture characteristic lines. When the cutting surface intersects with a fracture line, the shape of the cutting surface is automatically adjusted to conform to the fracture direction. For overlapping surfaces of adjacent unit groups after cutting (e.g., the upper and lower interfaces of longitudinally layered structures), the `block merge faces tolerance 0.01` command is executed to delete redundant surfaces, with the tolerance parameter controlling the merging accuracy (0.01m). The "least squares node smoothing algorithm" is used to optimize the coordinates of entity nodes, ensuring that the node deviation between adjacent units is ≤0.02m, avoiding calculation errors caused by node misalignment. The algorithm formula is as follows:

[0135] ;

[0136] In the formula, To optimize the node coordinates, The coordinates of adjacent nodes The weights are determined by the distance (the closer the distance, the greater the weight).

[0137] In step S25, press on the interface of the deteriorated layer. Sampling points are set up in the grid to extract the interface elevation between the grid model and the borehole data. For each main control fracture, a check point is taken every 2m along the strike. Multiple sampling points are evenly selected on the terrain contour line by the number of penetration units of the fracture line in the grid. The elevation difference between the grid ground and the DSM is extracted. The interface offset, fracture penetration and terrain conformity are calculated and compared with the threshold to determine whether the area is a geometric anomaly area and start the correction process.

[0138] Specifically, for three key geological features—deterioration layer interface, fracture location, and topographic contour—quantitative verification indicators are designed, including interface offset. The vertical deviation in meters (m) between the interface of the deteriorated layer (e.g., the bottom surface of a strongly weathered layer) in the mesh model and the actual interface revealed by the borehole; fracture penetration. This represents the ratio of the number of elements actually penetrated by the crack line in the mesh to the theoretically required number of elements to be penetrated. Indicates complete penetration; terrain fit. The specific formula for calculating the overlap between the grid surface outline and the UAV aerial survey DSM data is as follows:

[0139] ;

[0140] In the formula, The number of sampling points. For grid surface elevation, For aerial elevation surveying, , These are the maximum and minimum elevations of the dangerous rock. The closer the result is to 1, the higher the degree of agreement.

[0141] The threshold is determined as follows, and the qualified standard is: , , If any indicator is not met, it is marked as a geometric anomaly area and a correction process is initiated.

[0142] When performing degraded interface offset correction, that is, for For the area in question, the correction process is as follows:

[0143] 1. Extract the offset of all sampling points within the abnormal region. Offset surfaces are generated by kriging interpolation. ;

[0144] 2. Calculate the cutting surface correction amount (Reverse compensation);

[0145] 3. Adjust the equation parameters of the corresponding cutting surface in FLAC3D (such as the original equation). Revised to );

[0146] 4. Re-execute the block cut plane equation command. And locally update the mesh.

[0147] When correcting for insufficient crack penetration, that is, targeting The correction process for the fractured section is as follows:

[0148] 1. Identify elements whose cracks are not penetrated and mark them as "target elements";

[0149] 2. Insert virtual constraint lines (based on fracture orientation parameters) along the fracture direction within the target element.

[0150] 3. Execute the command "block split cell target-elements along fracture-line" to split the target elements along the constraint line;

[0151] 4. Regenerate the local mesh, ensuring that the crack line runs through the edge of the new cell (not inside).

[0152] When performing terrain fit correction, i.e. For the area in question, the correction process is as follows:

[0153] 1. For surface nodes in areas with low congruence, calculate elevation corrections based on DSM data. ;

[0154] 2. Adjust node elevations using the "least squares smoothing method": In the formula: Smoothing coefficient To avoid excessive single corrections that could lead to element distortion;

[0155] 3. For the adjusted nodes, check the distortion rate of adjacent elements. If... Then iterative correction (up to 3 times).

[0156] Construct a verification index system and design a multi-scale mechanical compatibility index: scale transition coefficient. Stress gradient matching degree and energy transfer efficiency ; Scale transition coefficient The ratio of the largest grid size of adjacent cells Stress gradient matching degree The synergy between the mesh size gradient and the stress gradient is represented by the following formula: In the formula, For the grid size gradient, For average size, For shear stress gradient, This represents the average shear stress.

[0157] In step S3, the deterioration layers are divided using a combination of vertical stratification and horizontal zoning. Vertical stratification extends from the surface of the unstable rock to its deeper layers, and is further divided according to weathering degree into strongly weathered, moderately weathered, weakly weathered, and slightly weathered layers. The thickness of each layer is determined based on borehole exploration data and weathering zone detection results, and the thickness range is [not specified in the original text]. The horizontal zoning extends from the near-water side to the far-water side, dividing the area into severely deteriorated, moderately deteriorated, slightly deteriorated, and undeteriorated zones according to the degree of degradation. The zoning boundaries are determined based on the thickness of the weathering zone and the density of fissures on the near-water side. The width of each zone is [missing information]. For areas with dense crack development, a separate sub-layer for specific degradation is defined to ensure the accuracy of degradation simulation.

[0158] The vertical layers are: surface strongly weathered layer (thickness 2m), medium weathered layer (thickness 3m), deep weakly weathered layer (thickness 5m), and slightly weathered layer (thickness ≥10m).

[0159] Lateral zoning: Severely deteriorated zone (4m wide) on the near-water side, moderately deteriorated zone (5m wide), slightly deteriorated zone (6m wide), and undeteriorated zone on the far-water side.

[0160] Specifically, the core parameters for vertical stratification are acquired through borehole exploration and field testing to obtain vertical (surface to deep) degradation characteristic parameters, including:

[0161] Weathering indicators: including rock mass integrity coefficient ( Sound wave velocity ratio), rebound value ( Rebound hammer test), porosity ( (Indoor test);

[0162] Depth parameters: Depth of the top and bottom plates of each weathering zone revealed by the borehole ( , ), unit m;

[0163] Physical and mechanical parameters: cohesion (c) and internal friction angle at different depths ( Attenuation rate (ratio to intact rock mass).

[0164] Construct a multi-parameter coupled weathering index to quantify the weathering grade of rock mass:

[0165] ;

[0166] In the formula, Rock mass integrity coefficient (intact rock mass) ); This is the ratio of the rebound value to the rebound value of the intact rock mass. Porosity (of intact rock mass) ); It is the ratio of cohesion to the cohesion of the intact rock mass; The range of values ​​is The larger the value, the more severe the weathering.

[0167] according to The values ​​are divided vertically into 4 layers, and the threshold is calibrated using borehole data:

[0168] Strong weathering layer moderate weathering layer Weakly weathered layer micro-weathering layer .

[0169] The core parameters for lateral zoning were acquired through ground mapping and geophysical exploration to obtain lateral (from near-water to far-water) degradation characteristic parameters, including:

[0170] Water level influencing parameters: Reservoir water level fluctuation range ( ), the horizontal distance from a certain point to the normal water level line ( ), duration of historical submersion ( );

[0171] Fracture parameters: fracture density ( (strips / m), average opening ( (mm)

[0172] Deterioration product parameters: thickness of weathering and spalling on the rock mass surface ( (mm), soluble mineral content ( ,%).

[0173] Taking into account factors such as water level influence and fracture development, a lateral deterioration index is constructed:

[0174] ;

[0175] In the formula, (Influence coefficient of flooding duration) (Distance attenuation coefficient); Range of values , A higher value indicates more severe degradation;

[0176] The partitioning threshold is: Severely degraded area: Moderately deteriorated area: Slightly deteriorated area: Undeteriorated area: .

[0177] In step S3, mechanical parameters are assigned to rock mass units of different degradation levels and zones according to the principle of directional progressive degradation, which decreases from the near-water side to the far-water side and from the surface to the deep layer. The specific parameter assignments are as follows:

[0178] Complete rock mass mechanical parameters were obtained from laboratory tests in the undeteriorated zone (deep part on the far side of the water).

[0179] The cohesion and internal friction angle of the mildly deteriorated zone are assigned 80%-90% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 85%-95% of the parameters of the undeteriorated zone.

[0180] The cohesion and internal friction angle of the moderately deteriorated zone are assigned 60%-80% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 70%-85% of the parameters of the undeteriorated zone.

[0181] The cohesion and internal friction angle of the severely degraded zone (near water surface) are assigned 40%-60% of the parameters of the undegraded zone, and the elastic modulus and compressive strength are assigned 50%-70% of the parameters of the undegraded zone.

[0182] For the specific deteriorated sublayer (fracture-dense area), based on the degree of fracture development, the cohesion and internal friction angle are reduced by 10%-30% from the parameters of the severely deteriorated area, and the influence of the fracture permeability coefficient on the deterioration is also considered. During the assignment process, the parameters of adjacent layers and zones adopt a linear transition method to avoid simulation distortion caused by abrupt parameter changes.

[0183] Please see Figures 2-11 In step S4, the specific process of FLAC3D performing stability analysis is as follows:

[0184] Step S41: In the built-in constitutive model of FLAC3D software (select the Mohr-Coulomb constitutive model or the jointed rock mass constitutive model according to the characteristics of the dangerous rock), input the assigned mechanical parameters, and verify the rationality of the model parameters by comparing them with the stress and displacement data monitored in the field.

[0185] Step S42: Use the strength reduction method combined with time step iteration to simulate the directional gradual deterioration process of the unstable rock. Set the iteration time step (determined according to the deterioration rate, ranging from 0.1 to 1 year / time step). For each iteration time step, update the mechanical parameters of each level and zone according to the preset deterioration rate.

[0186] Step S43: Perform stress distribution analysis, extract stress cloud map for each time step, analyze the distribution characteristics of principal stress, shear stress and tensile stress inside the unstable rock, identify stress concentration areas, and determine the potential failure initiation location;

[0187] Specifically, construct the spatiotemporal index of stress concentration ( ), quantifying the duration and intensity of stress concentration in different regions:

[0188] ;

[0189] In the formula: For the first Stress concentration factor at time step For the total time step, The larger the value, the more significant and longer the stress concentration in the area, indicating a high-risk area for potential damage.

[0190] Extract the principal stress direction angles of the stress concentration area ( ), and the direction of the fracture ( Compare and calculate the directional agreement:

[0191] ;

[0192] when When the value is greater than 0.8, it indicates that the direction of the principal stress is highly consistent with the direction of the crack, and the crack is prone to shear expansion, so it needs to be marked.

[0193] Step S44: Perform strain and displacement analysis, monitor the strain and displacement changes of key parts of the dangerous rock (surface near water, fracture development zone, near bedding plane), plot displacement-time curves and strain-time curves, analyze deformation rate and deformation trend, and determine the maximum displacement value and displacement concentration area.

[0194] Specifically, based on the degradation level classification results, units that meet the following conditions are selected as key monitoring points: degradation sensitivity index S>0.6 (high-level sensitive area), stress concentration factor K>1.2, and crack density λ>3 cracks / m.

[0195] Adaptive monitoring point deployment strategy: The "density gradient deployment method" is adopted, with monitoring points deployed at a spacing of 1m×1m in the extremely sensitive area and at a spacing of 2m×2m in the highly sensitive area, to ensure that the monitoring points are dense in the high-risk area and sparse in the low-risk area.

[0196] The sliding window algorithm is used to fit the trend of the displacement-time curve and extract the feature parameter: curve slope ( ): Reflects the rate of deformation; curvature ( ): Reflects changes in deformation acceleration ( Indicates acceleration. (Indicates deceleration); abrupt change point ( ):when When this occurs, it is determined to be a moment of sudden deformation, which may correspond to the initiation or expansion of cracks.

[0197] Step S45: Perform failure mode identification. By judging the stress state of the elements during the simulation (when the shear stress of an element exceeds the shear strength or the tensile stress exceeds the tensile strength, it is determined to be element failure), and combined with the crack propagation trajectory (followed and drawn by the FLAC3D discrete element module), identify the failure mode of the unstable rock (such as sliding failure, tensile failure, toppling failure or combined failure).

[0198] Specifically, when the element shear stress exceeds the deteriorated shear strength:

[0199] ;

[0200] In the formula, and These represent the deteriorated cohesion and internal friction angle, respectively; when the tensile stress of the unit exceeds the deteriorated tensile strength, then... In the formula, The tensile strength after degradation;

[0201] The damage status of the comprehensive evaluation unit is obtained as follows: ; Indicates unit destruction. The higher the value, the more severe the damage.

[0202] Step S46: Calculate the stability coefficient. Use the strength reduction method to calculate the stability coefficient for each time step (stability coefficient = shear strength / shear stress). When the stability coefficient is ≤1.0, the unstable rock is determined to be in an unstable state. Record the critical time of instability and the corresponding degree of deterioration.

[0203] Specifically, this embodiment introduces a time variable to account for intensity decay caused by degradation:

[0204] ;

[0205] In the formula, ; and The degradation coefficient is... The reduction factor is dynamically adjusted over time; the regional stability coefficient is calculated based on the deterioration zone as follows:

[0206] ;

[0207] In the formula, For the first The stability coefficient of each unit, The total number of regional units; when any partition's Issue warnings in a timely manner. It was determined to be unstable at that time.

[0208] In step S5, the stability analysis results are verified by combining on-site monitoring data (stress monitoring, displacement monitoring), historical geological disaster cases, and model inversion analysis. If the simulated stress and displacement values ​​deviate from the on-site monitoring values ​​by more than 10%, or the predicted failure mode does not match the actual situation, it is necessary to return to step S1 to adjust the parameters or model settings and re-perform the simulation analysis. Based on the stability analysis results, the stability status (stable, basically stable, understability, unstable), potential failure area, instability risk level, and critical triggering conditions (such as specific water level combinations, heavy rainfall) of the unstable rock are identified. Targeted treatment suggestions are proposed for the deterioration characteristics and stability status of different areas, including: grouting reinforcement schemes for severely deteriorated areas near the water, slope reduction and load reduction schemes for surface weathering zones, anti-slide pile installation schemes for potential sliding surfaces, crack sealing treatment schemes for fracture development areas, and layout suggestions for reservoir bank protection projects (such as breakwaters and revetments).

[0209] In step S6, a long-term monitoring system for the stability of unstable rocks on the reservoir bank is established, and stress sensors, displacement sensors, water level sensors, and crack monitoring instruments are deployed to collect data on the mechanical response and environmental parameters of the unstable rocks in real time. The monitoring data is periodically (every 1-2 years) input into the model constructed in step S4 to update the mechanical parameters and boundary conditions, conduct dynamic stability verification, and adjust the treatment plan according to the verification results to achieve closed-loop management of "monitoring-simulation-treatment".

[0210] It is worth noting that the various units included in the above system embodiments are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of each functional unit are only for easy differentiation and are not used to limit the scope of protection of the present invention.

[0211] Furthermore, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium.

[0212] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for analyzing the stability of unstable reservoir bank rocks based on directional progressive deterioration, characterized in that, Includes the following steps: Step S1: Determine the physical and mechanical properties and boundary conditions of the unstable rocks on the reservoir bank, and construct a geological model of the unstable rocks on the reservoir bank; Step S2: Based on the determined physical and mechanical properties, a model of the unstable rock on the reservoir bank is established using FLAC3D software, and the mesh is generated. Step S3: Assign mechanical parameters to the rock mass units in the model according to the principle of directional progressive deterioration. The mechanical parameters change gradually with the layers to simulate the degree of deterioration of different parts of the dangerous rock. Step S4: Based on the established reservoir bank boulders model and the assigned mechanical parameters, perform stability analysis using FLAC3D to obtain stress distribution, strain distribution, and displacement. Step S5: Verify the analysis results and output remediation recommendations; Step S6: Establish a long-term monitoring system for the stability of unstable rocks on the reservoir bank, deploy stress sensors, displacement sensors, water level sensors and crack monitoring instruments, and dynamically update the model.

2. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration as described in claim 1, characterized in that, In step S1, basic geological information of dangerous rocks on the reservoir bank is obtained by combining UAV aerial survey, ground geological mapping, and borehole exploration. Specifically, this includes topography, geological structure, lithology distribution, fracture development characteristics, bedding plane distribution, and the thickness of the weathering zone near the water. At the same time, historical water level change data, meteorological data, and historical geological disaster records of the reservoir area are collected to establish a complete geological information database.

3. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration as described in claim 1, characterized in that, In step S2, the specific process of establishing a reservoir bank dangerous rock model using FLAC3D software based on the basic geological information of the dangerous rocks on the reservoir bank is as follows: Step S21: Select the necessary parameters for FLAC3D modeling from the physical and mechanical parameters obtained from the field survey and indoor tests, including density, elastic modulus, Poisson's ratio, cohesion, internal friction angle, and tensile strength. Clarify the parameter attenuation coefficients for different deterioration levels and create a mapping table for the selected parameters according to the input format requirements of FLAC3D software. Step S22: Start FLAC3D software, create a new project and set the calculation accuracy, initial time step value and constitutive model; establish a geodetic coordinate system, with the X-axis along the reservoir bank, the Y-axis perpendicular to the reservoir bank pointing towards the reservoir area, and the Z-axis perpendicular to the ground upwards; Step S23: Import the topographic data of the dangerous rocks on the reservoir bank obtained in the early stage through UAV aerial survey and ground geological mapping into FLAC3D in DXF format to generate the surface outline of the dangerous rocks and the interface line of the bedrock; using the Block module of FLAC3D, based on the imported outline, construct a three-dimensional geometric model through stretching, cutting and merging operations. Step S24: Determine the mesh reference size, refine the mesh in the deterioration-sensitive area, execute the Mesh command to generate the initial mesh, and use the mesh quality inspection tool built into FLAC3D to calculate the element distortion rate and aspect ratio to adjust the mesh shape; Step S25: Compare the mesh model with the original geological data, check the mesh matching degree of the deterioration layer interface and fracture location, calculate the mesh density difference of different unit groups, and adjust the mesh size; Step S26: Based on the mapping table created in step S21, use the Property command in FLAC3D to batch assign the physical and mechanical parameters of different degradation levels to the corresponding unit groups.

4. The method for analyzing the stability of reservoir bank boulders based on directional progressive deterioration according to claim 3, characterized in that, In step S23, the specific process for generating the surface outline of the dangerous rock and the interface line of the bedrock is as follows: Step S231: Standardize the topographic data of the dangerous rocks on the reservoir bank, and adjust and correct the UAV aerial survey elevation data based on the reservoir area leveling points. Step S232: Perform three-dimensional processing on the fracture data. Based on the fracture orientation and dip angle mapped from the ground, expand the two-dimensional fracture lines (X, Y) into three-dimensional spatial lines (X, Y, Z) using the spatial coordinate transformation formula. Step S233: Set the elevation threshold, construct the surface triangulation network using the Delaunay triangulation algorithm, extract the boundary of the triangulation network as the initial contour line, smooth the initial contour line, and generate the final surface contour line. Step S234: Extract the burial depth of the top surface of the bedrock from the borehole data, combine it with the contour lines of the bedrock interface obtained by geophysical inversion, generate a discrete point set of the bedrock interface, use the Kriging interpolation algorithm to interpolate the discrete point set, generate a continuous bedrock interface surface equation, and cut the intersection line of the bedrock interface and the dangerous rock range as the bedrock interface line. Step S235: Based on the three-dimensional fracture data, generate attributed feature lines in the DXF file according to the "fracture ID-direction-dip angle-length" attribute; based on the thickness of the deteriorated layer revealed by the borehole, generate the interface line of the deteriorated layer using a linear gradient model.

5. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration according to claim 3, characterized in that, In step S25, on the interface of the deteriorated layer, press Sampling points are set up in the grid to extract the interface elevation between the grid model and the borehole data. For each main control fracture, a check point is taken every 2m along the strike. Multiple sampling points are evenly selected on the terrain contour line by the number of penetration units of the fracture line in the grid. The elevation difference between the grid ground and the DSM is extracted. The interface offset, fracture penetration and terrain conformity are calculated and compared with the threshold to determine whether the area is a geometric anomaly area and start the correction process.

6. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration according to claim 1, characterized in that, In step S3, the deterioration layer division adopts a vertical stratification and horizontal partitioning method; wherein, the vertical stratification extends from the surface of the unstable rock to the deep part, and is divided into strongly weathered, moderately weathered, weakly weathered, and slightly weathered layers according to the degree of weathering. The thickness of each layer is determined based on borehole exploration data and weathering zone detection results, and the thickness range is [missing information]. ; The transverse partitions, extending from the near-water side to the far-water side, are divided into severely deteriorated, moderately deteriorated, slightly deteriorated, and undeteriorated zones according to their degree of degradation. The partition boundaries are determined based on the thickness of the weathering zone and the density of fissures on the near-water side. The width of each partition is [missing information]. .

7. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration as described in claim 1, characterized in that, In step S3, mechanical parameters are assigned to rock mass units of different degradation levels and zones according to the principle of directional progressive degradation, which decreases from the near-water side to the far-water side and from the surface to the deep layer. The specific parameter assignments are as follows: Complete rock mass mechanical parameters for the undeteriorated zone were obtained using laboratory tests. The cohesion and internal friction angle of the mildly deteriorated zone are assigned 80%-90% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 85%-95% of the parameters of the undeteriorated zone. The cohesion and internal friction angle of the moderately deteriorated zone are assigned 60%-80% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 70%-85% of the parameters of the undeteriorated zone. The cohesion and internal friction angle of the severely deteriorated zone are assigned 40%-60% of the parameters of the undeteriorated zone, and the elastic modulus and compressive strength are assigned 50%-70% of the parameters of the undeteriorated zone.

8. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration according to claim 1, characterized in that, In step S4, the specific process of FLAC3D performing stability analysis is as follows: Step S41: Input the assigned mechanical parameters into the built-in constitutive model of FLAC3D software, and verify the rationality of the model parameters by comparing them with the stress and displacement data monitored on site. Step S42: The strength reduction method combined with time step iteration is used to simulate the directional and gradual deterioration process of the unstable rock. The iteration time step is set, and the mechanical parameters of each level and zone are updated according to the preset deterioration rate in each iteration time step. Step S43: Perform stress distribution analysis, extract stress cloud map for each time step, analyze the distribution characteristics of principal stress, shear stress and tensile stress inside the unstable rock, identify stress concentration areas, and determine the potential failure initiation location; Step S44: Perform strain and displacement analysis, monitor strain and displacement changes in key parts of the unstable rock, plot displacement-time curves and strain-time curves, analyze deformation rate and deformation trend, and determine the maximum displacement value and displacement concentration area. Step S45: Perform failure mode identification. By judging the stress state of the elements during the simulation process and combining it with the crack propagation trajectory, identify the failure mode of the unstable rock. Step S46: Calculate the stability coefficient. Use the strength reduction method to calculate the stability coefficient for each time step. When the stability coefficient is ≤1.0, the unstable rock is determined to be in an unstable state. Record the critical time of instability and the corresponding degree of deterioration.

9. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration according to claim 1, characterized in that, In step S5, the stability analysis results are verified by combining on-site monitoring data, historical geological disaster cases, and model inversion analysis. If the simulated stress and displacement values ​​deviate from the on-site monitoring values ​​by more than 10%, or the predicted failure mode does not match the actual situation, it is necessary to return to step S1 to adjust the parameters or model settings and re-perform the simulation analysis. Based on the stability analysis results, the stability state, potential failure area, instability risk level, and critical triggering conditions of the unstable rock are determined. Based on the deterioration characteristics and stability status of different areas, targeted treatment suggestions are proposed, including: grouting reinforcement scheme for severely deteriorated areas near the water, slope reduction and load reduction scheme for surface weathering zone, anti-slide pile installation scheme for potential sliding surface, crack sealing treatment scheme for cracked areas, and layout suggestions for reservoir bank protection projects.

10. The method for stability analysis of reservoir bank boulders based on directional progressive deterioration according to claim 1, characterized in that, In step S6, a long-term monitoring system for the stability of unstable rocks on the reservoir bank is established, and stress sensors, displacement sensors, water level sensors and crack monitoring instruments are deployed to collect data on the mechanical response and environmental parameters of the unstable rocks in real time. The monitoring data is periodically input into the model constructed in step S4 to update the mechanical parameters and boundary conditions, and to conduct dynamic verification of stability. The treatment plan is adjusted according to the verification results.

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