Method and system for evaluating the load bearing effect of a screw anchor foundation

Abstract

The application discloses a spiral anchor foundation bearing effect evaluation method and system, relates to the technical field of finite element analysis, and comprises the following steps: establishing a soil body and a spiral anchor finite element model, setting a boundary condition, and obtaining finite element data; according to the finite element data, introducing a local damage variable based on a stress-strain degradation function, simulating local shear band development, and generating first damage data, wherein the first damage data comprises a first stress-strain curve and a first local damage variable; stratifying the soil body, optimizing the first damage data based on layer internal constraints, and obtaining second damage data; and calculating full-field stress, displacement and bearing capacity based on a finite element solver according to the second damage data for effect evaluation; and the problems of inaccurate spiral anchor effect evaluation caused by soil body nonlinear behavior and stratified heterogeneous effects are solved.

Description

Technical Field

[0001] This invention relates to the field of finite element analysis technology, and more specifically, to a method and system for evaluating the bearing capacity of helical anchor foundations. Background Technology

[0002] Currently, most methods for evaluating the effects of helical anchor foundations rely on finite element analysis (FEM). By establishing a finite element model of the soil-helical anchor and setting boundary conditions and loading methods, the stress distribution, displacement response, and overall bearing capacity curve between the soil and the helical anchor can be calculated. This type of method has been widely used in engineering practice. Through the finite element solver, the interaction between the soil and the helical anchor can be simulated relatively accurately, providing a reference for the design and construction of helical anchors. These evaluation methods based on finite element analysis belong to the existing mature technical system.

[0003] However, existing finite element analysis typically relies on classical elastoplastic constitutive models, such as the Mohr-Coulomb model. While these models are effective in characterizing the overall strength and deformation properties of soil, they fall short when dealing with significant nonlinear behavior. For example, when a helical anchor experiences local slippage, shear band development, and gradual failure evolution under load, traditional constitutive models often fail to accurately reflect this process from local damage to overall failure, leading to significant deviations in bearing capacity prediction. To address this deficiency, researchers have begun to incorporate damage mechanics into soil analysis. By establishing a stress-strain degradation function in the finite element model and introducing local damage variables, the gradual degradation of soil stiffness as damage develops can be characterized at the element level, thus more realistically reflecting the nonlinear failure mechanism of soil.

[0004] Although the introduction of damage mechanics has theoretically compensated for the shortcomings of traditional constitutive models, its application in complex soils still faces new obstacles. Soil possesses inherent heterogeneity and stratification, and damage variables between different elements may exhibit excessive fluctuations or unreasonable distributions. Furthermore, the mechanical curves between adjacent soil layers are prone to abrupt changes, making it difficult to guarantee the continuity of the degradation stress-strain curve. These problems not only weaken the stability of damage mechanics methods in finite element calculations but may also lead to evaluation results deviating from the actual mechanical behavior of soil. Therefore, how to further address the heterogeneity and stratification effects of soil based on the introduction of damage mechanics has become a crucial issue that urgently needs to be addressed. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method and system for evaluating the bearing effect of helical anchor foundations. By introducing a stress-strain degradation function based on damage mechanics and combining it with a soil stratification constraint optimization method, the inaccurate evaluation of the helical anchor effect caused by the nonlinear behavior of soil and the stratified heterogeneity effect is solved.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This application discloses a method for evaluating the bearing capacity of a helical anchor foundation, comprising the following steps: establishing a finite element model of the soil and the helical anchor, setting the boundary conditions of the model, and obtaining finite element data through calculation; based on the finite element data, introducing local damage variables through constitutive degradation to simulate shear band development, generating first damage data; applying spatial constraints to the soil to optimize the first damage data, obtaining corrected second damage data; performing finite element calculations based on the second damage data, and outputting results for evaluating the bearing capacity.

[0008] In a preferred embodiment, the establishment of finite element models of the soil and the helical anchor, setting boundary conditions for the models, and obtaining finite element data through calculation specifically involves: establishing three-dimensional finite element models of the soil and the helical anchor based on geological and geometric data; setting interaction relationships between the soil and helical anchor models to simulate soil-structure contact behavior, forming a complete finite element model; applying boundary conditions and loads to the finite element models, wherein the boundary conditions include constraints on the bottom and lateral movement of the soil, and the loads are vertical tensile forces applied to the upper end of the helical anchor; and solving the finite element model with applied boundary conditions and loads to obtain finite element data.

[0009] In a preferred embodiment, the step of introducing local damage variables through constitutive degradation based on finite element data to simulate shear band development and generate first damage data specifically involves: using each soil mesh element in the finite element model as a calculation unit; updating the local damage variables of each element through a constitutive relation evolution algorithm based on the stress-strain state of each element; identifying and marking elements that have experienced local failure based on the updated local damage variables; and summarizing the damage evolution results of all elements to generate the first damage data.

[0010] In a preferred embodiment, updating the local damage variables of each element based on its stress-strain state using a constitutive evolution algorithm includes constructing an element stress-strain degradation function based on damage mechanics principles. Specifically, this involves: initializing the local damage variables of each soil element; obtaining the current mechanical state of each element; calculating and updating the local damage variables piecewise according to the current mechanical state and a predetermined damage evolution rule; and generating the element stress-strain degradation function based on the updated local damage variables.

[0011] In a preferred embodiment, the step of summarizing the damage evolution results of all elements to generate the first damage data further includes obtaining the first stress-strain curve, specifically: obtaining the updated local damage variables of each soil element and their corresponding equivalent stress and equivalent strain; mapping the local damage variables to element stress using the stress-strain degradation function based on the local damage variables and equivalent stress to obtain the degradation stress; pairing the equivalent strain with the degradation stress to generate the degradation stress-strain curve of each element.

[0012] In a preferred embodiment, the step of applying spatial constraints to the soil to optimize the first damage data and obtain the corrected second damage data specifically involves: dividing the soil in the finite element model into multiple soil layers with different soil properties based on geological exploration data; and for each soil layer after division, optimizing the damage parameters in the first damage data based on its discrete characteristics to obtain corrected damage data that better reflects the actual mechanical response of the soil layer.

[0013] In a preferred embodiment, the step of dividing the soil in the finite element model into multiple soil layers with different soil properties based on geological exploration data specifically involves: acquiring and organizing the geological exploration data of the site; generating a one-dimensional initial sequence for each borehole based on the rock and soil names and bottom elevations of each layer in the geological exploration data; performing spatial interpolation on the bottom elevations of each rock and soil layer based on the one-dimensional initial sequence to generate a three-dimensional level function characterizing the spatial distribution of each rock and soil layer; using the three-dimensional level function, dividing the entire site vertically into several three-dimensional soil layers; and mapping each soil element in the finite element mesh to its corresponding three-dimensional soil layer.

[0014] In a preferred embodiment, for each divided soil layer, the damage parameters in the first damage data are optimized based on its discrete characteristics to obtain corrected damage data that better reflects the actual mechanical response of the soil layer. Specifically, for each soil layer, the first damage data of all soil units within it is obtained; based on the first damage data, the intra-layer statistical characteristics of the soil layer are analyzed; according to the intra-layer statistical characteristics, the damage data of each unit within the soil layer is optimized, the optimization process including identifying abnormal units that differ significantly from the intra-layer statistical characteristics and correcting the damage variables of the abnormal units according to the statistical characteristics; the interface region of adjacent soil layers is smoothed; and the optimized damage data of all soil layers is summarized to generate the second damage data of the entire soil system.

[0015] In a preferred embodiment, the step of performing finite element calculations based on the second damage data and outputting results for evaluating the bearing effect specifically involves: inputting the second damage data into a finite element solver as a constraint condition for soil constitutive relations and element stiffness degradation; performing full-field numerical calculations on the system including the helical anchor and the soil to obtain the stress distribution, displacement field, and load-displacement response of the system; identifying the plastic development and failure zones of the structure based on the numerical calculation results, and evaluating the working performance of the helical anchor under different load levels; and determining the ultimate bearing capacity and deformation characteristics of the helical anchor based on the load-displacement response and displacement field to complete the final effect evaluation.

[0016] This application also discloses a soil helical anchor bearing effect assessment system based on local damage evolution, comprising: a finite element modeling module for establishing a finite element model of the soil and the helical anchor, setting the boundary conditions of the model, and obtaining finite element data through calculation; a damage mechanics analysis module for introducing local damage variables through constitutive degradation based on the finite element data to simulate shear band development and generate first damage data; an intra-layer constraint module for applying spatial constraints to the soil to optimize the first damage data and obtain corrected second damage data; and an effect assessment module for performing finite element calculations based on the second damage data and outputting results for assessing the bearing effect.

[0017] The technical effects and advantages of the present invention's method for evaluating the bearing capacity of helical anchor foundations are as follows:

[0018] 1. This invention overcomes the limitation of traditional elastoplastic constitutive models in accurately reflecting the significant nonlinear behavior of soil by introducing damage mechanics principles into finite element analysis, constructing element stress-strain degradation functions, and defining local damage variables to characterize the stiffness degradation and failure evolution process of soil. This method can dynamically simulate the development and accumulation of local shear bands in soil at the element scale, achieving a continuous characterization from local damage to overall failure. This makes the finite element calculation results more consistent with the actual mechanical response of soil, significantly improving the accuracy and reliability of the helical anchor effect assessment.

[0019] 2. This invention addresses obstacles in the application of damage mechanics through a layered constraint optimization method. Specifically, it tackles challenges in damage mechanics applications under heterogeneous and layered soil conditions, such as excessive fluctuations in local damage variables and discontinuities in interlayer stress-strain curves. This invention proposes an adaptive correction method based on soil layering and intralayer constraints. By modeling the soil layer by layer and correcting abnormal damage data using intralayer statistical characteristics, and by introducing smooth transition constraints between layers, the continuity and rationality of the degraded stress-strain curve are ensured. This method effectively solves the numerical stability problem of damage mechanics in complex soils, preserving the precision advantages of damage mechanics while avoiding computational distortions caused by soil heterogeneity, thereby improving the overall engineering feasibility and reliability of the results. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the method for evaluating the bearing capacity of helical anchor foundations according to the present invention.

[0021] Figure 2 This is a schematic diagram of the structure of the spiral anchor foundation bearing effect evaluation method system of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1, Figure 1 The present invention provides a method for evaluating the bearing capacity of helical anchor foundations, comprising the following steps:

[0024] S1. Establish a finite element model of the soil and the helical anchor, set the boundary conditions of the model, and obtain the finite element data through calculation.

[0025] In this embodiment, the establishment of the finite element model of the soil and the helical anchor, the setting of boundary conditions, and the acquisition of finite element data are specifically as follows:

[0026] Geological exploration data for the project is obtained, and the soil is divided into three-dimensional finite element meshes to generate a soil model, wherein the meshes are brick elements;

[0027] Obtain the geometric data of the helical anchor, select the helical anchor base model corresponding to the actual helical anchor material, establish a three-dimensional finite element model of the helical anchor, and generate the helical anchor model.

[0028] A soil-helical anchor interface element is set between the soil model and the helical anchor model to obtain the finite element model.

[0029] Boundary conditions are set in the finite element model, and a vertical tension is applied to the upper end of the helical anchor. The boundary conditions include displacement fixed constraints set at the bottom of the soil and elastic constraints set on the side.

[0030] Based on the boundary conditions, the finite element model is solved using a finite element solver to obtain finite element data.

[0031] It should be noted that the geological exploration data includes soil layer thickness and soil properties, including density, elastic modulus, Poisson's ratio, internal friction angle, and cohesion.

[0032] The geometric data of the helical anchor includes the diameter of the shaft, the diameter of the helical blades, the spacing between the helical blades, and the length. The helical anchor model uses steel properties by default, including the elastic modulus, yield strength, and Poisson's ratio.

[0033] The shaft and rotor of the helical anchor need to be unified into a continuous shaft and an additional rotor unit.

[0034] The interface unit defines the friction coefficient, adhesion force, and contact strength to simulate the interaction between the soil and the helical anchor body and helical blades, and allows for local sliding or peeling under load.

[0035] In addition to applying vertical tension, the upper end of the helical anchor can also apply inclined tension to simulate the loads during the construction or service phase. Horizontal loads or combined loads can be superimposed as needed to simulate wind loads or seismic loads.

[0036] The displacement-fixed constraint set at the bottom of the soil is used to simulate the assumption that the soil deep in the soil layer is immovable, so as to prevent the overall rigid body translation and rotation of the model.

[0037] The elastic constraints set on the side of the soil are used to simulate the elastic support effect of infinite soil, so that the finite boundary model can approximate the lateral constraint reaction force of real soil and reduce the influence of boundary effects on the force distribution of the helical anchor.

[0038] The finite element solver can use explicit or implicit solution methods to solve for nodal displacements, element stresses, element strains, and soil-helical anchor interface contact forces. The finite element data provides input for subsequent local damage modeling steps. During the solution process, nonlinear material, contact nonlinear, and geometric nonlinear analysis options are available to ensure that the calculation results reflect the true response of the helical anchor in complex soil environments.

[0039] It should be noted that the soil mass is divided into a three-dimensional finite element mesh using eight-node three-dimensional brick elements; the soil material is represented using the Mohr-Coulomb model. The helical anchor model in this embodiment is established using beam element modeling, where the stresses of the beam elements under bending, tension, and compression are... It is obtained through the following formula:

[0040] (1)

[0041] In the formula, For bending moment, The distance from the cross section to the neutral axis. Let the moment of inertia of the cross section be... It is an axial force. This represents the cross-sectional area.

[0042] An interface element is set between the soil model and the helical anchor model to simulate friction and bonding behavior. Its constitutive relation can be an elastoplastic friction model. The following is a feasible example of its expression:

[0043] (2)

[0044] In the formula, For interfacial shear stress, For adhesive force, The coefficient of friction, The stress is the interface normal stress, and the interface elements are allowed to undergo local sliding or peeling under load.

[0045] In this embodiment, a feasible method for setting displacement fixing constraints at the bottom of the soil is as follows:

[0046] (3)

[0047] In the formula, , , These represent the displacements in the x, y, and z directions, respectively.

[0048] In this embodiment, a feasible method for setting elastic constraints on the side of the soil is as follows:

[0049] (4)

[0050] It is a lateral reaction force. This is lateral displacement. This refers to the soil spring stiffness.

[0051] It should be noted that the finite element solution and output are achieved using mature finite element analysis techniques, such as finite element solvers like ABAQUS, ANSYS, or Plaxis, to numerically solve the nodal displacements, element stresses, element strains, and shear stresses and normal forces of the soil and helical anchors. During the solution process, material nonlinearity, geometric nonlinearity, and contact nonlinearity are considered, and an iterative method is used to solve the nonlinear equations. The following are examples of feasible basic forms:

[0052] (5)

[0053] In the formula This is the tangent stiffness matrix, describing the structural stiffness under the current iteration displacement; For the iterative displacement increment; The applied external load vector includes the load on the upper end of the helical anchor and the boundary constraint reaction force; This is the internal force vector under the current iterative displacement, including soil elasticity, plastic stress, and interface reaction force.

[0054] After the solution is completed, the finite element solver outputs full-field stress, displacement and interface force data as finite element data, which are used for subsequent local damage simulation and effect assessment. This solution method belongs to the existing mature technology.

[0055] S2, based on finite metadata, introduces local damage variables based on the stress-strain degradation function to simulate the development of local shear bands and generate the first damage data.

[0056] In this embodiment, the first damage data includes a first stress-strain curve and a first local damage variable.

[0057] Furthermore, based on finite metadata, local damage variables are introduced using the stress-strain degradation function to simulate the development of local shear bands, specifically:

[0058] Each soil mesh element in the finite element model is used as a computational unit;

[0059] For each computational unit, initialize the local damage variable to zero;

[0060] For each element, obtain the current stress and strain state of the element based on finite metadata;

[0061] Based on the principles of damage mechanics, a stress-strain degradation function for the element is constructed.

[0062] The local damage variables are updated based on the stress-strain degradation function and the current stress and strain state, and the corresponding degradation stress-strain curve is calculated as the first stress-strain curve.

[0063] Based on the updated local damage variables, determine whether each element has entered the local shear band evolution stage and mark the elements that have experienced local damage;

[0064] The first damage data is obtained by summarizing the first stress-strain curve and local failure variables for each soil element.

[0065] It should be noted that treating each soil mesh element in the finite element model as a computational unit means that during the finite element discretization process, the entire soil mass is divided into several three-dimensional elements, such as brick elements. Each element is treated as an independent mechanical unit for stress, strain, and damage analysis. By dividing the soil into discrete computational units, local stress concentration, shear band development, and failure evolution characteristics can be captured at the element level, thereby achieving accurate simulation of the overall soil behavior. This method is a mature technique in finite element analysis and forms the basis for local damage modeling and stress-strain degradation analysis.

[0066] Furthermore, based on the principles of damage mechanics, the element stress-strain degradation function is constructed as follows:

[0067] For each soil element in the finite element model, the local damage variable is set to zero, indicating that the element is not damaged.

[0068] The stress tensor and strain tensor of each element are obtained. Based on the principle of continuum mechanics, the element stress tensor is converted into equivalent stress, and the corresponding equivalent strain is generated by analysis.

[0069] The stiffness of the degraded element is obtained by degrading the elastic modulus of the element with the local damage variable.

[0070] Threshold strain and failure strain are introduced as reference values ​​for the initiation of element damage and complete failure.

[0071] Compare the threshold strain and the equivalent strain. When the equivalent strain is less than or equal to the threshold strain, set the local damage variable to zero.

[0072] When the equivalent strain is greater than the threshold strain and less than or equal to the failure strain, the damage variable is quantified by growing an empirical function in exponential form.

[0073] When the equivalent strain is greater than the failure strain, the local damage variable is set to 1;

[0074] By combining the degraded stiffness and damage variables with the equivalent stress, the element stress-strain degradation function is obtained.

[0075] The following are feasible formulas for equivalent stress and corresponding equivalent strain using von Mises:

[0076] , (6)

[0077] , (7)

[0078] In the formula, Equivalent stress; For equivalent change; Let be the deviatoric stress tensor, representing the stress after removing the volumetric stress; Let i be the element stress tensor components, and j = 1, 2, 3 under three-dimensional stress state. Stress tensor trace ; For Kronecker The function, when i=j, It is 1 if it is not 1, otherwise it is zero; For the partial strain tensor; These are the components of the element strain tensor; For strain tensor trace; where This indicates that the components within a tensor are multiplied one by one and then summed.

[0079] Among them, the stiffness of the degenerate element The formula is:

[0080] (8)

[0081] In the formula, The initial elastic modulus, It is a damage variable that evolves as the equivalent effect increases.

[0082] The expression for the exponential form empirical function that grows the quantified damage variable is as follows:

[0083] (9)

[0084] In the formula, The material sensitivity coefficient is obtained through indoor soil tests.

[0085] The element stress-strain degradation function is: .

[0086] In this embodiment, the local damage variable is used to quantify the degree of damage to the element material. Its value ranges from 0 to 1, where 0 indicates that the element is not damaged and 1 indicates that the element is completely destroyed. The local damage variable is associated with the degradation of the element's elastic modulus during the calculation process. By dynamically updating this variable, the evolution of the element's stiffness with damage can be described.

[0087] Equivalent stress is used to reduce the three-dimensional stress state to a scalar so that it can be combined with local damage variables for degradation analysis. Equivalent stress is calculated using the von Mises equivalent stress form.

[0088] The relationship between the degradation of elastic modulus and degradation stiffness is used to construct the stiffness matrix of the degradation element, so that the stress-strain response of the element weakens as damage evolves.

[0089] It should be noted that the threshold strain is used to define the damage initiation condition of the element, and the failure strain is used to define the complete failure state of the element. When the equivalent strain is less than or equal to the threshold strain, the local damage variable remains zero; when the equivalent strain is greater than the threshold strain, the damage variable increases quantified by an empirical function until the failure strain.

[0090] It should be noted that the element stress-strain degradation function is directly implemented in the finite element solver, enabling the element to reflect the nonlinear response of damage evolution under different stress states.

[0091] Furthermore, the process of updating the local damage variable and calculating the corresponding degradation stress-strain curve as the first stress-strain curve is as follows:

[0092] For each soil element in the finite element model, the degraded equivalent stress and equivalent strain of the element are obtained according to the element stress-strain degradation function;

[0093] When the equivalent strain is less than or equal to the threshold strain, the local damage variable is kept at zero;

[0094] When the equivalent strain is greater than the threshold strain and less than or equal to the failure strain, the local damage variable is updated based on the exponential empirical function.

[0095] When the equivalent strain is greater than the failure strain, the local damage variable is set to 1;

[0096] For each computational unit, obtain the updated local damage variables and the corresponding equivalent stress and equivalent strain;

[0097] By using the stress-strain degradation function, local damage variables are mapped to element stresses to obtain degradation stresses;

[0098] Equivalent strain is paired with degradation stress to form a unit degradation stress-strain curve;

[0099] Traverse all soil elements in the finite element model and obtain the degradation stress-strain curve for each element.

[0100] It should be noted that when the equivalent strain is greater than the threshold strain, updating the local damage variable through the exponential function can simulate the degradation of soil element stiffness as damage develops, avoid non-physical abrupt changes, and ensure that the degradation stress-strain curve is smooth and continuous.

[0101] It should be noted that when the equivalent strain exceeds the failure strain, setting the local damage variable to 1 indicates that the element is completely destroyed. In this state, the stress of the element degenerates to zero or close to zero, thus reflecting the formation of local shear bands in the finite element model.

[0102] It should be noted that the process of mapping local damage variables to element stresses to generate degraded stress-strain curves can be completed through the finite element post-processing module. Equivalent stress-strain values ​​are paired to form curves, which can be used for element-level damage analysis, or to generate layered or full-field statistical stress-strain curves, providing input data for subsequent effect assessment.

[0103] In the above steps, based on the updated local damage variables, it is determined whether each element has entered the local shear band evolution stage, and elements that have experienced local damage are marked. Specifically:

[0104] For each soil element, the corresponding degradation stress-strain curve (first stress-strain curve) is paired with the local failure marker to form the first damage data entry at the element level;

[0105] By traversing all soil elements in the finite element model, the first stress-strain curves and local failure markers of all elements are summarized to obtain the first damage dataset of the overall soil.

[0106] The first damage data can be used for subsequent hierarchical optimization or full-field effect assessment to ensure that unit-level damage information is effectively preserved during the simulation of local shear band formation.

[0107] It should be noted that the local shear zone evolution stage marking is a unit-level damage characterization method. This method can be used to perform targeted processing on soil units in the subsequent S3 layered optimization step, thereby improving the damage prediction accuracy of the overall model.

[0108] It should be noted that existing technologies for soil mechanics analysis typically employ linear elastic or simplified plastic models. These models struggle to accurately characterize the nonlinear behavior of soil under stress, especially when local slippage, plastic flow, and shear band formation occur during the loading or construction phases of the helical anchor. Traditional methods fail to predict local failure and stress concentration, leading to inaccurate mechanical response assessments. To address these issues, this invention utilizes finite metadata, introducing local damage variables based on a stress-strain degradation function, and simulating the development of local shear bands at the element level. This generates initial damage data, including the degraded stress-strain curve and local failure state for each soil element. This method provides reliable input for subsequent layered optimization and full-field effect calculations, considering the significant nonlinear behavior of the soil. This enables the invention to more accurately predict the overall mechanical properties of the soil and helical anchor system under actual engineering conditions.

[0109] S3, the soil is divided into layers, and the second damage data is obtained by optimizing the first damage data based on the intra-layer constraints.

[0110] In this embodiment, the process of stratifying the soil and optimizing the first damage data to obtain the second damage data based on intra-layer constraints specifically involves:

[0111] The soil in the finite element model is divided into several soil layers according to the pre-acquired geological exploration data, with each layer corresponding to a preset thickness and soil type;

[0112] For each layer, the damage parameters in the first damage data are adaptively corrected based on discrete feature analysis.

[0113] In this embodiment, the soil in the finite element model is divided into several soil layers according to pre-acquired geological exploration data. Each layer corresponds to a preset thickness and soil type, specifically:

[0114] Acquiring and organizing geological exploration data;

[0115] For each borehole, based on the soil and rock names and bottom elevations determined in the exploration report, a top-to-bottom stratigraphic sequence is generated within the borehole, forming a one-dimensional initial stratigraphic sequence.

[0116] Within each plane, spatial interpolation is performed on the bottom elevation of the same layer in each borehole to obtain the layer function of that layer;

[0117] Based on the elevation surfaces of the top and bottom of each layer, the entire site is divided into several three-dimensional soil layers along the Z-axis;

[0118] For each finite element soil element, take its geometric center coordinates and determine the layer to which it belongs.

[0119] It should be noted that the following is the expression for a 3D layer volume:

[0120] (10)

[0121] In the formula, For level functions.

[0122] In this embodiment, for elements that traverse a layer, equivalent parameters are weighted according to the proportion of the element volume in adjacent layers. Interlayers, lenses, and weak mud inclusions are treated as separate layers based on the exploration record; when the thickness of an interlayer is less than the minimum grid size, equivalent modeling is performed.

[0123] It should be noted that the equivalent model is incorporated into the adjacent layer, and the parameters are weighted according to the volume fraction.

[0124] It should be noted that the interpolation uses inverse distance weighting, and the following is a feasible calculation example:

[0125] (11)

[0126] (12)

[0127] In the formula, For level functions, Let be the elevation of the bottom of the Kth layer in the i-th borehole. For weighted index, The weights are calculated based on spatial distance and are used to measure the contribution of each known borehole data point to the interpolation point.

[0128] It should be noted that when there are obvious undulations or faults in the site, the borehole can be geologically divided before interpolation, and interpolation should only be performed within the same division to avoid distortion caused by "flattening" across faults.

[0129] It should be noted that the geological exploration data used includes borehole columnar sections, soil layer names, layer bottom elevations, laboratory test parameters, and groundwater levels. Before use, coordinates and elevation benchmarks need to be standardized, and data cleaning should be performed to remove outliers and ensure the reliability of the exploration data.

[0130] It should be noted that, within the site area, spatial interpolation should be performed on the bottom elevation of the corresponding layers to form a continuous layer function. Commonly used methods include inverse distance weighted interpolation and kriging interpolation. The specific method can be selected according to the data density and geological conditions, and cross-validation can be used to evaluate the interpolation accuracy.

[0131] It should be noted that, regarding the three-dimensional soil layers, the site is divided into several three-dimensional soil layers along the Z-axis based on the elevation surfaces of the top and bottom of each layer. For excessively thin layers, they can be merged or equivalentized according to engineering requirements to avoid instability in subsequent mesh generation.

[0132] It should be noted that the mechanical parameters and initial conditions corresponding to each soil layer need to be mapped into finite element units. After mapping, the distribution of element parameters should be checked to ensure consistency with the exploration data, in order to avoid abnormal elements appearing in the model due to interpolation or assignment errors.

[0133] Furthermore, for each layer, the damage parameters in the first damage data are adaptively corrected based on discrete feature analysis, specifically as follows:

[0134] For each soil layer, the first damage data of all units in the layer are extracted, the distribution of damage variables and the dispersion of stress-strain curves of each unit in the layer are analyzed, and the mean standard deviation in the layer is calculated as the statistical characteristics of the layer.

[0135] By comparing the local damage variables of each unit with the intra-layer statistical properties, abnormal units are identified.

[0136] For abnormal units, their damage variables are proportionally regressed to the intra-layer mean to obtain the corrected local damage variables;

[0137] The modified local damage variables are mapped to the element stiffness degradation formula;

[0138] Then, based on the modified stiffness, the degraded stress-strain curve of the unit is calculated to make the curve within the layer smooth and continuous.

[0139] For interface elements of adjacent soil layers, linear interpolation is used to make the degradation curve transition smoothly;

[0140] The optimized damage data of each layer are summarized to form the second damage data of the entire soil system, including the optimized degradation stress-strain curve and local failure variables within the layer.

[0141] The following are feasible expressions for identifying anomalous units:

[0142] (13)

[0143] In the formula, For local damage variables, This is the average value within the layer. Standard deviation The threshold coefficient set by the user, which defaults to 2.

[0144] The following is a feasible expression for proportionally regressing the damage variable to the in-layer mean:

[0145] (14)

[0146] In the formula, The convergence factor controls the correction magnitude; the default value is 0.5, which means shifting the deviation by half towards the mean.

[0147] It should be noted that in numerical calculations, soil elements are prone to uneven distribution of damage variables or excessively large local anomalies due to the influence of mesh generation, material heterogeneity, and boundary conditions. Discrete feature analysis can quantitatively measure the degree of fluctuation in damage data within a layer, thus providing a basis for subsequent corrections.

[0148] It should be noted that constant elements refer to elements whose damage variables deviate significantly from the overall statistical characteristics within the layer. These elements are often not due to actual material failure, but rather caused by factors such as numerical oscillations and local mesh distortion. By comparing them with the layer's mean and standard deviation, numerical anomalies can be effectively eliminated.

[0149] It should be noted that regressing the damage variables of anomalous units to the intra-layer mean can avoid abrupt changes caused by direct forced replacement. Using a proportional correction method can enhance the overall continuity and stability within the layer while maintaining local differences among units.

[0150] It should be noted that there is a direct relationship between the element's damage variable and stiffness degradation. By remapping the corrected damage variable to the element stiffness degradation formula, we can ensure that the mechanical response in subsequent calculations is consistent with the updated damage state, thus avoiding a disconnect between "data correction" and "mechanical calculation".

[0151] It should be noted that at the interface between different soil layers, the material properties often exhibit abrupt changes. However, without proper handling in numerical simulations, this can lead to a "break" in the curve. By performing linear interpolation on the interface elements, the degradation curve can maintain a reasonable transition while preserving the interlayer differences.

[0152] In this embodiment, due to the significant nonlinear behavior of soil, traditional elastoplastic constitutive methods often fail to accurately reflect its gradual failure process. This invention, by introducing damage mechanics principles and establishing local damage variables based on stress-strain degradation functions, effectively solves the problem of describing the macroscopic mechanical response of soil. However, when applying damage mechanics to complex soils, the inherent heterogeneity and stratification effects of soil often lead to new obstacles such as drastic fluctuations in damage parameters between different elements and discontinuous curves between layers, causing the analysis results to deviate from the true soil characteristics. Therefore, this step, by combining geological exploration data to stratify the finite element model and using discrete feature analysis within each layer to adaptively correct the first damage data, not only weakens the numerical anomalies caused by heterogeneity but also ensures the continuity and smoothness of the damage evolution process within and between layers. This makes the obtained second damage data more consistent with the mechanical laws of real layered soil, thereby improving the reliability and engineering applicability of the entire damage analysis method.

[0153] S4, based on the second damage data, calculates the full-field stress, displacement, and bearing capacity using a finite element solver for effect assessment.

[0154] In this embodiment, the step of calculating the full-field stress, displacement, and bearing capacity based on the second damage data using a finite element solver for effect assessment specifically involves:

[0155] The second damage data is input into the finite element solver as a constraint condition for soil constitutive relations and element stiffness degradation;

[0156] The finite element numerical calculation module is called to perform a full-field solution on the spiral anchor and the surrounding soil system, and the full-field stress distribution, displacement field response and bearing capacity curves including the interaction between the soil and the anchoring structure are obtained.

[0157] In the full-field solution, the plastic zone and local failure zone around the anchor body are identified, and the working effect of the helical anchor under different load levels is evaluated.

[0158] The bearing capacity curve is combined with the displacement field results to determine the ultimate bearing capacity and working deformation performance of the helical anchor, forming the final effect evaluation conclusion.

[0159] It should be noted that the second damage data serves only as input parameters for the nonlinear behavior of the soil material. Its purpose is to introduce the constitutive characteristics optimized based on damage mechanics into the finite element model, ensuring that subsequent numerical calculations accurately reflect the strength decay and stiffness degradation process of the soil. Without such damage parameter correction, the finite element analysis results often exhibit excessive dispersion or bias, making them unsuitable for reliable engineering effect assessment.

[0160] It should be noted that, during the full-field solution process, the identification of the plastic zone and local failure zone around the helical anchor is essentially achieved by analyzing stress concentration areas and elements where damage variables reach critical values. This method is based on continuum mechanics and plasticity theory.

[0161] It should be noted that the implementation of the finite element numerical calculation module is existing technology. Currently, mainstream finite element software (such as ABAQUS, ANSYS, Plaxis, etc.) can automatically complete the iterative solution of the full-field stress distribution and displacement field after inputting the material constitutive relation and boundary conditions. Therefore, this invention is not limited to a specific finite element platform, but focuses on improving the input accuracy through damage data correction methods to improve the rationality of the final solution results.

[0162] It should be noted that combining the bearing capacity curve with the displacement field results is a common evaluation method in engineering: the ultimate bearing capacity can be obtained through the load-displacement relationship, while the structural performance under working deformation can be analyzed through the displacement field distribution. The significance of this step lies in transforming the numerical calculation results into evaluation indicators that can be directly applied to the design and construction of helical anchors, thereby achieving a closed loop from theoretical model to engineering practice.

[0163] This embodiment overcomes the limitation of traditional elastoplastic constitutive models in accurately reflecting the significant nonlinear behavior of soil by introducing damage mechanics principles into finite element analysis, constructing element stress-strain degradation functions, and defining local damage variables to characterize the stiffness degradation and failure evolution process of soil. This method can dynamically simulate the development and accumulation of local shear bands in soil at the element scale, achieving a continuous characterization from local damage to overall failure. This makes the finite element calculation results more consistent with the true mechanical response of soil, significantly improving the accuracy and reliability of the helical anchor effect assessment.

[0164] This embodiment addresses obstacles in the application of damage mechanics through a layered constraint optimization method. Addressing the challenges of excessive fluctuations in local damage variables and discontinuities in stress-strain curves between layers, particularly in heterogeneous and layered soils, this invention proposes an adaptive correction method based on soil layering and intra-layer constraints. By modeling the soil layer by layer and correcting abnormal damage data using intra-layer statistical characteristics, while introducing smooth transition constraints between layers, the continuity and rationality of the degraded stress-strain curve are ensured. This method effectively solves the numerical stability problem of damage mechanics in complex soils, preserving the precision advantages of damage mechanics while avoiding computational distortions caused by soil heterogeneity, thereby improving the overall engineering feasibility and reliability of the results.

[0165] Example 2, Figure 2This invention presents a finite element method (FEM)-based system for evaluating the anchorage effect of a helical anchor foundation. The system comprises a finite element modeling module, a damage mechanics analysis module, an in-layer constraint module, and an effect evaluation module. The FEM modeling module establishes a finite element model of the soil and the helical anchor, sets boundary conditions, and obtains finite element data. The damage mechanics analysis module, based on the finite element data and a stress-strain degradation function, introduces local damage variables to simulate the development of local shear bands and generate first damage data, which includes a first stress-strain curve and a first local failure variable. The in-layer constraint module divides the soil into layers and, based on the in-layer constraints, optimizes the first damage data to obtain second damage data. The effect evaluation module calculates the overall stress, displacement, and bearing capacity based on the second damage data using a finite element solver for effect evaluation.

Claims

1. A method for evaluating the bearing capacity of helical anchor foundations, characterized in that, Includes the following steps: A finite element model of the soil and the helical anchor is established, the boundary conditions of the model are set, and the finite element data is obtained through calculation. Each soil mesh element in the finite element model is used as a computational unit; Based on the stress-strain state of each element, its local damage variables are updated through a constitutive relation evolution algorithm; Based on the updated local damage variables, identify and mark the units that have experienced local damage; The damage evolution results of all units are summarized to generate the first damage data; Based on geological exploration data, the soil in the finite element model is divided into multiple soil layers with different soil properties. For each soil layer, obtain the first damage data of all soil elements within it; Based on the first damage data, the intralayer statistical characteristics of the soil layer are analyzed; Based on the statistical characteristics within the soil layer, the damage data of each unit within the soil layer are optimized. The optimization process includes identifying abnormal units that differ significantly from the statistical characteristics within the soil layer, and correcting the damage variables of the abnormal units according to the statistical characteristics. Smooth the transition at the interface between adjacent soil layers; Summarize the optimized damage data of all soil layers to generate the second damage data of the entire soil system; Finite element analysis is performed based on the second damage data, and the output is used to evaluate the load-bearing effect.

2. The method for evaluating the bearing capacity of a helical anchor foundation according to claim 1, characterized in that, The process involves establishing a finite element model of the soil and the helical anchor, setting boundary conditions for the model, and calculating the finite element data, specifically as follows: Based on geological and geometric data, three-dimensional finite element models of the soil and the helical anchor were established respectively. An interaction relationship is established between the soil model and the helical anchor model to simulate the soil-structure contact behavior and form a complete finite element model. Boundary conditions and loads are applied to the finite element model. The boundary conditions include constraints on the bottom and lateral movement of the soil, and the loads are vertical tension applied to the upper end of the helical anchor. Solve the finite element model with applied boundary conditions and loads to obtain finite element data.

3. The method for evaluating the bearing capacity of a helical anchor foundation according to claim 2, characterized in that, The local damage variables are updated based on the stress-strain state of each element using a constitutive relation evolution algorithm. This includes constructing an element stress-strain degradation function based on damage mechanics principles, specifically: Initialize the local damage variables for each soil element; Obtain the current mechanical state of each unit; Based on the current mechanical state and the predetermined damage evolution rule, the local damage variables are calculated and updated in segments; Based on the updated local damage variables, the stress-strain degradation function of the element is generated.

4. The method for evaluating the bearing capacity of a helical anchor foundation according to claim 3, characterized in that, The process of summarizing the damage evolution results of all units to generate the first damage data also includes obtaining the first stress-strain curve, specifically: Obtain the updated local damage variables and their corresponding equivalent stress and equivalent strain for each soil element; Based on the local damage variables and equivalent stress, the local damage variables are mapped to the element stress through the stress-strain degradation function to obtain the degradation stress. Equivalent strain and degradation stress are paired to generate degradation stress-strain curves for each element.

5. The method for evaluating the bearing capacity of a helical anchor foundation according to claim 4, characterized in that, Based on geological exploration data, the soil in the finite element model is divided into multiple soil layers with different soil properties, specifically: Acquire and organize the site's geological exploration data; Based on the rock and soil names and bottom elevations of each borehole in the geological exploration data, a one-dimensional initial stratigraphic sequence is generated for each borehole. Based on a one-dimensional initial sequence, spatial interpolation is performed on the bottom elevation of each soil and rock layer to generate a three-dimensional layer function characterizing the spatial distribution of each soil and rock layer. Using the aforementioned three-dimensional layer function, the entire site is vertically divided into several three-dimensional soil layers. Each soil element in the finite element mesh is mapped to the three-dimensional soil volume to which it belongs.

6. The method for evaluating the bearing capacity of a helical anchor foundation according to claim 5, characterized in that, The finite element calculation based on the second damage data outputs results for evaluating the load-bearing effect, specifically: The second damage data is input into the finite element solver as a constraint condition for soil constitutive relation and element stiffness degradation. Full-field numerical calculations were performed on a system including helical anchors and soil to obtain the stress distribution, displacement field, and load-displacement response of the system. Based on numerical calculation results, the plastic development and failure zones of the structure are identified, and the working performance of the helical anchor under different load levels is evaluated. Based on the load-displacement response and displacement field, the ultimate bearing capacity and deformation characteristics of the helical anchor are determined, and the final effect assessment is completed.

7. A system for evaluating the bearing capacity of a helical anchor foundation as described in any one of claims 1-6, characterized in that, It includes a finite element modeling module, a damage mechanics analysis module, an in-layer constraint module, and an effect assessment module; The finite element modeling module is used to create finite element models of soil and helical anchors, set boundary conditions for the models, and obtain finite element data through calculation. The damage mechanics analysis module is used to simulate shear band development by introducing local damage variables through constitutive degradation based on finite metadata, and to generate the first damage data. The in-layer constraint module is used to apply spatial constraints to the soil to optimize the first damage data and obtain the corrected second damage data. The effect assessment module is used to perform finite element calculations based on the second damage data and output results for evaluating the load-bearing effect.

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