Underground cavern axis generation determination method based on multi-target space optimization model

Abstract

The invention belongs to the technical field of underground cavern axis generation, and provides an underground cavern axis generation determination method based on a multi-target space optimization model, and the method mainly comprises the steps: firstly, obtaining a main structural plane trend, a rock stratum trend and a maximum horizontal principal stress direction of an engineering region, and obtaining the engineering geological condition characteristics of the engineering region; secondly, establishing a multi-target space optimization model taking structural plane stability, stress state optimization and hydraulic performance guarantee as space optimization targets by taking the axis direction as an optimization variable; then, weights are distributed to each space optimization target based on engineering geological condition features; and finally, constructing a comprehensive scoring function, solving the axis direction when the comprehensive score is the highest by using the comprehensive scoring function, and taking the axis direction as the optimal axis direction. According to the method, the optimal axis direction suitable for the corresponding geological engineering condition characteristics can be quickly found under the complex geological conditions.

Description

Technical Field

[0001] This invention relates to the field of underground cavern axis generation technology, and in particular to a method for determining the generation of underground cavern axes based on a multi-objective spatial optimization model. Background Technology

[0002] Numerous engineering practices have pointed out that the design of underground powerhouse axes often faces a dilemma of "choosing one thing at the expense of another." For example, an axis chosen to avoid a major fault may happen to be perpendicular to the direction of high ground stress, leading to severe stress concentration problems; or a straight axis chosen to pursue the best hydraulic conditions may be parallel to the main fracture group, causing serious instability of the sidewall blocks. Existing codes and rules of thumb lack a unified and quantifiable method for weighing these key factors.

[0003] Meanwhile, the design of underground cavern axes requires comprehensive consideration of multiple factors, including geological structures (faults, fissures, rock strata), geostress fields, and hydraulic conditions. These factors have complex spatial coupling relationships. Existing design methods often consider these factors separately or empirically, lacking a clear and quantifiable set of spatial relationship criteria to guide the final determination of the axis direction. This makes it difficult to quickly and scientifically find the optimal solution under complex geological conditions, potentially leading to suboptimal axis designs and posing hidden dangers to the stability of the surrounding rock and operational safety. Summary of the Invention

[0004] The purpose of this invention is to provide a method for generating and determining the axis of underground caverns based on a multi-objective spatial optimization model, which can quickly find the optimal axis direction suitable for the corresponding geological and engineering conditions under complex geological conditions.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: A method for generating and determining the axis of underground caverns based on a multi-objective spatial optimization model includes the following steps: Obtain the orientation of the main structural planes, the orientation of the rock strata, and the direction of the maximum horizontal principal stress in the engineering area, and obtain the engineering geological conditions of the engineering area; A multi-objective spatial optimization model is established with the axial direction as the optimization variable, and the spatial optimization objectives are structural surface stability, optimized stress state, and guaranteed hydraulic performance. Weights are assigned to each spatial optimization objective based on the characteristics of engineering geological conditions. Construct a comprehensive scoring function, and use the comprehensive scoring function to find the axis direction that maximizes the comprehensive score, and use it as the optimal axis direction.

[0006] In some embodiments, obtaining the orientation of the main structural planes, the orientation of the rock strata, and the direction of the maximum horizontal principal stress in the engineering area, and obtaining the engineering geological conditions of the engineering area, refers to: Geological surveys were conducted to obtain the orientation of the main structural planes and the orientation of the rock strata in the engineering area, and geostress tests were conducted to obtain the direction of the maximum horizontal principal stress. The engineering geological conditions of the project area are determined by geological survey and geostress testing. These engineering geological conditions include high geostress areas, areas with developed structural planes, areas with high hydraulic requirements, and areas with balanced geological conditions.

[0007] In some embodiments, the spatial optimization objective for structural surface stability refers to maximizing the angle between the axial direction and the orientation of the main structural surface. The spatial optimization objective for optimizing the stress state is to minimize the angle between the axial direction and the direction of the maximum principal stress. The aforementioned spatial optimization objective for ensuring hydraulic performance refers to aligning the axial direction as closely as possible with the ideal upstream and downstream waterway connection direction.

[0008] In some embodiments, assigning weights to each spatial optimization objective based on engineering geological condition characteristics includes the following steps: Set equal initial weights for each objective function, so that the initial weights correspond to the geological condition equilibrium zone, and the sum of all initial weights is 1; Obtain real-time engineering geological conditions and determine the corresponding zone. If it belongs to a zone with balanced geological conditions, the initial weight will not be adjusted. If it belongs to a zone with high ground stress, a zone with developed structural surfaces, or a zone with high hydraulic requirements, the initial weight corresponding to it will be increased, and the initial weight corresponding to other zones will be decreased.

[0009] In some embodiments, the different spatial optimization objectives are represented by corresponding objective functions; The phrase "assigning weights to each spatial optimization objective based on engineering geological conditions" means assigning weights to the objective function corresponding to each spatial optimization objective based on the engineering geological conditions.

[0010] In some embodiments, the constructed comprehensive scoring function is a weighted sum of all objective functions.

[0011] In some embodiments, the ideal value of the angle between the axial direction and the orientation of the main structural surface is 90°. That is, the objective function corresponding to the spatial optimization objective of structural surface stability has the highest score (maximum value 1) when the angle between the axial direction and the orientation of the main structural surface is 90°, and the lowest score (minimum value 0) when the angle between the axial direction and the orientation of the main structural surface is 0° or 180°. The objective function monotonically increases between 0° and 90° and monotonically decreases between 90° and 180°.

[0012] In some embodiments, the ideal value of the angle between the axial direction and the direction of maximum principal stress is 0°. That is, the objective function corresponding to the spatial optimization objective of optimizing the stress state has the highest score (maximum value 1) when the angle between the axial direction and the direction of maximum principal stress is 0°, and the lowest score (minimum value 0) when the angle between the axial direction and the direction of maximum principal stress is 90°.

[0013] In some embodiments, the axial direction is as consistent as possible with the ideal upstream and downstream waterway connection direction. In this case, the objective function corresponding to the spatial optimization objective of ensuring hydraulic performance is a Gaussian function or a linear function.

[0014] In some embodiments, the step of using a comprehensive scoring function to find the axis direction that maximizes the comprehensive score and using it as the optimal axis direction includes the following steps: Discretize the possible axial directions from 0° to 180° with a fixed step size to generate a set of candidate directions; For each candidate direction in the candidate direction set, calculate its corresponding comprehensive score; Compare all the comprehensive score values ​​and find the candidate direction corresponding to the maximum value. This direction is the optimal axis direction.

[0015] The beneficial effects of this invention are as follows: First, this invention transforms the original experience-based axis determination process into a multi-objective optimization problem, obtaining the optimal solution through quantitative calculation, making the decision-making process clear and objective. Second, by simultaneously optimizing the spatial relationship between the axis, geological structure, and geostress, this invention can significantly improve the stress state and self-stabilizing ability of the surrounding rock from the source, reducing safety risks during construction and operation. Simultaneously, this invention provides designers with a clear design process and decision-making basis, reducing the blindness of repeated trial calculations and comparisons between different schemes, and enabling faster convergence to the optimal axis scheme. Furthermore, this invention does not rely on complex 3D modeling or specialized software; it can be implemented using geological data and simple mathematical calculations, making it easy to promote and apply in engineering design units. Finally, this invention introduces a weight allocation mechanism based on geological condition characteristics, thus solving the problem of varying importance of factors under different engineering backgrounds, making the method more flexible and resulting in strong applicability. Attached Figure Description

[0016] Figure 1 This is a flowchart of a method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model, according to Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Example 1

[0019] This embodiment provides a method for generating and determining the axis of underground caverns based on a multi-objective spatial optimization model. See the flowchart below. Figure 1 The method may include the following steps: S1. Obtain the orientation of the main structural planes, the orientation of the rock strata, and the direction of the maximum horizontal principal stress in the engineering area, and obtain the engineering geological conditions of the engineering area; S2. Using the axial direction as the optimization variable, establish a multi-objective spatial optimization model with structural surface stability, optimized stress state, and guaranteed hydraulic performance as spatial optimization objectives. S3. Assign weights to each spatial optimization objective based on engineering geological conditions; S4. Construct a comprehensive scoring function and use the comprehensive scoring function to find the axis direction that maximizes the comprehensive score, and use it as the optimal axis direction.

[0020] In practical applications, the orientation (denoted as α_s) and stratum strike (denoted as α_b) of the main structural planes (such as dominant fracture groups and faults) in the plant area can be obtained through geological exploration (surveying, drilling, geophysical exploration), and the direction of the maximum horizontal principal stress (denoted as α_σ) can be obtained through in-situ stress testing (such as hydraulic fracturing). Therefore, in this embodiment, obtaining the orientation of the main structural planes, stratum strike, and direction of the maximum horizontal principal stress in the engineering area, and obtaining the engineering geological conditions of the engineering area, means: obtaining the orientation of the main structural planes and stratum strike in the engineering area through geological exploration, and obtaining the direction of the maximum horizontal principal stress through in-situ stress testing.

[0021] In the process of obtaining the above parameters in this embodiment, the key characteristics such as the "degree of development of structural surfaces" and "level of ground stress" of the engineering area have been clearly obtained through comprehensive engineering geological exploration (surveying, drilling, geophysical exploration) and ground stress testing. Therefore, the engineering geological conditions can be determined. Thus, in this embodiment, the engineering geological conditions of the engineering area can be determined through geological exploration and ground stress testing. The engineering geological conditions include high ground stress areas, structural surface development areas, areas with high hydraulic requirements, and areas with balanced geological conditions.

[0022] In this embodiment, the axial direction of the plant (denoted as β) is used as the optimization variable, with the goal of achieving three optimal spatial relationships: spatial optimization for structural surface stability, spatial optimization for stress state optimization, and spatial optimization for ensuring hydraulic performance. Specifically, the spatial optimization for structural surface stability aims to maximize the angle (|β-α_s|) between the axial direction and the orientation of the main structural surface (ideally 90°) to reduce the cutting of the structural surface by the sidewalls and control the size and number of unstable blocks. The spatial optimization for stress state optimization aims to minimize the angle (|β-α_σ|) between the axial direction and the direction of the maximum principal stress (ideally 0°) to make the stress distribution around the tunnel more uniform and reduce stress concentration. The spatial optimization for ensuring hydraulic performance aims to prioritize a straight-line layout while satisfying geological stability requirements, ensuring that the axial direction is as consistent as possible with the ideal upstream and downstream waterway connection direction.

[0023] Next, weights can be assigned to each spatial optimization objective. In this embodiment, assigning weights to each spatial optimization objective based on engineering geological conditions can include the following steps: Set equal initial weights for each objective function, so that the initial weights correspond to the geological condition equilibrium zone, and the sum of all initial weights is 1; Obtain real-time engineering geological conditions and determine the corresponding zone. If it belongs to a zone with balanced geological conditions, the initial weight will not be adjusted. If it belongs to a zone with high ground stress, a zone with developed structural surfaces, or a zone with high hydraulic requirements, the initial weight corresponding to it will be increased, and the initial weight corresponding to other zones will be decreased.

[0024] In practical applications, the allocation of weights in this embodiment can be explained in detail with the following specific examples: Step 1: Set initial weights. In the "general case" where no specific geological trend is found, assign equal initial weights to the three objective functions, i.e.: W_stable_initial=W_stress_initial=W_hydraulic_initial=1 / 3≈0.333; This initial weight represents the equal importance given to structural stability, stress state, and hydraulic performance under the absence of special geological conditions.

[0025] Step 2: Dynamically adjust based on known geological conditions. This involves making targeted adjustments to the initial weights based on the geological characteristics obtained in Step 1, where: For high ground stress areas: If ground stress tests indicate a high ground stress area, increase W_stress and correspondingly decrease other weights. For example: W_stress=0.6, W_stable=0.2, W_hydraulic=0.2; For areas with well-developed structural planes: if exploration reveals highly developed faults and fractures, increase W_stable, for example: W_stable=0.6, W_stress=0.2, W_hydraulic=0.2; For areas with high hydraulic requirements: If the project is extremely sensitive to hydraulic losses (such as pumped storage power stations), W_hydraulic can be increased, for example: W_hydraulic=0.6, W_stress=0.2, W_stable=0.2.

[0026] It should be noted that the different spatial optimization objectives in this embodiment can be represented by corresponding objective functions. Therefore, in this case, assigning weights to each spatial optimization objective based on engineering geological conditions means assigning weights to the objective function corresponding to each spatial optimization objective based on engineering geological conditions.

[0027] In this embodiment, the constructed comprehensive scoring function is a weighted sum of all objective functions.

[0028] Therefore, the three objective functions in this embodiment will be described in detail with the following specific examples.

[0029] The ideal value for the angle between the axis direction and the orientation of the main structural plane is 90°. That is, the objective function corresponding to the spatial optimization objective of structural plane stability scores the highest when the angle between the axis direction and the orientation of the main structural plane is 90°, with a maximum value of 1. The lowest score is 0 when the angle between the axis direction and the orientation of the main structural plane is 0° or 180°. The objective function monotonically increases between 0° and 90° and monotonically decreases between 90° and 180°.

[0030] The ideal value of the angle between the axial direction and the direction of the maximum principal stress is 0°. That is, the objective function corresponding to the spatial optimization objective of optimizing the stress state scores the highest when the angle between the axial direction and the direction of the maximum principal stress is 0°, with a maximum value of 1. The score is the lowest when the angle between the axial direction and the direction of the maximum principal stress is 90°, with a minimum value of 0.

[0031] The axial direction is as consistent as possible with the ideal upstream and downstream waterway connection direction. In this case, the objective function corresponding to the spatial optimization objective of ensuring hydraulic performance is a Gaussian function or a linear function.

[0032] Specifically, for the three objective functions: (1) The objective function for structural stability is expressed as F_stable(β), and the objective is to maximize the angle θ_s=|β-α_s| between the axial direction β and the direction α_s of the main structural surface. The ideal value is θ_s=90°.

[0033] When designing the objective function, the score should be highest (1) when θ_s = 90° and lowest (0) when θ_s = 0° or 180°, i.e., F_stable(β) = sin²(|β-α_s|). The characteristics of this objective function are: When θ_s=90°, sin(90°)=1, F_stable(β)=1 (optimal); When θ_s = 0° or 180°, sin(0°) = 0, F_stable(β) = 0 (worst case); The objective function is monotonically increasing between 0° and 90° and monotonically decreasing between 90° and 180°, perfectly meeting the engineering requirement of "optimal perpendicularity to the structural plane".

[0034] (2) The objective function of stress state is expressed as: F_stress(β), the objective is to minimize the angle θ_σ=|β-α_σ| between the axial direction β and the direction of the maximum principal stress α_σ, and the ideal value is: θ_σ=0°.

[0035] When designing the objective function, the score should be highest (1) when θ_σ = 0° and lowest (0) when θ_σ = 90°. An ideal function is a cosine function: F_stress(β) = |cos(|β-α_σ|)|. The characteristics of the objective function are: When θ_σ=0°, cos(0°)=1, F_stress(β)=1 (optimal); When θ_σ=90°, cos(90°)=0, F_stress(β)=0 (worst case); Taking the absolute value ensures that the scores are the same in the 0° and 180° directions (because the direction of geostress is axial and has no positive or negative sign). This objective function quantifies the parallelism between the axis and the principal stress direction.

[0036] (3) The objective function of hydraulic performance is expressed as: F_hydraulic(β), the objective is: the axial direction β should be as consistent as possible with the ideal upstream and downstream waterway connection direction β_h, the ideal value is: β=β_h.

[0037] When designing the objective function: it is a single-objective optimization, and its objective function (scoring function) can be designed as a Gaussian function or a linear function, with the highest score at the ideal value and the lower the score as it deviates further from the ideal value.

[0038] For example, scheme A (Gaussian function, strict matching): F_hydraulic(β)= exp(-k*(β-β_h)²) Here, k is a decay coefficient that controls the strictness of the matching. The larger the value of k, the lower the tolerance for deviation. When β=β_h, the score is 1; the larger the deviation, the score approaches 0.

[0039] For example, Option B (linear function, with higher tolerance): F_hydraulic(β)=max(0,1-|β-β_h| / T) Here, T is a tolerance threshold (e.g., T = 30°). When the deviation angle is less than T, the score decreases linearly from 1 to 0; if it exceeds T, the score is 0.

[0040] Finally, the optimal axis direction can be obtained. In this embodiment, the step of using the comprehensive scoring function to find the axis direction that maximizes the comprehensive score and using it as the optimal axis direction can include the following steps: Discretize the possible axial directions from 0° to 180° with a fixed step size to generate a set of candidate directions; For each candidate direction in the candidate direction set, calculate its corresponding comprehensive score; Compare all the comprehensive score values ​​and find the candidate direction corresponding to the maximum value. This direction is the optimal axis direction.

[0041] Example 2

[0042] Based on Example 1, this example assumes that a certain project has already obtained the following basic data: The orientation of the main structural plane is α_s = 30°; The direction of the maximum principal stress is α_σ = 80°; Ideal hydraulic connection direction β_h = 60°; Based on the geological conditions, the weights are determined as follows: W_stable=0.5, W_stress=0.3, W_hydraulic=0.2; The hydraulic performance function is selected as a Gaussian function, with an attenuation coefficient of k=0.001.

[0043] Therefore, the specific implementation process can include the following three steps: I. Construct the comprehensive scoring function F_total(β): The comprehensive scoring function is a weighted sum of the three objective functions: F_total(β)=W_stable*F_stable(β)+W_stress*F_stress(β)+W_hydraulic*F_hydraulic(β); After substituting the specific function and weights, it becomes: F_total(β)=0.5*[sin²(|β-30°|)]+0.3*[|cos(|β-80°|)|]+ 0.2 * [exp(-0.001*(β-60°)²)].

[0044] 2. Solving for the optimal axis direction β_optimal: The goal is to find a β value (usually in the range of 0° to 180°) that maximizes the value of F_total(β).

[0045] The specific solution process (taking the enumeration method as an example): Since the objective function is continuous and nonlinear, the numerical enumeration method can be used for efficient solution. This method is easy to program and intuitive to understand. Therefore, the specific steps are as follows: Step 1: Discretize the search space. Discretize the possible axial directions β from 0° to 180° with a fixed step size (e.g., 1°) to generate a set of candidate directions: [0°, 1°, 2°, ..., 180°].

[0046] Step 2: Iteratively calculate the score. For each candidate direction β_i in the set, calculate its corresponding comprehensive score F_total(β_i).

[0047] Step 3: Compare and determine the optimal solution. Compare all values ​​of F_total(β_i) and find the candidate direction β_i corresponding to the maximum value. This direction is the optimal axis direction β_optimal.

[0048] Example of calculation results (simulation): When calculating to β=65°: F_stable(65°)=sin²(|65-30|)=sin²(35°)≈0.329; F_stress(65°)=|cos(|65-80|)|=|cos(15°)|≈0.966; F_hydraulic(65°)=exp(-0.001*(65-60)²)=exp(-0.025)≈0.975; F_total(65°)=0.5*0.329+0.3*0.966+0.2*0.975≈0.1645+0.2898+0.195=0.6493.

[0049] By iterating through all angles, it may be found that when β=68°, F_total(68°)≈0.6521 is the maximum value.

[0050] Therefore, under the specific conditions of this example, the optimal axis direction β_optimal is 68°.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model, characterized in that, Includes the following steps: Obtain the orientation of the main structural planes, the orientation of the rock strata, and the direction of the maximum horizontal principal stress in the engineering area, and obtain the engineering geological conditions of the engineering area; A multi-objective spatial optimization model is established with the axial direction as the optimization variable, and the spatial optimization objectives are structural surface stability, optimized stress state, and guaranteed hydraulic performance. Weights are assigned to each spatial optimization objective based on the characteristics of engineering geological conditions. Construct a comprehensive scoring function, and use the comprehensive scoring function to find the axis direction that maximizes the comprehensive score, and use it as the optimal axis direction.

2. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 1, characterized in that, Obtaining the strike of the main structural planes, the strike of the rock strata, and the direction of the maximum horizontal principal stress in the engineering area, as well as the engineering geological characteristics of the engineering area, refers to: Geological surveys were conducted to obtain the orientation of the main structural planes and the orientation of the rock strata in the engineering area, and geostress tests were conducted to obtain the direction of the maximum horizontal principal stress. The engineering geological conditions of the project area are determined by geological survey and geostress testing. These engineering geological conditions include high geostress areas, areas with developed structural planes, areas with high hydraulic requirements, and areas with balanced geological conditions.

3. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 2, characterized in that, The spatial optimization objective for structural surface stability refers to maximizing the angle between the axial direction and the orientation of the main structural surface. The spatial optimization objective for optimizing the stress state is to minimize the angle between the axial direction and the direction of the maximum principal stress. The aforementioned spatial optimization objective for ensuring hydraulic performance refers to aligning the axial direction as closely as possible with the ideal upstream and downstream waterway connection direction.

4. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 3, characterized in that, The process of assigning weights to each spatial optimization objective based on engineering geological conditions includes the following steps: Set equal initial weights for each objective function, so that the initial weights correspond to the geological condition equilibrium zone, and the sum of all initial weights is 1; Obtain real-time engineering geological conditions and determine the corresponding zone. If it belongs to a zone with balanced geological conditions, the initial weight will not be adjusted. If it belongs to a zone with high ground stress, a zone with developed structural surfaces, or a zone with high hydraulic requirements, the initial weight corresponding to it will be increased, and the initial weight corresponding to other zones will be decreased.

5. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 4, characterized in that, The different spatial optimization objectives are represented by corresponding objective functions; The phrase "assigning weights to each spatial optimization objective based on engineering geological conditions" means assigning weights to the objective function corresponding to each spatial optimization objective based on the engineering geological conditions.

6. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 5, characterized in that, The constructed comprehensive scoring function is a weighted sum of all objective functions.

7. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 6, characterized in that, The ideal value of the angle between the axis direction and the orientation of the main structural surface is 90°. That is, the objective function corresponding to the spatial optimization objective of structural surface stability has the highest score (maximum value 1) when the angle between the axis direction and the orientation of the main structural surface is 90°, and the lowest score (minimum value 0) when the angle between the axis direction and the orientation of the main structural surface is 0° or 180°. The objective function monotonically increases between 0° and 90° and monotonically decreases between 90° and 180°.

8. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 6, characterized in that, The ideal value of the angle between the axial direction and the direction of the maximum principal stress is 0°. That is, the objective function corresponding to the spatial optimization objective of optimizing the stress state has the highest score when the angle between the axial direction and the direction of the maximum principal stress is 0°, with a maximum value of 1. The lowest score is when the angle between the axial direction and the direction of the maximum principal stress is 90°, with a minimum value of 0.

9. The method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to claim 6, characterized in that, The axial direction is as consistent as possible with the ideal upstream and downstream waterway connection direction. In this case, the objective function corresponding to the spatial optimization objective of ensuring hydraulic performance is a Gaussian function or a linear function.

10. A method for generating and determining the axis of an underground cavern based on a multi-objective spatial optimization model according to any one of claims 6-9, characterized in that, The process of using a comprehensive scoring function to find the axis direction that maximizes the comprehensive score, and then using it as the optimal axis direction, includes the following steps: Discretize the possible axial directions from 0° to 180° with a fixed step size to generate a set of candidate directions; For each candidate direction in the candidate direction set, calculate its corresponding comprehensive score; Compare all the comprehensive score values ​​and find the candidate direction corresponding to the maximum value. This direction is the optimal axis direction.

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