Digital simulation evaluation method for overall settlement and horizontal offset of transmission tower-line system in goaf

Abstract

The application provides a kind of goaf transmission tower line system overall settlement and horizontal offset digital simulation evaluation method, relate to transmission line engineering structure safety analysis technical field.This method establishes three towers four line rod beam mixed coupling model and completes the shape finding of ground wire;Multiple gradient displacement loading is applied to the model to simulate continuous gradual deformation of goaf;Extract data to build high axial force skeleton reflecting main load-carrying channel;Combined with stress ratio, overall lateral stiffness, settlement-displacement nonlinear growth rate and stiffness degradation coefficient for multidimensional calculation.Through the coordinated monitoring of local stress overrun, abnormal force flow redistribution, stiffness degradation and displacement mutation threshold, the overall instability early warning is output.The application breaks through the limitation of single stress evaluation which is easy to cause missed alarm, realizes the precise mathematical representation of force flow evolution tracking and structure deterioration, greatly improves the foresight and quantization level of complex multi-tower coupling system anti-collapse early warning.

Description

Technical Field

[0001] This invention relates to the field of structural safety analysis technology for power transmission line engineering, and more specifically, to a digital simulation evaluation method for the overall settlement and horizontal displacement of power transmission tower systems in mining subsidence areas. Background Technology

[0002] As the core backbone of large-capacity power transmission, ultra-high voltage and extra-high voltage transmission lines are crucial to social production and daily life, and their safe and stable operation is of paramount importance. Transmission tower systems typically feature high tower height, large spans, and high flexibility, along with multiple degrees of freedom coupling. This makes these large spatial truss structures extremely sensitive to external environmental loads such as earthquakes, wind loads, icing, and foundation deformation. In actual engineering route selection and construction, due to limitations in terrain and geological conditions, many transmission lines inevitably need to traverse goaf areas left behind by underground mineral resource extraction. Goaf areas refer to cavities formed within underground rock strata due to mining. Over time, with the release of stress in the overlying rock strata, continuous and large-scale overall settlement and horizontal movement of the ground surface occur. This non-uniform, continuous, large-scale deformation of the foundation directly acts on the transmission tower foundation, forcing the tower legs to undergo forced displacement, which in turn causes severe additional internal forces within the tower and leads to a redistribution of these forces. When the foundation settlement or offset reaches a certain level, it can not only cause local tower components to yield and become unstable, but in severe cases it can even trigger a chain reaction, causing the entire transmission tower system to collapse and resulting in incalculable engineering losses.

[0003] Currently, research and safety assessment methods for the structural mechanical response of transmission towers in goaf areas still have many limitations, making it difficult to meet the safety early warning needs of complex projects. First, existing numerical simulations and assessments mostly focus on the settlement response of a single transmission tower or perform simplified static loading analyses. However, actual transmission tower systems are highly coupled structures consisting of multiple towers physically connected by conductors and ground wires. When ground settlement occurs at a certain location, there is a significant mechanical interaction between the side towers and the middle towers, and the displacement transmission and internal force distribution patterns under settlement differ fundamentally for different tower type combinations (such as different arrangements of straight-line towers and tension towers). Single-tower models completely sever the nonlinear tensile effect of conductors and ground wires on the tower body and the coupling constraints between adjacent towers, leading to overly idealized boundary condition assumptions and severely distorted assessment results. Second, the settlement and displacement of the goaf surface is an extremely complex, continuous, and gradual process, with deformation potentially accumulating from zero to several meters. Traditional assessment methods often lack gradient loading simulation mechanisms for such continuous large deformations, making it difficult to recreate the dynamic evolution of the structural mechanical response as surface deformation intensifies.

[0004] More importantly, in terms of structural safety assessment logic, existing technologies generally rely on a single "global maximum stress ratio" as the sole criterion for determining the safety of a component. This traditional "point assessment" model suffers from a severe "stress averaging" masking effect when dealing with complex, large-scale, multi-span tower-line coupled structures. Due to the extremely high static indeterminate nature of the tower-line system, when a local foundation undergoes forced displacement, the maximum stress ratio often concentrates only on one or two extremely localized components. However, actual structural collapse is often not caused by the instantaneous failure of a single component, but rather by a chain reaction of collective deterioration triggered by the sequential buckling, stiffness degradation, and force redistribution of multiple members. The global maximum stress ratio cannot reflect this decrease in overall structural stability caused by the abnormality of the main force transmission path. In other words, even if the global maximum stress ratio has not yet reached the yield limit, the main load-bearing channels within the structure may have already experienced asymmetric shifts, severe interruptions, or abnormal load transfers to non-critical components, posing a significant risk of local instability clustering and torsional tilting. Traditional methods cannot extract and understand these deep-seated internal force flow topological evolutions from a massive number of structural members, which can easily lead to missed warnings of chain reaction failure risks and prevent true early warning of structural collapse.

[0005] Therefore, there is an urgent need to establish a digital simulation evaluation method that can accurately reflect the mechanical characteristics of tower-line coupling and simulate the boundary conditions of continuous displacement in the goaf. Furthermore, it is necessary to break through the limitations of traditional single-point stress evaluation and combine key mechanical indicators such as displacement field, axial force field and component stress ratio to quantitatively evaluate the anti-collapse capability of different tower system combinations from the perspective of force flow redistribution within the structure, so as to achieve more forward-looking and accurate engineering safety early warning. Summary of the Invention

[0006] The present invention aims to solve at least one of the aforementioned technical problems existing in the prior art.

[0007] Therefore, this invention provides a digital simulation evaluation method for the overall settlement and horizontal displacement of power transmission tower systems in goaf areas.

[0008] This invention provides a digital simulation evaluation method for the overall settlement and horizontal displacement of a power transmission tower system in a goaf, comprising: S1. Establish a hybrid coupled model of three towers and four lines, including intermediate towers and side towers. The main materials and major components of the transmission towers are simulated using beam elements, the secondary components are simulated using pole elements, and the conductors and ground wires are simulated using pole elements under tension only. Based on the catenary theory, the initial length of the conductors and ground wires is calculated iteratively to ensure that the geometry of the conductors and ground wires satisfies the convergence condition of elastic elongation and geometric length self-consistency under the action of self-weight and initial tension, thus completing the initial state form finding of the system. S2. Apply bottom consolidation and conductor end fixing constraints to the side towers in the three-tower four-line pole-beam hybrid coupling model, apply a preset range of vertical settlement displacement and / or horizontal displacement to each tower leg of the middle tower, and perform multi-gradient step-by-step loading to simulate the continuous gradual deformation of the surface of the goaf. S3. Extract the global displacement response data of the transmission tower system under various gradient displacement loading and the axial force data of all members of the tower; based on the axial force data, select a set of key members with a predetermined number of key members whose absolute axial force values ​​are among the highest, and extract or draw a high axial force skeleton and its visualization cloud map that reflects the internal main load-bearing channel based on the set of key members. S4. Extract the internal force data and section parameters of each member of the entire tower. Based on the calculation logic of the ultimate tensile strength bearing capacity of the tension member and the calculation logic of the ultimate stability bearing capacity of the compression member, calculate the stress ratio of each member of the entire tower under the current loading gradient. At the same time, combined with the extracted global displacement response data and settlement loading step size, calculate the overall lateral stiffness of the transmission tower system, the nonlinear growth rate of settlement-displacement, and the stiffness degradation coefficient of each member of the entire tower. S5. Compare the stress ratio of each member of the entire tower with a preset safety threshold to assess the component-level yield resistance or instability resistance; determine the continuity and symmetry of the high axial force frame based on the spatial distribution characteristics of the high axial force frame or the visualization cloud map; simultaneously monitor the degradation inflection point of the overall lateral stiffness, the abrupt change in the nonlinear growth rate of settlement-displacement, and the decrease in the stiffness degradation coefficient; when any one or more of the following conditions are met—stress ratio exceeding the limit, asymmetry or interruption of the high axial force frame, or the overall lateral stiffness, settlement-displacement nonlinear growth rate, and stiffness degradation coefficient reaching the preset instability threshold—an early warning of overall instability or collapse of the transmission tower system is output.

[0009] The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to the above-mentioned technical solution of the present invention may also have the following additional technical features: In the above technical solution, in S1, the establishment of a three-tower, four-line beam hybrid coupling model including the intermediate tower and the side towers includes: Based on the structural characteristics, the components of the power transmission tower are mechanically equivalently divided. The main materials and structural skeleton that mainly bear bending moment and axial load are assigned as spatial beam elements; the auxiliary structures that only bear axial tensile and compressive loads are assigned as spatial rod elements. By assigning mass and cross-sectional area to the conductor, the split conductors in the conductor are equivalently converted into a single conductor, and the insulator string is set as a rigid rod unit with a high elastic modulus. The model is subjected to mass correction processing, and the mass of the power transmission tower is matched and verified with the actual design weight by increasing the material density.

[0010] In the above technical solution, in S1, the step of iteratively calculating the initial length of the ground wire includes: Input the coordinates of the two hanging points of the conductor and the design horizontal tension; Using the catenary theory or the parabola approximation equation, the original geometric length of the conductor arc length under strain-free state is derived by integral calculation. Calculate the elastic elongation of the conductor under its own weight and initial tension, and determine whether the difference between the original geometric length and the elastic elongation meets the preset error convergence condition; if not, dynamically adjust the initial length parameter and re-enter the iteration until the convergence condition is met and the accurate initial length data is output.

[0011] In the above technical solution, step S2, the step-by-step loading with multiple gradients includes: The continuous and gradual deformation process of the foundation in the goaf is discretized into multiple loading steps; Within each loading step, a spatial displacement load boundary condition of a preset step length is forcibly applied to the bottom node of the intermediate tower, and the static equilibrium state of the tower line system under the displacement boundary is recalculated. The loading step distance is cyclically increased until the total accumulated displacement reaches the limit deformation range of the simulation design, so as to obtain the evolution history of the structural response during continuous settlement.

[0012] In the above technical solution, in S3, the selection of key member sets and the extraction of high axial force skeletons include: From the extracted axial force data of all tower members, for any loading gradient, calculate the absolute value of the axial force of all members and sort them in descending order; The preset number of top-ranked members are selected to form a set of key members, and the node coordinates and topological connections of each member in the set of key members are obtained. Through three-dimensional spatial mapping, the key members and their axial force values ​​are mapped into a high axial force skeleton spatial continuity topology network, which is used to characterize the main force transmission path of the structure under the current deformation state.

[0013] In the above technical solution, in S4, calculations are performed based on the ultimate tensile strength bearing capacity calculation logic and the ultimate stability bearing capacity calculation logic of the compression member, respectively, including: When the internal forces of the member are in an axially tensile state, the stress ratio calculation method includes:

[0014] in, The stress ratio of an axially tensioned member. This refers to the design or ultimate bearing capacity of an axially tensioned member. Let be the net cross-sectional area of ​​the component. This is the design value for the tensile strength of the steel. When the internal forces of the member are in a state of axial compression, the stress ratio calculation method includes:

[0015] in, The stress ratio of an axially compressed member. Let be the stability coefficient of the axially compressed member, and A be the gross cross-sectional area of ​​the member.

[0016] In the above technical solution, the stability coefficient of the axially compressed member is determined based on the slenderness ratio of the member; The method for calculating the slenderness ratio includes:

[0017] in, For the slenderness ratio, The calculated length of the component. Let be the radius of gyration of the cross section about the corresponding principal axis; The stability coefficient of the axially compressed component is negatively correlated with the slenderness ratio.

[0018] In the above technical solution, in S4, the method for calculating the overall lateral stiffness of the transmission tower system includes:

[0019] in, For the overall lateral stiffness of the transmission tower system; This is the equivalent horizontal resultant force acting at the suspension point of the conductor and ground wire at the top of the tower; This corresponds to the horizontal displacement of the tower top.

[0020] In the above technical solution, in S4, the calculation method for the nonlinear growth rate of settlement-displacement includes:

[0021] in, The nonlinear growth rate of settlement-displacement; This represents the maximum displacement of the tower body at the current settlement depth h. This represents the settlement loading step size, i.e., the amount of settlement change.

[0022] In the above technical solution, in S4, the method for calculating the stiffness degradation coefficient of each member of the entire tower includes:

[0023] in, Let be the stiffness degradation coefficient of member i; This is the initial elastic modulus of the steel. Let be the tangent modulus of member i under the current stress state.

[0024] In the above technical solution, in S5, the assessment logic for the overall instability or collapse early warning of the output transmission tower system includes: The global maximum stress ratio is extracted from the stress ratio of each member of the entire tower and monitored. If the stress ratio of any member is greater than 1.0, it is determined that local yielding or instability failure has occurred. Track the topological evolution of the high axial force skeleton. If the main load-bearing loop of the high axial force skeleton is not kept closed, or if the spatial distribution of the high axial force components is asymmetrically offset due to load concentration on a certain side or in a certain layer, it is determined that the force flow redistribution path is abnormal. When the curve of the overall lateral stiffness as a function of settlement depth shows a downward inflection point, it is determined to be the initial threshold for system stiffness instability. When the nonlinear growth rate of settlement-displacement is greater than or equal to 1.0, the structure is determined to have entered the nonlinear instability warning zone. The stiffness degradation coefficient of each member in the set of key members is extracted and the average value is calculated. When the average value is less than 0.85, it is determined that the structure has undergone significant stiffness degradation. A collapse precursor warning is triggered when any of the following occurs: local yielding or instability failure, abnormal force flow redistribution path, reaching the initial threshold of system stiffness instability, entering the nonlinear instability warning zone, or significant stiffness degradation of the structure.

[0025] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are: This invention overcomes the limitations of single stress assessment and constructs a multi-dimensional collaborative anti-collapse early warning mechanism from component to system. Traditional safety assessments rely excessively on the single component-level indicator of "whether the maximum stress ratio exceeds the limit." When dealing with large, highly statically indeterminate tower systems, this is prone to missing warnings of overall instability due to the "stress averaging" masking effect. This invention creatively proposes to extract and construct a "high axial force skeleton" that reflects the internal main load-bearing channels, visualizing and logically topologicalizing the invisible structural force flow redistribution path. Even when the global maximum stress ratio has not reached the yield limit, it can still identify the cluster effect of structural stiffness degradation and local instability in advance by capturing the asymmetric offset or interruption of the main load-bearing loop, effectively avoiding the risk of chain-reaction failure.

[0026] The newly introduced quantitative mechanical indicators enable precise mathematical characterization of the evolution process of structural stiffness degradation and displacement mutations. Based on stress ratio and high axial force skeletons, this invention further constructs three synergistic judgment indicators: by calculating the overall lateral stiffness, the inflection point of decline can be used to accurately locate the initial safety threshold of overall system stiffness instability; by introducing the nonlinear growth rate of settlement-displacement, it can keenly identify "mutant" dangerous displacement responses exceeding the foundation settlement rate, and lock in the nonlinear instability warning zone in advance; by extracting the stiffness degradation coefficient of key members, the degree of deterioration of plasticity or buckling within the main load-bearing channel is precisely quantified. These multidimensional quantitative indicators transform the traditional experience-based fuzzy degradation assessment into a high-precision system-level judgment threshold, significantly improving the foresight and absolute accuracy of disaster early warning.

[0027] A high-fidelity hybrid coupling model of three towers and four conductors was established, eliminating evaluation distortions caused by idealized boundary conditions from the bottom-level data source. This invention abandons the traditional simplified analysis model for single towers and systematically considers the multi-degree-of-freedom nonlinear coupling characteristics of complex transmission tower and conductor systems. By strictly distinguishing between the main load-bearing materials and secondary auxiliary components and simulating them separately using beam and pole elements, and by introducing catenary theory to achieve initial state form finding for the conductor and ground wire with self-consistent elastic elongation and geometric length, the nonlinear tensile constraints of conductor and ground wire tension on the tower body and the mechanical transmission and dissipation effects between adjacent towers are perfectly reproduced, significantly improving the realism of the mechanical response analysis of large spatial truss structures.

[0028] This paper proposes a gradient displacement loading strategy for continuous large deformation of the surface in goaf areas, comprehensively recreating the real dynamic evolution process of disasters. Unlike traditional extreme value static single-step loading, this invention dynamically simulates the continuous non-uniform deformation process of the surface caused by the migration of rock strata in underground goaf areas by applying multiple gradients of vertical settlement displacement and horizontal offset to the intermediate tower foundation. This loading method effectively avoids the calculation non-convergence caused by single large deformations, and can output a complete continuous evolution trajectory of "settlement displacement - force flow redistribution - stiffness degradation," helping the evaluation system accurately capture each critical state of the structure from safety margin depletion and stress reorganization to final instability and failure.

[0029] The standardized closed-loop evaluation logic provides direct quantitative decision support for engineering route selection and disaster prevention and mitigation. The digital simulation evaluation method of this invention establishes a fully automated analysis chain from parameter input, coupled shape finding, continuous loading to comprehensive multi-dimensional index judgment. It not only performs high-precision "force-flow CT scans" of the safety status of existing operating lines, but also quantitatively compares the differences in anti-collapse performance of different tower type combinations under the same settlement conditions. The output of optimal tower system combinations and settlement safety threshold recommendations provides scientific and quantitative engineering basis for the selection of towers and span configuration for new transmission lines crossing mining subsidence areas, as well as for targeted reinforcement of existing lines, demonstrating extremely high industrial application value.

[0030] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart of a digital simulation evaluation method for the overall settlement and horizontal displacement of a power transmission tower system in a goaf area, according to an embodiment of the present invention. Figure 2 This is a visualized axial force cloud map in the digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in a goaf area according to an embodiment of the present invention; Figure 3 This is a visualized stress ratio cloud map in the digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in a goaf area according to an embodiment of the present invention. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0034] The following reference Figures 1 to 3 This invention describes a digital simulation evaluation method, equipment, and medium for the overall settlement and horizontal displacement of a goaf transmission tower system, provided by some embodiments of the present invention.

[0035] Some embodiments of this application provide a digital simulation evaluation method for the overall settlement and horizontal displacement of a power transmission tower system in a goaf.

[0036] To address the issues of missed warnings for chain reaction failures due to over-reliance on a single global maximum stress ratio in traditional power transmission tower safety assessments, and the limitations of single-tower static analysis in reflecting the highly nonlinear coupled mechanical behavior of multiple towers and lines, this disclosure proposes a dual-early warning digital simulation assessment framework based on "force flow redistribution path tracing." This invention overcomes the limitations of point-based assessment at the isolated component level. First, it establishes a high-fidelity hybrid coupling model of three towers and four lines, and introduces catenary form-finding technology to fully reproduce the tensile constraints of conductor and ground wire tension on the tower body and the mechanical transmission effect between adjacent towers. Second, it introduces a gradient loading mechanism simulating continuous large deformation of the surface in goaf areas, comprehensively reproducing the dynamic response history of the structure under complex forced displacement. Based on this, the key breakthrough of this invention lies in not blindly limiting itself to judging whether a single component has reached its yield or instability limit, but creatively extracting a set of key high-axial-force members across the entire tower and constructing a high-axial-force skeleton, thus spatially topologically and visually mapping the invisible main load-bearing channels. By collaboratively monitoring the ultimate state of the stress ratio of global components and the continuity and symmetry evolution of the high axial force skeleton, early warning of internal stiffness degradation, abnormal transfer of local loads and cluster instability effects can be achieved, thus providing a more forward-looking and systematic quantitative assessment method for anti-collapse of power transmission projects in goaf areas.

[0037] Specifically, this invention proposes a digital simulation evaluation method for the overall settlement and horizontal displacement of a power transmission tower system in a goaf area, such as... Figure 1 As shown, it includes the following steps S1-S5.

[0038] S1. Establish a hybrid coupled model of three towers and four lines, including intermediate towers and side towers. The main materials and major components of the transmission towers are simulated using beam elements, the secondary components are simulated using pole elements, and the conductors and ground wires are simulated using pole elements under tension only. Based on the catenary theory, the initial length of the conductors and ground wires is calculated iteratively to ensure that the geometry of the conductors and ground wires satisfies the convergence condition of elastic elongation and geometric length self-consistency under the action of self-weight and initial tension, thus completing the initial state form finding of the system. S2. Apply bottom consolidation and conductor end fixing constraints to the side towers in the three-tower four-line pole-beam hybrid coupling model, apply a preset range of vertical settlement displacement and / or horizontal displacement to each tower leg of the middle tower, and perform multi-gradient step-by-step loading to simulate the continuous gradual deformation of the surface of the goaf. S3. Extract the global displacement response data of the transmission tower system under various gradient displacement loading and the axial force data of all members of the tower; based on the axial force data, select a set of key members with a predetermined number of key members whose absolute axial force values ​​are among the highest, and extract or draw a high axial force skeleton and its visualization cloud map that reflects the internal main load-bearing channel based on the set of key members. S4. Extract the internal force data and section parameters of each member of the entire tower. Based on the calculation logic of the ultimate tensile strength bearing capacity of the tension member and the calculation logic of the ultimate stability bearing capacity of the compression member, calculate the stress ratio of each member of the entire tower under the current loading gradient. At the same time, combined with the extracted global displacement response data and settlement loading step size, calculate the overall lateral stiffness of the transmission tower system, the nonlinear growth rate of settlement-displacement, and the stiffness degradation coefficient of each member of the entire tower. S5. Compare the stress ratio of each member of the entire tower with a preset safety threshold to assess the component-level yield resistance or instability resistance; determine the continuity and symmetry of the high axial force frame based on the spatial distribution characteristics of the high axial force frame or the visualization cloud map; simultaneously monitor the degradation inflection point of the overall lateral stiffness, the abrupt change in the nonlinear growth rate of settlement-displacement, and the decrease in the stiffness degradation coefficient; when any one or more of the following conditions are met—stress ratio exceeding the limit, asymmetry or interruption of the high axial force frame, or the overall lateral stiffness, settlement-displacement nonlinear growth rate, and stiffness degradation coefficient reaching the preset instability threshold—an early warning of overall instability or collapse of the transmission tower system is output.

[0039] The following section will provide a detailed explanation of the specific implementation details for each step in the evaluation method.

[0040] S1. Establish a hybrid coupling model of three towers and four lines, including intermediate towers and side towers. The main materials and major components of the transmission towers are simulated using beam elements, the secondary components are simulated using pole elements, and the conductors and ground wires are simulated using pole elements under tension only. Based on the catenary theory, the initial length of the conductors and ground wires is calculated iteratively to ensure that the geometry of the conductors and ground wires meets the convergence condition of elastic elongation and geometric length self-consistency under the action of self-weight and initial tension, thus completing the initial state form finding of the system.

[0041] In a specific embodiment, the establishment of a hybrid coupling model of three towers and four conductors includes two parts: modeling the transmission towers and modeling the conductors and ground wires. For the transmission towers, the tower components are mechanically equivalently divided according to their structural characteristics. The main materials and main components that mainly bear bending moments and axial loads (such as main crossbeams, main diagonal members of the facade, and main crossarms) are assigned as spatial beam elements, which can be specifically simulated using BEAM188 spatial beam elements in finite element analysis software. The auxiliary structures that only bear axial tensile and compressive loads (such as auxiliary diagonal members and secondary cross members) are assigned as spatial pole elements, which can be specifically simulated using LINK8 spatial pole elements. In practical engineering applications, the steel type of the transmission tower can be selected according to the design drawings, such as Q235, Q355, Q420, etc., and its actual physical parameters are assigned in the model, such as elastic modulus (usually set to 206000MPa), yield stress, and Poisson's ratio (e.g., 0.3). Specific material parameter settings are shown in Table 1.

[0042] Table 1 Material Parameters

[0043] In some embodiments, to compensate for the shortcomings of the finite element pure rod system model in fully representing the mass of the node plates, bolted connections, and the added mass of the galvanized layer, and to make the dynamic and static responses more closely resemble reality, a mass correction process needs to be applied to the model. Specifically, using the actual design weight of the entire tower as a benchmark, the mass of the transmission tower is matched and verified with the actual design weight by amplifying the material density of the corresponding components. For example, for a straight-line tower model, the mass amplification factor can be 1.2; for a tension tower model, the mass amplification factor can be 1.3.

[0044] For modeling the conductor and ground wire (including conductors and ground wires) and insulator system, in a specific embodiment, both tension insulator strings and suspension insulator strings are treated as rigid bodies, simulated using rod elements, and given an elastic modulus much larger than that of conventional steel to reflect their rigid structural characteristics. To realistically reflect the stress mechanism and moment release boundary between components, the connection nodes between the insulator strings and the conductor / ground wire, and between the insulator strings and the tower body, are treated as spatial hinges. Furthermore, when calculating the dynamic or static response of the transmission tower-line coupling system, to effectively reduce the degree-of-freedom matrix of the entire tower model while ensuring calculation accuracy, the original split conductors are equivalently converted into single conductors by assigning corresponding mass and cross-sectional area. During the equivalence process, it is only necessary to ensure that the overall mass and cross-sectional area of ​​the equivalent single conductor are strictly consistent with the parameters of the corresponding split conductor.

[0045] In some embodiments, the conductors and ground wires are typical suspension flexible structures, whose mechanical constitutive characteristics mean they cannot withstand bending moments and pressures, only axial tensile forces, and plastic deformation caused by long-term operation is not considered. Therefore, in finite element modeling, the conductors and ground wires are simulated using only tensile spatial rod elements (such as LINK10 elements). It should be noted that the transmission tower system first defines the steady state under the combined action of its own weight and initial tensile force as the initial state, while the state under further external environmental deformation or loads is called the load state. The system must first undergo initial state determination based on self-weight equilibrium, i.e., form-finding analysis, before subsequent boundary loading can be carried out.

[0046] Specifically, the process of iteratively calculating the initial length of the conductor to complete the initial state shape finding includes the following program-controlled execution logic: The first step is to input the initial parameters. Input the coordinates of the two hanging points of the conductor and ground wire (including the elevation, span, and other positional parameters of the tower type) and the design horizontal tension or initial stress data given by the design specifications into the program framework.

[0047] The second step is theoretical arc length and shape-finding analysis. Based on the catenary theory (or in conventional tower structures, when the span is less than a preset value such as 500m and the height difference is less than a preset value such as 100m, the oblique parabolic approximation equation can also be used to reduce the amount of nonlinear calculation), assuming that the overhead conductor is a completely flexible ideal suspension cable subjected only to its own weight, the arc length of the conductor and ground wire is spatially integrated to derive its original geometric length parameters under strain-free conditions.

[0048] The third step is to calculate the elastic elongation. Based on the given initial tension, conductor cross-sectional area, and elastic modulus, calculate the elastic elongation of the conductor under its current weight and initial tension.

[0049] The fourth step is convergence judgment and parameter adjustment. The calculated elastic elongation is compared with the geometric length to determine if the current shape has reached stability, i.e., whether the residual between the two meets the preset error convergence condition. If the system determines that convergence has not occurred, the initial length parameter of the conductor is dynamically adjusted, and the catenary shape finding and integral solution steps are re-entered for the next iteration. This continues until the calculation result meets the convergence condition, indicating that the geometric shape and tension distribution of the conductor in the finite element model fully meet the actual design requirements. At this point, accurate initial length data is output for subsequent modeling and loading. The above nonlinear equation iteration process can be automated using programming tools combined with numerical solution algorithms known to those skilled in the art (such as the Newton-Raphson method, bisection method, etc.). This shape finding method eliminates the influence of mesh distortion on the internal forces of the structure, providing an accurate and stress-free initial physical model environment for the subsequent continuous settlement loading of the multi-tower model.

[0050] In one specific embodiment, the parameter settings for typical model conductors and ground wires are shown in Table 2.

[0051] Table 2 Tower Parameters

[0052] In one specific embodiment, the establishment of a three-tower, four-line hybrid coupled model including intermediate towers and side towers also includes constructing various differentiated tower system combination models based on the actual line layout evaluation requirements. Since the displacement transfer characteristics and internal force distribution evolution laws of different tower structures under forced settlement are fundamentally different, six typical three-tower, four-line coupled tower systems can be established for digital simulation preparation to comprehensively evaluate various boundary conditions. Based on the different structural types of the intermediate towers, these six tower systems are mainly divided into two basic groups: when the intermediate tower is set as a tension tower, straight-line tower-tension tower-tension tower combination, straight-line tower-tension tower-straight-line tower combination, and tension tower-tension tower-tension tower combination models can be established respectively; when the intermediate tower is set as a straight tower, straight-line tower-tension tower combination, straight-line tower-straight-line tower combination, and tension tower-straight-line tower-tension tower combination models can be established respectively.

[0053] Furthermore, when establishing the aforementioned multiple tower system combination models, to ensure that the only control variable in the evaluation conclusion is "tower type difference," it is necessary to unify and normalize the non-evaluation interference parameters of each model. Specifically, the span parameters of all combination models participating in the evaluation are uniformly set to standard preset values, such as 300m, to eliminate the interference of span differences on the structural stiffness and displacement response results. In terms of boundary treatment, for all tower system combinations, the bottom nodes of the side towers are set to fully consolidated, and fixed constraint boundary conditions are applied to the ends of the conductors at the span edges. By sequentially establishing the aforementioned tower system combinations and performing the aforementioned form-finding iterations, when the suspension state of the conductor at the mid-span is found to be completely consistent with the theoretical calculation value of the catenary, the correctness and high fidelity of the established coupled model can be verified. This process provides a complete and accurate digital physical model analysis library for subsequent quantitative lateral comparison of structural collapse resistance under a unified continuous settlement loading standard.

[0054] In one specific embodiment, the configuration of six three-tower, four-line coupled tower system combinations involved in a certain transmission line is shown in Table 3.

[0055] Table 3 Tower System Combinations

[0056] The specific implementation details of step S2 will be described in detail below.

[0057] S2. Apply bottom consolidation and conductor end fixing constraints to the side towers in the three-tower, four-line pole-beam hybrid coupling model, apply a preset range of vertical settlement displacement and / or horizontal displacement to each tower leg of the middle tower, and perform multi-gradient step-by-step loading to simulate the continuous and gradual deformation of the surface of the goaf.

[0058] In one specific embodiment, to accurately simulate the actual stress boundary of the transmission tower-line system above the goaf, static global spatial constraints must first be applied to the coupled model. Specifically, the bottom nodes of the two end towers in the three-tower, four-line model are kept in a fully fixed state, i.e., their translational degrees of freedom in the X, Y, and Z directions and rotational degrees of freedom around the three coordinate axes are restricted by the finite element program; at the same time, the ends of the conductors at the two end span edges are kept fixed to equivalently simulate the stable tension anchoring effect of the infinitely far line segment on the current analysis span. This boundary treatment ensures that when the middle tower is subjected to forced displacement, its deformation energy can be accurately transferred and dissipated to the adjacent end towers through the conductors, thus perfectly matching the highly coupled characteristics of multiple towers and multiple lines in real engineering.

[0059] In some embodiments, the actual surface displacement in the goaf includes not only vertical surface collapse but also horizontal tensile or compressive deformation due to the migration of overlying strata. Therefore, this embodiment sets diverse displacement conditions when applying continuous deformation boundary conditions. Forced spatial displacement load boundary conditions are simultaneously applied to the bottom nodes of the four legs of the intermediate tower. Specific conditions can be divided into: simultaneously applying settlement displacement in the Z direction (i.e., vertical) to each of the four legs of the intermediate tower; or optionally applying horizontal displacement in the X and / or Y directions to simulate horizontal tensile or compressive deformation in the goaf. In actual digital simulation, to clarify the impact of different stress mechanisms on structural safety, vertical settlement and horizontal displacement are usually solved and evaluated separately as two independent conditions.

[0060] In one specific embodiment, to realistically reproduce the dynamic physical characteristic of goaf settlement as "gradually changing from small to large," this application adopts a multi-gradient progressive loading strategy instead of the traditional single-step extreme value loading. Taking the vertical settlement case as an example, the limit simulation range of vertical settlement displacement is set to 0 to 4m, and progressive loading is performed with a preset step size gradient of 0.5m. The specific execution logic is as follows: the continuously changing goaf foundation deformation process is discretized into multiple consecutive loading steps; under the control of the finite element calculation program, within each individual loading step, the spatial displacement load boundary condition of the current step size (e.g., 0.5m) is forcibly applied to the bottom nodes of the four tower legs of the intermediate tower, and the large deformation nonlinear solver is called to recalculate and output the static equilibrium state of the tower line system under the displacement boundary; when the calculation of this step converges, the loading step is accumulated cyclically, and the next incremental displacement of 0.5m is applied on the basis of the previous displacement state until the total accumulated displacement reaches the limit deformation range of the simulation design (i.e., 4m).

[0061] The loading execution logic that combines gradient discretization with iterative solving not only effectively avoids the problems of stiffness matrix singularity and non-convergence caused by applying a large deformation load in a single step at the algorithm level, but also, more importantly, it can completely preserve and output the temporal evolution of the internal force response of the structure during continuous settlement. This provides continuous and rigorous basic data samples for tracking the "force flow redistribution path" of the structure from small deformation, stress reorganization to ultimate instability in subsequent steps.

[0062] The specific implementation details of step S3 will be described in detail below.

[0063] S3. Extract the global displacement response data of the transmission tower system under various gradient displacement loading and the axial force data of all members of the tower; based on the axial force data, select a preset number of key members with the highest absolute value of axial force, and extract or draw a high axial force skeleton and its visualization cloud map that reflects the internal main load-bearing channel based on the key member set.

[0064] In one specific embodiment, the extraction of global displacement response data is mainly achieved by calling the post-processing module of the finite element solver to extract the spatial displacement of each node of the entire tower under each continuous settlement displacement gradient (e.g., every 0.5m as a reading frequency). This allows for the plotting of displacement contour maps and maximum displacement variation curves for each tower at different settlement depths (or horizontal offsets). Through this displacement data, the spatial distribution pattern of structural deformation under different tower system combinations can be visually observed and extracted. When the intermediate tower is a tension tower, the overall displacement law of the system is as follows: For the straight tower of the side span, the displacement is concentrated at the bird's beak position (i.e., the junction of the ground wire suspension point and the conductor suspension point), and the deformation shows the characteristics of being symmetrical from left to right and decreasing uniformly from high to low; For the tension tower of the side span, the displacement is mainly concentrated at the horizontal position of the ground wire suspension point, and also shows a state of decreasing uniformly from high to low; For the intermediate tension tower located at the center of forced loading, the maximum displacement is located at the inner ground wire suspension point, and shows a spatial attenuation law that decreases simultaneously from the inner side to the outer side and from the top to the bottom.

[0065] When the intermediate tower is a straight tower, the overall displacement pattern of the system is as follows: the displacement of the straight towers in the side spans is also concentrated at the two "bird's beak" points and remains symmetrical; the displacement of the tension towers in the side spans is concentrated at the horizontal position of the ground wire suspension point; while for the intermediate straight tower, its maximum displacement is located at the intermediate conductor suspension point, and at the other conductor and ground wire suspension points, the waist of the tower body, and the cross diaphragms, significant deformation also occurs. The overall structural deformation exhibits a special distribution characteristic of first decreasing and then increasing from the middle to both sides. The above detailed global displacement response characteristics provide direct data support for macroscopically judging the tilting, torsional trends, and deformation coordination capabilities of multi-tower coupled structures.

[0066] In some embodiments, to penetrate the "stress averaging" appearance of complex statically indeterminate truss structures and capture the true internal force transfer paths, this embodiment performs a screening and extraction process targeting a specific set of key members. Specifically, for any displacement loading gradient, axial internal force data for all members of the entire tower are extracted from the finite element analysis results file, and the absolute values ​​of the axial forces of all members are taken to uniformly consider the ultimate bearing states of tension and compression. Subsequently, the members are sorted in descending order according to the magnitude of their absolute axial force values, and a predetermined number of members (e.g., the top 200 members by absolute axial force value) are selected to form the set of key members. The principle for selecting this predetermined number is to filter out a large number of secondary components that are in a low-stress state and do not participate in the main force transmission, while ensuring that the remaining members are sufficient for spatial coherence.

[0067] Combination Figure 2 The visualization of axial force cloud map drawing process, as shown in one specific embodiment, involves the extraction and drawing of the high axial force skeleton and its visualization cloud map through automated implementation by calling or compiling a specific data post-processing program. The specific execution logic is as follows: First, the program extracts the three-dimensional node coordinates of the entire tower, the line numbers of each member, the element numbers, and the corresponding axial force values ​​of the entire element from the finite element underlying file; second, through the one-to-one correspondence between coordinates, line numbers, and element numbers, the spatial topology connection of the key member set is reconstructed in the three-dimensional digital space; finally, during the drawing of the local axial force cloud map, different color depth indicators are assigned to axial force values ​​of different gradient levels. For example, a color gradient from black to red to white can be set to sequentially map and increase the magnitude of the axial force.

[0068] Through the aforementioned three-dimensional spatial mapping and data rendering, the key member assembly forms an intuitive high-axial-force skeleton topology network in three-dimensional space. This high-axial-force skeleton is essentially a visual representation of the main load-bearing channels (force flow paths) within the tower body under the current settlement deformation state. Engineers or automated judgment algorithms can clearly observe the differences in internal force characteristics of different tower types under settlement: for example, when the intermediate tower is a tension tower, the axial force of the main tower material below the conductor suspension point is larger, while it is smaller near the transverse diaphragm, and the high-axial-force members form a high-axial-force skeleton extending from the conductor and ground wire suspension points. Further analysis and comparison show that in the aforementioned Group A tower system, the A3 tower system combination (i.e., tension tower-tension tower-tension tower) forms the most complete high-axial-force skeleton under settlement, effectively maintaining the closed transmission of force flow and exhibiting relatively superior anti-collapse capability. When the intermediate tower is a straight tower, the axial force of the main material near the intermediate conductor and ground wire suspension points is more concentrated, extending into a complete high-axial-force skeleton. This extraction and visualization step transforms the traditional dark box of internal forces into a transparent "force flow CT scan," laying an irreplaceable data and image foundation for implementing forward-looking structural instability early warning in subsequent steps.

[0069] The specific implementation details and technical principles of step S4 will be introduced in detail below.

[0070] S4. Extract the internal force data and section parameters of each member of the entire tower. Based on the calculation logic of the ultimate tensile strength bearing capacity of the tension member and the calculation logic of the ultimate stability bearing capacity of the compression member, calculate the stress ratio of each member of the entire tower under the current loading gradient. At the same time, combined with the extracted global displacement response data and settlement loading step size, calculate the overall lateral stiffness of the transmission tower system, the nonlinear growth rate of settlement-displacement, and the stiffness degradation coefficient of each member of the entire tower.

[0071] In one specific embodiment, after extracting the internal force data and corresponding cross-sectional geometric parameters of all members of the tower using finite element analysis software, differentiated stress ratio calculation logic needs to be executed for different stress states of the members. For axially tensioned members, instability (bending) is not a critical issue; their ultimate bearing capacity is mainly due to the yielding of the steel. Therefore, when the internal forces of the member exhibit axial tension, the stress ratio is calculated using the following formula:

[0072] in, The stress ratio of an axially tensioned member. This refers to the design or ultimate bearing capacity of an axially tensioned member. This refers to the net cross-sectional area of ​​a structural member (such as angle steel). This is the design value for the tensile strength of the steel.

[0073] In some embodiments, the situation is more complex for axially compressed members, where failure modes are not limited to strength failure but more commonly include instability failure (i.e., buckling). Therefore, their load-bearing capacity must consider both strength and stability. When the internal forces of the member exhibit axial compression, the stress ratio is calculated using the following formula:

[0074] in, This represents the stress ratio of an axially compressed member. is the stability coefficient of the axially compressed member, which is the core of the entire compression calculation and reflects the reduced load-bearing capacity of the member due to its slenderness ratio; A is the gross cross-sectional area of ​​the member.

[0075] In one specific embodiment, the stability coefficient of the axially compressed member depends on the grade of steel, the slenderness ratio of the member, and the type of cross-section. The stability coefficient and the slenderness ratio exhibit an inverse relationship; that is, the stability coefficient decreases as the slenderness ratio increases. The slenderness ratio is a key indicator for measuring the flexibility of the member, and its calculation formula is as follows:

[0076] in, Slenderness ratio; The calculated length of the component is determined by the physical constraints at both ends of the component. This refers to the radius of gyration of the cross-section about the corresponding principal axis. For example, for commonly used equilateral angle steel members, when the steel grade reaches Q235 and above, its cross-section type is usually classified as Class A. Based on this, it is necessary to calculate the slenderness ratio of the angle steel about two principal axes (x-axis and y-axis) and about the smallest principal axis (u-u axis, i.e., the oblique axis), and extract the maximum slenderness ratio. In actual digital simulation, the accurate stability coefficient can be obtained by substituting this maximum slenderness ratio into the stability curve of the corresponding Class A cross-section axially compressed member in the current steel structure design code, either by looking up or by interpolation. This well-known code-based reference method ensures the engineering reliability of the underlying mechanical parameters.

[0077] In one specific embodiment, in order to quantitatively describe the stiffness degradation process, displacement abruptness characteristics, and non-uniform deformation risk of the transmission tower system under the action of goaf settlement, in addition to the stress ratio calculation at the component level mentioned above, this step also combines the global displacement response data extracted in step S3 with the settlement loading step size to simultaneously calculate three quantitative mechanical indices at the system level: First, calculate the overall lateral stiffness of the transmission tower system. Overall lateral stiffness is defined as the equivalent horizontal force required to generate a unit horizontal displacement at the top of the tower, reflecting the system's overall ability to resist lateral deformation. The calculation is performed using the following formula:

[0078] in, For the overall lateral stiffness of the transmission tower system; The equivalent horizontal resultant force acting at the suspension point of the conductor at the top of the tower (which can be obtained by superimposing the horizontal components of the conductor tension), is expressed in N; The displacement of the tower top in the horizontal direction (such as X or Y) is expressed in meters (m).

[0079] Secondly, the nonlinear growth rate of settlement-displacement is calculated. This indicator is used to accurately identify whether the tower displacement exhibits a "sudden" nonlinear increase exceeding the foundation settlement rate during the settlement process. It is calculated using the following formula:

[0080] in, The nonlinear growth rate of settlement-displacement; The maximum displacement of the tower body at the current settlement depth h (can be vertical or horizontal displacement), in meters; This represents the settlement loading step size, i.e., the amount of settlement change.

[0081] Finally, the stiffness degradation coefficient of each member in the entire tower is calculated. For any member in the tower, its stiffness degradation coefficient is defined as the ratio of the current tangent modulus to the initial elastic modulus. This coefficient is used to accurately quantify the degree of mechanical deterioration of the member due to increased stress, leading to plasticity or buckling. The specific formula is as follows:

[0082] in, Let be the stiffness degradation coefficient of member i; This is the initial elastic modulus of the steel. Let be the tangent modulus of member i under the current stress state.

[0083] In some embodiments, combined with Figure 3 As shown, after completing the above index calculations, to facilitate intuitive structural safety assessment, step S4 also includes calling a data processing program to draw a stress ratio visualization cloud map of the entire tower. The generation logic of this stress ratio cloud map analysis is similar to that of the aforementioned axial force cloud map. Figure 1 To achieve this, the axial force values ​​mapped at the program's underlying level are replaced with calculated stress ratio values, and corresponding gradient color markers are applied for 3D spatial rendering. This visualized cloud map allows for highly intuitive identification of the global maximum stress ratio distribution location and weak members approaching the ultimate bearing state, providing quantitative criteria for the next step of implementing system-level comprehensive safety early warning.

[0084] It should be noted that, Figure 2 and Figure 3 The X, Y, and Z axes of the three-dimensional coordinate system together constitute the three-dimensional spatial geometric coordinates of the power transmission tower model. The X and Y axes represent the lateral and longitudinal geometric dimensions of the power transmission tower projected onto the ground plane (such as the base span and tower width), while the Z axis represents the vertical elevation of the tower. The three-dimensional coordinate system accurately reflects the topological connection positions of all tower members in three-dimensional space, and its coordinate values ​​are expressed in meters (m).

[0085] exist Figure 2 In the visualized axial force cloud map shown, the color scale on the right represents the absolute value of the axial internal forces (axial forces) in all members of the tower. The diagram uses a color gradient from dark to light to map the axial force values ​​from low to high. Through this axial force cloud map and its color depth, the high-axial-force skeleton that bears the main force flow can be intuitively located and extracted in three-dimensional space.

[0086] exist Figure 3The visualized stress ratio cloud map shown has a color scale on the right representing the calculated stress ratio values ​​for each member of the entire tower. The stress ratio is the ratio of the actual stress on a member to its ultimate bearing capacity, and is a dimensionless physical quantity. This diagram uses a gradient of warm and cool colors (such as transitioning from dark blue for a low stress ratio to dark red for a high stress ratio) to visually reflect the degree to which a member is approaching its yield or instability limit state, and is used to quickly identify weak members in the structure whose stress ratio is close to or exceeds a safety threshold (such as 1.0).

[0087] S5. Compare the stress ratio of each member of the entire tower with a preset safety threshold to assess the component-level yield resistance or instability resistance; determine the continuity and symmetry of the high axial force frame based on the spatial distribution characteristics of the high axial force frame or the visualization cloud map; simultaneously monitor the degradation inflection point of the overall lateral stiffness, the abrupt change in the nonlinear growth rate of settlement-displacement, and the decrease in the stiffness degradation coefficient; when any one or more of the following conditions are met—stress ratio exceeding the limit, asymmetry or interruption of the high axial force frame, or the overall lateral stiffness, settlement-displacement nonlinear growth rate, and stiffness degradation coefficient reaching the preset instability threshold—an early warning of overall instability or collapse of the transmission tower system is output.

[0088] In one specific embodiment, the component-level assessment of yield strength or instability is determined by monitoring and judging the global maximum stress ratio among the stress ratios of all members in the entire tower calculated in S4 above. Specifically, a preset safety threshold of 1.0 is set. If the assessment results show that the stress ratio of any member is greater than 1.0, it is determined that the member has experienced local yielding or instability failure. Combined with specific engineering simulation scenarios, for example, when the simulated goaf settlement depth reaches 4m, it may be calculated that the stress ratio of all tower components is less than 1.0 and no direct failure has occurred. In this case, even if this warning has not been triggered, the system will still locate the weak area where the maximum stress ratio appears (usually concentrated in the connecting members at the conductor suspension point, the main materials distributed diagonally on the tower body, and the main materials near the ground wire suspension point) as a reference for subsequent reinforcement.

[0089] In some embodiments, due to the extremely high static indeterminate nature of large tower-line coupled structures, local non-yielding does not necessarily indicate overall safety. Therefore, this invention independently performs system-level topology evolution tracking for high-axial-force skeletons, separate from global maximum stress ratio monitoring. By determining the continuity and symmetry of the high-axial-force skeleton, if the main load-bearing loop of the high-axial-force skeleton fails to remain closed (i.e., is interrupted), or if the spatial distribution of high-axial-force components is asymmetrically offset due to load concentration on one side or in one layer, then an abnormal force flow redistribution path is determined. This determination logic can effectively penetrate the masking effect of "stress averaging" and identify chain-like collapse precursors caused by abnormal load transfer to non-critical components.

[0090] In one specific embodiment, to further perform high-precision mathematical characterization of the structure's stiffness degradation and displacement abrupt changes, this step simultaneously monitors the three quantitative mechanical indices calculated in S4 and sets a rigorous quantitative instability threshold. First, the curve of overall lateral stiffness versus settlement depth is monitored. When the curve shows a significant downward inflection point, it indicates a sudden drop in the structure's overall ability to resist lateral deformation, and the settlement amount corresponding to this inflection point is determined as the initial threshold for system stiffness instability. Second, the nonlinear growth rate of settlement-displacement is monitored. When this index is greater than or equal to 1.0, it means that the rate of increase in structural displacement has caught up with or exceeded the forced loading rate of foundation settlement, indicating that the structure exhibits abrupt growth characteristics and has entered the nonlinear instability warning zone. Finally, the stiffness degradation coefficient of each member in the key member set is extracted and its average value is calculated. This average value reflects the health status of the main load-bearing channel; when the average value continues to decrease and falls below the preset threshold of 0.85, the structure is determined to have experienced significant stiffness degradation.

[0091] In some embodiments, based on the aforementioned multi-dimensional judgment logic, this system executes a collaborative early warning mechanism. In any of the five scenarios—local yielding or instability failure, abnormal force flow redistribution path, initial threshold of system stiffness instability, entry into the nonlinear instability warning zone, and significant stiffness degradation of the structure—if any one or more of these occur, the system immediately triggers a collapse precursor warning. Based on this warning result, the evaluation method ultimately generates a standardized comparative output, including: a horizontal comparison of the mechanical response and triggering critical points of the six different intermediate and side tower combinations established above under the same settlement gradient, outputting optimal and worst tower combination recommendations; and, in conjunction with specific geological data, directly outputting structural settlement safety threshold recommendations suitable for engineering construction or disaster prevention reinforcement.

[0092] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0093] Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A digital simulation evaluation method for the overall settlement and horizontal displacement of a power transmission tower system in a goaf, characterized in that, include: S1. Establish a hybrid coupled model of three towers and four lines, including intermediate towers and side towers. The main materials and major components of the transmission towers are simulated using beam elements, the secondary components are simulated using pole elements, and the conductors and ground wires are simulated using pole elements under tension only. Based on the catenary theory, the initial length of the conductors and ground wires is calculated iteratively to ensure that the geometry of the conductors and ground wires satisfies the convergence condition of elastic elongation and geometric length self-consistency under the action of self-weight and initial tension, thus completing the initial state form finding of the system. S2. Apply bottom consolidation and conductor end fixing constraints to the side towers in the three-tower four-line pole-beam hybrid coupling model, apply a preset range of vertical settlement displacement and / or horizontal displacement to each tower leg of the middle tower, and perform multi-gradient step-by-step loading to simulate the continuous gradual deformation of the surface of the goaf. S3. Extract the global displacement response data of the transmission tower system under various gradient displacement loading and the axial force data of all members of the tower; based on the axial force data, select a set of key members with a predetermined number of key members whose absolute axial force values ​​are among the highest, and extract or draw a high axial force skeleton and its visualization cloud map that reflects the internal main load-bearing channel based on the set of key members. S4. Extract the internal force data and section parameters of each member of the entire tower. Based on the calculation logic of the ultimate tensile strength bearing capacity of the tension member and the calculation logic of the ultimate stability bearing capacity of the compression member, calculate the stress ratio of each member of the entire tower under the current loading gradient. At the same time, combined with the extracted global displacement response data and settlement loading step size, calculate the overall lateral stiffness of the transmission tower system, the nonlinear growth rate of settlement-displacement, and the stiffness degradation coefficient of each member of the entire tower. S5. Compare the stress ratio of each member of the entire tower with a preset safety threshold to assess the component-level yield resistance or instability resistance; determine the continuity and symmetry of the high axial force frame based on the spatial distribution characteristics of the high axial force frame or the visualization cloud map; simultaneously monitor the degradation inflection point of the overall lateral stiffness, the abrupt change in the nonlinear growth rate of settlement-displacement, and the decrease in the stiffness degradation coefficient; when any one or more of the following conditions are met—stress ratio exceeding the limit, asymmetry or interruption of the high axial force frame, or the overall lateral stiffness, settlement-displacement nonlinear growth rate, and stiffness degradation coefficient reaching the preset instability threshold—an early warning of overall instability or collapse of the transmission tower system is output.

2. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S1, the establishment of the three-tower, four-line beam hybrid coupling model including the intermediate tower and the side towers includes: Based on the structural characteristics, the components of the power transmission tower are mechanically equivalently divided. The main materials and structural skeleton that mainly bear bending moment and axial load are assigned as spatial beam elements; the auxiliary structures that only bear axial tensile and compressive loads are assigned as spatial rod elements. By assigning mass and cross-sectional area to the conductor, the split conductors in the conductor are equivalently converted into a single conductor, and the insulator string is set as a rigid rod unit with a high elastic modulus. The model is subjected to mass correction processing, and the mass of the power transmission tower is matched and verified with the actual design weight by increasing the material density.

3. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S1, the step of iteratively calculating the initial length of the conductor includes: Input the coordinates of the two hanging points of the conductor and the design horizontal tension; Using the catenary theory or the parabola approximation equation, the original geometric length of the conductor arc length under strain-free state is derived by integral calculation. Calculate the elastic elongation of the conductor under its own weight and initial tension, and determine whether the difference between the original geometric length and the elastic elongation meets the preset error convergence condition; if not, dynamically adjust the initial length parameter and re-enter the iteration until the convergence condition is met and the accurate initial length data is output.

4. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S2, the step-by-step loading with multiple gradients includes: The continuous and gradual deformation process of the foundation in the goaf is discretized into multiple loading steps; Within each loading step, a spatial displacement load boundary condition of a preset step length is forcibly applied to the bottom node of the intermediate tower, and the static equilibrium state of the tower line system under the displacement boundary is recalculated. The loading step distance is cyclically increased until the total accumulated displacement reaches the limit deformation range of the simulation design, so as to obtain the evolution history of the structural response during continuous settlement.

5. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S3, the key member set is screened and the high axial force skeleton is extracted, including: From the extracted axial force data of all tower members, for any loading gradient, calculate the absolute value of the axial force of all members and sort them in descending order; The preset number of top-ranked members are selected to form a set of key members, and the node coordinates and topological connections of each member in the set of key members are obtained. Through three-dimensional spatial mapping, the key members and their axial force values ​​are mapped into a high axial force skeleton spatial continuity topology network, which is used to characterize the main force transmission path of the structure under the current deformation state.

6. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S4, calculations are performed based on the ultimate tensile strength bearing capacity calculation logic and the ultimate stability bearing capacity calculation logic for compression members, respectively, including: When the internal forces of the member are in an axially tensile state, the method for calculating the stress ratio includes: in, The stress ratio of an axially tensioned member. This refers to the design or ultimate bearing capacity of an axially tensioned member. Let be the net cross-sectional area of ​​the component. This is the design value for the tensile strength of the steel. When the internal forces of the member are in a state of axial compression, the method for calculating the stress ratio includes: in, The stress ratio of an axially compressed member. Let A be the stability coefficient of the axially compressed member, and A be the gross cross-sectional area of ​​the member. The stability coefficient of the axially compressed member is determined based on the member's slenderness ratio; The method for calculating the slenderness ratio includes: in, For the slenderness ratio, The calculated length of the component. Let be the radius of gyration of the cross section about the corresponding principal axis; The stability coefficient of the axially compressed component is negatively correlated with the slenderness ratio.

7. The digital simulation evaluation method for the overall settlement and horizontal displacement of the transmission tower system in the goaf area according to claim 1, characterized in that, In S4, the method for calculating the overall lateral stiffness of the transmission tower system includes: in, For the overall lateral stiffness of the transmission tower system; This is the equivalent horizontal resultant force acting at the suspension point of the conductor and ground wire at the top of the tower; This corresponds to the horizontal displacement of the tower top.

8. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S4, the method for calculating the nonlinear growth rate of settlement-displacement includes: in, The nonlinear growth rate of settlement-displacement; This represents the maximum displacement of the tower body at the current settlement depth h. This represents the settlement loading step size, i.e., the amount of settlement change.

9. The digital simulation evaluation method for the overall settlement and horizontal displacement of the transmission tower system in the goaf area according to claim 1, characterized in that, In S4, the calculation method for the stiffness degradation coefficient of each member of the entire tower includes: in, Let be the stiffness degradation coefficient of member i; This is the initial elastic modulus of the steel. Let be the tangent modulus of member i under the current stress state.

10. The digital simulation evaluation method for the overall settlement and horizontal displacement of the power transmission tower system in the goaf area according to claim 1, characterized in that, In S5, the assessment logic for the early warning of overall instability or collapse of the output transmission tower system includes: The global maximum stress ratio is extracted from the stress ratio of each member of the entire tower and monitored. If the stress ratio of any member is greater than 1.0, it is determined that local yielding or instability failure has occurred. Track the topological evolution of the high axial force skeleton. If the main load-bearing loop of the high axial force skeleton is not kept closed, or if the spatial distribution of the high axial force components is asymmetrically offset due to load concentration on a certain side or in a certain layer, it is determined that the force flow redistribution path is abnormal. When the curve of the overall lateral stiffness as a function of settlement depth shows a downward inflection point, it is determined to be the initial threshold for system stiffness instability. When the nonlinear growth rate of settlement-displacement is greater than or equal to 1.0, the structure is determined to have entered the nonlinear instability warning zone. The stiffness degradation coefficient of each member in the set of key members is extracted and the average value is calculated. When the average value is less than 0.85, it is determined that the structure has undergone significant stiffness degradation. A collapse precursor warning is triggered when any of the following occurs: local yielding or instability failure, abnormal force flow redistribution path, reaching the initial threshold of system stiffness instability, entering the nonlinear instability warning zone, or significant stiffness degradation of the structure.

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