Optimization method for zoning design of dam seepage prevention curtain in complex and unfavorable geological structure

Abstract

The application provides a dam anti-seepage curtain zoning design optimization method for complex adverse geological structure, relates to the technical field of hydraulic engineering and comprises the following steps: S1, obtaining a groundwater critical line and a relative aquiclude critical line of a dam site area, and establishing a polar coordinate system with a dam abutment as a pole point and a dam axis as a pole axis; S2, in an angle range estimated according to the dam abutment topography and geology and the curtain extension direction, finding the nearest point to the dam abutment on the groundwater and relative aquiclude critical lines respectively, and connecting the point and the dam abutment to determine the anti-seepage curtain line and the extension length; S3, based on the stratum permeability and the adverse geological structure distribution of the dam site area, dividing the anti-seepage curtain into n design regions; and S4, establishing a dam three-dimensional seepage field finite element model containing the anti-seepage curtain line and the zoning information, setting an initial depth for each design region, calculating a total leakage Q, and continuously iterating until Q<=Q_limit. The application improves the reliability and safety of the curtain design.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to an optimized method for the zoned design of anti-seepage curtain walls for dams with complex and unfavorable geological structures. Background Technology

[0002] In the construction of water conservancy and hydropower projects, the seepage prevention system is a key component to ensure the safe and stable operation of the dam. As the core of the dam foundation seepage prevention system, the seepage prevention curtain mainly functions to cut off or reduce the leakage of reservoir water into the dam foundation and banks, reduce the uplift pressure at the dam base, and prevent seepage damage to the foundation. Its rational design directly determines the seepage prevention effect of the dam and the economy of the project.

[0003] In practical engineering projects, the geological environment in which dams are located is often very complex, frequently encountering complex and unfavorable geological structures such as fault fracture zones, karst caves, and highly permeable layers. These structures are characterized by high permeability, discontinuity, and uneven distribution, greatly increasing the difficulty of seepage prevention in the dam foundation. If the seepage prevention curtain is not scientifically designed to address these complex geological conditions, it can easily lead to concentrated leakage of reservoir water, and even endanger the safety of the dam.

[0004] However, current design methods for dam seepage prevention curtains in complex geological structures still have the following significant shortcomings: First, existing technologies lack systematic quantitative optimization methods for determining the route and length of the anti-seepage curtain. Current route designs largely rely on qualitative judgments based on engineering experience, especially when facing complex geological structures and groundwater distribution, making it difficult to accurately determine the optimal axial direction and extension length of the anti-seepage curtain on both sides of the dam. This experience-based design often fails to accurately find the optimal connection point between the anti-seepage curtain and the groundwater boundary or the relative impermeable layer, resulting in an incomplete anti-seepage seal or unnecessary engineering work due to excessively long routes.

[0005] Secondly, regarding the design of the depth of the anti-seepage curtain, existing technologies typically employ a "one-size-fits-all" empirical method or a simple estimation approach. The design often overlooks the significant differences in geological conditions between the dam foundation, left bank, and right bank, failing to fully consider the permeability of various strata in the foundation and the specific distribution of unfavorable geological structures such as faults and fracture zones. This uniform design easily leads to two extreme consequences: first, the anti-seepage curtain depth is insufficient in some areas with poor geological conditions, failing to effectively cut off seepage channels and resulting in poor anti-seepage effects; second, the anti-seepage curtain depth is excessive in some areas with better geological conditions, causing a huge waste of engineering resources.

[0006] Finally, regarding the design of the thickness of the seepage barrier curtain, existing technologies also lack a scientifically sound calculation basis. Currently, the curtain thickness is mostly set directly based on the engineering grade or analogous experience, without being verified against the actual seepage field conditions. If the designed thickness is too large, it will significantly increase the cost of grouting materials and reduce construction efficiency; if the designed thickness is too small, it will lead to an increased seepage gradient under high water head, potentially causing seepage damage such as piping, seriously threatening the seepage stability and seepage prevention safety of the curtain.

[0007] In summary, existing methods for designing cut-off curtains generally suffer from problems when dealing with complex and unfavorable geological structures. These problems include reliance on experience in designing cut-off lines, depths, and thicknesses; lack of systematic optimization; and insufficient consideration of regional geological differences. Therefore, there is an urgent need for a design method that can refine the zoning and optimize multi-dimensional parameters of the cut-off curtain based on the specific geological structure of the dam site area. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for optimizing the design of zonal anti-seepage curtains for dams with complex and unfavorable geological structures. This method scientifically determines the curtain route by establishing a polar coordinate system, zons the dam based on geological conditions, and couples this with three-dimensional seepage field finite element analysis to iteratively optimize the curtain depth and thickness. Ultimately, it achieves the dual control of leakage and seepage stability with minimal engineering cost.

[0009] To achieve the above-mentioned objectives, this invention provides a method for optimizing the zonal design of dam seepage prevention curtains for complex and unfavorable geological structures, comprising the following steps: S1. Route Determination: Obtain the groundwater critical line and the relative aquitard critical line in the dam site area. Establish a polar coordinate system. S2. Optimization of the minimum distance seepage prevention line based on weighted equivalent seepage path: Construct a three-dimensional engineering geological model covering the seepage prevention area of ​​the dam, and divide the three-dimensional engineering geological model into several geological grid units; calibrate the comprehensive weighting coefficient of each geological grid unit based on the geological risk and construction cost of each geological grid unit; generate several candidate curtain lines within the spatial range that meets the preset seepage prevention baseline requirements; along the main control seepage path of each candidate curtain line, accumulate the product of the geometric length of each geological grid unit passed through and its corresponding comprehensive weighting coefficient to obtain the weighted equivalent seepage path length corresponding to each candidate curtain line. Search for the weighted equivalent seepage path length among the candidate curtain lines. The smallest curtain line is selected as the initial optimal anti-seepage curtain line, thereby determining the zoned lines and extension lengths of the anti-seepage curtain. S3. Curtain Zoning: Based on the distribution of strata permeability and unfavorable geological structures in the dam site area, the seepage prevention curtain is divided into n design zones. S4. Depth Optimization: Establish a three-dimensional finite element model of the dam seepage field containing the seepage barrier line and zoning information, set an initial depth for each design area, and calculate the total seepage rate Q. x If Q x The leakage rate is greater than the preset allowable leakage amount Q. 限 If so, increase the depth of one or more design zones that contribute the most to the total leakage, and recalculate the leakage until Q is reached. x ≤Q 限 If the depth adjustment requires cutting off the fault or fracture zone, the adjusted depth must meet the following requirements: l i ≥max( ql i , pl i ),in l i Let i be the depth of the i-th design region. ql i Let be the distance from the top elevation of the seepage-proof curtain in the i-th design area to the relative water-proof layer of the foundation. pl i The curtain depth is the depth at which the i-th design region completely cuts off the unfavorable geological structure of the region. S5. Thickness Optimization: Based on the depth-optimized three-dimensional seepage field finite element model, calculate the maximum seepage gradient J for each design area; if J is greater than the preset allowable seepage gradient J... 允 If J ≤ J 允 Then reduce the thickness of the design area and recalculate the permeability gradient until a value satisfying J ≤ J is found. 允 And the optimal solution with the minimum thickness.

[0010] Furthermore, in step S1, the groundwater critical line is determined through long-term observation well data or hydrogeological surveys; the relative impermeable layer critical line is determined through a combination of geological borehole data and geophysical exploration data.

[0011] Further, in step S1, the step of establishing the polar coordinate system includes: S101. Geological Zoning and Target Identification: Analyze the geological survey data of the entire dam section to identify the unfavorable geological structures, spatial distribution, and main seepage path direction of the following river-guided faults, muddy weak interlayers, karst conduits in soluble rock areas, dense dissolution fissure zones, deep unloading fissure zones on the dam abutments, and strongly weathered zones. Divide the entire dam section into several independent geological zones. S102. Polar Point Determination: Based on the unfavorable geological structure types within each independent geological zone, and using the seepage control pole as the principle, the polar coordinate poles of each independent geological zone are determined differentially. For conventional uniform permeable strata zoning, the pole point is selected at the intersection of the dam abutment mountain and the relative impermeable layer at the corresponding elevation, and is the minimum control boundary point that meets the design requirements for seepage flow around the dam. For river-guided faults or muddy soft interlayer zones, the pole point is selected at the intersection of the fault or muddy soft interlayer with the dam axis and the relative impermeable layer. For karst conduits or dense dissolution fissure systems in soluble rock areas, the extreme points are selected at the water-impermeable boundary of the reservoir-side inlet and the water-impermeable boundary of the downstream outlet of the karst conduit system, or at the intersection of the concentrated development center of the dense dissolution fissure zone and the relative water-impermeable layer. For the deep unloading fracture zone or strongly weathered zone of the dam abutment, multiple levels of poles are set up at different elevations along the vertical direction. Each level of pole is selected at the intersection of the bottom boundary of the unloading fracture zone or strongly weathered zone and the relative impermeable layer at the corresponding elevation. S103, Polar coordinate parameter mapping: Using the poles established in each zone as the radiation control points of the seepage prevention curtain line, the polar angle corresponds to the direction of the seepage prevention curtain line, and the polar diameter corresponds to the extension length or depth of the seepage prevention curtain line, a differentiated polar coordinate system for each independent geological zone is established. S104. Curtain Line Splicing and Closure: Under the polar coordinate system of each independent geological zone, the corresponding seepage prevention curtain line is designed independently, and the seepage prevention curtain lines of each zone are spatially spliced. Each pole is located within the relative water-impermeable layer, so that the spliced ​​seepage prevention curtain line and the relative water-impermeable layer together form a continuous and closed seepage prevention and closure system.

[0012] Furthermore, the specific implementation steps of step S2 include: S201. Refined 3D Mesh Modeling: Based on borehole, adit, and 3D geophysical data of the dam site area, a 3D engineering geological model is constructed to delineate the spatial boundaries of unfavorable geological structures; based on the design reference seepage field, the 3D engineering geological model is divided into cubic mesh units with side lengths of 0.5m to 2m, which serve as the geological mesh units. S202, Dual-control weighted parameter calibration: Calculate the geological risk coefficient for each of the geological grid units. and construction cost coefficient The geological risk coefficient is mentioned above. The construction cost coefficient was obtained by weighted calculation using the analytic hierarchy process (AHP) based on the formation permeability factor, the type and scale factor of unfavorable geological structures, and the risk level factor of seepage failure; It is obtained by weighted calculation of factors such as formation groutability and construction difficulty, curtain hole depth and construction conditions, and special process requirements. S203, Dynamic Weighting and Normalization: Introducing Risk Weight Coefficient and cost weighting coefficient And satisfy Dynamic adjustment based on the level of hydraulic structures, dam height, and geological complexity. and The value of the geological risk coefficient is determined, and the geological risk coefficient is determined. and construction cost coefficient Perform normalization processing; S204, Weighted Equivalent Seepage Path Calculation: Using the formula Calculate the weighted equivalent seepage path length for each candidate curtain line. ,in The first in the seepage path The geometric length of each geological grid cell and The first Geological risk coefficient and construction cost coefficient corresponding to each geological grid unit; S205. Numerical Simulation Verification and Iteration: Perform a three-dimensional seepage field numerical simulation on the initially selected optimal seepage barrier line to verify whether the seepage flow rate of the dam foundation, the uplift pressure of the dam body, the seepage gradient of key strata, and the seepage flow rate around the dam meet the design specifications; if not, increase the risk weight coefficient of the corresponding zone. Then return to step S204 to recalculate iteratively until all safety indicators meet the standards; S206. Integrated Verification of the Entire Dam Section: The curtain lines in each geological zone, verified by numerical simulation and meeting safety standards, are spatially spliced ​​and integrated to form a continuous seepage prevention curtain running through the entire dam section. A comprehensive seepage field simulation analysis and a double verification of the engineering economics are then performed on the integrated continuous seepage prevention curtain. The verification checks whether the overall dam foundation seepage flow, overall dam body uplift pressure, seepage gradient of key strata, and overall seepage flow around the dam section fully meet the seepage prevention design requirements and specifications, while also considering the construction cost coefficient. The total amount of work for the entire project was reviewed, and the final verification of the continuous anti-seepage curtain for the entire dam section was completed.

[0013] Furthermore, in step S3, the principles for curtain zoning include: within the same design area, the variation in elevation of the top plate of the waterproof layer is within a small range allowed by the project, and unfavorable geological structures are spatially continuous. The "small range allowed by the project" usually refers to a variation of less than 10 meters, which can be determined comprehensively based on the regional geological homogeneity, survey accuracy, and project importance.

[0014] Further, in step S4, the iterative formula for depth optimization is: ,in Let x be the depth of the i-th design region after the x-th optimization. Let the depth of the i-th design region after the (x-1)-th optimization be denoted as . This is an increment for adjusting the depth based on the thickness of the geological unit and the calculation accuracy.

[0015] Furthermore, in step S5, the logic for the bidirectional thickness adjustment is as follows: using the current thickness t as a reference, the thickness is increased or decreased by a preset step size Δt. After each adjustment, the three-dimensional seepage field is recalculated, and the maximum seepage gradient J and J' are determined. 允 The relationship continues until a condition is found that satisfies J ≤ J 允 The critical minimum thickness.

[0016] Furthermore, in steps S4 and S5, the boundary conditions of the finite element model of the three-dimensional seepage field of the dam are set as follows: the upstream boundary is set as a known head boundary, the downstream boundary is set as a known head or a free overflow boundary, and the bottom and side boundaries of the model are set as water-blocking boundaries or known head gradient boundaries.

[0017] Further, in step S4, the allowable leakage amount Q 限 The determination is based on a comprehensive analysis of reservoir function, downstream ecological water demand, and economic factors.

[0018] Furthermore, in step S5, the permeability gradient J 允 The safety factor is determined based on the impermeability of the curtain material, the erosion resistance of the contact surface, and the safety factor.

[0019] Furthermore, the unfavorable geological structures include one or more of the following: faults, fracture zones, densely fractured zones, or karst development zones.

[0020] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: 1. Scientific and reasonable route determination: By establishing a polar coordinate system and searching for the minimum distance point, the curtain route is determined so that the curtain can connect the dam abutment and key geological boundaries (groundwater critical line, relative impermeable layer critical line) with the shortest path, reducing unnecessary curtain length from the source and improving economy.

[0021] 2. System optimization of the design process: The curtain design is decomposed into four logically clear steps: route determination, zoning, depth optimization, and thickness optimization. Three-dimensional seepage field finite element analysis is introduced as a quantitative evaluation tool, realizing the systematization and quantification of the design process.

[0022] 3. Depth Optimization Balancing Safety and Economy: Depth optimization aims to control the total leakage volume and specifically considers the depth requirement for cutting off unfavorable geological structures (l_i ≥ max(q_li, p_li)), ensuring the effectiveness of the curtain's seepage prevention. Iterative calculations are used to find the minimum depth that meets leakage control requirements, avoiding waste caused by excessive depth.

[0023] 4. Precise and efficient thickness optimization: Thickness optimization aims to control the local permeability gradient and prevent permeability damage. It adopts a two-way adjustment strategy (increasing or decreasing) to find the minimum thickness that meets the permeability stability requirements, thus achieving precise control of material usage.

[0024] 5. Adaptable to complex geological conditions: Through zoning design, the differences in geological conditions in different regions (such as permeability and distribution of unfavorable structures) can be fully considered, realizing personalized design of "one policy for one site", which is especially suitable for dam site areas with complex and unfavorable geological structures such as faults and fracture zones.

[0025] 6. High reliability of results: The entire optimization process is based on three-dimensional seepage field numerical simulation, which can truly reflect the spatial distribution of seepage. The optimization results are closer to the actual engineering situation, which improves the reliability and safety of curtain wall design. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the seepage-proof curtain partitions along the seepage-proof axis in an embodiment of the present invention; Figure 2 This is a schematic diagram showing the route and length of the anti-seepage curtain on both sides of the dam in an embodiment of the present invention.

[0027] Attached diagram labels: 1-Dam body; 2-Seepage barrier curtain; 3-Groundwater level; 4-Relative impermeable layer line; 5-1-Fault A; 5-2-Fault B; 5-3-Fault C; 5-4-Fault D; 6-Karst zone. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more complete description of this application will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of the present invention.

[0029] It should be noted that the terms "vertical," "horizontal," "up," "down," "left," "right," and similar expressions used in this article are for illustrative purposes only and do not represent the only possible implementation.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0031] Example. An optimization method for the zonal design of dam seepage prevention curtains for complex and unfavorable geological structures, such as... Figure 1 As shown, the method mainly includes the following steps: S1. Route Determination First, it is necessary to obtain the key geological and hydrological boundaries of the dam site area. The "groundwater critical line" refers to the boundary line where the groundwater level is basically level with the reservoir water level, which can be determined by deploying long-term observation wells or conducting specialized hydrogeological surveys. The "relative impermeable layer critical line" refers to the distribution boundary line of rock strata (such as intact bedrock or mudstone layers) with significantly reduced permeability that can serve as seepage prevention support in the dam site area, which needs to be determined through comprehensive analysis and inference of geophysical data such as geological boreholes, seismic wave methods, and electrical resistivity tomography.

[0032] like Figure 2 As shown, this coordinate system transforms complex two-dimensional planar positional relationships into angles and distances, facilitating minimum distance searches and selecting the maximum angle of the left bank seepage prevention curtain axis. θ max左 The maximum angle of the right bank seepage prevention curtain axis θ max右 The steps to establish a polar coordinate system include: S101. Geological Zoning and Target Identification: Analyze the geological survey data of the entire dam section to identify the unfavorable geological structures, spatial distribution, and main seepage path direction of the following river-guided faults, muddy weak interlayers, karst conduits in soluble rock areas, dense dissolution fissure zones, deep unloading fissure zones on the dam abutments, and strongly weathered zones. Divide the entire dam section into several independent geological zones. S102. Determination of Core Target Extremes: Based on the unfavorable geological structures within each independent geological zone, and taking the seepage control core target as the principle, the polar coordinate extremes of each independent geological zone are determined differently. For conventional uniform permeable strata zoning, the pole point is selected at the intersection of the dam abutment mountain and the relative impermeable layer at the corresponding elevation, and is the minimum control boundary point that meets the design requirements for seepage flow around the dam. Instead of using vague endpoints of the dam abutment topography or dam axis, the extreme points are strictly located at the corresponding design elevations, taking into account the dam abutment hillside and permeability. The intersection of the relative impermeable layers; this intersection point is also checked as the minimum control boundary for the seepage flow around the dam to meet the engineering seepage prevention design requirements; only one pole is set at each of the two key elevations, the dam crest elevation and the dam foundation elevation, forming a dual-pole control system. With this intersection pole as the radiation center, the direction of the curtain line is controlled by the polar angle, and the length of the curtain line extending into the mountain is controlled by the polar diameter; Because the extreme point precisely locks the minimum control boundary of seepage around the dam, the established polar coordinate system can guide the curtain line to form a fan-shaped curtain that precisely controls shallow seepage around the dam, effectively avoiding the curtain line from blindly and meaninglessly extending into the depths of the mountain, and greatly reducing the amount of ineffective curtain grouting work.

[0033] For river-guided faults or weak, muddy interlayers, the pole point is selected at the double intersection of the fault or muddy interlayer with the dam axis and the relative impermeable layer. If the fault penetrates the entire dam foundation, the double pole points at the dam shoulder are abandoned; instead, the main pole points are established at the intersection points of the fault with the top plate of the relative impermeable layer on the hanging wall and footwall of the dam foundation, respectively. If the fault develops only on one side of the dam shoulder, the zoning pole point is set only at the "fault-impermeable layer intersection point" on the bank where the fault is located, while the seepage prevention boundary control point of the dam shoulder in Example 1 is still used on the other bank. A polar coordinate system is established with the "fault-impermeable layer intersection point" as the main pole point, the initial extension direction of the polar radius is adjusted to extend along the fault strike, and the radiation range of the polar angle is set to completely cover the width of the entire geological influence zone of the fault.

[0034] The fan-shaped curtain derived from this polar coordinate system can cover 100% of the fault influence zone, achieving high-density and targeted sealing of key leakage channels in the fault. This solves the industry problem of poor curtain line overlap and leakage sealing failure in the fault zone caused by the long distance and insufficient control precision when the traditional large fan-shaped curtains on both banks of the dam cross the fault.

[0035] For karst conduits or dense dissolution fissure systems in soluble rock areas, poles are selected at the impermeable boundaries of the reservoir-side inlet and downstream outlet of the karst conduit system, or at the intersection of the concentrated development center of the dense dissolution fissure zone and the relative impermeable layer. For karst main conduits, primary poles are set at the impermeable boundary of the reservoir-side inlet, and secondary poles are set at the impermeable boundary of the downstream outlet. For diffuse dense dissolution fissure zones, zonal poles are set at the intersection of the concentrated development center of the fissure zone and the relative impermeable layer. A polar coordinate system is established with the reservoir-side primary pole as the core, the polar radius extends along the conduit direction, and interacts with the downstream secondary pole coordinate system to guide the curtain line to form a closed curtain ring around the karst system. For areas with multiple independent karst systems, sub-zones are divided according to the spatial distribution of the karst systems, and each sub-zone independently sets poles and establishes a polar coordinate system.

[0036] It achieves "one system, one coordinate, one pipeline, one closed loop". The radial and annular curtains can accurately cut off the concentrated seepage path of the karst pipeline system and accurately intercept diffuse leakage in dense fissure zones, completely avoiding the serious defects of traditional dam abutment double poles that result in incomplete coverage of distant karst channels and uncontrolled seepage around the dam.

[0037] For the deep unloading fracture zone or strongly weathered zone of the dam abutment, multiple levels of poles are set up vertically at different elevations. Each level of pole is selected at the intersection of the bottom boundary of the unloading fracture zone or strongly weathered zone and the relative impermeable layer at the corresponding elevation. Based on the vertical spatial distribution characteristics of the unloading zone determined by geological survey, the traditional single-point pole design of the dam abutment is changed. Vertically, at four levels—dam crest elevation, half dam height elevation, dam foundation elevation, and bottom boundary elevation of the unloading zone—the intersection of the bottom boundary of the unloading zone and the relative impermeable layer at the corresponding elevation is selected as the pole of that elevation level. At each elevation level, a two-dimensional polar coordinate system is independently established with its respective intersection point as the pole. The polar angle is designed to extend into the deep layers of the mountain, and the curtain line extends into the mountain along the polar diameter, thus constructing a multi-level, three-dimensional polar coordinate control system in space.

[0038] The multi-level polar coordinate system can guide the curtain line to precisely penetrate deep into the mountain according to the shape changes of the unloading zone, so that the seepage prevention curtain can perfectly close with the relative impermeable layer in the deep space. It successfully solves the engineering pain point of traditional single-point polarization, which can only control shallow layers and is powerless to control deep seepage.

[0039] S103, Polar coordinate parameter mapping: Using the poles established in each zone as the radiation control points of the seepage prevention curtain line, the polar angle corresponds to the direction of the seepage prevention curtain line, and the polar diameter corresponds to the extension length or depth of the seepage prevention curtain line, a differentiated polar coordinate system for each independent geological zone is established. S104. Curtain Line Splicing and Closure: Under the polar coordinate system of each independent geological zone, the corresponding seepage prevention curtain line is designed independently, and the seepage prevention curtain lines of each zone are spatially spliced. Each pole is located within the relative water-impermeable layer, so that the spliced ​​seepage prevention curtain line and the relative water-impermeable layer together form a continuous and closed seepage prevention and closure system.

[0040] S2. Minimum distance optimization includes the following steps: S201: Refined Modeling and Unit Division of 3D Geological Models Based on borehole, adit, and 3D geophysical data from the dam site area, a 3D engineering geological model covering the dam foundation, both banks of the dam abutment, and the reservoir bank near the dam was constructed. This model can accurately delineate the spatial distribution, occurrence, scale, and impact range of all complex and unfavorable geological structures.

[0041] Based on the design reference seepage field, the three-dimensional engineering geological model is divided into cubic grid cells with side lengths of 0.5~2m. Each grid cell corresponds to a unique geological attribute, and the initial values ​​of the basic parameters are assigned.

[0042] S202: Weighted System Parameter Calibration and Normalization Following the multi-factor hierarchical assignment method, the geological risk coefficient for each grid cell was determined. and construction cost coefficient The calculation and assignment of values ​​are performed, and the risk weight coefficients for each zone are determined based on the engineering safety level and the geological conditions of the zone. Cost weighting coefficient This completes the parameter normalization process. The specific quantization and assignment methods are as follows: Geological risk coefficient Calculation and calibration Geological risk coefficient As the core control dimension, the value range is: The higher the value, the higher the risk. Three main control factors were selected, and their weights were determined using the analytic hierarchy process (AHP) to assign values ​​to each factor. The formula for calculating the geological risk coefficient of a single unit is as follows: The hierarchical assignment rules for each main control factor are as follows for a single geological grid unit: Formation permeability (Weight percentage 40%): Extremely permeable layer Assign a value of 1.0; Highly permeable layer ( Assign a value of 0.7; Medium permeability layer ( Assign a value of 0.4; for the weakly permeable layer ( Assign the value 0.1.

[0043] Unfavorable geological structures and their scale (weight 35%): Through-flow faults and karst main channels are assigned a value of 1.0; Non-through-flow faults and dense dissolution fissure zones are assigned a value of 0.6; Localized muddy weak interlayers and shallow unloading fissures are assigned a value of 0.3; Intact bedrock is assigned a value of 0.05.

[0044] Risk level of seepage failure (weighting 25%): Piping / soil bleed critical slope < design seepage slope (high risk) assigned a value of 1.0; critical slope = 1~2 times the design slope (medium risk) assigned a value of 0.5; critical slope > 2 times the design slope (low risk) assigned a value of 0.1.

[0045] Construction cost coefficient Calculation and calibration Construction cost coefficient For the economic optimization dimension, the value range is: The higher the value, the higher the construction cost. The construction difficulty, technological requirements, and construction period of curtain grouting under different geological conditions are quantified. Three main control factors are selected and assigned values. The formula for calculating the single-unit construction cost coefficient is as follows: The hierarchical assignment rules for each main control factor are as follows for a single geological grid unit: Grouting suitability and construction difficulty (weight 50%): Karst development zone, fracture zone (requires repeated grouting, waiting for setting, special grout) assigned 1.0; fractured bedrock (requires segmented grouting) assigned 0.6; intact hard bedrock (conventional grouting is sufficient) assigned 0.2.

[0046] Curtain hole depth and construction conditions (weight 30%): Ultra-deep holes (depth > 100m) and steep slope construction are assigned a value of 1.0; medium-deep holes ( Assign a value of 0.5; shallow hole (hole depth is...) The construction value for the flat section of the riverbed is assigned as 0.3.

[0047] Special process requirements (weighting 20%): Advanced exploration, directional drilling, and chemical composite grouting are assigned a value of 1.0; high-pressure grouting with orifice sealing is assigned a value of 0.4; and conventional atmospheric pressure circulating grouting is assigned a value of 0.1.

[0048] Weight dynamic adjustment mechanism Introducing risk weight coefficient and cost weighting coefficient And satisfy The adjustments will be dynamically made based on the project grade, dam safety level, and geological complexity in different geological zones. The specific adjustment rules are as follows: Corresponding to Class 1 permanent hydraulic structures, high dams (dam height > 70m), and extremely high-risk geological areas: Take a value of 0.7~0.8. Take a value of 0.2~0.3; Corresponding to Class 2-3 hydraulic structures, medium and low dams, and medium-risk geological areas: Take a value of 0.5~0.6. Take a value of 0.4~0.5; Corresponding to intact bedrock regions without large-scale unfavorable structures: Take 0.4, Take 0.6.

[0049] S203: Definition and Calculation of Weighted Equivalent Seepage Path Length Weighted equivalent seepage path length Replacement of traditional geometric seepage length As the core criterion of the "minimum distance principle", the calculation formula is as follows: In the formula, The first in the seepage path The geometric length of each grid cell, , The geological risk coefficient and construction cost coefficient are for the corresponding grid units.

[0050] S204: Based on minimum Preliminary selection of the curtain line of value For each geological zone, all candidate curtain lines that meet the seepage prevention baseline requirements are generated. The seepage prevention baseline requirement is that the curtain line extends into the relatively impermeable layer. And the design seepage gradient The strata allow for a gradient.

[0051] Calculate the weighted equivalent seepage path length for each candidate curtain line corresponding to the main control seepage path. Values, from which to filter The curtain line with the smallest value is selected as the initial optimal solution for that partition, thus achieving the minimum distance principle optimization for partitioning.

[0052] S205: Verification and Iterative Optimization of Numerical Simulation of Seepage Field For the initially selected curtain line of the entire dam section, a three-dimensional seepage field numerical simulation was conducted to verify whether the seepage flow at the dam foundation, the uplift pressure in the dam body, the seepage gradient in key strata, and the seepage flow around the dam meet the specifications and design requirements. If the numerical simulation verification finds that the safety requirements are not met, the risk weight coefficient of the corresponding zone will be increased. And return to steps three and four for iterative calculation. The values ​​are then initially selected until all safety indicators meet the standards.

[0053] S206: Integration and Final Verification of the Entire Dam Section Scheme The curtain lines in each geological zone, verified by numerical simulation and meeting safety standards, are spatially spliced ​​and integrated to form a continuous seepage barrier curtain running through the entire dam section. A comprehensive seepage field simulation analysis and engineering economic verification are then performed on the integrated continuous seepage barrier curtain. The overall dam foundation seepage flow, overall dam body uplift pressure, seepage gradient of key strata, and overall seepage flow around the dam section are verified to fully meet the seepage prevention design requirements and specifications, based on the aforementioned construction cost coefficient. The total project volume was reviewed, and the final verification of the continuous anti-seepage curtain for the entire dam section was completed. The verification ensured that the optimized dam section scheme, compared with the traditional pure geometric minimum distance scheme, improved the seepage control safety factor by more than 10% while the project cost did not increase or even decreased, thus completing the optimization of the entire minimum distance principle scheme.

[0054] S3, Curtain Zone The impermeable curtain should not be uniform, but should be designed in zones according to differences in geological conditions. Based on the curtain line determined in steps S1 and S2, and combined with detailed geological survey data (such as the permeability q-value profile obtained from borehole water pressure tests, and the spatial distribution of faults / fracture zones revealed by three-dimensional geological models), the entire curtain is divided into n design zones (e.g., Figure 1 (①,②,③, …).

[0055] The core principle of zoning is that geological conditions should be relatively uniform within the same design area. Specifically, this can be quantified as follows: the variation in elevation relative to the top of the impermeable layer within the area should be within a small range allowed by engineering (usually less than 10 meters), and the main unfavorable geological structures (such as a fault) should be spatially continuous within the area. Significant geological differences exist between different areas, such as different permeability levels, and different sizes or properties of developed faults. After zoning, each area will serve as an independent unit for subsequent depth and thickness optimization.

[0056] S4, Deep Optimization The goal of this step is to determine the minimum curtain depth required for each zone to meet the total leakage control requirements.

[0057] 1. Model Establishment: Based on the dam structure, foundation rock mass, and the determined curtain flow path and zones, a three-dimensional finite element model of the dam's seepage field is established. The model is based on Darcy's law, treating the rock mass and curtain material as anisotropic porous continuous media. The rock mass permeability tensor is assigned values ​​based on geological zoning and pressure water test results. The permeability coefficient of the curtain zone is set as a homogeneous, isotropic, low-permeability coefficient based on the grouting material and grouting process effects. The model uses tetrahedral or hexahedral elements for meshing, with mesh refinement in the curtain and surrounding areas to ensure computational accuracy. Commercial finite element software (such as ABAQUS, COMSOL) or a custom program can be used. The model boundary conditions must be appropriately set: the upstream dam face and reservoir basin boundary are set to a known head (corresponding to normal storage level, etc.); the downstream dam toe and surface are set to a known head (tailwater level) or free overflow boundary; the bottom and left and right sides of the model are set to impermeable boundaries or known head gradient boundaries according to actual conditions.

[0058] 2. Setting Initial Values ​​and Objectives: Assign an initial depth l_i0 to each design area i (which can be preliminarily determined based on experience or specifications). Set the total allowable seepage limit Q_limit for the entire dam site. The determination of Q_limit needs to comprehensively consider the reservoir's water supply and power generation functions, the ecological base flow demand of the downstream river channel, and the economic analysis of seepage loss.

[0059] 3. Iterative Calculation and Adjustment: Run the finite element model and calculate the total flow rate through the downstream boundary or a specific monitoring section by integration to obtain the total leakage rate Q. Determine whether Q is greater than Q0. 限 .

[0060] If Q>Q 限 This indicates insufficient seepage prevention depth. The curtain depth needs to be increased to lengthen the seepage path and reduce leakage. In this case, priority should be given to increasing the depth of one or more areas that contribute the most to the total leakage. Depth adjustment is performed according to the formula: .in, To adjust the increment, it can be set according to the thickness of the strata (e.g., one layer every 5 meters) and the required calculation accuracy (e.g., 1-5 meters).

[0061] Key constraint: When increasing the depth, if unfavorable geological structures such as faults and fracture zones exist in the area, the adjusted depth should be adjusted accordingly. l i Must meet: l i ≥max( ql i , pl i ),in l i Let i be the depth of the i-th design region. ql i Let be the distance from the top elevation of the seepage-proof curtain in the i-th design area to the relative water-proof layer of the foundation. pl i The curtain depth is the depth at which the i-th design region completely cuts off the unfavorable geological structure of the region. After adjusting the depth, update the curtain geometry parameters in the model, recalculate the leakage rate Q, and perform the judgment again. Iterate in this way until the total leakage rate Q satisfies Q ≤ Q0. 限 .

[0062] If the initial Q ≤ Q 限 Then, we can try to appropriately reduce the depth of certain areas (provided that the geological cutoff requirements are met) to optimize the economy and find the minimum depth combination that meets the leakage control requirements.

[0063] S5, Thickness Optimization Based on the determined depth, the goal of this step is to determine the minimum curtain thickness required for each zone to meet the permeability stability requirements.

[0064] 1. Calculation and Judgment: Using the three-dimensional seepage field model determined by depth optimization, the hydraulic gradient of each element or Gaussian point inside the curtain body and at the curtain-rock contact surface is extracted through finite element post-processing. The maximum value is taken as the maximum seepage gradient J in this area, and the allowable seepage gradient J is set. 允 J 允 The determination should be based on the impermeability of the curtain grouting material, the erosion resistance of the contact surface between the curtain and the bedrock, and a certain safety factor (usually 1.5-3.0).

[0065] 2. Two-way adjustment optimization: Starting from the current thickness of each partition, optimization is performed.

[0066] For any region i, if the calculated maximum seepage gradient J i >J 允 This indicates that the curtain thickness in this area is insufficient, posing a risk of seepage and damage, and the thickness of the curtain in this area should be increased.

[0067] If J i ≤J 允 This indicates that the current thickness may have some margin, and we can try reducing the thickness of the curtain in this area to save materials.

[0068] Thickness adjustments are made in preset step sizes Δt (e.g., 0.5 meters). After each thickness adjustment for a region, the three-dimensional seepage field calculation must be rerun to obtain the new J. i value.

[0069] 3. Iterative convergence: Repeat the above judgment and adjustment process. For regions that need thickening, increase the thickness until J... i ≤J 允 For areas where thinning is possible, gradually reduce the thickness until J... i Very close but still satisfies J i ≤J 允 The critical state is found for each partition. Finally, for each partition, a state satisfying J is found. i ≤J 允 The minimum thickness under this safety constraint. This is the optimal thickness for this partition.

[0070] Through steps S1 to S5 above, the entire process of optimizing the curtain grouting system—from macroscopic positioning of the curtain grouting line to zoning based on geological differences, and then to the progressive, coupled, and quantitative optimization of depth (controlling leakage) and thickness (controlling seepage gradient)—is completed. The final output is the optimized centerline position, depth value, and thickness value for each design area, thereby guiding refined and differentiated curtain grouting construction.

[0071] Obviously, the above description is only a part of the embodiments of the present invention, and not all of the embodiments. The above embodiments are not intended to limit the present invention, and various modifications and variations can be made to the present invention by those skilled in the art. Any combination, modification, equivalent substitution, improvement, and all other embodiments that can be made by those skilled in the art within the spirit and principles of the present invention should be within the protection scope of the present invention.

Claims

1. A method for optimizing the zonal design of anti-seepage curtains for dams with complex and unfavorable geological structures, characterized by: Includes the following steps: S1. Route Determination: Obtain the groundwater critical line and the relative aquitard critical line in the dam site area. Establish a polar coordinate system. S2. Optimization of minimum distance seepage prevention line based on weighted equivalent seepage path: Construct a three-dimensional engineering geological model covering the seepage prevention area of ​​the dam, and divide the three-dimensional engineering geological model into several geological grid units; calibrate the comprehensive weighting coefficient of each geological grid unit based on the geological risk and construction cost of each geological grid unit; generate several alternative curtain lines within the spatial range that meets the preset seepage prevention baseline requirements. Along the main control seepage path of each candidate curtain line, the product of the geometric length of each geological grid unit traversed and its corresponding comprehensive weighting coefficient is accumulated to obtain the weighted equivalent seepage path length corresponding to each candidate curtain line. Search for the weighted equivalent seepage path length among the candidate curtain lines. The smallest curtain line is selected as the initial optimal anti-seepage curtain line, thereby determining the zoned lines and extension lengths of the anti-seepage curtain. S3. Curtain Zoning: Based on the distribution of strata permeability and unfavorable geological structures in the dam site area, the seepage prevention curtain is divided into n design zones. S4. Depth Optimization: Establish a three-dimensional seepage field finite element model of the dam, including the seepage barrier line and zoning information, set an initial depth for each design area, and calculate the total seepage volume Q; if Q is greater than the preset allowable seepage volume Q... 限 If so, increase the depth of one or more design zones that contribute the most to the total leakage, and recalculate the leakage until Q ≤ Q. 限 If the depth adjustment requires cutting off the fault or fracture zone, the adjusted depth must meet the following requirements: l i ≥max( ql i , pl i ),in l i For the first i The depth of each design area ql i For the first The distance from the top elevation of the seepage-proof curtain in each design area to the relative water-proof layer of the foundation. pl i For the first The depth of the curtain when the unfavorable geological structure of the area is completely cut off in the design area. S5. Thickness Optimization: Based on the depth-optimized three-dimensional seepage field finite element model, calculate the maximum seepage gradient for each design area. J ; like J Greater than the preset allowable permeability gradient J 允 If so, increase the thickness of the design area; J≤J 允 Then reduce the thickness of the design area and recalculate the permeability gradient until a satisfactory result is found. J≤J 允 And the optimal solution with the minimum thickness.

2. The method according to claim 1, characterized in that, In step S1, the groundwater critical line is determined by long-term observation well data or hydrogeological survey; the relative aquitard critical line is determined by a combination of geological borehole data and geophysical exploration data.

3. The method according to claim 1, characterized in that, In step S1, the steps for establishing the polar coordinate system include: S101. Geological Zoning and Target Identification: Analyze the geological survey data of the entire dam section to identify the unfavorable geological structures, spatial distribution, and main seepage path direction of the following river-guided faults, muddy weak interlayers, karst conduits in soluble rock areas, dense dissolution fissure zones, deep unloading fissure zones on the dam abutments, and strongly weathered zones. Divide the entire dam section into several independent geological zones. S102. Polar Point Determination: Based on the unfavorable geological structure types within each independent geological zone, and using the seepage control pole as the principle, the polar coordinate poles of each independent geological zone are determined differentially. For conventional uniform permeable strata zoning, the pole point is selected at the intersection of the dam abutment mountain and the relative impermeable layer at the corresponding elevation, and is the minimum control boundary point that meets the design requirements for seepage flow around the dam. For river-guided faults or muddy soft interlayer zones, the pole point is selected at the intersection of the fault or muddy soft interlayer with the dam axis and the relative impermeable layer. For karst conduits or dense dissolution fissure systems in soluble rock areas, the extreme points are selected at the water-impermeable boundary of the reservoir-side inlet and the water-impermeable boundary of the downstream outlet of the karst conduit system, or at the intersection of the concentrated development center of the dense dissolution fissure zone and the relative water-impermeable layer. For the deep unloading fracture zone or strongly weathered zone of the dam abutment, multiple levels of poles are set up at different elevations along the vertical direction. Each level of pole is selected at the intersection of the bottom boundary of the unloading fracture zone or strongly weathered zone and the relative impermeable layer at the corresponding elevation. S103, Polar coordinate parameter mapping: Using the poles established in each zone as the radiation control points of the seepage prevention curtain line, the polar angle corresponds to the direction of the seepage prevention curtain line, and the polar diameter corresponds to the extension length or depth of the seepage prevention curtain line, a differentiated polar coordinate system for each independent geological zone is established. S104. Curtain Line Splicing and Closure: Under the polar coordinate system of each independent geological zone, the corresponding seepage prevention curtain line is designed independently, and the seepage prevention curtain lines of each zone are spatially spliced. Each pole is located within the relative water-impermeable layer, so that the spliced ​​seepage prevention curtain line and the relative water-impermeable layer together form a continuous and closed seepage prevention and closure system.

4. The method according to claim 1, characterized in that, The specific implementation steps of step S2 include: S201. Refined 3D Mesh Modeling: Based on borehole, adit, and 3D geophysical data of the dam site area, a 3D engineering geological model is constructed to delineate the spatial boundaries of unfavorable geological structures; based on the design reference seepage field, the 3D engineering geological model is divided into cubic mesh units with side lengths of 0.5m to 2m, which serve as the geological mesh units. S202, Dual-control weighted parameter calibration: Calculate the geological risk coefficient for each of the geological grid units. and construction cost coefficient The geological risk coefficient is mentioned above. The construction cost coefficient was obtained by weighted calculation using the analytic hierarchy process (AHP) based on the formation permeability factor, the type and scale factor of unfavorable geological structures, and the risk level factor of seepage failure; It is obtained by weighted calculation of factors such as formation groutability and construction difficulty, curtain hole depth and construction conditions, and special process requirements. S203, Dynamic Weighting and Normalization: Introducing Risk Weight Coefficient and cost weighting coefficient And satisfy Dynamic adjustment based on the level of hydraulic structures, dam height, and geological complexity. and The value of the geological risk coefficient is determined, and the geological risk coefficient is determined. and construction cost coefficient Perform normalization processing; S204, Weighted Equivalent Seepage Path Calculation: Using the formula Calculate the weighted equivalent seepage path length for each candidate curtain line. ,in The first in the seepage path The geometric length of each geological grid cell and The first Geological risk coefficient and construction cost coefficient corresponding to each geological grid unit; S205. Numerical Simulation Verification and Iteration: Perform a three-dimensional seepage field numerical simulation on the initially selected optimal seepage barrier line to verify whether the seepage flow rate of the dam foundation, the uplift pressure of the dam body, the seepage gradient of key strata, and the seepage flow rate around the dam meet the design specifications; if not, increase the risk weight coefficient of the corresponding zone. Then return to step S204 to recalculate iteratively until all safety indicators meet the standards; S206. Integrated Verification of the Entire Dam Section: The curtain lines in each geological zone, verified by numerical simulation and meeting safety standards, are spatially spliced ​​and integrated to form a continuous seepage prevention curtain running through the entire dam section. The integrated continuous seepage prevention curtain is then verified. The verification checks whether the overall dam foundation seepage flow, overall dam body uplift pressure, seepage gradient of key strata throughout the site, and overall seepage flow around the dam section fully meet the seepage prevention design requirements and specifications, while also considering the construction cost coefficient. The total amount of work for the entire project was reviewed, and the final verification of the continuous anti-seepage curtain for the entire dam section was completed.

5. The method according to claim 1, characterized in that, In step S3, the principles of curtain partitioning include: within the same design area, the variation in the elevation of the top plate of the waterproof layer is within a small range allowed by the project, and unfavorable geological structures are continuously distributed in space.

6. The method according to claim 1, characterized in that, In step S4, the iterative formula for depth optimization is: ,in For the first The depth of the design region after the xth optimization. For the first The depth of the design region after the (x-1)th optimization. This is an increment for adjusting the depth based on the thickness of the geological unit and the calculation accuracy.

7. The method according to claim 1, characterized in that, In step S5, the logic for the bidirectional thickness adjustment is as follows: using the current thickness t as a reference, the thickness is increased or decreased by a preset step size Δt. After each adjustment, the three-dimensional seepage field is recalculated, and the maximum seepage gradient J and J' are determined. 允 The relationship continues until a relationship satisfying J≤J is found. 允 The critical minimum thickness.

8. The method according to claim 1, characterized in that, In steps S4 and S5, the boundary conditions of the finite element model of the three-dimensional seepage field of the dam are set as follows: the upstream boundary is set as a known head boundary, the downstream boundary is set as a known head or a free overflow boundary, and the bottom and side boundaries of the model are set as water-blocking boundaries or known head gradient boundaries.

9. The method according to claim 1, characterized in that, In step S4, the allowable leakage amount Q 限 The determination is based on a comprehensive analysis of reservoir function, downstream ecological water demand, and economic factors.

10. The method according to claim 1, characterized in that, In step S5, the permeability gradient J 允 The safety factor is determined based on the impermeability of the curtain material, the erosion resistance of the contact surface, and the safety factor.

Images